JP2019078547A - Position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detecting device capable of calculating a correction value with a small number of calculations while keeping a small storage area and improving output accuracy. A position detecting device includes a Hall element 13 that outputs a signal corresponding to a position relative to a magnetic generating unit and a magnetic generating unit, a memory 15 that stores a correction value and various values used when calculating the correction value, and the like. It includes a DSP 14 that calculates a correction value, corrects an actual output value based on the output signal of the Hall element 13 with the correction value, and calculates a relative rotation angle of the magnetic generating portion based on the corrected value. The DSP 14 calculates a primary difference, which is the difference between the actual output value and the ideal output value, and sets the primary difference at n preset correction points within a predetermined measurement range as a temporary correction value for interpolation processing. To carry out. Further, the DSP 14 calculates the quadratic difference which is the difference between the output value after the interpolation processing and the ideal output value, and finely adjusts and corrects the tentative correction values corresponding to the n correction points based on the quadratic difference. Let it be a value. [Selection diagram] Fig. 3

Description

  The present invention relates to a position detection device.

  BACKGROUND Conventionally, there has been known a position detection device which calculates a relative position by correcting an actual output value based on an output signal of a signal output unit such as a Hall element with a correction value. The correction value is preset. The position detection device disclosed in Patent Document 1 performs a series of processes for setting the maximum absolute value of the error amount between the output value after the linear function interpolation and the ideal output value as a correction value, and correcting them. The above process is repeated until the amount of error falls below a predetermined value. In this way, Patent Document 1 aims to improve the output accuracy with a few correction points by setting correction points in order from a part where the amount of error is large.

JP, 2013-19829, A

  According to Patent Document 1, while repeating the series of processes, it is necessary to sequentially store an error amount, a position at which the absolute value of the error amount is maximum, and a correction value set based on the error amount at that position. Therefore, it is necessary to prepare a certain storage area regardless of the necessity. Moreover, in patent document 1, it is necessary to calculate the output value after correction | amendment whenever it repeats the said series of processes. Therefore, the number of operations increases. A large number of operations leads to circuit enlargement and an increase in the number of manufacturing processes.

  The present invention has been made in view of the above-described point, and an object thereof is to provide a position detection device capable of calculating a correction value with a small number of operations with a small storage area and improving output accuracy. It is.

  The position detection device of the present invention comprises a magnetism generation unit (11), a signal output unit (13) that outputs a signal according to the relative position of the magnetism generation unit, and a correction value calculation unit (14) that calculates a correction value. 21) a storage unit (15) for storing a correction value and various values used when calculating the correction value, and a correction unit (14) for correcting an actual output value based on an output signal of the signal output unit with the correction value And a position calculation unit (14) that calculates the relative position of the magnetism generation unit with respect to the signal output unit based on the value corrected by the correction unit.

  The correction value calculation unit calculates a primary difference which is a difference between an actual output value and an ideal output value, and sets primary differences at n correction points set in advance within a predetermined measurement range as temporary correction values. To perform interpolation processing. In addition, the correction value calculation unit calculates a secondary difference which is a difference between the output value after interpolation processing and the ideal output value, and finely adjusts temporary correction values corresponding to n correction points based on the secondary difference. And set it as a correction value.

  Since the provisional correction value is finely adjusted only once based on the secondary difference instead of repeating setting of a new correction point based on the secondary difference as in the past, calculation is performed while keeping the storage area small Is possible. Further, since the calculation is completed in the procedure of finely adjusting the temporary correction value set based on the primary difference based on the secondary difference, the number of calculations is small. Therefore, it is possible to improve the output accuracy by calculating the correction value with a small number of operations while keeping the storage area small.

It is a figure explaining the position detection device by a 1st embodiment. It is a figure when the position detection apparatus of FIG. 1 is seen from the arrow II direction. It is a block diagram which shows the structure of a position detection apparatus. It is a flowchart explaining the process in which a position detection apparatus calculates a correction value. It is a figure which shows the relationship of the actual output value and angle value which a position detection apparatus measures. It is a figure which shows the relationship of the difference and angle value which a position detection apparatus calculates. It is a figure which shows a part of secondary difference which a position detection apparatus calculates. It is a figure which shows another part of the secondary difference which a position detection apparatus calculates. It is a block diagram which shows the structure of the position detection apparatus by 2nd Embodiment. It is a figure explaining the position detection apparatus by 2nd Embodiment. It is a figure when the position detection apparatus of FIG. 10 is seen from the arrow XI direction. It is a figure explaining the position detection apparatus by 3rd Embodiment. It is a figure when the position detection apparatus of FIG. 12 is seen from the arrow XIII direction.

