Analysis And Comparison Of Flexure Structures Used In 3-D Electrostatic Microactuators For Hard Disk Drives

To fulfill high-bandwidth and high-accuracy positioning requirements of hard disk drives (HDD), a novel slider-driven 3-dimensional electrostatic microactuator using dual-stage servo system was proposed in this paper. The microactuator is assembled between the suspension and the slider as the secondary actuator, and it is featured with the high aspect ratio 3-D silicon structure, high positioning bandwidth, low driving voltage and good reliability. The electrostatic microactuator has the parallel comb drives and mounting planes in the perpendicular planes, which greatly contributes to the large electrostatic force. The design and selection of the microflexures are crucial to the natural frequency and reliability of the microactuator. The flexure should have high stiffness effects and stiffness ratio. Four different flexure structures have been studied: straight-plate flexure, folded-plate flexure, curvy-plate flexure, and interlapped-L flexure. By analytical and numerical analysis, the interlapped-L flexure presents with higher stiffness effects and better actuation reliability, secondly is the straight-plate flexure. With ANSYS simulation, a servo bandwidth of over 2 kHz and a stroke of ±0.5 μm of the actuator can be obtained by utilizing interlapped-L flexure under a low driving voltage of 30V. It well satisfies the designed objective of the 3-D microactuators.