JPS58129508A - Control device of position - Google Patents

Abstract

PURPOSE:To obtain a position control device which causes no difference between a command position and a machine position at all times, by additionally providing a function for automatically correcting a delay between the command position and the machine position. CONSTITUTION:A position command pulse is inputted to a phase modulator 7, and from the modulator 7, a square wave of a constant period, which has been phase-modulated is outputted and is inputted to a phase discriminator 8. In the discriminator 8, phase error width of signals of a position detector 2 and the modulator 7 is detected, and it is inputted to a pulse train transducer 9. The transducer 9 converts a detection error to a pulse train, adds it as an error quantity pulse to a common pulse by a command adder 10, and a new command pulse containing an error portion of a command position and a machine position is led into a phase modulator 1. From the modulator 1, a square wave of a constant period is outputted, it rotates a driving motor 5 through a phase discriminator 3 and a driving amplifier 4, moves a moving base 6 of a hop board, and rotates the detector 2. When a control loop is constituted so that an output of the discriminator 8 becomes ''0'', the command pulse is inputted as it is to the modulator 1, and the command position coincides with the machine position.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position control device in a numerical control device.

When using a numerical control device to control the position of a control target, such as the feed axis of a machine tool such as a hobbing machine, the semi-closed loop method is generally used to control the position by attaching a position detector directly to the drive motor. Alternatively, there is a closed loop method in which a position detector is attached to a movable table on the machine side. FIG. 1 is a block diagram showing a conventional example of such a position control device based on a semi-closed loop system.

To explain the conventional device based on Fig. 1, (1) is 1
A phase modulator (2
) is a position detector that detects the current position of the machine, (3) is a phase discriminator that compares the output of the phase modulator (1) and the output of the position detector (2), and (4) is a phase discriminator ( a drive amplifier (6) that amplifies the output of 3) to drive the motor (5);
is a movable platform to be controlled, which is driven by a drive motor (5).

Next, the operation of this device will be explained. The position of the phase-shifted square wave is modulated. The amount and speed of this modulation are proportional to the number of input command pulses and the input speed (pulse density). As a result, an error occurs between the output phase of the position detector (2) and is detected as an error width in the phase discriminator (3). This error width is converted into a DC voltage in the drive amplifier (4), and further power amplified to rotate the drive motor (5) at a speed proportional to the error width.

The rotation of the motor (5) is transmitted to the movable table (6) by turning the V-screw of the machine, and the movable table (6) is moved at a speed proportional to the error width. At the same time, the rotation of the motor (5) with.

It is also transmitted to the position detector (2), for example, the reso V
eso1vθ)! ii. The detector (2) is rotated so that its phase becomes the same as the output phase of the phase variable WJIJ device (1), that is, the output of the phase discriminator (3) is controlled to be zero.

In this way, in the device shown in Figure 1, when a command for position control is input, the one-phase discriminator (3) excludes an error width proportional to the command (so-called tracking error), and uses this error output as The motor (5) rotates at a proportional speed to move one machine, that is, the movable 8 (6), by the amount of the command value. However, in this device, the phase discriminator (3
), the movable base (6) begins to move only when an error output is generated at the position, so there is always an error between the command and the machine (movable base) position, and the movement of the machine is delayed by the error.

This amount of delay changes depending on the rotational speed of the motor (5), that is, the input speed (pulse density) of the command bus V. For example, when cutting the same position with a hobbing machine by changing the cutting speed for the first and second cutting. Since the amount of shedding varies depending on the cutting speed, there is a drawback that accurate cutting cannot be performed. In addition, in order to eliminate this delay, it is necessary to
It is necessary to make corrections to the speed, but the amount of correction also varies depending on the speed, and accurate position control cannot be performed at speeds other than the preset speed.

This invention was made in order to eliminate the drawbacks of the conventional device as described above, and by adding a function to automatically correct the delay between the command position and the machine position that occurs in the conventional device, The object is to provide a one-position control device in which there is always no difference between the commanded position and the machine position.

An embodiment of the present invention will be described below.

