JP2001296142A - Rotating position detector and rotating speed detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detector which can improve resolution and accuracy by reducing required steps in the phase adjustment and shortening the arithmetic processing time. SOLUTION: The rotating position detector has a position detector to detect position using an orthogonal two-phase signal and is provided with means 21 and 22, to convert analog signals of two phases outputted from the position detector into digital signals and a means 3 which removes offset errors in each phase, by equalizing the amplitude in the respective phases of the digital signals of two phases and performs an arithmetic processing for adjusting the difference between the phases to 90 deg.. A means is provided to compute the sum of and the difference between the signals of the respective phases, after the removal of the offset between the phases with the amplitude equalized in the phases of the position detector, and adjusts the phase difference between the respective phases to 90 deg., using the two signals generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation position detector and a rotation speed detection device for detecting a rotation position of a rotating body such as a motor used for an industrial robot, an NC machine tool or the like.

[0002]

2. Description of the Related Art A rotational position detecting technique is widely used in various fields and applications. There are various detection principles such as a magnetic type and an optical type. In particular, a magnetic position detector that generates a two-phase signal having orthogonality by rotation (Japanese Patent Application No. 10-034050).
Has a battery-less absolute position and has a simple structure, so its application range is wide. As a signal processing method of the rotational position detector, a method of interpolating sine waves (A-phase and B-phase) generated by the detector and having different phases by 90 degrees is used. However, it is difficult to make the output from the detector an ideal state without error, and the difference between the amplitudes of the A phase and the B phase,
Such errors include an offset error of each of the A-phase and the B-phase, a phase error between the A-phase and the B-phase, and harmonics of the A-phase and the B-phase. Conventionally, analog processing circuits such as operational amplifiers (operational amplifiers), instrumentation amplifiers, and variable resistors have been used to correct these errors. However, as the resolution and accuracy of the detector improve, adjustments are made. There was a problem that it became more difficult.

To solve such a problem, Japanese Patent Laid-Open No. 2-251
No. 720, the analog signal output from the detector is converted into a digital signal and input to a processor, and the maximum value and the minimum value of each signal set are obtained by the processor, whereby the amplitude of each signal set is obtained. , An offset value is obtained, A-phase and B-phase signal data having the same amplitude as the obtained offset value and no offset are obtained, phase correction is performed, and the A-phase and B-phase signal data shifted by 90 degrees in phase are obtained. Is calculated, and an interpolation signal is created from the calculated A-phase and B-phase signal data, so that adjustment of the analog circuit is unnecessary. FIG. 5 shows the configuration of the rotation detector. In the figure, 1 is an amplitude adjustment unit, 11 is an A-phase signal from a rotation detector,
12 is a signal shifted by 180 degrees from the A phase, 13 is a B phase signal, 14 is a signal shifted by 180 degrees from the B phase, and 21 and 22 are for analog / digital conversion of the A and B phase signals. The A / D converter 3 is an arithmetic unit for correcting an error included in the digitally converted signal. In the interpolation method of the position detector having such a configuration, the arithmetic unit 3
In FIG. 6, an error is removed by digital operation in steps as shown in FIG. That is, step 301
From to step 311 performs the amplitude _K A, _{K B} and offset errors _O A, correction of _{O B,} from step 312 to step 332 corrects the phase error alpha, is performed to calculate the angle theta. In these speed detections, the speed is calculated using the position signal fluctuation of the position detector and used.

[0004]

