Position control apparatus and position control method

• US 20020151988A1
• Filed: 03/29/2002
• Published: 10/17/2002
• Est. Priority Date: 03/30/2001
• Status: Active Grant

• Current Assignee: Toshiba Kikai Kabushiki Kaisha
• Original Assignee: Toshiba Kikai Kabushiki Kaisha
• Inventors: Fujita, Jun, Shiba, Kazuhiro, Hamamura, Minoru
• Granted Patent: US 6,889,115 B2
• Time in Patent Office: Days
• US Class Current: 700/13
• 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 2219/41041 Compensation pulses as function of direction movement
• CPC Class Codes: G05B 2219/41045 For several modes and feed speeds, a table, registers for several backlash

Abstract

A position control apparatus for positioning a control object connected with a motor via a transmission mechanism so as to track a variable position reference varying with time, having a reference generating unit for generating the variable position reference; a control deviation generating unit for generating control deviation of the control object based on the variable position reference and a detected position of the control object or these and a detected rotational position of the motor; a servo control unit for generating a control quantity to make the control object track the variable position reference based on the control deviation and controlling the driving of the motor; a tracking error compensating unit having a first and second compensating unit of different modes for compensating for the control deviation or for correcting the detected rotational position of the motor used for generation of the control deviation so as to suppress tracking error of the control object from the variable position reference caused by mechanical transmission error of the transmission mechanism; and a compensation selecting unit for selecting a compensating unit to be operated from the first and second compensating unit based on whether the detected position of the control object changes in a period after the control object stops and before the variable position reference is input again to the control deviation generating unit.

Claims

1. A position control apparatus for positioning a control object connected with a motor via a transmission mechanism so as to track a variable position reference varying with time, comprising:

a reference generating means for generating said variable position reference;

a control deviation generating means for generating control deviation of the control object based on said variable position reference and a detected position of said control object;

a servo control means for generating a control quantity to make said control object track said variable position reference based on said control deviation and controlling the driving of said motor;

a tracking error compensating means having a first and second compensating means of different modes for compensating for said control deviation so as to suppress tracking error of said control object from said variable position reference caused by mechanical transmission error of said transmission mechanism; and

a compensation selecting means for selecting a compensating means to be operated from said first and second compensating means based on whether the detected position of said control object changes in a period after said control object stops and before said variable position reference is input again to said control deviation generating means.

2. A position control apparatus as set forth in claim 1, wherein

said first compensating means compensates for said control deviation so as to suppress said tracking error during a period after said variable position reference is again input and before said control object start to move again;

said second compensating means compensates for said control deviation so as to suppress said tracking error with a predetermined compensation amount in accordance with a feed direction of said variable position reference after said variable position reference is again input;

said compensation selecting means selects said first compensating means when the detected position of said control object does not change during a period after said control object stops and before said variable position reference is again input to said control deviation generating means and selects said second compensating means when the detected position of said control object changes.

3. A position control apparatus as set forth in claim 1 or 2, further comprising a compensation determining means for determining a compensation amount required for said second compensating means to perform compensation based on the detected position of said control object and a detected rotational position of said motor when said second compensating means is selected by said compensation selecting means.

4. A position control apparatus as set forth in claim 3, wherein said compensation determining means holds first and second compensation amounts corresponding to directions of movement of said control object and determines said first and second compensation amounts in accordance with a direction of change of the detected position of said control object.

5. A position control apparatus as set forth in claim 4, wherein said second compensating means selects one of said first and second compensating means determined by said compensation determining means and compensates for said control deviation in accordance with a feed direction of said variable position reference input again.

6. A position control apparatus for positioning a control object connected with a motor via a transmission mechanism so as to track a variable position reference varying with time, having:

a reference generating means for generating said variable position reference;

a control deviation generating means for generating control deviation of the control object based on said variable position reference and a detected position of said control object;

a servo control means for generating a control quantity to make said control object track said variable position reference based on said control deviation and controlling the driving of said motor;

a tracking error compensating means having first and second compensating means of different modes for correcting a detected rotational position of said motor to be used to generate said control deviation so as to suppress tracking error of said control object from said variable position reference caused by mechanical transmission error of said transmission mechanism; and

a compensation selecting means for selecting a compensating means to be operated from said first and second compensating means based on whether the detected position of said control object changes in a period after said control object stops and before said variable position reference is input again to said control deviation generating means.

7. A position control apparatus as set forth in claim 6, wherein

said first compensating means corrects the detected rotational position of said motor generating said control deviation so as to suppress said tracking error during a period after said variable position reference is input again and before said control object start to move again;

said second compensating means corrects the detected rotational position of said motor to be used to generate said control deviation so as to suppress said tracking error with a predetermined compensation amount in accordance with a feed direction of said variable position reference after said variable position reference is input again; and

said compensation selecting means selects said first compensating means when the detected position of said control object does not changes during a period after said control object stops and before said variable position reference is input to said control deviation generating means again and selects said second compensating means when the detected position of said control object changes.

8. A position control apparatus as set forth in claim 6 or 7, further comprising a compensation determining means for determining a compensation amount which said second compensating means requires to perform compensation based on the detected position of said control object and a detected rotational position of said motor when said second compensating means is selected by said compensation selecting means.

9. A position control apparatus as set forth in claim 8, wherein said compensation determining means holds first and second compensation amounts corresponding to directions of movement of said control object and determines said first and second compensation amounts in accordance with a direction of change of the detected position of said control object.

10. A position control apparatus as set forth in claim 9, wherein said second compensating means selects one of said first and second compensation amounts determined by said compensation determining means and corrects the detected rotational position of said motor to be used to generate said control deviation in accordance with a feed direction of said variable position reference input again.

11. A position control method comprising:

generating a variable position reference varying by time;

generating a control deviation of a control object connected with a motor via a transmission mechanism from said variable position reference based on said variable position reference and a detected position of said control object;

driving said motor by generating a control quantity for making said control object track said variable position reference based on said control deviation;

positioning said control object by making it track said variable position reference;

detecting whether the detected position of said control object changes or not during a period after said control object stops at a target position and before said variable position reference to a next target position is generated;

selecting one of a first and a second compensating means in accordance with a detected result of change of the detected position of said control object; and

compensating for said control deviation by the selected compensating means so as to suppress the tracking error of said control object from said variable position reference caused by mechanical transmission error of said transmission mechanism.

12. A position control method comprising:

generating a variable position reference varying by time;

generating a control deviation of a control object connected with a motor via a transmission mechanism from said variable position reference based on said variable position reference, and a detected position of said control object, and a detected rotational position of said motor;

driving said motor by generating a control quantity for making said control object track said variable position reference based on said control deviation;

positioning said control object by making it track said variable position reference;

detecting whether the detected position of said control object changes or not during a period after said control object stops at a target position and before said variable position reference to a next target position is generated;

selecting one of a first and a second compensating means in accordance with a detected result of change of the detected position of said control object; and

correcting the detected rotational position to be used to generate said control deviation by the selected compensating means so as to suppress the tracking error of said control object from said variable position reference caused by a mechanical transmission error of said transmission mechanism.