JPS6373891A - Motor control circuit - Google Patents

Abstract

PURPOSE:To improve resolving power even at super low speed and to control a motor at high accuracy, by a method wherein in addition to period of rise edge, period of drop edge is also observed. CONSTITUTION:Output of a rotary encoder 112 coupled in concentric relation with a rotary drive shaft of a servomotor 110 is connected to a period measuring circuit 114. Clock pulse CLK as reference drive signal of the servomotor 110 and clockwise rotation/counterclockwise rotation signals CW/CCW of the servomotor 110 are introduced in the period measuring circuit 114. Output side of the period measuring circuit 114 is connected to a drive circuit 116 of the servomotor 110. In this case, period from rise edge of the output pulse of the rotary encoder 112 to next rise edge and period from drop edge to next drop edge are observed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor control circuit, and more specifically, the present invention relates to a motor control circuit, and more specifically, a rotation speed detector is disposed in a motor rotating at an extremely low speed, and a rotation speed detector is provided for each phase of a plurality of phases from the rotation speed detector. The present invention relates to a motor control circuit that controls the rotation of a motor using a deviation signal obtained by observing the period and comparing it with a reference period signal.

Conventionally, when performing high-precision control in a servo system, a feedback system is constructed by attaching a tacho generator or the like to the rotating shaft of a servo motor, and an output signal related to the voltage from the tacho generator is once fed back to control the servo motor. It is widely practiced to compare the control signal with a motor control reference signal and use this signal to control the rotation of the servo motor.

However, when a tacho generator is used as described above to obtain a feedback signal in the rotation control of a servo motor that rotates at a very low speed, there is a problem in that the device itself must be considerably expensive. For this reason, conventionally, instead of the tachogenerator, there has been a device that incorporates a rotation speed detector such as a relatively inexpensive low-return encoder into the servo motor and achieves digital feedback control by counting the number of pulses. It has been developed and used in various ways.

However, in various devices that require motors to be driven at extremely low speeds, such as 0.3 to 0.5 revolutions per minute, the number of pulses output from the rotary encoder is extremely small, and therefore feedback control is performed using these few pulses. The problem is that it is difficult to do so in terms of accuracy.

In order to solve this problem, it is conceivable to use an extremely high frequency rotary encoder that outputs many pulses even during low speed rotation, but such a rotary encoder is very expensive.

The present invention has been made in order to overcome the above-mentioned disadvantages, and the rotational speed of the motor is extremely low, and therefore the number of output pulses from the row encoder disposed coaxially with the motor is small. Even in the case of a pulse train, it is possible to improve control accuracy by measuring both the rising edge and falling edge periods of the pulse train, and it is easy and inexpensive to manufacture using a commercially available motor control IC. The purpose is to provide a possible motor control circuit.

In order to achieve the above object, the present invention compares the period of a pulse train from a pulse generator connected to a motor with a reference period signal, and performs the rotation side of the motor according to the deviation signal obtained thereby. The device includes a motor control IC in which means for obtaining the deviation signal includes a D/A converter;
It is characterized by consisting of a logic gate and an analog switch.

Next, preferred embodiments of the motor control circuit according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 1)0 indicates a servo motor, and reference numeral 1)2 indicates a rotary encoder coaxially connected to the rotational drive shaft of the servo motor 1)0. The output side of the rotary encoder 1) 2 is connected to a period measuring circuit 1) 4. W/CCW is introduced into the period measuring circuit 1) 4 by a clock pulse CI- as a reference drive signal for the servo motor 1) 0 and clockwise rotation/counterclockwise rotation signals of the servo motor 1) 0. The output side of the period measuring circuit 1)4 is connected to the drive circuit 1)6 of the servo motor 1)0.

Next, the internal configuration of the period measuring circuit 1) 4 is shown in FIG.

In FIG. 2, reference numbers 26, 28, 30 and 32
is a motor control IC (for example, type TC9142P Q
uarts PLL Motor Control I
(manufactured by Toshiba Corporation), each of which is an FG pulse input terminal that represents the rotational speed of the motor. Circulating signal input terminal ■, 8 pino l-D/A
It is the output of the converter and has a motor speed control system output terminal (2). In addition, each IC has a power terminal [phase], a ground terminal ■, a motor PLAY/5TOP switching terminal ■, and a division ratio setting terminal ■ for the reference period signal set to a predetermined potential in advance, or a predetermined signal system. Assume that it is connected to.

In addition, in FIG. 2, reference numbers 20.22 and 24
These logic gates are substantially composed of an exclusive OR gate 20 for controlling the direction of rotation, an inverter 24, and a negative logic AND gate 22 as a decoder for mutually decoding the FG pulses.

Furthermore, reference numerals 34 and 36 are analog switches whose opening and closing are controlled by the negative logic AND gate 22, and the output terminals of each analog switch are connected to each other. The connection point is connected as the deviation signal to the servo motor drive circuit 1) 6 to drive and control the motor 1) 0. In FIG. 2, the O-marked reference numerals attached to each terminal of a logic symbol represent the terminal number of the logic symbol, while the alpha bent lowercase letters a, b,
c, d represent individual gates or switches housed in the same package.

The motor control circuit according to this embodiment is basically constructed as described above, and its operation and effects will be explained next.

First, the servo motor 1) 0 is driven by a clock pulse CLK that is sent through a frequency divider (not shown) that divides a pulse signal from a crystal oscillator (not shown) by a large number, for example.
It rotates at an extremely low speed of 0.3 to 0.5 revolutions per minute, and on the other hand, under the rotational driving action of the servo motor 1) 0, the rotary encoder 1) 2 outputs a very small pulse signal of about 60 per second. Output. Therefore, the rotary encoder 1
) 2 will be compared with the reference period of the reference signal in the period measuring circuit 1) 4. At this time, as shown in Fig. 3, the period Aφ from the rising edge to the next rising edge of the output pulse of the rotary encoder 1) 2 and the period A'φ from the falling edge to the next falling edge are Inside the motor control ICs 30 and 26, the period is compared with the reference period and the deviation is measured.

