SPECIFIED ORDER - H-infinity LOOP SHAPING CONTROL FOR HARD DISK DRIVE SERVO USING PSO

The demand of data storage density has been increasing continuously, but the data access time and track pitch need to be decreased. The high precision servo control system is required to achieve the predicted goal that will be crossing 10 TB/in(2) areal density before 2020. Due to the fact that the precision of read/write head is sensitive to disturbance and noise, it is the challenging problem for the practical control. To overcome this problem, this paper proposes a new servo controller designed, specified order H-infinity, loop shaping (SOHLS) which adapts the particle swarm optimization (PSO) for searching the optimal controller parameters. The proposed technique can solve the problem of high order that was caused from the conventional H-infinity, loop shaping (HLS), in addition, it can guarantee the robustness of the servo system. Based on simulation results, the performances of the proposed SOHLS approach are investigated in comparison with that of the conventional H-infinity, robust loop shaping, fixed-structure H-infinity, control based on non smooth algorithm including reduced order controller by Hangkel norm model reduction technique. The proper repeatable runout (RRO) and non-repeatable runout (NRRO) were applied to the system to verify the robustness of all designed controllers. The results demonstrate the advantages of the proposed SOHLS which gains better performance and more robustness than the other conventional controllers.