Method for detecting contact position

• US 6,008,612 A
• Filed: 10/30/1998
• Issued: 12/28/1999
• Est. Priority Date: 11/29/1996
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Tanaka, Toshiki, Kachi, Mitsuyasu
• Primary Examiner(s): Nappi, Robert E.
• Assistant Examiner(s): Duda, Rina I.
• Application Number:
  US09/182,207
• Time in Patent Office: 424 Days
• Field of Search: 318/560, 318/568.16, 318/568.11, 318/568.1, 318/638, 318/652, 318/671, 318/677, 318/265, 318/266, 318/609, 318/610, 318/565-567, 318/580
• US Class Current: 318/652
• CPC Class Codes: G05B 19/401 characterised by control arrangements for measuring, e.g. calibration and initialisation, measuring workpiece for machining purposes G05B19/19 takes precedence
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/37405 Contact detection between workpiece and tool, probe, feeler
• CPC Class Codes: G05B 2219/37411 Measure contact from force and velocity detection

Abstract

A movable body is moved towards an object for contact, it is determined whether a representative load for driving load such as a current instruction value for a servo amplifier providing controls for movement of the movable body has exceeded a reference value or not, and when the current instruction value exceeds the reference value, positional data for the body at this point of time is written in a memory, difference between the current instruction value and the reference value at this point of time and on is accumulated, and when the accumulated difference value reaches a specified value, a position indicated by the positional data in the memory is regarded as a contact position.

Claims

1. A contact position determining method for detecting a contact position at which a movable body contacts an object for contact comprising:

moving said body in a direction said object;

determining whether a representative value for driving a load, said representative value comprising at least one of;

a speed integration instruction value, a current instruction value, and a current feedback value in PI controls, by a servo section providing controls for movement has exceeded a preset reference value or not;

writing positional data for said body in a memory when the representative value for driving the load exceeds the reference value;

accumulating a difference between the representative value for driving the load and the reference value after the representative value for driving the load has exceeded the reference value; and

regarding a position indicated by the positional data stored in said memory as a contact position when the accumulated difference reaches a preset specified value.

2. A contact position detecting method according to claim 1 further comprising:

subjecting a speed integration instruction value, a current instruction value, or a current feedback value to integration with a time equal to the period of cyclic noise; and

regarding the integrated value as a representative value for driving the load.

3. A contact position detecting method according to claim 1 further comprising:

measuring a speed integration instruction value, a current instruction value, or a current feedback value for one rotation of a motor that drives said body;

writing a load fluctuation component value computed from the measured value for one rotation of the motor in said memory for each rotation of said motor;

executing load fluctuation compensation for the speed integration instruction value, the current instruction value, or the current feedback value based on the load fluctuation component value stored in said memory; and

regarding the value obtained after the compensation as the representative value for driving the load.

4. A contact position detecting method according to claim 1 further comprising:

measuring a speed integration instruction value, a current value, or a current feedback value during movement of said body;

writing a load fluctuation component value for said body at each position obtained from the measured value in said memory;

executing load fluctuation compensation for the speed integration instruction value, the current value, or the current feedback value based on the load fluctuation component value stored in said memory; and

regarding the value obtained after the compensation as the representative value for driving the load.

5. A contact position detecting method according to claim 1 further comprising:

executing feed forward correction to a current instruction with a sinusoidal wave signal having a cycle equal to that of a load fluctuation component with a constant cycle and a constant amplitude specified to a motor in current instruction control in said servo section; and

regarding a current instruction value before the feed forward correction or a speed integration instruction value in PI control as the representative value for driving the load.

6. A contact position detecting method according to claim 1 further comprising:

computing an external disturbance compensating current value with an external disturbance observer in current instruction control in said servo section;

executing feed forward correction to a current instruction according to the external disturbance compensating current value; and

regarding a current instruction value before the feed forward correction or a speed integration instruction value in PI controls as the representative value for driving the load.

7. A contact position detecting method according to claim 1 further comprising:

immediately moving said body away from said object when a contact position is detected.

