Robust Sliding-Mode Control for Dual-Stage Nanopositioning Systems

In this article, a robust feedback control scheme is presented for dual-stage nanopositioning platforms. Dual-stage nanopositioners consist typically of a long-range, low-speed actuator connected in series with a low-range, highspeed actuator. A sliding mode control structure is designed to dedicate sliding actions to the short-range actuator, effectively utilizing the secondary actuator for disturbance rejection. A multi-input, single-output high-gain observer is incorporated for robust state estimation. A hybrid serial-parallel-kinematic positioner is selected to demonstrate robustness of the control design through the mitigation of cross-talk and hysteresis nonlinearities. Simulation results show significant performance improvement on robust control of a standard long-range actuator, reducing the tracking error of a desired 100 Hz triangle trajectory by almost 90%. When disturbances are bounded by the long-range actuator control system to less than the range of the short-range actuator, root-mean-square and maximum error can be reduced to less than 1% of the magnitude of the desired trajectory.