Sliding Mode Control and Observation for Complex Industrial Systems - Part II

W ITH the recent rapid developments in industrial technology, the modern industrial systems have become more and more complex requiring a greater attention to be paid on the stabilizability, the robustness, the reliability, and the optimization issues. The recent developments in slidingmode control and observation techniques serve as powerful tools in this respect. The use of sliding mode control offers a number of advantages: insensitivity to external disturbances, system reduction, high accuracy, and finite time convergence. However, there are still several remaining issues that should be solved before it can be extensively used in the industry in the near future, that is, chattering effect, requirement of an accurate model of the system, relative higher complexity and higher implementation cost compared to existing linear controllers. This “Special Section on Sliding Mode Control and Observation for Complex Industrial Systems—Part I” of the IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS presents to the industrial electronics community the most recent advances with topics, such as applications of sliding mode control in industrial electronics (power grid, uninterruptible power supply, robot manipulators, etc.), design and implementation issues of sliding mode control and observation techniques. It is our pleasure to present this Special Section. Due to the high number of good papers submitted, this Special Section will be divided into two parts. In item 1) of the Appendix, a hybrid active–passive linear heave compensation system with a nonlinear cascade controller is designed to reduce the adverse effect of the unexpected vessel heave variation on the response of the underwater payloads. An adaptive extended disturbance observer is constructed to estimate and separately compensate the external perturbations. Sliding mode control is designed for the outer position tracking loop in order to compensate the disturbance estimation error while the backstepping technique is employed in the inner pressure control loop. In item 2) of the Appendix, a novel state/model-free variablegain discrete sliding mode control strategy is presented to suppress the unmolded position-dependent dynamics and disturbances in the nanopositioning wafer stage. To balance the tradeoff between the robustness and the chattering, the gain of the switching control term is designed to be variable. The proposed scheme facilitates a rapid implementation without either a parameter model or a state observer, and excellent tracking performance with the optimal controller parameters.