JP2012112711A - Rotation angle detecting device - Google Patents

Abstract

Provided is a rotation angle detection device that improves nonlinear errors and reduces linearity errors.
A hall element outputs a signal corresponding to a change in magnetic flux density caused by relative rotation with respect to a permanent magnet. The DSP 12 corrects the actual output value corresponding to the signal of the Hall element 11 and calculates and outputs the relative rotation angle between the Hall element 11 and the permanent magnet 20 based on the corrected value. The memory 13 stores data used by the DSP 12. The DSP 12 corrects the actual output value based on a predetermined value corresponding to n (n is a natural number) correction points set in advance within a predetermined range and a predetermined correction value corresponding to the predetermined value. Also, the curve representing the change rate of the difference between the predetermined values of two correction points adjacent to each other among the n correction points is a part of the sine wave curve obtained by shifting the sine wave curve corresponding to the actual output value by 180 °. Approximate.
[Selection] Figure 1

Description

  The present invention relates to a rotation angle detection device.

Conventionally, by installing one of a magnetic generation means such as a magnet and a magnetic flux density detection means such as a Hall element as a detection target, and detecting the magnetism of the magnetic generation means when the detection target rotates, the magnetic flux density detection means A rotation angle detection device that detects a rotation angle of a detection target is known.
For example, the rotation angle detection device disclosed in Patent Document 1 includes a magnet as a magnetism generation unit, a magnetic flux density sensor as a magnetic flux density detection unit, and a signal processing unit as a processing unit, and the signal processing unit performs correction calculation. Do. The signal processing unit corrects the actual output voltage based on the output signal of the magnetic flux density sensor based on a predetermined value (voltage level) corresponding to a preset correction point. Here, the various correction points set in advance are set at equal intervals.

JP 2002-206911 A

By the way, when the interval between the correction points is constant, the nonlinearity of the output signal is not improved, and the error of the actual output voltage remains as the linearity error of the rotation angle. In addition, increasing the number of correction points and reducing the interval between correction points corrects the nonlinearity of the actual output voltage. However, increasing the number of correction points leads to an increase in circuit scale and an increase in component costs. To do.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a rotation angle detection device that improves nonlinearity and reduces linearity error.

  The rotation angle detection device according to the first aspect of the present invention includes magnetism generation means, magnetism detection means, processing unit, and storage means. The magnetism detecting means outputs a signal corresponding to a change in magnetic flux density caused by relative rotation with respect to the magnetism generating means. The processing unit corrects the actual output value corresponding to the signal of the magnetic detection unit, calculates the relative rotation angle between the magnetic detection unit and the magnetic generation unit based on the corrected value, and outputs the relative rotation angle. The storage means stores data used in the processing unit.

  The processing unit corrects the actual output value based on a predetermined value corresponding to n (n is a natural number) correction points set in advance within a predetermined range and a predetermined correction value corresponding to the predetermined value. Further, a curve representing a change rate of a difference between predetermined values of two correction points adjacent to each other among n correction points is a sine wave curve obtained by shifting the phase of the sine wave curve corresponding to the actual output value by 180 °. Approximate the part.

Thereby, the rate of change of the difference between the predetermined values of two correction points adjacent to each other gradually decreases. For this reason, the correction point is set so that the difference between the predetermined values having a larger value is smaller than the difference between the predetermined values having a smaller value. Therefore, more correction points are set on the maximum value side of the actual output value than on the minimum value side of the actual output value.
By the way, the sine wave curve corresponding to the actual output value has a larger curve on the maximum value side of the actual output value than the minimum value side of the actual output value. Therefore, a large number of correction points are set on the maximum value side of the actual output value where the curve of the sine wave curve is relatively large, and the tendency of increasing non-linearity of the sine wave curve is offset. Therefore, setting the correction point in this way can improve the non-linearity with respect to the actual output value, and can effectively reduce the linearity error. Therefore, the correction accuracy of the rotation angle detection device can be improved.

According to the second aspect of the invention, the processing unit corrects the actual output value by adding or subtracting the correction value to or from the actual output value. When the actual output value matches the predetermined value of the correction point, the actual output value is corrected by substituting the predetermined correction value as the correction value.
Further, when the actual output value and the predetermined value of the correction point are different, the correction value is calculated based on two correction points closest to the actual output value and the predetermined correction value corresponding to the two correction points. The actual output value is corrected by substituting the calculated correction value.
Thereby, even if the actual output value is a value between correction points, correction can be performed.

