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WO2022185777A1 - Displacement detecting device - Google Patents

Displacement detecting device Download PDF

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Publication number
WO2022185777A1
WO2022185777A1 PCT/JP2022/002402 JP2022002402W WO2022185777A1 WO 2022185777 A1 WO2022185777 A1 WO 2022185777A1 JP 2022002402 W JP2022002402 W JP 2022002402W WO 2022185777 A1 WO2022185777 A1 WO 2022185777A1
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WO
WIPO (PCT)
Prior art keywords
displacement
filter
scale
moving average
processing unit
Prior art date
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PCT/JP2022/002402
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French (fr)
Japanese (ja)
Inventor
哲也 清水
崚平 木戸
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村田機械株式会社
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Publication of WO2022185777A1 publication Critical patent/WO2022185777A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains

Definitions

  • the present invention relates to a displacement detection device that detects displacement of an object to be measured.
  • Patent Literature 1 discloses a position detection device that is a displacement detection device of this type.
  • the position detection device of Patent Document 1 includes a magnetic scale, a pair of magnetic sensors that output two-phase sine waves having a phase difference of 90° corresponding to the pitch of the magnetic scale, and resolution switching means. .
  • a rough position is obtained by performing calculation based on the center value for each pitch calculated from each sensor output peak value for each pitch of the magnetic scale and the comparison result of the sensor output.
  • a precise position can be obtained by inverse trigonometric function calculation using two-phase corrected normalized signals.
  • the position detection device outputs a digital position signal by summing the coarse position and the fine position.
  • the digital position signal is switched to the digital position signal with the set resolution by shifting the data of each bit of the position signal to the lower bits according to the resolution set by the switch, and is output.
  • the resolution is artificially set by a switch or the like. Therefore, if the resolution is set to a low resolution, the detection accuracy will decrease, while if the resolution is set to a high resolution, the followability of detection will be insufficient when the relative speed between the magnetic scale and the magnetic sensor is high. There was room for improvement.
  • the present invention has been made in view of the above circumstances, and its purpose is to provide a displacement detection device capable of achieving both high accuracy and good followability.
  • a displacement detection device having the following configuration. That is, this displacement detection device detects the displacement of the object to be measured in the displacement detection direction.
  • a displacement detection device includes a scale, a sensor head, and a signal processing arithmetic unit. On the scale, magnetically responsive portions and non-magnetically responsive portions are alternately arranged at a predetermined detection pitch in the displacement detection direction.
  • the sensor head has at least four magnetic sensing elements that output respective output signals represented by a sine function, a cosine function, a minus sine function and a minus cosine function. An output signal of the magnetic detection element is input to the signal processing operation device.
  • the signal processing arithmetic device calculates and outputs at least one of a relative displacement of the scale with respect to the sensor head and a rate of change of the relative displacement.
  • the signal processing arithmetic device includes a first differential amplifier, a second differential amplifier, an AD converter, an arithmetic processing section, and a filter processing section.
  • the first differential amplifier outputs a first AC signal obtained by synthesizing the cosine function and the minus cosine function.
  • the second differential amplifier outputs a second AC signal obtained by synthesizing the sine function and the minus sine function.
  • the AD converter converts the first AC signal and the second AC signal into digital values.
  • the arithmetic processing unit arithmetically processes the digital value and outputs the relative displacement of the scale.
  • the filter processor determines whether the speed of the scale relative to the sensor head is high or low. When it is determined that the relative velocity is low, the filter processing section processes the relative displacement output from the arithmetic processing section with a first filter, and converts the displacement after the first filter processing obtained by the relative displacement of the scale to the relative displacement of the scale. output as When it is determined that the relative velocity is high, the filter processing section processes the relative displacement output from the arithmetic processing section with a second filter, and converts the displacement after the second filter processing to the relative displacement of the scale. output as The second filter has a lower order than the first filter.
  • the displacement detection device described above preferably has the following configuration. That is, the filter processing section of the displacement detection device obtains each of the first moving average, the second moving average, and the third moving average.
  • the first moving average corresponds to the first filtered displacement.
  • the second moving average corresponds to the displacement after the second filtering process.
  • the third moving average corresponds to a post-third filtering displacement obtained by processing the relative displacement output from the arithmetic processing unit with a third filter.
  • the third filter has a lower order than the first filter and a higher order than the second filter.
  • the filtering unit uses at least one of a difference between the first moving average and the third moving average and a difference between the first moving average and the second moving average to determine the A determination is made as to whether the relative velocity of the scale is high or low.
  • the displacement detection device described above preferably has the following configuration. That is, the filter processing section obtains each of the first moving average and the second moving average.
  • the first moving average corresponds to the first filtered displacement.
  • the second moving average corresponds to the displacement after the second filtering process.
  • the filter processing section uses a difference between the first moving average and the second moving average to determine whether the speed of the scale relative to the sensor head is high or low.
  • the arithmetic processing unit calculates the displacement of the scale by arctan calculation.
  • FIG. 1 is a block diagram showing the configuration of a displacement detection device according to an embodiment of the present invention
  • FIG. 4 is a block diagram showing an example of moving average
  • FIG. FIG. 10 is a diagram showing experimental results with different numbers of filter stages
  • FIG. 4 is an enlarged view of a portion of the experimental results of FIG. 3
  • FIG. 3 is a block diagram showing processing within the FPGA
  • 7A and 7B are graphs conceptually explaining the selection of the number of stages of the moving average filter according to the speed.
  • FIG. 1 is a block diagram showing the configuration of a displacement detection device 100 according to one embodiment of the present invention.
  • FIG. 2 is a block diagram illustrating an example of moving average.
  • FIG. 3 is a diagram showing experimental results with different numbers of filter stages.
  • FIG. 4 is an enlarged view of part of the experimental results of FIG.
  • FIG. 5 is a block diagram showing processing within the FPGA.
  • FIG. 6 is a graph conceptually explaining the selection of the number of stages of the moving average filter according to the speed.
  • a displacement detection device 100 shown in FIG. 1 is used to detect displacement in a predetermined direction of an object to be measured.
  • the direction in which the displacement of the object to be measured is detected may be called the displacement detection direction.
  • Displacement is a value that indicates how much the current position has changed compared to the reference position (for example, the initial position).
  • the reference position for example, the initial position.
  • the displacement detection device 100 can be used as a position detection device.
  • the displacement detection device 100 mainly includes a scale 1, a magnetic detection head (sensor head) 2, and a detection signal processing device (signal processing operation device) 3.
  • Either the scale 1 or the magnetic detection head 2 is attached to the object to be measured.
  • the scale 1 is attached to a movable member (not shown)
  • the magnetic detection head 2 is attached to a fixed member (not shown) which is the object to be measured.
  • the movable member is linearly movable along a path parallel to the displacement detection direction.
  • the scale 1 may be attached to the fixed member, which is the object to be measured
  • the magnetic detection head 2 may be attached to the movable member.
  • both the scale 1 and the magnetic detection head 2 may be attached to movable members that are displaced relative to each other.
  • the displacement detection device 100 detects the relative displacement of the object to be measured (that is, the scale 1 and the magnetic detection head 2).
  • the scale 1 is used as a scale for detecting the displacement of the measurement object in the longitudinal direction of the scale 1.
  • the scale 1 is elongated in a direction parallel to the movement stroke so as to include the movement stroke of the magnetic detection head 2 accompanying the movement of the movable member.
  • the scale 1 may be formed in the shape of an elongated block, or may be formed in the shape of an elongated rod.
  • the scale 1 includes a non-magnetic response section 11 and a magnetic response section 12.
  • the non-magnetic response section 11 is made of, for example, a metal that does not have significant magnetism, or a material that does not have magnetism, such as plastic.
  • the magnetic response section 12 is made of, for example, metal having ferromagnetism.
  • the non-magnetic responsive portions 11 and the magnetic responsive portions 12 are alternately arranged in the longitudinal direction of the scale 1 .
  • the magnetic response units 12 are arranged in the longitudinal direction of the scale 1 at predetermined detection pitches C0. Since the magnetic response portions 12 are arranged side by side while forming a predetermined interval, there is a non-magnetic portion, which is a portion with no (or relatively weak) magnetism, between two magnetic response portions 12 adjacent to each other. A response part is formed. Therefore, in the magnetic response section 12, presence or absence or strength of the magnetic response appears alternately and repeatedly at each detection pitch C0 in the longitudinal direction of the scale 1.
  • the magnetic detection head 2 is arranged at a predetermined distance from the magnetic response section 12, as shown in FIG.
  • the magnetic detection head 2 can be shaped like a cylinder, and the scale 1 can be inserted into the cylinder hole.
  • the shape of the magnetic detection head 2 is not limited.
  • the magnetic detection head 2 includes a primary coil 21 and a plurality of secondary coils (magnetic detection elements) 22 .
  • Four secondary coils 22 are provided in this embodiment. Note that the primary coil 21 can be omitted.
  • the primary coil 21 is used to generate an alternating magnetic field.
  • an alternating current of an appropriate frequency is passed through the primary coil 21, a magnetic field whose direction and strength periodically change is generated around it.
  • the primary coil 21 is arranged in a portion of the magnetic detection head 2 farther from the scale 1 than the secondary coil 22 is.
  • the four secondary coils 22 are arranged side by side in a direction parallel to the longitudinal direction of the scale 1, as shown in FIG.
  • the secondary coil 22 is arranged in a portion of the magnetic detection head 2 closer to the scale 1 than the primary coil 21 is.
  • An induced current induced by the magnetic field strengthened by the magnetic response section 12 flows through the four secondary coils 22 .
  • the magnetic detection head 2 detects and outputs an electric signal (for example, a voltage signal) based on this induced current.
  • the four secondary coils 22 are arranged side by side at predetermined unit pitches C1 in the displacement detection direction.
  • the unit pitch C1 is determined based on the detected pitch C0 so as to have a predetermined relationship with the detected pitch C0.
  • the unit pitch C1 is set to be the sum of an integral multiple of the detection pitch C0 and 1/4 of the detection pitch C0.
  • C1 (n+1/4) ⁇ C0
  • each of the four secondary coils in order to specify each of the four secondary coils, they are referred to as a first coil 22a, a second coil 22b, a third coil 22c, and a fourth coil 22d in order from the left side shown in FIG. Sometimes.
  • each secondary coil 22 When an alternating current of an appropriate frequency is passed through the primary coil 21, a magnetic field is generated in the primary coil 21, the direction and strength of which change periodically. On the other hand, an induced current is generated in the secondary coil 22 in a direction that hinders the change in the magnetic field of the coil. If a ferromagnetic material exists in the vicinity of the primary coil 21, this ferromagnetic material acts to strengthen the magnetic field generated by the primary coil 21. FIG. This effect increases as the ferromagnetic material approaches the primary coil 21 .
  • the primary coil 21 and the secondary coil 22 approach the magnetic response section 12 as the magnetic detection head 2 relatively moves from one side of the scale 1 to the other side in the longitudinal direction. After coming closest, they move away.
  • the induced current generated in the secondary coil 22 is an alternating current, and the magnitude of the amplitude varies depending on the positional relationship between the secondary coil 22 and the magnetic response section 12 .
  • the secondary coils 22 are spaced apart by the unit pitch C1 so that the positional relationship with the nearest magnetic response section 12 is substantially shifted by 1/4 of the detection pitch C0.
  • the first coil 22a, the second coil 22b, the third coil 22c, and the fourth coil 22d are separated from each other by 1/4 of the detection pitch C0, they are out of phase with each other by 90°. outputs a voltage signal That is, when the voltage signal output by the first coil 22a is expressed as cos+ phase, the second coil 22b outputs a sin+ phase voltage signal, the third coil 22c outputs a cos ⁇ phase voltage signal, and the fourth coil 22c outputs a voltage signal of cos ⁇ phase.
