Robust time-optimal control of a linear motor positioning system

In this paper,a robust minimum-time control technique is presented for point-to-point motion of a linear positioning system with an ironless permanent magnet linear synchronous motor(ILPMLSM).For this system,a time-optimal control satisfying Pontryagin's minimum principle is in Bang-Bang fashion.A switching time computation algorithm using particle swarm optimization(PSO) is proposed to obtain bang-bang control law.Due to parameter variations and other disturbances,the obtained bang-bang control would result in undesirable chattering towards the end of the desired final state.To tackle this problem,a two-phase control scheme is developed in this work.In the first phase(gross motion control),a bang-bang control law is applied,while in the second phase(fine motion control) a fast terminal sliding mode control(FTSMC) technique is employed to guarantee the convergence of the state to the desired final state.The simulation results show that the proposed method is more applicable and the probability of tramped into local extremum is dramatically reduced.Experimental results demonstrate that the proposed control scheme is effective and robust against parameter variations and other disturbances.