Research On The Fuzzy Control Of Battery Charge In Hybrid Engineering Machinery

The research and development of hybrid engineering machinery has broadapplication prospects, because of high energy consumption and poor emissions intraditional single power source engineering machinery. As an auxiliary power source, theperformance of energy storage device directly affects the work efficiency of engineeringmachinery, and the cycle life of MH-Ni battery which is commonly used as energy storageelement is directly related to the cost of hybrid engineering machinery. Therefore, how tocontrol the energy storage unit to satisfy the demand of absorbing and releasing energy,improve the utilization of energy recovery and extend the life in hybrid constructionmachinery is one of the urgent problems of the hybrid engineering machinery.This paperproposes a charge and discharge fuzzy control strategy of MH-Ni battery in hybridengineering machinery through the actual product and related scientific research projects,due to the fact that charging and discharging of battery is frequent in hybrid engineeringmachinery, and energy storage unit needs to quickly absorb and release power.In this paper, the research is completed as follows:(1)This paper establishes a mathematical model through the analysis of equivalentcircuit of MH-Ni battery;(2)Through analyzing the actual working conditions of engineering machinery, thefuzzy control strategy of MH-Ni’s charge and discharge in hybrid engineering machineryis proposed;(3)According to the fuzzy control theory, the fuzzy control system of electriccharging and discharging of MH-Ni battery is built in hybrid engineering machinery, andfuzzy controller is designed according to the selected input and output variables;(4)The simulation model of fuzzy control system of MH-Ni battery is built byMATLAB, and is tested with real-time power of5t hydraulic excavator motor.Firstly, taking a parallel hybrid hydraulic excavator as an example to describe theprocess of determining the parameters of MH-Ni battery as the energy storage element indetail. By analyzing the characteristics of MH-Ni battery, RC circuit model is chosen asthe equivalent circuit model of charging and discharging of battery in this paper, and themathematical model of storage battery is established on this basis.Through analyzing the actual working conditions of engineering machinery, andcombined with the technology of battery’s rapid charging and discharging, the fuzzy control strategy of battery is proposed. According to the actual control circuit of MH-Nibattery of hybrid engineering machinery, the block diagram of fuzzy control system isbuilt.The difference of the maximum battery voltage and the measured voltage is ΔU, thevoltage difference change rate is ΔU/Δt. ΔU and ΔU/Δt are the input variables, and outputvariables is duty cycles R, the two-dimensional fuzzy controller is designed, the fuzzycontrol rule table is established, and select the appropriate fuzzy, fuzzy reasoning anddefuzzification method, by changing the duty cycle, it can change the charging current, soas to achieve the control of voltage and current and the purpose of rapid the energyabsorption and the energy liberation.Finally, using MATLAB software, the model of MH-Ni battery and the fuzzycontroller of two-dimensional model are established, and on this basis, the fuzzy controlsystem simulation model of MH-Ni’s charging and discharging is built in the hybridengineering machinery, and simulated with5t hydraulic excavator motor. Simulationresults show that the control strategy can quickly absorb the excess power and releasepower, and meet the needs of complex working conditions of the hybrid engineeringmachinery.