Next, the deviation signal obtained through the above process is applied to the IC.
The signal is converted into an analog signal by a D/A converter inside 30 and 26, and then the drive circuit 1) of the servo motor 1)0
6 and is used as a drive control signal.

Therefore, the above operation will be explained in detail with reference to FIGS. 2, 3, and 4.

In FIG. 2, the case where W is supplied to the exclusive OR gate 20 as a clockwise rotation signal, that is, the case where the LO(0) signal is supplied to the terminal 2 of the logic gate 20 will be described. In addition, exclusive
If the counterclockwise rotation signal CCW is supplied to the half-or gate 20, this clockwise rotation signal will be easily understood by the explanation about 7 o'clock, so a detailed explanation thereof will be omitted.

Now, the A-phase pulse (hereinafter referred to as FG) of the rotary encoder 1) 2 is connected to the terminal
A) is supplied. In this case, the applicable exclusion
A pulse having the same phase as the input is sent to the output terminal (2) of the Shiv-OR gate 20, as can be understood from the truth table of FIG. Therefore, the output signal, that is, F as shown in FIG.
The GA pulse is supplied to the terminal (2) of the motor control IC 30. The IC30 counts the reference period signal CLK that arrives during the Aφ interval from the rising edge of the FGA pulse to the next rising edge, and outputs a deviation proportional to the number of pulses within the Aφ interval.
It is output from the output terminal ■ through a converter (not shown).

Figure 3 shows the output signal from terminal ■ of this FIc30! Illustrated in

On the other hand, the D/
A, the deviation output of the converter (not shown) is F as shown in Figure 3d.
If you use the GA pulse, you will be able to understand the words easily. As mentioned above, the output terminal ■ of the logic gate 20 is connected to F.
Since the GA pulse is being sent, the FGA pulse appears at the output terminal (3) of the inverter 24. Therefore, the above A′φ
The deviation output of the D/A converter (not shown), which depends on the period from the falling edge of the A-phase pulse to the next falling edge, is obtained at the output terminal (2) of the 1'C26.

By the way, as mentioned above, the B-phase pulse FGB is the other output of the low reencoder that outputs two pulse trains with a phase difference from each other with the A-phase pulse FGA, but for this pulse train as well, the A-phase pulse It goes without saying that the accuracy of the servo motor 1) 0 can be further improved if a deviation output can be obtained by performing a process similar to the process performed above.

Next, the operation of obtaining a deviation signal for servo motor control related to this B-phase pulse will be explained using FIGS. 2 and 3. In FIG. 2, the FGB pulse is
32 is easily understood. Therefore, in the same manner as above, the motor control period is compared with the reference period, and the motor control period from one rising edge of the FGB pulse to the next rising edge is compared. 1) The deviation signal for 1 is obtained at the terminal (3) of the IC32, and the deviation signal from one falling edge to the next falling edge is obtained from the IC32.
28 terminal ■ is obtained.

From the above, FGA, FC, = ~, FGB and FG
Bζ Such deviation signals are obtained at f, j, , m, and k, respectively, in the time chart of FIG.

Now, in order to drive the servo motor 1)0 with each of the deviations No. 13, it is necessary to switch and drive the servo motor 1) using four switches with different timings. In other words,
The four switches only need to open and close at intervals of 174 cycles.

This switching action is performed by the analog switches 34a, 34b, 36a, 36b shown in FIG.

That is, it can be easily understood from the four negative logic analogues 1- in the circuit diagram shown in FIG. 2 and the time charts b to e in FIG. FGA, FGA.

The analog switches 36a, 34a are shifted from each other by 174 cycles in correspondence with each pulse train of FGB, .
, 36b, and 34b are shown. As a result, deviation signals related to the four phases shown in FIG. 3n are sent to the servo motor drive circuit 1) 6 to drive and control the servo motor 1) 0. In this manner, in this embodiment, a total of four types of cycles are compared with the reference cycle, so that higher motor rotation drive control is achieved.

According to the present invention, as described above, in order to avoid the problem that only a small number of pulses are obtained when the servo motor rotates at an extremely low speed and sufficient control cannot be achieved, In addition to the period of the edge and the edge, the period of the falling edge and the edge and the edge of the falling edge is also observed, and this is also compared with the reference signal. Therefore,
Even in a very low-speed control system, that is, a control system that generates few pulses, the resolution is further improved and the effect of achieving highly accurate control of the motor can be obtained.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to this embodiment f1, and various improvements and design changes can be made without departing from the gist of the present invention. Of course.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention, FIG. 2 is a detailed circuit diagram showing an example of the configuration of a period measurement circuit in one embodiment of the present invention, and FIGS. FIG. 2 is a waveform diagram and a truth table for explaining the operation of an embodiment of the present invention. FIG. 20... Exclusive OR gate 22... Negative logic AND gate 2.1... Inverter 26.28.30.32... Morph control IC34
, 36...Analog switch 1) 0...Servo motor 1) 2...Low reencoder 1) 4...Period measurement circuit 1) 6...Servo motor drive circuit

Claims (1)

[Claims] (1) A device that compares the period of a pulse train from a pulse generator connected to a motor with a reference period signal, and controls the rotation of the motor based on the deviation signal obtained thereby, and means for obtaining the deviation signal. A motor control circuit comprising a motor control IC including a D/A converter, a logic gate, and an analog switch.