JP4867534B2 - Motor speed detection device - Google Patents

Description

  The present invention relates to a speed detection apparatus for wide-range variable speed control from a very low speed range to a high speed range of a motor.

  FIG. 4 shows a configuration example of a variable speed control device for a motor. The power converter 1 drives the motor 2 at a variable speed with a PWM output whose voltage and frequency are controlled. The speed control unit 3 performs a proportional integral (PI) operation on the deviation between the speed command and the speed detection value of the motor 2, and the current control unit 4 using this output as a current command is a deviation from the output current detection value of the power converter 1. Thus, the output voltage / frequency control signal of the power converter 1 is obtained.

  In such a variable speed control device, a pulse pickup type speed detector is often used for detecting the speed of the motor 2. FIG. 4 shows an example of a pulse pickup type speed detector. A disk (rotary body) 5 having a large number of teeth on the peripheral edge is axially coupled to the motor 2, and a constant part is provided around the disk 5. A pair of magnetic sensors 6a and 6b are arranged with a circumferential distance (determined by the tooth interval of the tooth portion), and the relative position change with the tooth portions adjacent to the magnetic sensors 6a and 6b is electromagnetically detected. Pulse generation times Ta, Tb and pulses corresponding to the rotational position and speed of the motor 2 are detected by the time / phase latch processing unit 7 and the timer 8 from the two-phase pulse signals Sa and Sb respectively detected and obtained by the magnetic sensors 6a and 6b. The generated phases Pa and Pb are extracted, and the speed calculator 9 calculates the speed of the motor 2 and further calculates the rotor phase from these pulses.

  FIG. 5 shows respective waveforms in the magnetic sensors 6 a and 6 b and the time / phase latch processing unit 7. In the figure, the A-phase pulse and the B-phase pulse are pulses having the generation periods TA1, TA2, TB1, TB2 of the pulse signals Sa, Sb from the magnetic sensors 6a, 6b, and the pulse edges are the edge positions of the pulse signals Sa, Sb. The phase θ and the time t are values of a counter that counts the edges of the pulse signals Sa and Sb. From these phase θ and time t, pulse generation times Ta and Tb and pulse generation phases Pa and Pb are obtained by calculation. For this calculation, the 1f method using the pulse edges of the same phase is obtained from, for example, the phase θ of the period T1f and the time t, and the 4f method using all the pulse edges of the A phase pulse and the B phase pulse is, for example, the phase of the period T4f. Obtained from θ and time t.

  Such a pulse pickup type speed detector currently performs detection based on the two-phase pulse shown in FIG. 5 or detection based on the one-phase pulse, and the pulse count number (phase) and pulse generation Speed detection is performed based on time (see, for example, Patent Document 1 and Patent Document 2).

Patent Document 1 proposes a method for measuring an accurate average speed even in the case where there is uneven motor speed fluctuation in a two-phase system of an A-phase pulse and a B-phase pulse. Patent Document 2 proposes a method for reducing an error in rotational speed detection in the one-phase method.
JP-A-6-1118090 JP-A-8-76855

  There are the following types of encoders and features of the disk 5 and the magnetic sensors 6a and 6b.

  In a system that requires a wide range of rotation speeds, a mechanical pulse type is effective if mechanical strength at high rotation speed is to be obtained at low cost. However, since there is a limit to the mechanical processing accuracy of gears and slits, it is difficult to increase the number of pulses. When the number of pulses is small, the frequency of occurrence of pulses is low in the extremely low speed region, so that the speed and position control gain cannot be increased, and control in the extremely low speed region becomes difficult.

  Also, the pulse-type detection method has different characteristics between the 1f method and the 4f method. For example, the 1f method uses TA1, TA2, TB1, and TB2 in FIG. 5, and the detection accuracy is high, but the phase information is delayed, so the detection delay is large. The 4f method uses T1, T2, T3, and T4 in FIG. 5, and the detection accuracy is low, but the detection delay is small because the frequency of occurrence of edge pulses is high.

  At present, the 1f method and the 4f method are adopted according to the difference in the operating speed range of the motor to be applied and the device specifications. In addition, both types of encoders are provided for speed detection in a wide range from a very low speed range to a high speed range, and a method of switching them according to the motor speed is conceivable.

  An object of the present invention is to provide a motor speed detection device capable of detecting a wide range of speeds with high accuracy and responsiveness with an inexpensive device configuration.

  In order to solve the above-mentioned problems, the present invention converts the rotational position of a rotating body that is shaft-coupled to a motor into multi-pulses that detect three or more phase pulse signals, and detects the rotational speed / phase from these pulse signals, or the high-speed range. In this case, the motor speed / rotation phase is detected by switching to a two-phase pulse signal and switching to a pulse signal of three or more phases in the low speed range, and has the following configuration.

