JPS5847044B2 - Servo control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a servo control device having a feedback loop using a position detector.

FIG. 1 shows the configuration of a conventional servo control device of this type.

In the figure, 1' is a command position θi given from a command pulse train Pi and a current position θ given from a position feedback loop described later.

Which deviation θ is proportional to the position that generates the position deviation voltage e?
A voltage converter 4' is a voltage synthesizer for obtaining a voltage e-e', which is the difference between the position error voltage e described above and a speed voltage e'7 described later, = Ei, that is, a drive command voltage Ei, and 6' is a drive command voltage Ei. 7' is a servo motor driven by the drive voltage obtained from the servo amplifier 6';
8' is a position detector consisting of a resolver provided in a feedback loop 9' extending from the servo motor 7' to the converter', and 10' is a feedback loop 11 extending from the servo motor' to the input end of the servo amplifier 6'.
A speed generator (tachogenerator) is provided as speed voltage forming means 5'.

In a servo control device having a position feedback loop 9' using a position detector 8' as shown in the figure, a speed voltage e'7 proportional to the rotational speed of the servo motor' is applied to the servo motor in order to improve the control characteristics of the servo motor'. It is necessary to feed it back to the motor amplifier 6'.

For this reason, the speed generator 1 is connected to the output shaft of the servo motor'.
0' was installed to obtain a voltage (differential value of position) proportional to the speed of the servo motor'.

However, since the speed generator 10' generally has a commutator, it has the disadvantage of requiring maintenance and inspection, and ripples etc. contained in the voltage generated by the speed generator 10' have an adverse effect on the control of the servo motor'. There are disadvantages such as

An object of the present invention is to provide a servo motor control device that does not require a speed generator.

Hereinafter, specific examples of the present invention will be explained in detail with reference to FIGS. 2 and 3.

In FIG. 2, 1 is a position/voltage converter that generates a position deviation voltage e proportional to the deviation θ between a command position θi given from a command pulse train P and a current position layer θ0 to which a position feedback loop described later is also given. , 2 is the output voltage e obtained by differentiating the position error voltage e outputted by the converter 1.
1 is a differentiating circuit which generates the signal 1, and 3 is a frequency/voltage converter which generates a voltage e2 proportional to the frequency of the command pulse train P.

4 subtracts the voltage e2 from the voltage e1 described above to form the speed voltage ev (-e2-el), and this speed voltage e
The drive command voltage E is obtained by adding the position bias voltage e mentioned above to v.
This is a voltage synthesis unit that synthesizes i.

In the present invention, the differentiator circuit 2, the frequency/voltage converter 3, and the voltage synthesizer 4 constitute a speed voltage forming means 5.

6 is a servo amplifier that amplifies the drive command voltage Ei to form a drive voltage; 7 is a servo motor driven by the drive voltage output from the servo amplifier 6; 8 is a feedback loop from the servo motor to the converter 1; This is a position detector consisting of a resolver provided in 9.

The frequency of the command pulse train Pi is the speed of the servo motor,
The number of pulses commands the amount of movement.

Now, the position/voltage converter receives the command pulse train Pi from the outside and the output voltage of the position detector 8, and calculates the command position θ· and the current position θ.

A deviation voltage e as shown in FIG. 3 is generated which is proportional to the error θ.

This deviation voltage e drives the servo motor via the servo amplifier 6 so that the deviation θ becomes zero.
Even if you try to drive the servo motor 7 by simply applying only the position deviation voltage e to the servo amplifier 6, if the speed feedback signal for braking is lost, the servo motor will become unstable even if there is a slight disturbance. Becomes out of control.

Therefore, in the present invention, the output voltage e1 of the differentiating circuit 2 that differentiates the position error voltage e, and the output voltage e2 of the frequency/voltage converter 3 that converts the frequency of the command pulse train Pi into voltage.
A speed voltage ev is generated by comparing the two voltages in a voltage combining section 4.

That is, since the position deviation voltage e, which is the output of the position/voltage converter, is a function of (θi-θ0), the output voltage e1 of the differentiating circuit 2 obtained by differentiating it is as follows.

In addition, the output of frequency/voltage converter 3 Since the voltage e2 is proportional to the command speed, It can be expressed as

Therefore, the input signal voltage to the servo amplifier 6, ie, the drive command Ei, is E, -80.

1°2, so by substituting equations (1) and (2) into this equation, it becomes the speed voltage ev because it is the differential value of, which is equal to the speed voltage eI in FIG. 1, and the speed generator 10' You can have the same control as using .

In addition to the resolver, the position detector 8 may be a rotary drive type or linear drive type pulse encoder.

Further, as shown in FIG.
a part 41 that synthesizes l) to form ev, and (ev
) may be formed separately into a part 42 for synthesizing, or as shown in FIG. Alternatively, as shown in FIG. 6 (e-e2)
The part that synthesizes 4. and (e-62) 161 may be formed separately.

As explained above, in the servo control device according to the present invention,
The output voltage of the differentiating circuit that differentiates the output voltage of the position/voltage converter and the output voltage of the frequency/voltage converter that converts the frequency of the command pulse train into voltage are synthesized in the voltage synthesizer to obtain the speed voltage. No need for a generator,
Therefore, the mechanical structure becomes simple and economical.

Further, in the present invention, troubles caused by the speed generator and adverse effects caused by ripples included in the output voltage of the speed generator do not occur.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional servo control device, FIG. 2 is a block diagram showing an embodiment of the servo control device according to the present invention, FIG. 3 is a diagram showing the output characteristics of a position/voltage converter, and FIG. 6 through 6 are configuration diagrams showing other embodiments of the voltage combining section used in the present invention. 1...position/voltage converter, 2...
Differential circuit, 3... Frequency/voltage converter, 4
. . . Voltage synthesis section, 5 . . . Speed voltage forming means, 9 . . . Position feedback loop.

Claims (1)

[Claims] 1. A position feedback loop, a position/voltage converter that generates a position deviation voltage proportional to the deviation between the command position given from the command pulse train and the current position given from the position feedback loop, and a speed voltage formation that creates a speed voltage. a servo control device that obtains a drive command voltage from the position deviation voltage and the speed voltage, wherein the speed voltage forming means includes a differentiating circuit that differentiates the position deviation voltage, and a voltage that differentiates the frequency of the command pulse train. 1. A servo control device comprising: a frequency/voltage converter that converts a speed voltage into a speed voltage; and a voltage synthesis section that synthesizes a speed voltage from the output voltage of the differentiation circuit and the output voltage of the frequency/voltage converter.