JPS5936817A - Restoring method to origin - Google Patents

Abstract

PURPOSE:To prevent a moving part from twisting and to improve working accuracy by previously setting up the origins of the 1st and 2nd axes synchronously to stop the moving part precisely and then controlling the synchronous operation. CONSTITUTION:In a gantry type working machine GMC or the like, moving parts are driven in the same direction by two servo motors M1. The original positions of the 1st and 2nd axes previously set up synchronously each other. An origin restoring dog DG is fitted to the machine moving part and a speed decreasing limit switch DLS is attached close to the origin of a fixing part. In the origin restoration mode, the motors M1 are driven through a reversible counter RCN1, etc. by a pulse CP from an NC device 1. If the dog DC depresses the switch DLS, the speed of a pulse string CP from the NC device 1 is reduced by a speed decreasing signal *DEC, and after a prescribed time, te speed of the motors M1 becomes zero. Subsequently, the moving parts are moved to the origins by a restoration command to position the moving parts.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an origin squid return system, which is particularly useful in Gantt-type machine tools, large-scale drafting machines, etc., by rotating two motors, m 1 and 2, synchronously. In gantry type machine tools, large drafting machines, etc., the movable parts are driven in the same direction by two motors.

In this case, it is necessary to maintain a constant positional relationship between the synchronously controlled axes and rotate the two motors synchronously.If they are not rotated synchronously, the positional relationship between the axes will shift and the moving parts Crabs such as twisting occur, and work accuracy.

Drafting accuracy decreases. Furthermore, in the worst case, the machine may be damaged.

For this reason, various methods for synchronously rotating two motors have been proposed and put into practical use. FIG. 1 is a block diagram for realizing such a conventional synchronous control method. In the figure, reference numeral 1 denotes a numerical control device (hereinafter referred to as an NC device) which has a pulse distributor inside and generates a pulse train having a frequency corresponding to a commanded speed based on a command from a paper tape or the like (not shown).

Note that this pulse train becomes a position command for each motor.

2 is the servo circuit of one motor, and the position f deviation signal P
D, a position control circuit 2a that generates a position deviation signal (speed command) PD, a speed control circuit 2b that generates a drive voltage according to the difference between the actual speed V of the motor M, and the motor M,
It has a tacho generator 2c that generates a voltage V corresponding to the actual speed of the motor M, a pulse coder 2d that generates one feedback pulse FP every time the motor M rotates by a predetermined angle, and a position feedback loop PF. velocity feedback loop VF,
is formed. Now, the position control circuit 2a includes a reversible counter RV, a DA converter DAC, and an amplifier AM.
It has P. And this reversible counter R
V counts up every time a pulse PCMD, which is a position command, is generated, and counts down every time a feedback pulse FP is generated. That is, the contents of the reversible counter RV are proportional to the positional deviation.

The contents of this reversible counter RV are transferred to the DA converter D.
The AC signal is converted into an analog value, then amplified and output as a position deviation signal PD. Speed control circuit 2
b generates a drive voltage according to the difference between the speed command PDI and the actual speed signal vI, and controls the motor M so that the drive voltage becomes zero.
, to drive. With the above control, in a steady state, the positional deviation is at a steady value, and the shimotor M1 rotates at a constant speed.

3 is the other motor M! This servo circuit has the same configuration as servo circuit 1. In addition, 3a is the position deviation signal PD
, a position control circuit that generates , 3b is a position deviation signal PD,
and the actual speed V of the motor My, 5C is a tacho generator that generates a voltage Vt according to the actual speed of the motor Ml, and 5d is a motor M
, generates one feedback node FPI every time , rotates by a predetermined angle, VF is a velocity feedback loop, PF is a position feedback loop, Hv is a reversible counter, DACt is a DA converter, AMP! is an amplifier.

4 is a synchronization correction circuit, which includes an error voltage generator 4a that generates a voltage EV proportional to the difference in the number of pulses generated from the pulse coders 2d and 5d, and an amplifier 4 that amplifies the error voltage EV.
It has b. In addition, 4c is the difference voltage EV of the motor M.
This is an adder that adds to the position deviation voltage PDV of .

If there is no synchronization between the axes and the motors M and My rotate in complete synchronization, the error voltage generator 4a
The output of is zero and no correction can be made. However, the synchronous rotational force of the motors M, , M, <1" is 2. If one of the motors rotates faster, the pulses generated by the Norse coaters 2d and 3d75λ A difference occurs in speed, and the error voltage generator 4a generates an error voltage EV having an amplitude corresponding to the speed difference and a sign corresponding to the magnitude of the rotational speed of the motors M, . This sign is positive if Vl > Vt, V,
(vt becomes negative. 4L means that the position deviation voltage PDV of the servo circuit 6 is corrected according to the speed difference between both Tanabata. That is, if Vl>Vl, the position fRft+lI' is the output of the M1 circuit 3a. As the voltage increases, the speed of motor M, becomes v,-
It rises to the point where it becomes a shield, and Vl < Vl, and it becomes fff
The output voltage of the tfli control circuit 5a decreases, and the speed of the motor λ11 decreases to -v. I-hiyo Shimota M.

and motor M will rotate in synchronization.