( 1 ) a rotating body shaft-coupled to a speed detection target motor;
A pulse signal (Sa to Sd) in which the change in relative position with respect to the tooth portion or slit of the rotating body is magnetically or optically converted into four phases of A phase, B phase, C phase, and D phase , and an A phase pulse The C phase pulse signal Sc is delayed by 1/4 phase with respect to the signal Sa, the B phase pulse signal Sb is delayed by 1/4 phase with respect to the C phase pulse signal Sc, and with respect to the B phase pulse signal Sb. A sensor for detecting the D phase pulse signal Sd in four phases delayed by 1/4 phase;
From the pulse edge waveform synchronized with all edge positions of the four-phase pulse signals (Sa to Sd) and the timer signal, the pulse generation time (Ta to Td) and pulse generation phase (Pa to A time / phase latch processing unit for obtaining Pd);
The two-phase pulse generation time (Ta, Tb) and the pulse generation phase (Pa, Pb) are taken in, and the pulse edge phase of the same phase and the speed or rotation phase of the motor at a high speed are determined from this pulse edge period. A high-speed arithmetic processing unit to be obtained;
The four-phase pulse generation time (Ta to Td) and the pulse generation phase (Pa to Pd) are taken in, and the phase of the four-phase pulse edge and the speed or rotation phase of the motor at a low speed are determined from these pulse edge periods. A low-speed calculation processing unit to be obtained;
A switching determination unit for determining a high speed and a low speed of the motor from the calculation result of the high-speed calculation processing unit;
There is provided a changeover switch for switching and outputting the outputs of the two arithmetic processing units according to the determination result of the switching determination unit.

  As described above, according to the present invention, the rotation position of the rotating body that is shaft-coupled to the motor is converted to multiple pulses that detect three or more phase pulse signals, and the rotation speed / phase is detected from these pulse signals, or 2 in the high speed range. The phase pulse signal is switched to a pulse signal of three or more phases in the low speed range, and the speed / rotation phase of the motor is detected, so that a wide range of speed detection with improved accuracy and responsiveness can be achieved with an inexpensive device configuration. There is.

(Embodiment 1)
FIG. 1 shows a configuration diagram of a variable speed control device for a motor, and a portion different from FIG. 4 is a speed detection device. In the present embodiment, three or more sensors are installed on one disk (rotary body) to make it multiphase, and to increase the accuracy and responsiveness by making multipulses in a low speed region.

  FIG. 1 shows a case where a mechanical pulse type encoder is used, and the conventional two-phase detection is changed to four-phase detection in order to increase the number of pulses in the low speed region. In this four-phase detection, four magnetic sensors 6a to 6d are arranged at a peripheral portion of a disc (rotary body) 5 having a large number of teeth at a peripheral portion with a constant circumferential distance. 6a to 6d are respectively detected magnetically relative position changes with the tooth portions adjacent to each other, and the time / phase latch processing unit 7 and the timer are obtained from the four-phase pulse signals Sa to Sd obtained by the magnetic sensors 6a to 6d. 8, pulse generation times Ta to Td and pulse generation phases Pa to Pd corresponding to the rotational position and speed of the motor 2 are extracted, and the speed calculation unit 9 calculates the speed of the motor 2 and further calculates the rotor phase from these pulses.

  FIG. 2 is synchronized with the waveforms of the four-phased (A-phase, B-phase, C-phase, D-phase) pulse signals Sa to Sd obtained in the magnetic sensors 6a to 6d and all the edge positions of these pulse signals Sa to Sd. The pulse edge waveform of 4f system which obtains a pulse is shown. The relative positions of the magnetic sensors 6a to 6d with respect to the teeth of the disk 5 are such that the C phase is delayed by 1/4 phase with respect to the A phase obtained in the pulse signals Sa to Sd, and similarly, the B phase is 1 with respect to the C phase. / 4 phase is delayed, and 4 phases are detected in which D phase is delayed by 1/4 phase relative to B phase.

  According to the speed detection device configured as described above, pulses that can be detected from one tooth can be multiphased into the A to D phases, and the control performance is improved by increasing the number of pulses in the low speed range, thereby achieving extremely low speed. Can detect a wide range of speed from high to high speed. In addition, the number of teeth of the disk 5 is as small as that of the prior art, making it easy to manufacture with a high processing accuracy of the teeth, and there is no cost increase. Then, it is only necessary to install four magnetic sensors having the same structure, and the time / phase latch processing unit 7 can be additionally provided with the same signal processing circuit.

