JP2005172615A - Measuring device for coordinate displacement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring device for coordinate displacement capable of measuring the coordinate displacement with a simple constitution. <P>SOLUTION: This measuring device 10 for the coordinate displacement comprises magnetic body panels C and nonmagnetic body panels S placed on the surface of a desired measuring object, and arrayed alternately in the X-axis direction and in the Y-axis direction matrixingly respectively, and an detection head H arranged oppositely to the magnetic body panels and the nonmagnetic body panels, displaced relatively thereto in the noncontact state, and including an X-axis detection part and a Y-axis detection part by a plurality of impedance elements. The device 10 is characterized by outputting respectively an X-axis component detection signal and a Y-axis component detection signal corresponding to the relative position of the detection head H to the array surface of the magnetic body panels and the nonmagnetic body panels on the measuring object from the X-axis detection part and the Y-axis detection part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coordinate displacement measuring apparatus.

Japanese Patent Laid-Open No. 10-176926 JP-A-10-82607 JP-A-10-82608

  2. Description of the Related Art In recent years, a position displacement sensor that detects a position displacement of an object by obtaining a detection signal from each impedance element according to the relative position between an impedance element such as a coil and a magnetic response member made of a magnetic material (for example, Patent Document 1). Etc.) and the application range of this basic detection principle is wide, and therefore, it has been attempted to be applied to various uses.

The position displacement sensor detects a position displacement from an electrical phase difference that appears in an AC signal according to the relative position between an impedance element and a magnetic response member made of a magnetic material or the like. The basic detection principle is roughly as follows.
First, this position displacement sensor is roughly divided into two according to its driving principle. Hereinafter, these are referred to as an inductive type and an impedance type, respectively. In any type, there are a linear displacement detection method in which a plurality of impedance elements are linearly arranged and a rotation angle detection method in which the impedance elements are arranged in the circumferential direction. In the induction type, the secondary coil of the transformer is an impedance element. Thus, these arrays are formed (see Patent Document 1).

  Therefore, it is easy to understand the above-described position displacement sensor that detects the position displacement from the electrical phase difference that appears in the AC signal according to the relative position between the impedance element and the magnetic response member made of a magnetic material or the like, which is the subject of the present invention. First, the principle of operation of the linear type displacement sensor will be described with reference to FIG. FIG. 1A is an external perspective view, and FIG. 1B is a diagram showing the state of the impedance elements (L1 to L4) and the magnetic material array rod (3). In FIG. 1, 1 is a solenoid type primary coil, 2 is a secondary coil array coaxially arranged inside, and here, four coils L1 to L4 of the same standard are arranged at equal intervals. This secondary coil array functions as an impedance element. A magnetic material array rod 3 physically connected to the subject is inserted into the coil array so as to be coaxial with each coil center axis and movable in the axial direction. A plurality of cylindrical ferromagnets (magnetic response members) 4 are repeatedly provided at a predetermined pitch along the linear displacement direction on the magnetic material array rod 3. In the example shown in FIG. 1, the ferromagnetic body 4 is repeatedly provided with a pitch that is four times the coil arrangement interval (distance between adjacent coil centers). The rod axis of the magnetic material array rod 3 is made of a metal or plastic material that does not exhibit significant magnetism. There is a gap or non-magnetic material 8 between the adjacent ferromagnetic materials 4.

In each of the secondary coils L1 to L4, a sine wave voltage is induced by the mutual induction action from the primary coil 1 to which the sine wave voltage ASinωt is applied as shown in the figure. However, a change in the relative position between the magnetic material array rod 3 and each of the secondary coils L1 to L4 causes a change in magnetic coupling between the primary coil and each secondary coil and an accompanying inductance change. In the secondary coil, an induction output AC signal whose amplitude is modulated according to the linear position of the magnetic material array rod 3 is induced with different amplitude characteristics according to the displacement of the arrangement of the secondary coils. Axial position of magnetic array rod 3 in FIG. 1 (positions of L1 and L3: a position where the central part in the axial direction of each coil substantially corresponds to the boundary between ferromagnetic material 4 and gap or nonmagnetic material 8. , L2 and L4 positions: substantially L2 corresponds to the axial central portion of the ferromagnetic body 4, L4 corresponds to the axial central portion of the nonmagnetic body 8) d = 0, and If the movement to the right in the figure is a positive direction, the L1-L3 differential output is converted into an induced sine wave Sinωt by an amplitude function aSind (a is a constant, The same applies below) aSindSinωt
The L2-L4 differential output is a value obtained by multiplying the induced sine wave Sinωt by an amplitude function aCosd corresponding to a coefficient that fluctuates, that is, a position displacement, aCosdSinωt
It becomes. Here, the amplitude functions aSind and aCosd change with the repetition unit (= 1 pitch displacement) of the ferromagnetic material 4 on the magnetic material array rod 3 as one cycle. That is, the amplitude function can process 1 pitch as 2π [rad], and the mechanical displacement for the electrical phase difference of 360 degrees corresponds to 1 pitch.