According to the invention of claim 3, the apparatus further comprises a predetermined correction value calculating means for calculating the predetermined correction value based on the actual output value.
Thereby, by updating the predetermined correction value in the rotation angle detection device, for example, even if the positions of the magnetism generating means and the magnetic detection means are shifted, the predetermined correction can be set to an appropriate value. Therefore, the correction accuracy of the rotation angle detection device can be maintained only by the rotation angle detection device for a long time.

  According to the fourth aspect of the present invention, the actual output value output from the magnetic detection means in accordance with the change in magnetic flux density caused by the relative rotation with respect to the magnetic generation means is a sine wave curve.

The schematic diagram which shows the rotation angle detection apparatus of 1st Embodiment of this invention. The schematic diagram which shows the processing circuit of the rotation angle detection apparatus of 1st Embodiment of this invention. The figure which shows the data memorize | stored in the memory | storage means of the rotation angle detection apparatus of 1st Embodiment of this invention. The figure which shows the sine wave corresponding to the actual output value of the magnetic detection means of the rotation angle detection apparatus of 1st Embodiment of this invention. The figure which shows the sine wave which shifted the sine wave of FIG. 4 180 degrees. The figure showing the change rate of the difference of the predetermined value corresponding to the correction point of the rotation angle detection apparatus of 1st Embodiment of this invention. (A) is a figure showing the set of the value which becomes an actual output value of the magnetic detection means of the rotation angle detection apparatus of 1st Embodiment of this invention, and the ideal correction result of an actual output value, (b) is (a). The figure which expanded and showed the content in the frame b of. The figure which shows the linearity error of the detection result of the rotation angle detection apparatus of 1st Embodiment of this invention. The figure which shows the change rate of the difference of the predetermined value corresponding to the correction point of the conventional rotation angle detection apparatus. The figure which shows the linearity error of the detection result of the conventional rotation angle detection apparatus.

Hereinafter, rotation angle detection devices according to a plurality of embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
A rotation angle detection device according to a first embodiment of the present invention is shown in FIG. The rotation angle detection device 1 is a device that detects, for example, the rotation angle of a valve shaft of a throttle as a detection target. The rotation angle detection device 1 includes a permanent magnet 20, a Hall IC 10 including a Hall element 11, a digital signal processor (hereinafter referred to as DSP) 12, and a memory 13.

  The permanent magnet 20 is attached to a yoke 30 provided on the valve shaft of the throttle. Here, the permanent magnet 20 corresponds to “magnetism generating means” in the claims. The permanent magnet 20 is provided so as to be rotatable relative to the Hall IC 10 as the detection target rotates.

  The Hall element 11 is formed of a semiconductor thin film and corresponds to “magnetic detection means” in the claims. The Hall element 11 outputs a signal corresponding to a change in magnetic flux density.

  The DSP 12 specializes in digital signal processing, and performs processing such as correction processing and rotation angle calculation processing on the value output from the Hall element 11 and converted into a digital signal. The DSP 12 corresponds to a “processing unit” in the claims.

  The memory 13 includes, for example, a read-only memory and a writable / erasable memory, and stores various data used by the DSP 12. The memory 13 corresponds to “storage means” in the claims.

  In the present embodiment, as shown in FIG. 2, the Hall IC 10 includes, in addition to the Hall element 11, the DSP 12, and the memory 13, an analog-digital conversion circuit (hereinafter referred to as ADC) 14, and a digital-analog conversion circuit. (Hereinafter referred to as DAC) 15 or the like. The Hall IC 10 is provided such that the magnetosensitive surface of the Hall element 11 is positioned on the central axis O (see FIG. 1).

Next, the operation of the rotation angle detection device 1 will be described.
The Hall element 11 outputs a signal corresponding to a change in magnetic flux density caused by relative rotation around the central axis O with respect to the permanent magnet 20. The ADC 14 converts an analog value output from the Hall element 11 into a digital value and transmits the digital value to the DSP 12. Hereinafter, the digital value converted by the ADC 14 is simply referred to as an actual output value. The DSP 12 performs correction processing, rotation angle calculation processing, and the like on the output value from the Hall element 11. Further, the DSP 12 transmits the processing result to the DAC 15. The DAC 15 converts the digital value transmitted from the DSP 12 into an analog value and outputs the analog value.

Here, the correction processing by the DSP 12 will be described in detail.
In the case of the present embodiment, for example, 16 correction points are set in advance, and the actual output value is corrected based on a predetermined value corresponding to the 16 correction points. The memory 13 stores predetermined values A (0) to A (15) and predetermined correction values K (0) to K (15) corresponding to the respective correction points. As shown in FIG. 3, predetermined values A (0) to A (15) and predetermined correction values K (0) to K (15) are associated with each other. The predetermined values A (0) to A (15) are all values within the range of the actual output value (voltage level) of the Hall element 11. Here, the “predetermined range” in the claims corresponds to the range of the actual output value of the Hall element 11.

