New initial pole-position estimation of surface PM-LSM using reference currents

This paper proposes a new algorithm for the initial pole-position estimation of a surface permanent-magnet linear synchronous motor (PM-LSM), which is carried out under closed-loop control without a pole sensor and is insensitive to the motor parameters. This is based on the principle that the initial pole position (IPP) is calculated by the reverse trigonometric function using the two reference currents, which are received from the speed controller. Compared to published research, the proposed algorithm does not utilize the impedance ratio like the general methods and it can be widely applied without the limitation of the motor structures. The effectiveness of the proposed algorithm is verified by testing a surface PM-LSM with large cogging. Its results show the IPP is well estimated within a satisfied moving distance and a shorter estimation time, even if a large disturbance such as cogging exists.