JPS63133883A - Speed controller for motor - Google Patents

Abstract

PURPOSE:To settle a motor in a short time by adding the output of a phase loop to the output of a speed loop as a speed control signal, and subtracting the value obtained by multiplying the output of the phase loop by a speed deviation from the speed control signal. CONSTITUTION:A speed control signal (c) is obtained on the basis of a speed deviation (b) by a PI regulator 7. The output of a phase comparator 9 is applied to a low pass filter 10. An adder 11 adds the speed control signal (c) and a phase control signal (d) as a speed control signal (f). A half-wave rectifier 13 outputs a signal b' coincident with the deviation (b) only when an input is positive. A multiplier 12 multiplies the signals b', d, and applies it to a variable amplification factor amplifier 14. A subtractor 15 subtracts the signal (h) from the amplifier 14 from the signal (f), and applies a speed control signal (e) to a motor driver 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a speed control device for controlling the speed of an electric motor;
In particular, the present invention relates to a speed control device for an electric motor that has improved response characteristics in acceleration and deceleration states.

[Prior art and its problems]

(Prior Art) Conventionally, as a speed side '4111 device for controlling the rotational speed of an electric motor, for example, as shown in FIG. In addition to converting it into a speed setting value Ns, the speed of the motor 3 to be controlled is detected using a pulse generator 4, and the speed signal Ni is applied to a subtracter 6 via an F/■ converter 5 to calculate its deviation. A speed control device is known in which a speed control signal C is applied to a pr regulator 7 having integral and proportional elements, and the speed of the motor 3 is controlled via a motor driver 8 by obtaining a speed control signal C. In such a speed control device, the PI controller 7 controls the speed signal of the motor 3 so that the deviation becomes zero, and when the speed deviation becomes zero, it stops the integration and maintains a constant output. The motor 3 is rotated at a constant speed. The responsiveness of the speed signal at this time is expressed, for example, as shown in FIG.

The overshoot and settling time of the speed signal Ni with respect to the speed setting value Ns depend on the PI constant of the PI adjuster 7.

However, in such a motor speed control device, there is a delay in response to disturbances such as torque fluctuation of the motor 3, and F/V
Due to the temperature characteristics and aging of the converters 2 and 5, it has been difficult to achieve highly accurate speed control.

Therefore, as shown in Fig. 4, the output a of the oscillator 1 is
and the phase of the output of the pulse generator 4 are compared by a phase comparator 9, and the comparison output is applied to an adder 11 via a low-pass filter 10, and a control signal C based on the speed deviation S and a control signal d based on the phase deviation are generated. The speed side where the speed control signal C for the motor driver 8 is obtained by adding the 111 devices are known. In this way, even if the frequency of the detection signal of the pulse generator 4 fluctuates even slightly and a phase difference with the output of the oscillator 1 occurs, it can be immediately corrected, so that the motor 3 can be operated at a constant speed with high precision.

However, a speed control device including such PLL control has a problem in that responsiveness of transient state control is not good when the set speed is changed. That is, as shown in FIG. 6, immediately after changing the speed setting value Ns, the oscillation frequency of the oscillator 1 and the oscillation frequency of the pulse generator 4 are significantly different, and the output d of the low-pass filter 10 is in a saturated state. There is. Therefore, the sum of the control signal C obtained from the PI regulator 7 and the control signal d obtained from the low-pass filter 10 is as shown by the broken line c+d in FIG. 6, and based on this, the speed when the motor 3 is actually controlled The control signal e is as shown in FIG. In this way, the phase deviation has no meaning unless it falls within the pull-in range of the phase loop in a transient state, so the problem is that the speed signal Ni' has a lot of overshoot in a transient state, as shown in the figure, and the settling time becomes longer. There was a point.

In order to solve such problems, for example,
134310 and JP-A-60-157604, speed control devices are also known in which PLL control is not performed during acceleration and deceleration, but PLL control is applied after entering the phase loop pull-in region. The former applies PLL control when the motor reaches a set speed,
The latter is P when the change in the speed signal is less than a predetermined value.
LL control is added.

(Problems to be Solved by the Invention) In such a conventional speed control device that includes PLL control, it is necessary to connect and disconnect the comparator and PLL control output for determining the PLL control range from the actual speed value. An analog switch, etc. is required for this purpose. For example, as shown in Fig. 7, if the speed setting value NsL Ns2 itself changes, the optimum pull-in area also changes as nl, n2, so it is necessary to change the reference signal level of the comparator each time. However, there was a problem in that the configuration was extremely complicated.

[Technical Problem] The present invention has been made in view of the problems of the conventional speed control device for electric motors. The technical challenge is to control it so that it stabilizes at .

