Point-to-point control of a high accuracy positioning mechanism

This paper compares three open-loop command generating methods for the point-to-point control of a wafer stage. Whereas the theoretical time-optimal bang bang force command results in excessive residual vibration due to excitation of resonant modes, shaped force profiles have the property not to excite these modes while still allowing for fast movements. The most successful shaping method turned out to be the one which was best able to handle uncertainty in our knowledge of the resonant mode dynamics, and the way this knowledge is used to shape the spectral content of the force command. Besides comparing three shaping methods, it was also investigated how the feedback and feedforward compensator affect the point-to-point motion.