However, in the prior art, the steps required to correct the amplitude error and the offset error are 10 steps, whereas the steps required to correct the phase error and detect the angle are at most 18 steps. Steps that are almost twice are required, and as a result, there is a problem that the entire processing time increases, and as a result, when the rotation speed increases, the processing time cannot be kept in time. In addition, since harmonics, which is one of the causes of waveform distortion, are not removed, there is a problem that resolution and accuracy are not improved. Further, in the above-described conventional technology, the output signal of the magnetic field detection element is input to the A / D converter, but the amplitude is not necessarily constant for each element. For example, when a Hall element is used as the magnetic field detecting element, the output differs by about twice due to variation between the elements. This is a problem that occurs in the process due to the fact that the magnetic field detecting element is a semiconductor device, and it is not easy for a user to make correction after packaging. Therefore, the output variation is input to the A / D converter as it is. Here, since the A / D converter generally guarantees the accuracy with respect to the rated input, if the input value becomes smaller than the expected input value, it means that the accuracy deteriorates accordingly. In addition, when two-phase signals are used, the output of each phase is actually different due to variations, which causes deterioration in accuracy. Further, the element may be selected so as to make the sensitivity of the Hall element uniform, but it is not realistic because it takes much time and labor for measurement. From the above, it has been difficult to commercialize this position detector. Further, in the above-described conventional technique, since the digitally processed position detection signal is quantized with a fixed resolution, the lower the speed, the more sufficient speed information cannot be obtained, making it difficult to control the servomotor. That is, assuming that the angle variation dθ and the time required for the angle variation are dt, the speed signal is expressed as dθ / dt. Assuming that dt is a constant value, the smaller the value of dθ, the lower the rotation speed. When the conventional method rotational speed reduced dθ finally is becomes smaller than the value theta ₀ quantized, the speed signal can not be obtained. Therefore, the minimum value of the speed is θ ₀ /
dt.

[0005] To solve the above problem, if the resolution of dθ is increased and dt is increased, the speed can be detected even at low speed rotation.
However, the latter is not preferable because the time for performing the process becomes longer. In the former case, it is sufficient to further divide the position signal, but it is not preferable because the size of the detection unit is required and the applicable range is narrowed. Therefore, the first problem to be solved by the present invention is
The object of the present invention is to provide a position detector capable of reducing the number of steps required for phase adjustment, shortening the processing time, and improving the resolution and accuracy. To provide a position detector that can eliminate a decrease in accuracy due to variations in sensitivity and offset when a Hall element is used as a detector.
A third object is to provide a speed detector that can accurately detect the speed during low-speed rotation when detecting the speed from the output of the position detector.

[0006]

In order to solve the above-mentioned first problem, the present invention comprises a position detector for performing position detection using a two-phase signal having orthogonality. Means for converting a two-phase analog signal into a digital signal, equalizing the amplitude of each phase of the two-phase digital signal, removing offset errors of each phase, and adjusting the phase difference of each phase to 90 degrees. A rotational position detector comprising means for performing arithmetic processing, wherein the amplitude of each phase of the position detector is made the same, the offset of each phase is removed, and the sum and difference of each phase signal are calculated. And means for making the phase difference of each phase 90 degrees using the two generated signals. In order to solve the second problem, the present invention provides a permanent magnet fixed to a rotating body, a magnetic field detecting element opposed to the permanent magnet via a gap, and attached to the fixed body, A signal processing circuit for processing a signal from the detection element, the permanent magnet is formed in a disk shape, and a magnetic encoder magnetized in one direction perpendicular to the axis of the rotating body as a position detector In the rotational position detecting device used,
An amplifier for amplifying the signal amplitude from the magnetic field detection element,
An analog / digital converter for converting an analog signal amplified by the amplifier into a digital signal, and means for performing position detection based on the signal output from the analog / digital converter. In this rotational position detecting device, the magnetic encoder has at least two or more magnetic field detecting elements in order to obtain a two-phase signal having orthogonality, and the amplitude of each signal obtained from the magnetic field detecting element is amplified by an amplifier. A configuration in which amplification is performed so as to be uniform can be employed. In order to solve the third problem, a velocity detector of the present invention includes a position detector that performs position detection using a two-phase signal having orthogonality, and a two-phase signal output from the position detector is provided. It is provided with a means for detecting the rotation speed from the derivative of the ratio and the calculation of the coefficient. In this speed detector, the position detector is composed of a permanent magnet fixed to a rotating body, a magnetic field detecting element opposed to the permanent magnet via an air gap, and mounted on the fixed body. A signal processing circuit for processing a signal, wherein the permanent magnet is formed in a disk shape, and may be a magnetic encoder magnetized in one direction perpendicular to the axis of the rotating body.

