JPH03108010A - Position controller - Google Patents

Abstract

PURPOSE:To attain exact coincidence between transient responses to acquire synchronism for position control of plural axes by properly delaying a speed control command in accordance with lengths of response dead times peculiar to respective speed control parts so that they coincide with one another as the whole. CONSTITUTION:The extent of delay of a delay control part 21 is adjusted by the number of stages of delay means 22. When plural position controllers having speed control parts 15 are used to perform the position control of plural corresponding axes, the speed control part having the longest response dead time is found, and differences between the response dead time peculiar to this speed control part and those to the other speed control parts are obtained. Extents of delay in delay control parts 21 of the other speed control parts are set to the number of stages in the increasing direction by these differences. Thus, response dead times of the other speed control parts are matched to that of the speed control part having the longest response dead time, and responses completely coincide with one another in all speed control parts, and the synchronism deviation of transient responses is eliminated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a position control device used, for example, in a controller for an NC machine tool or a robot, and in particular, the present invention relates to a position control device used for example as a controller for an NC machine tool or a robot, and in particular performs position control using a plurality of measurement control units to control the position of a plurality of axes. The present invention relates to a position control device used in a numerical control device that performs synchronous operation.

[Conventional technology]

FIG. 2 shows an example of a conventional position control device used in a controller for an NC machine tool or a robot. This position control device includes an adder 11 and a delay means 12 arranged on the output side of the adder 11. Delay means 1
The output of 2 is supplied to a multiplier 13 and an adder 11.

The adder 11 inputs the command movement amount P and the motor movement amount R for each unit time, and adds the difference between them to the delayed output of the delay means 12. The delay means 12 inputs the addition result A of the adder 11, delays it by a unit sample time, and outputs it. If this relationship is described using the quantity Zml representing the delay of unit sample time, it will be as shown in the following equation (1).

A = A Z-' + P -R... (1
) The multiplier 13 multiplies the delayed output AZ-' of the delay means 12 by a gain K that determines the responsiveness of position control, and supplies this result to the speed control section 15 as a speed control command Q.

The speed control command Q can be expressed by the following equation (2).

Q=KAZ (2) A speed control command Q is input to the speed control section 15, and the rotational speed of the motor 16 connected to the output side thereof is controlled. The rotation of the motor 16 is controlled by a position detector 17 such as an encoder.
detected by. The position detector 17 outputs the motor movement amount R for each unit sample time to the adder 11. where motor movement i per unit sample time
R may be considered to be approximately equivalent to the rotational speed of the motor 16.

As described above, the conventional position control device shown in FIG. 2 as a whole is a feedback control system in which the command movement amount P is manually input and the motor movement IR is fed back.

Let us consider the response of the device shown in FIG. Assume now that the response characteristic from the speed controller 15 to the output of the position detector 17 is expressed only by a dead time element having a response dead time n times the unit sampling time. At this time (3)
The formula holds true.

R=QZ... (3) In this case, the transfer function from the command movement amount P to the motor movement ff1R is expressed as the following equation (4) based on equations (1) to (3). be able to.

R/P=KZ-"-'/[1-(1-KZ-")Z-'
]... (4) Figure 3 shows the transfer function of equation (4) when K=0.
05 shows the step response. It can be seen that the transient characteristics vary greatly depending on the numerical value n representing the size of the dead time of the speed control section 15.

[Problem to be solved by the invention]

As described above, in the conventional position control device, the transient characteristics vary greatly depending on the numerical value n representing the size of the dead time. Therefore, if a plurality of speed control units having different response dead times are used to control the positions of a plurality of axes, the following problem occurs. In other words, for example, when performing synchronized operation such as path following control using multiple axes, the transient responses of these position control devices differ depending on the response dead time of the speed control section, so synchronization between the axes is difficult. An error will occur. As a result, the entire system with these multiple axes is unable to correctly follow a path.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a position control device that can match the transient characteristics of these speed control units even when performing position control using a plurality of speed control units having response dead times.