The DSP 12 corrects the actual output value of the Hall element 11 based on the predetermined values A (0) to A (15) and the predetermined correction values K (0) to K (15).
When the actual output value matches any one of the predetermined values A (0) to A (15), a predetermined correction value corresponding to the predetermined value that matches the actual output value is subtracted from the actual output value. Correct the actual output value. For example, when the actual output value matches A (3), the predetermined correction value corresponding to A (3) is K (3) as shown in FIG. It is corrected as K (3).

When the actual output value is different from any of the predetermined values A (0) to A (15), the actual output value is corrected by subtracting the operation correction value corresponding to the actual output value from the actual output value. Calculation correction value K
Is calculated by performing primary interpolation according to the following equation (2) using two predetermined values between the actual output values and predetermined correction values corresponding to the two predetermined values.
{K (n) -K (n-1)} / {A (n) -A (n-1)} = {KK (n-1)} / {A-A (n-1)} ..Formula 1
K = {K (n) -K (n-1)} / {A (n) -A (n-1)} * {AA (n-1)} + K (n-1) Expression 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 calculation correction value corresponding to the actual output value A is K. Here, when the actual output value A, the predetermined value A (3), the predetermined value A (4), the predetermined correction value K (3), and the predetermined correction value K (4) are substituted into Expression 1, Expression 3 is obtained. .
{K (4) -K (3)} / {A (4) -A (3)} = {KK (3)} / {AA (3)} Expression 3
The following formula 4 is obtained by the formula 3.
K = [{K (4) −K (3)} / {A (4) −A (3)}] × {AA− (3)} + K (3) Equation 4
Further, since the actual output value is corrected to AK, the actual output value is corrected to a calculated value according to the following equation 5.
A-[{K (4) -K (3)} / {A (4) -A (3)}] × {AA (3)}-K (3) Formula 5
In this way, the DSP 12 corrects the actual output value by subtracting the calculation correction value calculated by the primary interpolation process from the actual output value, and calculates the rotation angle.

Hereinafter, the setting of the correction point and the calculation of the predetermined correction value will be described in detail.
In the present embodiment, a predetermined value and a predetermined correction value corresponding to the correction point are calculated using an external computer.
First, the actual output value output from the hall element 11 is acquired for each rotation angle of the throttle. Then, a sine wave corresponding to the actual output value of the Hall element 11 is acquired using the rotation angle of the throttle and the actual output value acquired for each rotation angle of the throttle.

In the case of this embodiment, since the Hall element 11 is provided on the central axis O, for example, when the permanent magnet 20 rotates 360 ° around the Hall IC 10, a sine wave corresponding to the actual output value of the Hall element 11 is The sine wave 100 shown in FIG.
In the present embodiment, the detection target is the valve shaft of the electronic throttle, and the operating angle range is, for example, −10 ° to 80 °. Here, the positional relationship between the permanent magnet 20 and the Hall IC 10 is set in advance so that the actual output value of the Hall element 11 becomes 0 when the rotation angle is −10 ° (see FIG. 7A). . In the case of this embodiment, the rotation angle detection device is used within a range of −10 to 80 °. Therefore, the output of the Hall element 11 corresponds to the curve 101 in FIG.

  When the phase of the sine wave 100 shown in FIG. 4 is shifted by 180 ° along the rotation angle axis, a sine wave 200 as shown in FIG. 5 is obtained. Here, a curve within a range of −10 ° to 80 ° of the sine wave 200 is defined as a curve 201.

  A curve 301 that approximately matches the shape of the curve 201 is shown in FIG. As shown in FIG. 6, numbers M1 to M15 are set at equal intervals on the horizontal axis. Numbers M1 to M15 are numbers corresponding to a difference between predetermined values corresponding to two correction points adjacent to each other. In the present embodiment, the number M1 corresponds to the difference between the predetermined value A (1) and the predetermined value A (0), and the number M2 corresponds to the difference between the predetermined value A (2) and the predetermined value A (1). The number M15 corresponds to the difference between the predetermined value A (15) and the predetermined value A (14). On the curve 301, points Z1 to Z15 corresponding to the numbers M1 to M15 are set. The points Z1 to Z15 are set so that the point Z1 having the largest coordinate value on the vertical axis corresponds to the number M1, and the point Z15 having the smallest coordinate value on the vertical axis corresponds to the number M15. Here, the coordinate value of the vertical axis of the point Z1 is 1, and the coordinate value of the vertical axis Z15 is set to a value close to 0.