8. A contact position determining method for detecting a contact position at which a movable body contacts an object for contact comprising:

moving said body in a direction of said object;

calculating a time differentiation of a representative value for driving a load, said representative value comprising at least one of;

a speed integration instruction value, a current instruction value, and a current feedback value in PI controls, by a servo section providing controls for movement;

determining whether the time-differentiated value has exceeded a preset reference value or not; and

regarding a position indicated by positional data for said body as a contact position when the time-differentiated value has exceeded the reference value.

9. A contact position detecting method according to claim 8 further comprising:

subjecting a speed integration instruction value, a current instruction value, or a current feedback value to integration with a time equal to the period of cyclic noise; and

regarding the integrated value as a representative value for driving the load.

10. A contact position detecting method according to claim 8 further comprising:

measuring a speed integration instruction value, a current instruction value, or a current feedback value for one rotation of a motor that drives said body;

writing a load fluctuation component value computed from the measured value for one rotation of the motor in said memory for each rotation of said motor;

executing load fluctuation compensation for the speed integration instruction value, the current instruction value, or the current feedback value based on the load fluctuation component value stored in said memory; and

regarding the value obtained after the compensation as the representative value for driving the load.

11. A contact position detecting method according to claim 8 further comprising:

measuring a speed integration instruction value, a current value, or a current feedback value during movement of said body;

writing a load fluctuation component value for said body at each position obtained from the measured value in said memory;

executing load fluctuation compensation for the speed integration instruction value, the current value, or the current feedback value based on the load fluctuation component value stored in said memory; and

regarding the value obtained after the compensation as the representative value for driving the load.

12. A contact position detecting method according to claim 8 further comprising:

executing feed forward correction to a current instruction with a sinusoidal wave signal having a cycle equal to that of a load fluctuation component with a constant cycle and a constant amplitude specified to a motor in current instruction control in said servo section; and

regarding a current instruction value before the feed forward correction or a speed integration instruction value in PI control as the representative value for driving the load.

13. A contact position detecting method according to claim 8 further comprising:

computing an external disturbance compensating current value with an external disturbance observer in current instruction control in said servo section;

executing feed forward correction to a current instruction according to the external disturbance compensating current value; and

regarding a current instruction value before the feed forward correction or a speed integration instruction value in PI controls as the representative value for driving the load.

14. A contact position detecting method according to claim 8 further comprising:

immediately moving said body away from said object when a contact position is detected.

15. A contact position determining method for detecting a contact position at which a movable body contacts an object for contact comprising:

moving said body in a direction of said object;

calculating a time differentiation of a representative value for driving a load, said representative value comprising at least one of;

a speed integration instruction value, a current instruction value, and a current feedback value in PI controls, by a servo section providing controls for movement;

determining whether the time-differentiated value has exceeded a preset reference value or not;

writing positional data for said body in a memory when the time-differentiated value has exceeded the reference value;

accumulating a difference between the time-differentiated value and the reference value after the time-differentiated value has exceeded the reference value; and

regarding a position indicated by the positional data stored in said memory as a contact position when the accumulated value has reached a preset specified value.

16. A contact position detecting method according to claim 15 further comprising:

subjecting a speed integration instruction value, a current instruction value, or a current feedback value to integration with a time equal to the period of the cyclic noise; and

regarding the integrated value as a representative value for driving the load.

17. A contact position detecting method according to claim 15 further comprising:

measuring a speed integration instruction value, a current instruction value, or a current feedback value for one rotation of a motor that drives said body;

writing a load fluctuation component value computed from the measured value for one rotation of the motor in said memory for each rotation of said motor;

executing load fluctuation compensation for the speed integration instruction value, the current instruction value, or the current feedback value based on the load fluctuation component value stored in said memory; and

regarding the value obtained after the compensation as the representative value for driving the load.