[Structure and effects of the invention]

(Means for Solving the Problems) The present invention provides an oscillator having an oscillation frequency corresponding to the rotational speed to be controlled of an electric motor, a speed detector for detecting the speed of the electric motor, and an oscillation frequency of the oscillator and the speed detector. The first one converts each into a voltage signal. a second F/V converter;
The phase difference between the output of the oscillator and the output signal of the speed detector is compared with a regulator that outputs a speed control signal through control including an integral operation based on the deviation of the second F/V converter given the deviation. It has a phase comparator, a low-pass filter to which the output of the phase comparator is given, and an adder that adds control signals obtained from the adjuster and the low-pass filter, respectively, and based on the speed control signal of the adder. This is a motor speed control device that controls the speed of an electric motor, and as shown in FIGS. 1 to 3, the output of a low-pass filter and the first . A multiplier that multiplies the deviation of the second F/V converter, a variable gain amplifier that amplifies the output of the multiplier, and a speed control signal obtained by subtracting the output of the variable gain amplifier from the speed control signal of the adder. The present invention is characterized by comprising a subtracter having the following properties.

(Operation) According to the present invention having such features, phase loop control is added to the speed deviation control loop to generate a speed control signal, and the output of the low-pass filter and the speed deviation are multiplied by a multiplier, and the multiplier By subtracting this value from the speed control signal, a new speed control signal is obtained to control the speed of the motor.

(Effects of the Invention) Therefore, according to the present invention, the speed control signal becomes almost flat in a region where phase control has no meaning immediately after the set speed is changed, and the motor speed is controlled by a phase control loop in response to this. The speed can be changed almost linearly, similar to a control device that does not. When the motor speed approaches the set value and enters the phase control loop, the speed deviation becomes smaller, so the multiplication value of the speed deviation and the low-pass filter output also becomes smaller, reducing the influence of the multiplication term and controlling the motor speed. I can do it. Therefore, compared to any of the conventional speed control systems, there is less overshoot, and the motor speed can be settled to the set value in a short settling time. From then on, precise speed control using a phase-locked loop is possible. It can be performed.

[Explanation of Examples]

(Configuration of First Embodiment) FIG. 1 is a block diagram showing a motor speed control device according to a first embodiment of the present invention. In this figure, the same parts as in the conventional example are given the same reference numerals. In this embodiment as well, the output of the oscillator 1 that oscillates a reference frequency corresponding to the speed of the motor to be controlled is given to the first F/V converter 2 to obtain the speed setting value Ns, and the Pulse generator 4 is connected and generates an output corresponding to its rotation speed.
A signal from a speed detector such as the above is given to the second F/V converter 5. And the first. Output N of the second F/V converter 2°5
The subtractor 6 subtracts s, Ni (Ns - Ni) to obtain the speed deviation, and the PI adjuster 7 generates the speed control signal C based on the speed deviation, which is basically the same as in the conventional example. Also in this embodiment, the output of the oscillator 1 is applied to the phase comparator 9 as in the conventional example shown in FIG. 4, and the output of the pulse generator 4 is also applied to the phase comparator 9. The phase comparator 9 outputs the phase difference between these signals, and supplies the output to the low-pass filter 10.

The low-pass filter 10 supplies only the low frequency components of the input signal to the adder 11 and the multiplier 12 as a phase control signal d. The adder 11 adds the speed control signal C obtained from the pig) H unit 7 and the phase control signal d of the low-pass filter 10 to form a speed control signal f.

In this embodiment, the speed deviation obtained from the subtracter 6 is also added to the half-wave rectifier 13. The half-wave rectifier 13 performs half-wave rectification of this signal, and transmits a signal b' to the multiplier 12, which corresponds to the speed deviation only when the input is in the positive direction. The multiplier 12 multiplies these signals b' and d, and provides the multiplication output g to the variable gain amplifier 14. The variable amplification factor amplifier 14 is an amplifier whose amplification factor k can be arbitrarily set, and its output h (=kg) is sent to the subtractor 1
Give to 5. The subtracter 15 subtracts the signal from the variable gain amplifier 14 from the speed control signal f, and provides the signal to the motor driver 8 as a new speed control signal e. Therefore, the speed control signal e is given by the following equation.

e = d + c - kg = d + c - k

(motion) Next, the operation of the speed control device of this embodiment will be explained.

