JPH02214491A - Servo controller - Google Patents

Abstract

PURPOSE:To reduce the dead time of a speed detecting signal for calculation so as to secure a sufficient phasic margin to a servo system by dividing a servo cycle by the number of motors to be controlled and calculating the control signal for servo control based on the rotating speed of each motor detected in the preceding detecting cycle during each divided period. CONSTITUTION:A fixed-cycle timer 10 outputs a pulse signal P the cycle of which is the 1/2 of a servo cycle T. From the pulse signal P, decode signals D1 and D2, the cycles of which are equal to the servo cycle and phases of which are shifted from each other by a 1/2 cycle, are produced by means of a binary counter 11 and decoder 12. By means of the decode signals D1 and D2, speed detectors 6 and 7 alternately output speed signals V1 and V2 at every servo cycle. A microprocessor 13 calculates and outputs the control signal of the motor of the number indicated by a count CO at the timing given by means of an interrupt signal INT.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a servo control device that performs speed servo control of a plurality of motors with one device.

<Prior art> When controlling position and speed in a so-called software servo control device that performs servo control using a microprocessor, etc., the speed detection signal generally uses the average speed of the controlled object during the previous servo cycle. Use. The average speed is determined by detecting the displacement of the controlled object with an encoder, and from the number of encoder pulses that came during the previous servo cycle, the period of the encoder pulses, etc.

When controlling a robot arm with two or more axes with one software servo device, one microprocessor can control two or more axes.
This means that more than one motor will be controlled.

As a servo control device used in such a case, there is one shown in FIG. 4, for example. This figure shows a device that controls a two-axis robot arm.

In the figure, 1 and 2 are motors for driving the first axis and motors for driving the second axis, 3 and 4 are position detection means for detecting the rotational positions of motors 1 and 2, and 5 is a constant-speed regulator that generates a pulse signal with a constant period. Period timer, 6 and 7 are position detection signals P1 of position detection means 3 and 4
This is a speed detector that detects the rotational speed of the motor based on P2 and P2. These detectors 6 and 7 perform detection operations alternately based on the output pulses of the fixed-cycle timer 5.

8 is a microprocessor that configures a servo system using software. The microprocessor YS 8 calculates and outputs control outputs C+ and C2 for servo-controlling the motor based on the command speed V and the speed detection signal from the speed detector 6.7. The calculation of the microprocessor 8 is started using the output pulse of the fixed period timer 5 as an interrupt signal.

This control device operates according to the flowchart shown in FIG.

<Problems to be Solved by the Invention> However, in such a device, the calculation of the control output of the first axis drive motor and the control output of the second axis drive motor are performed serially. Regarding the configuration of the shaft, the dead time delay of the speed detection signal increases and the phase margin decreases. This poses a problem in that the stability of the system is impaired.

The present invention has been made to solve such problems, and when performing servo control of a motor used for a robot l-arm with two or more axes using software servo, the dead time delay of the speed detection signal due to calculation is An object of the present invention is to realize a servo control device in which the phase margin is reduced and sufficient phase margin is ensured in the servo system.

Means for Solving the Problems> The present invention provides a servo control device that performs speed servo control of N motors (N is an integer of 2 or more) with one device, and provides a cycle for sending control signals to the motors. A fixed period timer that generates a pulse signal (1) with a frequency N times the frequency of the servo cycle, and a fixed period timer that generates a pulse signal (1) with a frequency N times that of the servo cycle, and a fixed period timer that is shifted by one period of this pulse signal based on the pulse signal (1) and is at the same period as the servo cycle. a pulse signal generating means for generating N pulse signals (2), which are provided, receive any one of the N pulse signals (2), and generate a signal according to a detection signal of the rotational position of the motor; A speed detection means for detecting the average rotational speed of the motor in the previous cycle of the pulse signal C), and receiving the pulse signal (1) to determine which pulse signal this pulse signal has occurred in the servo cycle. A servo control device comprising: a number detection means for detecting a number; and a servo calculation means for performing a speed servo control calculation of a motor corresponding to the number detected by the number detection means in synchronization with the pulse signal (1). be.

According to the present invention, the servo cycle is divided according to the number of motors to be controlled, and in each divided period, a control signal for servo control is generated based on the rotational speed of each motor detected in the previous detection cycle. Calculate.

