JPH04100130A - Servo controller for motor - Google Patents

Abstract

PURPOSE:To improve the following-up property without damaging the stability of a control system by changing a position loop gain KP and a speed feed- forward gain KF at the time of at least rise or fall of the speed while keeping specific relations. CONSTITUTION:An adder 12 which calculates the difference between the positioning target position from a function generator 4 and the present position from a position detector 2, an absolume value circuit 13 which calculates the absolute value of the output of this adder, and a gain determining device 14 which determines the position loop gain KP and the speed feed-forward gain KF by the output of the absolute value circuit 13 are provided. The position loop gain KP and the speed feed-forward gain KF are changed to values determined by the gain determining device 14 in accordance with a condition KP=1/a(1-KF) ((a) is fixed). Thus, the following-up property of the motor is improved without damaging the stability of the control system.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a servo control device for a motor, etc., and in particular, a gain is set so that the position and speed of the motor follow the commands from a function generator when the speed rises and falls. The present invention relates to a servo control device equipped with means for changing.

[Prior Art] FIG. 2 shows a block diagram of an example of a conventional servo control device. A control device that controls a controlled object (not shown) consisting of a machine driven by a motor 1 has a position detector 2 that generates pulses depending on the rotation angle of the motor 1 coupled to the motor 1. The output from 2 is input to the differential element 3, and the number of pulses per unit time is counted to generate a speed signal.

Further, a function generator 4 for calculating a speed command pattern based on the target position of the controlled object, and an adder 5 for calculating the deviation between this speed command pattern and the speed signal which is the output of the differential element 3 are provided. The speed deviation signal output from the adder 5 is integrated by an integral element 6 to output a position deviation signal.

The second position deviation is amplified by the position amplifier 7, and the result, the speed feedforward signal whose speed command pattern is amplified by the speed feedforward amplifier 8, and the output of the differential element 3 are amplified by the speed detection amplifier 9. The detected speed signal is applied to an adder 10. Here, the deviation between the speed command and the speed detection signal is output, and this speed deviation is amplified by the speed amplifier 11 and applied to the motor.

JP-A No. 61-122718 adds to the above configuration a subtracter that calculates the difference between the final target position and the current target position, an absolute value circuit that takes the absolute value of the difference, and a comparison between the magnitude of the difference and a predetermined value. (-1 was added to the comparator, and the proportional, integral, and differential gains of the control section were changed to two types of gains, large and small, based on the comparison results.

Further, in Japanese Patent Application Laid-Open No. 62-2877, the speed feedback key is changed by switching the F/D conversion coefficient depending on whether the CPU including the function generating section is at the time of speed rise or constant speed operation.

[Problems to be Solved by the Invention] However, in the above configuration, the gain related to the stability of the control system, that is, the coefficient of the denominator of the transfer function, in other words, the position of the pole in control theory is changed. There is a problem that depending on the power of changing the gain, the control system may become vibrating.

The object of the present invention is to improve the tracking of the motor at the rise and fall of speed so as not to impair the stability of controllability.

Means for Solving Problems U] The present invention detects at least the position of a motor to obtain a position signal and a speed signal, and detects a deviation between a position command given from a function generator and the position signal, and a function generator. A servo control device having a control system that calculates a speed command using a speed feedforward signal given from the motor and controls the motor so that a deviation between the speed command obtained by the calculation and the speed signal becomes zero. When the speed rises or falls, the position loop gain Kl and the speed feed forward cane KF are changed while maintaining the following relationship.

[Effect] If the position loop key Kp and the speed feed signal word key are changed according to the conditions when the speed rises or falls, the gain of the servo system in terms of the size of the position deviation in the steady state can be changed. Since it can be kept constant, the position control system can be operated in a system similar to a speed control system with a high relative gain without impairing the stability of the control system, and the tracking of the motor can be improved.

[Example] The present invention will be described with reference to embodiments shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and the same reference numerals as in FIG. 2 described above indicate the same elements. The difference between FIG. 1 and FIG. 2 is the positioning target position from the function generator 4 and the position detector 2.
an adder 12 that takes the difference of the current position from
The absolute value circuit 13 takes the absolute value of the output of 2, and the position loop gain is set to 1.2 by the output of the absolute value circuit 13. and a speed feedforward gain, and a gain determiner 14 is provided to determine the position loop gain Kp and the speed feedforward gain K to the gain determined by the gain determiner 14.
The point is that v can be changed.

