Sensorless control of linear permanent magnet synchronous motors using a combined sliding mode adaptive observer

A novel combined sliding mode adaptive observer for flux and speed estimation of direct thrust controlled surface mounted Linear Permanent Magnet Synchronous Motor (LPMSM) without using position sensors is proposed. The observer comprises a linear state observer combined with a novel nonlinear sliding mode component. The sliding mode component is improved by using two boundary layers which reduce the chattering without compromising the robustness. The novel observer is experimentally validated. The flux, speed and position estimation errors are small resulting in reliable observer performance.