[0007]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 shows a first embodiment of the present invention, and shows the processing contents of a computing unit of the position detecting device shown in FIG. 5 in a flow form. The signal A and the signal B in step 101 are both signals obtained from the position detection unit, and the signal A is the offset error O _A
The includes the signal B includes a phase difference α and the offset error O _B with respect to the signal A. Next, in steps 102 to 109, the maximum value A _ma of the signal A and the signal B
_x and B _max and minimum values A _min and B _min are obtained. In step 110, the maximum value _A max determined _{earlier, B max} and the minimum value _{A m in,} from _{B min,} signals A and B of the amplitudes (respectively _{K A, K} B),
Offset error _(O A, O _B) are seeking. Further, in step 111, the amplitude error adjustment and the offset error adjustment are performed on the signal A and the signal B, and A ′,
It is represented as B '. There is no difference from the conventional one in the step of adjusting the amplitude error and the offset error, but the phase can be adjusted in 12 steps 112 to 123. Here, step 112
It is proved that the phase adjustment of a two-phase signal having a phase difference of 90 degrees is possible by the expression represented by. The signals A ′ and B ′ obtained from step 111 are respectively sin
Assuming θ and sin (θ + φ), A ″ = A ′ + B ′ = 2 cos (φ / 2) sin {(2θ + φ) / 2} (1) B ″ = A′−B ′ = 2 sin (φ / 2) cos {(2θ + φ) / 2} (2) Since 2cos (φ / 2) in equation (1) and 2sin (φ / 2) in equation (2) are constants, A ″ B ″ can maintain the relationship between a sine wave and a cosine wave. That is, A ″ and B ″ have a phase difference of 90 degrees regardless of the values of φ and θ. After this, step 1
13 to 122, the amplitudes of A ″ and B ″ are adjusted to be the same, and the rotation position θ is calculated in step 123.

FIG. 2 shows a second embodiment of the present invention, and is a circuit block diagram of an embodiment of a position detector for a magnetic encoder to which a position detecting circuit according to the present invention is applied. Although the magnetic encoder is not shown, a disk-shaped permanent magnet fixed to the rotating body and magnetized in one direction perpendicular to the axis of the rotating body, faces the permanent magnet via a gap,
The magnetic encoder includes a magnetic field detecting element attached to a fixed body, and detects a magnetic field generated by rotation of a disk with the magnetic field detecting element. In particular, the magnetic field detecting elements are arranged shifted by 90 degrees around the rotation axis so that signals having orthogonality, that is, sine and cosine signals are detected. Further, in order to reduce harmonic components, the magnetic field detecting elements are arranged at 180 degrees from the positions of the magnetic field detecting elements for generating sine and cosine signals for the purpose of differential. In the figure, the signals obtained from the magnetic field detecting elements are represented by A for the sine wave and B for the cosine wave, and the signals of the elements at positions shifted by 180 degrees are indicated by overbars. In this embodiment, a Hall element is used as the magnetic field detecting element, and the signal of each element is 2
Since it has two electrodes, it is described as high and low, respectively. Amplifiers 111 and 1 in amplitude adjustment section 1
At 12, 121 and 122, the amplitude is adjusted and input to the rated input value of the A / D converter 2. Also, the bias is adjusted before inputting to the A / D converter 2. A / D
After the conversion processing by the converter 2, the arithmetic unit 3 outputs θ = tan
^An angle signal is obtained by performing an operation of ^-1 (Vb / Va). The disk of the magnetic encoder was rotated at 1 Hz using a motor, and a calibration encoder was installed on one side to measure the signal accuracy. For comparison, as a conventional method, as shown in FIG. 3, the accuracy was measured by directly inputting to the A / D converter 2 without adjusting the amplitude. As a result, it was found that the accuracy of the conventional method was 7 bits, whereas the accuracy of the embodiment of the present invention was 9 bits.

