JPS58140813A - Position controlling system - Google Patents

Abstract

PURPOSE:To compensate a following error, by providing a simulator for the primary delay characteristics of a servo system. CONSTITUTION:A servo motor 13 shows the primary delay characteristics and is unable to have immediate and following revolutions although the distribution pulse CP is produced from an NC device 11. Thus the motor 13 turns with a prescribed delay. Therefore a simulator 17 simulates the transmission characteristics of a servo system and then produces a simulation pulse SP with a time interval approximately equal to the feedback pulse FP. The error between the pulses SP and CP is added to the pulse CP to be supplied to a servo circuit 12. As a result, the delay due to the characteristics of servo system can be compensated. That is, a mobile part 15 moves immediately with generation of the pulse CP and then stops immediately when the generation is discontinued for the pulse CP. Thus it is possible to give compensation to a following error.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position control method, and particularly to a position control method capable of correcting a tracking gA difference.

Normally, in position control in a numerical control system,
The difference between the command value and the actual movement amount is amplified, the servo motor is driven so that the scissor error becomes zero, and the movable wJs is positioned at the command position. FIG. 1 is an explanatory diagram illustrating such position control. In the figure, 11 is a No. device which has a built-in pulse distributor, performs pulse distribution calculation based on a movement command, and generates a command pulse CP. Reference numeral 12 designates a well-known servo circuit, including an error calculation storage unit 12m consisting of a reversible counter cape that calculates and outputs the difference between a command pulse CP and a feedback pulse FP (referred to as a WA difference), which will be described later; A DA converter 12b that generates an analog voltage and an amplifier 12C
The servo motor is driven so that the error becomes zero. 1s is a servo motor such as a DC motor,
14 is a pole screen, 15 is a table as a movable part, and 16 is a position detector such as a pulse distributor that generates one feedback pulse FP every time the table moves by a predetermined amount. In this diagram W11, when a distribution pulse OP is generated from the NO device 11, the distribution pulse is accumulated in the error calculation memory 9128 in the servo circuit 12.

Contents (error) of error calculation storage unit 12a FiDA converter 1
After DA conversion by 2b, the signal is amplified by amplifier 12c and input to the servo motor 15, and the servo motor pvtvs
Turn around. Since the table 15 is commanded to move in the correct direction, the feedback pulse FP on the 1 side is generated from the position detector 16 when the table 15 moves by a predetermined amount. It is input to the error calculation storage unit 1ta and its contents are reduced.

Thereafter, the above O operation is repeated, and during steady state, the error Er stored in the error calculation storage section 12aK is adjusted to a constant steady deviation value, and the servo motor 13. The movable part 15 is instructed to move at a high speed. tll, the steady-state deviation value becomes F/, where the gain of the position control 1llll path is and r is the command pulse series. When a commanded number of distribution pulses (command pulses) CP corresponding to the distance traveled is generated, the distribution pulses are no longer outputted, and are thereafter stored in the error calculation/storage unit 121 and stored in an amount corresponding to 9 errors. If the table 15 moves by this amount, the WIA difference Er becomes zero, and the table 15 is correctly positioned at the target position.

As mentioned above, according to the conventional position side tlnK, the table,
The movable part of the tool can be accurately positioned at the target position.

However, in such conventional position control, a certain delay occurs between the command and the movement of the movable part. In other words, even if a command pulse (distribution pulse CP in Figure 1) is generated, the table does not move immediately but starts moving after a certain delay time, and the table does not stop immediately after the command pulse is stopped. Stops after a certain delay time.

Therefore, when moving a table or tool using simultaneous two-axis or simultaneous three-axis control, if the servo circuit characteristics of each control axis are different, for example, if the gain of each servo circuit is different, the steady-state deviation value will be different. Otherwise, the movable part will no longer move on the command path.

In addition, in gantry type machine tool control that operates two motors synchronously or movement control of large drafting machines,
If the servo characteristics of each motor are different, complete synchronization may not be achieved, resulting in damage to the machine and the inability to perform accurate machining.