By the way, according to Figure 1, the motors M, M,
The power that can rotate + 21FIII IIη
Nomo Lizune.

It is not possible to reduce the (period slippage) to zero. In other words, if a positional deviation has occurred before synchronous control, the method shown in FIG. 1 will not even eliminate the positional deviation.

For this reason, unreasonable force is constantly applied to the machine when the machine moves twice due to misalignment, and this also reduces the ease of machining.

Now, Detection 4, which can detect the absolute position of a machine like a resolver or absolute encoder! In a system that uses progress to detect the position of the first and second axes, it is easy to recognize the positional deviation between the axes. How synchronized are they when the power is turned on? 11] It is impossible to know if there is a positional deviation between the two controlled axes.

From the above, the present invention is a synchronous control system that moves a movable object in one direction by rotating two motors in synchronization, and is synchronously controlled in a synchronous control system that uses a nose coder as a detector. It is an object of the present invention to provide a home return method that can set the positional deviation between two axes to a value that does not cause twisting force on a movable object and does not adversely affect machining accuracy.

FIG. 2 is a time chart for realizing the origin return control method according to the present invention. Note that the origin positions for the first and second axes are set in advance so as not to be out of synchronization with each other. Now, a dog for returning to the origin is provided in the movable part of the machine, and an IJ switch for deceleration is provided in common for each axis near the origin of the fixed part of the machine. If you use the J+% production board top point return switch (not shown) to enter the home return mode,
A fast forward pulse is generated by the NC device, the first and second motors are rotated by this fast forward pulse, and the mechanical movable part moves toward the origin at a fast forward speed (FH speed).

Then, time 1. When the dog reaches near the origin and steps on the deceleration limit switch, the deceleration signal %DEC changes to 1°.
°. Due to the rise of this deceleration signal -XI)EC, N
The speed of the pulse train output from the C device is decelerated, and as a result, the home return speed (first and second motor speeds) is decelerated and reaches zero after a predetermined time (time 1).

That is, the rotational speeds of the first and second motors become zero.

Now, until time t after the start of home return, the @1 and second motors are controlled in exactly the same way, but at time t! After that, each is controlled independently. That is, time t! The rear first and second motors both rotate at low speed VL, and the mechanical movable part moves at low speed toward the origin. Then, at time t3, the deceleration limit switch / switch separates from the dog and restores.kDEC=”
ON), then further move towards the origin of the first and second axes,
At time t, the first near-zero signal NZ approaches the origin of the first axis, and at time t11, the second near-zero signal NZ approaches the origin of the second axis. Now, after the first near-zero signal NZ is generated, the numerical control device selects the first grid position (grid point position...grid signal GS).
, occurs) is the origin of the first axis, and the first grid position # after the second near-zero signal NZ is generated (where the grid signal GS is generated) is regarded as the origin of the second axis. Stop the rotation of the first motor at time t,
At time t, the rotation of the second motor is stopped and the return of the mechanical movable part to the origin is completed.

FIG. 3 is a block diagram of an embodiment of the present invention, in which 1 is an NC device, 2 is a servo circuit for the first motor, 5 is a servo circuit for the second servo motor hook, and 4 is a synchronization correction circuit. still,
The servo circuit 2 has the same circuit configuration as the servo circuit 3, and the operation of the servo circuit 2 will be mainly described in detail below, but the servo circuit 5 also operates in the same manner.

When the home return command ZRN is “ON”, the position command
Command pulses CP are sent to the servo circuits 2.3 from a pulse distributor (not shown) of the C device. Every time a command pulse is input, the reversible counter RC of the first servo circuit 2
N counts this, and a voltage proportional to the count is generated from the digital-to-analog converter DAC.

This voltage becomes the speed command PD and is compared with the actual speed V generated from the tachometer TCM, and the difference is amplified by the power amplifier AMP to rotate the servo motor M.
For example, a gun) drives the first axis of the IJ type machine tool GMC. Similarly, the second axis is driven by the servo circuit 5, and the movable part of the gantry machine tool moves. Servo motor M
, the rotary encoder RE rotates. The rotary encoder RE is configured to generate a signal FBP every time it rotates by a predetermined amount, and to generate a one-rotation signal PC every time it rotates. Note that this one rotation signal generation position is lattice point -t'6. Thus, the rotation amount of the servo motor M is detected by the rotary encoder RE, and the rotation amount is input as a feedback pulse FBP to the subtraction terminal of the first reversible counter RCN, and the contents of the counter are subtracted. When the command pulses CP stop arriving and a number of foot pulses FBP equal to the number of command pulses are generated, the content of the first pulse counter RCN becomes zero, and the servo motor M.

stops its rotation and completes positioning. In addition, the synchronous correction circuit 4 and the synthesis circuit ADDll- are operated so that the first and second servo motors rotate in synchronization. For details, please refer to the operation of the synchronous correction circuit 4 and adder 4C in Fig. 1. .

