Walking. Electric Forklift Motor System Efficiency Optimization Control Study

Due to high start frequency and long-time working under light load state, electric forklift truck's track driving motor always functions in an uneconomical and inefficient conditions, which wastes a lot of battery energy, deduced the integral performance. With the low or medium(and sub-medium) power asynchronous motor of electric forklift truck as a research object, the study on optimizing driving motor was done in this thesis. The main content are as follows:The current situation and future tendency of the development of electric forklift truck at home and abroad was summarized ,and the component of the energy-consumption of track system and promotion system were analysed. Compared to the conventional energy-saving methods of asynchronous motor, integrating consumption model control and minimizing power searching strategy, arithmetic of optimizing excitation current using fuzzy logic was brought forward to command the motor work under minimal consumption status.In allusion to the motor model built in MATLAB/Simulink software ignoring iron loss, a new arith model with iron loss in M-T coordinate is put forward. It is more in accord with the real status, and simpler, more reliable, and easier to realize as well. Using this AC motor model, a model of speed control system for electric forklift truck driving motor, which is based on SVPWM, is established.To verify the accuracy of the mathematic model of the induction motor, we measured the input current, rotor frequency and other datas of the track motor. By compared to the simulation result, it shows that the mathematical model of the induction motor with iron loss is accurate .By measuring the efficiency of the driving motor, it provides a foundation to design the optimized efficiency of the control system.The optimizing strategy with fuzzy logic control in asynchronous motor was designed. By calculating the proportional parameter online and coordinating fuzzy membership functions of input and output, the surging problem on the point of maximum efficiency was solved. With this methods, the maximum efficiency point was quickly searched with good dynamic response and energy-saving effect. In addition, the software of fuzzy logic control was designed.