  Next, the operation principle of the rotation method will be described with reference to FIG. In FIG. 2, each of the coils L1 to L4 constituting the secondary coil 2 ′ has a central axis parallel to the central axis of the primary coil 1 ′, and is inscribed in the form inscribed in the primary coil 1 ′. Arranged at intervals. Each secondary coil L1-L4 has the pole iron core 5 arrange | positioned coaxially with each center axis | shaft. The end faces of these pole cores are all aligned on substantially the same axial cross section. A magnetic sleeve eccentric plate 6 for covering the pole core 5 of the secondary coil according to the rotational position is provided on the shaft sleeve arranged coaxially with the central axis of the primary coil (= the central axis of the secondary coil arrangement). It is supported. The magnetic body eccentric plate 6 is physically coupled to the subject so that it can rotate according to the movement of the subject. The magnetic body eccentric plate 6 rotates with the central axis of the primary coil as a rotation axis, and accordingly, a portion 9 of the magnetic body eccentric plate 6 that is substantially farthest from the rotation axis is sequentially turned into the secondary coils L1 to L1. It passes over the pole core 5 of L4.

  A sinusoidal voltage based on the sinusoidal voltage ASinωt applied to the primary side is induced in each of the secondary coils L1 to L4 by mutual induction with the primary coil 1 ′, but the rotation of the magnetic eccentric plate 6 described above is performed. A change in the magnetic coupling between the primary coil and each secondary coil according to the position and an accompanying inductance change occur, whereby each secondary coil is amplitude-modulated according to the rotational angular displacement of the magnetic eccentric plate 6. The induction output AC signal is induced with different amplitude characteristics according to the displacement of the arrangement of the secondary coils. The coil end-to-end voltages induced in each of these secondary coils are doubled and detected if they are differentially taken out in the L1-L3 group and the L2-L4 group whose arrangement relationship is 180 degrees (opposite phase). Obviously you can.

When the magnetic body eccentric plate 6 is in the angular position shown in FIG. 2B (= the portion 9 of the magnetic body eccentric plate 6 that is substantially farthest from the rotation axis is on the right side in the horizontal direction when viewed from the central axis 7). If the angular position in the 12 o'clock direction (= the position corresponding to L1) is defined as θ = 0 and the clockwise rotation of the eccentric plate 6 in the figure is the positive direction, the secondary coil L1 The −L3 differential output is a value obtained by multiplying the induced sine wave Sinωt by the coefficient, that is, the amplitude function aSinθ corresponding to the angular displacement, that is,
aSinθSinωt
It becomes. On the other hand, the L2-L4 differential output is a value obtained by multiplying the induced sine wave Sinωt by an amplitude function aCosθ corresponding to a coefficient, that is, an angular displacement, that is,
aCosθSinωt
It becomes. Here, the amplitude functions aSinθ and aCosθ change with one rotation of the magnetic material eccentric plate 6 as one cycle. Therefore, the amplitude function can be processed in the same manner as in the case of the linear method with a 360-degree displacement of θ as one pitch.

  The connection diagram of FIG. 3 shows these relationships collectively for a straight line and a rotational angular displacement in a circuit form.

  A similar relationship is also established when L1 to L4 are impedance elements that are substantially composed only of self-inductances and a sinusoidal voltage ASinωt is directly applied to them (hereinafter referred to as an impedance type). This is shown in the circuit diagram of FIG. In the present invention, in the direct impedance type, the coordinate displacement is determined by the electrical phase difference that appears in the output AC signal according to the relative position between the impedance element and the magnetic response member (magnetic panel) made of a magnetic material or the like. The present invention relates to a novel sensor structure to be measured.

Therefore, in the impedance type, if the terminal voltages of the impedance elements (coils L1 to L4) obtained in the same manner as described above are represented by α as the sine coefficient formula and β as the cosine coefficient formula, In the case of linear displacement, it can be expressed as follows. a is a constant as appropriate.
α = aSin (θ, d) · Sinωt
β = aCos (θ, d) · Sinωt

From these equations, the actual rotational angle displacement θ or linear displacement d of the subject (if the electrical phase angle is θ, this corresponds to the mechanical displacement in each axial direction, and will be described below by the notation of θ). As an arithmetic circuit for obtaining the above, first, the equations 1 and 2 are respectively multiplied by the cosine function Cosφ and the sine function Sinφ of the digital phase value φ sequentially increasing from 0,
Sinφ · Cosθ-Cosφ · Sinθ = 0 ·········· Equation 3
At this point, a known RD conversion method in which θ is specified as θ = φ can be cited (see Patent Document 1). In this method, a clock delay occurs when φ is followed and counted, and there is room for improvement in terms of responsiveness.

