JPH06161560A - Servo system - Google Patents

Abstract

PURPOSE:To provide the servo system for easily improving the accuracy of circular arc interpolation at an inflection point with simple processing when switching an event during circular arc interpolation. CONSTITUTION:Since the responsiveness of a servo motor MX or the like is improved by increasing the position loop gains KPX and KPY at the inflection point when switching the event during circular arc interpolation, namely, near the inversion of the turning direction of the servo motor MX or the like, the accuracy of circular arc interpolation can be prevented from getting adverse such as followup delay caused by the frictional force of a machine or disabling the sufficient drive of the machine with the gain lack of amplifier parts 9X and 9Y caused by a fine velocity command.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo device for servo-controlling a moving body.

[0002]

2. Description of the Related Art Conventionally, a moving body, for example, a tool of a machine tool is controlled by interpolating two servo motors for driving an X-axis and driving a Y-axis. During the interpolation control, the servo motor is driven with the normally set constant position loop gain.

[0003]

However, when the circular interpolation is performed with the usual constant position loop gain, the rotation of the servomotor becomes slow and reverses at the inflection point at the time of the circular arc event switching. I can not follow sufficiently with frictional force,
Due to the delay, the accuracy of the circular interpolation may be deteriorated, or the gain may not be sufficient in the low speed region where the amplifying unit is a very small speed input and the servo motor may not be rotated sufficiently, and similarly the accuracy of the circular interpolation may be deteriorated. .

In order to solve these problems, a servo device is known in which a correction torque command is separately input to the amplifying section to improve the accuracy of circular interpolation, but it takes time to calculate the correction input. Alternatively, when the amplifier is independent as the servo drive device, it is necessary to prepare an extra signal input in order to separately apply the correction input.

Further, in the numerical control device disclosed in Japanese Patent Laid-Open No. 63-231602, the NC program is decoded in advance by the command unit, and the inflection point and its vicinity at the time of arc event switching are foreseen in advance. Then, when the tool reaches the specific area during circular interpolation, it has a function to set the position loop gain to an appropriate value to improve the accuracy of circular interpolation, but also in this case the processing is complicated. However, there is a problem that the calculation process takes time, and it is necessary to rely on hardware capable of high-speed processing.

The present invention has been made in order to solve the above-mentioned problems, and provides a servo device which improves the circular interpolation accuracy at the inflection point at the time of event switching during circular interpolation by a simple process. To provide.

[0007]

In order to achieve this object, a servo apparatus of the present invention comprises a plurality of servo motors and a command section for outputting a movement command signal for driving these servo motors in a predetermined relationship. An interpolating section that performs a predetermined interpolation based on the signal type of the movement command signal; a distributing section that performs a pulse distribution by applying a predetermined acceleration / deceleration time constant to the interpolation signal interpolated by the interpolation section; A comparing unit that compares the distributing unit pulse distributed by the distributing unit and the feedback pulse of the servo motor, and generates a pool pulse that is a position error;
When the interpolation in the interpolation unit is circular interpolation, the direction reversal detection unit that detects the vicinity of reversal of the rotation direction of the servo motor and the direction reversal detection unit that detects the vicinity of reversal based on the accumulated pulse generated by the comparison unit. As a result, a position loop gain setting unit that sets an appropriate position loop gain, a speed command that calculates a speed command based on the accumulated pulse generated by the comparison unit and the position loop gain set by the position loop gain setting unit An arithmetic unit and an amplification unit that drives the servo motor based on the speed command are provided.

[0008]

In the servo apparatus of the present invention having the above structure,
While grasping that circular interpolation is being performed in the command unit that outputs the movement command signal, when interpolation in the interpolation unit that performs predetermined interpolation based on the signal type of the movement command signal is circular interpolation,
A direction reversal detection unit that detects the accumulated pulse generated by the comparison unit detects that it is near the inversion of the rotation direction of the servo motor in the vicinity of the inflection point at the time of arc event switching. The position loop gain setting unit for setting an appropriate position loop gain thereby sets the position loop gain higher than the normal position loop gain, and based on the position loop gain, the speed command for calculating the speed command of the servo motor Section, the speed command to the servo motor near the inflection point during arc event switching is calculated higher than the speed command other than near the inflection point during arc event switching, and the calculated speed command is sent to the amplifier section. Is entered.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the servo apparatus of the present invention has servo motors MX and M for the X-axis and the Y-axis, respectively.
Y, and corresponding to the servomotors MX and MY, the distribution units 3X and 3Y, the comparison units 4X and 4Y, the direction inversion detection units 6X and 6Y, and the position loop gain setting units 7X and 7 are provided.
It has Y, speed command calculation units 8X and 8Y, and amplification units 9X and 9Y. Further, the distribution units 3X and 3Y are both connected to the interpolation unit 2, and the interpolation unit 2 is connected to the command unit 1.

From the servomotors MX and MY, feedback pulses are amplified as position feedback in the X-axis direction and Y-axis direction to the comparison units 4X and 4Y, respectively, and a feedback speed signal is amplified as speed feedback in the X-axis direction and Y-axis direction. Part 9
Returned to X and 9Y respectively.

The command unit 1 reads the contents of the NC program 10 and reads a table or a tool (not shown) of a machine tool.
A command signal is output to the interpolator 2 in order to make a linear or circular motion.

The interpolation unit 2 interpolates the input command signal, generates interpolation data for the X axis and the Y axis, and outputs the interpolation data to the distribution units 3X, 3Y. Further, during the circular interpolation, a signal indicating that the circular interpolation is being performed is output to the direction inversion detection units 6X and 6Y.

