JPS6010325B2 - Servo control method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a positioning servo control system.

As is well known, positioning servo control systems require position and velocity signals of a movable member. Conventionally, the position signal of a movable member is detected by a position detector such as an induction sensor or a photo sensor that is connected directly or indirectly to a servo motor that drives the movable member, but the speed signal is generally detected by 8U. A method of detection using a speed generator installed in the vehicle was being explored. For this reason, there have been problems such as response deterioration due to increased inertia and increased cost.
As a method to solve this problem, some methods have been proposed to obtain a speed signal by differentiating a position signal detected by a position detector. By the way, this method detects two position signals with different phases, inverts each of these position signals to obtain a total of four position signals, and differentiates each of them.
The peak value is sampled with a gate signal and used as a speed signal, but since the gate signal is created by simulating the position signal, it is difficult to deal with fluctuations in the phase difference, amplitude, and center of the two position signals. This has the disadvantage that the speed signal fluctuates and control becomes unstable. Furthermore, in this method, the position pulse (that is, this pulse indicates the unit movement amount of the movable member) used for the input clock of the position error counter that represents the distance between the current position and the target position of the movable member is also Since the signal is created by Schmitt using a constant voltage as a reference, the detection position of the position pulse relative to the actual position will fluctuate due to fluctuations in the power supply voltage and fluctuations in the position signal, just as with the speed signal, resulting in unstable control. It has the disadvantage of being SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a stable servo control system that obtains speed signals and position pulses that are not affected by fluctuations in power supply voltage, position signals, etc. Therefore, the feature of the present invention is to differentiate two periodic position signals having different phases from each other detected by a position signal detector, and to rectify and superimpose these differentiated signals using an ideal full-wave rectifier circuit. In addition to obtaining a speed signal, the average value of the amplitudes of the two periodic position signals is used as a reference signal, and this reference signal is used as a Schmitt bias to obtain a position pulse.

Hereinafter, the contents of the present invention will be explained in detail with reference to the drawings. 1st
The figure shows a block diagram of an embodiment of the positioning servo control system of the present invention.

In FIG. 1, 10 is a servo motor, which includes a photo encoder (position detector) 11 that generates position signals with different phases as the rotor rotates. movable parts)
29 are directly or indirectly connected to each other and rotate and stop together with the motor 10. At the start of the operation, the movement distance command and position error counting device 25 outputs a signal indicating the distance and direction in which the movable member 29 should move (or rotate) as an output command signal, that is, distance information and a rotation direction command signal. Of these, the distance information is sent to the speed command signal generator 20 as the initial value of the position error instruction signal, and the speed command signal Vc is determined based on the contents thereof. That is, load 2
The larger the required travel distance of 9, the larger Vc becomes, and the motor rotates at a higher speed. On the other hand, the rotation direction instruction signal is sent to the selection circuit 24, and the output signal of the inverting amplifier 22 (Vc-10V
w10) or the output signal of the inverting amplifier 23 (Vc10VW-
) is selected and sent to the amplifier 28. Now, when the motor 0 starts rotating, the photoencoder 11 detects two periodic minute position signals indicating the unit movement amount of the load 29 and whose phases are different from each other by 2 points. This signal is sent to a position signal amplifier 12, where it is amplified to a predetermined amplitude to obtain a position signal A and a position signal B. These two signals may be sawtooth waves, sine waves, or similar waveforms. The two position signals A and B are differentiated by differentiators 13 and 14 to produce a differential signal A';d^/d
After being converted into t, B'=dB/dt, they are rectified by full-wave rectifiers 16 and 17, and further rectified by full-wave rectifier adder 18.
is added.