In the present embodiment, the coordinate values of the vertical axes of the points Z1 to Z15 on the curve 301 represent the rate of change of the difference between the predetermined values of two correction points adjacent to each other. For example, the coordinate value of the vertical axis of the point Z1 is a ratio between the difference between the predetermined value A (1) and the predetermined value A (0) and the predetermined value A (1). The coordinate value of the vertical axis of the point Z2 is a ratio between the difference between the predetermined value A (2) and the predetermined value A (1) and the predetermined value A (1). Thus, “the rate of change of the difference between the predetermined values of two correction points adjacent to each other” refers to the ratio of the difference between the predetermined values of the two adjacent correction points to the predetermined value A (1). In the case of this embodiment, when 0 is a predetermined value A (0) and the relative rotation angle between the permanent magnet 20 and the Hall IC 10 is 0 °, the actual output value of the Hall element 11 is a predetermined value A (1). .
The predetermined values A (1) and the rate of change of the vertical axis of the points Z1 to Z15 are assigned to the output coordinate axis to calculate the predetermined values A (2) to A (15), and these predetermined values A (0) to A Correction points corresponding to (15) are respectively set. Also, predetermined values A (0) to A (15) corresponding to the correction points are written into the memory.

FIG. 7A is an enlarged view of the curve 101. As shown in FIG. 7A, a straight line 102 is obtained by connecting points P0 and P15 at both ends of the curve 101 with a straight line. A straight line 102 is a straight line corresponding to an ideal correction result of the actual output value. The coordinate values of the output value axes of the points P0 to P15 on the curve 101 coincide with the predetermined values A (0) to A (15). Here, the “correction point” in the claims corresponds to the points P0 to P15. Points P16 to P29 and points P1 to P14 on the straight line 102 have the same rotation angle. Here, the difference between the coordinate value of the output value axis of the points P1 to P14 and the coordinate value of the output value axis of the points P16 to P29 is a predetermined correction value K corresponding to the predetermined values A (1) to A (14). It corresponds to (1) to K (14). In the present embodiment, the curve 101 and the straight line 102 are a point P0 where the coordinate value of the output value axis is A (0), and a point P15 where the coordinate value of the output value axis is A (15). Overlap. Therefore, the predetermined correction value K (0) corresponding to the predetermined value A (0) and the correction value K (15) corresponding to the predetermined value A (15) are 0.
The predetermined correction values K (0) to K (15) are written in the memory 13 in association with the predetermined values A (0) to A (15).

  As described above, in the present embodiment, the curve 301 representing the change rate of the difference between the predetermined values of two correction points adjacent to each other is a sine wave obtained by shifting the sine wave 100 corresponding to the actual output value by 180 °. It almost coincides with the curve 201 in the range of 200 −10 ° to 80 °. Thereby, the rate of change of the difference between the predetermined values of two correction points adjacent to each other gradually decreases. For this reason, the predetermined values A (0) to A (15) are set so that the difference between the predetermined values having a larger value is smaller than the difference between the predetermined values having a small value. Therefore, more predetermined values are set on the maximum value side of the actual output value than on the minimum value side of the actual output value.

  Incidentally, the curve 101 corresponding to the actual output value which is a sine wave curve has a larger curve on the maximum value side of the actual output value than the minimum value side of the actual output value. Therefore, a large number of correction points are set on the maximum value side of the actual output value where the curve 101 is relatively large, and the tendency of the nonlinearity of the curve 101 to increase is offset. In particular, the actual output value that is a sine wave curve is set by assigning the change rate of the difference between the predetermined values of two correction points adjacent to each other to the output axis so as to correspond to the sine wave curve of the actual output value. It is possible to improve the non-linearity with respect to and to effectively reduce the linearity error. Therefore, the correction accuracy for the actual output value can be improved.

  As shown in FIG. 7B, the point P is a point on the curve 101, and the point PL is a point on the straight line 102. Here, the coordinate value of the output axis of the point P is A, and the coordinate value of the output axis of the point PH is Equation 5. That is, the coordinate value of the output axis of the point PH is a value obtained by performing the primary interpolation process on the coordinate value of the output axis of the point P. As shown in FIG. 7B, the point PH and the point PL substantially overlap. Thus, based on the predetermined values A (0) to A (15) corresponding to the correction points of the present embodiment, the non-linearity can be corrected so as to be reduced with respect to the actual output value of the rotation angle detection device 1. it can.