By the way, the command generated from the NC device 1] (RusCpH
-tAntogame)AN, the second reversible counter r
usN, is added to the addition terminal and counted. or,
After the power is turned on, the flip-flop FF is reset until the first one-rotation signal PC is generated, so the feedback pulse FBP generated from the rotary encoders R and E is sent to the second reversible counter via the AND gate AN. It is input to the subtraction terminal of RCN, and the contents of the counter are subtracted. However, when the first one-rotation signal is generated after the power is turned on, the second reversible counter RCN! The contents indicate the number of command pulses until the first one-rotation pulse PC is generated after the power is turned on, minus the amount of movement A from the motor stop position until the first one-rotation pulse PC is generated.

Since the capacity of the second reversible counter RCN is equal to the number of feedback pulses FBP generated from the rotary encoder during one revolution of the rotary encoder RE, the second reversible counter RCN will be used as a command from now on. If the pulses are counted and their content becomes zero, the commanded position is exactly at the grid point.

Next, the return-to-origin command ZRN becomes 1”, and the clip
Since the flops FF and FF are initially reset and the AND gate AN is open, the return-to-origin pulse given from the NC device 1 is applied to the first and second reversible counters RCN r via the gate AN.

RCN! , and the movable part moves in the direction of the origin (in the direction of the arrow) according to the same operation as the above-mentioned normal positioning. The movable part reaches the vicinity of the origin and the nine-dog DG is attached to the movable part at time 1. When the deceleration limit switch DLS is stepped on (see FIG. 2), a deceleration signal -%DEC is generated, and the AND gate AN is opened and the flip-flop FF is set. At the same time, the deceleration signal -XDEC is supplied to the NC device 1 to decelerate the speed of the home return pulse. Thus,
The movable part moves toward the origin at low speed, and after a predetermined time (
It becomes zero at time t, ). As a result, switch SW
Then, a low-speed (FL) return-to-home pulse is generated from the NC device a1, and the movable object moves toward the home at low speed, and at time ts, the deceleration limit switch leaves the dog and returns to normal operation (-4DEC= "0"). Thereafter, the first and second servo motors rotate at low speed, and the movable part moves toward the origin of the first and @2 axes. Then, at time t4, the first smell
When the axis approaches the origin and the first near-zero signal NZ is generated from the magnetic sensor MGS, the output of the AND gate AN becomes 1°, and 9FF4 is set. After FF is set, when the content of the second reversible counter RCN becomes zero, the output power of the AND gate ANs becomes "1", FF is set, and AN is closed. Therefore, the origin return pulse of the NC device 1 is no longer supplied to the first and second reversible counters RCN, .about.RCN. After all, the command position when FF is set is at the grid point,
Thereafter, the first axis of the movable part moves by the deviation between the number of command pulses and the number of feedback pulses stored in the first reversible counter RCN, and stops at time t6, and at this time, the movable part is correctly positioned at the grid point. It is often positioned.

In parallel with this, at time t, the movable object approaches the origin of the second axis and a second near-zero signal NZ,
occurs, it operates in the same way as the first axis and reaches time t7.
Stop at .

As described above, according to the present invention, it is possible to accurately stop the movable portion at the origin of the first axis and the origin of the second axis, which are set in advance so as not to be out of synchronization.

If you perform synchronous operation control from this stopped state, synchronization will not occur, and unreasonable force will not be applied to the machine.
Without this, you can improve the accuracy of your work.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for realizing a conventional synchronous control system, FIG. 2 is a time chart of the present invention, and FIG. 6 is a block diagram of an embodiment of the present invention. 1... NC device, 2.3... Servo circuit, 4...
Synchronous correction circuit patent applicant Fanuc Co., Ltd. agent Patent attorney Tsuji Tsuji (one other person)

Claims (1)

[Claims] By rotating the first and second motors synchronously,
In the origin return method for a movable object that is moved in the direction, the origin positions for the first and second axes are set in advance in the direction in which the movable object moves by synchronous control so that they do not deviate from synchronization with each other, and the origin return mode is set. The first and second motors are rotated by the pulse train generated at the position to move the movable object toward the origin position of each axis, and the moving speed is reduced by a deceleration signal generated near the origin, so that the moving speed includes zero. After reaching a predetermined speed, the first and second motors are independently controlled, and when the origin position of each axis is reached, the rotation of the corresponding motor is stopped to return to the origin. method.