Design of swing arm type actuators considering thermal and dynamic characteristics

Abstract

The present state of the design of swing arm actuators for optical disc drives is to obtain the highly efficient dynamic characteristics within a very compact volume. As a necessary consequence, the need of the small form factor (SFF) storage device has arisen as a major interest in the information storage technology. Due to the size constraint, the thermal stability of the optical pick-up head is important: therefore, the actuator is designed to emit the heat, which is generated by the optical pick-up, along the structural body easily. In this paper, we suggest the miniaturized swing arm type actuator that has effective heat emission quality as well as satisfies the dynamic requirements for the SFF optical disk drive (ODD). The actuator is targeted to be installed in CF-II card size drive to be competitive with flash memory or mini hard disk drive used in mobile electric devices; therefore the dimension of the actuator is required as 11.0 mm · 2.5 mm · 25.0 mm (width · height · length). Because of its small size, the dynamic requirements are severe to ensure the enough gain-margin for the system control together with satisfying the DC/AC sensitivity conditions. Moreover, due to the small size, the maximum pick-up temperature is critical in design because the system has high possibility to reach the shut-down temperature. For the operating mechanism, it uses a tracking electromagnetic (EM) circuit for the focusing motion together and the initial model is designed and promoted by the design of experiments (DOE) only considering the dynamic characteristics. New concept design is suggested based on the topology optimization method considering the thermal conductivity. Furthermore, the new design is modified by DOE to maintain the high sensitivity and to have wide control bandwidth and decreasing mass and inertia. The final design of a swing arm type actuator for SFF ODD is suggested and its dynamic characteristics are verified.

Topology optimization of flextensional piezoelectric actuators with active control law

“…One classical example is the controlled miniaturized swing arm type actuator installed in optical disk drives for mobile electrical devices. They require highly efficient dynamic characteristics and the optimization of performance under size constraint (KIM; KIM; HAN, 1999;YU;LIU, 2003;ZHU;WANG;JIANG, 2006;PARK et al, 2007;LEE, 2007;SUN et al, 2009;SONG;KIM, 2012). The suspension assembly in the head disk interface must provide high reliability as a slider following capability for disk run-out, and it must also allow for good servo control during track seeking, settling and following (YU;LIU, 2003).…”

Design of the rotary VCM actuator for small form factor optical disk drive

“…The heat generated from the integrated optical pickup is varied by temperature and optical output power (Lee et al 2006a, b). And Park and Yoo (2006) analyzed and verified that the heat generated from the integrated optical pickup is 231 mW which is used in this paper. The vibration of the optical disk has to be measured in order to obtain the heat generated from voice coils, because the heat depends on the input electrical power that is related to the vibration of optical disk.…”

“…The heat can cause many problems; especially, the laser diode in the integrated optical pickup can be damaged easily because it generates large heat and has low thermal endurance. Park and Yoo (2006) designed an actuator considering thermal and dynamic characteristics. Natural convection of the pickup is improved by cooling pad and the amount of conducted heat is increased by modifying the structure.…”

Design of moving magnet type pickup actuator using inserted coil

“…To check the thermal stability, thermal analysis is performed. The material of yoke is zinc and the convection coefficient is settled at 10 W/m 2 K (Kim et al 2004b(Kim et al , 2005Park et al 2006). The bottom area of yoke has 323 K because we assumed that the temperature of pickup base is about 318 K. And the room temperature is 298 K. Heat generated in coils was calculated by resistance and current of coils.…”