Contact detecting method and an apparatus for the same

• US 6,233,497 B1
• Filed: 09/16/1998
• Issued: 05/15/2001
• Est. Priority Date: 09/18/1997
• Status: Expired due to Fees

• 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): Grant, William
• Assistant Examiner(s): RODRIGUEZ, PAUL L
• Application Number:
  US09/153,889
• Time in Patent Office: 972 Days
• Field of Search: 700/63, 700/61, 700/64, 700/150, 700/160, 700/164, 700/170, 700/188, 700/190, 700/173, 451/9
• US Class Current: 700/173
• CPC Class Codes: B24B 49/02 according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent B24B49/12 takes precedence
• CPC Class Codes: B24B 49/16 taking regard of the load
• CPC Class Codes: B24B 5/14 for grinding conical surfaces, e.g. of centres
• CPC Class Codes: G05B 19/4015 going to a reference at the beginning of machine cycle, e.g. for calibration
• CPC Class Codes: G05B 2219/37405 Contact detection between workpiece and tool, probe, feeler

Abstract

Under the conditions that the tool is movable in an X-axial direction for approaching a work W and in a Y-axial direction perpendicular to the X-axial direction, the tool is moved at a specified speed in the X-axial direction to make the tool approach a work W and at the same time the tool is reciprocally moved at a specified frequency and a specified amplitude to detect a load fluctuation component for the tool in the X-axial direction during movement of the tool, and contact between the tool and the work W is detected according to this load fluctuation component.

Claims

1. A contact detecting method of detecting contact between a movable body and an object for contact, said movable body movable in a first direction for approaching said object for contact and in a second direction slanting at a certain angle against said first direction, comprising the steps of:

moving said movable body at a specified speed in said first direction to make said movable body approach said object for contact and simultaneously moving said movable body in said second direction to generate fluctuation in load to said movable body in said first direction during movement of said movable body; and

detecting a load fluctuation in said first direction.

2. A contact detecting method according to claim 1;

further comprising the step of detecting load fluctuation in other directions; and

detecting contact between said movable body and said object for contact based on a combination of load fluctuation in a plurality of directions.

3. A contact detecting method according to claim 1, wherein detecting said load fluctuation in said first direction comprises;

detecting a speed integration instruction value, a current instruction value, or a current feedback value in PI control of a servo unit for driving in a direction as an object for detection of load fluctuation as a representative value for driving load;

storing said representative values for driving load and positional data of said movable body during a specified period of time in time series;

determining, when an increase rate of said representative value for driving load exceeds a specified value during said specified period of time, that contact occurred;

detecting a point of time when said representative value for driving load starts changing from this point of time when it is determined that contact has occurred; and

regarding as a contact position a position indicated by positional data of said movable body in said first direction at this point of time when said representative value for driving load starts changing.

4. A contact detecting method according to claim 1, wherein detecting said load fluctuation in said first direction comprises;

detecting a speed integration instruction value, a current instruction value, or a current feedback value in PI control of a servo unit for driving in a direction as an object for detection of load fluctuation as a representative value for driving load;

storing said representative values for driving load and positional data of said movable body during a specified period of time in time series;

determining, when a frequency component of reciprocal movement appears in said representative value for driving load during said specified period of time, that contact has occurred;

detecting a point of time when said representative value for driving load starts changing from this point of time when it is determined that contact has occurred; and

regarding as a contact position a position indicated by positional data of said movable body in said first direction at this point of time when said representative value for driving load starts changing.

5. A contact detecting method according to claim 1 further comprising the steps of:

specifying a zone where it is expected for load fluctuation in said first direction to cyclically increase according to a frequency of reciprocal movement due to reciprocal movement in said first direction or in said second direction; and

determining whether said movable body and said object for contact has contacted to each other by checking whether a change rate of load fluctuation in this zone has exceeded a specified rate or not.

6. A contact detecting method according to claim 1, wherein detecting the load fluctuation in the first direction comprises;

measuring a representative value for driving load in a non-contact state previously together with positional data of said movable body and storing the measured value as a reference change rate;

detecting a speed integration instruction value, a current instruction value, or a current feedback value in PI control of a servo unit for driving in a direction as an object for detection of load fluctuation as a representative value for driving load;

determining as a contact point a position of said movable body in said first direction at a point of time when a difference between this representative value for driving load and said reference change rate or a change rate of said difference exceeds a specified rate;

detecting a point of time when said representative value for driving load starts changing from this point of time when it is determined that contact has occurred; and

regarding as a contact position a position indicated by positional data of said movable body in said first direction at said point of time when said representative value for driving load starts changing.