The following methods are also known in the past. That is, Sinωt in Equation 1 is converted to Cosωt on the circuit to obtain aSin (θ, d) · Cosωt, and then the addition theorem of the trigonometric function is applied, so that the sine wave signal aSin including the positional displacement as a phase difference is obtained. In this method, (ωt ± θ, d) is obtained, and the position displacement (θ, d) of the subject is obtained therefrom. This is shown in Equation 4 below. Hereinafter, this method is referred to as a phase difference conversion (PD conversion) method. Note that aSin (ωt + θ, d) is a lead phase wave P, and aSin (ωt−θ, d) is a delayed phase wave M.
aSin (θ, d) · Cosωt ± aCos (θ, d) · Sinωt =
aSin (ωt ± θ, d) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 4

  Regarding this phase difference conversion method, FIG. 5 shows operation waveforms and analysis procedures. FIG. 5A is a waveform diagram of the applied voltage ASinωt and the amplitude-modulated signals on the right side of Equations 1 and 2, and FIG. 5B is a graph including the graph of ASinωt and a specific phase difference (θ, d). (C) It is a waveform diagram showing the time relationship with the graph of the sine wave on the right side, in this case the delayed phase wave M = aSin (ωt−θ, d). FIG. 5C shows the mathematical transition that is the basis for deriving the waveform diagram shown in FIG. FIG. 6 is a block diagram of an arithmetic circuit that specifically realizes the operation of FIG. 5C on the circuit. The signals α and β expressed by Equations 1 and 2 are each subjected to amplification (amplification b / a) and phase shift and addition processes before being input to the phase detector 18. In FIG. 5B, in the case of the leading phase wave P = aSin (ωt + θ, d), the graph is symmetrical with the solid line of the delayed phase wave M = aSin (ωt−θ, d) shown by the broken line. It becomes a sine wave that precedes in time by (θ, d) from the graph of ASinωt shown in FIG.

  As is apparent from the graph of FIG. 5B, to obtain θ or d, the delayed phase wave M = aSin (ωt−θ, d) or the leading phase wave P = aSin (ωt + θ, d) from the zero cross point of the ASinωt graph. ) Count the time to the zero cross point of the graph.

  By the way, all of the inductive or impedance type position displacement sensors measure a one-dimensional position such as a linear position or a rotational position, and none of them measure a two-dimensional position. The inductive or impedance-type position displacement sensor is structurally non-contact, and can be easily and inexpensively manufactured with a simple configuration of a magnetic response member made of an impedance element and a magnetic body. If this can be applied to a two-dimensional position detection device, a wide range of applications and uses can be expected. From such a viewpoint, the inventions described in Patent Documents 2 and 3 have been proposed. All of these inventions are related to the induction type, but a coil is embedded in a measurement object in advance, or these are connected. Therefore, there is a problem that it is necessary to configure a detection circuit, an arithmetic circuit, and the like, and it is troublesome to mount each component in the measurement target, and it is necessary to secure a mounting space again. Furthermore, since the measurement range is limited to the vicinity of the coil embedded in the measurement object, there is a problem that it is difficult to measure a wide range of coordinate displacement.

The present invention has been made in view of the above points, and an object of the present invention is to provide a coordinate displacement measuring apparatus capable of measuring coordinate displacement with a simple configuration.
Another object of the present invention is to provide a coordinate displacement measuring apparatus capable of accurately measuring coordinate displacement in a wide range.

  As a result of various studies to solve the above-mentioned problems, the inventor has developed the length measurement principle of the above-described inductive or impedance-type position displacement sensor in a planar or other multi-dimensional manner, that is, an object to be measured. By alternately arranging a magnetic panel and a non-magnetic panel in the direction of each coordinate axis in a matrix on the surface, the detection head is composed of a set of impedance elements for measuring the position displacement for each axis, The present inventors have found that coordinate displacement can be measured with a simple configuration and completed the present invention.

The coordinate displacement measuring apparatus of the present invention capable of solving the above-described problems is a magnetic panel placed on the surface of a desired object to be measured and arranged alternately in the X-axis direction and the Y-axis direction in a matrix form, respectively. A non-magnetic body panel, and an X-axis detection unit and a Y-axis detection unit that are arranged relative to the magnetic body panel and the non-magnetic body panel and are displaced in a non-contact manner relative to the non-magnetic body panel. An X-axis component detection signal and a Y-axis component detection signal corresponding to the relative position of the detection head with respect to the arrangement surface of the magnetic panel and the non-magnetic panel of the object to be measured. The X-axis detection unit and the Y-axis detection unit respectively output the data.
The X-axis and Y-axis referred to in the present invention are examples of names of axes on one side and the other side that intersect and extend on a two-dimensional plane, and are not limited to those orthogonal to each other. Also, when magnetic and non-magnetic panels are alternately arranged in the direction of each coordinate axis in a matrix on the surface of the object to be measured, the magnetic panels or non-magnetic panels are not adjacent to each other on the surface of the object to be measured. In the same way, it means that the magnetic panel and the non-magnetic panel are arranged by mistake.