<Example> Hereinafter, the present invention will be explained using the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. 1st
Components in the figure that are the same as those in FIG. 4 are given the same reference numerals.

In the figure, 10 is a fixed-period timer that generates a pulse signal P of 1/2 period of the servo cycle, 11 is a 1-bit binary counter that counts the number of pulses of the pulse signal P, and 12 is a decoded count of the counter 11. It is a decoder that The speed detectors 6 and 7 are operated by the decode signal D2 of the decoder 12.

13 is the command speed V and the speed detection signals V of speed detectors 6 and 7.
, , V2 is a microprocessor that calculates and outputs control signals C, , C2 for servo-controlling motors 1 and 2. The microprocessor 13 starts calculation using the output of the periodic timer 10 as an interrupt signal INT, and also servo-controls the motor 1 or 2 according to the count of the counter 11.

The operation of the device configured in this way will be explained.

FIG. 2 is a time chart of each signal of the device shown in FIG.

The fixed period timer 10 outputs a pulse signal P whose period is 1/2 of the servo cycle T. This signal is converted into a decoded signal D2 by a binary counter 11 and a decoder 12 whose period is equal to the servo cycle and whose phases are shifted from each other by 1/2 period.

The speed detectors 6 and 7 are detected by the decoded signals D1 and D2.
outputs speed detection signals V and v2 alternately every servo cycle.

The output of the fixed-cycle timer 10 also serves as an interrupt signal INT, and the count CO of the counter 11 indicates the number of the motor to be servo-controlled.

The microprocessor 13 constitutes a servo system using software, and calculates and outputs a control signal for the motor numbered by the count CO at the timing given by the interrupt signal INT.

For example, at time t1, the rise of the interrupt signal INT and the count "1" of the counter 11 causes the microprocessor 13 to control the servo motor 2 based on the speed detection signal detected by the speed detector 7 in the previous detection cycle. The calculation of the control signal C1 for control is started. This operation has a period of 1゛,
It will be held in

Similarly, at time t2, calculations for servo-controlling motor 1 start from time t2 and are performed for period T2.

In this way, calculations for servo-controlling motors 1 and 2 are performed within one servo cycle.

FIG. 3 is a flowchart showing the processing procedure of such an operation.

Here, the pulse signal (1) in the claims is the output of the fixed period timer 10, and the pulse signal (2) is the decode signal DI.
, D2, respectively.

In addition, in the embodiment, the case where two motors are controlled has been described, but the number of motors to be controlled may be other than this. For example, when controlling N motors, (
(N is an integer of 3 or more), the fixed-cycle timer 10 generates a pulse signal with a period of 1/N of the servo cycle, and the counter 11
is capable of taking counts of type N11, and the decoder 12
outputs N decoded signals, and N speed detectors are provided.

Effect> According to the present invention, a servo cycle is divided according to the number of motors to be controlled, and in each divided period, a control signal for servo control is generated based on the rotational speed of each motor detected in the previous detection cycle. Since the calculation is performed, the dead time delay of the control signal due to calculation is reduced. This increases the phase margin and improves the stability of the servo system.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams of the operation of the device shown in FIG. 1, and FIG. 4 is a diagram showing an example of the configuration of a conventional servo control device. , FIG. 5 is an explanatory diagram of the operation of the apparatus shown in FIG. 4. 1.2... Motor, 3.4... Rotation detection means, 6°7... Speed detector, 10... Fixed period timer, 11.
... Counter, 12... Decoder, 13... Microprocessor. first

Claims (1)

[Claims] In a servo control device that performs speed servo control of N motors (N is an integer of 2 or more) with one device, a fixed-period timer that generates a pulse signal (1), and N pulse signals, based on the pulse signal (1), that are shifted by one period of this pulse signal and have the same period as the servo cycle. (2); N pulse signal generating means are provided, which receive one of the N pulse signals (2) and detect the previous pulse signal (2) based on a detection signal of the rotational position of the motor; speed detection means for detecting the average rotational speed of the motor in the period of; and the pulse signal (1).
a number detection means for detecting the number of pulse signals generated in the servo cycle by the pulse signal; and a number detection means for detecting the number detected by the number detection means in synchronization with the pulse signal (1). A servo control device comprising: servo calculation means for calculating speed servo control of a corresponding motor.