  Hereinafter, a plurality of embodiments will be described based on the drawings. The same reference numerals are given to substantially the same configuration in the plurality of embodiments and the description will be omitted.

First Embodiment
The position detection device according to the first embodiment is shown in FIG. 1 and FIG. The position detection device 10 is a rotation angle detection device that detects the relative rotation angle of the detection target member 6 with respect to the reference member 5. The position detection device 10 includes a magnetism generation unit 11 and a Hall IC 12. The Hall IC 12 includes a Hall element 13, a digital signal processor (hereinafter DSP) 14 and a memory 15.

  The magnetism generation unit 11 is fixed to the detection target member 6 and has two yokes 16 and two magnets 17. One magnet 17 is provided between one end of each yoke 16. The other magnet 17 is provided between the other ends of the respective yokes 16. The two yokes 16 and the two magnets 17 form a closed magnetic circuit. The reference groove 8 formed at one end of the rotation shaft portion 7 of the detection target member 6 is used to be fitted with the measuring instrument and to match the reference of the angle of the detection target member 6 and the angle of the measuring instrument.

  The Hall IC 12 is fixed to the reference member 5 and disposed inside the closed magnetic circuit of the magnetic generation unit 11, that is, between the two yokes 16. The magnetism generation unit 11 is rotatable relative to the Hall IC 12 together with the detection target member 6.

  The Hall element 13 is a signal output unit that outputs a signal according to the relative position to the magnetism generation unit 11. The DSP 14 is specialized for digital signal processing, and performs processing such as correction processing and position calculation processing on the values output from the Hall element 13 and converted into digital signals. The DSP 14 is a correction unit and a position calculation unit. The memory 15 is a storage unit including, for example, a read only memory and a writable and erasable memory, and stores various data used by the DSP 14. The memory 15 stores a correction value corresponding to the rotation angle of the detection target member 6.

  As shown in FIG. 3, the Hall IC 12 includes, in addition to the Hall element 13, the DSP 14 and the memory 15, an analog-digital conversion circuit (hereinafter, ADC) 18 and a digital-analog conversion circuit (hereinafter, DAC) 19 and the like. It is an IC chip that contains

  Next, the operation of the position detection device 10 will be described. The Hall element 13 outputs a signal according to the change of the magnetic flux density generated by the relative rotation of the magnetic generation unit 11 with respect to the Hall element 13 around the central axis AX. The ADC 18 converts an analog value output from the Hall element 13 into a digital value, and outputs the digital value to the DSP 14. Hereinafter, the digital value converted by the ADC 18 is simply referred to as an actual output value. The DSP 14 performs correction processing, position calculation processing, and the like on the actual output value, and outputs the processing result to the DAC 19. The DAC 19 converts the digital value output from the DSP 14 into an analog value and outputs it.

  The correction processing by the DSP 14 will be described. In the case of the present embodiment, n correction points are set in advance within a predetermined measurement range corresponding to the rotatable angle range of the detected member 6, and the actual output value is based on the correction values corresponding to the n correction points. Is corrected. The memory 15 stores predetermined values A (1) to A (n) and correction values c (1) to c (n) corresponding to the respective correction points. The predetermined values A (1) to A (n) are all within the range of the actual output value based on the output signal of the Hall element 13.

  When the actual output value matches one of the predetermined values A (1) to A (n), the actual output value is corrected by subtracting the correction value corresponding to the matching predetermined value from the actual output value. Be done. For example, if the actual output value matches A (3), the correction value corresponding to A (3) is c (3), so the actual output value is corrected to A (3) -c (3) .

