Positional control system and positional control method

• US 6,738,679 B2
• Filed: 04/30/2001
• Issued: 05/18/2004
• Est. Priority Date: 05/08/2000
• Status: Expired due to Term

• Current Assignee: Toshiba Kikai Kabushiki Kaisha (Shibaura Machine Co., Ltd.)
• Original Assignee: Toshiba Kikai Kabushiki Kaisha (Shibaura Machine Co., Ltd.)
• Inventors: Fujita, Jun, Hamamura, Minoru
• Primary Examiner(s): Patel, Ramesh
• Assistant Examiner(s): PHAM, THOMAS K
• Application Number:
  US09/844,284
• Publication Number:
  US 20010054876A1
• Time in Patent Office: 1,114 Days
• Field of Search: 700/56, 700/57, 700/186, 700/189, 318/561, 318/568.15, 318/569, 318/573, 318/600, 318/638
• US Class Current: 700/56
• 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 2219/41032 Backlash
• CPC Class Codes: G05B 2219/41036 Position error in memory, lookup table for correction actual position
• CPC Class Codes: G05B 2219/41074 Learn, calibrate at start for indetermined position, drive until movement
• CPC Class Codes: G05B 2219/41085 Compensation pulses on inversion of direction of rotation, movement

Abstract

A positional control system wherein the position of the controlled object connected to a drive is controlled to a variable target or desired position. A period is determined which starts with a detection of a reversal in the direction of the feed of a positional command Pr as well as the detection of a stoppage of a table 104 as a controlled object and which ends with a detection of the re-start of the movement of the table 104. During the period, a correction amount for correcting a positional deviation E is issued.

Claims

1. A positional control system for controlling a position of a controlled object, comprising:

a driving means connected to the controlled object;

a setting means for setting a variable target position of the controlled object;

a control command generating means for generating a control command in accordance with said variable target position;

a position sensor arranged on said controlled object for detecting a position of the controlled object;

a deviation generating means for generating a deviation between said control command and a detected position of the controlled object;

a servo control means for generating, in accordance with the deviation, a manipulated variable issued to said driving means for causing said controlled object to follow said variable target position; and

,

a tracking error correction means operated from a first time at which a direction in the feed in the variable target position is reversed and the controlled objected is stopped to a second time at which the movement of the controlled object is re-started, for correcting a lost movement for a mechanical non-linear position error caused by a mechanical coupling of the controlled object and the driving means, which appears at the restart time after the stop.

2. A system according to claim 1, wherein said tracking error correction means comprise:

a reversal detector part detecting a reversal in direction of feed;

a movement/stoppage detector part for detecting a movement or stoppage of the controlled object; and

,

a tracking error correcting part for issuing a correcting amount for correcting a correction amount of the lost movement in accordance with signals from said reversal detector and said movement/stoppage detector.

3. A system according to claim 2, wherein said tracking error correcting part holds, in accordance with the direction of the reverse of the feed, a first and second correction amounts of the lost movements having opposed signs and the same absolute value.

4. A system according to claim 2, wherein said movement/stoppage detector part detects the movement or the stoppage of the controlled object based on the signal from said position sensor.

5. A positional control system for controlling a position of a controlled object, comprising:

a driving means connected to the controlled object;

a setting means for setting a variable target position of the controlled object;

a control command generating means for generating a control command in accordance with said variable target position;

a first position sensor arranged on said controlled object for detecting a position of the controlled object;

a second position sensor arranged on said driving means for detecting a driving position of the driving means;

a deviation generating means for generating control deviation of the controlled object in accordance with said control command, the detected position of the controlled object and detected driving position of the driving means;

a servo control means for generating, in accordance with the control deviation, a manipulated variable issued to said driving means for causing said controlled object to follow said variable target position; and

,

a tracking error correction means operated from a first time at which a direction in the feed in the variable target position is reversed and the controlled objected is stopped to a second time at which the movement of the controlled object is re-started, for correcting a lost movement for a mechanical non-linear position error caused by a mechanical coupling of the controlled object and the driving means, which appears at the restart time after the stop.

