Position control method, position control device, and medium storage device having disturbance suppression function

Abstract

In a position control device having a disturbance suppression function, loop gain is calibrated without stopping disturbance suppression control. The position control device has, for disturbance suppression control, a feedback controller for changing the loop characteristic, a table for storing a target gain according to a disturbance frequency, and a gain calibration section for calibrating open loop gain. The gain is calibrated using a target gain in the table according to the change of the loop characteristic of the feedback controller. Open loop gain can be calibrated without interrupting the disturbance suppression control, so the open loop gain can be accurately calibrated without being affected by disturbance, and accurate position control is possible.

1 . A position control method for controlling a position of an object to a predetermined position by an actuator, comprising:
 a step of computing a position error based on a target position of the object and a current position of the object;   a step of computing a control value in which a disturbance frequency component is suppressed, using a predetermined feedback loop based on the position error and computing a drive value of the actuator by multiplying the control value by a loop gain;   a step of fetching a target loop gain according to the disturbance frequency from a table;   a step of adding disturbance of a measurement frequency to the feedback loop and measuring a loop gain of the feedback loop; and   a step of calibrating the loop gain of the control value computing step based on the measured loop gain and the target loop gain.   
     
     
         2 . The position control method according to  claim 1 , wherein the step of fetching the target loop gain comprises a step of fetching a measurement frequency according to the disturbance frequency, and
 wherein the measurement step comprises a step of adding disturbance of the fetched measurement frequency to the feedback loop, and measuring a loop gain of the feedback loop.   
     
     
         3 . The position control method according to  claim 1 , wherein the step of fetching the measurement frequency comprises a step of fetching a measurement frequency which does not overlap the disturbance frequency. 
     
     
         4 . The position control method according to  claim 1 , wherein the drive value computing step comprises:
 a step of estimating the disturbance frequency according to the position error based on an adaptive control;   a step of computing a control value in which the disturbance frequency component is suppressed, according to the estimated disturbance frequency; and   a step of computing a drive value of the actuator by multiplying the control value by a loop gain.   
     
     
         5 . The position control method according to  claim 4 , further comprising a step of interrupting the estimation of the disturbance frequency according to the position error during calibration of the loop gain. 
     
     
         6 . The position control method according to  claim 4 , wherein the drive value computing step comprises:
 a step of estimating the disturbance frequency according to the position error based on an adaptive control, and changing a constant of a controller according to the estimated disturbance frequency; and   a step of computing a control value in which the disturbance frequency component is suppressed, using the changed controller according to the position error, and multiplying the result by a loop gain, so as to compute a drive value of the actuator.   
     
     
         7 . The position control method according to  claim 4 , wherein the drive value computing step comprises:
 a step of estimating the disturbance frequency according to the position error based on an adaptive control;   a step of changing a constant of a controller constructed with an observer according to the estimated disturbance frequency; and   a computing step of computing a control value in which the disturbance frequency component is suppressed according to the position error, using the changed observer, and multiplying the result by a loop gain, so as to compute a drive value of the actuator.   
     
     
         8 . A position control device for controlling a position of an object to a predetermined position by an actuator, comprising:
 a control unit for computing a position error based on a target position of the object and a current position of the object, computing a control value in which a disturbance frequency component is suppressed, using a predetermined feedback loop based on the position error, and multiplying the result by a loop gain, so as to compute a drive value of the actuator; and   a table for storing a target loop gain according to the disturbance frequency,   wherein the control unit fetches the target loop gain according to the disturbance frequency from the table, adds a disturbance of a measurement frequency to the feedback loop, measures a loop gain of the feedback loop, and calibrates the loop gain in the control value computing step based on the measured loop gain and the target loop gain.   
     
     
         9 . The position control device according to  claim 8 , wherein the control unit fetches a measurement frequency according to the disturbance frequency from the table, adds a disturbance of the fetched measurement frequency to the feedback loop, and measures a loop gain of the feedback loop. 
     
     
         10 . The position control device according to  claim 8 , wherein the control unit fetches a measurement frequency which does not overlap with the disturbance frequency from the table. 
     
     
         11 . The position control device according to  claim 8 , wherein the control unit estimates the disturbance frequency according to the position error based on an adaptive control, computes a control value in which the disturbance frequency component is suppressed according to the estimated disturbance frequency, and multiplies the result by a loop gain, so as to compute a drive value of the actuator. 
     
     
         12 . The position control device according to  claim 11 , wherein the control unit interrupts the estimation of the disturbance frequency according to the position error during calibration of the loop gain. 
     
     
         13 . The position control device according to  claim 11 , wherein the control unit estimates the disturbance frequency according to the position error based on adaptive control, changes a constant of a controller according to the estimated disturbance frequency, computes a control value in which the disturbance frequency component is suppressed, using the changed controller, according to the position error, and multiplies the result by a loop gain, so as to compute a drive value of the actuator. 
     
     
         14 . The position control device according to  claim 11 , wherein the control unit estimates the disturbance frequency according to the position error based on adaptive control, changes a constant of a controller constructed with an observer according to the estimated disturbance frequency, computes a control value in which the disturbance frequency component is suppressed according to the position error, using the changed observer, and multiplies the result by a loop gain, so as to compute a drive value of the actuator. 
     
     
         15 . A medium storage device, comprising:
 a head for at least reading data on a storage medium;   an actuator for positioning the head to a predetermined position on the storage medium;   a control section for computing a position error based on a target position of the head and a current position acquired from the head, computing a control value in which a disturbance frequency component is suppressed, using a predetermined feedback loop based on the position error, and multiplying the result by a loop gain, so as to compute a drive value of the actuator; and   a table for storing a target loop gain according to the disturbance frequency,   wherein the control section fetches the target loop gain according to the disturbance frequency from the table, adds a disturbance of a measurement frequency to the feedback loop, measures loop gain of the feedback loop, and calibrates the loop gain in the control value computing step based on the measured loop gain and the target loop gain.   
     
     
         16 . The medium storage device according to  claim 15 , wherein the control section fetches a measurement frequency according to the disturbance frequency from the table, adds a disturbance of the fetched measurement frequency to the feedback loop, and measures a loop gain of the feedback loop. 
     
     
         17 . The medium storage device according to  claim 15 , wherein the control section fetches a measurement frequency which does not overlap with the disturbance frequency from the table. 
     
     
         18 . The medium storage device according to  claim 15 , wherein the control section estimates the disturbance frequency according to the position error based on adaptive control, computes a control value in which the disturbance frequency component is suppressed, according to the estimated disturbance frequency, and multiplies the control value by a loop gain, so as to compute a drive value of the actuator. 
     
     
         19 . The medium storage device according to  claim 18 , wherein the control section interrupts the estimation of the disturbance frequency according to the position error during calibration of the loop gain. 
     
     
         20 . The medium storage device according to  claim 18 , wherein the control section estimates the disturbance frequency according to the position error based on adaptive control, changes a constant of a controller according to the estimated disturbance frequency, computes a control value in which the disturbance frequency component is suppressed, using the changed controller, according to the position error, and multiplies the result by a loop gain, so as to compute a drive value of the actuator. 
     
     
         21 . The medium storage device according to  claim 18 , wherein the control section estimates the disturbance frequency according to the position error based on adaptive control, changes a constant of a controller constructed with an observer according to the estimated disturbance frequency, computes a control value in which the disturbance frequency component is suppressed, according to the position error, using the changed observer, and multiplies the result by a loop gain, so as to compute a drive value of the actuator.