Therefore, according to the present invention, the detection principle of the position displacement of the linear displacement that is currently used and used in cylinders, die cast machines, etc., pointer devices that designate arbitrary coordinate positions, surface mounters, and other planes The present invention can be extended to devices that require measurement of coordinate displacement. In addition, according to the present invention, it is possible to measure the coordinate displacement without contact with the object to be measured, and only one detection head is required, and a detection circuit or the like may be incorporated therein, thereby simplifying the configuration. Can be
Furthermore, since the coordinate displacement measuring device of the present invention is a detection device using magnetism, it is less susceptible to adhesion of dust, dust, and the like than those employing a conventionally known optical detection principle. However, it can be said that the environment resistance is high in that it can exhibit the same performance and can provide a stable detection output regardless of the installation environment.

The magnetic panel and the non-magnetic panel of the present invention do not need to be rigid, and can be composed of sheet-like ones. Therefore, even when the object to be measured is a curved surface, these are arranged on the curved surface. By appropriately pasting the sheet, the coordinate displacement can be detected.
In addition, the surface or the detection head provided with the magnetic panel and the non-magnetic panel of the object to be measured does not necessarily have to be on a horizontal plane. According to the coordinate position measuring apparatus of the present invention, the plane is not limited to the horizontal plane. The coordinate position on the inclined surface can also be measured. Further, according to the coordinate displacement measuring apparatus of the present invention, the coordinate displacement can be accurately measured in a wide range by appropriately using a correction calculation as described later. Hereinafter, the present invention will be described in more detail.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
7A and 7B are diagrams showing an example of the configuration of the coordinate displacement detection apparatus of the present invention, in which FIG. 7A is a plan view and FIG. 7B is a front view thereof. 8A and 8B are partially enlarged views of FIG. 7A showing the arrangement of impedance elements for each axis detection unit of the detection head, where FIG. 8A is an X-axis direction detection unit and FIG. 8B is a Y-axis direction detection. It is a figure showing arrangement | positioning of a part. 9A and 9B are diagrams showing changes in the output voltage from the impedance element, where FIG. 9A shows changes in the output voltages of the coils L2 and L4, and FIG. 9B shows characteristics of the L2-L4 differential output. . FIG. 10 is a circuit diagram showing the configuration of each axis detection unit of the detection head, FIG. 11 is a diagram showing the state of processing in the converter, and FIG. 12 is another arrangement example of impedance elements in the detection head. FIG. 7 to 12, the same components as those shown in FIGS. 1 to 6 are denoted by the same reference numerals.
Further, the position of the detection head H in FIG. 7A in the X-axis direction and the Y-axis direction is d _x = d _y = 0, and as shown by the arrows in FIG. The upward movement is defined as the positive direction in the X-axis direction and the Y-axis direction, respectively. In the present embodiment, the X axis and the Y axis are substantially orthogonal.

[Constitution]
First, a configuration example of the coordinate displacement measuring apparatus of the present invention will be described with reference to FIG.
As shown in FIG. 7, a panel (core panel) C made of a magnetic material and a panel (spacer panel) S made of a non-magnetic material are arranged in a matrix on the surface of the object whose coordinates are to be detected. And are alternately arranged in the Y-axis direction. In the example shown in FIG. 7, a total of 16 magnetic panels C and 8 nonmagnetic panels S are arranged on the surface of the object to be measured. In this example, the nonmagnetic panel S is made of a metal or plastic material that does not exhibit significant magnetism.
In the example shown in FIG. 7, the configuration of each axis detection unit of the detection head H described later is a one-phase excitation four-coil system, and therefore each coil arrangement interval constituting the detection head H (distance between adjacent coil centers). 4) is a basic unit of the interval at which the magnetic panel C and the non-magnetic panel S are continuously arranged, that is, the detection pitch (mechanical displacement with respect to an electrical phase difference of 360 degrees). Therefore, a desired detection pitch is realized by appropriately adjusting the coil diameter or the coil arrangement interval. Also in the example of FIG. 7, each impedance element is arranged within the range of the one pitch.

  In FIG. 7, H is a detection head, and in the apparatus of this embodiment for measuring a plane coordinate displacement, the detection head is a combination of two sets of an X-axis detection unit and a Y-axis detection unit. The X-axis detection unit displays an X-coordinate value, and the Y-axis detection unit displays a Y-coordinate value. In the present embodiment, both the X-axis detection unit and the Y-axis detection unit are composed of four impedance elements (coils L1 to L4, R1 to R4) of the same standard, and Y-axis component detection signals α and β described later or X-axis component detection signals γ and δ are output. Unlike the inductive type shown in FIG. 1 and others, the coordinate displacement measuring device described in this section is an impedance type, and therefore a primary coil is unnecessary.

