JPH07118928B2 - DC motor / servo mechanism - Google Patents

Description

The present invention relates to a servo mechanism for a DC motor.

[Conventional technology]

A conventional DC motor servo mechanism converts a pair of sinusoidal analog position signals of an encoder into a pair of square wave digital signals having a phase difference of 45 degrees and uses the digital signals as feedback signals of the DC motor.

[Problems to be solved by the invention]

With the general servo mechanism as described above, when the DC motor is stationary or at a low speed, for example, the rotation angle of the DC motor is within the range (a) of the square wave digital feedback signals FB1 and FB2 in FIG. In the case of, the position of the rotation angle in (a) was not known, and the accuracy of the DC motor could not be improved. Further, when the motor is stationary, the motor moves one step, and the feedback voltage is applied to the control unit only after the counter counts the digital feedback signal, so that the response is poor.

The present invention aims to eliminate the above defects.

[Means for solving problems]

In order to achieve the above object, an encoder that outputs a pair of sinusoidal analog position signals having a 90-degree phase difference depending on the rotation direction of a DC motor, and a pair of sinusoidal analog position signals of the encoder that have a 45-degree phase difference. Means for converting into a square wave digital signal, and before and after the zero cross point based on the digital signal and the sine wave analog position signal.
The sawtooth waveform creating means for creating a sawtooth waveform voltage composed of a position voltage signal that is substantially linear in degrees, and D / that outputs a staircase waveform voltage based on the count value of the digital signal.
A converter and the output of the D / A converter by adding the sawtooth voltage waveform at an appropriate magnification to obtain a voltage that linearly changes with respect to the rotation angle of the DC motor, and The summing amplifier is configured to output an addition value to the rotation command voltage to the DC motor, and a voltage-current conversion amplifier that converts the output of the summing amplifier into a current and supplies the current to the DC motor.

[Action]

In the above configuration, when the DC motor is driven by the DC motor rotation command voltage, the rotational movement of the output shaft of the DC motor is converted from the sinusoidal voltage to the sawtooth waveform voltage,
The sawtooth waveform voltage is added to the stepwise waveform voltage output of the D / A converter at an appropriate ratio to form a feedback analog voltage that changes linearly with the rotation angle of the DC motor.
This voltage is added to the DC motor rotation command voltage by the adding amplifier, and the added voltage is converted into a current and supplied to the DC motor. The summing amplifier is set so that the summed voltage of the feedback analog voltage and the motor rotation command voltage becomes zero at the zero cross point of the sawtooth waveform voltage, and the DC motor can be stopped accurately at the zero cross point.

〔Example〕

Hereinafter, the configuration of the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings.

In FIG. 1, reference numeral 2 is a commercially available encoder connected to the output shaft of the DC motor 4. By rotating the motor output shaft, as shown in FIG. 2, approximate sine waves A and B centered at zero volts are generated. It is configured to output with a phase difference of 90 degrees. When the motor output shaft rotates forward,
The phase A approximate sine wave is set to have a phase advance of 90 degrees with respect to the phase B approximate sine wave, and when the motor rotates in the reverse direction, the phase 90 phase is delayed. The approximate sine wave A is input to the amplifier 6, and the approximate sine wave B is input to the amplifier 8. 10,12 is a polarity reversal device, 1
Reference numeral 4 denotes a comparator, which is imaged so that the approximate sine wave A is input to the input end A and the approximate sine wave B is input to the input end B. When A + B <0, LOW of "0" A signal is output, and when A + B> 0, a High signal of "1" is output as shown in FIG. Also, the input terminal A of the comparator 16
Is connected so that the approximate sine wave A is input to the input terminal and the inverted polarity output of the approximate sine wave B is input to the input terminal. When A + <0, a LOW signal of “0” is output, and A +
When> 0, a high signal of "1" is output as shown in FIG. Square wave digital signals from comparators 14 and 16, 22 and 24
Is inverted by the inverters 18 and 20, and the input ends 22 and 24 of the multiplexer 26 and the direction determination up / down pulse generation circuit 7
It is configured to enter 0. 28, 30, 32, 34 are differentiating circuits, 36, 38, 40, 42 are diodes, and 44 is an operational amplifier, which are connected to a reference voltage setting input terminal of a D / A (digital analog) converter 46. 48 is an integrating circuit, 50 is an amplifier, 52 is a variable resistor, 54 is an operational amplifier, 56 is a voltage-current conversion amplifier, and 72 is an up / down counter.

