| Electrical wheels dump truck is a kind of special engineering vehicle which is widely used for transporting rare earth ores.Its transportation distance is short,and the road environment is bad,start braking is frequent.The traditional electrical wheels dump truck adopts mechanical braking,and the braking energy is consumed in the form of heat energy.This creates the need for braking energy to be wasted,thereby increasing the fuel consumption and greenhouse gas emissions from dump trucks.Therefore,it is ver y important to study the braking energy o f the electric wheel dump truck.Vehicle-mounted energy feedback s ystem is widely used in passenger cars,and has a good effect of energy saving and emission reduction.Therefore,the energy feedback system based on super capacitor can be used to rec ycle the braking energy of dump truck,and the energy feedback system can provide auxiliar y power for dump truck.The application of vehicle-mounted energy feedback system will make the energy flow of the vehicle-driven storage and recovery s ystem more complicated.At the same time,considering that the super capacitor of energ y storage device is expensive,and the large scale electric wheel dump truck need to be equipped with large capacity.Therefore,it is necessary to optimize the control method of the system and to allocate the capacity of the energ y storage device under the constraint of the operation demand of the electric wheel dump truck.Firstly,according to the running characteristics of the electric wheel dump truck and the charging and discharging characteristics of the super capacitor,the main circuit structure of the Bi-directional DC/DC converter in the energy feedback system is designed,and the working principle of the DC/DC converter and the change o f the circuit parameters in the system are analyz ed.The research lays a foundation for the control of energy feedback system.Secondly,this paper analyz es the operating principle of the electric wheel dumper and the energy transmission relationship of ea ch part of the power source,and establishes the mathematic model of its driving feedback energy storage S ystem.On this basis,considering the economy,energy recover y effect and system size and weight,the multi-objective optimization function with the maximum working voltage of the Super capacitor group and the number of parallel groups as variables is constructed.The characteristics of super capacitor charge and discharge and the dynamic Performance index of the electric wheel dump truck starting and b raking are used as the constraint conditions.Under the constraint conditions,an improved genetic algorithm is proposed to calculate the global optimal parameters of the multi-objective function,and the performance indexes of the system are compared.The results show that the proposed method optimizes the weight and size of the s ystem and improves the performance of the energy-feedback s ystem.Finally,taking the energy feedback system as an example,the equivalent model of two-wa y staggered parallel DC/D C in Buck State is established.At the same time,the circuit parameters of the DC/DC converter are linearized in a switching period,the small signal model is established,the transfer function is deduced,and the double closed loop controller is designed by correcting the dynamic performance of the system b y PI Controller.In order to verif y the feasibility and validity of the proposed method,the simulation results show that the energy feedback system improves the braking performance and driving performance of the M AT LA B /simulink,and can effectively recover the braking energy and improve the economy of the tipper operation. |
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