  As shown in FIG. 7 or FIG. 12, in this embodiment, as a configuration example of the detection head H, eight coils as impedance elements are arranged in a frame of 3 rows 3 columns or 4 rows 5 columns (5 rows 4 columns). Things are listed. In the example illustrated in FIG. 7, the X-axis detection unit on one side of the detection head H includes two impedance elements R1 to R4 arranged in the first row and the third row extending in the X-axis direction, and the other side. The Y-axis detection unit includes impedance elements L1 to L4 arranged in the first row and the third row extending in the X-axis direction, and two impedance elements L1 to L4 arranged in the second row, respectively. R1 is arranged at the center of the nonmagnetic panel S, L3 and R3 are arranged at the center of the magnetic panel C, and the others are arranged at the boundary between the magnetic panel C and the nonmagnetic panel S2. As shown in FIG. 7B, the detection head H is arranged in a non-contact manner on the upper surface of the object to be measured provided with the magnetic panel C and the non-magnetic panel S.

[Detection operation]
As shown in FIGS. 8A and 8B, in the detection head H configured as shown in FIG. 7, the coils R1 to R4 are X-axis detection units, and the coils L1 to L4 are Y-axis detection units. The displacement in the X-axis direction and the displacement in the Y-axis direction are detected. The detection head H is in the X-axis or Y-axis direction in the circle showing the impedance elements R1 to R4 in FIG. 8A and in the circle showing the impedance elements L1 to L4 in FIG. An amplitude function indicating a voltage characteristic of an output signal generated by a change in self-inductance of each element as it moves is written. In the figure, the minus sine function or the minus cosine function has “-” (bar) on Sin or Cos.

  The detection principle for each axis is as follows and is substantially the same as the position displacement sensor of the linear displacement detection method described above. In this example, an impedance type detection method is used, and an AC power source Sinωt is directly connected to each coil. FIG. 10 shows a circuit representation of the configuration of each axis detection unit of the detection head. Note that FIGS. 8 to 11 are referred to for connection of impedance elements and calculation of coordinate displacement for each axis detection unit. In the following, attention will be paid to the case of movement in the Y-axis direction, the displacement detection method will be described, and then the coordinate displacement calculation will be described.

  First, paying attention to the coil L2, when the coil L2 moves in the Y-axis direction, the impedance of the coil changes, and an output voltage as shown by a solid line in FIG. 9A appears. Similarly, an output voltage as indicated by a broken line in FIG. 9A also appears in the coil L4. If these differential outputs are taken, a signal of aSinθ can be obtained as shown in FIG. 9B. Similarly, by connecting the coils L1 and L3 so as to obtain a differential output, a signal of aCosθ can be obtained. The aSinθ or aCosθ is a coefficient part of the reference signal component (Sinωt) (Formula 1 and Formula 2).

  The arrangement of the impedance elements constituting the X-axis detection unit is as shown in FIG. 8A, and the detection method and others are the same as in the case of the Y-axis.

As shown in FIGS. 8 to 10, when the reference signal ASinωt is excited in the impedance elements (coils L <b> 1 to L <b> 4, R <b> 1 to R <b> 4) constituting each axis detection unit, the detection head H comes directly under the movement. Depending on the position of the magnetic panel C or the non-magnetic panel S, the impedance (self-inductance) of each coil changes.
For example, paying attention only to the Y axis composed of the coils L1 to L4, when the coils L2 to L4 differential output α and L1 to L3 differential output β are taken out from the detection circuit having the configuration shown in FIG.
α = aSinθSinωt ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Equation 1
β = aCosθSinωt ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 2
It becomes. a is a constant as appropriate. The signals (Y-axis detection signals) α and β from these detection circuits are amplified (amplification factor b / a) at the input unit 19 of the arithmetic circuit 15, and then the signal α is electrically connected to the Sinωt unit through the phase shift circuit 16. Processing for delaying the phase by π / 2 is performed.
α ′ = aSinθSin (ωt−π / 2)
= ASinθCosωt ......... Equation 1 '
By calculating this and β shown in Equation 2 by applying the addition theorem as shown in Equation 4, the leading phase wave P = aSin (ωt + θ) or the delayed phase wave M = aSin (ωt−θ) can be obtained. Therefore, mechanical displacement is detected from the phase difference between these and the reference excitation signal ASinωt (phase difference detection method). The same applies to the case of the X axis.

The mechanical displacement is detected by setting one pitch (= the length of one set of the magnetic panel C and the non-magnetic panel S or the arrangement interval of the magnetic panels C) to an electrical angle of 360 ° (one cycle). When the detection head H moves and a displacement of θ is obtained, it can be obtained by setting d = (θ / 360) × p. Here, p is the length of one pitch, d is a mechanical displacement, and for each axis component, d _{x is the} X-axis component position and d _{y is the} Y-axis component position.

