Prediction of position error signal of a hard disk drive undergoing a long seek

Current methods used for the measurement of stiffness and damping of spindle motor bearings used in hard disk drives use a vibration base driven by an external actuator. Acceleration sensors and displacement sensors installed onto the vibration base are then used to measure the acceleration and the spindle runout, respectively. Outputs from these sensors are analysed and used for the calculation of the stiffness and damping. The method, used for direct measurement and monitoring of total stiffness and damping, and proposed in this article does not require the use of any additional external sensors, neither does it require a vibration base driven by an external actuator. Vibration is generated by introducing a known value of imbalance onto the spindle motor. The vibration generated is then measured by reading and analysing the position error signal written on the disk surface and subsequently, used to calculate the total stiffness and damping. Experimental results verifying the proposed method are presented.

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An Adaptive Feedforward Control Approach for Rejecting Disturbances Acting on Uncertain Linear Systems

Volume 2: Mechatronics; Mechatronics and Controls in Advanced Manufacturing; Modeling and Control of Automotive Systems and Combustion Engines; Modeling and Validation; Motion and Vibration Control Applications; Multi-Agent and Networked Systems; Path Planning and Motion Control; Robot Manipulators; Sensors and Actuators; Tracking Control Systems; Uncertain Systems and Robustness; Unmanned, Ground and Surface Robotics; Vehicle Dynamic Controls; Vehicle Dynamics and Traffic Control ◽

10.1115/dscc2016-9832 ◽

2016 ◽

Cited By ~ 1

Author(s):

Behrooz Shahsavari ◽

Jinwen Pan ◽

Roberto Horowitz

Keyword(s):

Standard Deviation ◽

Linear Systems ◽

Control Method ◽

Feedforward Control ◽

Disk Drive ◽

Position Error ◽

Error Signal ◽

Position Error Signal ◽

Uncertain Dynamics ◽

Adaptive Feedforward

This paper proposes a novel adaptive feedforward control method for rejecting unknown disturbances acting on linear systems with uncertain dynamics. The proposed algorithm does not require a model of the plant dynamics and does not use batches of measurements in the adaptation process. Moreover, it is applicable to both minimum and non-minimum phase plants. The algorithm is a “direct” adaptive method, in the sense that the identification of system parameters and the control design are performed simultaneously. In order to verify the effectiveness of the proposed method, an adaptive feedforward controller is designed as an add-on compensator to the existing baseline controller of a hard disk drive. An accelerometer mounted on the disk drive casing provides the input signal for the controller. The control objective is to minimize the standard deviation of the position error signal in the presence of external random vibrations. Simulation results show that reduction of 46% in the standard deviation of the position error signal can be obtained.

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