Reliability Evaluation of Piezoelectric Micro-Actuators With Application in Hard Disk Drives

Piezoelectric micro-actuators have been extensively studied and used in hard disk drive head positioning systems. In these cases, piezoelectric micro-actuators/sensors experience high frequency cyclic loading during their operations. The fatigue failure and the lifespan of such micro-actuators become a concern of researchers and engineers. However, the probability and statistics based reliability theory has not been well developed for piezoelectric micro actuators. In this paper, a probabilistic approach is presented to evaluate the reliability of piezoelectric micro-actuators. Based on the relationship between the lifetime degradation mechanism of piezoelectric actuators and the electric field strength, an interference model of electric load and strength is introduced for the reliability study of piezoelectric micro-actuators. Furthermore the reliability model is expanded into a 2-D case to take into account the effects of both driving voltage and temperature. A 2-D interference model incorporating the 2-D strength and load is proposed to obtain the relationship among the reliability, usage cycles, driving voltage and temperature. A case study of a piezoelectric micro-actuator used in a disk drive head positioning system demonstrates the application of the proposed approach.