Electrical two speed transmission and advanced control of electric vehicles.

摘要

The performance of electric vehicle propulsion depends on many factors. This thesis investigates its two basic aspects. The first aspect is the introduction and the development of the principle of electrical two speed transmission by induction motor stator winding switching schemes. The second aspect is the investigation of fuzzy logic control for the vehicle propulsion.; Electric vehicles need a high torque to accelerate in the starting operation and a high speed capability in the normal operation. A conventional solution is using a multi-gear transmission. This increases the vehicle size, weight and cost, and reduces the efficiency. Analysing the electric vehicle requirements shows that the inverter capacity is determined by the high current during the acceleration and the high voltage in the normal operation. If the motor line current is kept within the rated value while the current through each winding branch is at overload level, the inverter current is then limited to the rated value. Therefore, the overload requirement of the inverter is eliminated.; Three switching schemes have been investigated and compared theoretically by computer simulation, and experimentally by laboratory tests. The series-parallel scheme presents the best performance. It can improve the vehicle acceleration 23.5% faster than the traditional propulsion by simulation results and 22.8% by test results.; The performance of the conventional Mamdani type fuzzy logic control is investigated for the vehicle propulsion. By simulation and experiment, comparison of the fuzzy logic control and the conventional Proportional plus Integral (PI) control demonstrates that the fuzzy logic control is less sensitive to the variations of system parameters. The simulation study also reveals that the fuzzy logic control can be refined to achieve a better performance. Its rule base quantization can be determined by using PI design and tuning experience. Continuous defuzzification is proposed to produce a finer regulation in the steady state, which makes the controller tuning easier as compared with the methods using two rule base tables or one table but more rules. The analysis of membership function shapes indicates that at least one of the first order partial derivatives of the membership functions should be non-zero at any time instant to achieve a non-saturated control. The tuning of the PI proportional coefficient in real time, defined as the error driven PI control, can achieve a similar control performance to the fuzzy logic control but this can be achieved in a simple and straightforward manner. The proposed error driven PI control has been studied by computer simulation and tested in the laboratory for the electric vehicle propulsion system. Both stability and sensitivity analysis on this control have also been conducted. The proposed approaches have been confirmed by test results.