JPH06121567A - Motor controller - Google Patents

Abstract

PURPOSE:To provide a motor controller which performs highly accurate high speed positioning control without requiring any high accuracy D/A converter circuit. CONSTITUTION:Output signal from a position sensor 6 is fed, as a signal representative of current value of position or speed, to a microcomputor 1 through a counter circuit 7. The microcomputor operates a control amount based on the difference between a command value and a current value of position or speed and delivers the control amount thus operated to a D/A converter circuit 3. In this regard, a variable voltage generating circuit generates a reference voltage for the D/A converter circuit 3 depending on an input signal received from the microcomputor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device, and more particularly to a motor control device for performing positioning control by an output signal of a position sensor.

[0002]

2. Description of the Related Art Linear motors (hereinafter referred to as "motors") are often used as driving sources for precision positioning devices having sub-micron or nanometer positioning accuracy because they are capable of running at high speed and long strokes without vibration. There is. As an example of this, the Japan Society for Precision Engineering, March 1991 issue (1
58-163).

[0003]

In a servo motor, a closed loop control system that feeds back an output signal of a position sensor to a control circuit is provided. Therefore, the positioning accuracy is improved by increasing the resolution of the position sensor. The resolution of this position sensor is the reciprocal of the detection pitch.

Further, it is digital control in which control calculation is performed by a microcomputer (hereinafter referred to as "microcomputer"). A control signal from a microcomputer is converted into an analog voltage through a digital / analog conversion circuit (hereinafter referred to as a D / A conversion circuit), and a power amplifier drives a motor drive voltage,
Alternatively, it is converted into a drive current. The motor produces thrust that is proportional to the output from the D / A.

In order to increase the moving speed of the motor and shorten the moving time, the maximum thrust is increased. On the contrary, in order to improve the stopping accuracy during positioning, reduce the minimum thrust.

Table 1 shows an example of the relationship between the resolution of the D / A conversion circuit and the minimum positioning accuracy. The maximum thrust of the motor is 500 N and the payload is 4 kg.

[Table 1]

In the conventional example, the resolution of the D / A conversion circuit is increased as the positioning accuracy becomes higher. However, as shown in Table 1, since the conversion time increases as the resolution of the D / A conversion circuit increases, the response speed of the control circuit decreases.

The present invention has been made to solve such a problem, and is a motor control device for performing high-speed and high-accuracy positioning control without using a high-accuracy D / A conversion circuit. The purpose is to provide.

[0009]

In a motor control device having a position sensor, a microcomputer and a D / A conversion circuit, D
The variable voltage generating circuit is provided at the reference voltage input terminal of the / A conversion circuit.

[0010]

In the control circuit, the microcomputer calculates the position or speed of the motor based on the output signal from the position sensor and outputs the control amount to the D / A conversion circuit. At the same time, the variable voltage generation circuit generates a reference voltage of the D / A conversion circuit according to the position or speed according to the command signal from the microcomputer.

Here, assuming that the reference voltage er of the D / A conversion circuit, the output voltage ed, the resolution D, and the control amount (input value) n,
The following Expression 1 is established.

[Equation 1] ed = n · er / D

As an example, the reference voltage e depending on the motor position
When changing r, the maximum thrust can be obtained by setting er to the maximum value when the motor is moving, and the moving time can be shortened. In addition, a small thrust is obtained by reducing er during positioning, and the positioning accuracy is improved.

[0013]

Embodiments of the present invention will be described with reference to FIGS. The same components as those of the conventional example are designated by the same reference numerals. As shown in FIG. 1, the output signal of the position sensor 6 is input to the microcomputer 1 as a current position or speed value via a counter circuit 7. The position sensor 6 is, for example, an optical or magnetic incremental encoder.

The microcomputer calculates a control amount from the deviation between the position or speed command value and the current value, and outputs it to the D / A conversion circuit 3 having an 8-bit resolution, for example. At this time, the variable voltage generation circuit 2 responds to the input signal from the microcomputer 1 by the D / A
The reference voltage of the conversion circuit 3 is output.

FIG. 2 shows a variable voltage generating circuit 2 of FIG.
It is an example showing the configuration of. As shown in the figure, the variable voltage generation circuit 2 is composed of, for example, a D / A conversion circuit 8 having 8-bit resolution. The control signal is output from the microcomputer to the D / A conversion circuit 8. The D / A conversion circuit 8 outputs a voltage corresponding to the input signal as a reference voltage of the D / A conversion circuit 3.

Table 2 shows the relationship with the minimum positioning accuracy in the embodiment of the present invention shown in FIGS. The maximum thrust and load capacity are the same as in Table 1.

[Table 2]

From Table 2, the minimum positioning accuracy is 0.00 even though the 8-bit resolution D / A conversion circuit is used.
It is 4 μm, and a value similar to that of the 16-bit D / A conversion circuit can be obtained. Further, since the D / A conversion circuits 2 and 3 are connected in parallel to the microcomputer, the conversion time remains the 8-bit D / A conversion circuit, and at the same time the high speed is improved.

FIG. 3 shows the variable voltage generating circuit 2 shown in FIG.
2 is another example showing the configuration of FIG. For example, the voltage sources 10 and 11 for outputting a constant voltage are respectively connected to the switch circuit 9
Connect to. The switch circuit 9 in FIG. 3 includes, for example, a mechanical switch or a semiconductor switch, and a logic element.

The switch circuit is switched by a control signal from the microcomputer, and either one of the voltage sources is connected to the reference voltage input terminal of the D / A conversion circuit 3. Also in this case, the same effect as the result of Table 2 is obtained.

According to the present invention, since the resolution of the D / A conversion circuit can be selected by the control of the control circuit according to the position or speed of the motor, a low resolution D / A conversion circuit is used. High-speed and high-accuracy positioning control is possible and has a remarkable effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a motor control device according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a variable voltage generation circuit in FIG.

FIG. 3 is a block diagram showing another configuration example of the variable voltage generating circuit in FIG.

FIG. 4 is a block diagram showing a conventional motor control device.

[Explanation of symbols]

 1 Microcomputer 2 Variable voltage generation circuit 3 D / A conversion circuit 4 Power amplifier 5 Motor 6 Position sensor 7 Counter circuit 8 D / A conversion circuit 9 Switch circuit 10 Constant voltage source 11 Constant voltage source 12 Constant voltage source

Claims (3)

[Claims] 1. A motor control device having a position sensor, a microcomputer, and a digital / analog conversion circuit, wherein a variable voltage generation circuit is provided at a reference voltage input terminal of the digital / analog conversion circuit. apparatus. 2. The motor control device according to claim 1, wherein the variable voltage generating circuit comprises a digital / analog conversion circuit. 3. The motor control device according to claim 1, wherein the variable voltage generating circuit includes a plurality of constant voltage generating circuits and a switch circuit.