JP2004226124A - Rotation angle detection device for angle sensor - Google Patents

Abstract

An object of the present invention is to provide a rotation angle detection device for an angle sensor that can compensate for a detection error due to a temperature change or an individual difference during production.
A ring magnet (magnetic circuit component) for generating a magnetic field, first and second Hall elements (magnetic flux density detecting units) for outputting detection signals corresponding to magnetic flux densities, and the detection signals are output. In the rotation angle detecting device 10 of the angle sensor, which comprises the angle calculating means 12 for calculating the rotation angle of the ring magnet 3 with respect to the first and second Hall elements 7, 8, the amplitude detecting means for detecting the amplitude a of the detection signal 13, a correction value calculation means 14 for calculating an amplitude correction value e and an offset correction value f from the amplitude a of the detection signal, a correction means 15 for obtaining a corrected signal from the detection signal and these correction values e and f, Signal switching means 16 for switching a signal output to the angle calculation means 12 to either a detection signal or a corrected signal.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rotation angle detection device of an angle sensor that uses magnetism and is used for home electric appliances, automobiles, and the like.
[0002]
[Prior art]
Conventionally, as this type of angle sensor, a ring-shaped magnet is fixed to one end of a shaft, and a plurality of Hall elements are provided inside or outside the magnet, and this Hall element changes as the magnet rotates relatively. There is a device that outputs a voltage corresponding to the generated magnetic flux density as a signal (see Patent Document 1).
[0003]
As a method of compensating for a characteristic change due to a temperature change in this type of angle sensor, there has been a method using a temperature compensator having characteristics reverse to those of the angle sensor with respect to a temperature change (see Patent Documents 2 and 3). .
[0004]
[Patent Document 1]
Japanese Patent Application No. 2001-352683 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2-1168181 [Patent Document 2]
JP-A-48-48087
[Problems to be solved by the invention]
However, in the case of such an angle sensor using magnetism, the factors that cause a detection error are that the magnetic force of the magnet and the sensitivity of the Hall element change according to the temperature, the variation in the magnetizing strength of the magnet and the mounting of the Hall element. There is a problem at the time of production such as a variation in position, and furthermore, there is an individual difference of the Hall element itself, which causes a problem that the amplitude of the sensor output and a center value (offset value) of the amplitude of the sensor output described later change.
[0006]
In addition, in the case of a compensation method using a conventional temperature compensator, there is a problem that tuning of the temperature compensator is difficult. There is also a problem that it is difficult to cope with individual differences during production.
[0007]
The present invention has been made in view of the above problems, and has as its object to provide a rotation angle detection device for an angle sensor that can compensate for a detection error due to a temperature change or an individual difference during production.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, a magnetic circuit component for generating a magnetic field, a magnetic flux density detector for outputting a detection signal corresponding to a magnetic flux density, and a rotation angle of the magnetic circuit component with respect to the magnetic flux density detector based on the detection signal Is applied to a rotation angle detection device of an angle sensor including an angle calculation means for calculating the rotation angle.
[0009]
An amplitude detector for detecting the amplitude of the detection signal; a correction value calculator for calculating a correction value from the amplitude of the detection signal; a correction unit for obtaining a corrected signal from the detection signal and the correction value; And a signal switching means for switching the signal output to either the detection signal or the corrected signal.
[0010]
According to a second aspect, in the first aspect, a correction value is calculated based on a detection signal detected while the magnetic circuit constituting unit makes one or more rotations N with respect to the magnetic flux density detection unit, and the magnetic circuit component rotates N times. The signal output to the angle calculating means later is switched from the detection signal to the corrected signal.
[0011]
In a third aspect based on the first or second aspect, a correction value is calculated based on the detection signal every time the magnetic circuit configuration unit makes two or more rotations of the magnetic flux density detection unit with respect to the magnetic flux density detection unit, and the correction value is calculated. It is characterized in that it is configured to be updated.
[0012]
In a fourth aspect based on any one of the first to third aspects, the correction value calculation means calculates the amplitude correction value based on the amplitude and the amplitude reference value as amplitude correction value = amplitude reference value / amplitude. The offset correction value is calculated as the offset correction value = 0− (maximum value + minimum value) / 2 based on the maximum value and the minimum value of the detection signal, and the correction means is configured based on the amplitude correction value and the offset correction value. The corrected signal is calculated as a corrected signal = (detection signal + offset correction value) × amplitude correction value.
[0013]
Function and Effect of the Invention
According to the first aspect, it is possible to calculate an accurate rotation angle in which a detection error caused by a characteristic change due to a temperature change of the angle sensor or an individual difference between products is compensated based on the corrected signal. Also, unlike the conventional method, no temperature compensator is used, and there is no need for tuning.
[0014]
According to the second aspect, a correction value is calculated based on a detection signal detected while the magnetic circuit configuration unit makes N rotations with respect to the magnetic flux density detection unit, and a detection signal is calculated based on the calculated correction value. According to the third aspect of the present invention, a corrected corrected signal is calculated, and after N rotations, the output signal to the angle calculating means is switched from the detected signal to the corrected signal, and a detection error due to a temperature change or an individual difference during production is compensated. By updating the correction value every M rotations, it is possible to calculate an accurate rotation angle in which a detection error caused by a temperature change or the like after startup is compensated.
[0015]
According to the fourth aspect, the amplitude of the detection signal is detected, the amplitude correction value is calculated based on the amplitude and the amplitude reference value, and the offset correction value is calculated based on the maximum value and the minimum value of the detection signal. Then, the corrected signal is calculated based on the amplitude correction value and the offset correction value. A characteristic change due to a temperature change of the angle sensor is compensated for by the amplitude correction value, and a detection error caused by an individual difference between products is compensated for by the offset correction value, so that an accurate rotation angle can be detected.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0017]
First, FIG. 1 shows an example of an angle sensor to which the present invention is applied, which has already been filed by the present applicant as Japanese Patent Application No. 2001-352683.
[0018]
The angle sensor 1 mainly includes a ring magnet 3 fixed to a rotating shaft as a magnetic circuit component, and a pair of Hall elements 7 and 8 provided as a magnetic flux density detector.
[0019]
In the ring magnet 3 made of a permanent magnet, a pair of N and S poles are formed on the rotation center line with the rotation center O interposed therebetween by parallel magnetization.
[0020]
