| Linear induction motor (LIM) has been widely developed for a new urban transit system, it has been applied in 10 cities and more cities is constructing and planning. Compared to traditional AC motor drives, LIM as electrical drives has the advantage of little section of underground tunnel, strong climbing ability, low noise, etc, but low efficiency and low power factor, which is the most concerning problem. So it is significant in test of the dynamic performance of thrust and vertical force of LIM.In view of facts above, this paper presents the method of measuring thrust and vertical force of LIM based on maglev principle. It applies the principle of maglev to fix air gap between its primary and secondary coil. It is known that the acceleration of LIM can be measured by use of position sensors installed on it, and then the thrust performance of LIM under decided air gap can be obtained. According to the current of electromagnet controlled the LIM to suspend and the preset air gap, the electromagnetic force of controlled electromagnet can be calculated. And vertical force of measured LIM can be obtained after gravity is been subtracted.In this paper, maglev principle and control method is studied; the dynamic model of hybrid-levitation system is established. In order to guarantee the system suspend steadily, the control method of state feedback is used and the validity and feasibility is proved by simulation. The hardware and software of the suspend system is designed. Finally, a series of experimental study are done and the stability is confirmed.
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