Recently, optical disk drives are demanded to a fast data processing with a small size. It is necessary that the performance of actuator and controller be improved for the fast reading or writing. Especially, controllers play an important role in reading the signal on tracks of an optical disk and getting over the limitation of the actuator. Controllers of the tracking direction can be separated into a track following controller and a track seek controller. And, the time consumption for the track seek is one of the essential index of the performance of an optical disk system. There are many techniques for the control of the velocity or acceleration in a fine tracking actuator and a coarse actuator in order to reduce the track seek time.
First of all, the residual vibration of the fine actuator which is entrained on a coarse actuator is a fatal problem of the track seek and the track pull-in. In this paper, previous methods for reducing seek time were accomplished. But the perfect vibration reduction of the fine actuator has some limitations under the non-zero track eccentricity. Generally, the track eccentricity has the constant amplitude and the fixed frequency when the spindle motor rotates with CAV (Constant Angular Velocity).
If the fine actuator has the same velocity with the track eccentricity when the coarse actuator stops, there would be no latency time for the track pull-in. Both a sinusoidal excitation and a pulsed excitation are proposed for the velocity generation of the fine actuator. And merits and demerits of two excitation methods are investigated by the simulation, experimental result and error analysis. Excitation of the fine actuator by the pulsed input has good performance in comparison with the sinusoidal excitation.
