JPS62245310A - Servomotor control device - Google Patents

Abstract

PURPOSE:To stabilize a response characteristics, by switching a control mode corresponding to a command speed. CONSTITUTION:A servomotor control device is constituted of a system controller 1 which generates a command pulse train and the control signal of a control mode, a deviation counter 2, a D/A conveter 3, and F/V converters 8-9, etc. At such a time, the titled device is constituted so that an analog switch 11 switches by a command from the controller 1, is added, and only a difference between a command speed voltage by the F/V converter 9, and a motor speed voltage by the F/V converter 8, is supplied to a driver 4 as a speed control signal, at a high speed command time. In this way, a control for a position and a speed is performed by a deviation from the deviation counter 2 at a low speed command time. Also, a speed control can be performed by switching the analog switch 11 to B side by the controller 1 at the high speed command time, and furthermore, a position control can be performed by switching it to A side at a targeted place.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention 1] The present invention relates to a servo motor control device that controls the position and speed of a servo motor using a command pulse train. The present invention relates to a servo motor control device that stabilizes operation from low speed to low speed.

[Prior Art] As conventional servo motor control devices, there are, for example, the following two types.

The first example is a system in which the vehicle is driven to the target location at a speed ill IXI and switched to position control at the target location, and a system C is provided in which a speed command to the target location and a position command at the target location are separately issued.

In this specification 4, the term "target location" is used to mean "within a range determined with a predetermined accuracy from the target location." Further, the predetermined accuracy means a relatively rough accuracy corresponding to the accuracy of speed control when speed control is being performed, and means the accuracy of position control when it is position control.

FIG. 2 shows a block diagram of this type of servo motor control device. In the figure, reference numeral 1 denotes a system controller that generates command speed data, target value data, and control signals for switching control modes. As target location data, the amount of motor movement from the point at which motor drive is started to the target location, ie, the drive m, is output. 2 is the deviation counter, 3
is a digital-to-analog converter (hereinafter referred to as a D/A converter) that converts the output of the deviation counter into voltage; 4 is a driver; 5 is a servo motor; 6 is a digital encoder; 7
8 is a waveform shaping circuit that outputs up and down pulse trains from the two-phase signals from the digital encoder 6; 8 is a frequency/voltage converter (hereinafter referred to as an F/V converter) that converts the feedback pulse train to voltage; A D/A converter that converts command speed data into command speed voltage, 11 is an analog switch that changes the control mode,
12 is a target value register that stores target value data from the controller 1;

In the above configuration, the system controller 1 sets the analog switch 11 to "I" and outputs the command speed. D
The /A converter 10 converts this command speed into a D/A to generate a command speed voltage, and the F/V converter 8 converts the feedback pulse train output from the digital encoder (pulse encoder) 6 attached to the servo motor 5 into F/A converter 10 . /V conversion to generate motor speed voltage. The difference between the command speed voltage and the motor speed voltage is used as a motor voltage to drive the servo motor 5 to the target location via the driver 4.

After reaching the target location, the controller 1 outputs a control signal, switches the analog switch 11 to A, and performs position control. In this position control, the deviation counter 2 and the D/A converter 3 operate so that the controller 1 accurately stops at the position set in the target value register 12. That is, the deviation counter 2 increments the feedback pulse train of the digital encoder 6 obtained via the waveform shaping circuit 7 to obtain position information of the servo motor 5, and at the same time detects the deviation from the stop position of the target value register 12. , this deviation is converted into a motor voltage by the D/A converter 3 to drive the servo motor 5. At this time, in order to stabilize the control system, the l! ! A speed control feedback loop is added to the control feedback loop.

In such a control method, when the rotation speed of the servo motor 5 decreases, the output from the pulse generator 6 becomes low frequency and the output of the F/V converter 8 becomes unstable, making low speed speed control unstable. There is a drawback.

The second example is a digital servo system that controls speed and position using a command pulse train.

FIG. 3 shows a block diagram of this type of servo motor control device. In the figure, 1 is a system controller that outputs a command pulse train, and 9 is an F/V converter that converts the command pulse train into voltage. In this device, a controller 1 generates a command pulse train and inputs it to a deviation counter 2. The deviation counter 2 counts this command pulse train and at the same time counts the feedback pulse train output from the pulse encoder 6 attached to the servo motor 5 and subtracts it from the number of command pulses to detect the positional deviation from the command position. The value of the deviation counter 2 is converted into a motor voltage by the D/A converter 3 as a position control command for the servo motor 5.
A servo motor 5 is driven via a driver 4. At this time as well, in order to stabilize the control system, the command pulse train and the feedback pulse train are converted into voltages by F/V converters 8 and 9, and the difference is added to the position control feedback loop.

