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. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 67–75, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10049