JPH01292508A - Servo controller - Google Patents

Abstract

PURPOSE:To perform the servo position/speed control in a short tact time by using an acceleration correcting means to change the acceleration of a commanded speed based on the difference between a commanded position and an actual shift position. CONSTITUTION:The transfer of data is carried out between the control units 1 and 2 consisting of the CPUs, etc., via a 2-port RAM 3. At this time point, the unit 2 reads the droop value and calculates the optimum acceleration alphaM from this droop value. Then a speed VA=VN-1+alphaM is calculated (VN-1: preceding control command). An acceleration table is included into a program to the droop value and the alphaM is read out to the read droop value by reference to the acceleration table. For the value of said table, the alphaM is decreased in response to the increase of the droop value. In such a constitution, the tact time is shortened without increasing the motor load.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a servo control device that controls position and speed using a motor.

(Prior Art) FIG. 3 is a block diagram of a servo control device such as that disclosed in Japanese Patent Application Laid-open No. 59-8320!1, in which (1) is a microprocessor (10).
(2) is a second control unit consisting of the same CPU (20), and both units (1) and (2) are configured with control software and calculations. It consists of memories (11) and (21) for storing result data, and timers (12) and (22) for operating the CPU at a constant calculation cycle.
A two-point RAM (3) is provided for exchanging data between the two control units (1) and (2).

The second control unit (2) controls the servo A M P (
Servo output I/F (23) consisting of a D/A converter for output to 4) and a servo input I/F (23) consisting of a counter for counting input from an encoder and detecting the current position of the motor. Equipped with I/F (24). (5) is a servo motor, and (6) is an encoder for detecting the position of this motor (5).

The first control unit (1) controls the target position of the servo position,
Since it performs general control of other push buttons, etc., its calculation cycle is relatively slow, about 40 m5ec. In addition, the second control unit (2) is a control unit dedicated to servo calculations, such as position loop calculations for servo control in boat fishing, so the calculation time is 2 m5ec, etc., compared to the first control unit (2).
It is shorter than 1).

FIG. 4 is a flowchart of the content of control in the first control unit (1), particularly the speed control portion. Here, the current position of the motor is X. The target position of the motor movement this time is X. shall be. - Boat fishing requires multiple motors (x
, has a motor for each direction for movement in the y, z directions, etc.).

etc. are expressed as vectors, but here they are expressed as scalar quantities for simplicity. Furthermore, processing as a vector quantity is almost the same. The remaining distance calculation in step (302) is the remaining distance = xD-xC, and the calculation of the deceleration speed in step (303) is the deceleration speed. Binding, remaining distance - from the above remaining distance
Read vo from the deceleration speed table. Step (304
) is calculated as VA=VN-1+α, where the previous output speed is VN-1, the acceleration speed is 6, and the acceleration of the servo motor (5) is α. Next, if the maximum speed of the servo motor is VM, then in step (305) vA and v
o is compared, and if ■ that one is smaller than ■ 2, vA and VD are further compared in step (306). In this case, v
A is ■. If it is smaller, we know that we can now accelerate further, so the output is ■. shall be. Similarly step (30
5) to (307), it is determined whether the current speed is accelerating, constant speed (maximum speed), or decelerating. - Speed control command v
A, VD, and VM are created. FIG. 5 is a control block diagram of the second control unit, where (201) is smoothing, (202) is integrator, (203) is proportional calculator, and (204) is D/A conversion. Vessel, and (205)
indicates a differentiator.

(Problem to be solved by the invention) The conventional servo control device is constructed as described above.
In the above control system, the integrator (
202), that is, the difference between the command position and the actual movement position (
Since there are restrictions on droop (hereinafter referred to as droop), it is controlled to be below a certain value. When this constant value is exceeded, it is called droop over and is treated as a system error. That is, if the commanded speed is too high than the actual motor capability, the motor will not be able to catch up, the droop will increase, a system error will occur, and the motor will stop. For this reason, it is impossible to increase the acceleration of the command so that droop over does not occur. Therefore, there is a problem in that whether the movement is short or long distance, the acceleration is set to a low value and the overall takt time (operation time) becomes long. Particularly in the control of robots, the change pattern of droop varies greatly depending on whether a heavy object is grasped or not, even for the same speed command pattern, and commands are always issued with acceleration assuming a heavy load, which increases the takt time as a whole. In general, droop moves in a similar manner to its speed pattern, depending on the mechanism being controlled. Therefore, it is difficult to obtain good position and velocity commands by simply controlling the acceleration using the inverse ratio of the droop.

