Abstract: A system, modules, means, and computer readable media for and a method of compensating disturbances that cause track shape irregularities on a disc in a disc drive during a disc servo-writing process performed by a servo-writer are disclosed. The disturbances substantially attributable to a nonrepeatable runout (NRRO) are present during the servo-writing process. A substantial component of the NRRO is a cage frequency generated by a spindle motor mechanism in the disc drive. A reference cage frequency is determined during a servo-writing process by using a position sensor. Then a feed-forward input signal is determined based at least on the reference cage frequency during the servo-writing process. In addition, the feed-forward input signal is feed-forwardly transmitted to the servo-writer.

Abstract: A method of implementing an automatic acoustic management feature for a disc drive includes receiving an acoustic/performance compromising factor from a host, tuning disc drive performance by applying the factor to a control parameter to generate a modified control parameter, and executing a loop for controlling a disc drive operation using the modified control parameter. In another embodiment, a disc drive has a base, a rotatable disc, an actuator assembly with an arm for carrying a head in transducing relation to the disc in response to a control signal, a receiver for receiving an acoustic/performance compromising factor, and a controller that monitors the position of the arm and generates the control signal. The controller executes a seeking control loop having a control parameter modified by applying a compromising factor to the parameter to tune the acoustic performance of the drive.

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: A method of characterizing and screening a disc drive based on a voice coil motor pivot friction developed during a low velocity seek operation consists of determining estimated drive level bias values required by the voice coil motor to move an actuator arm assembly during a fast seek, then determining a low velocity drive level bias values required by the voice coil motor to move an actuator arm assembly during a slow seek, then computing a difference between the estimate drive level bias values and the low velocity drive level bias values, then determining a hit counter value based on comparing the computed difference with a predetermined threshold value, and then characterizing the disc drive based on the hit counter value.

Abstract: A repetitive learning compensator for a servo system of a disc drive includes a memory buffer having a length N/m where N is the number of servo sectors in a track, m is a parsing factor greater than 1 and N/m is an integer. A down sampler supplies servo signals containing error signals to the repetitive learning compensator at a frequency of fs/m, where fs is a sampling frequency based on N and a fundamental frequency f0 of the spindle motor. An up sampler supplies filtered signals from the repetitive learning compensator to the actuator assembly at the sampling frequency fs. One aspect of the disclosure includes tuning the repetitive learning compensator with a phase advance represented by NPA and a cutoff frequency fc, where NPA and fc are selected as a pair to provide the greatest transfer function amplitude at the harmonic frequencies for the repetitive learning compensator.

Abstract: A disc drive device 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 an actuator arm and a transducer head in a transducing relationship with respect to the disc. The transducer is attached to the actuator arm. A method of screening disc drives for harmonic resonant frequencies includes sampling the position error signal at a track location in the disc drive, and determining the velocity of the position error signal from the sample of the position error signal. The velocity of the position error signal sample is divided by the position error signal to produce a quotient. The quotient is compared to a selected quotient threshold value to determine the type of a harmonic in the disc drive.

Abstract: A low cost sensorless technique for attenuating an actuating force experienced by the actuator arm assembly due to an external vibration and shock during a track following operation includes, in one example embodiment, measuring an applied signal and a position error signal during the track following operation within a sampling time. Then, the method includes the step of computing an acceleration signal from the measured position error signal. Further, the method includes comparing the acceleration signal with the applied signal to obtain a correction signal. Then, the force experienced by the actuator arm due to the external vibration and shock is attenuated by filtering the correction signal using one or more low-pass frequency filters.

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 an actuator arm and a transducer head in a transducing relationship with respect to the disc. The transducer is attached to the actuator arm. A method for screening disc drives for resonant frequencies associated with the actuator arm includes the steps of following a track within the disc drive, and selectively boosting the servo control signal. The method further includes a step of monitoring a position error signal from a transducer attached to an actuator arm of a disc drive. The position error signal is monitored by filtering the position error signal using a bandpass filter. Boosting the servo control loop includes tuning the magnitude of the booster signal gain.