JPS5818712A - Position controller - Google Patents

Abstract

PURPOSE:To control a position with high accuracy by executing the succeeding control on the basis of the quantity of coasting and that of an error in the preceding control. CONSTITUTION:An apparatus driven by a motor is turned to creeping speed just before its stop and then braked in consideration of the quantity of coasting. In this case, the quantity of coasting generated until the apparatus is stopped after braking and an error from a prescribed position at the time of stopiing are detected and stored in memories 13, 15. Coasting information is updated on the basis of these information. In the succeeding operation, the quantity of coarsing to be generated until the stop of the apparatus is calculated on the basis of the preceding error to obtain braking timing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position control device for stopping an object driven by an electric motor at a target position.

As is well known, position control devices that stop an object driven by an electric motor at a target position are often used in machine tools and the like. In order to stop the object at the target position, when the deviation between the target position and the actual position reaches a predetermined value, the object is decelerated to a creep speed (3 to 4% of the rated speed). When the positional deviation reaches a smaller predetermined value (coasting amount setting value) in the state of creep speed, that is, when the target object reaches a position ahead of the target position by the coasting amount setting value, the motor is stopped and Applying the brake allows the vehicle to coast and stop at the target position.

Conventionally, the coasting amount after a stop operation is assumed to be constant, and the coasting amount setting value is fixed and given to a constant value.

The amount of coasting can be set based on the inertia of the electric motor and object, braking force, and creep speed.

However, even if the braking force is constant, the coasting amount is
Aging and temperature of electric motors and objects.

It fluctuates due to changes in the coefficient of friction due to changes in the working environment such as humidity. Electric brakes are usually applied using frictional force, so the braking force also changes, further exacerbating fluctuations in the amount of coasting. For this reason, it becomes impossible to accurately stop the object at the target position.

As described above, the conventional method has the disadvantage that the object cannot be accurately stopped at the target position because the amount of coasting after the stop operation fluctuates.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a position control device that can accurately stop an object at a target position.

A feature of the present invention is that the coasting amount setting value for the previous operation is corrected by the position error from the previous operation, and the corrected coasting amount setting value is used as the coasting amount setting value for the current operation.

Note that the previous operation in this specification means not only the time immediately before the current operation but also the previous operation.

FIG. 1 shows an embodiment of the present invention.

In FIG. 1, a target machine 7 to be subjected to positioning control is mechanically directly connected to an electric motor 4, and is also provided with a speed detector 5 and a brake device 6.

A position detector 8 is attached to the target aircraft 7.

The position control circuit 1 inputs the position command value PR and the actual position value PF detected by the position detector 8, and receives the speed command signal Nm and the operation stop signal 0. Output. The speed control circuit 2 compares the speed command value Na with the actual speed value NF of the speed detector 5, and controls the motor drive circuit 3 so that the motor speed becomes the command value NR. The motor drive circuit 3 is composed of a thyristor, a transistor, or the like.

FIG. 2 shows a detailed configuration diagram of an example of the position control circuit.

In FIG. 2, a comparator circuit 9 compares a position command value PR and an actual value PF, and a position deviation ΔP is determined by a speed command circuit 10. Deceleration command circuit 11. Added to stop command circuit 12 and memory circuit 13. The speed command circuit IO outputs a step-like speed command signal NR which rises when the positional deviation ΔP is added and becomes zero when the positional deviation ΔP reaches a predetermined value ΔPs. The deceleration command circuit 11 inputs the positional deviation ΔP and outputs a deceleration command signal DC to the speed control circuit 10 when the target machine 7 reaches a predetermined position. 12 outputs an operation stop signal O1 for coasting from the creep speed. The position error storage circuit 13 stores the position deviation 4P after the operation, that is, the position error ε, and the coasting amount storage circuit 15 stores the coasting amount setting value of the correction circuit 14 after the operation path r. The storage timing of both storage circuits 13 and 14 is controlled by a timing circuit 16. The switch 17 sets the coasting amount storage circuit 15 and the initial value of the coasting amount.