FIG. 3 shows a block diagram in which the gain of the speed control section is adjusted in such a configuration so that the transfer function of the speed feedback system can be approximated to a quadratic equation. In Figure 3, is the position loop gain at the position amplifier's Cain,
K is the gain of the speed feedforward amplifier, KV is the gain of the speed feedforward amplifier, KvP is the gain of the speed amplifier, and J is the gain of the motor inertia, etc.

Also, if the gain of the speed control loop is adjusted sufficiently high compared to the gain of the position control loop so that the overall transfer function of the system without speed feedforward is determined by the position loop gain. , in a system with velocity feedforward, the position loop gain is =0
, velocity feedforward gain = 1, the transfer function of the entire servo system becomes controllable between the systems.

Furthermore, when the positional deviation ε at the time of a speed command is expressed using the final value theorem, it becomes (where A is the magnitude of the speed), and this ε is considered to be a value representing the gain of the servo system.

If the ratio between the positional deviation ε and the velocity magnitude A is set to a constant value, then equation (3) is transformed as follows.

Further, when the velocity feedforward gain is set to =O, the following is obtained.

Here, since equation (1) is the transfer function of the speed control system and equation (2) is the transfer function of the position control system, K, ≠0. To,
If ≠0, the speed control system and position control Kp”N
KF) ... (4) However, 0≦
.ltoreq.1. The relationship between Kp and .ltoreq.1 at this time is shown in FIG.

If the position loop gain Kp and velocity feedforward gain KF are on this straight line, the gain of the servo system can be kept constant in terms of the magnitude of positional deviation in a steady state, which will impair the stability of the control system. Never.

For example, as shown in FIG. 5, the gain determiner 14 is provided with a function or table that inputs the difference between the current value and the positioning target position and outputs the velocity feedforward gain KF, and calculates the velocity feedforward gain from, (
4) According to the equation, find the position loop gain KP, and set each gain to the speed feedforward amplifier and the position amplifier.

From the above, if the position loop gain Kp and speed feedforward gain KF are changed according to the above conditions when the speed rises or falls, the position control system will have a high relative gain without compromising the stability of the control system. It can be operated in a system close to the speed control system, and the tracking of the motor can be improved.

Here, the function that determines the velocity feedforward is
In addition to the straight lines shown in the figure, there are also S-shaped curves and (
The present invention may be implemented by using a curve such as b), or by incorporating the portion added by the present invention into the function generator 4.

In addition, although the output of the position detector 2 was used as the current position,
Instead, the present invention can also be applied using command current values managed by the function generator 4.

"Effects of the Invention" As described above, according to the present invention, if the position loop gain and speed feedforward gain are changed while maintaining a certain relationship when the speed rises or falls, the stability of the control system is not compromised. Since the followability of the motor is improved, there is an effect that a stable and highly accurate servo control device can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a conventional motor servo control device,
FIG. 3 is a block diagram approximating the velocity feedback system to a quadratic equation, and FIG. 4 is a relationship diagram illustrating the relationship between the position loop gain and velocity feedforward gain of the present invention.
5, 6(a) and 6(b) show the absolute value of the difference between the current position and the positioning target position for explaining the present invention,
FIG. 3 is a relationship diagram showing the relationship with speed feedforward gain Kp. 1 Motor, 2. Position detector, 3. Differential element, 4.
Function generator, 5.10.12...Adder, 6 Integral element, 7...Position amplifier, 8...Speed feed forward amplifier, 9...Speed detection amplifier, 11...Speed amplifier, 13 ... Absolute value circuit, 14... Gain determiner diagram ↑

Claims (1)

[Claims] 1. At least the position of the motor is detected to obtain a position signal and a speed signal, and the deviation between the position command given from a function generator and the position signal, and the speed given from the function generator In a servo control device having a control system that calculates a speed command using a feedforward signal and controls the motor so that a deviation between the speed command obtained by the calculation and the speed signal becomes zero, the speed rise The position loop gain K_p and the velocity feedforward gain K_F are changed at least at one time or at the time of falling while maintaining the relationship K_p=1/a(1-K_F) (where a is constant). Servo control device for the motor.