7. A contact detecting method according to claim 1;

wherein said movable body is moved reciprocally in said second direction, and wherein a frequency and an amplitude of said reciprocal movement are changeably set according to materials of said movable body or said object for contact.

8. A contact detecting method of detecting contact between a movable body and an object for contact, said movable body movable in a first direction to approach said object for contact, comprising the steps of:

making said movable body approach said object for contact by way of moving said movable body in said first direction to generate fluctuation in load to said movable body in a second direction, which slants at a certain angle against said first direction, during movement of said movable body in said first direction;

wherein said movable body and said object for contact are made closer to each other by superimposing reciprocal movement with a specified frequency and a specified amplitude in said first direction onto movement of said movable body; and

detecting said load fluctuation to determine contact between said movable body and said object for contact according to said load fluctuation.

9. A contact detecting method of detecting contact between a movable body and an object for contact, said movable body movable in a first direction for approaching said object for contact and in a second direction slanting at a certain angle against said first direction, comprising the steps of:

moving said movable body in said first direction as well as in said second direction to generate fluctuation in load to said movable body in the first direction or in the second direction during movement of said movable body; and

detecting said load fluctuation to determine contact between said movable body and said object for contact according to said load fluctuation.

10. A contact detecting method according to claim 9;

wherein said movable body and said object for contact are made closer to each other by superimposing reciprocal movement with a specified frequency and a specified amplitude in one of said first direction or in said second direction onto movement of said movable body.

11. A contact detecting method according to claim 9;

wherein said movable body and said object for contact are made closer to each other by superimposing reciprocal movement with a specified frequency and a specified amplitude in said first direction and also reciprocal movement with a specified frequency and a specified amplitude in said second direction onto movement of said movable body.

12. A contact detecting method of detecting a contact between a movable body and an object for contact, said movable body movable in a first direction for approaching said object for contact and said object for contact movable in a second direction slanting at a certain angle against said first direction, comprising the steps of:

moving said movable body in said first direction at a specified speed to make said movable body approach said object for contact and also moving said object for contact in said second direction; and

detecting fluctuation in load to said object for contact in said second direction during movement of said movable body and said object for contact to determine contact between said movable body and said object for contact according to said load fluctuation.

13. A contact detecting method according to claim 12;

wherein said movable body and said object for contact are made closer to each other by superimposing reciprocal movement with a specified frequency and a specified amplitude in said first direction to movement of said movable body.

14. A contact detecting method according to claim 12, wherein said movable body is movable not only in said first direction but also in a third direction slanting at a certain angle against said first direction, and wherein said movable body approaches said object for contact in said first direction at a specified speed and also reciprocally moves at a specified frequency and a specified amplitude in said third direction.

15. A contact detecting method according to claim 12;

wherein reciprocal movement with a specified frequency and a specified amplitude in said second direction is superimposed to movement of said object for contact.

16. A contact detecting apparatus for detecting a contact between a movable body and an object for contact, said movable body movable in a first direction for approaching said object for contact as well as in a second direction, which slants at a certain angle against said first direction, said apparatus comprising:

a control unit for moving said movable body at a specified speed in the first direction for approaching said object for contact and also for simultaneously moving said movable body in said second direction to generate fluctuation of load to said movable body during movement of the movable body in said first direction; and

a contact determining unit for detecting said load fluctuation and determining according to said load fluctuation that said movable body and said object for contact have contacted each other.

17. A contact detecting apparatus according to claim 16;

wherein said contact determining unit is operating to detect load fluctuation in a plurality of directions and determine that said movable body and said object for contact have contacted each other according to a combination of load fluctuations in said plurality of directions.

18. A contact detecting apparatus according to claim 16 further comprising:

a storing unit for storing, assuming an instruction value for speed integration, an instruction value for a current, or a current feedback value in PI controls of a servo unit for driving in a direction as an object for detection of load fluctuation as a representative value for driving load, said representative value for driving load during a specified period of time and positional data for said movable body in said first direction in time series; and

a contact position identifying unit for detecting a point of time when said representative value for driving load starts changing from a point of time when it is determined by said contact determining unit that the contact between said movable body and said object for contact has occurred when a change rate of said representative value for driving load exceeds a specified value during said specified period of time and regarding as a contact position a position indicated by said positional data of said movable body in said first direction at this point of time when the change starts.