Next, its operation will be explained with reference to FIG.

Now, as shown in Figure 3(a), the position deviation ΔP due to the previous operation is
Assume that the position command value PR is changed from PRI to PH1 at time t1 in a state where there is ε (position error).

The comparator circuit 9 outputs a positional deviation ΔP to which the positional error ε of the previous operation is added, as shown in FIG. 3(C). Speed command circuit 1
0 outputs a speed command signal NR that changes stepwise as shown in FIG. 3(b) when the positional deviation ΔP is added. The speed control circuit 2 compares the speed command value NR and the actual speed value Nr detected by the speed detector 5, and controls the motor 1 drive circuit 3 so that the deviation becomes zero. As a result, the electric motor 4 is started, accelerated as shown by the dashed line in FIG. 3(I), and then driven at a constant speed N1. The target aircraft 7 also moves due to the drive of the electric motor 4, and its position Pr moves as shown by the dashed line in FIG. 3(a) (in FIG. 4).

When the target aircraft 7 moves to position P and the positional deviation ΔP from the target position PR2 becomes ΔP, the deceleration command circuit 11 gives a deceleration command signal Dc to the speed command 1 command circuit 10.

The deceleration command circuit 11 repeatedly calculates the following equation at intervals of approximately 1 ms, and outputs a deceleration command signal Da.

First, based on the speed command value NR of the speed command circuit 10, a movement amount M1 necessary for deceleration is determined from a constant speed N1.

Ms "f'(N1-α)dt...
(1) α: Deceleration When this movement amount M becomes equal to the positional deviation ΔP, the deceleration command signal Dc shown in FIG. 3(f) is output.

When the speed command circuit IO receives the deceleration command signal Da at time t2, it sets the speed command value NR to the creep speed N2 as shown in FIG. 3(b). The speed control circuit 2 controls the motor drive circuit 3 so that the speed of the motor 4 becomes a creep speed N2. As a result, the electric motor 4 (target machine 7) is
1)) It decelerates as shown by the dashed line and reaches the creep speed N2 at time t3. With the electric motor 4 operating at the creep speed N2, the target machine 7 further approaches the target position PR2, and the positional deviation ΔP becomes smaller. The stop command circuit 12 receives the speed command value NR.
(=N2) and the coasting amount set value given as described later, and calculate the following formula to receive the operation stop signal O8.
Output. The stop command circuit 12, like the deceleration command circuit 11, repeats this calculation at intervals of about 1 ms.

M2=f(N2-β)dt ・・・・・・・・・(
2) β: Deceleration When this movement amount (coasting amount) M2 becomes equal to the coasting amount setting value up to the own aircraft position PR2, the operation stop signal O1 is output. Note that the coasting amount M2 is a quadratic curve due to the action of the braking force, but since it is complicated and does not directly relate to the gist of the present invention, it will be described approximately as a linear curve.

Position P2 where the movement amount M2 is equal to the set value at time t4
When this happens, the stop command circuit 12 generates an operation stop signal 08 as shown in FIG. 3(g), and the speed command circuit 10 and brake device 6
Add to. The stop command circuit 12 inputs the position deviation ΔP as shown by the dotted line, and calculates the amount of movement.

The repair pressure may be applied to M2 at a set value.

The speed command circuit 10 receives the operation stop signal 0. When the speed command value NR is added, the speed command value NR becomes zero, and the brake device 6 still applies the brake. This stopping operation causes the target aircraft 7 to stop at the target position PR2.

On the other hand, the coasting amount set value is determined by the stop command circuit 1 as follows.
given to 2.

First, when the target machine 7 starts operating, the switch 17 is turned on to store an initial value in the coasting amount storage circuit 15. Set. At this time, the position error storage circuit 13 has been reset. The outputs of the coasting amount storage circuit 15 and the position error storage circuit 13 are added in the correction circuit 14, and this added value is added to the stop command circuit 12 as the coasting amount setting value. Therefore, the initial value is set at the start of operation. becomes the coasting amount setting [L].