The first and second Hall elements 7 and 8 output a voltage corresponding to a magnetic flux density that changes as the ring magnet 3 relatively rotates. The first and second Hall elements 7, 8 are arranged on a rotation center line orthogonal to each other.
[0021]
As shown in FIG. 2, the rotation angle detecting device 10 captures the sensor signals of the first and second Hall elements 7 and 8 as detection signals by an AD converter 11 and, based on the detection signals, rotates the rotation angle Is calculated.
[0022]
FIG. 3 shows how the detection signals of the first and second Hall elements 7 and 8 change according to the rotation angle. This detection signal is a sine wave having a phase difference of 90 degrees.
[0023]
The angle calculation means 12 uses, as a signal for calculating the rotation angle, one of the detection signals having a large voltage change with respect to the rotation angle. Then, by using the detection signal having a smaller voltage change with respect to the rotation angle, it is determined in which rotation angle region the detection signal used as the signal for calculating the rotation angle is located. For example, while the second Hall element 8 makes one rotation, the same output is obtained at, for example, two points by the detection signal B, but the rotation angle is specified by monitoring the detection signal A.
[0024]
By the way, as a factor that causes a detection error of the angle sensor 1, the amplitude a of the detection signal and the center value (offset value) of the amplitude a may change due to a temperature change or an individual difference generated during production. The magnetic force of the permanent magnet weakens with increasing temperature. The individual differences of the angle sensor 1 include, for example, variations in the sensitivity of the Hall elements 7 and 8, the mounting position, the magnetization strength of the ring magnet 3, and the like.
[0025]
In response to this, the rotation angle detection device 10 calculates an amplitude correction value e based on the amplitude a of the detection signal and an offset correction value f based on the amplitude a of the detection signal. Correction value calculating means 14, a correcting means 15 for calculating a corrected signal obtained by correcting the detection signal based on these correction values e and f, and an angle calculating means 12 as the corrected signal is calculated. And a signal switching means 16 for switching the output signal to the detected signal from the detected signal to the corrected signal.
[0026]
Accordingly, the rotation angle detection device 10 compensates for a characteristic change due to a temperature change of the angle sensor 1 and a detection error caused by an individual difference of a product by the amplitude correction value e and the offset correction value f. Can be detected.
[0027]
Specifically, the amplitude detecting means 13 calculates the amplitude a as the difference between the maximum value and the minimum value of the detection signal by the following equation.
Amplitude a = maximum value-minimum value In a method of detecting the maximum value and the minimum value, first, the signal switching means 16 is set to 1 when the system is started, and the angle is calculated by the angle calculating means 12 based on the detection signal as described above. Calculate the angle value. The amplitude detecting means 13 obtains the final maximum value and minimum value by continuously updating the maximum value and the minimum value of the detection signal during one rotation of the ring magnet 3 based on the rotation angle signal from the angle calculating means 12. .
[0028]
Until the maximum value and the minimum value of the detection signal are obtained, the rotation angle is calculated based on the detection signal as before, but even if the rotation angle is not corrected, an extremely wrong value is obtained. Is not calculated, and it is not a big problem. When the angle sensor 1 is used to detect a steering angle in a power steering device of a vehicle, if a speed reducer of about 15: 1 is provided, the above-described maximum can be obtained by turning the steering wheel of the vehicle by about 24 ° after turning on the power. Since the value and the minimum value are obtained, there is almost no problem when the vehicle actually runs.
[0029]
The correction value calculating means 14 calculates the amplitude correction value e based on the amplitude a and the amplitude reference value (original amplitude) a 'by the following equation.
Amplitude correction value e = amplitude reference value a '/ amplitude a
Then, the correction value calculating means 14 calculates the offset correction value f by the following equation based on the maximum value and the minimum value of the detection signal.
Offset correction value f = 0− (maximum value + minimum value) / 2
The correction unit 15 corrects the detection signal based on the amplitude correction value e and the offset correction value f by the following equation, and calculates a corrected signal.
Corrected signal = (detection signal + offset correction value f) × amplitude correction value e
As the post-correction signal is calculated, the signal switching means 16 is set to the second side, and the output signal to the angle calculation means 12 is switched from the detection signal to the post-correction signal. Thereby, the angle calculation means 12 can calculate an accurate rotation angle in which a detection error caused by a characteristic change due to a temperature change of the angle sensor 1 or an individual difference of a product is compensated based on the corrected signal.
[0030]
Next, the above control operation executed by the rotation angle detection device 10 will be described with reference to the flowchart of FIG.
[0031]
The correction mode flag is initialized (0) when the system is started.
[0032]
In step 1, the detection signal is read, and in step 2, it is determined whether the correction mode flag is 0 or not. If the correction mode flag is 0, the process proceeds to step 3, where it is determined whether the ring magnet 3 has made one rotation.
[0033]
If the ring magnet 3 has not yet made one rotation (until it makes one rotation), the maximum and minimum values of the detection signal are detected and updated in step 4.
[0034]
On the other hand, when the ring magnet 3 makes one rotation, the correction mode flag is set to 1 (step 5), and the amplitude correction value e and the offset correction value f are set based on the maximum value and the minimum value detected earlier in step 6. calculate. When the correction values e and f are calculated in this way, a corrected signal is calculated in step 7 based on these values. If the correction mode flag is 1, the process proceeds to step 7 without performing the processing of steps 3 to 6 (step 2), and the calculated amplitude correction value e, offset correction value f, and detection signal are used. To calculate the corrected signal.
[0035]
By the way, in addition to the embodiment shown in the above-mentioned flowchart, the calculation of the correction value is not performed only once after the activation, but is performed every time the ring magnet 3 makes two or more M rotations, and the correction value is updated. Is also good. This makes it possible to calculate a more accurate rotation angle in which a detection error caused by a temperature change or the like after startup is compensated.
[0036]
Furthermore, in the above-described embodiment, one rotation is performed at the time of startup, and the maximum and minimum values are detected from the detection signal during that time, and the correction value is calculated based on the maximum and minimum values. It is also possible to rotate two or more times N to find the maximum and minimum values detected among them and calculate the correction value from the average value. As a result, a more stable value can be obtained.
[0037]
It is apparent that the present invention is not limited to the above-described embodiment, and that various changes can be made within the scope of the technical idea.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an angle sensor showing an embodiment of the present invention.
FIG. 2 is a configuration diagram of a rotation angle detection device.
FIG. 3 is a diagram showing output characteristics of the angle sensor.
FIG. 4 is a flowchart showing a control operation for compensating a detection error of the rotation angle.
[Explanation of symbols]
1 Angle sensor 2 Shaft 3 Ring magnet (magnetic circuit component)
7, 8 First and second Hall elements (magnetic flux density detector)
Reference Signs List 10 rotation angle detecting device 12 angle calculating means 13 amplitude detecting means 14 correction value calculating means 15 correcting means

