| With the rapid development of the automotive industry,car ownership is on the rise,environmental protection and energy saving has become a main trend of automobile,with driving comfort requirements,optimization and upgrade of automotive transmission becomes a hot topic.At present,electric transmission and electro-mechanical transmission are constantly expanding in terms of passenger vehicle,and hydro-mechanical transmission still remains in the area of construction vehicles and special vehicles,which is blank for optimization of transport vehicle transmission system.Consequently,on the basis of a large number of related documents,aimed at transport vehicle,research for hydro-mechanical transmission system had done as follow:Based on selection whose research carrier is transport vehicles and research object is power split hydro-mechanical hybrid transmission system,and characteristics research requirements,started from structure of transmission system,different levels of functions and structure types were researched and analyzed,and hybrid transmission program with two modes was determined which used single planetary to split,fixed gear and single planetary to confluence,and volumetric speed control.And running condition and working characteristics under different modes were researched and analyzed.According to transmission program,mathematical analysis was done for planetary transmission and ratio characteristics in variable speed control mode,the characteristics system adjusted output speed by change displacement of hydraulic components was confirmed.Introduced displacement rate of hydraulic components,and analyzed speed control of system,four-parameters speed control rule was determined which took expected speed as reference signal,two displacement rates of hydraulic components as control signal,stroke adjustment factor as correction signal.The simulation model of transmission system based on Matlab/Simscape was built,which was validated by inputting HYZEM Urban and HYZEM Extra Urban respectively.Simulation results show that the system has good characteristics for variable speed control which adjust speed smoothly and reliably.The project analyzed further energy distribution of braking(or decelerating),and energyrecovery characteristics was researched,hydraulic components and accumulators were designed for parameter matching.Based on balance equation,energy was analyzed by using mathematical method for braking,and three-parameters control strategy was determined which used output pressure and speed as referenced signal,relative variable rate of hydraulic component as control signal.Braking simulation model based on Matlab/Simscape was built,which was validated by inputting different initial pressures of accumulator.Simulation results show that the system could recovery braking energy in braking,and total recovery and recycling speed would be under the influence of accumulator initial pressure.Finally,switch of system mode was researched based on dual modes,and switching logic diagram was set out,which was controlled by several signals.For big power and torque output,mathematical analysis was made for output power and torque of system,and results show that the system would output larger torque or power due to hydraulic system under the same conditions.Reversing condition was also researched for single hydraulic driving which was validated by adjusting energy recovery simulation.The simulation result show that the system could complete reversing independently under energy status of accumulator,and the efficiency of energy recovery and secondary utilization was up to 33%. |
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