[Calculation of detection signal in converter]
Next, the processing in the converter for deriving the position displacement in the X-axis or Y-axis direction from the output signals (Y-axis component detection signals α, β or X-axis component detection signals γ, δ) obtained from each impedance element. This will be described with reference to FIGS. 10 and 11. The converter 35 is provided for each axis detection unit, and includes an arithmetic circuit 15 including an amplification unit 19, a phase shift unit 16, an addition unit 17, and a phase detection unit 18, respectively. The microcomputer 36 and the lookup table 37 in the figure will be described later. The differential outputs α to δ from each axis detection unit are connected to the amplification unit 19 of the arithmetic circuit 15.
As shown in FIG. 11A, in the present embodiment, a phase difference conversion (PD conversion) method conventionally known in an inductive or impedance type position displacement sensor that detects a linear displacement or a rotation angle is used. The position displacement in the X-axis or Y-axis direction is derived. The P-D conversion is as described above. As is apparent from FIGS. 10 and 11, each axis detection unit determines that these are L2-L4 or R2-R4 (α, γ), Then, after being converted into two kinds of differential outputs of L1-L3 or R1-R3 (β, δ), it is inputted to the arithmetic circuit 15 in the converter 35 and subjected to amplification, phase shift and addition processing. A phase detection process is performed later to derive a position displacement in the Y-axis or X-axis direction. If the derived displacement in the Y-axis or X-axis direction is appropriately expressed as a coordinate displacement in the form of (X coordinate: Y coordinate = d _x : d _y ), the device of the present invention functions as a coordinate displacement measuring device. Will be clear.

  As described above, according to the coordinate displacement measuring apparatus of the present invention having the coil arrangement or the detection head as shown in FIG. 7 or FIG. From the value of a sine wave signal (Y-axis component detection signal α, β or X-axis component detection signal γ, δ) having an output level or an amplitude function corresponding to each self-inductance or the like obtained, the X-axis or Y-axis It is possible to derive the positional displacement in the direction, and thus the coordinate displacement on the two-dimensional plane.

  Regarding the output value of the detection distance or the coordinate displacement from the detection head, in the case of the coil arrangement placed in the 3 × 3 frame shown in FIG. 7A, the magnetic panel C and the non-magnetic panel When the combination of S is one pitch and the position of the detection head H in FIG. 7A is used as a reference, the detection head H is within the range of the magnetic panel C and the non-magnetic panel S that are initially opposed to each other in FIG. That is, within the range of ± 1/4 pitch, especially ± 1/8 pitch in the X and Y axis directions (see FIG. 9B), the output from the detection head H is a coordinate displacement that does not require any correction. Display the value. The same applies to a detection head having a coil arrangement as shown in FIG.

The configuration, operation, and the like of the coordinate displacement measuring apparatus according to one embodiment of the present invention are as described in the accompanying drawings including FIGS. 7 to 12 and the above-mentioned [Mode for Carrying Out the Invention]. is there.
Thus, the phase difference θ output from the phase detector 18 of each arithmetic circuit 15 connected to the X-axis detector or Y-axis detector is the displacement of the X-axis component or the Y-axis component in the X-axis detector or Y-axis detector. Is equivalent to the displacement (d _x , d _y ). At this time, if 16-bit processing is performed to divide one pitch, that is, the repetitive pitch of the magnetic panel C, for example, 2 ¹⁶ = 65536, if 1 pitch = 10 mm, the X-axis detection unit or the Y-axis detection unit is 10,000 / A resolution of 65536≈0.15 [μm] can be obtained.

In this embodiment, in order to widen the detection range, a conversion table called a look-up table is used, and some errors that may occur when the detection head moves out of the ± 1/4 pitch range. The included waveform or output value can be corrected.
In the case of the coil arrangement shown in FIG. 7 or FIG. 12, the detection head output is used to correct the error between the coordinate displacement value obtained from the output value to which the PD conversion is applied and the actual coordinate displacement value. Lookup tables such as a contrast conversion table between values (values including errors) and true values (actual correct position displacements or coordinate displacements for each axis) can be used for inspections when manufacturing the device of the present invention. It may be prepared in advance based on the actually measured output value and provided in the converter 35 via a storage medium (memory 37) such as a correction ROM as illustrated in FIG. The CPU (microcomputer) 36 performs processing for sequentially comparing the signals actually obtained from the respective coils with the look-up table so that the output signals (including errors) actually obtained from the respective coils (including the Y axis). Component detection signal α, β or Can easily obtain the true value from the X-axis component detection signals γ, δ). As shown in FIG. 11, the position displacement value in the X-axis or Y-axis direction output from the arithmetic circuit 15 is input to the CPU 36 in the same converter 35. The CPU 36 has a built-in or electrically connected memory 37 in which a lookup table is stored, and values inputted from the arithmetic circuit 15 are sequentially compared with the lookup table in the CPU 36. After the contrast process, the CPU 36 obtains the correct position displacement value in the X-axis or Y-axis direction after the correction calculation.
According to the coordinate displacement measuring apparatus of the present embodiment, the coordinate displacement of the detection head H is accurately measured in a wide range without any particular limitation on the detection range by appropriately using correction calculation or the like as described above. be able to.

