Reserch On Direct Torque Control For Electric Wheel Dump Truck Tractor

Electric-wheel mining dump truck has large carrying capacity, high efficiency, etc. It is used as a transport for large-scale opencast and water conservancy construction. Along with the larger mine scale, it needs higher performance.Compared with the mechanical equipments, the electric wheel dump truck with high energy efficiency, simple structure and flexible control, etc. Therefore is well favored by major manufacturers.Its variable frequency speed control technology refers to different subjects, such as power electronics and electric transmission, automatic control principle and microcomputer control technology. In order to make the dump truck has good stability and climbing ability under low speed condition, it is especially important to research a kind of variable frequency control method which can be applicable to the dump truck. Firstly, this paper introduces the development of electric-wheel dump truck and the composition of AC drive system, By introducing space vector and coordinate transformation theory and establishing the mathematical model of tractor in different coordinate system, which laid a foundation for the following control strategy research. Secondly, the paper analyzes several main principles about variable frequency speed control, and then combines with the characteristics of electric wheel dump truck. Finally, the direct torque control technology is chosen as a method to the dump truck tractors.Because of the traditional direct torque control technology with large torque ripple, high current harmonic content, unfixed-switching frequency at low speed, which can’t apply to the control of tractor directly. So this paper establishes a model of SVM-DTC bases on voltage space vector modulation method, and analyzes the principle of torque adjustment and magnetic linkage adjustment.Due to it is difficult to measure the induction motor stator flux directly, the key problem of realizing high performance direct torque control technology is accurately calculate the stator flux linkage. For stator flux observation susceptible to the influenced with the stator resistance variation, this paper puts forward two different methods. The first method is using fuzzy neural network technology to compensate the change of the stator resistance online, and combining with the modified voltage model to observe stator flux; The second one is using the theory of extended state observer to build a stator flux observer. It can effectively avoid the influence of the stator flux change. For the mentioned methods in this paper, a simulation was to be done in matlab/simulinkThis article also introduces software and hardware platforms about the tractor direct torque control experiment. On one hand, hardware part mainly analyzs the DSP chips and peripheral circuits, sampling circuits, orthogonal coding circuits and IGBT driver chips; On the other hand, software part introduces the main program, period interrupt, sampling interrupt program and other functions. Finally the SVM- DTC and flux observation algorithm which were proposed in this paper raised the experiment platform, and also the experimental results show that the feasibility of the algorithm.