The distribution unit 3 converts the interpolation data for the X-axis and the Y-axis into predetermined distribution pulses for each unit time,
The distribution pulse corresponding to the X axis is output to the comparison unit 4X, and the distribution pulse corresponding to the Y axis is output to the comparison unit 4Y.

The comparators 4X and 4Y compare the distributed pulses from the distributors 3X and 3Y with the feedback pulses from the servomotors MX and MY, and collect pulses εx which are position errors in the X-axis direction and the Y-axis direction. , Εy is generated.

The direction reversal detection units 6X and 6Y generate the accumulated pulse ε generated by the comparison units 4X and 4Y when the interpolation unit 2 outputs a signal indicating that the circular interpolation is being performed.
By observing x and εy, it is detected that εx and εy are smaller than a certain value, so that the vicinity of the inflection point at the time of event switching during circular arc interpolation, that is, the point where the rotation directions of the servomotors MX and MY are reversed. Position loop gain setting units 7X and 7Y
Instructs to change the position loop gain.

The position loop gain setting units 7X and 7Y receive an instruction to change the position loop gain instructed by the direction reversal detection units 6X and 6Y, and the accumulated pulses εx and εy generated in the comparison units 4X and 4Y. Based on, the appropriate position loop gains K _PX and K _PY are calculated and set.

The speed command calculators 8X and 8Y are provided with position pulse gains K _PX and K _PY which are appropriately set by the accumulated pulses εx and εy generated by the comparators 4X and 4Y and the position loop gain changing units 7X and 7Y. Based on, the speed command is calculated (multiplied) to generate.

The amplifiers 9X and 9Y amplify and output the speed commands output from the speed command calculators 8X and 8Y,
The servo motors MX and MY are driven.

By operating in this manner, the inflection point at the time of event switching during circular interpolation, that is, the servomotor M
At the point where the rotation directions of X and MY are reversed, the servo motor M
Since the responsiveness of X and MY is increased by increasing the position loop gains K _PX and K _PY , the tracking delay due to the frictional force of the machine and the insufficient gain of the amplifiers 9X and 9Y due to the minute speed command will cause the machine to operate sufficiently. It is possible to prevent the accuracy of the circular interpolation from being deteriorated, such as being unable to drive.

The position loop gain changing units 7X and 7Y
As an example of a method of setting the appropriate position loop gains K _PX and K _PY by, as shown in FIG. 2, when | ε |> A, K _P = K _{P0 when} A ≧ | ε |> B, K _P = When K _P α B ≧ | ε | ≧ 0, K _P = K _P β K _P0 <K _P α <K _P β ε; Droop pulse A; Direction reversal detection level constant B; Gain two-step change level constant K _P0 : Normal position loop gain K _P α, K _P β; There is a changed position loop gain.

Alternatively, in consideration of the inversion information of the drive axis of the servomotor M, as shown in FIGS. 3 (a) and 3 (b), ε: positive value → negative value A> ε ≧ 0 Case K _P = K _P α, 0>ε> -A K _P = K _P β, | ε |> A K _P = K _P0 ε: Negative value → positive value A> ε ≧ 0 Case K _P = K _P β, 0>ε> -A K _P = K _P α, | ε |> A K _P = K _P0 ε; Pool pulse A; Direction reversal detection level constant K _P0 ; Ordinary position loop gain K _P α, K _P β; There is a setting method for setting the changed position loop gain.

[0023]

As is apparent from the above description, according to the servo device of the present invention, in the vicinity of the inflection point at the time of event switching during circular interpolation, that is, the point where the rotation direction of the servo motor is reversed, Since the response of the servo motor is enhanced by increasing the position loop gain, the servo motor can operate swiftly to improve the response, and the tracking delay of the machine due to the frictional force of the machine and the amplification by the minute speed command It is possible to prevent the accuracy of circular interpolation from deteriorating, such as when the machine cannot be driven sufficiently due to insufficient gain in the part.

[Brief description of drawings]

FIG. 1 is a block diagram of a servo device embodying the present invention.

FIG. 2 is a diagram showing an example of a position loop gain changing state in a position loop gain changing unit of the servo apparatus of the present embodiment.

FIG. 3 is a diagram showing an example of a position loop gain changing state in a position loop gain changing unit of the servo apparatus of the present embodiment.

[Explanation of symbols]

 1 command section 2 interpolation section 3X, 3Y distribution section 4X, 4Y comparison section 6X, 6Y direction reversal detection section 7X, 7Y position loop gain change section 8X, 8Y speed command calculation section 9X, 9Y amplification section MX, MY servo motor

Claims (1)

[Claims] 1. A plurality of servo motors, a command unit for outputting a movement command signal for driving these servo motors in a predetermined relationship, and an interpolation for performing a predetermined interpolation based on the signal type of the movement command signal. A distribution unit for applying a predetermined acceleration / deceleration time constant to the interpolation signal interpolated by the interpolation unit for pulse distribution, and a distribution unit pulse distributed by the distribution unit and a feedback pulse of the servo motor. A comparison unit that compares and generates a stagnant pulse that is a position error, and when the interpolation in the interpolation unit is circular interpolation, a direction that detects the vicinity of the reversal of the rotation direction of the servo motor by the stagnant pulse generated by the comparison unit. By the inversion detection unit and the direction inversion detection unit detecting the vicinity of the inversion,
A position loop gain setting unit that sets an appropriate position loop gain, a speed command calculation unit that calculates a speed command based on the accumulated pulse generated by the comparison unit and the position loop gain set by the position loop gain setting unit. A servo device that drives the servo motor based on the speed command.