JPH071462B2 - Numerical control method - Google Patents

Description

The present invention relates to a numerical control method, and more particularly to position loop gain control of a motor in position control for controlling a transient position of a servo motor.

[Conventional technology]

FIG. 2 is a block diagram for explaining the outline of the conventional numerical control method. In the figure, reference numeral (1) is a command unit that outputs a signal instructing the movement amount P _CMD per unit time,
(2) is the detected actual movement distance Pf per unit time
A processing unit that outputs a signal representing _B , (3) a low-frequency gain compensation circuit, (4) a setting unit that sets the position loop gain K _P , and (5) a signal that represents the detected actual speed Vf _B. A processing unit for outputting, (6) a power amplification unit (including a current loop),
(7) is a servomotor, and (8) is a detector for detecting position and speed.

Next, the operation will be described. The detector (8) detects the rotational position and rotational speed of the servomotor (7),
This detection signal is supplied to the processing units (2) and (5). The processing unit (2) outputs a signal representing the actual movement distance Pf _B, and the processing unit (5) outputs the actual speed Vf.
A signal representing _B is output. The output of the power amplification section (6) is controlled based on the signal representing the actual speed Vf _B from the processing section (5) and the loop gain K _P set by the setting section (4). Servo electric motor (7)
Is driven.

On the other hand, a signal indicating the movement amount P _CMD instructed by the command unit (1) and the actual movement distance Pf output from the processing unit (2).
_The signal indicating _B is calculated, and the difference between the movement amount P _CMD and the actual movement distance Pf _B is calculated as the position deviation (9). The signal indicating the position deviation (9) is supplied to the low-frequency gain compensating circuit (3), and if the position deviation (9) is a small value within a certain range, the value is larger than that in the normal case, The position loop gain K _P of the setting unit (4) is increased so that it is multiplied by a certain constant. By increasing the gain in this way, the response at the time of a minute command becomes reliable.

[Problems to be solved by the invention]

Since the numerical control device to which the conventional numerical control method is applied is configured as described above, it is impossible to quantitatively grasp the amount of the follow-up delay, and for example, it corresponds to the change of the follow-up delay with respect to the change of the cutting speed. However, there is a problem in that the adjustment of the gain by the machine is diversified. Also, since the position loop gain is constantly increasing when stopped,
There was also a risk of mechanical vibration.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to quantitatively grasp the current tracking delay, and the tracking delay can be matched with a target value. The purpose is to obtain a control method.

[Means for solving problems]

A numerical control method according to the present invention detects a rotation position and a rotation speed of a servomotor, obtains an actual movement amount and an actual speed from the rotation position and the rotation speed, gives a command movement amount, and gives an actual movement amount and a command movement amount. The position deviation is obtained from the position deviation, the theoretical position deviation is sequentially obtained from the preset position control loop position loop gain and command movement amount, and the difference between the position deviation and the theoretical position deviation is multiplied by the preset correction constant to determine the position. A deviation is added, the added position deviation is multiplied by a position loop gain, and the servomotor is controlled based on the multiplied position deviation and the actual speed so that the position deviation follows the theoretical position deviation. It was done.

[Action]

In the present invention, the position deviation is obtained from the given command movement amount and the actual movement amount, the theoretical position deviation is sequentially obtained from the preset position control loop position loop gain and the command movement amount, and the position deviation The difference from the theoretical position deviation is multiplied by a preset correction constant and added to the position deviation, the added position deviation is multiplied by the position loop gain, and the servo is based on the multiplied position deviation and the actual speed. The motor is controlled and the position deviation follows the theoretical position deviation.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, the same reference numerals as those in FIG. 2 indicate the same or corresponding portions, and thus detailed description thereof will be omitted. Reference numeral (10) is a position loop gain variable circuit, (10a) is a command unit that outputs a signal instructing the position deviation model value D _CMD per unit time, and (10b) is a setting unit that sets the correction constant value Ka. Is.

The output of the power amplification unit (6) is controlled based on the signal representing the actual speed Vf _B from the processing unit (5) and the position loop gain K _P set by the setting unit (4), and the output This drives the servomotor (7).