In this embodiment, as shown in FIG. 11B, the processing in the converter 35 for deriving the position displacement in the Y-axis or X-axis direction from the output signal obtained from each impedance element is performed in the Y-axis or X-axis direction. Is detected based on the output level of each of the individual coils L1 to L4 or R1 to R4 directly input into the converter 35. In this embodiment, correction calculation is appropriately performed at the same time. As in the first embodiment, a conversion table called a lookup table is used for the correction calculation. At this time, output signals respectively obtained from the four coils are input to the CPU 36, and a process of comparing with a look-up table stored in a memory 37 installed inside or outside thereof is performed.
The information stored as the look-up table includes, for example, position displacements or coordinates for each axis obtained from output signals (Y-axis component detection signals α, β or X-axis component detection signals γ, δ) obtained from four coils. Information on the error (error information) between the displacement value and the actual correct position displacement or coordinate displacement for each axis can be mentioned. Alternatively, from the output signals obtained from the four coils of each axis or the position displacement or coordinate displacement values (including errors) for each axis obtained from these, this is used as an address to directly correct the actual position displacement for each axis. Alternatively, it is possible to reach the value (true value) of the coordinate displacement, and then, a method is adopted in which information about the true value is written in advance in the ROM for correction calculation when the apparatus of the present invention is manufactured. .

As described above, the configuration for measuring the two-dimensional coordinate displacement has been mainly described as an embodiment of the present invention. However, the present invention is not limited to the above-described embodiment, and various design changes can be made.
For example, the crossing angle between the axes on one side and the other side extending in a crossing manner on the two-dimensional plane is not limited to the right angle as described above as the X axis and the Y axis.
As for the coordinate displacement measurement, the coordinate displacement measuring device of the present invention is combined with a rough coordinate displacement measuring means separately, and the rough coordinate displacement is determined in advance, and then the coordinate displacement is accurately measured by the device of the present invention. It doesn't matter if you do.
Further, a signal (= excitation signal) applied to each impedance element may be a digital signal made up of a so-called pulsed rectangular wave instead of an analog signal made up of a sinusoidal AC voltage, for example. Such a configuration eliminates complicated analog circuit element precision control. Also with such a configuration, the same performance as when an analog sine wave AC signal is input to each impedance element can be obtained. At this time, the digital signal used as the excitation signal can be directly output from a microcomputer used for phase difference detection or other control of the coordinate displacement measuring device of the present invention, and an output signal from the microcomputer. Can be applied to each impedance element after appropriate digital signal processing.

  The number and arrangement of the impedance elements are not limited to those described in the above embodiments, and various values can be adopted. Even in the case of such a configuration, the correct coordinate displacement can be measured by changing the calculation method in the phase detection unit or by using correction by a lookup table at the time of phase detection.

  Furthermore, instead of applying a sinusoidal voltage to each impedance element (= excitation of the coil) that has been performed in only one phase in each of the above examples, an AC voltage having a phase shift is applied to the first end of each impedance element. By connecting an AC power supply to be supplied and collectively connecting the second ends of the impedance elements, the impedance elements and the An AC signal having a phase difference corresponding to a change in impedance associated with a change in relative position between the magnetic panel C and the non-magnetic panel S is taken out and used to measure the coordinate displacement of the object to be measured. You can also At this time, excitation signals shifted by ωt = 2π / n (where n is the number of impedance elements constituting the X-axis or Y-axis detection unit) can be input to the first ends of the coils serving as impedance elements.

The impedance element is not limited to a coil, and may be a magnetoresistive element (MR), for example. However, when a magnetoresistive element is used as each impedance element, it is necessary to separately apply a bias magnetic field (field magnetic field) to each magnetoresistive element as described in Japanese Patent Application Laid-Open No. 2000-292113. is there. Since the magnetoresistive element can be significantly reduced in size as compared with a coil that is an example of an impedance element, the detection head can be reduced in size and the detection pitch can be reduced, which contributes to improvement in detection accuracy of the apparatus.
In each of the above examples, the nonmagnetic panel S is made of a metal or plastic material that does not exhibit significant magnetism, but in addition, only the magnetic panel C is left and the portion where the nonmagnetic panel S is disposed is used as a gap. In addition, a diamagnetic material may be provided between the magnetic panels C instead of the gaps.