FIG. 3 is a circuit block diagram of a third embodiment of a magnetic encoder position detector to which the position detection circuit according to the present invention is applied. The magnetic encoder is the same as in the second embodiment. Signal amplitudes from the respective magnetic field detection elements are converted into amplifiers 111, 112, 121, and 12 in the amplitude adjustment unit 1.
After adjusting the amplitude to be uniform at 2, the differential processing is performed by the amplifiers 113 and 123. The input of the A / D converter 2 with the amplitude adjusted to the rated input value is the same as in the second embodiment. Although the configuration is more complicated than in the second embodiment, the calculation is not performed by the CPU, so that a high-speed position detection process can be performed without imposing a load on the CPU. Similarly to the second embodiment, the accuracy was measured by inputting to the A / D converter 2 without adjustment by the amplitude adjustment unit for comparison. As a result, it was found that the accuracy of the conventional method was 7 bits, as compared with the second embodiment, whereas the accuracy of the 9 bits was possible in the embodiment of the present invention.

FIG. 4 is a block diagram of a signal processing circuit for a position detector to which the speed detecting method according to the present invention is applied. Although not described in detail, the position detector 42 is fixed to a rotating body, and faces a disk-shaped permanent magnet that is magnetized in one direction perpendicular to the axis of the rotating body. A magnetic encoder having a magnetic field detecting element attached to a body and detecting a magnetic field generated by rotation of a disk with the magnetic field detecting element. In particular, the magnetic field detecting elements are arranged shifted by 90 degrees around the rotation axis so that two signals having orthogonality, that is, sine and cosine signals are detected. Note that a drive circuit 41 is provided to drive the magnetic field detection element. Next, the speed detector 43 will be described. The speed detector 43 includes a divider 44, a differentiator 45, a coefficient calculator 46, and a multiplier 47. The details of the processing performed by each unit will be described in detail. The angle at time t is θ, and the voltages of the sine and cosine signals obtained from the position detector 22 are Vs = Vsinθ and Vc = Vcosθ, respectively. The angle θ is represented by θ = tan ⁻¹ x where x = Vs / Vc. Here, since the rotation speed is represented by dθ / dt, dθ / dt = dθ / dx × dx / dt = 1 / (1 + x ² ) × dx / dt (1)

Therefore, the sine and cosine signal voltages obtained from the position detector 42 at time t are measured,
After calculating the above x, the coefficient 1 / (1+
x ² ) is converted to a differential value dx / d of x in the coefficient calculating unit 46.
The rotation speed dθ / dt can be obtained by calculating t in the differentiator 25 and finally performing multiplication in the multiplier 47. FIG. 7 shows a processing circuit block of an optical encoder having a 12-bit resolution as a conventional example in order to compare the resolution of the speed. In the figure, 31 is a position detector, and 32 is a speed detecting unit having a CPU 33 for calculation. 10 rpm
A position detector 31 having a processing circuit for realizing the rotation speed processing method of the present invention on a shaft rotating at
The rotation speed was investigated by installing a position detector capable of dividing. In the conventional example, the minimum time for recognizing the rotation speed is 1.
In contrast to 4 msec, in the present invention, it was found that the rotational speed can be obtained in 0.7 msec if the calculation accuracy is 12 bits. Although the analog processing is used in the embodiment of the present invention, the signal from the position detector may be digitally processed and the same arithmetic processing may be performed.

[0012]

As described above, according to the present invention, the following effects can be obtained. (1) After equalizing the amplitude of each phase of the position detector and removing the offset of each phase, the sum and difference of each phase signal are calculated,
By providing means for making the phase difference of each phase 90 degrees using the two generated signals, the phase adjustment of the A phase and the B phase can be performed in 12 steps, which was conventionally 18 steps. This leads to a reduction in time, and as a result, it is possible to sufficiently follow the rotation speed of the rotating body that is the measured object, even when the rotation speed increases. (2) An amplifier for amplifying the signal amplitude from the magnetic field detecting element, an analog / digital converter for converting an analog signal amplified by the amplifier into a digital signal, and a signal output from the analog / digital converter. Means for performing position detection by using a magnetic encoder having at least two magnetic field detecting elements in order to obtain a two-phase signal having orthogonality. Since each of the signals is a rotational position detection circuit that amplifies the signal so that the amplitude becomes uniform, the position can be detected with high accuracy without impairing the accuracy. (3) In signal processing in a position detector that performs position detection using a two-phase signal having orthogonality, the rotational speed is detected from the derivative of the arc tangent and the time variation of the ratio using the ratio of the two-phase signals. Therefore, even if the rotating shaft is rotating at a low speed, a speed signal can be obtained, so that it is possible to control a rotating shaft such as a motor at the time of low-speed rotation.