  • the coil 22d outputs a sin-phase voltage signal.
  • the detection signal processing device 3 processes the voltage signals output from the first coil 22a, the second coil 22b, the third coil 22c, and the fourth coil 22d, and calculates the relative displacement of the scale 1 with respect to the magnetic detection head 2. Output.
  • the detection signal processing device for example, as shown in FIG. and a filtering unit 36 .
  • the first differential amplifier 31, the second differential amplifier 32, the first AD converter 33, and the second AD converter 34 are part of the circuits (or electronic parts).
  • the arithmetic processing unit 35 and the filter processing unit 36 are realized by executing a program by an FPGA or the like that constitutes the detection signal processing device 3 .
  • FPGA is an abbreviation for Field Programmable Gate Array.
  • the first differential amplifier 31 is used to amplify the difference between the outputs of the first coil 22a and the third coil 22c.
  • the first differential amplifier 31 amplifies the difference between the voltage signals output from the first coil 22a and the third coil 22c, and outputs it as the first AC signal y1.
  • the second differential amplifier 32 is used to amplify the difference between the outputs of the second coil 22b and the fourth coil 22d.
  • the second differential amplifier 32 amplifies the difference between the voltage signals output from the second coil 22b and the fourth coil 22d and outputs it as a second AC signal y2.
  • the first AD converter 33 and the second AD converter 34 respectively convert the analog signals (the first AC signal y1 and the second AC signal y2) from the first differential amplifier 31 and the second differential amplifier 32 into digital signals.
  • used to convert to The first AD converter 33 and the second AD converter 34 are electrically connected to the arithmetic processing section 35 and output converted digital signals to the arithmetic processing section 35 .
  • the arithmetic processing unit 35 divides the second AC signal y2 by the first AC signal y1. This result corresponds to the value of tan ⁇ . After that, the arithmetic processing unit 35 obtains the arctan value of the calculation result. Thereby, the phase ⁇ representing the displacement of the scale 1 with respect to the magnetic detection head 2 can be obtained. Strictly speaking, ⁇ is the phase, but substantially indicates the relative displacement of the scale 1 with respect to the magnetic detection head 2 . Therefore, ⁇ may be referred to as displacement below.
  • the filter processing unit 36 filters the displacement ⁇ (t) obtained by the arithmetic processing unit 35 .
  • the filter processing unit 36 is configured as, for example, a moving average filter. High frequency components contained in the displacement ⁇ (t) are removed from the displacement ⁇ (t) by filtering. Accordingly, noise and the like can be removed.
  • the filter processing unit 36 can be configured using a shift register, for example, as shown in FIG.
  • This shift register has a configuration in which a plurality of registers are cascaded. Each time a common shift clock is input to each register, data representing the displacement ⁇ (t) is sequentially transferred to the next-stage register.
  • the filter processing unit 36 of this embodiment is composed of 4096 stages of shift registers. Therefore, the filter processing unit 36 can perform moving average processing from 1 to 4096 steps.
  • ⁇ 1(t) ( ⁇ (t)+ ⁇ (t ⁇ 1 ⁇ s)+ ⁇ (t ⁇ 2 ⁇ s)+ . . . + ⁇ (t ⁇ 4095 ⁇ s))/4096
  • this 4096-stage moving average filter process corresponds to the process of the first filter.
  • the value of ⁇ 1(t) may be referred to as a first moving average (displacement after first filtering).
  • this 16-stage moving average filter process corresponds to the process of the second filter.
  • the value of ⁇ 2(t) may be referred to as a second moving average (displacement after second filtering).
  • the SN ratio (SNR: signal-to-noise ratio) of an AD converter is generally represented by the following mathematical model.
  • N is the resolution.
  • FIG. 3 and 4 show the effect of filter processing when the scale 1 moves from position P1 to position P3 and then stops relative to the magnetic detection head 2, and further moves from position P3 to position P2 and stops. It is shown.
  • the graph of FIG. 3 was obtained by experiment, and a part of the graph is enlarged and shown in FIG. In FIG. 4, large-amplitude fluctuation occurs in the sensor output without the filter.
  • Fig. 4 intuitively shows that vibration can be effectively suppressed by filtering. That is, the larger the number of steps of the moving average, the smaller the deviation of the value of the moving average, so that a good value of the SN ratio can be obtained.
  • the number of stages of the moving average filter to be output is selected according to whether the scale 1 is substantially moving or stationary with respect to the magnetic detection head 2. . That is, the displacement detection device 100 outputs moving averages processed with different numbers of filter stages according to the relative moving speed of the scale 1 .
  • each of the first AC signal y1 and the second AC signal y2 is input to the arithmetic processing unit 35 after undergoing processes such as offset correction amount addition and gain correction amount multiplication. be.
  • the calculation processing unit 35 obtains the displacement ⁇ (t) by performing an arctan calculation using the first AC signal y1 and the second AC signal y2.
  • the obtained displacement ⁇ (t) is input to the filter processing section 36 after undergoing processing such as pitch synthesis.
  • the filter processing unit 36 of the present embodiment performs the moving average processing with each of the first filter, the second filter, and the third filter described later, and based on the post-filter processing displacement obtained, the magnetic detection head 2 It is determined whether or not the scale 1 is moving.
  • the third filter is similar to the first and second filters except that the moving average is 2048 stages. It can be said that 2048 stages is an intermediate number of stages between the first filter and the second filter.
  • this 2048-stage moving average filter process corresponds to the process of the third filter.
  • the value of ⁇ 3(t) may be referred to as a third moving average (displacement after third filtering).
  • the stationary state includes a completely stationary state in which the relative speed is zero, and a slow moving state in which the relative speed is slight although the relative speed is not completely stationary.
  • the filter processing unit 36 determines that the scale 1 is stationary with respect to the magnetic detection head 2, the first moving average obtained by performing the moving average processing with the first filter (displacement after first filtering) to select and output.
  • the filter processing unit 36 determines that the scale 1 is moving with respect to the magnetic detection head 2, the second moving average (after the second filter processing) obtained by performing the moving average processing with the second filter displacement) to output.
  • the filter processing unit 36 calculates a first difference that is the difference between the first moving average and the third moving average, and a second difference that is the difference between the first moving average and the second moving average. Compare with a predetermined threshold. The filtering unit 36 determines that the scale 1 is stationary when both the first difference and the second difference are smaller than the threshold. On the other hand, the filter processor 36 determines that the magnetic detection head 2 is moving when at least one of the first difference and the second difference is equal to or greater than the threshold.
  • the second moving average reacts most sensitively among the three moving averages, and the reaction slows down in the order of the third moving average and the first moving average.
  • the first difference and the second difference are moving average differences due to the time lag being different according to the number of moving average stages.
  • the filter processing section 36 substantially determines whether the speed of the scale 1 relative to the magnetic detection head 2 is high or low.
  • the method of determining whether the relative speed of the magnetic detection head 2 is high or low is not limited to the above. For example, determination may be made based on only one of the first difference and the second difference. The determination may be made simply by comparing the difference between the first moving average and the second moving average with a predetermined threshold value. The difference between the current value of an appropriate moving average (for example, the second moving average) and the value a predetermined time ago is obtained, and the difference can be determined by comparing the difference with a predetermined threshold value.
  • an appropriate moving average for example, the second moving average
  • the post-filtering displacement output by the filtering unit 36 is output as position information after undergoing post-processing such as linearity calibration and prediction calculation, as shown in FIG.
  • the displacement detection device 100 of this embodiment is output as the detected value, and when the relative speed of the scale 1 is relatively large, the value obtained by the 16-step moving average process is output as the detected value.
  • FIG. 6 shows that the relative velocity itself is directly compared with the threshold value, this is a conceptual explanation for convenience and differs from actual processing.
  • the displacement detection device 100 of this embodiment can achieve both good followability and accuracy, which are usually in a trade-off relationship.
  • a displacement detection device 100 detects the displacement of the object to be measured in the displacement detection direction.
  • a displacement detection device 100 includes a scale 1 , a magnetic detection head 2 , and a detection signal processing device 3 .
  • On the scale 1 magnetic response sections 12 and non-magnetic response sections 11 are alternately arranged at a predetermined detection pitch in the displacement detection direction.
  • the magnetic detection head 2 has at least four secondary coils 22 that output respective output signals represented by a sine function, a cosine function, a minus sine function and a minus cosine function.
  • the output signal of the secondary coil 22 is input to the detection signal processing device 3, and the detection signal processing device 3 calculates the relative displacement of the scale 1 with respect to the magnetic detection head 2 and outputs it.
  • the detection signal processing device 3 includes a first differential amplifier 31, a second differential amplifier 32, AD converters (first AD converter 33 and second AD converter 34), an arithmetic processing unit 35, and a filter processing unit. 36 and.
  • the first differential amplifier 31 outputs a first AC signal y1 obtained by synthesizing the cosine function and the minus cosine function.
  • the second differential amplifier 32 outputs a second AC signal y2 obtained by synthesizing the sine function and the minus sine function.
  • the AD converter converts the first AC signal y1 and the second AC signal y2 into digital values.
  • the arithmetic processing unit 35 arithmetically processes the digital values and outputs the relative displacement of the scale 1 .
  • the filtering unit 36 determines whether the speed of the scale 1 relative to the magnetic detection head 2 is high or low. When the filter processing unit 36 determines that the relative velocity is low, the displacement after the first filter processing obtained by processing the relative displacement output from the arithmetic processing unit 35 with the first filter is used as the relative displacement of the scale 1. Output. When the filter processing unit 36 determines that the relative velocity is high, the filter processing unit 36 outputs the second filtered displacement obtained by processing the relative displacement output from the arithmetic processing unit 35 with the second filter as the relative displacement of the scale 1. do. The second filter is of lower order than the first filter.
  • the filtering unit 36 obtains each of the first moving average, the second moving average, and the third moving average.
  • the first moving average corresponds to the first filtered displacement.
  • the second moving average corresponds to the second filtered displacement.
  • the third moving average corresponds to the post-third filtering displacement obtained by processing the relative displacement output from the arithmetic processing unit 35 with the third filter.
  • the third filter has a lower order than the first filter and a higher order than the second filter.
  • the filtering unit 36 uses the first difference, which is the difference between the first moving average and the third moving average, and the second difference, which is the difference between the first moving average and the second moving average. A determination is made as to whether the speed of scale 1 relative to scale 2 is high or low.
  • the relative speed of the scale 1 with respect to the magnetic detection head 2 can be accurately determined.
  • the filter processing unit 36 determines whether the speed of the scale 1 relative to the magnetic detection head 2 is high or low based on the difference between the first moving average and the second moving average. can also be configured to
  • the arithmetic processing unit 35 calculates the displacement of the scale 1 by arctan calculation.
  • the scale 1 is not limited to the configuration described above, and may have an appropriate configuration as long as different magnetic properties (strength of magnetism, direction of generated magnetic field, etc.) are repeated.
  • the magnetic response section 12 may be configured by alternately arranging a ferromagnetic material and a weakly magnetic material/non-magnetic material in the longitudinal direction of the scale 1 . By arranging the north and south poles of magnets, repetition of changes in magnetic properties may be realized.
  • the magnetic detection element may be composed of a conductive pattern on a printed circuit board, a Hall element, or the like.
  • the primary coil 21 is arranged on the side closer to the scale 1, and the secondary coil 22 is positioned closer to the scale 1. may be arranged on the far side from the
  • the arithmetic processing unit 35 can also obtain ⁇ by a method other than calculating tan ⁇ . Specifically, the phase of the second AC signal y2 is shifted by 90° by a known shift circuit and added to the first AC signal y1. The signal after the addition can be represented as asin( ⁇ t+ ⁇ ) by the well-known addition theorem of trigonometric functions. The arithmetic processing unit 35 obtains ⁇ by measuring the phase difference between this signal and the reference AC signal asin ⁇ t (specifically, the difference in the timing at which each signal crosses zero). Further, the arithmetic processing unit 35 can also obtain ⁇ by PD (Phase-Digital) conversion.
