Pole-clustering using sliding-mode techniques for motor drives with bounded control

A two-degree-of-freedom (DOF) global sliding-mode control (GSMC) scheme with adjustable performance robustness is proposed for motor drives with bounded control and system uncertainty. Through introducing an auxiliary process and eliminating the reaching phase, the sliding dynamics is equivalent to the overall closed-loop system dynamics, and can be adjusted to yield the desired performance robustness. By fully utilizing the tolerance in performance specifications, the chatter phenomenon is alleviated while the performance specifications are satisfied. In dealing with the problem of bounded control, an estimation process is proposed for estimating the maximum control input required by the uncertain system with external disturbance. The estimation process can be utilized in two ways. For specific output command, the estimation result reveals the maximum control input that the actuator must deliver in order to maintain performance robustness. On the other hand, given bounds on control input, the estimation process can be applied to find the range of allowable output command, within which the performance robustness is guaranteed. Simulation results show the feasibility of the control scheme and the estimation process.