Decoupling control of thrust and attractive force a LIM using a space vector control inverter

A new control method for magnetic levitation vehicles using linear induction motors is described. They can generate both thrust and attractive force. Selecting the voltage vectors of pulse-width-modulation (PWM) inverters appropriately allows decoupling control between the thrust and attractive force to be achieved. A module is constructed by four linear induction motors. The levitation control can be accomplished by detecting the gap length and controlling the attractive force of each linear induction motor. Ultrasonic wave sensors can stop the vehicle at any desired position using modified sliding mode control. Decoupling control between the thrust and attractive force was experimentally proved by means of a small model. The fluctuation of the gap length for the step change of the thrust is less than 0.1 mm. It would be suitable for relatively low-speed vehicles, such as an urban transit system.<>