When the actual output value is different from any of the predetermined values A (1) to A (n), the actual output value is corrected by subtracting the operation correction value corresponding to the actual output value from the actual output value. The arithmetic correction value c is to be subjected to linear interpolation according to the equation 2 derived by the following equation 1 using the two predetermined values taking the actual output value and the correction values corresponding to the two predetermined values. Calculated by
{C (n) -c (n-1)} / {A (n) -A (n-1)} = {c-c (n-1)} / {A-A (n-1)}. .. Formula 1
c = {c (n) -c (n-1)} / {A (n) -A (n-1)} * {A-A (n-1)} + c (n-1) .. Formula 2

For example, when the actual output value is a value A between the predetermined value A (3) and the predetermined value A (4), the operation correction value corresponding to the actual output value A is c. Here, when the actual output value A, the predetermined value A (3), the predetermined value A (4), the correction value c (3), and the correction value c (4) are substituted into Expression 1, Expression 3 is obtained. And Formula 4 is obtained by Formula 3. Further, since the actual output value is corrected to A-c, the actual output value is corrected to the calculated value by equation 5. Thus, the DSP 14 corrects the actual output value by subtracting the operation correction value calculated by the linear function interpolation processing from the actual output value.
{C (4) -c (3)} / {A (4) -A (3)} = {c-c (3)} / {A-A (3)} Formula 3
c = [{c (4) -c (3)} / {A (4) -A (3)}] × {A-A (3)} + c (3) formula 4
A-[{c (4) -c (3)} / {A (4) -A (3)}] × {A-A (3)}-c (3) Formula 5

  Next, the setting of the correction value will be described with reference to FIGS. In the present embodiment, the DSP 14 is a correction value calculation unit. The DSP 14 calculates the correction value based on the process flowchart shown in FIG.

  In S101 of FIG. 4, an angle value Angle (m) and an actual output value V (m) corresponding to the rotation angle of the detection target member 6 within a predetermined measurement range are measured. An example of the relationship between the measured angle value Angle (m) and the actual output value V (m) is shown by a curve S1 in FIG. In FIG. 5, the angle value range θb1 is a range corresponding to a predetermined measurement range. The angle value Angle (m) and the actual output value V (m) are stored in the memory 15. After S101, the process proceeds to S102.

  In S102, an ideal output value VR (m) is calculated based on the measured actual output value V (m). In the case of this embodiment, the ideal output value VR (m) passes through the coordinates (0, 0) at which the angle value Angle (m) and the actual output value V (m) are 0 respectively, and the inclination is the ideal inclination. It is a value on a straight line. An example of the relationship between the angle value Angle (m) and the ideal output value VR (m) is shown by a straight line S2 in FIG. The ideal output value VR (m) is stored in the memory 15. After S102, the process proceeds to S103.

  In S103, a primary difference is calculated. The primary difference is the difference {V (m) −VR (m)} between the actual output value V (m) and the ideal output value VR (m). An example of the relationship between the angle value Angle (m) and the primary difference is shown by a curve S3 in FIG. After S103, the process proceeds to S104.

  In S104, the primary differences at n correction points set in advance within the predetermined measurement range are set to a temporary correction value ct (n). As shown in FIG. 5, the n correction points are equally arranged with respect to the actual output value V (m). After S104, the process proceeds to S105.

  In S105, an output value VC (m) (hereinafter, an output value after interpolation) subjected to linear function interpolation processing using the temporary correction value ct (n) is calculated. The interpolated output value VC (m) is stored in the memory 15. After S105, the process proceeds to S106.

  At S106, a secondary difference is calculated. The secondary difference is the difference {VC (m) −VR (m)} between the interpolated output value VC (m) and the ideal output value VR (m). The relationship between the angle value Angle (m) within a predetermined measurement range and the second-order difference is shown by a curve S4 in FIG. After S106, the process proceeds to S107.

  In S107, the count value k of the correction point counter is set to 2. After S107, the process proceeds to S108.

  In S108, the secondary difference Y1 at the position where the absolute value of the secondary difference is maximum between the k-th correction point and the (k-1) -th correction point, the k-th correction point and the (k + 1) -th correction point The secondary difference Y2 is calculated at the position where the absolute value of the secondary difference is maximum between the correction point of. The secondary differences Y1 and Y2 are stored in the memory 15. After S108, the process proceeds to S109.

  In S109, it is determined whether or not {(Y1 × Y2) ≧ 0}. That is, it is determined whether the signs of the secondary difference Y1 and the secondary difference Y2 are the same. FIG. 7 shows the case of {(Y1 × Y2) ≧ 0}. In this case (S109: YES), the process proceeds to S110. On the other hand, FIG. 8 shows the case of {(Y1 × Y2) <0}. In this case (S109: NO), the process proceeds to S113.

