Servomotor controller, servomotor control method, and computer-readable recording medium

• US 10,175,676 B2
• Filed: 11/29/2017
• Issued: 01/08/2019
• Est. Priority Date: 12/01/2016
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Shinoda, Shougo, Ikai, Satoshi
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US15/825,650
• Publication Number:
  US 20180157236A1
• Time in Patent Office: 405 Days
• CPC Class Codes: F16H 61/0202 the signals being electric F16H61/04 takes precedence
• CPC Class Codes: G05B 11/011 details of the correcting means
• CPC Class Codes: G05B 19/404 characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia G05B19/19, G05B19/41 take precedence
• CPC Class Codes: G05B 2219/41129 Force compensation for non linearity of system
• CPC Class Codes: G05B 2219/41138 Torque compensation
• CPC Class Codes: G05B 2219/41164 How to compensate, for example by injecting compensation signal in comparator of normal loop

Abstract

A servomotor controller includes a connection mechanism configured to transfer power of a servomotor to a driven body; a motor control unit configured to control the servomotor using a position command value; a first force estimation unit configured to estimate a first force estimated value which is a drive force acting on the driven body at a connecting unit with the connection mechanism; a second force estimation unit configured to estimate a second force estimated value serving as a fixed value; a selection unit configured to compare an absolute value of the first force estimated value and an absolute value of the second force estimated value to output the first or second force estimated value having the larger absolute value; and a compensation amount generation unit configured to generate a compensation amount for compensating the position command value on the basis of the first or second force estimated value.

Claims

1. A servomotor controller comprising:

a servomotor;

a driven body configured to be driven by the servomotor;

a connection mechanism configured to connect the servomotor and the driven body and transfer power of the servomotor to the driven body;

a position command generation unit configured to generate a position command value for the driven body;

a motor control unit configured to control the servomotor using the position command value;

a first force estimation unit configured to estimate a first force estimated value which is a drive force acting on the driven body at a connecting unit with the connection mechanism;

a second force estimation unit configured to estimate a second force estimated value serving as a fixed value;

a selection unit configured to compare an absolute value of the first force estimated value and an absolute value of the second force estimated value to output the first, or second force estimated value having the larger absolute value; and

a compensation amount generation unit configured to generate a compensation amount for compensating the position command value generated by the position command generation unit on the basis of the first or second force estimated value output from the selection unit.

2. The servomotor controller according to claim 1, wherein

the compensation amount generation unit uses, as the compensation amount, a sum of a product of the first or second force estimated value output from the selection unit and a first coefficient and a product of the first or second force estimated value output from the selection unit, a distance from the servomotor to the connecting unit, and a second coefficient.

3. The servomotor controller according to claim 1, wherein

the second force estimated value is a value obtained by adjusting a drive force acting on the driven body to be estimated to a predetermined constant value having a sign corresponding to a direction of a position command created by the position command generation unit.

4. The servomotor controller according to claim 1, wherein

the second force estimated value is a predetermined constant value or a fixed value of the first force estimated value estimated by the first force estimation unit when a command speed or a command acceleration of the position command created by the position command generation unit is no more than a desired value.

5. The servomotor controller according to claim 1, further comprising:

a switching unit configured to switch its output from a value output from the selection unit to the first force estimated value estimated by the first force estimation unit when a command speed or a command acceleration of the position command value generated by the position command generation unit exceeds a desired value.

6. The servomotor controller according to claim 1, wherein

the compensation amount generated by the compensation amount generation unit is passed through a filter when the selection unit switches its output from the second force estimated value to the first force estimated value or from the first force estimated value to the second force estimated value.

7. The servomotor controller according to claim 5, wherein

the compensation amount generated by the compensation amount generation unit is passed through a filter when the switching unit switches its output from the second force estimated value to the first force estimated value or from the first force estimated value to the second force estimated value.

8. The servomotor controller according to claim 1, wherein

the motor control unit includes a speed command creation unit and a torque command creation unit,

the torque command creation unit includes an integrator that integrates at least a speed error, and

the integrator is overwritten when the selection unit switches its output from the second force estimated value to the first force estimated value or from the first force estimated value to the second force estimated value.

9. The servomotor controller according to claim 5, wherein

the motor control unit includes a speed command creation unit and a torque command creation unit,

the torque command creation unit includes an integrator that integrates at least a speed error, and

the integrator is overwritten when the switching unit switches its output from the second force estimated value to the first force estimated value or from the first force estimated value to the second force estimated value.

10. A servomotor control method for controlling a servomotor controller including:

a servomotor;

a driven body configured to be driven by the servomotor; and

a connection mechanism configured to connect the servomotor and the driven body and transfer power of the servomotor to the driven body, the method comprising the steps of;

generating a position command value for the driven body;

estimating a first force estimated value which is a drive force acting on the driven body at a connecting unit with the connection mechanism;

comparing an absolute value of the first force estimated value and an absolute value of the second force estimated value to select the first or second force estimated value having the larger absolute value;

compensating the generated position command value on the basis of the selected first or second force estimated value; and

controlling the servomotor using the compensated position command value.

11. The servomotor control method according to claim 10, wherein

a position command compensation value for compensating the position command value is a sum of a product of the selected first or second force estimated value and a first coefficient and a product of the selected first or second force estimated value, a distance from the servomotor to the connecting unit, and a second coefficient.

12. The servomotor control method according to claim 10, wherein

the second force estimated value is a value obtained by adjusting a drive force acting on the driven body to be estimated to a predetermined constant value having a sign corresponding to a direction of a position command.

13. The servomotor control method according to claim 10, wherein

the second force estimated value is a predetermined constant value or a fixed value of the first force estimated value estimated when a command speed or a command acceleration of the position command is no more than a desired value.

14. The servomotor control method according to claim 10, wherein

the selected force estimated value is switched to the first force estimated value when a command speed or a command acceleration of the generated position command value exceeds a desired value.

15. The servomotor control method according to claim 10, wherein

the compensation amount of the position command value is passed through a filter when the second force estimated value is switched to the first force estimated value or the first force estimated value is switched to the second force estimated value.

16. The servomotor control method according to claim 10, wherein

a speed command is created using the compensated position command value, a torque command is created using the created speed command, and the servomotor is controlled using the torque command,

the torque command is created using an integrator that integrates at least a speed error, and

the integrator is overwritten when the second force estimated value is switched to the first force estimated value or the first force estimated value is switched to the second force estimated value.

17. A non-transitory computer-readable recording medium encoded with a servomotor control program that causes a computer to execute servomotor control of a servomotor controller including:

a servomotor;

a driven body configured to be driven by the servomotor; and

a connection mechanism configured to connect the servomotor and the driven body and transfer power of the servomotor to the driven body, the program causing the computer to execute processing of;

generating a position command value for the driven body;

estimating a first force estimated value which is a drive force acting on the driven body at a connecting unit with the connection mechanism;

comparing an absolute value of the first force estimated value and an absolute value of the second force estimated value to select the first or second force estimated value having the larger absolute value;

compensating the generated position command value on the basis of the selected first or second force estimated value; and

controlling the servomotor using the compensated position command value.