Research On Transmission And Energy Saving Characteristics Of Tractors Equipped With Mechanic-electronic-hydraulic Powertrain System

Tractor is the most important power machinery in the development of agricultural mechanization,and is currently facing two major problems of global oil resource shortage and pollution emission.The development of a new generation of energysaving tractors will become the focus of future research under the guidance of the national policy on upgrading agricultural equipment.Tractor operating conditions are complex,need to do field work and road transport,with a complex working environment,poor self-adaptability and poor power matching characteristics.In response to the above situation,this paper proposes a Mechanic-electronic-hydraulic powertrain system(MEH-PS)based on the currently popular Hydro-mechanical transmission(HMT)and hybrid technology.To make the tractor from low speed to high speed,low load to high load have good drive performance and high economy.The main work and conclusions of the paper include the following four aspects.1.The operating principles and characteristics of three hybrid architectures of series,parallel and mix with hybrid torque and speed coupling methods,are analyzed,on the basis of which three models of MEH-PS suitable for tractors are proposed,and one of the MEH-PS with both torque and speed coupling methods is studied in depth.2.Completed the selection of power source and transmission components,introduced the implementation principle of MEH-PS drive mode and transmission mode,and analyzed the performance of MEH-PS in turn,including speed regulation characteristics,speed characteristics,torque characteristics,power split and efficiency characteristics.The full-load acceleration process of the tractor is studied by Simulation X and simulation results are consistent with the theoretical analysis,and the operating parameters of each component are within the rated parameters,and the MEHPS is well matched with the tractor.3.The whole tractor control architecture was established.The HMT speed ratio control strategy is developed to enable the engine to operate on the best economy curve under different loads.Develop a rule-based mode identification strategy to reasonably classify the power source operating intervals.For the problem of power distribution of multiple power sources working together,an equivalence factor is introduced to calculate the equivalent fuel consumption at each moment to achieve the optimal power distribution among the power sources.4.The energy performance of the tractor equipped with MEH-PS were conducted under EPA standard operating conditions and field operation conditions.The results show that the developed energy management strategy can reasonably allocate the work of power source,and the HMT can continuously change the transmission speed ratio according to the resistance of travel mechanism,so that the engine operating point is distributed more in the low fuel consumption area.Comparing with the powershift tractor and CVT tractor announced by DLG,the tractor equipped with MEH-PS has advantages in fuel consumption under different operating conditions,which verifies the feasibility of the scheme.The MEH-PS proposed in this paper provides design ideas for tractors to improve operational efficiency under complex working conditions,and promotes the electrification of tractors,which also provides a solution for modern agriculture to reduce tractor energy consumption under a variety of working conditions.