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

A control method for magnetic levitation vehicles using linear induction motors which can generate both thrust and attractive force, is described. By selecting voltage vectors of PWM inverters appropriately, control with decoupling of the thrust and attractive force is achieved. Levitation control is accomplished by detecting the gap length and controlling the attractive force of each linear induction motor. Ultrasonic wave sensors allow stoppage of the vehicle at any desired position using modified sliding-mode control. Decoupling control was experimentally confirmed for the module. The fluctuation of the gap length for step change of the thrust was less than 0.1 mm. The module is judged to be suitable for low-speed vehicles, such as those found in urban transit systems