Motor control system

• US 7,248,014 B2
• Filed: 06/16/2003
• Issued: 07/24/2007
• Est. Priority Date: 06/28/2002
• Status: Expired due to Fees

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Iwashita, Yasusuke, Kawamura, Hiroyuki, Genma, Eiji
• Primary Examiner(s): Leykin; Rita
• Application Number:
  US10/461,331
• Publication Number:
  US 20040000890A1
• Time in Patent Office: 1,499 Days
• Field of Search: 318/638, 318/611, 318/568.18, 318/609, 318/610, 318/560, 318/630, 318/452, 318/629, 318/561, 700245-264
• US Class Current: 318/638
• CPC Class Codes: B30B 1/103 operated by screw means
• CPC Class Codes: G05B 19/19 characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path

Abstract

A motor control system capable of securing stability and rapidity of motion even in a machine where the stability varies in accordance with a position of a driven member. The driven member and a motor for driving the driven member are operatively connected through a transmission mechanism including a nonlinear element such that a rate of change of the position of the driven member with respect to the position of the motor varies in dependence on the position of the motor. Optimum values of multiplier factors of operation constants with respect to the position of the driven member or the rotational position of the motor for the position control and the velocity control are stored in a data table. The values of the multiplier factors of the operation constants for a present position of the driven member or a present position of the motor are determined using the data table and the determined values of the multiplier factors are multiplied by reference operation constants to update the operation constants. The position and/or velocity control processing is performed using the updated optimum operation constants in accordance with the present position of the driven member or the present rotational position of the motor.

Claims

1. A motor control system for controlling a servomotor for driving a driven member through a transmission mechanism for mechanically connecting the servomotor and the driven member, comprising:

a servo controller having a position control section for performing position control processing for feedback controlling a position of the driven member, and a velocity control section for performing velocity control processing for feedback controlling a velocity of the driven member;

a host controller for issuing a position command commanding a position of the driven member to said servo controller, and outputting information on operation constants for the position control processing by the position control section and/or the velocity control processing by the velocity control section, to be corresponding to the commanded position; and

operation constant varying unit for varying operation constants for the position control processing and/or the velocity control processing in accordance with the information on the operation constants outputted from said host controller,

wherein the driven member comprises a mold of an electric press machine for performing a press work, and the operation constants have different values in the vicinity of a bottom dead point where the press work is performed and in the vicinity of a top dead point where the press work is not performed.

2. A motor control system according to claim 1, wherein the operation constant for the position control processing is a position gain for obtaining a velocity command from a deviation between the position command issued from said host controller and a position of the driven member detected by a position detector, the servo motor is mechanically connected with the driven member through the transmission mechanism such that a rate of change of the position of the driven member with respect to change of a position of the servomotor is not constant, and said operation constant varying unit varies the position gain in accordance with the commanded position of the driven member.

3. A motor control system according to claim 1, wherein said operation constant varying unit comprises a storage unit for storing data representing relation between the position of the driven member and the operation constants, and determines values of the operation constants for the present position of the driven member using the stored data.

4. A motor control system according to claim 3, wherein said storage unit is provided in said host controller.

5. A motor control system according to claim 1, said operation constant varying unit comprises a storage unit for storing a mathematical equation representing a relation between the position of the driven member and the operation constants, and determines values of the operation constants for the present position of the driven member using the mathematical equation.

6. A motor control system according to claim 5, wherein said storage unit is provided in said host controller.

7. A motor control system according to claim 1, wherein said operation constant varying unit starts varying of the operation constants upon receipt of a signal from an external device or a signal produced by internal processing in the motor control system.

8. A motor control system according to claim 7, wherein the determination of values of the operation constants is performed by said host controller.

9. A motor control system according to claim 1, wherein said operation constant varying unit starts varying of the operation constants upon receipt of a program command.

10. A motor control system according to claim 9, wherein the determination of values of the operation constants is performed by said host controller.

11. A motor control system according to claim 1, wherein said operation constant varying unit determines values of the operation constants to be varied smoothly.

12. A motor control system according to claim 11, wherein the varying of the operation constant is performed by said host controller.

13. A motor control system according to claim 1, wherein the operation constants for the position control section and/or the velocity control section are set to upper limit values until an initial position of the driven member is established after a power supply to the motor control system is turned on.

14. A motor control system according to claim 1, wherein said operation constant varying unit varies the operation constants in accordance with a present rotational position of the servomotor mechanically connected with the driven member by the transmission mechanism.

15. A motor control system according to claim 14, wherein said operation constant varying unit stores a data table representing relation between the rotational position of the servomotor and the operation constant, and determines values of the operation constants for the present rotational position of the servomotor using the data table.

16. A motor control system according to claim 15, wherein said data table is provided in said host controller.

17. A motor control system according to claim 14, said operation constant varying unit stores a mathematical equation representing a relation between the rotational position of the servomotor and values of the operation constants, and determines values of the operation constants for the present rotational position of the servomotor using the mathematical equation.

18. A motor control system according to claim 17, wherein the determination of values of the operation constants for the present rotational position of the servomotor is performed by said host controller.

19. A motor control system controlling a servomotor driving a driven member through a nonlinear transmission mechanism mechanically connecting the servomotor and the driven member, comprising:

a position controller generating position control commands according to a position input command, reference position operation constants and feedback of a present position of the driven member, the position control commands controlling a position of the driven member;

a velocity controller generating velocity control commands according to an input velocity command, reference velocity operation constants and feedback of a present velocity of the driven member, the velocity control commands controlling a velocity of the servomotor to control a velocity of the driven member; and

a constant multiplier calculator adjusting the reference position operation constants and/or the reference velocity operation constants according to the present position of the driven member, wherein the position and velocity of the driven member is controlled through the nonlinear transmission according to the present position of the driven member.

20. The system of claim 19, wherein the reference position operation constant comprises a position gain, and the reference velocity operation constants comprise at least one of a proportional gain and an integral gain.

21. The system of claim 19, wherein the reference position operation constants and the reference velocity operation constants are stored as data values according to a position of the driven member.

22. The system of claim 19, wherein the constant multiplier calculator adjusts the reference position operation constants by a small amount and adjusts the reference velocity operation constants by a large amount when the present position of the driven member is near a top dead point.

23. The system of claim 19, wherein the motor control system is a full-closed loop control system.