Servo control apparatus, servo control method, and non-transitory computer-readable medium, with filter added to proportional term calculated at high speed

• US 9,933,759 B2
• Filed: 04/20/2017
• Issued: 04/03/2018
• Est. Priority Date: 04/28/2016
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Tsuneki, Ryoutarou, Ikai, Satoshi
• Primary Examiner(s): Ro, Bentsu
• Assistant Examiner(s): Agared, Gabriel
• Application Number:
  US15/492,448
• Publication Number:
  US 20170315513A1
• Time in Patent Office: 348 Days
• Field of Search: 318569
• CPC Class Codes: G05B 11/42 for obtaining a characteristic which is both proportional and time-dependent, e.g. P. I., P. I. D.

Abstract

A servo control apparatus includes a subtractor configured to calculate a difference between a first command value for controlling a servo motor, and a first detection value from the servo motor; an integral term creation unit configured to create an integral term based on an output of the subtractor; an internal division processing unit configured to internally divide the first command value; a subtractor configured to calculate a difference between an output of the internal division processing unit and the first detection value; a proportional term creation unit configured to create a proportional term based on the subtractor; and a adder configured to add an output of the integral term creation unit and an output of the proportional term creation unit, in which a calculation period calculated by the proportional term creation unit is shorter than a calculation period calculated by the integral term creation unit.

Claims

1. A servo control apparatus, comprising:

a first subtractor configured to calculate a difference between a first command value being a periodic signal for controlling a servo motor, and a first detection value from the servo motor;

an integral term creation unit configured to create an integral term by integrating an output of the first subtractor, and multiplying an integral value thereof by a first coefficient;

an internal division processing unit configured to internally divide the first command value by a predetermined period;

a second subtractor configured to calculate a difference between an output of the internal division processing unit and the first detection value;

a proportional term creation unit configured to create a proportional term by multiplying an output of the second subtractor by a second coefficient; and

a first adder configured to add an output of the integral term creation unit and an output of the proportional term creation unit, and configured to output an additional value thereof as a second command value for controlling the servo motor,

wherein a calculation period calculated by way of the proportional term creation unit is shorter than a calculation period calculated by way of the integral term creation unit.

2. The servo control apparatus according to claim 1, wherein the internal division processing unit divides a quantity, which has been changed in an update period of the first command value, by a calculation period calculated by way of the proportional term creation unit.

3. The servo control apparatus according to claim 1, further comprising:

a feedforward term creation unit configured to create a feedforward term by differentiating a third command value for controlling the servo motor, and multiplying a differential value thereof by a third coefficient;

a third subtractor configured to calculate a difference between the third command value and a second detection value from the servo motor;

a feedback term creation unit configured to create a feedback term from an output of the third subtractor;

a timing adjustment unit configured to adjust timing of an output of the feedforward term creation unit;

a second adder configured to add an output of the feedforward term creation unit and an output of the feedback term creation unit, and configured to output an additional value thereof as the first command value to the first subtractor; and

a third adder configured to add an output of the timing adjustment unit and an output of the feedback term creation unit, and configured to output an additional value thereof as the first command value being timing-adjusted to the internal division processing unit.

4. The servo control apparatus according to claim 3, wherein the timing adjustment unit advances timing by a quantity of delay in the internal division processing unit.

5. The servo control apparatus according to claim 3, wherein the first command value and the first command value being timing-adjusted are speed command values, the first detection value is a speed detection value, the second command value is a current command value, the third command value is a position command value, and the second detection value is a position detection value.

6. A servo control method for a servo control apparatus, the method comprising:

calculating a first difference between a first command value being a periodic signal for controlling a servo motor, and a first detection value from the servo motor;

creating an integral term by integrating the first difference, and multiplying an integral value thereof by a first coefficient;

internally dividing the first command value by a predetermined period;

calculating a second difference between the value internally divided and the first detection value;

creating a proportional term by multiplying the second difference by a second coefficient; and

adding the integral term and the proportional term, and outputting an additional value thereof as a second command value for controlling the servo motor,

wherein a calculation period for calculating the proportional term is shorter than a calculation period for calculating the integral term.

7. The servo control method according to claim 6, further comprising:

creating a feedforward term by differentiating a third command value for controlling the servo motor, and multiplying a differential value thereof by a third coefficient;

calculating a third difference between the third command value and a second detection value from the servo motor;

creating a feedback term from the third difference;

adjusting timing of the feedforward term;

adding the feedforward term and the feedback term, and outputting an additional value thereof as the first command value; and

adding the feedforward term being timing-adjusted and the feedback term, and outputting an additional value thereof as the first command value being timing-adjusted.

8. A non-transitory computer-readable medium storing a servo control program thereon, causing a computer as a servo control apparatus to execute the processing of:

calculating a first difference between a first command value being a periodic signal for controlling a servo motor, and a first detection value from the servo motor;

creating an integral term by integrating the first difference, and multiplying an integral value thereof by a first coefficient;

internally dividing the first command value by a predetermined period;

calculating a second difference between the value internally divided and the first detection value;

creating a proportional term by multiplying the second difference by a second coefficient; and

adding the integral term and the proportional term, and outputting an additional value thereof as a second command value for controlling the servo motor,

wherein a calculation period for calculating the proportional term is shorter than a calculation period for calculating the integral term.