Study On Three-parameters Comprehensive Shift Strategy For Construction Vehicle

Construction vehicles are widely used in the field of national infrastructure andnational defence, playing an more and more important role.Due to the easily changingand complex load, the powertrain usually adopts hydromechanical transimission, butthe effieciency of the hydromechanical transmission is very low,especially under theheavy working condition. Adding the numbers of the transmission box could solve theproblem, but frequently shifting makes the driver tired easily, and then decrease theefficiency of the production. So,applying automatic shift on construction vehicles willimprove the performance in many aspects, for example, the power performance,energy-saving and reducing the labor intensity of drivers, this applying is verymeaningful in practical significance. However, limited to the special workingsituation of the construction vehicles, the working load will cut off most of the engineoutput, that is the biggest difference between construction vehicles and cars,so theautomatic shift schedule for road vehelces can not be applied in construction vehiclesin the totally same way. In a word, it is very meaningful in reality to study theautomatic shift technology speciallized for construction vehicles.This paper was supported by the Specialized Fund of Higher Education of Chinafor Doctoral Project “Study on the automatic transmission technology for constructionvehicles based on New3parameters”, choosing ZL50wheel loader as the prototype,aiming at improving the comprehensive performance, the automatic shift strategywere researched in-depth.Focusing on the operation characteristics of construction vehicles, the operatingload factor and its calculation formula were defined to describe the operation load,analysed its effection to the flow direction of engine power output.Taking the ZL50loader as the prototype,its mathematical model of the powertrain system of the loaderand the vehicle dynamics equation were established.Based on the analysis of dynamic and energy-saving shift schedule, both the traction performance and energy-saving efficience of construction vehilces were takeninto account, defining the comprehensive coefficient and its calculation formula toquantize dynamic output and energy-saving. Aiming at improve the comprehensiveperformance, the throttle opening, vehicle speed and operating load factor were takenas the shift control parameters, as a result, the comprehensive shift schedule wasproposed. Using multi-variable multinomial regression method, the calculation of thebest shift speed and the3-D shift curved surfaces were presented.In the simulation environment of Matlab/Simulink, the simulation model ofautomatic transmission system for construction vehicles was established. Thesimulation experimet was carried out to analyse the effect of the comprehensive shfitstrategy, the results valided the effect of the proposed shift strategy preliminarily. Thiscomprehensive shift strategy could change its control effect according to the throttleopening. The total effect was between dynamic and energy-saving strategy. Thevertification experiment was carried out on the construction vehicle powertrain testbench. The experiment results demonstrated that the comprehensive shift scheduledeveloped in this paper was reasonable.