Research On Wireless Electricity Charging System For Mining Electric Locomotive Storage Batteries

Mining electric locomotives are mainly utilized in the underground transportation of coal mine and the long distance ground transportation. It is an important type of equipment in the mining transportation area. Most electric locomotives use storage batteries as power source. At present, the traditional method for mining electric vehicle battery charging is conducted by removing the battery, putting into the charging chamber and using wired electric charger. Since the use of such charging method, a couple of problems have been noticed, such as the electric sparks produced in the contact spots, the lead exposure and great consumption for contacted components., etc.. Meanwhile, such direct contact charging method is likely to be influenced by the dust, water and contaminants in the environment, causing certain amount of limitations. In addition, due to the charging method can only be carried out in fixed sites, it brings lots of inconvenience to the mining production. Therefore, this dissertation designs a new prototype of storage battery wireless electricity charging system based on inductively coupled electric power transfer technology. This system is capable of transferring electrical energy wirelessly. Based on electromagnetic coupling principles, energy can be transferred from the primary side to the secondary side through electromagnetic fields, offsetting the deficiencies of the traditional wired electric power transfer methods.This dissertation takes advantages of inductively coupled power transfer technology based on the loosely coupled transformer. It modifies the traditional electric locomotive storage battery charging systems through the replacement of the core part, the tightly coupled transformer with the loosely coupled transformer, makes the primary side of the transformer apart from the secondary side and uses a manipulator to drive the primary side to make it dock with the secondary side. By doing this, both sides of the transformer will have a relatively ideal position, making it feasible the contactless electricity charging for the electric locomotive. The research contents of this dissertation mainly include:1. Modeling and calculation research of the loosely coupled transformer The loosely coupled transformer is an important part of the wireless electricity charging system and also the critical component for realizing contactless power transfer. There exists a certain amount of air gap between the primary side core and the secondary side core. Relatively large air gap directly reduces the coupling coefficient for the loosely coupled transformer, reducing the energy transfer efficiency. In this dissertation, an EI type loosely coupled transformer with two separate sides is designed, based on the original transformer in the storage battery charging cabinet. Calculation and simulation are conducted to investigate the influences of air gaps, displacement errors on the coupling capability of the transformer, to deduce the quatitative accurary alignment criteria.2. Kinematic analysis of the driving manipulator Due to a couple of factors including the high power of the mining storage battery locomotive, the large mass of the primary core and coil, making it hard for alignment, a manipulator drive system with six degrees of freedom(DOF) is applied for alignment. On the basis of the manipulator design, this dissertation uses the D-H space modeling method, conducts research on the forward kinematics problem and the inverse kinematics problem. For the forward kinematics problem, through the space coordinate transformation method of two adjacent joints, the method of calculating the spatial position and orientation of the end execution unit based on each joint angle of six degrees of freedom manipulator is investigated. For the kinematics inverse problem, the six joint angles of the manipulator can be calculated through the measurement of the spatial position and orientation of the end execution unit, combined with the spatial limitations of the manipulator. Finally, the kinematics model of the manipulator is investigated through MATLAB for simulation research.3. Research on trajectory planning technology for the manipulator To improve the precision of motion for the manipulator driving the primary side core, this dissertation conducts research about the trajectory planning technology, based on Cartesian space coordinates and the manipulator joint space coordinates. Firstly, the linear interpolation method and the circular arc interpolation method are studied for the straight line and the circular arc trajectory in the Cartesian space. Then, in the joint space, the trajectory planning method and optimization strategy of a single joint are studied through the use of five polynomial interpolation. Finally, for the requirements of motion coordination of the six DOF manipulator, the trajectory planning method of the manipulator with six DOF is investigated.4. Experimental research on power transfer performance for the EI type loosely coupled transformer and the high-precision positioning technology for the manipulator The prototype of the EI type loosely coupled transformer is manufactured for investigating the actual influences of parameters including air gap, horizontal and vertical displacement on power transfer efficiency to verify the simulation results and present the high-precision positioning requirements for wireless electrical charging system. Based on the trajectory planning methods, specific trajectory is made for the manipulator to drive the primary core to dock with the secondary core on a high-precision basis, with the precision reaches 0.5mm. So the requirements for wireless electricity charging system for the mining storage battery electric locomotive are met.