[Means to solve the problem]

In the present invention, (i) a motor for performing position control;
ii) a speed control section that has a unique response dead time in controlling the speed of this motor; and (iii) a speed control command delay that delays the speed control command to be output to this speed control section by an arbitrary amount of time. The position control device is provided with means.

That is, in the present invention, the speed control command is appropriately delayed in accordance with the unique response dead time of each speed control section, so that the response dead times in the respective speed side 'H sections are made to appear to match.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 shows a position control device in one embodiment of the present invention. In FIG. 1, the same parts as in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

This position control device includes an adder 11, a delay means 12, and a multiplier 13 like the conventional position control device shown in FIG. The speed control command Q output from the multiplier 13 is
The signal is input to the speed control unit 15 via the delay control fpf) 21. The speed control section 15 controls the rotational speed of the motor 16. The rotation of the motor 16 is detected by a position detector 17 such as an encoder, and is output as a motor movement amount R to the adder 11.

In this device, the delay control section 21 has a series circuit in which M stages of delay means 22 (where M is a sufficiently large integer) are connected, and the output of an arbitrary number of stages of these delay means 22 is selected to be taken out as an external output. It is composed of a circuit. This example shows how the output of the m-th stage (m<M) is output to the speed control section 15 as the speed control command Q'.

The speed control command Q' is obtained by delaying the speed control command Q input to the delay control section 21 by m sample times, and can be expressed by the following equation (5).

Q' = QZ (5) Next, the response of such a position control device will be considered.

Similar to the previous explanation, the response characteristic of the speed control section 15 is (3)
It is assumed that the dead time element has a response dead time that is n times the unit sample time of the equation. In this case, the transfer function from the command movement amount P to the motor movement amount R is expressed by the following equation (6).

R/P = K Z-'-'-'/[1-(1-K
(6) This equation (6) is the same as equation (4) in which the term n is replaced with (n+m).

That is, if we set N=n+m (7), equation (6) matches equation (4) as shown in equation (8) below.

R/P=KZ-"-'/[1-(l-KZ-')Z-'
] (8) The step response of this position control device is the same as that in FIG. 3 in which the numerical value n is replaced with the numerical value N.

The position control device of this embodiment explained above has a delay control section 2.
The delay amount of 1 can be adjusted by the number of stages of the delay means 22. Therefore, when performing position control of a plurality of corresponding axes using a plurality of position control devices each having a speed control section 15, find the speed control section with the largest response dead time among them, and The difference between the unique response dead time and the unique response dead time of each of the other speed controllers is determined. Then, the delay amount of the delay control section 21 of these other speed control sections is set to the number of steps in the increasing direction by an amount corresponding to the difference between them.

Thereby, it is possible to match the response dead time of other speed control parts to the speed control part having the largest response dead time. As a result, the responses of all speed controllers are completely consistent, and even when controlling the position of multiple axes in response to multiple speed controllers, synchronization errors that occur due to transient responses can be eliminated. It can be made zero.

[Effects of the Invention] As explained above, according to the present invention, the speed control command is appropriately delayed according to the length of the response dead time specific to each speed control section so that these delay times match as a whole. Therefore, even if the transient responses differ depending on the length of the response dead time, it is possible to accurately match the transient responses, and it is possible to eliminate the position error that has conventionally occurred in the transient response. Therefore, it is possible to reduce the synchronization error to zero when performing position control of a plurality of axes.

Furthermore, if the response characteristics of different position control devices are matched in advance, even if one device breaks down, it can be replaced with another device to ensure the same characteristics.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the circuit configuration of a position control device according to an embodiment of the present invention, Fig. 2 is a block diagram showing the circuit structure of a conventional position control device, and Fig. 3 is a block diagram showing the circuit configuration of a position control device according to an embodiment of the present invention. FIG. 3 is a characteristic diagram showing a step response when 15... Speed control section, 16... Motor, 17... Position detector, 21... Delay control section, 22... Delay means.

Claims (1)

[Claims] A motor for performing position control, a speed control section having a specific response dead time in controlling the speed of this motor, and a speed control command output to this speed control section for an arbitrary period of time. 1. A position control device comprising a speed control command delay means for outputting a speed control command with a delay of .