This invention was made to solve the above problems, and aims to provide a servo control device that can control the servo in a short takt time by achieving the highest acceleration regardless of load fluctuations. purpose.

[Means for Solving the Problems] A servo control device according to the present invention is a servo control device that controls position and speed using a motor. It is equipped with correction means.

[Function] In this invention, the acceleration of the commanded speed can be changed by the difference between the commanded position and the actual movement position by the acceleration correction means, and thereby the servo position, position, and speed can be controlled in a short takt time. can be done.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. This invention reads out the droop calculated by the second control unit of the conventional example in the first control unit, and uses this to change the acceleration in the calculation of the speed control command created by the first control unit. This creates an overall optimal speed control command.

Next, the calculation of the speed control command in this invention will be explained with reference to the flowchart shown in FIG. Note that this embodiment is a modification of the acceleration calculation part of step (304) in FIG. 2 of the conventional example, and the parts other than (304) are the same as in FIG. 2, so a description thereof will be omitted. Now,
Step (402) is to read the current droop value from the second control unit (2) via the 2-point RAM (3), and step (403) is to calculate the optimal acceleration α2 from this droop value. Step (40)
4) calculates the velocity VA from the acceleration α calculated in step (403). At this time, VA is the previous speed control command VN-, plus a, VA=VN-1+(EM
It is calculated by By the way, various methods can be considered for the method of step (403), but one method is to have a table of acceleration for droop on the program and calculate αN by referring to the table for the read droop. . This method is very simple but effective. At this time, by configuring the table so that the acceleration value decreases as the droop increases, the droop increases, and the acceleration decreases as the droop approaches the droop over, which has the effect of suppressing the increase in droop. With this table method, when the load is small, the acceleration is increased, and when the load is large, the droop is larger than the light load, so the acceleration is suppressed, and the overall optimum acceleration can be obtained. Overall, the load on the motor does not increase, and the entire system can be controlled in a short takt time.

FIG. 2 shows another embodiment of the present invention, in which step (406) internally calculates the first-order delay of the speed control command that is output from the first control unit to the second control unit. The time constant at this time takes into account the delay of the system,
Settings must be made to accommodate this delay. Methods for realizing first-order delay calculations are well known, and there are various methods.

As an example of a simple method, however, if the cumulative value is the cumulative value + current human car output, and the output at this time is D, then by making the above time constant match the time constant of the device, D can be calculated in step (402). This is the expected droop reading. Therefore, by creating a table similar to the above embodiment based on the difference between the droop reading and D, the optimum acceleration α can be determined.

Note that this embodiment allows more detailed droop fluctuations to be known than the above embodiments, provides more optimal acceleration, shortens layer takt time, and reduces load on the motor. The increase is not that great.

〔Effect of the invention〕

As explained above, according to the present invention, the first control unit reads the droop value from the second control unit, and changes the acceleration of the speed control command created by the first control unit, thereby controlling the motor. Takt time can be shortened without increasing the load.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of speed command creation in the servo control device of the present invention, FIG. 2 is a flowchart of speed command creation according to another embodiment, FIG. 3 is a block diagram of a conventional servo control device, and FIG. 4 5 is a flowchart of speed command creation in the first control unit, and FIG. 5 is a control block diagram of the second control unit. (1)...first control unit, (2)...second control unit, (4)...servo AMP. (5)... Servo motor, (6)... Encoder. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] A servo control device that controls position and speed using a motor, the servo control device comprising an acceleration correction means for changing the acceleration of the command speed based on the difference between the command position and the actual movement position.