Positioning control system

• US 5,469,414 A
• Filed: 11/23/1992
• Issued: 11/21/1995
• Est. Priority Date: 11/22/1991
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Okamura, Eiji
• Primary Examiner(s): Pascal, Robert J.
• Assistant Examiner(s): DINH, TAN X
• Application Number:
  US07/980,928
• Time in Patent Office: 1,093 Days
• Field of Search: 369/32, 369/43, 369/44.27, 369/44.28, 369/44.34, 369/44.35, 360/77.02, 360/75, 360/78.05, 360/78.06
• US Class Current: 360/78.06
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/34047 Dsp digital signal processor
• CPC Class Codes: G05B 2219/41192 Compensation for different response times, delay of axis
• CPC Class Codes: G05B 2219/41355 Electro magnetic coil actuator, voice coil
• CPC Class Codes: G05B 2219/41367 Estimator, state observer, space state controller
• CPC Class Codes: G05B 2219/43025 Acceleration, deceleration is polynomial, derivative is zero on stop position
• CPC Class Codes: G05B 2219/43034 Form of profile, ramp, trapezoid, S-curve, exponential
• CPC Class Codes: G11B 21/083 on discs
• CPC Class Codes: G11B 5/5547 "Seek" control and circuits therefor G11B5/5556 takes precedence

Abstract

A positioning control system for a controlled device, such as a disk drive head, estimates a moving time for moving the controlled device from a current position of the controlled device to a newly designated position. The system sets the estimated moving time as a target moving time. Positioning elements then move the controlled device to the designated position in response to the target moving time. Positioning elements may include an actuator for moving the controlled device, a position detector for tracking movement of the controlled device, and a control element for controlling the actuator. The control element calculates a trajectory for the controlled device to follow based on the target moving time, and controls the actuator based on the calculated trajectory and controlled device position as determined by the position detector. The control system may also have a position correcting element included in the control element. The correcting element compares the actual position of the controlled device with a calculated position of the controlled device and makes necessary adjustments.

Claims

1. A positioning control system for a controlled device comprising:

drive means for moving and positioning said controlled device to a designated position;

position detecting means for detecting the position of said controlled device; and

arithmetic control means for controlling said drive means in accordance with the position of said controlled device detected by said position detecting means and said designated position, wherein said arithmetic control includes;

moving time calculating means for calculating the target moving time for moving said controlled device by a certain moving distance from a current position of said controlled device to said designated position thereof;

gain calculating means for calculating a gain in accordance with said target moving time and said moving distance;

trajectory calculating means for calculating a target trajectory using an algebraic polynomial represented by said target moving time, said gain and an elapsed time, said algebraic polynomial at least making a target position said designated position when said elapsed time is equal to the target moving time; and

following control means for controlling said drive means in accordance with said target trajectory calculated by said trajectory calculator and the position of said controlled device detected by said position detecting means while causing the position of said controlled device to follow said target trajectory.

2. A positioning control system as set forth in claim 1, wherein the target trajectory is expressed by a polynomial, V₀ (t/T)^k [1-(t/T)]^j, where T denotes target moving time, t denotes an elapsed time whose initial value is 0, V₀ denotes a constant, powers j and k are positive numbers, and the power j is set at 3 or larger.

3. A positioning control system as set forth in claim 1, wherein the target trajectory is expressed by a polynomial, V₀ (t/T)^k [1-(t/T)]^g, where T denotes a target moving time, t denotes an elapsed time whose initial value is 0, V₀ denotes a constant, a power g is set at 3 or larger, and a power k is set 2 or larger.

4. A positioning control system as set forth in claim 1, wherein the moving time calculation means estimates the moving time of the controlled device between the current position and the designated position in proportion to a square root of a cubed root of the moving distance.

5. A positioning control system as set forth in claim 1, wherein the position of the controlled device is detected by the position detecting means, an estimated speed of the controlled device is calculated in accordance with a detected position information for each sample and a driving amount of the drive means which moves the controlled device, and a speed feedback gain corresponding the estimated speed is set.

6. A positioning control system as set forth in claim 1, wherein a normalized time is calculated based on a detected position information from the position detecting means, and a response delay is added to the calculated normalized time so as to compensate for response delay.

7. A positioning control system as set forth in claim 1, wherein a constant speed period is provided between an acceleration period and a deceleration period which are determined in accordance with the target trajectory when the moving distance of the controlled device is longer than a predetermined value.

