Frequency Shaping Sliding Mode Control for Axial AMB Systems

N.-C. Tsai and C.W. Chiang (Taiwan)

Keywords

nonlinear control, sliding mode

Abstract

A Sliding Mode Controller (SMC) with dynamic switching surface is proposed for axial motion control of active magnetic bearings systems. The so called dynamic SMC in this paper is designed to attenuate the high-frequency excitation, from unmodeled rotor dynamics, and select appropriate corner frequencies of the closed-loop systems. The detrimental impacts of potential perturbation in the neighborhood of natural frequencies are alleviated. The experimental and simulation results verify the performance of dynamic SMC by its fast regulation capability and smaller overshoot, in comparison with conventional SMC. A test rig of imbalanced beam is implemented to be appropriately real-time controlled, with satisfied performance requirement and robustness with respect to the system parameter uncertainties. The magnetic force is generated by a DSP-based digital microprocessor. In contrast, a counter example of conventional PI (proportional-integral) controller, which is mostly employed in axial rotor motion, is presented to have potential instability.

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