  • PD Phase-Digital
  • the determination of the relative velocity of the scale 1 in the filter processing unit 36 does not have to be performed in real time. For example, determination may be performed at predetermined time intervals, or may be performed at time intervals that vary according to the relative speed of the scale 1 .
  • the 1st to 16th shift registers are shared by the first filter, the second filter, and the third register.
  • the first to 2048th shift registers are shared by the first and third filters.
  • a shift register may be provided independently for each filter.
  • Filters other than moving average filters may be used as the first and second filters as long as the second filter satisfies the condition that the order is lower than that of the first filter.
  • a filter other than the moving average filter may be used as the third filter as long as the third filter has a lower order than the first filter and a higher order than the second filter.
  • the displacement detection device can also output the rate of change of the relative displacement.
  • the change speed of relative displacement substantially means the relative speed of scale 1 .
  • the change rate of the relative displacement can be easily obtained by calculating the difference between the current relative displacement of the scale 1 and the relative displacement a predetermined time ago.
  • the unmarked processing for example, processing such as offset correction amount addition, gain correction amount multiplication, pitch count generation, pitch synthesis, linearity calibration, prediction calculation, etc.
  • processing for example, processing such as offset correction amount addition, gain correction amount multiplication, pitch count generation, pitch synthesis, linearity calibration, prediction calculation, etc.

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  • General Physics & Mathematics (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Abstract

A displacement detecting device (100) is provided with a scale (1), a magnetic detecting head (2), and a detection signal processing device (3). The detection signal processing device (3) is provided with an arithmetic processing unit (35), and a filter processing unit (36). The arithmetic processing unit (35) performs arithmetic processing of a digital value, and outputs a relative displacement of the scale (1). The filter processing unit (36) performs a determination relating to whether the relative speed of the scale (1) relative to the magnetic detecting head (2) is high or low. If the relative speed is determined to be low, the filter processing unit (36) outputs a first filter-processed displacement obtained by using a first filter to perform processing of the relative displacement output from the arithmetic processing unit (35). If the relative speed is determined to be high, the filter processing unit (36) outputs a second filter-processed displacement obtained by using a second filter to perform processing of the relative displacement output from the arithmetic processing unit (35). The second filter has a lower order than the first filter.

Description

変位検出装置Displacement detector
　本発明は、測定対象物の変位を検出する変位検出装置に関する。 The present invention relates to a displacement detection device that detects displacement of an object to be measured.
　従来から、電磁誘導現象を利用して測定対象物の変位を測定する変位検出装置が知られている。特許文献１は、この種の変位検出装置である位置検出装置を開示する。 Conventionally, there has been known a displacement detection device that measures the displacement of an object to be measured using an electromagnetic induction phenomenon. Patent Literature 1 discloses a position detection device that is a displacement detection device of this type.
　特許文献１の位置検出装置は、磁気スケールと、磁気スケールのピッチに対応して９０゜の位相差をもった２相の正弦波を出力する一対の磁気センサと、分解能切換手段と、を備える。この位置検出装置では、磁気スケールのピッチ毎の各センサ出力ピーク値から演算されたピッチ毎の振央値と、センサ出力の比較結果と、に基づいて演算することにより、粗位置が得られる。また、２相の補正された正規化信号を用いて三角関数逆演算することにより、精位置が得られる。位置検出装置は、粗位置と精位置を合算してデジタルの位置信号を出力する。デジタルの位置信号は、スイッチにより設定された分解能に応じてその位置信号の各ビットのデータを下位ビットへシフトさせることで、設定した分解能のデジタル位置信号に切り換えて出力される。 The position detection device of Patent Document 1 includes a magnetic scale, a pair of magnetic sensors that output two-phase sine waves having a phase difference of 90° corresponding to the pitch of the magnetic scale, and resolution switching means. . In this position detection device, a rough position is obtained by performing calculation based on the center value for each pitch calculated from each sensor output peak value for each pitch of the magnetic scale and the comparison result of the sensor output. In addition, a precise position can be obtained by inverse trigonometric function calculation using two-phase corrected normalized signals. The position detection device outputs a digital position signal by summing the coarse position and the fine position. The digital position signal is switched to the digital position signal with the set resolution by shifting the data of each bit of the position signal to the lower bits according to the resolution set by the switch, and is output.
日本国特許第３３１７４１０号公報Japanese Patent No. 3317410
　上記特許文献１の構成は、スイッチ等により人為的に分解能が設定される。従って、低分解能に設定されている場合は検出精度が低下する一方、高分解能に設定されている場合は、磁気スケールと磁気センサとの相対速度が速い際に検出の追従性が不足するという点で改善の余地があった。 In the configuration of Patent Document 1, the resolution is artificially set by a switch or the like. Therefore, if the resolution is set to a low resolution, the detection accuracy will decrease, while if the resolution is set to a high resolution, the followability of detection will be insufficient when the relative speed between the magnetic scale and the magnetic sensor is high. There was room for improvement.
　本発明は以上の事情に鑑みてされたものであり、その目的は、高精度及び良好な追従性を両立することが可能な変位検出装置を提供することにある。 The present invention has been made in view of the above circumstances, and its purpose is to provide a displacement detection device capable of achieving both high accuracy and good followability.
課題を解決するための手段及び効果Means and Effects for Solving Problems
　本発明の解決しようとする課題は以上の如くであり、次にこの課題を解決するための手段とその効果を説明する。 The problem to be solved by the present invention is as described above. Next, the means for solving this problem and its effect will be explained.
　本発明の観点によれば、以下の構成の変位検出装置が提供される。即ち、この変位検出装置は、変位検出方向における測定対象物の変位を検出する。変位検出装置は、スケールと、センサヘッドと、信号処理演算装置と、を備える。前記スケールには、変位検出方向に所定の検出ピッチで磁気応答部と非磁気応答部とが交互に配列されている。前記センサヘッドは、サイン関数、コサイン関数、マイナスサイン関数及びマイナスコサイン関数で表現される出力信号のそれぞれを出力する少なくとも４つの磁気検出素子を有する。前記信号処理演算装置には、前記磁気検出素子の出力信号が入力される。前記信号処理演算装置は、前記センサヘッドに対する前記スケールの相対変位、及び、前記相対変位の変化速度のうち少なくとも一方を演算して出力する。前記信号処理演算装置は、第１差動増幅器と、第２差動増幅器と、ＡＤ変換器と、演算処理部と、フィルタ処理部と、を備える。前記第１差動増幅器は、前記コサイン関数及び前記マイナスコサイン関数を合成して得られた第１交流信号を出力する。前記第２差動増幅器は、前記サイン関数及び前記マイナスサイン関数を合成して得られた第２交流信号を出力する。前記ＡＤ変換器は、前記第１交流信号及び前記第２交流信号をデジタル値に変換する。前記演算処理部は、前記デジタル値を演算処理して、前記スケールの前記相対変位を出力する。前記フィルタ処理部は、前記センサヘッドに対する前記スケールの相対速度の高低に関して判別を行う。前記相対速度が低いと判別した場合、前記フィルタ処理部は、前記演算処理部から出力された前記相対変位を第１フィルタで処理して得られた第１フィルタ処理後変位を前記スケールの相対変位として出力する。前記相対速度が高いと判別した場合、前記フィルタ処理部は、前記演算処理部から出力された前記相対変位を第２フィルタで処理して得られた第２フィルタ処理後変位を前記スケールの相対変位として出力する。前記第２フィルタは、前記第１フィルタより次数が低い。 According to the aspect of the present invention, a displacement detection device having the following configuration is provided. That is, this displacement detection device detects the displacement of the object to be measured in the displacement detection direction. A displacement detection device includes a scale, a sensor head, and a signal processing arithmetic unit. On the scale, magnetically responsive portions and non-magnetically responsive portions are alternately arranged at a predetermined detection pitch in the displacement detection direction. The sensor head has at least four magnetic sensing elements that output respective output signals represented by a sine function, a cosine function, a minus sine function and a minus cosine function. An output signal of the magnetic detection element is input to the signal processing operation device. The signal processing arithmetic device calculates and outputs at least one of a relative displacement of the scale with respect to the sensor head and a rate of change of the relative displacement. The signal processing arithmetic device includes a first differential amplifier, a second differential amplifier, an AD converter, an arithmetic processing section, and a filter processing section. The first differential amplifier outputs a first AC signal obtained by synthesizing the cosine function and the minus cosine function. The second differential amplifier outputs a second AC signal obtained by synthesizing the sine function and the minus sine function. The AD converter converts the first AC signal and the second AC signal into digital values. The arithmetic processing unit arithmetically processes the digital value and outputs the relative displacement of the scale. The filter processor determines whether the speed of the scale relative to the sensor head is high or low. When it is determined that the relative velocity is low, the filter processing section processes the relative displacement output from the arithmetic processing section with a first filter, and converts the displacement after the first filter processing obtained by the relative displacement of the scale to the relative displacement of the scale. output as When it is determined that the relative velocity is high, the filter processing section processes the relative displacement output from the arithmetic processing section with a second filter, and converts the displacement after the second filter processing to the relative displacement of the scale. output as The second filter has a lower order than the first filter.
　これにより、センサヘッドとスケールとの相対速度に応じて、異なる次数のフィルタで処理して得られた変位を出力することができる。従って、変位検出装置の追従性及び検出精度を両立することができる。 As a result, it is possible to output the displacement obtained by processing with filters of different orders according to the relative speed between the sensor head and the scale. Therefore, both the followability and detection accuracy of the displacement detection device can be achieved.
　前記の変位検出装置において、以下の構成とすることが好ましい。即ち、当該変位検出装置の前記フィルタ処理部は、第１移動平均と、第２移動平均と、第３移動平均と、のそれぞれを求める。前記第１移動平均は、前記第１フィルタ処理後変位に相当する。前記第２移動平均は、前記第２フィルタ処理後変位に相当する。前記第３移動平均は、前記演算処理部から出力された前記相対変位を、第３フィルタで処理して得られた第３フィルタ処理後変位に相当する。前記第３フィルタは、前記第１フィルタより次数が低く、前記第２フィルタより次数が高い。前記フィルタ処理部は、前記第１移動平均と前記第３移動平均との差分、及び、前記第１移動平均と前記第２移動平均との差分のうち少なくとも一方を用いて、前記センサヘッドに対する前記スケールの相対速度の高低に関して判別を行う。 The displacement detection device described above preferably has the following configuration. That is, the filter processing section of the displacement detection device obtains each of the first moving average, the second moving average, and the third moving average. The first moving average corresponds to the first filtered displacement. The second moving average corresponds to the displacement after the second filtering process. The third moving average corresponds to a post-third filtering displacement obtained by processing the relative displacement output from the arithmetic processing unit with a third filter. The third filter has a lower order than the first filter and a higher order than the second filter. The filtering unit uses at least one of a difference between the first moving average and the third moving average and a difference between the first moving average and the second moving average to determine the A determination is made as to whether the relative velocity of the scale is high or low.
　これにより、センサヘッドに対するスケールの相対速度に関する判別をより的確に行うことができる。 This makes it possible to more accurately determine the relative speed of the scale with respect to the sensor head.
