Compact three-degree-of-freedom planar actuator with two sets of three-phase currents capable of driving over large displacements in yaw direction

We present a three-degree-of-freedom planar actuator that can position a mover over a wide range of locations in the yaw and translational directions. In conventional planar actuators, which have multiple pairs of permanent magnets and armature coils, the mover cannot be displaced by large amounts unless the planar actuator has numerous armature coils. Furthermore, the movable area of conventional planar actuators in the yaw direction is quite narrow because of the interference between the different pairs of permanent magnets and armature currents that occurs due to the yaw displacements. The proposed planar actuator has only six stationary armature conductors for two sets of three-phase currents. The mover constantly faces all the armature conductors, and hence, it can be subjected to driving forces for three-degree-of-freedom movement anywhere on a plane parallel to the stator surface. Therefore, the movable area of the actuator can be easily expanded by increasing the length of the armature conductors. However, the driving forces depend on the yaw angle, and large yaw displacements impede the generation of sufficiently strong driving forces. In this paper, we present the results of experiments conducted to determine the movable area of our proposed planar actuator in the yaw direction. The experimental results indicate that sufficient torques in the yaw direction can be generated when the yaw displacement is less than 26 deg. The driving force acting on the mover is a function of the yaw angle and is periodic with a 90-deg period due to the central symmetry of the actuator. The experimental results also indicate that the mover can travel over 90-deg displacements in the yaw direction. Thus, we successfully demonstrate the three-degree-of-freedom large movement of the planar actuator by controlling two sets of three-phase currents. © 2009 The Institute of Electrical Engineers of Japan.