Decoupled Control Of Traction Force And Normal Force In Linear Induction Motor Drive

Linear metro is a new urban rail traffic pattern, which using linear induction motor drives and wheel-track to complete its support and guidance. It became more and more applicable due to its low cost, small vibration, low noise, and high climbing ability, excellent traction capacity through small curve radius, and low consumption, little pollution, better security and many other advantages.The main shortcoming of linear induction motor is the low efficiency and power factor, which is due to the air-gap and edge effects. And the normal force between the primary and secondary is another reason of the low efficiency. This article analyzes the shortcomings of linear induction motor through the end effect and the normal force characteristics. Based on the analysis, an effective compensation and optimal control scheme which can increase the energy utilization is proposed.In this paper, the electrical properties of linear induction motor caused by the special structure especially the dynamic end effect are analyzed at first. Then the dynamic mathematical model of linear induction motor taking into account the edge effect is proposed. Based on this, a new s-function simulation model of linear induction motor is constituted. After that, an analysis of linear induction motor normal force and traction force characteristics is developed, and the characteristic curve of the electromagnetic force is received from the simulation experiments. The results show that the normal force is 2 to 5 times of the traction force especially at the rated speed.Based on the analysis of the electromagnetic force of linear induction motor, the decoupling control scheme of traction force and normal force based on vector control is proposed and the linear induction motor control simulation system is established. This scheme use optimized flux control to minimize the normal force without change the performance of LIM control system. The simulative experimental results validate that this approach can reduce the effectiveness of the electrical energy consumption. Finally, the decoupling control scheme was achieved by using the linear motor comprehensive test-bed. The experimental results show that the proposed control scheme has good steady-state and dynamic performance.