Circuit model for piezoelectric actuator with electrically conductive epoxy

Dual stage actuator (DSA) has been a critical component in hard disk drives to increase servo control bandwidth and thus storage capacity. The electrical properties of a typical DSA vary with the frequency, as piezoelectric materials (e.g., PZT) and electrically conductive adhesives (ECA) are commonly used. A circuit model is thus needed to capture such complexity for servo control design. In this paper, we review two typical DSA circuit designs and compare three circuit models with different simplifications. The model with parallel RC circuits can successfully capture DSA circuit characteristics up to 1 MHz. Impedance data measured from real parts show excellent agreement with simulation results based on the model. In addition, we investigate impacts of abnormal ECA on the overall DSA transfer function. This research can provide a practical yet valuable guideline for DSA related servo control.