Now, as shown in FIG. 3, it is assumed that there is a position error of ε due to the driving operation before moving the target aircraft 7 from position PR1 to PR2. At this time, the position error storage circuit 13
The position error ε is stored as shown in FIG. 3(d). Furthermore, as shown in FIG. 3(e), the coasting amount storage circuit 15 stores the coasting amount setting value -1 for the previous operation with the position PR1 as the target position.

The memory of both storage circuits 13 , 15 is provided by a timing circuit 16 . As shown in FIG. 3(h), the timing circuit 16 activates both memory circuits 13 after a predetermined time after the stop command circuit 12 outputs the operation stop signal O1 as shown in FIG. 3(g).
．． 15, give memory command pulses ml and m2. Memory command pulses to both memory circuits 13 and 15 are applied with a difference of several milliseconds. The position deviation storage circuit 13 stores the position deviation ΔP, that is, the position error ε, of the comparator circuit 9 at the time when the memory command pulse is applied, and the coasting amount storage circuit 15 stores the coasting amount setting value of the correction circuit 14.

In this way, the position error ε at the previous operation is stored in the position deviation storage circuit 13, the coasting amount set value at the previous operation is stored in the coasting amount storage circuit 15, and the values stored in both storage circuits are It is updated every time the target aircraft 7 moves once.

In this way, the coasting amount setting value given to the stop command circuit 12 is changed. During the current operation to move the target aircraft 7 to the target position PR□, there was an insufficient position error ε during the previous operation, so the position error 6 was subtracted from the coasting amount set value Ln-1 during the previous operation, as shown in Figure 3(e). Give the coasting amount set value as shown in .

Conversely, if the target aircraft 7 went too far from the target position during the previous operation, -1+ε becomes the current coasting amount setting value.

In this way, the motor stop operation start position is changed by changing the coasting amount setting value, but as shown in Fig. 4, for example, it was thought that if coasting was started at position P2m, it would stop at the target position PR. If an insufficient position error ε occurred during the previous operation, the stop operation is started when the position of the target aircraft 7 reaches P2b. Then, the target aircraft 7 is shown in Fig. 4 (a
), it decelerates and reaches the target position PR at the time.

Furthermore, if the previous operation had gone too far, the stop operation will be started at position P2m, the speed will be decelerated using the C characteristic, and it will stop at the target position PR.

As described above, the target aircraft is controlled to stop at the target position, and the coasting amount set value is changed depending on the position error in the previous operation to change the stop operation start position. Therefore, even if the frictional force changes due to the work environment of the target machine or changes over time, the target machine can be stopped at the target position with high accuracy.

As explained above, the present invention corrects the coasting amount set value during the current operation based on the position error at 6 during the previous operation, so the vehicle stops at the target position with high precision without being affected by the work environment or aging. can be done.

In the above-described embodiment, the coasting amount setting value is corrected every time the target aircraft moves, but it is also possible to correct the coasting amount setting value by performing copying operation once a day, for example. The good one is of course Lc.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
Detailed configuration diagram showing an example of the position control circuit in the figure, Part 3
The figure is a waveform diagram for explaining the operation of the present invention, and FIG. 4 is a characteristic diagram for explaining the present invention. 1...Position control circuit, 2...Speed control circuit, 3...
- Motor drive circuit, 4... Electric motor, 5... Speed detector, 6... Brake device, 7... Target machine, 8...
・Position detector, 9...Comparison circuit, 10...Speed command circuit, 11...Deceleration'I53 mouth cj, , WL2nd
4-Picture Haruyama

Claims (1)

[Claims] 1. When stopping a target object driven by an electric motor at a target position, the target object is decelerated to creep speed, and then coasted when the target object reaches a position ahead of the target position by a coasting amount setting value. In the position control device, the position error storage circuit stores a position error in a previous operation;
A coasting amount storage circuit for storing a coasting amount setting value in a previous operation is provided, and the coasting amount setting value for the current operation is obtained by correcting the coasting amount setting value stored in the coasting amount storage circuit by the position error. A position control device characterized in that it is configured to give