That is, the output of this full-wave rectification adder 18 is the speed signal Vw representing the actual speed of the motor 10. On the other hand, the position signals A and B are also sent to a position signal amplitude average value detector 19, and the amplitude fluctuations thereof are monitored and used to relatively cancel the fluctuations in the speed signal due to the amplitude fluctuations of the position signals. . The output of the position signal amplitude average value detector 19 becomes the input of the speed command signal generator 20. Further, the position signal B is also sent to the position pulse signal generator 15, and as the motor 10 rotates, a position pulse is output every time the load 29 moves a unit distance. As described later, this position pulse signal generator 15
consists of a position signal Schmitt circuit, which uses the signal obtained by the position signal amplitude average value detector 19 as its bias, so that even if the amplitudes of the position signals A and B vary, the deviation of the position pulse with respect to the absolute position is maintained. I'm trying not to let it happen. The contents of a well-known position error counter built in the moving distance command and position error counting device 25 are subtracted by the position pulse output of the &direct pulse signal generator 15.

The output of this position error counter is given to the speed command signal generator 20 as a position error instruction signal, and a speed command signal Vc of a level corresponding to the distance between the target stop position of the load 29 and the current position is created. Then, this speed command signal Vc and the actual speed signal Vw which is the output of the full-wave rectification adder 18 are
, Vw adder 21 and further inverting amplifier circuit 2
The signal is inverted twice at 2 and 23 and sent to the selection circuit 24, and one of the inverted outputs is selected to drive the motor 10. As the motor 10 rotates, the contents of the position error counter decrease, and the level of the speed command signal Vc also decreases, and the speed of the motor 10 decreases.In this way, the contents of the position error counter decrease to zero. When the load 29 reaches the target position, a target position arrival instruction signal is sent from the movement distance command and position error counting device 25 to the selection circuit 2.
Output to 4. This blocks Vc and Vw,
Instead, the position signal and differential signal addition circuit 27 is left in place, and the addition signal of the position signal A and the differential signal A' is sent to the selection circuit 24.
is selected and sent to the amplifier 28, and the motor 10 is stopped. FIG. 5 is a time chart of the main signals to explain the overall operation of FIG. The direction rotation instruction and the movement distance thereof are outputted from the movement distance instruction and position error counting device 25, and accordingly, the speed instruction signal Vc+ is inputted to the amplifier 28, and the amplified voltage is applied between the terminals of the motor 10. As a result, motor 0 starts rotating in the forward direction, and position signals A and B are output at the same time, and a speed signal Vw- obtained by differentially rectifying this position signal is also input to amplifier 28.These V
c+ and Vw- have opposite polarities and always act to cancel each other out. However, due to the rotor inertia, load inertia, etc. of the motor 10, the rotational speed of the motor 0 cannot immediately respond to changes in the speed command signal V, but increases or decreases with a certain gradient. At the time of initial acceleration, Vc10Vw->0, the motor current flows in the negative direction, and the motor 10 continues to accelerate. When the rotational speed of the motor 10 approaches the set speed based on the position error, Vc becomes 10Vw-〒0, the motor current becomes almost zero, and constant speed rotation is performed.
As the motor 10 rotates, the contents of the position error counter decrease, and when a certain position error is reached, the level of the speed command signal Vc0 is switched and decreased. On the other hand, since the rotation of the motor 10 cannot respond immediately, Vc temporarily becomes 10VW-0, and the motor current flows in the opposite direction. That is, the motor 0 is decelerated as the speed command signal Vc0 decreases. Thereafter, similar operations are repeated one after another, and when the load 29 reaches the target position, the content of the position error counter becomes zero, and a target position arrival instruction signal is output to the selection circuit 24. This allows V
c10 Vw- is cut off, and instead the position signal A and its differential signal A' are input to the amplifier 28, and the motor 10 is stopped while being damped. FIG. 2 shows a specific configuration example of the main circuit in FIG. 1, and the same parts as in FIG. 1 are given the same reference numerals.

