JP2008148449A - Motor position control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a motor position controller that does not trip even when a load abruptly fluctuates and is capable of smooth positioning. <P>SOLUTION: The motor position controller includes: a position control block 10 that compares position data 12 detected from a motor with a position command 11 and generates a speed command from the position error; a speed control block 20 that compares the speed command with speed data detected from the motor and generates a torque command from the velocity error; and a torque control block 30 that carries out torque control suitable for the motor. The speed control block 20 includes a speed limit function 21 for inputting the speed command generated at the position control block 10. The speed limit function 21 works as follows: when a speed command exceeds a speed limit set value, the speed limit set value is output as a speed command; and when a speed command is equal to or lower than a speed limit set value, an input speed command value is output and the speed command is limited so that the position error is not abruptly reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor position control method for controlling the position of a single-axis motor, and more particularly to a motor position control method that takes into account rapid fluctuations in load.

  In machine tool applications, conventionally, when controlling multiple axes, it has been necessary to perform position control while performing interpolation so that the hand position locus does not deviate even under sudden load fluctuations.

  Therefore, in the servo control system in which there are a plurality of motors and control loops and the controlled object is controlled, when the torque in at least one control loop exceeds the torque limit value of the motor and becomes saturated, the torque of the motor A method has been proposed in which a position loop gain corresponding to a limit value is obtained by calculation, the position loop gain is set as the position loop gain of all control loops, and the position control loop is operated by the position loop gain (for example, Patent Documents). 1).

On the other hand, in general industrial applications, control capable of positioning at low cost is required. For simple positioning applications, a method of instructing an inverter from a sequencer to control an induction motor has been mainstream.
JP 7-84648 A

  In recent years, as the processing speed of microcomputers has improved and the capacity of built-in memory has increased, controllers with PC functions and NC functions and motor speed control functions have been consolidated into a single microcomputer. It is going

  Against this background, demands for servo motors and brushless motors are changing, and a control system capable of smooth positioning without tripping is indispensable with a low-cost and simplified system configuration.

  The problem to be solved by the invention is that, when positioning is performed, a trip cannot be made in response to a sudden load fluctuation.

  In the case of position control, if the load becomes heavy and the torque in the control loop becomes close to the torque limit value of the motor, the position deviation will accumulate too much. After that, when the load suddenly decreases, the speed command value suddenly increases to reduce the accumulation of position deviation, the motor speed exceeds the maximum rotation speed, and the speed limit function trips. For this reason, the motor stopped and smooth positioning could not be performed.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a motor position control device capable of smooth positioning at a low cost without tripping even when a load fluctuates rapidly.

In order to solve the above-described conventional problems, a motor position control method according to the present invention includes a position control block that compares position data detected from a motor with a position command and generates a speed command from a position deviation, and the speed command and the motor In a motor position control device having a speed control block that compares the detected speed data and generates a torque command from a speed deviation, and a torque control block that performs torque control suitable for the motor, the speed control block includes the position control It has a speed limit function that inputs the speed command generated in the block, and when the speed command exceeds the speed limit set value, the speed limit function outputs the speed limit set value as a speed command and sets the speed limit. When the value is less than or equal to the value, the input speed command value is output, and the speed command is limited so as not to reduce the position deviation suddenly. That.

  Further, the speed limit set value of the speed limit function can be changed by a parameter.

  According to the motor position control method of the present invention, an excessive speed command due to a sudden change in load is limited by the speed limit function, so that a trip due to overspeed does not occur.

  Moreover, since the speed limit function can be changed depending on parameters, it can be handled only by the software difference of the microcomputer that combines the positioning controller function and the motor drive control function.

  Therefore, it is possible to provide a motor position control device that is capable of low-cost and smooth positioning without tripping with respect to a sudden change in load.

  The motor position control device compares the position data detected from the motor with the position command and generates a speed command from the position deviation, and compares the speed command with the speed data detected from the motor and compares the speed command with the torque from the speed deviation. A speed control block that generates a command and a torque control block that performs torque control suitable for the motor, and the speed control block has a speed limit function that inputs a speed command generated by the position control block, and The speed limit function outputs the speed limit set value as a speed command when the speed command exceeds the speed limit set value, and outputs the input speed command value when the speed command is less than or equal to the speed limit set value. Limit the speed command so that the position deviation does not suddenly decrease. The speed limit setting value of the speed limit function can be changed by a parameter.

  Specific examples will be described below. FIG. 1 is a block diagram showing each control function block of the motor position control apparatus according to the first embodiment of the present invention, in which a speed limit function is provided in the speed control block.

  In FIG. 1, the position control block 10 improves the response at the time of starting the motor and the deviation counter 13 that counts the deviation between the position command 11 and the position data 12 detected by the encoder (or CS signal), as in the conventional case. It is composed of a speed feed forward 14 and a position error amplifier 15 that determines position control responsiveness, and outputs a speed command.

  The speed control block 20 includes a speed limit function 21 for inputting the speed command generated in the position control block 1, speed detection processing means 22 for detecting the speed from the encoder (or CS signal), and a speed error for determining the speed responsiveness. It comprises an amplifier 23 and speed integration processing means 24 that determines the rigidity of the speed loop, and generates a torque command.