19. A contact detecting apparatus according to claim 16 further comprising:

a storing unit for storing, assuming an instruction value for speed integration, an instruction value for a current, or a current feedback value in PI controls of a servo unit for driving in a direction as an object for detection of load fluctuation as a representative value for driving load, said representative value for driving load during a specified period of time and positional data for said movable body in said first direction in time series; and

a contact position identifying unit for detecting a point of time when said representative value for driving load starts changing from the point of time when it is determined by said contact determined unit that contact has occurred when a frequency component of reciprocal movement appears in said representative value for driving load during said specified period of time, and regarding as a contact position a position indicated by positional data of said movable body in said first direction at this point of time when said representative value for driving load starts changing.

20. A contact detecting apparatus according to claim 16;

wherein said contact determining unit specifies a zone in which it is expected for the load fluctuation in said first direction to cyclically increase in response to a frequency of reciprocal movement of said movable body in said first direction or in said second direction, an d determines whether contact between said movable body and s aid object for contact has occurred by checking whether a change rate in load has exceeded a specified rate or not in this zone.

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

a storing unit for storing, assuming an instruction value for speed integration, an instruction value for a current, or a current feedback value in PI controls of a servo unit for driving in a direction as an object for detection of load fluctuation as a representative value for driving load, the representative value for driving load in a non-contact state together with positional data of said movable body as a reference change rate;

wherein said contact determining unit determines as a contact-determined position a position of said movable body in said first direction at a point of time when a difference between the representative value for driving load and said reference change rate stored in said storing unit or a change rate in the difference has exceeded a specified value; and

a contact position identifying unit which detects a point of time when said representative value for driving load starts changing from a point of time when it is determined that contact has occurred, and regarding as a contact position a position indicated by positional data of said movable body in said first direction at a point of time when the representative value for driving load starts changing.

22. A contact apparatus according to claim 16;

wherein said control unit changeably sets a frequency or an amplitude of a reciprocal movement of said movable body according to materials of said movable body and said object for contact.

23. A contact detecting apparatus for detecting contact between a movable body and an object for contact, said movable body movable in a first direction for approaching said object for contact, said apparatus comprising:

a control unit for providing controls for making said movable body approach said object for contact by way of moving said movable body in said first direction to generate load fluctuation to said movable body in a second direction, which slants at a certain angle against said first direction during movement of said movable body in said first direction;

wherein said control unit makes said movable body approach said object for contact by superimposing reciprocal movement of said movable body in said first direction with a specified frequency and a specified amplitude; and

a contact determining unit detecting said load fluctuation and determining according to said load fluctuation that contact between said movable body and said object for contact has occurred.

24. A contact detecting apparatus for detecting contact between a movable body and an object for contact, said movable body movable in a first direction for approaching said object for contact as well as in a second direction, which slants at a certain angle against said first direction, said apparatus comprising:

a control unit operating to control said movable body to approach said object for contact in said first direction and in said second direction at a specified speed respectively; and

a contact determining unit for detecting fluctuation of load to said movable body in said first direction or in said second direction during movement of said movable body and determining according to said load fluctuation that said movable body and said object for contact have contacted each other.

25. A contact detecting apparatus according to claim 24;

wherein said control unit provides controls for making said movable body approach said object for contact by superimposing reciprocal movement with a specified frequency and a specified amplitude in said first direction or in said second direction to movement of said movable body.

26. A contact detecting apparatus according to claim 24;

wherein said control unit provides controls for making said movable body approach said object for contact by superimposing reciprocal movement with a specified frequency and a specified amplitude in said first direction as well as reciprocal movement with a specified frequency and a specified amplitude in said second direction to movement of said movable body.

27. A contact detecting apparatus for detecting contact between a movable body and an object for contact comprising:

a control unit for providing controls for making said movable body approach said object for contact by way of moving said movable body at a specified speed in a first direction for approaching said object for contact and also moving said object for contact in a second direction slanting at a certain angle against said first direction; and

a contact determining unit for detecting fluctuation of load to said object for contact in said second direction during movement of said movable body as well as of said object for contact and determining according to said load fluctuation that said movable body and said object for contact have contacted each other.

28. A contact detecting apparatus according to claim 27;

wherein said control unit provides controls for making said movable body approach said object for contact by superimposing reciprocal movement with a specified frequency and a specified amplitude in said first direction to movement of said movable body.

29. A contact detecting apparatus according to claim 27;

wherein said control unit provides controls for reciprocally moving said movable body at a specified frequency and a specified amplitude in said second direction while moving said movable body in said first direction at a specified speed for making said movable body approach said object for contact.

30. A contact detecting apparatus according to claim 27;

wherein said control unit superimposes reciprocal movement with a specified frequency and a specified amplitude in a third direction to movement of said movable body.