Design of air gap control for linear drives with minimal power loss

Abstract

This paper is related to a doubly-fed linear motor, which is applied for a mechatronic railway system based on the operation of shuttles. Compared with conventional trains, a single axle undercarriage is developed for the shuttle. The primary of the linear motor is installed between the rails and the secondary is fixed on the axle via the middle. In order to prevent the secondary from pitching and maintain a constant air gap between the primary and the secondary, a proper air gap control strategy must be designed without any influence on the motion control, a real time measurement of the air gap is also required. On the basis of choosing a right reference frame, the author proposed a separate air gap and velocity control and a coupled air gap and velocity control in the previous papers. This paper focuses on the topic of having an air gap control with minimal power loss to generate the control effect. Through extensive theoretical investigations, a conclusion is drawn for the practical implementation, i.e. a combination of separation and coupled air gap and motion control. Finally, the experimental results are presented and analyzed.