FIG. 2 is a block diagram showing an embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate the same or corresponding parts, and since they operate in the same way, repeated explanation will be omitted. (7) is the second
This phase modulator converts the number of command buses into a phase difference amount in the same way as the 1-phase modulator (1). (8) is a second phase discriminator that compares the output phase of the second phase modulator (7) and the output phase of the position detector (2), and (9) is a second phase discriminator (8 ) is a pulse train converter (9) that converts the error width output of the command bus into a pulse train having the same form as the command bus.

This is a command adder that adds the output error amount pulse.

Next, the operation will be explained. The second phase modulator (7) always outputs a rectangular wave with a constant period.

The output is phase modulated by the input of the command bus V. As a result, a phase difference occurs between the phase modulator (7) and the position detector (2), which is detected as an error width in the second phase discriminator (8). This detection error is due to the 331-column converter (9)
The pulse train is input to the command pulse, converted into a pulse train having the same form as the command pulse, and added to the command pulse in a command adder as an error amount pulse indicating the error between the command position and the machine position.

In this way, a new position command bus V including the error between the command position and the machine position is created in the command adder QO, which is introduced into the phase modulator (1), and is introduced into the phase discriminator (3). ), the drive motor (5) is rotated via the drive amplifier (4) in the same way as the device shown in FIG.
) and rotate the position detector (2). Therefore, when the command P/V rate remains constant, the pulse train converter (9) outputs an error amount pulse when the command starts to be input, and this pulse is inputted into the phase modulator (1) in excess. 1. If the machine moves an extra amount of error amount V with respect to the conventional position, then Similarly, the position detector (2) also rotates an extra amount by an error amount of 237. On the other hand, since the command pulse is input as is to the second phase modulator (7) and indicates the command position, the position detector (
A second phase discriminator (8) eliminates the phase difference of the output with
), the output of the pulse train converter (9) becomes zero after a certain time determined by the control loop gain, and the output of the pulse train converter (9) becomes zero. The pulse will be input as is.In other words, at this time, the command phase and model phase will match, and one machine will be at the commanded position.Therefore, no matter what the table command speed is, when a constant speed command is given, Since the model always moves at a position that matches the commanded position except for a short time when the command starts and stops, no special correction is required even if the commanded speed is changed.

Incidentally, in the nine embodiments described above, a position control device using a semi-closed loop method was shown, but if the position detector (2) is constructed of an inductosin or the like, it can be easily converted to a closed V-bu method. It is.

As described above, according to the present invention, one machine always moves to a position that coincides with the commanded position, except for a short time when the command starts and stops, and no position error occurs during this time. Therefore, even when controlling the position by changing the speed, no special correction is required.

It is possible to perform highly accurate position control, and for example, when cutting threads with a hobbing machine, it is possible to perform cutting without positional deviation without special correction even if the cutting speed is changed during rough cutting and finishing cutting. can.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional device. FIG. 2 is a block diagram showing an embodiment of the present invention. (1)...Phase modulator, (2)...Position detector, (
3)... Phase discriminator, (5)... Drive motor, (6
)... Movable base, (7) -... Second phase modulator, (8
) - second phase discriminator, (9) - pulse train converter, α
G--Command adder. In Figure 1, the same reference numerals indicate corresponding parts. Agent Makoto Kuzuno

Claims (3)

[Claims] (1) A position am detector outputs a position detection signal indicating the current position of the controlled object, and a position li1 error signal is detected by comparing the output of this position detector with a position command signal indicating the commanded position of the controlled object. a signal converter that converts the output of the position error detection circuit into a signal having the same form as the position command signal; and a command adder that adds the output of the signal converter to the position command signal; A phase modulator whose output is modulated by the input of the command adder output, a phase discriminator which compares the output of this phase modulator with the output of the position detector, and a control target that is proportional to the output of this phase discriminator. and a drive means for driving the position control device. (2) The position error detection circuit includes a second phase modulator whose output is modulated by the input of the position command signal, and a second phase modulator that detects the phase difference between the output of the second phase modulator and the output of the position detector. 2. The position control device according to claim 1, further comprising two phase discriminators. (3) The position control device according to claim 1, wherein the controlled object is a feed shaft of a hobbing machine.