　前記の変位検出装置においては、以下の構成とすることが好ましい。即ち、前記フィルタ処理部は、第１移動平均と、第２移動平均と、のそれぞれを求める。前記第１移動平均は、前記第１フィルタ処理後変位に相当する。前記第２移動平均は、前記第２フィルタ処理後変位に相当する。前記フィルタ処理部は、前記第１移動平均と前記第２移動平均との差分を用いて、前記センサヘッドに対する前記スケールの相対速度の高低に関して判別を行う。 The displacement detection device described above preferably has the following configuration. That is, the filter processing section obtains each of the first moving average and the second moving average. The first moving average corresponds to the first filtered displacement. The second moving average corresponds to the displacement after the second filtering process. The filter processing section uses a difference between the first moving average and the second moving average to determine whether the speed of the scale relative to the sensor head is high or low.
　これにより、センサヘッドに対するスケールの相対速度に関する判別を、簡素な処理で行うことができる。 As a result, it is possible to determine the relative speed of the scale with respect to the sensor head with simple processing.
　前記の変位検出装置において、前記演算処理部は、ａｒｃｔａｎ演算により前記スケールの変位を算出することが好ましい。 In the displacement detection device, it is preferable that the arithmetic processing unit calculates the displacement of the scale by arctan calculation.
　これにより、簡単な演算で、変位を得ることができる。 With this, the displacement can be obtained with a simple calculation.
本発明の一実施形態に係る変位検出装置の構成を示すブロック図。1 is a block diagram showing the configuration of a displacement detection device according to an embodiment of the present invention; FIG. 移動平均の例を示すブロック図。4 is a block diagram showing an example of moving average; FIG. 異なるフィルタ段数の実験結果を示す図。FIG. 10 is a diagram showing experimental results with different numbers of filter stages; 図３の実験結果の一部の拡大図。FIG. 4 is an enlarged view of a portion of the experimental results of FIG. 3; ＦＰＧＡ内の処理を示すブロック図。FIG. 3 is a block diagram showing processing within the FPGA; 速度の高低に応じた移動平均フィルタの段数の選択を概念的に説明するグラフ。7A and 7B are graphs conceptually explaining the selection of the number of stages of the moving average filter according to the speed.
　次に、図面を参照して本発明の実施の形態を説明する。図１は、本発明の一実施形態に係る変位検出装置１００の構成を示すブロック図である。図２は、移動平均の例を示すブロック図である。図３は、異なるフィルタ段数の実験結果を示す図である。図４は、図３の実験結果の一部の拡大図である。図５は、ＦＰＧＡ内の処理を示すブロック図である。図６は、速度の高低に応じた移動平均フィルタの段数の選択を概念的に説明するグラフである。 Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a displacement detection device 100 according to one embodiment of the present invention. FIG. 2 is a block diagram illustrating an example of moving average. FIG. 3 is a diagram showing experimental results with different numbers of filter stages. FIG. 4 is an enlarged view of part of the experimental results of FIG. FIG. 5 is a block diagram showing processing within the FPGA. FIG. 6 is a graph conceptually explaining the selection of the number of stages of the moving average filter according to the speed.
　図１に示す変位検出装置１００は、測定対象物の所定の方向での変位を検出するために用いられる。以下の説明では、測定対象物の変位が検出される方向を変位検出方向と呼ぶことがある。 A displacement detection device 100 shown in FIG. 1 is used to detect displacement in a predetermined direction of an object to be measured. In the following description, the direction in which the displacement of the object to be measured is detected may be called the displacement detection direction.
　変位とは、基準位置（例えば、初期位置）と比較して、現在の位置がどれだけ変化しているかを表す値である。基準位置を適宜の方法で定義することにより、測定対象物の位置そのものを変位から計算することもできる。従って、変位検出装置１００は、位置検出装置として使用可能である。 　Displacement is a value that indicates how much the current position has changed compared to the reference position (for example, the initial position). By defining the reference position in an appropriate manner, the position of the measurement object itself can also be calculated from the displacement. Therefore, the displacement detection device 100 can be used as a position detection device.
　変位検出装置１００は、主として、スケール１と、磁気検出ヘッド（センサヘッド）２と、検出信号処理装置（信号処理演算装置）３と、を備える。 The displacement detection device 100 mainly includes a scale 1, a magnetic detection head (sensor head) 2, and a detection signal processing device (signal processing operation device) 3.
　スケール１及び磁気検出ヘッド２のうち何れかが、測定対象物に取り付けられる。例えば、スケール１が図略の可動部材に取り付けられ、磁気検出ヘッド２が、測定対象物である図略の固定部材に取り付けられる。可動部材は、変位検出方向と平行な経路に沿って直線的に移動可能である。 Either the scale 1 or the magnetic detection head 2 is attached to the object to be measured. For example, the scale 1 is attached to a movable member (not shown), and the magnetic detection head 2 is attached to a fixed member (not shown) which is the object to be measured. The movable member is linearly movable along a path parallel to the displacement detection direction.
　また、測定対象物である固定部材にスケール１が取り付けられ、可動部材に磁気検出ヘッド２が取り付けられても良い。更に、スケール１と磁気検出ヘッド２の両方が、互いに相対変位する可動部材にそれぞれ取り付けられても良い。この場合、変位検出装置１００は、測定対象物（即ち、スケール１及び磁気検出ヘッド２）の相対変位を検出する。 Also, the scale 1 may be attached to the fixed member, which is the object to be measured, and the magnetic detection head 2 may be attached to the movable member. Furthermore, both the scale 1 and the magnetic detection head 2 may be attached to movable members that are displaced relative to each other. In this case, the displacement detection device 100 detects the relative displacement of the object to be measured (that is, the scale 1 and the magnetic detection head 2).
　スケール１は、測定対象物が当該スケール１の長手方向における変位を検出するための目盛として用いられる。スケール１は、可動部材の移動に伴う磁気検出ヘッド２の移動ストロークを含むように、当該移動ストロークと平行な方向に細長く形成されている。スケール１は、細長いブロック状に形成されても良いし、細長い棒状に形成されても良い。 The scale 1 is used as a scale for detecting the displacement of the measurement object in the longitudinal direction of the scale 1. The scale 1 is elongated in a direction parallel to the movement stroke so as to include the movement stroke of the magnetic detection head 2 accompanying the movement of the movable member. The scale 1 may be formed in the shape of an elongated block, or may be formed in the shape of an elongated rod.
　スケール１は、非磁気応答部１１と、磁気応答部１２と、を備える。非磁気応答部１１は、例えば、顕著な磁性を有しない金属、又は、磁性を有しないプラスチック等の材料から構成されている。磁気応答部１２は、例えば、強磁性を有する金属等から構成されている。非磁気応答部１１及び磁気応答部１２は、スケール１の長手方向において、交互に配列されている。 The scale 1 includes a non-magnetic response section 11 and a magnetic response section 12. The non-magnetic response section 11 is made of, for example, a metal that does not have significant magnetism, or a material that does not have magnetism, such as plastic. The magnetic response section 12 is made of, for example, metal having ferromagnetism. The non-magnetic responsive portions 11 and the magnetic responsive portions 12 are alternately arranged in the longitudinal direction of the scale 1 .
　磁気応答部１２は、予め定められた検出ピッチＣ０毎に、スケール１の長手方向に並べて設けられている。磁気応答部１２は、所定の間隔を形成しながら並べて配置されているので、互いに隣接する２つの磁気応答部１２の間には、磁性がない（又は、相対的に弱い）部分である非磁気応答部が形成される。従って、磁気応答部１２においては、スケール１の長手方向で検出ピッチＣ０毎に、磁気応答性の有無又は強弱が交互に繰返し現れる。 The magnetic response units 12 are arranged in the longitudinal direction of the scale 1 at predetermined detection pitches C0. Since the magnetic response portions 12 are arranged side by side while forming a predetermined interval, there is a non-magnetic portion, which is a portion with no (or relatively weak) magnetism, between two magnetic response portions 12 adjacent to each other. A response part is formed. Therefore, in the magnetic response section 12, presence or absence or strength of the magnetic response appears alternately and repeatedly at each detection pitch C0 in the longitudinal direction of the scale 1. FIG.
　磁気検出ヘッド２は、図１に示すように、磁気応答部１２と所定の間隔をあけて配置されている。スケール１が細長い棒状に形成されている場合、磁気検出ヘッド２は例えば筒状に形成され、その筒孔にスケール１が差し込まれる構成とすることができる。ただし、磁気検出ヘッド２の形状は限定されない。磁気検出ヘッド２は、１次コイル２１と、複数の２次コイル（磁気検出素子）２２と、を備える。２次コイル２２は、本実施形態においては４つ設けられている。なお、１次コイル２１を省略することができる。 The magnetic detection head 2 is arranged at a predetermined distance from the magnetic response section 12, as shown in FIG. When the scale 1 is shaped like an elongated bar, the magnetic detection head 2 can be shaped like a cylinder, and the scale 1 can be inserted into the cylinder hole. However, the shape of the magnetic detection head 2 is not limited. The magnetic detection head 2 includes a primary coil 21 and a plurality of secondary coils (magnetic detection elements) 22 . Four secondary coils 22 are provided in this embodiment. Note that the primary coil 21 can be omitted.
　１次コイル２１は、交流磁界を発生するために用いられる。１次コイル２１に適宜の周波数の交流電流を流すと、その周囲に、向き及び強さが周期的に変化する磁界が発生する。図１に示すように、１次コイル２１は、磁気検出ヘッド２において、２次コイル２２よりもスケール１から遠い側の部分に配置されている。 The primary coil 21 is used to generate an alternating magnetic field. When an alternating current of an appropriate frequency is passed through the primary coil 21, a magnetic field whose direction and strength periodically change is generated around it. As shown in FIG. 1, the primary coil 21 is arranged in a portion of the magnetic detection head 2 farther from the scale 1 than the secondary coil 22 is.
　４つの２次コイル２２は、図１に示すように、スケール１の長手方向と平行な方向に並べて配置されている。２次コイル２２は、磁気検出ヘッド２において、１次コイル２１よりもスケール１に近い側の部分に配置されている。４つの２次コイル２２には、磁気応答部１２で強められた磁界によって誘起された誘導電流が流れる。磁気検出ヘッド２は、この誘導電流に基づく電気信号（例えば電圧信号）を検出して出力する。 The four secondary coils 22 are arranged side by side in a direction parallel to the longitudinal direction of the scale 1, as shown in FIG. The secondary coil 22 is arranged in a portion of the magnetic detection head 2 closer to the scale 1 than the primary coil 21 is. An induced current induced by the magnetic field strengthened by the magnetic response section 12 flows through the four secondary coils 22 . The magnetic detection head 2 detects and outputs an electric signal (for example, a voltage signal) based on this induced current.
　図１に示すように、当該４つの２次コイル２２は、変位検出方向において予め定められた単位ピッチＣ１毎に並べて配置されている。当該単位ピッチＣ１は、前述の検出ピッチＣ０との間で所定の関係を有するように、検出ピッチＣ０に基づいて定められている。具体的に説明すると、以下の式で示すように、単位ピッチＣ１は、検出ピッチＣ０の整数倍と、検出ピッチＣ０の１／４と、の和となるように設定される。
　Ｃ１＝（ｎ＋１／４）・Ｃ０
　ただし、ｎは整数である。本実施形態においては、ｎ＝０であるが、これに限定されない。 As shown in FIG. 1, the four secondary coils 22 are arranged side by side at predetermined unit pitches C1 in the displacement detection direction. The unit pitch C1 is determined based on the detected pitch C0 so as to have a predetermined relationship with the detected pitch C0. Specifically, as shown in the following formula, the unit pitch C1 is set to be the sum of an integral multiple of the detection pitch C0 and 1/4 of the detection pitch C0.
C1=(n+1/4)·C0
However, n is an integer. Although n=0 in this embodiment, the present invention is not limited to this.
