Abstract: A head position control system controls the position of the head by correcting the components synchronizing rotation of the disk from the head control amount, in which an adjusted gain to minimize the components synchronizing rotation after correction is theoretically acquired. An adjusted gain based on the ratio of the magnitude between the components synchronizing rotation of a disk and the components not synchronizing rotation of the disk in the position signals is used. And a gain to minimize RRO after correction can be theoretically determined using an expression to determine RRO after correction. The gain can be determined without depending on experiment, and the value of RRO after correction can be guaranteed, therefore the manufacturing time and the device specifications can be determined.

Abstract: In a seek control device based on a current observer control which performs two degree of freedom control, a current step difference to be generated when seek control is switched to following control is prevented. When seek control is switched to following control, a current step difference cancellation trajectory generation section calculates a current value Udiff for the amount of the step difference based on a difference between current values u(n) and u(n?1), and supplies a target position trajectory r?(n) (or target current trajectory) for offsetting this calculated value to a following controller. Therefore the current step difference of the output current is cancelled.

Abstract: In a position control device based on a current observer control for performing two degree of freedom control, calculation accuracy is improved using a fixed point processor. For a target position trajectory and position error, which are inputs of a two degree of freedom control system using an observer, relative values of which reference is the reference trajectory are used, so that the state variable of the observer can hold a relative distance from the reference position. Compared with the case of holding an absolute distance, a range where the value changes is smaller, and the number of effective digits of a decimal point can be increased, and calculation accuracy can be improved even if a fixed point method is used. As a consequence, control current becomes smooth and the generation of resonance and noise can be prevented in an acceleration period, and the generation of residual vibration can be prevented in a constant velocity period and deceleration period, and seek time can be decreased.

Abstract: A storage device has a separate type magnetic head and a discrete type magnetic recording medium on which recording tracks and recording disabled areas are alternately formed. An accurate offset of the magnetic head with respect to the magnetic recording medium is measured even if the widths of the elements of the separate type head differ. While changing the write position and read position of a magnetic recording head, a write element writes measurement data to a magnetic recording medium, a read element reads the written measurement data, and the signal quality is measured and the write offset value and the read offset value are calculated from the inflexion points of a contour line on the two-dimensional map on the measured signal quality. Even if the widths of the write element and the read element differ depending on the individual magnetic recording head, an offset with respect to the separated recording tracks can be accurately measured.

Abstract: In a position control device based on a current observer control for performing two degree of freedom control, deterioration of the position accuracy caused by the output delay due to computation is prevented. In the two degree of freedom control system for preventing overrun, the delay of output of the two degree of freedom control (computing delay and hardware delay of drive amplifier, D/A converter, etc.) is considered, and the estimated state of Td which is advanced by the amount of delay from the sample point of time is computed, then output is computed based on this estimated state. So even if state changes during calculation from the sample point of time, the influence of the output delay can be prevented, and highly accurate position control can be performed, therefore overrun can be prevented.

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.

Abstract: A magnetic disk device includes a position and velocity demodulating circuit. In the position and velocity demodulating circuit, a difference calculating unit demodulates a moving velocity of a magnetic head based on a phase difference in servo signals as servo data in the same sector. An overflow detecting unit detects an overflow of the demodulated moving velocity and calculates a correction value for the overflow. The overflow is corrected based on the correction value. The corrected overflow is further corrected by a correction value of a repeatable velocity error for the demodulated velocity to output an accurate demodulated velocity.

Abstract: A control device demodulates servo information read from a storage medium of a storage device via a head. A velocity demodulating unit demodulates a moving velocity of the head based on the servo information. A velocity correcting unit corrects the moving velocity, when an amount of change in demodulated moving velocity exceeds a predetermined threshold.

Abstract: In a positioning control device based on control of an observer having a disturbance suppression function, a disturbance suppression function according to a head position is added without impairing the control characteristics of the observer. The position control device has an observer having a disturbance suppression function comprising a model of an actuator and a model of disturbance, and a table for storing an estimated gain of the observer according to a position of the head. And an estimated gain is acquired from the table according to the position of the head, and an estimated gain of the observer is changed so as to change the disturbance suppression frequency characteristic. The disturbance suppression characteristic can be optimized according to the position of the head in the radius direction or between disks, and vibration of the head can be prevented even if recording density is increased.

Abstract: In a head position control device having a disturbance suppression function and eccentricity correction function, the interference between the eccentricity correction function and the disturbance suppression function is prevented. An eccentricity correction function and disturbance suppression control function are provided in the head positioning control system, and an interference prevention function, which detects the disturbance suppression frequency and turns OFF the feedback of the eccentricity correction control for the eccentricity correction frequency near the disturbance suppression frequency, or shifts the disturbance suppression frequency from the eccentricity correction frequency, is provided. Therefore the interference between the eccentricity correction and the disturbance suppression can be prevented, and unstable eccentricity correction can be prevented.