18. A contact position detecting method according to claim 15 further comprising:

measuring a speed integration instruction value, a current value, or a current feedback value during movement of said body;

writing a load fluctuation component value for said body at each position obtained from the measured value in said memory;

executing load fluctuation compensation for the speed integration instruction value, the current value, or the current feedback value based on the load fluctuation component value stored in said memory; and

regarding the value obtained after the compensation as the representative value for driving the load.

19. A contact position detecting method according to claim 15 further comprising:

executing feed forward correction to a current instruction with a sinusoidal wave signal having a cycle equal to that of a load fluctuation component with a constant cycle and a constant amplitude specified to a motor in current instruction control in said servo section; and

regarding a current instruction value before the feed forward correction or a speed integration instruction value in PI control as the representative value for driving the load.

20. A contact position detecting method according to claim 15 further comprising:

computing an external disturbance compensating current value with an external disturbance observer in current instruction control in said servo section;

executing feed forward correction to a current instruction according to the external disturbance compensating current value; and

regarding a current instruction value before the feed forward correction or a speed integration-instruction value in PI controls as the representative value for driving the load.

21. A contact position detecting method according to claim 15 further comprising:

immediately moving said body away from said object when a contact position is detected.

22. A contact position determining method for detecting a contact position at which a movable body contacts an object for contact comprising:

moving said body in a direction of said object;

writing positional data for said body during this movement in time series in a memory;

calculating a time-differentiation of a representative value for driving a load, said representative value comprising at least one of;

a speed integration instruction value, a current instruction value, and a current feedback value in PI controls, by a servo section providing controls for movement;

determining whether the time-differentiated value has exceeded a preset reference value or not;

accumulating a difference between the time-differentiated value and the reference value at the point in time and on, when the time-differentiated value has exceeded the reference value;

calculating an average of the time-differentiated values between the point in time when the time-differentiated value has exceeded the reference value and the accumulated difference value has reached the specified value when the time-differentiated value exceeds the reference value, and estimating a point in time when the representative value for driving the load has exceeded the preset reference value;

reading out positional data at the estimated point in time from said memory; and

regarding a position indicated by the positional data as a contact position.

23. A contact position detecting method according to claim 22 further comprising:

subjecting a speed integration instruction value, a current instruction value, or a current feedback value to integration with a time equal to the period of a cyclic noise; and

regarding the integrated value as a representative value for driving the load.

24. A contact position detecting method according to claim 22 further comprising:

measuring a speed integration instruction value, a current instruction value, or a current feedback value for one rotation of a motor that drives said body;

writing a load fluctuation component value computed from the measured value for one rotation of the motor in said memory for each rotation of said motor;

executing load fluctuation compensation for the speed integration instruction value, the current instruction value, or the current feedback value based on the load fluctuation a component value stored in said memory; and

regarding the value obtained after the compensation as the representative value for driving the load.

25. A contact position detecting method according to claim 22 further comprising:

measuring a speed integration instruction value, a current value, or a current feedback value during movement of said body;

writing a load fluctuation component value for said body at each position obtained from the measured value in said memory;

executing load fluctuation compensation for the speed integration instruction value, the current value, or the current feedback value based on the load fluctuation component value stored in said memory; and

regarding the value obtained after the compensation as the representative value for driving the load.

26. A contact position detecting method according to claim 22 further comprising the steps of:

executing feed forward correction to a current instruction with a sinusoidal wave signal having a cycle equal to that of a load fluctuation component with a constant cycle and a constant amplitude specified to a motor in current instruction control in said servo section; and

regarding a current instruction value before the feed forward correction or a speed integration instruction value in PI control as the representative value for driving the load.

27. A contact position detecting method according to claim 22 further comprising:

computing an external disturbance compensating current value with an external disturbance observer in current instruction control in said servo section;

executing feed forward correction to a current instruction according to the external disturbance compensating current value; and

regarding a current instruction value before the feed forward correction or a speed integration instruction value in PI controls as the representative value for driving the load.

28. A contact position detecting method according to claim 22 further comprising:

immediately moving said body away from said object when a contact position is detected.