Decoupling control of three-dimensional electromagnetic forces in linear induction motors based on novel equivalent circuit

Since the single-sided linear induction motor not only produces thrust, but also produces vertical and transversal forces, if no specific control is applied, vertical and transversal forces can have a negative effect on the load propelled by the motor, especially in the application of the railway transit. Therefore, the best solution to the above issues is to independently control the vertical force or transversal force without changing the thrust in the motor. First, this paper presents a 3-D electromagnetic forces, i.e. thrust, vertical and transversal forces, decoupling strategy for the single-sided linear induction motor based on a novel equivalent circuit considering the longitudinal end effect and 3-D electromagnetic forces. Then, the slip-frequency calculator, thrust observer and thrust controller in the conventional vector control for induction motors are reconstructed, and a force decoupling controller is proposed. Finally, the simulation to verify the vector control with the force decoupling controller for the linear motor is performed by using a prototype motor which is used for railway transit.