  The speed limit function 21 outputs the speed limit set value as a speed command when the speed command exceeds the speed limit set value, and outputs the input speed command value when the speed command is less than or equal to the speed limit set value. The speed command is limited so that the position deviation is not suddenly reduced.

  The torque control block 30 is composed of a torque filter 31 and a torque limit 32 with a torque command as an input, and drives a motor.

  A feature of the present invention is that a speed limit function is provided in the speed control block, and this point will be described in detail with reference to FIG.

  FIG. 2 is a flowchart for explaining the speed limit function. First, a speed command is generated in the position control block 10 based on a position command 11 that is an operation command from the host controller as in the conventional case. If the generated speed command value is less than or equal to the speed limit set value, the speed command value is compared with the speed data detected by the speed detection processing means 22 to generate a torque command, and the motor is passed through the torque control block 30. Drive.

  If the load fluctuates rapidly during the operation, the position deviation of the position control block 10 increases. The speed limit function 21 of the speed control block 20 always compares whether or not the input speed command value is equal to or less than the speed limit set value. If it is equal to or less than the speed limit set value, the input speed command value is used as it is. Output. When the speed limit set value is exceeded, the speed limit set value is output in response to the input speed command.

  Thus, if the speed command value generated by the position control block is equal to or less than the speed limit set value of the speed limit function, the positioning operation is completed in the same time as the normal operation while absorbing the influence of the load fluctuation. On the other hand, if the speed limit set value is exceeded, the control following the excessive speed command generated by the sudden load fluctuation is not performed and the speed limit is set by the limit value, so that a trip due to overspeed can be prevented.

  It should be noted that since the speed command generated by a sudden load fluctuation is limited by the speed limit setting value, it takes time until the actual speed approaches the speed command value for normal operation. If the positioning is completed while the actual speed is about to follow the speed command value for normal operation, the positioning time will be longer than that for normal operation. This point will be described with reference to the drawings.

  In FIG. 3, the vertical axis represents the speed command value, which is a speed trip command value and a speed limit setting value that trip from the top at an overspeed. The horizontal axis is the operating time. By setting the speed trip command value as an overspeed protection function higher than the speed limit setting value, it can be tripped even if overspeed occurs due to other reasons such as runaway, and the motor can be stopped and protected .

  FIG. 3 compares the operation time for the speed command value in the normal operation with no speed limit with the operation time when the speed limit function is provided.

  First, the case where there is no speed limit will be described. The actual speed command value (indicated by a thick line) commanded from the position control block 10 operates so as to follow the operation time when there is no speed limit.

  On the other hand, with the speed limit function of the present invention, the speed limit setting value is output as the speed command even if the actual speed command value is input exceeding the speed limit setting value. Operates as indicated by the value (dotted line).

  The areas indicating the movement distance until the two patterns indicated by the bold line and the dotted line follow are the same.

In other words, during the triangular area (shaded area) shown above the speed limit set value, driving is performed with a torque command generated from the speed command limited by the speed limit set value. Furthermore, since the drive is performed with the torque command generated from the speed command limited by the speed limit setting value between the parallelogram area (shaded area) of the same area as the triangular area indicated by the hatched line, it is normal compared to when there is no speed limit. The time required to follow the speed command value of the operation becomes longer.

  The speed limit setting value can be changed by microcomputer software. In addition, such a motor position control method taking into account sudden load fluctuations can be dealt with only by the software difference of the microcomputer that combines the positioning controller function and the motor drive control function into one, and can be provided at low cost. When the positioning controller function and the motor drive control function are configured separately, the speed limit function of the present invention may be added to either.

  The motor position control method of the present invention is useful for general industrial equipment and the like for which low cost is required as an application for smoothly positioning only one axis without tripping.

Functional block diagram of the motor position control apparatus of Embodiment 1 of the present invention The flowchart explaining the speed limit function in Example 1 of this invention Explanatory drawing of speed limit function in Embodiment 1 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Position control block 11 Position command 12 Position data 13 Deviation counter 14 Speed feed forward 15 Position error amplifier 20 Speed control block 21 Speed limit function 22 Speed detection processing means 23 Speed error amplifier 24 Speed integration processing means 30 Torque control block 31 Torque filter 32 Torque limit

Claims (2)

A position control block that compares the position data detected from the motor with the position command and generates a speed command from the position deviation, and a speed control that generates a torque command from the speed deviation by comparing the speed command and the speed data detected from the motor In the motor position control device having a block and a torque control block for performing torque control suitable for the motor, the speed control block has a speed limit function for inputting a speed command generated by the position control block, and the speed The limit function outputs the speed limit set value as a speed command when the speed command exceeds the speed limit set value, and outputs the input speed command value when the speed command is below the speed limit set value. A motor position control method characterized by limiting a speed command so as not to reduce the deviation suddenly. The motor position control method according to claim 1, wherein a speed limit set value of the speed limit function can be changed by a parameter.