  In each of the above examples, the magnetic panel C and the non-magnetic panel S have been described as being arranged on the object to be measured. However, the coordinate displacement measuring apparatus of the present invention has the impedance elements, the magnetic panel C, and the non-magnetic panel C. Since the coordinate displacement of the object to be measured is measured from the relative position of the magnetic panel S, the object to be measured may be physically coupled to the detection head H side.

  In addition, it goes without saying that the coordinate displacement measuring device of the present invention is not limited to the above-mentioned application targets but can also be applied to various objects.

  Furthermore, the present invention is not limited to the measurement of two-dimensional coordinate displacement, but can be applied to, for example, NC (numerical control) machine tools, rapid prototyping machines, and other devices that measure three-dimensional coordinate displacement. Is.

  As shown at the beginning, in addition to linear displacement, it is possible to detect a rotation angle in addition to linear displacement. By combining these, even when detecting two-dimensional coordinate displacement, a planar coordinate system or XYZ axes The coordinate system is not limited to the above, and a polar coordinate system can also be used.

  Thus, the present invention makes use of the basic principle of the position displacement sensor that detects the position displacement from the electrical phase difference that appears in the AC signal according to the relative position of the impedance element and the magnetic response member made of a magnetic material, etc. It is clear that a small coordinate displacement measuring apparatus that is inexpensive, simple and excellent in environmental performance can be provided.

It is a figure which shows typically the structure of the linear displacement detection sensor by the conventional guidance system. It is a figure which shows typically the structure of the rotational displacement detection sensor by the conventional guidance system. FIG. 3 is a circuit diagram showing how a linear displacement or a rotational angular displacement is detected using the configuration of FIG. 1 or FIG. 2. An impedance type position displacement sensor circuit that can detect linear displacement or rotational angular displacement in the same manner by using an impedance element that substantially consists of only self-inductances L1 to L4 instead of the transformer structure in the induction system of FIG. FIG. It is a figure which shows the operation | movement waveform and analysis procedure of a linear displacement and a rotational displacement detection sensor, (A) is a voltage waveform figure which shows the applied voltage ASinωt and the amplitude-modulated applied voltage signal, (B) is a graph of ASinωt A waveform diagram showing a time relationship with a graph of a sine wave aSin (ωt−θ, d) including a specific phase difference (θ, d), and (C) shows a mathematical transition as a basis of these waveform diagrams. It is a figure. FIG. 6 is a block diagram of a circuit that specifically realizes the operation shown in FIG. FIG. 7 is a diagram illustrating a configuration example of a coordinate displacement measuring apparatus according to the present invention. FIG. 8 is a partially enlarged view of FIG. 7A showing the arrangement of impedance elements for each axis detection unit of the detection head. It is a figure showing the change of the output voltage from an impedance element. It is the figure which represented the structure for every axis | shaft detection part of a detection head like a circuit. It is a figure which shows the mode of the process in a converter. It is a figure which shows another example of arrangement | positioning of the impedance element in a detection head.

Explanation of symbols

C Magnetic panel H Detection head L1 to L4 Coil R1 to R4 Coil S Nonmagnetic panel 1 Primary coil 1 'Primary coil 2 Secondary coil 2' Secondary coil 3 Magnetic material array rod 4 Ferromagnetic material 5 Polar core 6 Magnetic Body eccentric plate 7 Central axis 8 Nonmagnetic material 9 Part of magnetic material eccentric plate 10 Coordinate displacement measuring device 15 Arithmetic circuit 16 Phase shift unit 17 Addition circuit based on additive theorem 18 Phase detection unit 19 Amplifying unit 35 Converter 36 Microcomputer 37 memory

Claims (3)

A magnetic panel and a non-magnetic panel placed on the surface of a desired object to be measured and arranged alternately in a matrix in the X-axis direction and the Y-axis direction,
A detection head including an X-axis detection unit and a Y-axis detection unit by a plurality of impedance elements, which is disposed relative to the magnetic panel and the non-magnetic panel, and is displaced without contact with the magnetic panel;
An X-axis component detection signal and a Y-axis component detection signal corresponding to the relative position of the detection head with respect to the arrangement surface of the magnetic panel and the non-magnetic panel of the object to be measured. And a coordinate displacement measuring device, respectively, outputting from the Y-axis detecting unit.   The detection head includes eight impedance elements arranged in a frame of 3 rows and 3 columns along the X-axis and Y-axis directions, respectively, and the detection unit on one side includes a first row and a first row extending in the X-axis direction. Two impedance elements are arranged in the third row, and one detection unit on the other side is arranged in the first and third rows extending in the X-axis direction, and two in the second row. The coordinate displacement measuring device according to claim 1, wherein the coordinate displacement measuring device comprises a plurality of impedance elements.   2. The coordinate displacement of the detection head or the object to be measured is detected by correction calculation using a lookup table in addition to the X-axis component detection signal and the Y-axis component detection signal. 2. The coordinate displacement measuring device according to 2.

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