　以下の説明においては、当該４つの２次コイルのそれぞれを特定するために、図１に示す左側から順に、第１コイル２２ａ、第２コイル２２ｂ、第３コイル２２ｃ、及び第４コイル２２ｄと呼ぶことがある。 In the following description, in order to specify each of the four secondary coils, they are referred to as a first coil 22a, a second coil 22b, a third coil 22c, and a fourth coil 22d in order from the left side shown in FIG. Sometimes.
　ここで、各２次コイル２２で出力する信号（例えば、電圧信号）について、簡単に説明する。１次コイル２１に適宜の周波数の交流電流を流すと、１次コイル２１には、向き及び強さが周期的に変化する磁界が発生する。一方、２次コイル２２には、コイルの磁界の変化を妨げる向きの誘導電流が発生する。１次コイル２１の近傍に強磁性体が存在すると、この強磁性体は、１次コイル２１が発生させる磁界を強めるように作用する。この作用は、強磁性体が１次コイル２１に近づく程大きくなる。 Here, the signal (for example, voltage signal) output by each secondary coil 22 will be briefly described. When an alternating current of an appropriate frequency is passed through the primary coil 21, a magnetic field is generated in the primary coil 21, the direction and strength of which change periodically. On the other hand, an induced current is generated in the secondary coil 22 in a direction that hinders the change in the magnetic field of the coil. If a ferromagnetic material exists in the vicinity of the primary coil 21, this ferromagnetic material acts to strengthen the magnetic field generated by the primary coil 21. FIG. This effect increases as the ferromagnetic material approaches the primary coil 21 .
　磁気応答部１２に着目すると、磁気検出ヘッド２がスケール１の長手方向一側から他側へ相対移動するにつれて、１次コイル２１及び２次コイル２２が当該磁気応答部１２に近づいていくが、最も近づいた後は離れていく。２次コイル２２に発生する誘導電流は交流電流であるが、その振幅の大きさは、当該２次コイル２２と、磁気応答部１２と、の位置関係に応じて異なる。 Focusing on the magnetic response section 12, the primary coil 21 and the secondary coil 22 approach the magnetic response section 12 as the magnetic detection head 2 relatively moves from one side of the scale 1 to the other side in the longitudinal direction. After coming closest, they move away. The induced current generated in the secondary coil 22 is an alternating current, and the magnitude of the amplitude varies depending on the positional relationship between the secondary coil 22 and the magnetic response section 12 .
　磁気応答部１２は実際には検出ピッチＣ０ごとに並べて配置されるので、振幅の大きさの変化は、検出ピッチＣ０ごとの繰り返しになる。即ち、横軸に磁気検出ヘッド２の位置をとり、縦軸に振幅の大きさをとると、振幅と位置との関係は、検出ピッチＣ０を周期とする周期曲線（具体的には、正弦曲線ｙ＝ｓｉｎθ）となる。このθを求めることができれば、繰返し単位である検出ピッチＣ０の中でスケール１が磁気検出ヘッド２に対してどの位置にあるかを取得することができる。 Since the magnetic response units 12 are actually arranged side by side for each detection pitch C0, the change in amplitude is repeated for each detection pitch C0. That is, if the horizontal axis represents the position of the magnetic detection head 2 and the vertical axis represents the magnitude of the amplitude, the relationship between the amplitude and the position is a periodic curve (specifically, a sine curve y=sin θ). If this θ can be obtained, it is possible to obtain the position of the scale 1 with respect to the magnetic detection head 2 within the detection pitch C0, which is the repeating unit.
　しかし、正弦曲線ｙ＝ｓｉｎθの１周期分を考えると、特別な場合を除いてｙに対応するθの値は２つ考えられ、ただ１つに定まらない。そこで、本実施形態では、２次コイル２２を、最も近い磁気応答部１２との位置関係が検出ピッチＣ０の１／４ずつ実質的にズレるように、上述の単位ピッチＣ１で定められる間隔をあけて４つ配置している。 However, considering one period of the sine curve y = sin θ, there are two possible values of θ corresponding to y except for special cases, and only one is not determined. Therefore, in this embodiment, the secondary coils 22 are spaced apart by the unit pitch C1 so that the positional relationship with the nearest magnetic response section 12 is substantially shifted by 1/4 of the detection pitch C0. There are four
　図１に示すように、第１コイル２２ａ、第２コイル２２ｂ、第３コイル２２ｃ、第４コイル２２ｄのそれぞれは、互いに検出ピッチＣ０の１／４だけ離れているので、互いに位相が９０°ズレている電圧信号を出力する。即ち、第１コイル２２ａが出力する電圧信号をｃｏｓ＋相と表現した場合、第２コイル２２ｂはｓｉｎ＋相の電圧信号を出力し、第３コイル２２ｃはｃｏｓ－相の電圧信号を出力し、第４コイル２２ｄはｓｉｎ－相の電圧信号を出力することとなる。 As shown in FIG. 1, since the first coil 22a, the second coil 22b, the third coil 22c, and the fourth coil 22d are separated from each other by 1/4 of the detection pitch C0, they are out of phase with each other by 90°. outputs a voltage signal That is, when the voltage signal output by the first coil 22a is expressed as cos+ phase, the second coil 22b outputs a sin+ phase voltage signal, the third coil 22c outputs a cos− phase voltage signal, and the fourth coil 22c outputs a voltage signal of cos− phase. The coil 22d outputs a sin-phase voltage signal.
　検出信号処理装置３は、第１コイル２２ａ、第２コイル２２ｂ、第３コイル２２ｃ、第４コイル２２ｄから出力された電圧信号を処理し、磁気検出ヘッド２に対するスケール１の相対変位を算出して出力する。 The detection signal processing device 3 processes the voltage signals output from the first coil 22a, the second coil 22b, the third coil 22c, and the fourth coil 22d, and calculates the relative displacement of the scale 1 with respect to the magnetic detection head 2. Output.
　検出信号処理装置３は、例えば、図１に示すように、第１差動増幅器３１と、第２差動増幅器３２と、第１ＡＤ変換器３３と、第２ＡＤ変換器３４と、演算処理部３５と、フィルタ処理部３６と、を備える。 The detection signal processing device 3, for example, as shown in FIG. and a filtering unit 36 .
　本実施形態において、第１差動増幅器３１、第２差動増幅器３２、第１ＡＤ変換器３３、第２ＡＤ変換器３４は、検出信号処理装置３が備えるアナログ回路を構成する一部の回路（又は電子部品）から構成される。演算処理部３５及びフィルタ処理部３６は、検出信号処理装置３を構成するＦＰＧＡ等がプログラムを実行することにより実現されている。ＦＰＧＡは、Ｆｉｅｌｄ　Ｐｒｏｇｒａｍｍａｂｌｅ　Ｇａｔｅ　Ａｒｒａｙの略称である。 In the present embodiment, the first differential amplifier 31, the second differential amplifier 32, the first AD converter 33, and the second AD converter 34 are part of the circuits (or electronic parts). The arithmetic processing unit 35 and the filter processing unit 36 are realized by executing a program by an FPGA or the like that constitutes the detection signal processing device 3 . FPGA is an abbreviation for Field Programmable Gate Array.
　第１差動増幅器３１は、第１コイル２２ａ及び第３コイル２２ｃの出力の差分を増幅するために用いられる。第１差動増幅器３１は、第１コイル２２ａ及び第３コイル２２ｃから出力された電圧信号の差分を増幅して、第１交流信号ｙ１として出力する。 The first differential amplifier 31 is used to amplify the difference between the outputs of the first coil 22a and the third coil 22c. The first differential amplifier 31 amplifies the difference between the voltage signals output from the first coil 22a and the third coil 22c, and outputs it as the first AC signal y1.
　磁気検出ヘッド２に対するスケール１の変位を表す位相をθとしたとき、上記第１交流信号ｙ１は、以下の式で表すことができる。
　ｙ１＝ａｃｏｓθ・ｓｉｎωｔ Assuming that the phase representing the displacement of the scale 1 with respect to the magnetic detection head 2 is θ, the first AC signal y1 can be expressed by the following equation.
y1=a cos θ·sin ωt
　第２差動増幅器３２は、第２コイル２２ｂ及び第４コイル２２ｄの出力の差分を増幅するために用いられる。第２差動増幅器３２は、第２コイル２２ｂ及び第４コイル２２ｄから出力された電圧信号の差分を増幅して、第２交流信号ｙ２として出力する。 The second differential amplifier 32 is used to amplify the difference between the outputs of the second coil 22b and the fourth coil 22d. The second differential amplifier 32 amplifies the difference between the voltage signals output from the second coil 22b and the fourth coil 22d and outputs it as a second AC signal y2.
　磁気検出ヘッド２に対するスケール１の変位を表す位相をθとしたとき、上記第２交流信号ｙ２は、以下の式で表すことができる。
　ｙ２＝ａｓｉｎθ・ｓｉｎωｔ Assuming that the phase representing the displacement of the scale 1 with respect to the magnetic detection head 2 is .theta., the second AC signal y2 can be expressed by the following equation.
y2=asinθ·sinωt
　第１ＡＤ変換器３３及び第２ＡＤ変換器３４はそれぞれ、第１差動増幅器３１及び第２差動増幅器３２からのアナログ信号（第１交流信号ｙ１及び第２交流信号ｙ２）のそれぞれを、デジタル信号に変換するために用いられる。第１ＡＤ変換器３３及び第２ＡＤ変換器３４は、演算処理部３５に電気的に接続されており、変換したデジタル信号を演算処理部３５に出力する。 The first AD converter 33 and the second AD converter 34 respectively convert the analog signals (the first AC signal y1 and the second AC signal y2) from the first differential amplifier 31 and the second differential amplifier 32 into digital signals. used to convert to The first AD converter 33 and the second AD converter 34 are electrically connected to the arithmetic processing section 35 and output converted digital signals to the arithmetic processing section 35 .
　演算処理部３５は、第２交流信号ｙ２を第１交流信号ｙ１で除算する。この結果は、ｔａｎθの値に相当する。その後、演算処理部３５は、計算結果のａｒｃｔａｎの値を求める。これにより、磁気検出ヘッド２に対するスケール１の変位を表す位相θを得ることができる。θは厳密には位相であるが、実質的には、磁気検出ヘッド２に対するスケール１の相対変位を示している。従って、以下ではθを変位と呼ぶことがある。 The arithmetic processing unit 35 divides the second AC signal y2 by the first AC signal y1. This result corresponds to the value of tan θ. After that, the arithmetic processing unit 35 obtains the arctan value of the calculation result. Thereby, the phase θ representing the displacement of the scale 1 with respect to the magnetic detection head 2 can be obtained. Strictly speaking, θ is the phase, but substantially indicates the relative displacement of the scale 1 with respect to the magnetic detection head 2 . Therefore, θ may be referred to as displacement below.
　フィルタ処理部３６は、演算処理部３５で求められた変位θ（ｔ）に対してフィルタ処理を行う。フィルタ処理部３６は、例えば移動平均フィルタとして構成される。変位θ（ｔ）に含まれる高周波成分が、フィルタ処理によって、当該変位θ（ｔ）から除かれる。これにより、ノイズ等を除去することができる。 The filter processing unit 36 filters the displacement θ(t) obtained by the arithmetic processing unit 35 . The filter processing unit 36 is configured as, for example, a moving average filter. High frequency components contained in the displacement θ(t) are removed from the displacement θ(t) by filtering. Accordingly, noise and the like can be removed.
　フィルタ処理部３６は、例えば、図２に示すように、シフトレジスタを用いて構成することができる。このシフトレジスタは、複数のレジスタをカスケード接続する構成を有する。各レジスタに共通のシフトクロックが入力されるたびに、変位θ（ｔ）を示すデータが次段のレジスタに順次転送されていく。 The filter processing unit 36 can be configured using a shift register, for example, as shown in FIG. This shift register has a configuration in which a plurality of registers are cascaded. Each time a common shift clock is input to each register, data representing the displacement θ(t) is sequentially transferred to the next-stage register.
