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This paper deals with a new tracking control method for piezoelectric actuators. When actuating in an open-loop manner, in order to compensate for the creep effect of the piezoelectric transducer as well as hysteresis, a new concept of `voltage creep' is proposed, which is represented by the two parameters V0 and γv. It is shown that these two parameters have the properties of wiping out and congruency, which make it possible to derive parameter values appropriate to control piezoelectric actuators using the Preisach model. Finally, a tracking control experiment of piezoelectric actuators for an arbitrary desired trajectory is performed giving greatly improved results compared to other open-loop actuating methods.

In a small-form-factor (SFF) optical disk drive (ODD), the optical flying head (OFH) on a thin-cover-layered plastic disk requires not only uniformity of the cover layer thickness of the disk media, but also the flying stability of OFH on the plastic disk surface with low flying height variation, as well as precise tolerance management in the OFH assembly. Therefore, in order to develop a practical optical pickup head interfaced to the plastic disk, we designed the OFH with a parallel-plate electrostatic actuator for the vertical positioning of the objective lens for better flying characteristics. The flying height of the OFH is designed to be 200 nm to increase air-bearing stiffness. On the other hand, a UV resin cover layer is adopted as a protective layer and a hard and stiff plastic substrate is also adopted to increase the durability of the disk. In the evaluation of the stability of the OFH and the durability of the disk, we introduce computational and experimental results on the flying height variation of the OFH, additionally we investigated the characteristics of the durability of various plastic disks.