FIG. 4 shows the main signal waveforms at constant speed in FIG. 2. Now, when the position signal A is input to the capacitor C31 of the differentiator 13, if d^/dt≦0, the differential waveform determined by C31 and the constant of the
A connection point between 31 and resistor R32 appears, which connects resistors R33 and R34 of the full-wave rectifier 16 and the full-wave rectifier adder 18.
It is input to the Vc, Vw adder 21 through the resistor R36. Note that when the input is negative, the output of the amplifier OP37 of the full-wave rectifier 16 is positive, so in this case the diode D
The output of the amplifier OP37 is separated from the differential signal by i35. - On the other hand, in the case of d^/dt and ○, a differential waveform determined by the constants of C31 and Kamesagi-so appears at the connection point between capacitor C31 and resistor R32, and this is multiplied by R34/R33 by the full-wave rectifier 16, and the resistor Vc, VW through R36
It is input to the adder 21. The above operation is the same for the position signal 8, and the result obtained by adding the differential signals of the position signals A and B in this way by the full-wave rectification adder 18 is Vc,
It is sent to the Vw adder 21. The above is a case where a full-wave rectifier circuit is adopted, but the position signals A and B are inverted and a total of 4
It goes without saying that the same results can be expected even if half-wave rectification is applied to the two position signals. Blocks 19 and 20 in FIG. 2 are specific examples of the configuration of circuit portions for obtaining the speed command signal Vc and the bias voltage for generating position pulses. position signal A with this)
, B are inverted by oven amplifiers OP41 and OF42, and a total of 4
The negative peak values of the three position signals A, B, A, and B are each sampled and held by a diode and a capacitor. For example, the diode Di43 and the capacitor C44 correspond to a sampling and holding circuit for the signal A obtained by inverting the position signal A. By summing these four signals, the average value of the amplitudes of the position signals A and B, ie, FB2=pa(IAI+IBi), is obtained at the output side of the oven amplifier OP47.
By using this as a reference signal when creating a speed command signal, it is possible to relatively cancel fluctuations in the speed signal when the amplitudes of the position signals A and B change. Note that the voltage generated by the diode Di2 and the resistor RI is input to the obeamp OP47 via the resistor R2, and this is to compensate for the drift due to temperature of the diode Di43 and other three similar diodes. Further, the diode Di2 is connected to the negative voltage source through the sampling hold section which is the contact point between the diode Di43 and the capacitor C44, and this is to prevent the capacitor C44 from being discharged when the motor is at rest. The other sampling and holding circuits are also the same. The speed command signal generator 20 is connected to the position signal amplitude average value detector 1.
It consists of a circuit group of multiple resistors and switches connected in parallel between 9 and the Vc, Vw adder 21, and the on/off control of the switches of each circuit is based on the movement distance command and the position error content of the position error counter 25. determined by That is, when the position error is large, the selected resistance is small and the speed command signal current supplied from the speed reference signal FB2 to the Vc, Vw adder 21 is large. Conversely, the larger the position error,
A large resistance is selected. In this case, resistors R44, R47 and diode Di are used as the smallest circuit for the speed command signal.
5, Di6, AND circuit IC5, diode Dj3, D
There is i4, but this is a circuit that was added specifically due to the timing of speed command signal activation and restrictions on switch elements. The diodes Di5 and Di6 are 5 V in the AND circuit when the V is low. L is absorbed by this) to prevent leakage current.
Diode Dj3, D of position signal amplitude average value detector 19
i4 is for compensating the temperature drift of the diodes Di5 and Di6 when V is high. The resistor R44 has the role of absorbing the loH of the AND circuit IC5 when V, is /.i, and suppressing fluctuations in the speed command signal current in this circuit. As is clear from the above explanation, the circuit of the speed command signal generator 20 can be constructed using only an IC, a resistor, and a diode. The position pulse generator 15 is a circuit that uses the speed reference signal (or position signal amplitude average value) FB2 as a bias and generates position signals B and B using a resistor R43, a Schmitt ICI, a resistor R42, and a Schmitt 2, respectively.

As shown in Figure 3, these circuits can be equivalently configured with a comparator, a resistor, and an inverter IC, and their function is to control the absolute position of the position pulse with respect to the amplitude fluctuation of the position signal, as described above. The key is not to shift the The differentiating circuit 26, the position signal and differential signal adding circuit 27 are composed of resistors R9, RI0, RI1, and a capacitor C32, and the position signal A is connected to the capacitor 32 through the resistor R9.
The differential signal A' between the resistor band and the resistor band is the resistor RI
0 to the selection circuit 24.