  In S110, it is determined whether (Y1 ≧ Y2). If (Y1 ≧ Y2) (S110: YES), the process proceeds to S111. On the other hand, if (Y1 <Y2) (S110: NO), the process proceeds to S112. FIG. 7 shows the case of (Y1 <Y2).

At S111, the temporary correction value ct (k) corresponding to the kth correction point is finely adjusted based on the secondary difference to obtain a correction value c (k). Specifically, the correction value c (k) is calculated from Expression 6. That is, half of the second-order difference Y1 having a large absolute value is set as the fine adjustment amount. After S111, the process proceeds to S114.
c (k) = ct (k) + Y1 / 2 equation 6

At S112, the temporary correction value ct (k) corresponding to the kth correction point is finely adjusted based on the secondary difference to obtain a correction value c (k). Specifically, the correction value c (k) is calculated from Expression 7. That is, half of the second-order difference Y2 having a large absolute value is set as the fine adjustment amount. After S112, the process proceeds to S114.
c (k) = ct (k) + Y 2/2 Equation 7

At S113, the temporary correction value ct (k) corresponding to the kth correction point is finely adjusted based on the secondary difference to obtain a correction value c (k). Specifically, the correction value c (k) is calculated from Expression 8. That is, half of the sum of the secondary difference Y1 and the secondary difference Y2 is set as the fine adjustment amount. After S113, the process proceeds to S114.
c (k) = ct (k) + (Y1 + Y2) / 2 Equation 8

  In S114, the count value k of the correction point counter is counted up (that is, +1). After S114, the process proceeds to S115.

  In S115, it is determined whether the count value k is n-1. If the count value k is n-1 (S115: YES), the process ends. On the other hand, if the count value k is not n-1, that is, if the count value k is smaller than n-1 (S115: NO), the process proceeds to S108.

  The relationship between the angle value Angle (m) within the predetermined measurement range and the final difference is shown by a curve S5 in FIG. The final difference is the difference {VC2 (m) −VR (m)} between the ideal output value VR (m) and the output value VC2 (m) subjected to linear function interpolation processing by the correction value c (n) after fine adjustment is there. The DSP 14 does not calculate the final difference.

(effect)
As described above, the position detection device 10 outputs the Hall element 13 that outputs a signal according to the relative position of the magnetism generation unit 11 and the magnetism generation unit 11, and various correction values and various correction values used in calculation of the correction values. Memory 15 for storing a value, a correction value is calculated, an actual output value based on an output signal of the Hall element 13 is corrected with the correction value, and a relative rotation angle of the magnetism generating portion 11 with respect to the Hall element 13 based on the corrected value. And a DSP 14 for calculating.

  The DSP 14 calculates a primary difference which is a difference between an actual output value and an ideal output value, sets primary differences at n correction points set in advance within a predetermined measurement range as a temporary correction value, and performs interpolation processing Conduct. Further, the DSP 14 calculates a secondary difference which is a difference between the output value after the interpolation processing and the ideal output value, and finely adjusts a provisional correction value corresponding to n correction points based on the secondary difference to correct It will be a value.

  Since the provisional correction value is finely adjusted only once based on the secondary difference instead of repeating setting of a new correction point based on the secondary difference as in the past, calculation is performed while keeping the storage area small Is possible. Further, since the calculation is completed in the procedure of finely adjusting the temporary correction value set based on the primary difference based on the secondary difference, the number of calculations is small. Therefore, it is possible to improve the output accuracy by calculating the correction value with a small number of operations while keeping the storage area small.

  Further, in the first embodiment, the n correction points are equally arranged with respect to the actual output value. Therefore, if the actual output values at both ends of the predetermined measurement range are known, it is not necessary to store other points.

  In the first embodiment, when {(Y1 × Y2) ≧ 0}, the DSP 14 calculates the fine adjustment amount of the k-th correction point with 1⁄2 of the larger one of the absolute values of Y1 and Y2. Do. Further, when {(Y1 × Y2) <0}, the DSP 14 sets (Y1 + Y2) / 2 as the fine adjustment amount of the k-th correction point. According to this, it is possible to effectively correct the difference between the actual output value and the ideal output value to be small by finely adjusting the temporary correction value by the simple calculation means. Therefore, the output accuracy can be easily improved.

