JPH081481A - Position controller for movable body - Google Patents

Abstract

PURPOSE:To quickly stop a movable body when an emergency stop signal is inputted. CONSTITUTION:A position controller is provided with a sequencer 13 which resets a deviation counter 2 when an emergency stop switch 14 is operated and de-energizes a relay 15 after the fixed time. When the deviation counter 2 is reset, a servomotor 4 is stopped by means of a driving circuit 11, and when the relay 15 is de-energized, contacts r2-r5 of the relay 15 are released and supply from an electric power source to the deviation counter 2, a D/A converter 8, a subtracter 9, a servo-amplifier 10, a driving circuit 11, and an F/V converter 12 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling the position of a movable body provided in a machine tool or the like, and more particularly to means for emergency stopping the movable body.

[0002]

2. Description of the Related Art A sensor for detecting the amount of displacement of a movable body which is displaced by a servo actuator as the number of pulses, and a difference between the number of command pulses and the number of output pulses of the sensor as position deviation of the movable body. A position control device including a deviation counter and an actuator driving unit that drives the servo actuator in the direction in which the position deviation disappears based on the output of the deviation counter is in practical use.

By the way, in an NC machine tool that performs machining such as cutting while moving a movable body (for example, a movable table) on which a tool or a workpiece is set in a predetermined direction, normal machining is caused by some factor. It may be difficult, but in such a case, it is necessary to stop the feeding of the movable body.

Therefore, in the above position control device applied to such a machine tool, an emergency stop switch that is operated when normal machining becomes difficult, and the actuator drive when the switch is operated. Means for stopping the supply of power to the means.

[0005]

Even if the supply of power to the actuator driving means is stopped, the servo actuator does not stop instantaneously but continues to operate until its inertial force disappears. Therefore, the movable body stops after coasting a certain distance from the time of operating the emergency stop switch.

As described above, in the conventional control device, the servo actuator cannot be promptly stopped at the time of operating the emergency stop switch. Therefore, abnormal machining is performed before the movable body is completely stopped. There was a case where the process was continued and the work piece became irreproducible.

In view of the above situation, an object of the present invention is to provide a position control device for a movable body which can quickly stop a servo actuator when an emergency stop signal is input.

[0008]

According to the present invention, a sensor for detecting the displacement amount of a movable body, which is displaced by a servo actuator, as the number of pulses, and a difference between the number of command pulses and the number of output pulses of the sensor. An emergency stop signal is provided in a positioning control device including a deviation counter that detects a position deviation of the movable body, and an actuator drive unit that drives the servo actuator in a direction in which the position deviation disappears based on an output of the deviation counter. Is provided when the deviation counter is reset.

[0009]

Operation: The deviation counter is reset when the emergency stop signal is input. Resetting the deviation counter is to force the position deviation to zero. Therefore, the actuator driving means acts to lock the movable body at the present position, and as a result, the movable body is stopped very quickly.

[0010]

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

FIG. 1 shows an embodiment of the present invention applied to a machine tool for chamfering a cylinder port of a two-cycle engine.

In FIG. 1, the NC controller 1 outputs a normal rotation command pulse signal or a reverse rotation command pulse signal composed of a pulse train, and the normal rotation command pulse signal is output to the up input terminal of the deviation counter 2 The signals are applied to the down input terminals of the counter 2, respectively.

While the pulse encoder 3 makes one rotation,
It is a known pulse generating means for outputting a large number (for example, 1000) of A-phase pulse signals and B-phase pulse signals whose phases are shifted by 90 degrees.

The pulse encoder 3 is rotated by a servo motor 4 which is a servo actuator. On the other hand, the servomotor 4 rotates the feed screw 5 of the NC machine tool to displace the movable table 6 screwed on the screw 5 in the left-right direction. Therefore, the number of pulse signals output from the encoder 3 depends on the movable table 6
It corresponds to the actual displacement amount of.

A tool for performing the chamfering process or a cylinder of a two-cycle engine as a workpiece is set on the movable table 6.