(Embodiment 2)
In the first embodiment, the edge accuracy of the pulses obtained in the magnetic sensors 6a to 6d is good between the 1f edges of each phase (TA1, TA2, TB1, TB2 in FIG. 5), but between the edges of different phases. The accuracy (T1, T2, T3, T4 in FIG. 5) is not good. This is because of errors due to mounting accuracy and gear machining accuracy. In particular, when the number of phases is three or more, the accuracy between each phase is determined by the mounting accuracy.

  In the present embodiment, in the high speed region where the number of detection pulses per unit time increases, the two-phase 1f method is detected with high accuracy as in the conventional case, and in the low speed region where the detection pulses per unit time decreases, multiphase edge detection is performed. Thus, speed detection with improved accuracy and responsiveness is achieved throughout the entire area by increasing the number of pulses.

  FIG. 3 shows an example of the configuration of a motor variable speed control device. The difference from FIG. 1 is that a high speed / low speed switching function block is added to the speed detection device. The high-speed detection unit 10H takes in the pulse generation times Ta and Tb and the pulse generation phases Pa and Pb, and performs speed calculation processing by the two-phase 1f method. The low-speed detection unit 10L takes in the pulse generation times Ta to Td and the pulse generation phases Pa to Pd and performs a speed calculation process using a four-phase 4f method. The switching determination unit 11 determines the high speed and the low speed from the calculation result of the high speed detection unit 10H, and switches the changeover switch 12 based on the determination result. If the speed is high, the calculation result of the high speed detection unit 10H is speed detected. If it is a low speed range, the calculation result of the low speed detection unit 10L is extracted as a speed detection signal.

  According to the speed detection device configured as described above, in the high speed range, the two-phase 1f is detected with high accuracy in the same manner as in the past, and in the low speed range, multi-pulse detection is performed to detect multiple pulses. Even when there is an error due to the machining accuracy of the gears, good speed detection can be achieved in the entire area.

  In the above embodiments, the case where a mechanical pulse type magnetic sensor is used is shown. Instead, the same effect can be obtained by using the optical pulse type shown in the above table. Can do. In this case, the four optical sensors instead of the magnetic sensor optically detect a change in the relative position with the tooth portion or slit of the rotating body as a four-phase pulse signal.

The block diagram of the variable speed control apparatus of the motor which shows Embodiment 1 of this invention. The polyphase-ized waveform diagram by four magnetic sensors. The block diagram of the variable speed control apparatus of the motor which shows Embodiment 2 of this invention. The structural example of the conventional variable speed control apparatus of a motor. The time / phase detection waveform diagram by two magnetic sensors.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power converter 2 Motor 3 Speed control part 4 Current control part 5 Disc (rotary body)
6a to 6d Magnetic sensor 7 Time / phase latch processing unit 8 Timer 9 Speed calculation processing unit 10H High-speed detection unit 10L Low-speed detection unit 11 Switch determination unit 12 Changeover switch

Claims (1)

A rotating body shaft-coupled to the speed detection motor;
A pulse signal (Sa to Sd) in which the change in relative position with respect to the tooth portion or slit of the rotating body is magnetically or optically converted into four phases of A phase, B phase, C phase, and D phase , and an A phase pulse The C phase pulse signal Sc is delayed by 1/4 phase with respect to the signal Sa, the B phase pulse signal Sb is delayed by 1/4 phase with respect to the C phase pulse signal Sc, and with respect to the B phase pulse signal Sb. A sensor for detecting the D phase pulse signal Sd in four phases delayed by 1/4 phase;
From the pulse edge waveform synchronized with all edge positions of the four-phase pulse signals (Sa to Sd) and the timer signal, the pulse generation time (Ta to Td) and pulse generation phase (Pa to A time / phase latch processing unit for obtaining Pd);
The two-phase pulse generation time (Ta, Tb) and the pulse generation phase (Pa, Pb) are taken in, and the pulse edge phase of the same phase and the speed or rotation phase of the motor at a high speed are determined from this pulse edge period. A high-speed arithmetic processing unit to be obtained;
The four-phase pulse generation time (Ta to Td) and the pulse generation phase (Pa to Pd) are taken in, and the phase of the four-phase pulse edge and the speed or rotation phase of the motor at a low speed are determined from these pulse edge periods. A low-speed calculation processing unit to be obtained;
A switching determination unit for determining a high speed and a low speed of the motor from the calculation result of the high-speed calculation processing unit;
A motor speed detecting device comprising a changeover switch for switching and outputting the outputs of the two arithmetic processing units according to the determination result of the switching determination unit.

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