Online‐Offline Optimized Motion Profile for High‐Dynamic Positioning of Ultraprecision Dual Stage

Abstract

The wafer stage in dual-stage lithographic system is an air-bearing servo motion platform requiring high positioning accuracy and high transient performance. However, the residual vibration, resulting from almost zero damping, high velocity, parallel decoupling structure, and direct drive, brings about unacceptable overshoot and settling time. To suppress these unfavorable elements in high dynamic motion, a novel motion profile planning method combined with input shaping is proposed in this paper. Firstly, a trajectory named all free S-curve (AFS-curve) is derived, which has less constraints and better performance than traditional S-curve profile. Then, AFS-curve combined with a zero vibration shaper (ZV) is developed to further suppress residual vibration. Due to the very complex parameter adjustment, the online tuning may cause system oscillation that leads to damage of the precision stage. This paper, furthermore, proposes an online-offline method to optimize the parameters in the motion profile. Online step is performed to collect input and output data. Offline step includes the system model identification based on I/O data and parameter self-learning based on particle swarm optimization (PSO). The simulation and experimental results indicate that the proposed method achieves significant reduction of the positioning time and the overshoot in the dual-stage system.

Dynamic Modeling and Residual Vibration Suppression of the Redundantly-Actuated Cable Driving Parallel Manipulator

“…In order to verify the proposed algorithm, the fifth-order polynomial depicting the point-to-point motion as shown in (24) is used for the simulation, and parameters of one-to three-order IS will be optimized to suppress the residual vibration, and set the maximum iteration step K max = 300, the tolerance of the fitness function TolFun = 1 × 10 −6 , and the number of particles N p = 40 for the PSO. , we can see that without the IS, the maximum RV of cables are 0.037mm, and corresponding value is suppressed to 0.011mm when one-order IS is used, about 70% RV is eliminated.…”

“…Researchers adopted time-variant input shapers, which need additional sensors for online measurement of the frequencies. Some researches employed the PSO to offline optimize the variable of the IS and get good RV suppression performance [23], [24]. But they didn't consider the controller and only perform one-order optimization.…”