[Brief description of the drawings]

FIG. 1 is a flowchart of an arithmetic processing unit according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a signal processing circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a signal processing circuit according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a signal processing circuit according to a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional position detector.

FIG. 6 is a flowchart of a calculation processing unit according to a conventional example.

FIG. 7 is a block diagram of a conventional signal processing circuit.

[Explanation of symbols]

1: Amplitude adjuster, 11: A-phase signal output from rotation detector, 12: A signal output from rotation detector and 180 degrees out of phase, 13: B output from rotation detector
Phase signal, 14: B-phase output from rotation detector and 180
Signals with different degrees of phase, 111, 112, 113, 12
1,122,123: Amplitude adjusting amplifier, 2,21,2
2: A / D converter, 3: arithmetic unit, 31 position detector (optical type), 32: speed detector, 33: arithmetic CPU, 41:
Drive circuit, 42: position detector (magnetic type), 43: speed detector, 44: divider, 45: differentiator, 46: coefficient calculator, 47: multiplier

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // G01D 5/36 G01D 5/36 W (72) Inventor Takefumi Kabashima 2 Kurosaki Shiroishi, Yawatanishi-ku, Kitakyushu, Fukuoka Prefecture No. 1 Yasukawa Electric Co., Ltd. (72) Inventor Yuji Nakamura 2-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu-shi, Fukuoka F-term (reference) 2F063 AA35 AA50 BD16 CB20 DA05 DB07 DD03 EA03 GA52 GA67 GA73 KA01 LA02 LA11 LA12 LA16 LA17 LA19 LA22 LA23 LA24 LA25 LA29 2F069 AA83 AA99 DD15 DD19 EE20 GG04 GG06 HH15 JJ17 JJ25 NN00 NN01 NN05 NN08 NN09 NN26 2F077 AA11 CC02 NN02 NN19 NN24 TT27Q02 NN27 TT27Q09 FA06

Claims (5)

[Claims] A means for converting a two-phase analog signal output from the position detector into a digital signal, comprising: a position detector for detecting a position using a two-phase signal having orthogonality; , The amplitude of each phase of the digital signal is made the same, the offset error of each phase is removed, and the phase difference of each phase is 9
A rotational position detector comprising means for performing arithmetic processing for adjusting to 0 degrees, wherein the amplitude of each phase of the position detector is made the same, and the offset of each phase is removed. A rotational position detector comprising means for calculating a difference and making a phase difference of each phase 90 degrees using two generated signals. 2. A permanent magnet fixed to a rotating body, a magnetic field detecting element opposed to the permanent magnet via a gap and attached to the fixed body, and a signal processing circuit for processing a signal from the magnetic field detecting element. Wherein the permanent magnet is formed in a disk shape, and a rotational position detecting device using a magnetic encoder magnetized in one direction perpendicular to the axis of the rotating body as a position detector, wherein the magnetic field detecting element An amplifier for amplifying the signal amplitude from
A rotary converter comprising: an analog / digital converter for converting an analog signal amplified by the amplifier into a digital signal; and means for detecting a position based on a signal output from the analog / digital converter. Position detection circuit. 3. A magnetic encoder has at least two magnetic field detecting elements to obtain a two-phase signal having orthogonality, and each of the signals obtained from the magnetic field detecting elements is uniformly amplified by an amplifier using an amplifier. 3. The rotational position detecting circuit according to claim 2, wherein the signal is amplified so as to be amplified. 4. A means for detecting a rotational speed from a differential of a ratio of a two-phase signal outputted from the position detector and a coefficient calculation, comprising a position detector for performing position detection using a two-phase signal having orthogonality. A rotation speed detecting device comprising: 5. The position detector includes a permanent magnet fixed to a rotating body, a magnetic field detecting element opposed to the permanent magnet via an air gap, and mounted on the fixed body, and a signal from the magnetic field detecting element. And a signal processing circuit for processing the permanent magnet, wherein the permanent magnet is a magnetic encoder formed in a disk shape and magnetized in one direction perpendicular to the axis of the rotating body. The rotation speed detecting device according to any one of the preceding claims.