From the above, the present invention is based on the difference in steady-state deviation values.
The purpose is to provide a position control system.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Part 21e is a diagram showing the yellow example of this invention.
*The same parts as in the previous example are given the same symbols.

s 1y in 11 is a similator 0 Usually, a servo cage
The motor (direct 111 motor) 15 exhibits first-order lag time operation, and even if the distribution pulse CP is generated, the distribution pulse OP is immediately activated.
It follows K and rotates with a predetermined delay.

Similter 17 simulates the transfer characteristics of the t-po system and uses the feedback pulse xFF and #'! Simulated pulse SP at the same time interval as 11!1! Wow.

Figure 1 is a block diagram of the simulator 17 - e&j
, 17ad A reversible counter that counts up the distributed pulse CP and subtracts the simulated pulse 8P.

17bIIi Akinimulator, 17cFi oscillator that generates a constant frequency pulse Ps, 17d is a generator 17c
This is an addition circuit that adds the count value of the reversible counter 17m to the cumulative value of the accumulator 17b every time a pulse Ps is generated. If the number of bits of the accumulator 17b is n, then if the cumulative value is 2a or more, then m/(70
- The overflow pulse generated by Haruska is output as a simulated pulse SP. life.

C1 oscillation of the contents of reversible counter 17m! The pulse speed of the pulse generated from 117c is fo, the pulse speed of the distribution pulse cP is Fl, and the pulse speed of the simulated pulse SP is Fo.
Then, the following formula holds true.

a ---= Fi −Fo (
11t)・. "-", e = ke 211 (2) (1),
From equation (2), e and Fo are respectively ゎ1 e = -, (1-exp (-k t ))
(31Fo = Fl (1-exp (-k
l)) f41 and the simulator 17 simulate the first-order delay characteristics of the servo system.

Returning to FIG. 2, the first synthesis circuit generates a pulse train having a number of pulses equal to the difference between the number of 18-digit distribution pulses CP and the number of Yokozuna pulses 8PO, 19 is the distribution pulse CP and #11
Synthesizing circuit 1B (this is the 20th combining circuit that combines the D output pulses).

Kyoto, 21st! Servo circuit 12OW in IDq example
The command pulse applied to the A difference calculation storage section 121 is CP
+ (OF-8P) and (CP-8P) compensate for deviations based on the characteristics of the servo system. As soon as the distribution pulse OF passes through the plane, the movable part (table) F! As soon as the distribution pulse OF stops generating, the moving part of the movable part stops.

111E4 Fig.
The same parts as f#ll are given the same reference numerals.

This is an application example of the present invention for synchronizing two BmFi 15 and 1B'. The same parts as in FIG. 4 are given the same symbols #i. Also 12,
15 and 14 are connected to the water circuit 12, the servo motor 11, and the position detector 14, respectively (not shown in the figure).

In FIG. 5, the motor 13' is rotating with a predetermined tracking error with respect to the distribution pulse OP. However, motor 1
5 rotates without delaying the feedback pulse FP because the system incorporates a 7-mirror generator 17, first and second synthesis circuits. In other words, the motors 1s' and 15 rotate synchronously.

According to the present invention, it is possible to eliminate the tracking error even if there is a steady deviation, it is possible to reliably perform synchronized operation of two motors, and furthermore, it is possible to reduce the degree of machining glaze in simultaneous n-axis control. can be improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram for explaining conventional position control, Fig. 2 is an explanatory diagram for explaining position control according to the present invention, Fig. 5 is a block diagram of a simulator, and Fig. 4 is another embodiment of the present invention. The block diagram, wIJ5 diagram, is a block diagram for explaining the present invention in detail. 11...NO device%12...Servo circuit, 15...
Servo motor, 14...Position detector, 17...Shi
z rate. Patent applicant Fujitsu Fanuc Co., Ltd. Attorney: Mr. Tsuji, 2 persons

Claims (1)

[Claims] In the position control method described above, the method includes a position control circuit that increases the error between the command value and the actual movement amount and drives a servo motor to position the movable part at the command position so that the error becomes zero. A simulator that simulates the transmission lf# characteristic of the position control circuit is provided, a command value is input to the armpit controller, an error between the simulator output and the command value is generated, and the error is added to the command value. A position control method that uses the input to the four position-side circuits as the 4I image.