A transfer-function approach to the analysis and design of zero-power controllers for magnetic suspension systems

A transfer function approach is applied to the analysis and design of zero-power controllers for magnetic suspension systems. The general structures of controllers achieving zero-power control are derived for both current- and voltage-controlled magnetic suspension systems. For the former type of system, there are two basic approaches: feeding back the velocity signal and introducing a minor feedback of the integral of the current. Both approaches are applicable to the latter type of system. In addition to them, the self-sensing suspension also achieves zero-power characteristics automatically. A direct synthesis method for zero-power control is developed based on the analysis. Several experiments are carried out with a single-degree-of-freedom model. The experimental results show the effectiveness of the proposed synthesis method. (C) 2002 Wiley Periodicals, Inc.