　図２に示すように、本実施形態のフィルタ処理部３６は、４０９６段分のシフトレジスタによって構成されている。従って、フィルタ処理部３６は、１段から４０９６段までの移動平均処理を行うことができる。 As shown in FIG. 2, the filter processing unit 36 of this embodiment is composed of 4096 stages of shift registers. Therefore, the filter processing unit 36 can perform moving average processing from 1 to 4096 steps.
　４０９６段の移動平均フィルタ処理後の値は、以下の式で表すことができる。ただし、ｓは、シフトレジスタのシフト周期である。
　θ１（ｔ）＝（θ（ｔ）＋θ（ｔ－１・ｓ）＋θ（ｔ－２・ｓ）＋・・・＋θ（ｔ－４０９５・ｓ））／４０９６
　本実施形態では、この４０９６段の移動平均フィルタ処理が、第１フィルタの処理に相当する。以下、θ１（ｔ）の値を、第１移動平均（第１フィルタ処理後変位）と呼ぶことがある。 The value after 4096 stages of moving average filtering can be expressed by the following equation. However, s is the shift period of the shift register.
θ1(t)=(θ(t)+θ(t−1·s)+θ(t−2·s)+ . . . +θ(t−4095·s))/4096
In the present embodiment, this 4096-stage moving average filter process corresponds to the process of the first filter. Hereinafter, the value of θ1(t) may be referred to as a first moving average (displacement after first filtering).
　１６段の移動平均フィルタ処理後の値は、以下の式で表すことができる。
　θ２（ｔ）＝（θ（ｔ）＋θ（ｔ－１・ｓ）＋θ（ｔ－２・ｓ）＋・・・＋θ（ｔ－１５・ｓ））／１６
　本実施形態では、この１６段の移動平均フィルタ処理が、第２フィルタの処理に相当する。以下、θ２（ｔ）の値を、第２移動平均（第２フィルタ処理後変位）と呼ぶことがある。 The value after 16-stage moving average filtering can be expressed by the following equation.
θ2(t)=(θ(t)+θ(t−1·s)+θ(t−2·s)+ . . . +θ(t−15·s))/16
In the present embodiment, this 16-stage moving average filter process corresponds to the process of the second filter. Hereinafter, the value of θ2(t) may be referred to as a second moving average (displacement after second filtering).
　知られているように、ＡＤ変換器のＳＮ比（ＳＮＲ：ｓｉｇｎａｌ－ｔｏ－ｎｏｉｓｅ　ｒａｔｉｏ）は、一般的に下記の数式モデルで表される。ただし、Ｎは分解能である。
　ＳＮＲ＝６．０２・Ｎ＋１．７６［ｄＢ］
　従って、理論的にいえば、４のｎ乗の移動平均処理を行うことで、分解能がｎビット分改善される。例えば、１６段（＝４の２乗）の移動平均では、フィルタ無しに比べて、有効分解能が２ビット分向上する。４０９６段（＝４の６乗）の移動平均では、フィルタ無しの値に比べて、有効分解能が６ビット分向上する。 As is known, the SN ratio (SNR: signal-to-noise ratio) of an AD converter is generally represented by the following mathematical model. where N is the resolution.
SNR = 6.02 N + 1.76 [dB]
Therefore, theoretically speaking, the resolution is improved by n bits by performing the moving average processing of 4 to the nth power. For example, with a moving average of 16 stages (=4 squared), the effective resolution is improved by 2 bits compared to no filter. With a moving average of 4096 steps (=4 to the 6th power), the effective resolution is improved by 6 bits compared to the unfiltered value.
　図３及び図４には、スケール１が磁気検出ヘッド２に対して、位置Ｐ１から位置Ｐ３へ移動して静止し、更に位置Ｐ３から位置Ｐ２へ移動して静止した場合の、フィルタ処理の効果が示されている。図３のグラフは実験により得られたものであり、グラフの一部は拡大して図４に示されている。図４において、フィルタ無しでのセンサ出力には振幅の大きな振れが生じている。 3 and 4 show the effect of filter processing when the scale 1 moves from position P1 to position P3 and then stops relative to the magnetic detection head 2, and further moves from position P3 to position P2 and stops. It is shown. The graph of FIG. 3 was obtained by experiment, and a part of the graph is enlarged and shown in FIG. In FIG. 4, large-amplitude fluctuation occurs in the sensor output without the filter.
　図４には、フィルタ処理により振れを効果的に抑制できることが直感的に示されている。即ち、移動平均の段数が大きければ大きいほど、移動平均の値の振れが小さくなるので、ＳＮ比の良い値を得ることができる。 Fig. 4 intuitively shows that vibration can be effectively suppressed by filtering. That is, the larger the number of steps of the moving average, the smaller the deviation of the value of the moving average, so that a good value of the SN ratio can be obtained.
　一方、図３の下側に示すように、スケール１が移動するときには、移動平均の段数が大きければ大きいほど、得られた移動平均の時間遅れが大きくなる。例えば、シフト周期（サンプリング周期）ｓを１６μｓとする場合、移動平均１６段の処理を行って得られた第２移動平均θ２（ｔ）には、１２８μｓの時間遅れが発生する。移動平均４０９６段の処理を行って得られた第１移動平均θ１（ｔ）には、３２．７６８ｍｓの時間遅れが発生する。 On the other hand, as shown in the lower part of FIG. 3, when the scale 1 moves, the larger the number of stages of the moving average, the greater the time lag of the obtained moving average. For example, when the shift cycle (sampling cycle) s is 16 μs, a time delay of 128 μs occurs in the second moving average θ2(t) obtained by performing 16 stages of moving average processing. A time delay of 32.768 ms occurs in the first moving average θ1(t) obtained by performing 4096 stages of moving average processing.
　以上に示すように、フィルタの段数が大きければ大きいほど、得られた移動平均（フィルタ処理後変位）の精度が良くなるが、時間遅れが大きく発生してしまい、追従性が低下していく。時間遅れによる位置検出誤差は、スケール１が高速で変位する場合に特に大きくなる。 As shown above, the larger the number of stages of the filter, the better the accuracy of the obtained moving average (displacement after filtering), but the larger the time delay, the lower the followability. A position detection error due to a time delay becomes particularly large when the scale 1 is displaced at high speed.
　この点に関して、本実施形態の変位検出装置１００においては、磁気検出ヘッド２に対してスケール１が実質的に移動しているか静止しているかに応じて、出力する移動平均フィルタの段数を選択する。即ち、変位検出装置１００は、スケール１の相対移動速度に応じて、異なるフィルタ段数で処理した移動平均を出力する。 Regarding this point, in the displacement detection device 100 of the present embodiment, the number of stages of the moving average filter to be output is selected according to whether the scale 1 is substantially moving or stationary with respect to the magnetic detection head 2. . That is, the displacement detection device 100 outputs moving averages processed with different numbers of filter stages according to the relative moving speed of the scale 1 .
　具体的には、図５に示すように、第１交流信号ｙ１及び第２交流信号ｙ２のそれぞれが、オフセット補正量加算、ゲイン補正量乗算等の処理を経た後、演算処理部３５に入力される。演算処理部３５では、第１交流信号ｙ１及び第２交流信号ｙ２を用いてａｒｃｔａｎ演算を行うことにより、変位θ（ｔ）を取得する。得られた変位θ（ｔ）は、ピッチ合成等の処理を経た後、フィルタ処理部３６に入力される。 Specifically, as shown in FIG. 5, each of the first AC signal y1 and the second AC signal y2 is input to the arithmetic processing unit 35 after undergoing processes such as offset correction amount addition and gain correction amount multiplication. be. The calculation processing unit 35 obtains the displacement θ(t) by performing an arctan calculation using the first AC signal y1 and the second AC signal y2. The obtained displacement θ(t) is input to the filter processing section 36 after undergoing processing such as pitch synthesis.
　本実施形態のフィルタ処理部３６は、上記第１フィルタ、第２フィルタ、及び後述の第３フィルタのそれぞれで移動平均処理を行って得られたフィルタ処理後変位に基づいて、磁気検出ヘッド２に対してスケール１が移動しているか否かを判定する。 The filter processing unit 36 of the present embodiment performs the moving average processing with each of the first filter, the second filter, and the third filter described later, and based on the post-filter processing displacement obtained, the magnetic detection head 2 It is determined whether or not the scale 1 is moving.
　第３フィルタは、移動平均が２０４８段である以外は、第１フィルタ及び第２フィルタと同様である。２０４８段は、第１フィルタと第２フィルタの中間の段数であるということができる。２０４８段の移動平均フィルタ処理後の値は、以下の式で表すことができる。
　θ３（ｔ）＝（θ（ｔ）＋θ（ｔ－１・ｓ）＋θ（ｔ－２・ｓ）＋・・・＋θ（ｔ－２０４７・ｓ））／２０４８
　本実施形態では、この２０４８段の移動平均フィルタ処理が、第３フィルタの処理に相当する。以下、θ３（ｔ）の値を、第３移動平均（第３フィルタ処理後変位）と呼ぶことがある。 The third filter is similar to the first and second filters except that the moving average is 2048 stages. It can be said that 2048 stages is an intermediate number of stages between the first filter and the second filter. The value after 2048 stages of moving average filtering can be expressed by the following equation.
θ3(t)=(θ(t)+θ(t−1·s)+θ(t−2·s)+ . . . +θ(t−2047·s))/2048
In the present embodiment, this 2048-stage moving average filter process corresponds to the process of the third filter. Hereinafter, the value of θ3(t) may be referred to as a third moving average (displacement after third filtering).
　本実施形態において、磁気検出ヘッド２に対してスケール１が移動しているか静止しているかの判定は、スケール１の相対速度が比較的高いか低いかを、フィルタ処理部３６が適宜の計算により判別した結果に基づく。従って、静止している場合とは、相対速度がゼロである完全静止状態と、完全静止状態ではないものの相対速度が僅かである微速移動中の状態と、を含む。 In this embodiment, whether the scale 1 is moving or stationary with respect to the magnetic detection head 2 is determined by the filter processing unit 36 based on appropriate calculations based on whether the relative speed of the scale 1 is relatively high or low. Based on determined results. Therefore, the stationary state includes a completely stationary state in which the relative speed is zero, and a slow moving state in which the relative speed is slight although the relative speed is not completely stationary.
　フィルタ処理部３６は、磁気検出ヘッド２に対してスケール１が静止していると判定した場合、第１フィルタで移動平均処理を行って得られた第１移動平均（第１フィルタ処理後変位）を選択して出力する。 When the filter processing unit 36 determines that the scale 1 is stationary with respect to the magnetic detection head 2, the first moving average obtained by performing the moving average processing with the first filter (displacement after first filtering) to select and output.
　一方、フィルタ処理部３６は、磁気検出ヘッド２に対してスケール１が移動していると判定した場合、第２フィルタで移動平均処理を行って得られた第２移動平均（第２フィルタ処理後変位）を選択して出力する。 On the other hand, when the filter processing unit 36 determines that the scale 1 is moving with respect to the magnetic detection head 2, the second moving average (after the second filter processing) obtained by performing the moving average processing with the second filter displacement) to output.
