In this paper, a robust sensorless speed observer-controller scheme for a permanent magnet synchronous motor (PMSM) is proposed. First-of-all, the observability of the PMSM is studied and fixed for the surface permanent magnet synchronous motor(SPMSM). Secondly, a complete model observer based on sliding mode technique in order to estimate both position and speed is designed. Then, a high order sliding mode controller is developed. By using this technique, the well-known “chattering” phenomenon is highly attenuated. The stability and the robustness of the controller-observer scheme are proved. The overall system is tested by simulation with significant tests of robustness in the framework of an industrial benchmark.