The oscillator 1 is oscillated on the current side L0, and the oscillation frequency is set to a frequency corresponding to the rotational speed of the motor 3, and the F/V converter 2
Assume that the motor 3 is started by setting the output of the set value to Ns. Then, the speed setting value Ns, which is the output of the F/V converter 2, becomes a constant level as shown in FIG. Here, the amplification factor of the variable amplification factor amplifier 14 is adjusted so that the component d of the PLL loop of the speed control signal e at time 0 becomes zero. That is, if the amplification factor k of the variable amplification factor amplifier 14 is set to the reciprocal of the speed deviation value S (k = 1/b'), the speed control signal e will be equal to C at the start of acceleration, and control based on the speed deviation S will be performed. It operates only as a loop. Therefore, the rotational speed of the motor 3 is initially O, and the speed deviation obtained by the subtractor 6 is large, so the speed control of the proportional element is mainly performed by the PI regulator 7, and the rotational speed gradually increases, and the speed signal Ni also rises as shown. Immediately after the start of the operation, the speed deviation is large as shown in FIG. Therefore, the output g of the multiplier 12 gradually decreases with ripples as shown in FIG. The output h (=kg) is similarly large and then gradually decreases.On the other hand, the phase control signal d of the low-pass filter 10 is also applied to the adder 11, and the speed control signal f output from the adder 11 is It contains ripples as shown by the broken line in Figure 2. Therefore, the speed control signal e obtained by subtracting the output of the variable gain amplifier 14 from the speed control signal f is the second
It changes as shown in the figure, and after the start of the operation it becomes almost flat until around time tl, and the speed signal Ni also increases almost linearly (and after time tl, the variable gain amplifier 1
4 decreases, the component of the output d of the PLL control loop increases, and the speed control signal e gradually becomes the same curve as the speed control signal f, including the ripple due to the phase difference of the phase comparator 9. It becomes something. However, as the speed of the motor 3 increases, the phase loop almost enters the pull-in region at the point where the influence of the output of the phase comparator 9 becomes large, so the speed control signal does not significantly overshoot as shown in the figure. (The speed will be quickly settled to the set value Ns.

(Description of second embodiment) FIG. 3 is a block diagram showing a second embodiment of the present invention.

In this embodiment as well, the same parts as in the first embodiment are given the same reference numerals. In this embodiment, the variable gain amplifier 16 is an amplifier (VCA) whose gain is controlled by voltage input,
The amplification factor k is set based on the output Ns of the F/V converter 2. In this way, the amplification factor of the variable gain amplifier 16 is automatically set based on the speed setting value Ns at that time, so there is no need to manually adjust the gain k of the summing gain amplifier, making the speed control device easy to use. It can be done.

Furthermore, although each of the embodiments described above uses a normal motor as the motor, it goes without saying that the invention can also be applied to speed control of a linear motor. In this case, a linear encoder is used as the speed detector instead of a pulse generator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a speed control device for an electric motor according to the present invention, FIG. 2 is a time chart showing changes in the speed control signal, and FIG. FIG. 4 is a block diagram showing an example of a conventional speed control device; FIGS. 5 and 6 are time charts showing changes in speed control signals of the conventional speed control device; FIG. The figure shows P for different settings.
5 is a time chart showing changes in the pull-in range of the LL loop. ■--Oscillator 2,5--F/V converter 3--Motor 4-m--Pulse generator (speed detector) 6.15-- Subtractor 7...-PI adjuster 8-...-
・Motor driver 9-...Phase 1'l
1o・−・−・Low pass filter 11・・−・−
Adder 12 - Multiplier 13 - Half-wave rectifier 14. 16 - Variable gain amplifier Patent applicant Tateishi Electric Co., Ltd. agent Patent attorney Kanki Okamoto (and 1 other person) No. 2 figure 8% IJI

Claims (2)

[Claims] (1) An oscillator having an oscillation frequency corresponding to the rotational speed of the electric motor to be controlled; a speed detector that detects the speed of the electric motor; and an oscillator that converts the oscillation frequencies of the oscillator and the speed detector into voltage signals, respectively. 1. a second F/V converter; a regulator that is given a deviation between the first and second F/V converters and outputs a speed control signal through control including an integral operation based on the deviation; a phase comparator that compares the phase difference between the output of the oscillator and the output signal of the speed detector; a low-pass filter to which the output of the phase comparator is applied; and a control signal obtained from the regulator and the low-pass filter, respectively. an adder that adds the output of the low-pass filter and the first and second F/Vs, the speed control device for a motor that controls the speed of the motor based on the speed control signal of the adder. a multiplier that multiplies the deviation of the converter; a variable gain amplifier that amplifies the output of the multiplier; and a subtraction that subtracts the output of the variable gain amplifier from the speed control signal of the adder to obtain a speed control signal. A speed control device for an electric motor, comprising: (2) The amplification factor of the variable amplification factor amplifier is the first F/
2. The motor speed control device according to claim 1, wherein the speed control device is determined based on the output of a V converter.