　磁気検出ヘッド２に対してスケール１が移動しているか否かの判定は、例えば、図５に示すように行われる。詳細には、フィルタ処理部３６は、第１移動平均と第３移動平均の差分である第１差分、及び、第１移動平均と第２移動平均との差分である第２差分、のそれぞれを所定の閾値と比較する。フィルタ処理部３６は、第１差分及び第２差分の何れも閾値より小さい場合、スケール１が静止していると判定する。一方、フィルタ処理部３６は、第１差分及び第２差分のうち少なくとも一方が閾値以上である場合、磁気検出ヘッド２が移動していると判定する。 Whether or not the scale 1 is moving with respect to the magnetic detection head 2 is determined, for example, as shown in FIG. Specifically, the filter processing unit 36 calculates a first difference that is the difference between the first moving average and the third moving average, and a second difference that is the difference between the first moving average and the second moving average. Compare with a predetermined threshold. The filtering unit 36 determines that the scale 1 is stationary when both the first difference and the second difference are smaller than the threshold. On the other hand, the filter processor 36 determines that the magnetic detection head 2 is moving when at least one of the first difference and the second difference is equal to or greater than the threshold.
　変位θ（ｔ）が変化した場合、３つの移動平均のうち第２移動平均が最も敏感に反応して変化し、第３移動平均、第１移動平均の順に反応が鈍くなる。第１差分及び第２差分は、時間遅れが移動平均段数に応じて異なることによる移動平均の差である。スケール１の移動速度がゼロに近い場合、変位θ（ｔ）は殆ど変化しないので、第１差分も第２差分も小さくなる。一方、スケール１の移動速度が相当に大きい場合は、変位θ（ｔ）が大きく変化するので、第１差分も第２差分も大きくなる。従って、フィルタ処理部３６は、実質的に、磁気検出ヘッド２に対するスケール１の相対速度の高低に関して判別しているということができる。 When the displacement θ(t) changes, the second moving average reacts most sensitively among the three moving averages, and the reaction slows down in the order of the third moving average and the first moving average. The first difference and the second difference are moving average differences due to the time lag being different according to the number of moving average stages. When the moving speed of the scale 1 is close to zero, the displacement θ(t) hardly changes, so both the first difference and the second difference are small. On the other hand, when the moving speed of the scale 1 is considerably high, the displacement θ(t) changes greatly, so both the first difference and the second difference become large. Therefore, it can be said that the filter processing section 36 substantially determines whether the speed of the scale 1 relative to the magnetic detection head 2 is high or low.
　磁気検出ヘッド２の相対速度の高低の判別手法は、上記に限定されない。例えば、第１差分及び第２差分のうち一方だけに基づいて判別を行っても良い。単に第１移動平均と第２移動平均との差分を所定の閾値と比較することで、判別を行っても良い。適宜の移動平均（例えば、第２移動平均）の現在値と所定時間前の値との差分を求め、この差分を所定の閾値と比較することで判別することもできる。 The method of determining whether the relative speed of the magnetic detection head 2 is high or low is not limited to the above. For example, determination may be made based on only one of the first difference and the second difference. The determination may be made simply by comparing the difference between the first moving average and the second moving average with a predetermined threshold value. The difference between the current value of an appropriate moving average (for example, the second moving average) and the value a predetermined time ago is obtained, and the difference can be determined by comparing the difference with a predetermined threshold value.
　フィルタ処理部３６により出力されたフィルタ処理後変位は、図５等に示すように、リニアリティ較正、予測演算等の後処理を経った後、位置情報として出力される。 The post-filtering displacement output by the filtering unit 36 is output as position information after undergoing post-processing such as linearity calibration and prediction calculation, as shown in FIG.
　上記のように、本実施形態の変位検出装置１００は、図６に示すように、磁気検出ヘッド２に対するスケール１の相対速度が比較的に小さい場合、４０９６段の移動平均処理により得られた値を検出値として出力し、スケール１の相対速度が比較的に大きい場合、１６段の移動平均処理により得られた値を検出値として出力する。なお、図６では、相対速度そのものを閾値と直接比較するように示されているが、これは便宜のために概念的に説明したものであって、実際の処理とは異なっている。 As described above, the displacement detection device 100 of this embodiment, as shown in FIG. is output as the detected value, and when the relative speed of the scale 1 is relatively large, the value obtained by the 16-step moving average process is output as the detected value. Although FIG. 6 shows that the relative velocity itself is directly compared with the threshold value, this is a conceptual explanation for convenience and differs from actual processing.
　このように、本実施形態の変位検出装置１００は、通常はトレードオフの関係にある良好な追従性及び精度を両立することができる。 Thus, the displacement detection device 100 of this embodiment can achieve both good followability and accuracy, which are usually in a trade-off relationship.
　以上に説明したように、本実施形態の変位検出装置１００は、変位検出方向における測定対象物の変位を検出する。変位検出装置１００は、スケール１と、磁気検出ヘッド２と、検出信号処理装置３と、を備える。スケール１には、変位検出方向に所定の検出ピッチで磁気応答部１２と非磁気応答部１１とが交互に配列されている。磁気検出ヘッド２は、サイン関数、コサイン関数、マイナスサイン関数及びマイナスコサイン関数で表現される出力信号のそれぞれを出力する少なくとも４つの２次コイル２２を有する。検出信号処理装置３には２次コイル２２の出力信号が入力され、検出信号処理装置３は、磁気検出ヘッド２に対するスケール１の相対変位を演算して出力する。検出信号処理装置３は、第１差動増幅器３１と、第２差動増幅器３２と、ＡＤ変換器（第１ＡＤ変換器３３及び第２ＡＤ変換器３４）と、演算処理部３５と、フィルタ処理部３６と、を備える。第１差動増幅器３１は、コサイン関数及びマイナスコサイン関数を合成して得られた第１交流信号ｙ１を出力する。第２差動増幅器３２は、サイン関数及びマイナスサイン関数を合成して得られた第２交流信号ｙ２を出力する。ＡＤ変換器は、第１交流信号ｙ１及び第２交流信号ｙ２をデジタル値に変換する。演算処理部３５は、デジタル値を演算処理して、スケール１の相対変位を出力する。フィルタ処理部３６は、磁気検出ヘッド２に対するスケール１の相対速度の高低に関して判別を行う。フィルタ処理部３６は、相対速度が低いと判別した場合、演算処理部３５から出力された相対変位を第１フィルタで処理して得られた第１フィルタ処理後変位を、スケール１の相対変位として出力する。フィルタ処理部３６は、相対速度が高いと判別した場合、演算処理部３５から出力された相対変位を第２フィルタで処理して得られた第２フィルタ処理後変位をスケール１の相対変位として出力する。第２フィルタは、第１フィルタより次数が低い。 As described above, the displacement detection device 100 of this embodiment detects the displacement of the object to be measured in the displacement detection direction. A displacement detection device 100 includes a scale 1 , a magnetic detection head 2 , and a detection signal processing device 3 . On the scale 1, magnetic response sections 12 and non-magnetic response sections 11 are alternately arranged at a predetermined detection pitch in the displacement detection direction. The magnetic detection head 2 has at least four secondary coils 22 that output respective output signals represented by a sine function, a cosine function, a minus sine function and a minus cosine function. The output signal of the secondary coil 22 is input to the detection signal processing device 3, and the detection signal processing device 3 calculates the relative displacement of the scale 1 with respect to the magnetic detection head 2 and outputs it. The detection signal processing device 3 includes a first differential amplifier 31, a second differential amplifier 32, AD converters (first AD converter 33 and second AD converter 34), an arithmetic processing unit 35, and a filter processing unit. 36 and. The first differential amplifier 31 outputs a first AC signal y1 obtained by synthesizing the cosine function and the minus cosine function. The second differential amplifier 32 outputs a second AC signal y2 obtained by synthesizing the sine function and the minus sine function. The AD converter converts the first AC signal y1 and the second AC signal y2 into digital values. The arithmetic processing unit 35 arithmetically processes the digital values and outputs the relative displacement of the scale 1 . The filtering unit 36 determines whether the speed of the scale 1 relative to the magnetic detection head 2 is high or low. When the filter processing unit 36 determines that the relative velocity is low, the displacement after the first filter processing obtained by processing the relative displacement output from the arithmetic processing unit 35 with the first filter is used as the relative displacement of the scale 1. Output. When the filter processing unit 36 determines that the relative velocity is high, the filter processing unit 36 outputs the second filtered displacement obtained by processing the relative displacement output from the arithmetic processing unit 35 with the second filter as the relative displacement of the scale 1. do. The second filter is of lower order than the first filter.
　これにより、磁気検出ヘッド２とスケール１との相対速度に応じて、異なる次数のフィルタで処理して得られた変位を出力することができる。従って、変位検出装置１００の追従性及び検出精度を両立することができる。 As a result, it is possible to output the displacement obtained by processing with filters of different orders according to the relative speed between the magnetic detection head 2 and the scale 1 . Therefore, both the followability and detection accuracy of the displacement detection device 100 can be achieved.
　また、本実施形態の変位検出装置１００において、フィルタ処理部３６は、第１移動平均と、第２移動平均と、第３移動平均と、のそれぞれを求める。第１移動平均は、第１フィルタ処理後変位に相当する。第２移動平均は、第２フィルタ処理後変位に相当する。第３移動平均は、演算処理部３５から出力された相対変位を第３フィルタで処理して得られた、第３フィルタ処理後変位に相当する。第３フィルタは、第１フィルタより次数が低く、第２フィルタより次数が高い。フィルタ処理部３６は、第１移動平均と第３移動平均との差分である第１差分、及び、第１移動平均と第２移動平均との差分である第２差分を用いて、磁気検出ヘッド２に対するスケール１の相対速度の高低に関して判別を行う。 Also, in the displacement detection device 100 of the present embodiment, the filtering unit 36 obtains each of the first moving average, the second moving average, and the third moving average. The first moving average corresponds to the first filtered displacement. The second moving average corresponds to the second filtered displacement. The third moving average corresponds to the post-third filtering displacement obtained by processing the relative displacement output from the arithmetic processing unit 35 with the third filter. The third filter has a lower order than the first filter and a higher order than the second filter. The filtering unit 36 uses the first difference, which is the difference between the first moving average and the third moving average, and the second difference, which is the difference between the first moving average and the second moving average. A determination is made as to whether the speed of scale 1 relative to scale 2 is high or low.
　これにより、磁気検出ヘッド２に対するスケール１の相対速度に関する判別を的確に行うことができる。 As a result, the relative speed of the scale 1 with respect to the magnetic detection head 2 can be accurately determined.
　ただし、本実施形態の変位検出装置１００において、フィルタ処理部３６は、第１移動平均と第２移動平均の差分に基づいて、磁気検出ヘッド２に対するスケール１の相対速度の高低に関して判別を行うように構成することもできる。 However, in the displacement detection device 100 of the present embodiment, the filter processing unit 36 determines whether the speed of the scale 1 relative to the magnetic detection head 2 is high or low based on the difference between the first moving average and the second moving average. can also be configured to
　この場合、磁気検出ヘッド２に対するスケール１の相対速度に関する判別を、簡素な処理で行うことができる。 In this case, it is possible to determine the relative speed of the scale 1 with respect to the magnetic detection head 2 by simple processing.
　また、本実施形態の変位検出装置１００において、演算処理部３５は、ａｒｃｔａｎ演算によりスケール１の変位を算出する。 Also, in the displacement detection device 100 of the present embodiment, the arithmetic processing unit 35 calculates the displacement of the scale 1 by arctan calculation.
　これにより、簡単な演算で、変位を得ることができる。 With this, the displacement can be obtained with a simple calculation.
　以上に本発明の好適な実施の形態を説明したが、上記の構成は例えば以下のように変更することができる。 Although the preferred embodiment of the present invention has been described above, the above configuration can be modified, for example, as follows.
　スケール１は、上述の構成に限定されず、互いに異なる磁気的な性質（磁性の強弱、発生する磁界の方向等）が繰り返されるのであれば、適宜の構成とすることができる。例えば、磁気応答部１２が、強磁性体と弱磁性体／非磁性体を、当該スケール１の長手方向に交互に並べることで構成されても良い。磁石のＮ極とＳ極を並べることで、磁気的な性質の変化の繰返しを実現しても良い。 The scale 1 is not limited to the configuration described above, and may have an appropriate configuration as long as different magnetic properties (strength of magnetism, direction of generated magnetic field, etc.) are repeated. For example, the magnetic response section 12 may be configured by alternately arranging a ferromagnetic material and a weakly magnetic material/non-magnetic material in the longitudinal direction of the scale 1 . By arranging the north and south poles of magnets, repetition of changes in magnetic properties may be realized.