The direction discriminating circuit 7 is based on the phase difference between the A-phase pulse signal and the B-phase pulse signal given from the pulse encoder 3, and the rotation direction of the servomotor 4, that is,
The displacement direction of the movable table 6 is determined. Then, at the time of forward rotation and reverse rotation of the motor 4, the same number of normal rotation pulse signals and reverse rotation pulse signals as the A and B phase pulse signals are generated, and the normal rotation pulse signals are input to the down input terminal of the deviation counter 2. Further, a reverse rotation pulse signal is applied to each of the up input terminals of the counter 2.

Since the structure of the direction discriminating circuit 7 is well known, a detailed description thereof will be omitted.

The command pulse signal input from the NC controller 1 to the deviation counter 2 is sent to the movable table 6.
Is a position command signal for moving from one position to the next target position. On the other hand, the pulse signal input from the direction discrimination circuit 7 to the deviation counter 2 is a position feedback signal indicating the actual displacement amount of the movable table 6. Is. Therefore, the count value of the deviation counter 2 is the movable table 6
Position deviation.

The output of the deviation counter 2 indicating the position deviation is D / A converted by the D / A converter 8 and then subtracted by the subtracter 9.
It is applied to the servo motor 4 via the servo amplifier 10 and the drive circuit 11, and as a result, the movable table 6 is moved in the direction in which the position deviation becomes zero.

The output signal of the frequency / voltage converter 12 for converting the frequency of the output pulse of the encoder 3 into a voltage is applied to the other input terminal of the subtractor 9 as a speed feedback signal.

The sequencer 13 has an input terminal X1 connected to a normally-closed emergency stop switch 14 and an output terminal Y thereof.
Reference numeral 1 is connected to the relay 15, and its output terminal Y2 is connected to the clear terminal of the deviation counter 2.

The relay 15 has its contact point r1 connected to the emergency stop input terminal of the NC controller 1. The contact r2 has the deviation counter 2, the D / A converter 8, the subtractor 9, and the servo amplifier 1 which are commonly connected to each other.
0 and the power supply terminals of the F / V converter 12 and the DC power supply 16 are interposed, and their contacts r3, r4 and r5 are the power supply terminals of the drive circuit and the AC power supply 1 respectively.
7, U-, V-, and W-phase output terminals, respectively.

During operation of the machine tool, the sequencer 13 energizes the relay 15 to close the contacts r1 to r5. As a result, power is supplied to the deviation counter 2, the D / A converter 8, the subtractor 9, the servo amplifier 10, the F / V converter 12 and the drive circuit 11, respectively. Positioning control of the movable table 6 is executed based on the forward rotation command pulse signal or the reverse rotation command pulse signal that is output.

When the workpiece is abnormally machined due to some cause during the operation of the machine tool, the operator operates the emergency stop switch 14 to open it. As a result, the input terminal X1 of the sequencer 13 is opened. A signal of logic level "L" as shown in FIG.

In response to this, the sequencer 13 resets the deviation counter 2 by outputting from the output terminal Y2 the reset signal shown in FIG.
At the same time, a built-in timer (not shown) is started.

The opened emergency stop switch 14 remains open unless its knob is closed.

When the deviation counter 2 is reset, that is, the position deviation of the movable table 6 is indicated by the counter 2
When the count value of is forced to zero, the value of the speed command signal input to the subtractor 9 becomes zero. Therefore, the drive circuit 11
Acts to make the speed of the servomotor 4 zero, in other words, to lock the movable table 6 at the current position.

As described above, in this embodiment, when the emergency stop switch 14 is opened, the servo operation is performed so as to prevent the movable table 6 from moving, that is, the servo motor 4 is not brought into a free state. So the table 6
Can be decelerated rapidly and stopped immediately.

On the other hand, the timer built in the sequencer 13 outputs a signal of logic level "L" to the output terminal Y1 after the time t has been counted, as shown in FIG. 2 (b). As a result, the relay 15 is deenergized, and the contacts r1 to r5 that have been closed until then are opened.

By opening the contact r1 of the relay 15, the logic level of the emergency stop input terminal of the NC controller 1 is changed from "H" to "L". Therefore, the NC controller 1 stops the output of the command signal based on this change.