Claims (4)

A magnetic circuit component for generating a magnetic field, a magnetic flux density detector for outputting a detection signal corresponding to the magnetic flux density, and an angle calculator for calculating a rotation angle of the magnetic circuit component with respect to the magnetic flux density detector based on the detection signal In a rotation angle detection device for an angle sensor comprising:
Amplitude detection means for detecting the amplitude of the detection signal; correction value calculation means for calculating a correction value from the amplitude of the detection signal; correction means for obtaining a corrected signal from the detection signal and the correction value; Signal rotation means for switching a signal output to the calculation means to either the detection signal or the corrected signal. A rotation angle detection device for an angle sensor. The correction value is calculated based on a detection signal detected while the magnetic circuit configuration unit makes one or more rotations N with respect to the magnetic flux density detection unit, and is output to the angle calculation unit after N rotations. The rotation angle detecting device for an angle sensor according to claim 1, wherein a signal is switched from the detection signal to the corrected signal. The correction value is calculated based on the detection signal and the correction value is updated every time the magnetic circuit configuration unit makes two or more rotations with respect to the magnetic flux density detection unit. A rotation angle detection device for an angle sensor according to claim 1. The correction value calculation means calculates an amplitude correction value based on the amplitude and the amplitude reference value as amplitude correction value = amplitude reference value / amplitude, and calculates an offset correction value based on a maximum value and a minimum value of the detection signal. The offset correction value is calculated as 0− (maximum value + minimum value) / 2, and the correction unit calculates the corrected signal based on the amplitude correction value and the offset correction value as a corrected signal = (detection signal + offset). 4. The rotation angle detection device for an angle sensor according to claim 1, wherein the rotation angle is calculated as (correction value) .times.amplitude correction value.

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