Fast seek control for flexible disk drive systems with back EMF and inductance

This paper derives shaped time-optimal servomechanism (STOS) controllers for flexible disk drive systems considering the effect of back electromotive force (back EMF) and coil inductance. To eliminate the vibration due to an unwanted flexible mode, input shaping is used to alter the time-optimal velocity phase-plane profile that moves the third-order non-flexible dynamics from rest to rest. Because the closed-form solution for the time-optimal control of the third-order non-flexible dynamics is not known, the shaped time-optimal velocity phase-plane profiles are derived numerically. By using a curve-fit polynomial to approximate these shaped time-optimal velocity phase-plane profiles, we obtain an analytical expression for the STOS control. Simulations show that the curve-fit polynomials give high accuracy and the STOS control yields near time-optimal performance without unwanted residual vibration.