Also, a signal indicating the movement amount P _CMD instructed by the command unit (1) and the actual movement distance Pf output from the processing unit (2).
_The signal indicating _B is calculated, and the difference between the movement amount P _CMD and the actual movement distance Pf _B is calculated as the position deviation (9). The value of this actual position deviation (9) is the position loop gain K _P.
And the movement amount per unit time P _CMD instructed by the command unit (1)
Almost determined by

At the time of a minute instruction, the position deviation (9) as intended is caused by the resolution of the detector (8), the dead zone of the servomotor (7), the dead zone of the power amplifier (6) (including the response limit of the current loop gain), etc. In some cases, the value of, that is, the actual position deviation D cannot be tracked. Further, the above-mentioned position deviation model value per unit time, that is, the theoretical position deviation D _CMD is expressed by the equation (1).

D _CMD = P _CMD / K _P ……… (1) The value of this theoretical position deviation D _CMD is given to the control system in synchronization with the movement amount P _CMD, and the actual position deviation D and the theoretical position deviation D _CMD The difference is multiplied by the correction constant value Ka set by the setting section (10b) and added to the actual position deviation D. Then, the actual position deviation D to which the value of the correction constant value Ka of the difference between the actual position deviation D and the theoretical position deviation D _CMD is added is multiplied by the position loop gain K _P , and the multiplied actual position deviation D Also, the output of the power amplification section (6) is controlled based on the actual speed Vf _B and the servomotor (7) is drive-controlled.

By such an operation, when the actual position deviation D is deviated from the theoretical position deviation D _{CMD due} to a minute command of the movement amount P _CMD instructed by the command unit (1), the actual position deviation D is _calculated. The value added to the actual position deviation D changes so as to approach the theoretical position deviation D _CMD , and the actual position deviation D follows the theoretical position deviation D _CMD .

The added value is represented by Ka (D-D _CMD ), and the correction constant value Ka is a constant for bringing the actual position deviation D close to the theoretical position deviation D _CMD , and the value of the correction constant value Ka is The larger the value, the more effective the effect.

The actual actual position deviation D follows the ideal theoretical position deviation D _CMD with an error due to disturbance due to friction existing in the mechanical system. For example, when the moving direction is reversed, the friction There is a moment when there is no movement at all until the torque exceeding the force is generated, and the theoretical position deviation D _CMD
However, by adding the correction based on the correction constant value Ka, the actual position deviation D can be brought close to the theoretical position deviation D _CMD .

However, if the value of the correction constant value Ka is too large, mechanical vibration or noise occurs, so the optimum value of the correction constant value Ka can be set to the upper limit value at which these values do not occur to obtain the maximum effect. .

Therefore, the correction constant value Ka is set for each machine according to its mechanical characteristics, and is set by the setting section (10b).

In addition, all the units of the above variables are calculated by converting the unit time per second. Further, it is desirable that the position loop gain K _P is a digital control that can be controlled in terms of parameters.

〔The invention's effect〕

As described above, according to the present invention, the position deviation is obtained from the given command movement amount and the actual movement amount, and the theoretical position deviation is sequentially obtained from the preset position control loop position loop gain and the command movement amount. , The difference between the position deviation and the theoretical position deviation is multiplied by a preset correction constant and added to the position deviation, the added position deviation is multiplied by the position loop gain, and the multiplied position deviation and actual speed Based on the above, the servo motor is controlled so that the position deviation follows the theoretical position deviation.Therefore, the position deviation does not depend on the characteristics of the speed change and the opportunity, and even when the command movement amount is minute, The deviation follows the theoretical position deviation, the cutting error can be minimized, and highly accurate numerical control can be performed.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, and is a block diagram for explaining an outline of a numerical control method, and FIG. 2 is a block diagram for explaining an outline of a conventional numerical control method. In the figure, reference numeral (6) power amplifier, (7) servo motor, (8) detector, (9) position deviation, (10) position loop gain variable circuit, (10a) per unit time A command unit that outputs a signal indicating the position deviation model value, (10
b) is a setting unit for setting the correction constant value. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A rotation position and a rotation speed of a servomotor are detected, an actual movement amount and an actual speed are obtained from the rotation position and the rotation speed, a command movement amount is given, and the actual movement amount and the command movement amount are calculated. The position deviation is obtained, the theoretical position deviation is sequentially obtained from the position loop gain of the position control loop and the command movement amount set in advance, and the difference between the position deviation and the theoretical position deviation is set by a preset correction constant. Then, the position deviation is added to the position deviation, the added position deviation is multiplied by the position loop gain, the servo motor is controlled based on the multiplied position deviation and the actual speed, and the position deviation is calculated based on the theory. A numerical control method characterized in that it is made to follow a dynamic position deviation.