6. A system according to claim 5, wherein said tracking error correction means comprise:

a reversal detector part detecting a reversal in direction of feed;

a movement/stoppage detector part for detecting a movement or stoppage of the controlled object, and;

a tracking error correcting part for increasing or decreasing a correcting amount for correcting a correction amount of the lost movement in accordance with signals from said reversal detector part and said movement/stoppage detector part.

7. A system according to claim 5, wherein said tracking error correcting part effects a periodical modification of a predetermined amount of the correcting amount for correcting the detected driving position when a reversal in the direction of the feed is detected by the reversal detecting part and when the stoppage of the controlled object is detected by said movement/stoppage detector part, said modification being ceased when a re-start of the controlled object is detected by said movement/stoppage detector part.

8. A system according to claim 5, wherein said movement/stoppage detector part detects the movement or the stoppage based on the signal from said position sensor.

9. A position control method for controlling a position of a controlled object, connected to a driving means comprising the steps of:

setting a variable target position of the controlled object;

generating control command in accordance with said variable target position;

detecting a position of the controlled object by said position sensor arranged on the controlled object;

generating a deviation between said control command and a detected position of the controlled object;

effecting a servo-control by generating, in accordance with the deviation, a manipulated variable issued to said driving means for causing said controlled object to follow said variable target position, and;

correcting a lost movement for a mechanical non-linear position error caused by a mechanical coupling of the controlled object and the driving means, which appears at a restart time after a stop during the period from a first time at which a direction in the feed in the variable target position is reversed and when the controlled objected is stopped to a second time at which the movement of the controlled object is re-started.

10. A method according to claim 9, wherein said tracking error correcting step comprise the steps of:

detecting a reversal in direction of feed;

detecting a stoppage of the controlled object;

correcting said lost movement when a reversal in the direction of the feed and the stoppage of the controlled object are detected, and;

ceasing the correction when a re-start of the controlled objection is detected.

11. A method according to claim 10, wherein said step for correcting the tracking error detects a correction of said controlled deviation by a first or second correction lost movement amount of opposed signs of the same absolute vales which are determined in accordance with the direction of the reversal in the feed.

12. A method according to claim 10, wherein said step for detecting the stoppage and said step for detecting the re-start comprise steps of detecting the stopped and the moved conditions of the controlled object in accordance with the detected signal from the position sensor.

13. A position control method for controlling a position of a controlled object, connected to a driving means comprising the steps of:

setting a variable target position of the controlled object;

generating control command in accordance with said variable target position;

detecting a position of the controlled object by said position sensor arranged on the controlled object;

detecting a driving position of the driving means by the driving position sensor;

generating a deviation from said control command and a detected driving position of the driving means;

effecting a servo-control by generating, in accordance with the deviation, a manipulated variable issued to said driving means for causing said controlled object to follow said variable target position, and;

modifying correcting amount for correcting a lost movement for a mechanical non-linear position error caused by a mechanical coupling of the controlled object and the driving means, which apprears at a restart time after a stop during the period from a first time at which a direction in the feed in the variable target position is reversed and the controlled objected is stopped to a second time at which the movement of the controlled object is re-started.

14. A method according to claim 13, wherein said tracking error correcting step comprise the steps of:

detecting a reversal in direction of feed;

detecting a stoppage of the controlled object;

increasing or decreasing the correction amount for correcting said detected driving position when a reversal in the direction of the feed as well as the stoppage of the controlled object are detected, and;

ceasing the modification of the correction amount when a re-start of the controlled objection is detected.

15. A method according to claim 13, wherein said step for correcting the tracking error detects a periodical modification of a predetermined amount of the correcting amount for correcting the detected driving position when the reversal in the direction of the feed and the stoppage of the controlled object, said modification of the correcting amount being ceased when the restart of the controlled object is detected.

16. A method according to claim 13, wherein said step for detecting the stoppage and said step for detecting the re-start comprise steps of detecting the stopped condition and the moved condition in accordance with the detected signal from the position sensor.