In such a control method, the position and speed of the servo motor are controlled only by the command pulse train, but when the command pulse train becomes a high frequency, the deviation counter 2 and D/
There is a drawback that hardware such as the A converter 3 cannot follow this, resulting in malfunction.

[Objective of the Invention] The object of the present invention is (1) In view of the drawbacks of this conventional example, a servo motor control capable of obtaining a stable response over a wide range of command speeds by switching the control method according to the command speed. The goal is to provide equipment.

[Summary of the Invention] To give a specific example, the present invention counts a command pulse train and a feedback pulse train by a hard counter, and calculates the deviation by D/
A first control mode in which the command pulse train is converted into F and used as a command voltage for the servo motor to control speed and position;
/V conversion and given command speed voltage and feedback pulse train are F/
The speed is controlled by using the difference with the motor speed voltage obtained by V conversion as the motor voltage, and the second control mode switches to position control at the target location. The second i11 control mode is used to control the speed and position of the servo motor when a high-speed drive command is issued.

[Embodiment] FIG. 1 is a block diagram of a servo motor control device according to an embodiment of the present invention. Note that parts common to or corresponding to those of the conventional example are denoted by the same reference numerals. In the same figure,
Reference numeral 1 denotes a system controller that generates command pulse trains and control signals for control modes.

This device adds an analog switch 11 that is switched by a command from a controller 1 to the device shown in FIG.
When a low speed command is issued, the connection is made in the same way as shown in Fig. 3, and when a high speed command is issued, the command speed voltage and F/V from the F/V converter 9 are connected.
Only the difference in motor speed voltage across the converter 8 is supplied to the driver 4 as a speed control signal.

The operation of the apparatus shown in FIG. 1 will be explained below.

When commanding a low speed, the controller 1 sets the analog switch 11 to A to generate a command pulse train, counts this command pulse train and feedback pulse train with the deviation counter 2, and uses the deviation to determine the position and speed of the servo motor 5.
Do this.

However, if the command speed becomes high and the frequency of the command pulse train becomes high, in this mode, the deviation counter 2
There is also a risk that hardware such as the D/A converter 3 may not be able to follow this and malfunction may occur. Therefore, the controller 1 switches the analog switch 11 to 8 using the control signal, and changes the command pulse train and the feedback pulse train to F/V.
The speed of servo motor 5 is set to 1ilJI by the converted difference.
11 speed control is performed, and at the destination, the analog switch 9 is switched to A again to switch from speed control to position control.

By switching the control mode according to the command speed in this way, it is possible to prevent the error counter 2 and the D/A converter 3 from malfunctioning at high speeds, or the output of the F/V converter 8 from becoming unstable at low speeds, causing IIJill to become unstable. This makes it possible to control the servo motor 5 from low speed to high speed using a command pulse train.

[Modification 1 of Embodiment In the above description, a digital encoder is used to detect the movement amount and speed of the servo motor, but in the case of a rotary servo motor, a tachogenerator can also be used.

[Effects of the Invention] As described above, according to the present invention, stable response characteristics can be obtained over a wide range of command speeds from low speeds to high speeds by switching the control mode according to the command speed.

Additionally, in the case of rotary servo motors, it is generally possible to detect the motor speed using a tachometer, but in the case of linear servo motors, a digital encoder is used as there are no highly accurate and inexpensive speed detectors on the market. The present invention is particularly effective since it can be used to perform stable control without malfunction.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a servo motor lt control device according to an embodiment of the present invention, and FIGS. 2 and 3 are block diagrams of a conventional servo motor control device. 1.Niji system control day-ra, 2: deviation counter, 3: D
/Aq inverter, 4: Driver, 5: Servo motor, 6
:Digital encoder, 7:Waveform shaping circuit, 8.9:
F/V converter, 11: Analog switch.

Claims (1)

[Scope of Claims] A servo motor, a driver for driving the servo motor, means for outputting a command pulse train representing the drive amount and driving speed of the servo motor at each point in time, and means for generating a feedback pulse train; speed control signal generating means for converting the frequencies of the command pulse train and the feedback pulse train into voltages and outputting the difference between these voltages as a first control signal; and pulses of the command pulse train and the feedback pulse train. a position control signal generating means for outputting a voltage proportional to the difference in numbers as a second control signal; and a position control signal generating means for supplying the first control signal to the driver when driving the servo motor at high speed; A servo motor control device comprising a switching means for supplying the second control signal to the driver when driving at a low speed.