A Design of H∞ Controller for Minimizing Position Error Signal in HGA Tester

Abstract

Abstract

In hard disk drive industry, head gimbal assemblies (HGAs) may be individually tested prior to their installation in a disk

drive. While performing a test by a HGA tester, false negative result may result because of external air turbulence caused by

the rotation of the test disk, which may lead to oscillation of the HGA, causing it to move out of track; this error is called

PES (Position Error Signal). The objective of this study is to find a model of a servo system in HGA testing system by

using Transfer Function Determination Code (TFDC) algorithm with Particle Swarm Optimization (PSO) algorithm. TFDC

technique is proposed to model the system in frequency domain and PSO is used to adjust the weights in the TFDC

algorithm at each frequency. Several kinds of inertia weights for PSO are compared to get the different models. After

getting the model, controllers are designed to get rid of the effect of disturbance by using PID Control and H∞ Control.

Keywords : Head Gimbal Assembly; HGA Tester; Position Error Signal; Servo System