　磁気検出素子は、２次コイル２２の代わりに、プリント基板の導電パターン、ホール素子等から構成されても良い。 Instead of the secondary coil 22, the magnetic detection element may be composed of a conductive pattern on a printed circuit board, a Hall element, or the like.
　２次コイル２２がスケール１（磁気応答部１２）からの変位に応じた変化を捉えることが可能であれば、１次コイル２１がスケール１に近い側に配置され、２次コイル２２がスケール１から遠い側に配置されても良い。 If the secondary coil 22 can detect the change according to the displacement from the scale 1 (the magnetic response section 12), the primary coil 21 is arranged on the side closer to the scale 1, and the secondary coil 22 is positioned closer to the scale 1. may be arranged on the far side from the
　演算処理部３５は、ｔａｎθを計算する以外の方法で、θを得ることもできる。具体的には、公知のシフト回路により第２交流信号ｙ２の位相が９０°シフトされて、第１交流信号ｙ１に加算される。加算後の信号は、周知の三角関数の加法定理により、ａｓｉｎ（ωｔ＋θ）と表すことができる。演算処理部３５は、この信号と、基準交流信号ａｓｉｎωｔと、の位相差（具体的には、各信号がゼロと交差するタイミングの差）を計測することにより、θを得る。また、演算処理部３５は、ＰＤ（Ｐｈａｓｅ－Ｄｉｇｉｔａｌ）変換によってθを得ることもできる。 The arithmetic processing unit 35 can also obtain θ by a method other than calculating tan θ. Specifically, the phase of the second AC signal y2 is shifted by 90° by a known shift circuit and added to the first AC signal y1. The signal after the addition can be represented as asin(ωt+θ) by the well-known addition theorem of trigonometric functions. The arithmetic processing unit 35 obtains θ by measuring the phase difference between this signal and the reference AC signal asinωt (specifically, the difference in the timing at which each signal crosses zero). Further, the arithmetic processing unit 35 can also obtain θ by PD (Phase-Digital) conversion.
　フィルタ処理部３６におけるスケール１の相対速度に対する判別は、リアルタイムで行われなくても良い。例えば、予め設定された一定の時間間隔で判別が行われても良いし、スケール１の相対速度に応じて変化する時間間隔で行われても良い。 The determination of the relative velocity of the scale 1 in the filter processing unit 36 does not have to be performed in real time. For example, determination may be performed at predetermined time intervals, or may be performed at time intervals that vary according to the relative speed of the scale 1 .
　上記の実施形態では、第１段目から第１６段目までのシフトレジスタは、第１フィルタ、第２フィルタ、及び第３レジスタで共有されている。第１段目から第２０４８段目までのシフトレジスタは、第１フィルタ及び第３フィルタで共有されている。しかし、シフトレジスタは、フィルタ毎に独立して設けられても良い。 In the above embodiment, the 1st to 16th shift registers are shared by the first filter, the second filter, and the third register. The first to 2048th shift registers are shared by the first and third filters. However, a shift register may be provided independently for each filter.
　第２フィルタが第１フィルタよりも次数が低い条件を満たせば、第１フィルタ及び第２フィルタとして、移動平均フィルタ以外のフィルタが用いられても良い。第３フィルタが第１フィルタより次数が低く、第２フィルタより次数が高い条件を満たせば、第３フィルタとして、移動平均フィルタ以外のフィルタが用いられても良い。 Filters other than moving average filters may be used as the first and second filters as long as the second filter satisfies the condition that the order is lower than that of the first filter. A filter other than the moving average filter may be used as the third filter as long as the third filter has a lower order than the first filter and a higher order than the second filter.
　変位検出装置は、スケール１の相対変位に代えて、又はそれに加えて、相対変位の変化速度を出力することもできる。相対変位の変化速度とは、実質的に、スケール１の相対速度を意味する。相対変位の変化速度は、スケール１の現在の相対変位と、所定時間前の相対変位と、の差を計算することにより、容易に得ることができる。 Instead of or in addition to the relative displacement of the scale 1, the displacement detection device can also output the rate of change of the relative displacement. The change speed of relative displacement substantially means the relative speed of scale 1 . The change rate of the relative displacement can be easily obtained by calculating the difference between the current relative displacement of the scale 1 and the relative displacement a predetermined time ago.
　図１及び図５において、符号を付していない処理（例えば、図５のオフセット補正量加算、ゲイン補正量乗算、ピッチカウント生成、ピッチ合成、リニアリティ較正、予測演算等の処理）については、使用される条件に応じて適宜省略されても良い。 In FIGS. 1 and 5, the unmarked processing (for example, processing such as offset correction amount addition, gain correction amount multiplication, pitch count generation, pitch synthesis, linearity calibration, prediction calculation, etc.) in FIG. It may be omitted as appropriate depending on the conditions.
　１　スケール
　２　磁気検出ヘッド（センサヘッド）
　３　検出信号処理装置（信号処理演算装置）
　１１　非磁気応答部
　１２　磁気応答部
　２２　２次コイル（磁気検出素子）
　３１　第１差動増幅器
　３２　第２差動増幅器
　３３　第１ＡＤ変換器
　３４　第２ＡＤ変換器
　１００　変位検出装置 1 scale 2 magnetic detection head (sensor head)
3 Detection signal processing device (signal processing arithmetic device)
11 non-magnetic response section 12 magnetic response section 22 secondary coil (magnetic detection element)
31 first differential amplifier 32 second differential amplifier 33 first AD converter 34 second AD converter 100 displacement detector

Claims (4)

  1. 　変位検出方向における測定対象物の変位を検出する変位検出装置であって、
    　変位検出方向に所定の検出ピッチで磁気応答部と非磁気応答部とが交互に配列されたスケールと、
    　サイン関数、コサイン関数、マイナスサイン関数及びマイナスコサイン関数で表現される出力信号のそれぞれを出力する少なくとも４つの磁気検出素子を有するセンサヘッドと、
    　前記磁気検出素子の出力信号が入力され、前記センサヘッドに対する前記スケールの相対変位、及び、前記相対変位の変化速度のうち少なくとも一方を演算して出力する信号処理演算装置と、
    を備え、
    　前記信号処理演算装置は、
    　前記コサイン関数及び前記マイナスコサイン関数を合成して得られた第１交流信号を出力する第１差動増幅器と、
    　前記サイン関数及び前記マイナスサイン関数を合成して得られた第２交流信号を出力する第２差動増幅器と、
    　前記第１交流信号及び前記第２交流信号をデジタル値に変換するＡＤ変換器と、
    　前記デジタル値を演算処理して、前記スケールの前記相対変位を出力する演算処理部と、
    　前記センサヘッドに対する前記スケールの相対速度の高低に関して判別を行い、前記相対速度が低いと判別した場合、前記演算処理部から出力された前記相対変位を第１フィルタで処理して得られた第１フィルタ処理後変位を前記スケールの相対変位として出力し、前記相対速度が高いと判別した場合、前記演算処理部から出力された前記相対変位を前記第１フィルタより次数が低い第２フィルタで処理して得られた第２フィルタ処理後変位を前記スケールの相対変位として出力するフィルタ処理部と、
    を備えることを特徴とする変位検出装置。     A displacement detection device for detecting displacement of an object to be measured in a displacement detection direction,
    a scale in which magnetic response portions and non-magnetic response portions are alternately arranged at a predetermined detection pitch in a displacement detection direction;
    a sensor head having at least four magnetic detection elements that output respective output signals expressed by a sine function, a cosine function, a minus sine function and a minus cosine function;
    a signal processing arithmetic unit that receives an output signal from the magnetic detection element and calculates and outputs at least one of a relative displacement of the scale with respect to the sensor head and a rate of change of the relative displacement;
    with
    The signal processing arithmetic device is
    a first differential amplifier that outputs a first AC signal obtained by synthesizing the cosine function and the minus cosine function;
    a second differential amplifier that outputs a second AC signal obtained by synthesizing the sine function and the minus sine function;
    an AD converter that converts the first AC signal and the second AC signal into digital values;
    an arithmetic processing unit that arithmetically processes the digital value and outputs the relative displacement of the scale;
    A determination is made as to whether the relative velocity of the scale with respect to the sensor head is high or low, and when it is determined that the relative velocity is low, a first The filtered displacement is output as the relative displacement of the scale, and when it is determined that the relative velocity is high, the relative displacement output from the arithmetic processing unit is processed by a second filter having a lower order than the first filter. a filter processing unit that outputs the displacement after the second filter processing obtained by the above as the relative displacement of the scale;
    A displacement detection device comprising:
  2. 　請求項１に記載の変位検出装置であって、
    　前記フィルタ処理部は、
    　前記第１フィルタ処理後変位に相当する第１移動平均と、
    　前記第２フィルタ処理後変位に相当する第２移動平均と、
    　前記演算処理部から出力された前記相対変位を、前記第１フィルタより次数が低く、前記第２フィルタより次数が高い第３フィルタで処理して得られた、第３フィルタ処理後変位に相当する第３移動平均と、
    のそれぞれを求め、
    　前記第１移動平均と前記第３移動平均との差分、及び、前記第１移動平均と前記第２移動平均との差分のうち少なくとも一方を用いて、前記センサヘッドに対する前記スケールの相対速度の高低に関して判別を行うことを特徴とする変位検出装置。     The displacement detection device according to claim 1,
    The filter processing unit is
    a first moving average corresponding to the displacement after the first filtering;
    a second moving average corresponding to the displacement after the second filtering;
    Corresponds to displacement after third filter processing obtained by processing the relative displacement output from the arithmetic processing unit with a third filter having a lower order than the first filter and a higher order than the second filter. a third moving average;
    find each of
    Using at least one of the difference between the first moving average and the third moving average and the difference between the first moving average and the second moving average, the relative speed of the scale with respect to the sensor head increases or decreases. A displacement detection device characterized in that it discriminates with respect to.
  3. 　請求項１に記載の変位検出装置であって、
    　前記フィルタ処理部は、
    　前記第１フィルタ処理後変位に相当する第１移動平均と、
    　前記第２フィルタ処理後変位に相当する第２移動平均と、
    のそれぞれを求め、
    　前記第１移動平均と前記第２移動平均との差分を用いて、前記センサヘッドに対する前記スケールの相対速度の高低に関して判別を行うことを特徴とする変位検出装置。     The displacement detection device according to claim 1,
    The filter processing unit is
    a first moving average corresponding to the displacement after the first filtering;
    a second moving average corresponding to the displacement after the second filtering;
    find each of
    A displacement detection device, wherein a difference between the first moving average and the second moving average is used to determine whether the relative velocity of the scale with respect to the sensor head is high or low.
  4. 　請求項１から３までの何れか一項に記載の変位検出装置であって、
    　前記演算処理部は、ａｒｃｔａｎ演算により前記スケールの変位を算出することを特徴とする変位検出装置。     The displacement detection device according to any one of claims 1 to 3,
    The displacement detection device, wherein the arithmetic processing unit calculates the displacement of the scale by arctan arithmetic.
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JPH0387606A (en) * 1989-06-22 1991-04-12 Sumitomo Metal Ind Ltd Method and device for measuring automatically tubular article
JPH0697823A (en) * 1992-09-16 1994-04-08 Okuma Mach Works Ltd Position controller
JP2012255732A (en) * 2011-06-09 2012-12-27 Sodick Co Ltd Position detecting device
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