Abstract: An apparatus and method for selecting physical cylinders (cylinders accessible for read/write operations) in a disc drive is provided. The disc drive includes at least one rotatable disc. The disc drive also includes a first head, which is positionable adjacent a first disc surface, and a second head, which is positionable adjacent a second disc surface. The first disc surface has a first plurality of greycode tracks and the second disc surface has a second plurality of greycode tracks. Each greycode track of the second plurality of greycode tracks corresponds to a different greycode track of the first plurality of greycode tracks, thereby forming a plurality of greycode cylinders, with each greycode cylinder of the plurality of greycode cylinders including a pair of corresponding greycode tracks. The physical cylinders are a subset (less than all) of the plurality of the greycode cylinders.

Abstract: A method of handling resonance effects on disc drives includes the steps of monitoring a position error signal (PES) for an actuator arm of a disc drive, generating a feedforward compensation signal from the PES using a bandpass filter, and applying the compensation signal to a servo control signal. The bandpass filter has a center frequency set to a known resonance frequency. A disc drive includes an actuator assembly including an arm for carrying a head in a transducing relation with respect to a disc in response to a control signal, and a controller that monitors a PES for the arm and generates the control signal. The controller includes a servo controller that generates a servo control signal from the PES, and a feedforward compensation element which bandpass filters the PES to generate a compensation signal which is combined with the servo control signal to generate the control signal.

Abstract: An information handling system, such as a disc drive, includes a base, a disc stack rotatably attached to the base, and an actuator assembly movably attached to the base. A region of the disc stack is identified as a parking band, and when power is not provided to the disc drive, the actuator assembly is held in a parked position within the parking band by an actuator latch. The actuator latch and actuator assembly have different resonant frequencies based on several environmental elements near the actuator assembly, including the temperature of the environment in the disc enclosure. The actuator assembly is unlatched by measuring the environmental element near the actuator assembly and applying an alternating current to a voice coil coupled to the actuator. The frequency of the alternating current applied to the actuator assembly during the unlatching procedure is near the resonant frequency of the actuator assembly in the measured environment.

Abstract: A method for writing servo information to a disc rotatably mounted to a spindle motor. A measured cage frequency is obtained from a written reference track, from which an actual cage frequency is predicted. The predicted cage frequency is then used to derive compensated position commands. During a servo write interval, the compensated position commands are used to control the head such that the head follows the disc movements caused by the cage frequency.

Abstract: A method of producing a modified control signal to an actuator arm assembly of a disc drive to reduce RRO includes the step of generating a correction signal corresponding to a position error signal of a current track. Then to determine a high pass filter transfer function of a high pass filter to decrease a gain of an unwanted frequency generated when increasing a learning gain of the correction signal to achieve a faster convergence without any loss of performance in the disc drive. Then to determine filter parameters from the high pass filter transfer function, and to filter the correction signal by passing the correction signal through the high pass filter to generate a modified control signal to the actuator arm assembly of the disc drive using the filtered correction signal to remove the RRO on a next track.

Abstract: A method for writing servo information to a disc rotatably mounted to a spindle motor. A measured cage frequency is obtained from a written reference track, from which an actual cage frequency is predicted. The predicted cage frequency is then used to derive compensatedposition commands. During a servo write interval, the compensated position commands are used to control the head such that the head follows the disc movements caused by the cage frequency.

Abstract: A disc drive system and method of screening an actuator resonance includes a servo controller providing a multi-servo zone architecture. The servo controller partitions the disc into a plurality of servo zones. Each of the servo zones has a corresponding servo gain. When an actuator resonance is detected in one of the servo zones, the servo controller reduces the corresponding servo gain of the detected servo zone such that a drive with very low resonance at a certain zone does not affect the servo bandwidth of the other good zones. Accordingly, a drive with very low resonance is prevented from being scrapped. Further, the screening technique allows a drive to have an adequate servo margin for its normal operation after going through a resonance detection test.

Abstract: A disc drive includes a base and a disc rotatably attached to the base. The disc drive also includes an actuator assembly rotatably attached to said base and a device for moving the actuator assembly. The actuator assembly includes a transducer head in a transducing relationship with respect to the disc. The disc drive includes a disc drive controller for controlling movement of the actuator during track follow and track seek operations. The disc drive controller monitors the actuator during seek operations. The disc drive controller further computes a maximum average settle time from the monitored settle times. The dis drive controller further compares the maximum average settle time to a predetermined threshold value, and issues a command signal to adjust seek profile parameters of the disc drive to eliminate resonance in the actuator arm during a seek operation.

Abstract: A servo writer writes servo information to at least one disc of a head disc assembly. The servo writer includes a clock head that writes a clock track to the at least one disc and generates a clock signal when the clock head reads the clock track on the at least one disc. A servo pattern generator writes servo patterns to the at least one disc in response to the clock signal generated by the clock head reading the clock track on the at least one disc. The servo track writer also includes a phase lock loop clock generator which synchronizes to the clock track and produces the clock signal for the servo pattern generator.

Abstract: A disc drive includes a base and a disc rotatably attached to the base. The disc drive also includes an actuator assembly rotatably attached to said base and a device for moving the actuator assembly. The disc drive includes servo circuitry and a controller for controlling movement of the actuator and head switches during track seek operations. The disc drive determines the average seek time for each head and also measures the amount of time for a head switch from the transducer head having the shortest average seek time to all the other transducing heads in the disc drive. When a seek is performed, the controller in the disc drive determines if the shortest average seek time plus the seek time from the transducing head to the transducing head on the surface containing the target track and sector is less than the average seek time of the head on the surface having the target track and sector.