Next, the operation of this embodiment will be described. Line 74 or 76
When the motor rotation command pulse is output from the, the pulse is counted by the up / down counter 72, the counted digital data is converted into an analog voltage by the D / A converter 46, and the D / A converter 46 outputs the motor rotation command output. Then, the output is input to the summing amplifier 54.
The output of the summing amplifier 54 is converted into a current by the amplifier 56 and supplied to the DC motor 4, so that the motor 4 starts rotating. When the motor 4 rotates, the encoder 2 causes the approximate sine wave voltage A, which has two 90 degree phase differences, as shown in FIG.
Output B. The voltages A and B and the voltage inverted by the inverters 10 and 12 are the channels of the multiplexer 26.
Applied to C1, C2, C3, C4. These channels C1, C2, C
3, C4 is selected by the switch 60 controlled by the digital signal of the input ends 22 and 24, and before and after the zero cross point.
At 45 degrees, a sawtooth voltage 62 consisting of a position voltage signal that is approximately linear is created. When the input terminals 22 and 24 of the multiplexer 26 are 1,1, the channel C1 is selected, when it is 0,1, the channel C2 is selected, and when it is 1,0, the channel C3 is selected.
Is selected and channel C4 is set to be selected when 0,0. On the other hand, the rotation speed of the DC motor 4 is
Differentiating circuits 28, 30, 32, 34, the channel selecting means of the multiplexor 26, the integrating circuit 48, the amplifier 50, and the variable resistor 52 convert the signals into speed voltage signals. On the other hand, the comparator 14,1
The pulse signal of 6 is converted into a directional pulse by the circuit 70, and the pulse is counted by the up / down counter 72. The D / A converter 46 converts the output of the up / down counter 72 into an analog voltage signal and outputs a stepped waveform voltage 58 whose timing matches the sawtooth waveform voltage 62.
Is output. The summing amplifier 54 is provided with the sawtooth waveform voltage 62 and
The stepwise waveform voltage output 58 of the D / A converter 46 is added at an appropriate magnification. This added voltage becomes a feedback voltage signal 64 that changes linearly with respect to the rotation angle of the output shaft of the DC motor 4. Since this voltage signal 64 is set to have a negative relationship with the motor rotation command voltage, the amplifier 56 uses the feedback voltage signal with respect to the rotation command voltage.
The output voltage decreases as the absolute value of 64 increases, and when the magnitudes of the absolute values of the rotation command voltage and the feedback voltage signal 64 match, the amplifier 54 outputs zero. The DC motor 4 is controlled by the output of the amplifier 54.
The operational amplifier 44 takes out the absolute values of the approximate sine wave voltages A, B, -A, -B and supplies them as a reference voltage of the D / A converter 46, and the sawtooth waveform regardless of the output voltage fluctuation of the encoder 2. The voltage 62 is connected smoothly and linearly.
Incidentally, 64 'is the voltage signal 64 when the +1 step command is received.

[Effect] As described above, the present invention converts the output of the encoder that outputs two approximate sine wave voltages having different phases by 90 degrees by the rotation of the DC motor into the sawtooth waveform voltage, and the sawtooth waveform voltage and the stepwise waveform voltage. Since a feedback signal that changes linearly with the waveform voltage is obtained, the return voltage can be applied before the DC motor moves one step and the responsiveness can be improved, and the stationary position of the DC motor can be controlled with high accuracy. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a block electronic circuit diagram, FIG. 2 is an operation explanatory diagram, and FIG. 3 is an explanatory diagram. 2 …… Encoder, 4 …… DC motor, 6,8 …… Amplifier, 10,
12 …… Polarity inverter, 14,16 …… Comparator, 18,20 …… Inverter, 26 …… Multiplexer, 28,30,32,34 …… Differentiation circuit,
36,38,40,42 …… Diode, 44 …… Op Amp, 46 …… D
/ A converter, 48 …… integrator circuit, 50 …… amplifier, 52 …… variable resistor, 54 …… summing amplifier, 56 …… voltage-current conversion amplifier, 60 …… switch, 62 …… sawtooth waveform voltage

Claims (1)

[Claims] 1. An encoder that outputs a pair of sinusoidal analog position signals having a 90-degree phase difference depending on the direction of rotation of a DC motor, and a pair of squares that have a 45-degree phase difference between the sinusoidal analog position signals of the encoder. Means for converting into a wavy digital signal, and sawtooth waveform creating means for creating a sawtooth waveform voltage composed of a position voltage signal which is substantially linear at 45 degrees before and after the zero cross point based on the digital signal and the sinusoidal analog position signal. , A D / A converter that outputs a staircase waveform voltage based on the count value of the digital signal, and the rotation angle of the DC motor by adding the sawtooth voltage waveform to the output of the D / A converter at an appropriate magnification. On the other hand, the voltage that changes linearly is obtained, and the added value of the voltage and the rotation command voltage to the DC motor is output. Amplifier and a DC motor servo mechanism to convert the output of said summing amplifier to a current, characterized in that it consists of a voltage-current converting amplifier to be supplied to the DC motor.