8. A positioning control system as set forth in claim 1, wherein the controller device is comprised of a magnetic head which is movable on a magnetic disk and said drive means is comprised of an actuator for positioning the magnetic head at a designated track position on the magnetic disk.

9. A positioning control system as set forth in claim 1, wherein the controlled device is comprised of an optical head which is movable on an optical disk and the drive means is comprised of an actuator for positioning the optical head at a designated position on the optical disk.

10. A positioning control system as set forth in claim 1, wherein the controller device is comprised of a print head which is movable on a printing sheet and the drive meads is comprised of an actuator for positioning the print head at a designated position on the printing sheet.

11. A positioning control system as set forth in claim 1, wherein the trajectory generating means calculates the target trajectory which makes a derivative of high order of a target acceleration curve zero at the time of the start of movement of the controlled device and at the time of completion of movement thereof, in accordance with the moving distance designated by a host device and a resonance frequency characteristics which the controlled device per se has, and wherein the follow control means control the driving means so that the controlled device is moved following the target trajectory to be positioned at the designated position.

12. A positioning control system for a magnetic head on a magnetic disk, comprising:

an actuator for moving and positioning said magnetic head to a designated track position on said magnetic disk;

position detecting means for detecting the track position of said magnetic head; and

arithmetic control means for controlling said actuator in accordance with the track position of said magnetic head detected by said position detecting means and said designated track position, wherein said arithmetic control means includes;

moving time calculating means for calculating a target moving time for moving said magnetic head by a certain moving distance from a current track position of said magnetic head to said designated track position thereof;

gain calculating means for calculating a gain in accordance with said target moving time and said moving distance;

trajectory calculating means for calculating a target trajectory using an algebraic polynomial represented by said target moving time, said gain and an elapsed time, said algebraic polynomial at least making a target track position said designated track position when said elapsed time is equal to the target moving time; and

following control means for controlling said actuator in accordance with said target trajectory calculated by said trajectory calculator and the track position of said magnetic head detected by said position detecting means, while causing the track position of said magnetic head to follow said target trajectory.

13. A positioning control system as set forth in claim 12, wherein the system further comprises position correcting means which stores a position correction value that is calculated by taking into account an amount of displacement of the controlled device in a given position, and wherein the trajectory generating means predicts a position correction value when the movement of the controlled device is completed in accordance with the current position of the controlled device and the calculated target moving time with reference to the position correcting means, and corrects previously the target trajectory in accordance with the predicted position correction value, and wherein the follow control means positions the control device while causing the same to follow the corrected target trajectory.

14. A positioning control system as set forth in claim 12, wherein the system further comprises:

calculating means which predicts and calculates the target moving time as a function of the current position of the controlled device and the entire moving distance; and

position correction means which stores a position correction value that is calculated by taking into account an amount of displacement of the controlled device in a given position, and wherein a true entire moving distance from the start of movement of the controlled device to the completion thereof is adapted to be sequentially calculated, in the calculating means and the position correcting means.

15. A positioning control system as set forth in claim 14, wherein an amplitude of the target trajectory is adapted to be corrected using the approximate entire moving distance obtained by a sequential approximation, and to be calculated the target trajectory taking into account the accuracy of distance equal to or smaller than a track pitch.

16. A positioning control system as set forth in claim 15, wherein the controlled device is adapted to be positioned taking into account the correction of the amplitude of the target trajectory, only when the entire moving distance is relatively small.

17. A positioning control system for a magnetic head on a magnetic disk comprising:

an actuator for moving and positioning the magnetic head at the designated track position;

position detecting means for detecting the track position of the magnetic head;

arithmetic control means for controlling the actuator in accordance with the track position of the magnetic head detected by the position detecting means and the designated track position; and

a position correction table which stores a position correction value that is calculated taking into account an amount of displacement of the magnetic head in a given track position on the magnetic disk, wherein the arithmetic control means includes;

trajectory generating means for calculating target trajectory in accordance with an entire moving distance between a current track position of the magnetic head and the designated track position; and

follow control means for controlling the actuator in accordance with the target trajectory from the trajectory generating means and the position of the magnetic head detected by the position detecting means, said follow control means causing said actuator to move the magnetic head to follow the target trajectory, and wherein the trajectory generating means predicts a position correction value in accordance with the target moving time with reference to the position correction table, and corrects the previous target trajectory in accordance with the predicted position correction table, and controls the actuator so that the magnetic head is moved following the target trajectory to be positioned at the designated track position.