Further, by opening the contacts r2 to r5, the supply of power to the deviation counter 2, the D / A converter 8, the subtractor 9, the servo amplifier 10, the drive circuit 11 and the F / V converter 12 is stopped. .

The time t of the timer is set to be equal to or longer than the time (for example, several ms) required for the movable table 6 to completely stop after the emergency stop switch 14 is opened. Therefore, according to this embodiment, after the movable table 6 is stopped, the output of the command signal and the supply of power to the elements 2, 8 and 9 to 12 are automatically stopped, resulting in noise and the like. Malfunction of each element is prevented.

When the emergency stop switch 14 is closed, the sequencer 13 energizes the relay 15 again, and the input of the reset signal to the deviation counter 2 is stopped. Therefore, by operating a start switch (not shown), the machine tool can be operated again.

By the way, the sequencer 13 is provided as a means for controlling the accessory mechanism of the machine tool, and, for example, a switch signal for instructing clamping or unclamping of the workpiece, or an instruction for opening / closing the door of the machine tool. A switch signal or the like is input to control an actuator (for example, an air cylinder) for clamping, opening and closing a door, or the like.

In the above-mentioned embodiment, the sequencer 13 is provided with the reset means for the deviation counter 2 and the respective elements 2,
Since it is used as a means for stopping the power supply to the power supply units 8, 9 to 12, the cost can be reduced and the configuration can be simplified. Of course, it is of course possible to provide a dedicated means for resetting the deviation counter 2 and for stopping the power supply to the elements 2, 8, 9 to 12.

In the above embodiment, the power supply to each of the elements 2, 8 and 9 to 12 is stopped at the time when the timer finishes measuring time, but the power supply to only the drive circuit 11 is stopped. However, it is sufficient for practical use.
This is because even if a signal based on noise is output from each element located in the preceding stage of the drive circuit 11, there is no possibility that the servo motor 4 will operate if the drive circuit 11 is powered off. is there.

If sufficient measures are taken against noise, it is possible to omit stopping the power supply to the drive circuit 11.

The embodiment shown in FIG. 1 controls one axis of a multi-axis machine tool, but the other axes of the machine tool are also controlled by a control system having the same configuration as this embodiment. In the above embodiment, the emergency stop signal generated based on the operation of the switch 14 is input to the sequencer 13.
It is also possible to detect the state of the emergency stop with an appropriate sensor and input the emergency stop signal output from this sensor to the sequencer 13. Further, the control device of the above-described embodiment can be applied to the position control of the movable table in machines other than machine tools.

[0039]

According to the present invention, the deviation counter is reset at the time of inputting the emergency stop signal, that is, the position deviation, which is the count value of the counter, is forcibly set to zero. The servo actuator and the movable body can be rapidly decelerated and stopped quickly.

Therefore, if the present invention is applied to the control of an NC machine tool that performs machining such as cutting while moving a movable body on which a tool or a work piece is set in a predetermined direction, it can be instantaneously input at the time of inputting an emergency stop signal. It is possible to avoid the situation where the movable body is stopped and the workpiece becomes unreproducible.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the sequencer.

[Explanation of symbols]

 1 NC Controller 2 Deviation Counter 3 Pulse Encoder 4 Servo Motor 6 Movable Table 7 Direction Discrimination Circuit 10 Servo Amplifier 11 Drive Circuit 13 Sequencer 14 Emergency Stop Switch 15 Relay

Claims (2)

[Claims] 1. A sensor for detecting a displacement amount of a movable body displaced by a servo actuator as the number of pulses, and a difference between the number of command pulses and the number of output pulses of the sensor as a position deviation of the movable body. A deviation counter, and an actuator drive means for driving the servo actuator in the direction in which the position deviation disappears based on the output of the deviation counter. A position control device for a movable body, comprising means for resetting the position. 2. A sensor for detecting a displacement amount of a movable body which is displaced by a servo actuator as the number of pulses, and a difference between the number of command pulses and the number of output pulses of the sensor as a position deviation of the movable body. A deviation counter, and an actuator drive means for driving the servo actuator in the direction in which the position deviation disappears based on the output of the deviation counter. And a means for stopping the supply of electric power to the actuator driving means when a certain time has elapsed from that time.