Design and Control of a Compact Lightweight Planar Positioner Moving Over a Concentrated-Field Magnet Matrix

In this paper, a single-moving-part planar positioner with six coils is designed and implemented. A concentrated-field permanent-magnet matrix is employed as the stationary part. The moving platen has a compact size (185.4 mm × 157.9 mm), light mass (0.64 kg) and low-center-of-gravity. The moving platen carries three planar-motor armatures with two phases per motor. Force calculation is based on the Lorentz force law and conducted by volume integration. In order to deal with the nonlinearity due to trigonometric dependencies in the force-current relation, modified proportional-integral-derivative (PID) and lead-and-PI compensators are designed with computed currents to close the control loop and obtain the desired performances. Experimental results verified the commutation law and the force calculation. The new design with only six coils allows for simplification of the control algorithm and reduced power consumption of the positioner. The maximum travel ranges in x, y, and the rotation about the vertical axis are 15.24 cm, 20.32 cm, and 12.03°, respectively. The positioning resolution in x and y is 8 μm with the rms position noise of 6 μm. The positioning resolution in rotations about the vertical axis is 100 μrad.