Junichi Ichihara

Precise track-following control using a MEMS tracking mirror in high-density optical disk drives

Developed a dual-stage tracking mechanism using a MEMS tracking mirror and used /spl mu/-analysis and synthesis to design a controller satisfying multiple desired specifications. The efficiency of the proposed method was demonstrated by an experiment having tracking errors of less than 10 nm. We expect the MEMS tracking mirror to contribute to the creation of high-density optical disk drives.

Development of Actuators for Small-Size Magneto-Optical Disk Drives

This paper describes the development of focusing and tracking actuators for compact low profile magneto-optical disk drives. We clarify a structural optimization mechanism that raises the upper mechanical resonant frequencies of the actuators to 30 kHz. Optimized drive motors reduce power consumption.

Robust controller design for single-stage track-following system in magneto-optical disk drives

We designed robust controllers for track-following systems in magneto-optical (MO) disk drives, and compared them with a conventional controller. We estimated achievable tracking accuracies of single-stage systems while changing the three dominant parameters that restrict control performance.

Computer Mechanics. Positioning Control of an Actuator with Two Degrees of Freedom.

Precise and accurate positioning is required by high-density disk storage devices, such as magnetic disk drives and optical disk drives. Nonlinear friction in a guide system reduces positioning accuracy. In this paper, we introduced a swing arm rotary actuator with two degrees of freedom which overcomes the problem of nonlinear friction and improves positioning accuracy. The moving part of the rotary actuator has two members. The first member runs on ball bearings around the fixed shaft, and the second is suspended from the first by a leaf spring. Driving torque is applied to the second member. Small displacements are achieved by bending the leaf spring, and large displacements are realized by rotation around the ball bearings. We analyzed our actuator theoretically and found that its positioning is stable with a suitable lead lag compensator. We conducted a numerical analysis of the control system, including the influence of nonlinear friction, using the Runge-Kutta-Gill method. The positioning accuracy of our system is clearly higher than that of a conventional rotary actuator positioning system. We also present the performance of an actual actuator. We obtained an error suppression ratio of better than -60dB for a sinusoidal input of 1 μm at 60Hz.