The selection circuit 24 is a moving distance command and position error counting device 2.
The output of the inverting amplifier 22 or 23 is selected until the position error content of 5 becomes zero, and when the position error content becomes zero and the target position arrival instruction signal is output from the device 25, the position signal and differential signal addition circuit 27 Select output.

Note that the timing at which the destination position arrival instruction signal is issued is not at the complete destination position as shown in FIG. 5, but at i/8 to 1'4 cycles of the position signal before the target position in a strict sense. The signal selected by the selection circuit 24 is sent to the amplifier 28
However, when the input value exceeds a certain value, the voltage Vs at the connection point between the resistor R12 and the diode Di7 is input to the diodes Di7, Di8 and the resistor R.
It is saturated to a constant value by a constant voltage circuit composed of 13. On the other hand, a motor current detection resistor R1 is connected in series with the motor 10.
6 is connected, and a voltage V is generated by the motor current. Since the input impedance of the driver DRVI is very large, it can be equivalently set as 5, v=lxR16.From this, the motor current=lxR16 also becomes 6. Therefore, when Vs is saturated, the motor current becomes constant. In addition"
As shown in this embodiment, the method of grounding one end of the motor current detection resistor R16 and detecting the current value from the other end is applied when the driver DRVI is T type, but when DRVI is H type However, similar current feedback is possible by detecting the voltage between both terminals of a motor current detection resistor connected in series with the motor 10. Some conventional constant current circuits have a Zener diode connected in parallel with the feedback resistor of the OBE amplifier, but in this method, the operating resistance of the Zener diode changes in response to the input signal, making it impossible to reach the complete saturation voltage. It's hard to get. As is clear from the above description, according to the present invention, stable and highly accurate servo control is possible even with respect to phase difference fluctuations, amplitude fluctuations, and center fluctuations of two position signals.

[Brief explanation of the drawing]

FIG. 1 is an overall block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a specific configuration example of the main parts in FIG. 1, and FIG.
The figure shows an equivalent circuit of another embodiment of the position pulse signal generator 15. "Figure 4 is a diagram of the main signal waveforms when the motor rotates at a constant speed, and Figure 5 explains the overall operation of Figure 1. 10... Motor, 11... Photo encoder (position signal detector), 12... Position signal amplifier, 13, 1
4... Differentiator, 15... Position pulse signal generator, 16, 17... Full wave rectifier, 18...
... Full-wave rectification adder, 19 ... Position signal amplitude average value detector, 20 ... Speed command signal generator, 21 ...
Vc, Vw adder, 22...Inverting amplifier, 2
3... Inverting amplifier, 24... Selection circuit, 2
6...Moving distance command and position error counting device, 2
6...Differential circuit, 27...Position signal and differential signal addition circuit, 28...Amplifier, 29...Load. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A motor that drives a movable member, and two periodic positions that are connected directly or indirectly to the rotating shaft of the motor and that have a phase difference of π/2 according to the rotation of the motor. means for generating a signal, means for obtaining a signal by differentiating the two position signals, means for rectifying and superimposing the differentiated signals to obtain an actual speed signal of the motor, and a means for obtaining a signal by respectively differentiating the two position signals; means for obtaining a signal representative of the average value of the amplitude;
means for generating a position signal using an average value of the amplitude of the position signal as a bias to generate a position pulse representing a unit movement distance of the movable member; and means for generating a position pulse representing a unit movement distance of the movable member; a position error counter means for outputting position error information representing a distance of the position signal, and a speed reference signal that uses the average value of the amplitude of the position signal as a speed reference signal, and creates a speed command signal whose level decreases sequentially in accordance with the value of the position error information. When the distance between the current position and the target position of the movable member is large, a signal obtained by adding the speed command signal and the actual speed signal is selected, and near the target position, the position signal and its differential signal are selected. means for selecting the summed signals;
A servo control system comprising: an amplifier that amplifies the selected signal and supplies it to the motor. 2. Claim 1, characterized in that the amplifier is equipped with a current feedback type constant current circuit as a circuit portion for driving the motor, and the constant current circuit is composed of a Zener diode, a diode, and a resistor. Servo control method described.