Position or speed signals are the key control parameters in long primary linear induction motor (LPLIM) drives. This paper quantitatively analyses the relationship between the speed measuring error and the motor thrust. The system allowable measurement error with the premise satisfying certain thrust fluctuation range under high speed is deduced in this paper. Based on the above results, the design of the grating strips is optimized. Even if the mover is crossing the rail gap, the error of the speed measurement system can still be kept within the range of thrust fluctuations, and specially, the accuracy requirements for track installation are reduced. Finally, the simulation and experiments verification are completed.

LPLIM， position-speed measuring， grating strips， rail gap， thrust fluctuations