  In FIG. 8, the actual output value is corrected using the predetermined values A (0) to A (15) and the predetermined correction values K (0) to K (15) corresponding to the correction points of the present embodiment, and the rotation angle is set. The linearity error when calculating is shown. As shown in FIG. 8, in the case of the present embodiment, the linearity error is suppressed within ± 0.2%, and is suppressed within 0.1% below 70 °. FIG. 9 shows the change rate of the difference between the predetermined values of the conventional correction points set at equal intervals. FIG. 10 shows the linearity error of the conventional rotation angle detection device 1 in which the correction points are set at equal intervals. Here, when FIG. 8 and FIG. 10 are compared, it can be seen that the rotation angle detection device 1 of the present embodiment has a higher effect of suppressing the linearity error than the conventional rotation angle detection device.

(Second Embodiment)
A rotation angle detection device according to a second embodiment of the present invention will be described.
In the present embodiment, a program for calculating predetermined correction values K (0) to K (15) is written in the memory 13. A microcomputer is installed in place of the DSP of the first embodiment, and the predetermined correction value can be updated when necessary by a program written in the memory.

  Thereby, for example, when a preset relative positional relationship between the permanent magnet 20 and the Hall element 11 is deviated, an error can be suppressed by calculating a new predetermined correction value corresponding to the new relative positional relationship. Therefore, high correction accuracy of the rotation angle detection device can be maintained for a long time.

(Other embodiments)
In the first embodiment, the DSP performs the correction calculation. However, a microcomputer may be installed in place of the DSP, and a correction calculation or the like stored in the memory may be read and corrected by the microcomputer.
In the above embodiment, the change rate of the difference between the predetermined values of the two adjacent correction points is defined as the ratio between the predetermined value difference between the two adjacent correction points and the predetermined value A (1). . On the other hand, in another embodiment, the change rate of the difference between the predetermined values of two correction points adjacent to each other is, for example, the predetermined value of the (n + 1) th correction point and the nth correction out of n correction points. A configuration may be defined in which a difference between a predetermined value of the point and a ratio between a predetermined value of the nth correction point and a predetermined value of the (n−1) th correction point is defined.
In the above embodiment, 16 correction points are set, and 16 predetermined values are stored in the memory. On the other hand, in other embodiments, the number of correction points and predetermined values may be increased or decreased.
In the above embodiment, when the actual output value matches any one of the predetermined values A (0) to A (15), the predetermined correction value corresponding to the predetermined value that matches the actual output value is output as the actual output value. Although the actual output value is corrected by subtracting from the value, the sign of the correction value K stored in the memory is set to minus when the use range of the sine wave curve as the actual output value is expanded to a negative angle. In such a case, the actual output value may be corrected by adding the correction value.
In the above embodiment, the minimum value of the change rate of the correction point is set to a value close to zero. On the other hand, in another embodiment, the minimum value of the change rate of the correction point may be set to 0.
The present invention described above is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1 ... Magnetic detection apparatus 11 ... Hall element (magnetic detection means)
12 ... DSP (Processor)
13 ... Memory (storage means)
20 ... Permanent magnet (magnetic generation means)

Claims (4)

Magnetism generating means;
A magnetic detection means for outputting a signal corresponding to a change in magnetic flux density caused by relative rotation with respect to the magnetic generation means;
A processing unit that corrects an actual output value corresponding to the signal of the magnetic detection unit, calculates and outputs a relative rotation angle between the magnetic detection unit and the magnetic generation unit based on the corrected value;
Storage means for storing various programs and data used in the processing unit;
With
The processing unit corrects the actual output value based on a predetermined value corresponding to n (n is a natural number) correction points set in advance within a predetermined range and a predetermined correction value corresponding to the predetermined value. ,
The curve representing the change rate of the difference between the two predetermined correction points among the n correction points is a sine wave curve obtained by shifting the phase of the sine wave curve corresponding to the actual output value by 180 °. A rotation angle detection device that approximates a part of the rotation angle. The processing unit corrects the actual output value by adding or subtracting a correction value to the actual output value,
When the actual output value matches the predetermined value, the predetermined correction value is substituted as the correction value to correct the actual output value,
When the actual output value is different from the predetermined value, the correction value is calculated based on the two predetermined values closest to the actual output value and the predetermined correction value corresponding to the two predetermined values. The rotation angle detection device according to claim 1, wherein the actual output value is corrected by substituting the calculated correction value.   The rotation angle detection device according to claim 1, further comprising a predetermined correction value calculation unit that calculates the predetermined correction value based on the actual output value.   4. The actual output value output from the magnetism detecting means in accordance with a change in magnetic flux density caused by relative rotation with respect to the magnetism generating means is a sinusoidal curve. The rotation angle detection device according to claim 1.

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