Second Embodiment
In the second embodiment, as shown in FIG. 9, a computer 21 is provided outside the Hall IC 12. The computer 21 functions as a correction calculation unit, calculates correction values c (1) to c (n), and stores the correction values in the memory 15. Thus, a correction calculation unit may be provided outside the Hall IC 12.

Third Embodiment
In the third embodiment, as shown in FIGS. 10 and 11, the magnetism generating unit 31 of the position detection device 30 is rotatable relative to the Hall IC 12 about the central axis AX. The two yokes 32 of the magnetism generation unit 31 are provided to face each other in the direction parallel to the central axis AX. The Hall IC 12 is provided inside the closed magnetic circuit formed by the two yokes 32 and the two magnets 33. The position detection device 30 detects the relative rotation angle of the magnetism generation unit 31 with respect to the Hall IC 12. Such a magnetism generation part 31 may be provided. Nevertheless, since the Hall IC 12 has the same configuration as that of the first embodiment, the same effect as that of the first embodiment can be obtained.

Fourth Embodiment
In the fourth embodiment, as shown in FIG. 12 and FIG. 13, the magnetism generating unit 41 of the position detection device 40 is movable relative to the Hall IC 12 in the linear direction. The two yokes 42 of the magnetism generation part 41 are provided to face in the direction orthogonal to the movement direction. The Hall IC 12 is provided inside the closed magnetic circuit formed by the two yokes 42 and the two magnets 43. The position detection device 40 detects the relative stroke amount of the magnetism generation unit 41 with respect to the Hall IC 12. Such a magnetism generation part 41 may be provided. Nevertheless, since the Hall IC 12 has the same configuration as that of the first embodiment, the same effect as that of the first embodiment can be obtained.

[Other embodiments]
In another embodiment, the signal output unit is not limited to the Hall element but may be another configuration such as a magnetoresistive element. In short, any signal may be output as long as the signal corresponds to the relative position with the magnetism generation unit.

  The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the scope of the invention.

10, 30, 40 · · · Position detection device 11, 31, 41 · · · Magnetic generation unit 13 · · · Hall element (signal output unit)
14: Digital signal processor (DSP, correction value calculation unit, correction unit, position calculation unit)
15 ・ ・ ・ Memory (storage unit)
21: Computer (correction value calculation unit)

Claims (4)

Magnetism generating parts (11, 31, 41),
A signal output unit (13) for outputting a signal according to the relative position to the magnetism generation unit;
A correction value calculation unit (14, 21) that calculates a correction value;
A storage unit (15) for storing the correction value and various values used when calculating the correction value;
A correction unit (14) for correcting an actual output value based on an output signal of the signal output unit with the correction value;
A position calculation unit (14) that calculates the relative position of the magnetism generation unit with respect to the signal output unit based on the value corrected by the correction unit;
Equipped with
The correction value calculation unit
Calculating a primary difference which is a difference between the actual output value and the ideal output value;
Interpolation processing is performed by setting the primary differences at n correction points set in advance within a predetermined measurement range as temporary correction values,
Calculating a secondary difference which is a difference between the output value after the interpolation process and the ideal output value;
A position detection device, wherein the temporary correction value corresponding to the n correction points is finely adjusted based on the secondary difference to obtain the correction value.   The position detection device according to claim 1, wherein the n correction points are evenly arranged with respect to the actual output value. The correction value calculation unit
The secondary difference at a position where the absolute value of the secondary difference is maximum between the k-th correction point and the (k-1) -th correction point is Y1;
Assuming that the secondary difference at a position where the absolute value of the secondary difference is maximum between the k-th correction point and the (k + 1) -th correction point is Y 2:
When {(Y1 × Y2) ≧ 0}, 1⁄2 of the larger one of the absolute values of Y1 and Y2 is set as the fine adjustment amount of the k-th correction point,
The position detection device according to claim 1, wherein (Y1 + Y2) / 2 is set as a fine adjustment amount of the k-th correction point when {(Y1 × Y2) <0}.   The position detection device according to any one of claims 1 to 3, wherein the relative position calculated by the position calculation unit is a relative rotation angle or a relative stroke amount.

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