Abstract: In a settling judgment method for judging whether an object is settled at a target position, a margin for settling judgment is expanded, and settling is judged accurately. As the settling judgment formula of the settling judgment block, both the position error and the added value of the position errors of a plurality of samples are used. Particularly for the vibration in the low frequency area, the margin for settling judgment increases. Therefore even if vibration exists in the low frequency area, judging as deviation from the settling judgment conditions by mistake can be decreased, and operations (e.g. read/write operation) can be continued.

Abstract: A positioning control device based on an observer control has a disturbance suppression function to which a disturbance suppression function is added without affecting the control characteristics of the observer. Models of an actuator and a disturbance model are separated, and for the disturbance model, state information is generated using an estimated gain determined from a disturbance model defined by a transfer function of which denominator is a numerator of a filter in which degrees of denominator and numerator for shaping a sensitivity function are the same, and the disturbance suppression value of the actuator is computed from the state information. The vibration of the head can be prevented adapting to a wide range of disturbance frequencies without affecting the control characteristics of the observer.

Abstract: A seek control device controls the seek of a plant to prevent the position shift due to an error between a model for generating seek current and a model of the plant. When the seek trajectory is provided by seek trajectory generation for controlling the seek of a plant, the frequency characteristic of a feed back loop is changed according to the seek time and the gain of the position shift component due to the shift of the actual plant and the model of the plant is increased, so as to suppress the position shift by the feed back loop. Dispersion of the seek time can be decreased, and an overrun or underrun can be prevented.

Abstract: A positioning control device executes disturbance observer control having a disturbance suppression function, wherein changes of control characteristics are prevented even if the disturbance frequency is suppressed. When a control value of an actuator is computed using estimated gains of the actuator and estimated gains of disturbance according to an estimated position error by disturbance observer control including a model of the actuator and model of the disturbance, the disturbance frequency is estimated according to the estimated position error, and the estimated gains of the actuator and the estimated gains of the disturbance, corresponding to the disturbance frequency, are changed. Therefore appropriate observer control according to the disturbance frequency can be implemented.

Abstract: A disk device has a positioning control system which has a disturbance suppression function in which the disturbance is suppressed quickly to prevent vibration of the head. In a positioning system having a disturbance suppression function of a disk device, an interface circuit for setting a known disturbance frequency to an initial value from the outside is installed. An unknown disturbance frequency can be immediately suppressed, or disturbance frequency control can be started from a known disturbance frequency, and even if the frequency changes thereafter, the estimated frequency can follow up to the disturbance, and the vibration of the head can be quickly prevented.

Abstract: A storage device has a separate type magnetic head and a discrete type magnetic recording medium on which recording tracks and recording disabled areas are alternately formed. An accurate offset of the magnetic head with respect to the magnetic recording medium is measured even if the widths of the elements of the separate type head differ. While changing the write position and read position of a magnetic recording head, a write element writes measurement data to a magnetic recording medium, a read element reads the written measurement data, and the signal quality is measured and the write offset value and the read offset value are calculated from the inflexion points of a contour line on the two-dimensional map on the measured signal quality. Even if the widths of the write element and the read element differ depending on the individual magnetic recording head, an offset with respect to the separated recording tracks can be accurately measured.

Abstract: In a settling judgment method for judging whether an object is settled in a target position, the settlement is judged accurately at high-speed. In a positioning device for controlling a position of an object using a position error between a target position and a current position, a plurality of judgment blocks, each of which has a different judgment slice value and continuous sample count, are created in a settling judgment block for judging whether the object is settled within the positioning accuracy range of the target position, the judgment value of the position error computed by the judgment formula is judged in each judgment block each having a different judgment slice value and continuous sample count respectively, and OR of the judgment results is output. According to the settling judgment formula, settling can be judged accurately at high-speed, and both improvement of positioning accuracy and high-speed judgment can be implemented.

Abstract: A settling judgment method judges whether an object is settled at a target position by using a settlement judgment formula set a slice value and number of continuous samples. The slice and number of continuous judgments of the judgment value of the settling judgment are judged by the slice value and number of samples which are set such that the maximum value of a maximum amplitude ratio (Rate), for each frequency of cyclic disturbance (Y), determined from the maximum amplitude values (Max1, Max2) of the judgment values when the cyclic disturbance is applied is contained within a predetermined position accuracy. Settlings can be judged at high-speed and accurately according to the settling judgment formula, and both an improvement of positioning accuracy and high-speed judgment can be implemented.

Abstract: The present invention provides a positioning control device and a disk device for shortening a calculation delay time. Upon detection of a position signal from a demodulation circuit, an MCU of the disk device calculates a position error, and following calculation of a control amount, executes determination and correction processing. A variable value prior to the start of calculation is stored in a save area of a memory (or a save memory) such that when the variable value is to be reset as a result of the determination and correction processing, the variable value is read from the save area, the reset variable value is stored in an overwrite area of the memory (or an overwrite memory), and calculation of the control amount is re-executed.

Abstract: A storing unit stores first correction information for correcting a distortion synchronized with a rotation frequency of servo information of a first disk. A control unit controls positioning of a head on a target track by correcting the servo information of the first disk with the first correction information. Measurement information used for measuring the first correction information is calculated based on second correction information for the servo information in other disk apparatus including a second disk on which the servo information is formed using a common master medium with the first disk.