A New Type of Direct-Drive Variable-Reluctance Actuators

Most advanced manufacturing processes require highspeed and high precision motion control for material transfer, packaging, assembly, and electrical wiring. Examples are surface mounting of electronic components, wire bonding of semiconductor chips, and assembly of watches and hard disks. To achieve precise motion control, most of these high-performance manufacturing machines use rotary d.c. or a.c. motors as the prime motion actuator, and couple their output shafts to mechanical motion translators (e.g. reduction gear, belt, ball screw, etc.). Though this is the most widely used method, it has disadvantages of reduced accuracy, complex mechanical structure, difficult adjustments and alignments, high production cost, and low reliability. In this paper, the author proposes a new direction in high performance machine design, and suggests that future high performance motion systems should be designed through "simplifying the mechanics through specialized directdrive actuators and advanced control methodologies". For this purpose, this paper investigates a class of variable reluctance (VR) direct-drive motion actuators for high performance machines. The paper looks into several specialized motion actuator systems designed by the author, (including limited stroke actuator, gripper, artificial limb, linear motion device, and planar motion device), highlights their features and advantages, and describes the challenges of controlling these devices.