Method to Control Multiple Segmented LLSM without Position Encoder

Abstract

In recent years long stator linear synchronous motors (LLSM) started to replace the typical rotating to linear converters like belts, chains, screw systems, pulleys, disks and so on. With LLSM a lot of drawbacks in the machine concepts and design can be prevented. For long tracks, reducing reactive power and individual control of numerous moveable units, the track is segmented in several fed stator units. Because of the LLSM construction an operation with a physical position encoder is not desirable. For that reason position observers should be used instead. In this paper a method to control the multiple segmented LLSM without position encoder is proposed. The special behaviour during entrance and exit of one moveable unit in an active stator segment is described and the control concept via a master slave relationship is proposed. Experimental results are presented to demonstrate the performance and feasibility of the proposed method.