Study On Power Matching And Nonlinear Steering Dynamic Of The Extended-range Vehicle With Multi-motor Driving

With the higher speed of the travelling vehicle, the more important for theproblem of the stability of the vehicle high speed and large angle steering, nd that isalso more serious in the study of vehicle dynamics, while the vehicle with four wheelsteering can largely improve the stability of the high speed and the large anglesteering. This paper based on the national863program major projects of moderntraffic technology’’ the extended-range/plug-in heavy commercial vehicle chassisdevelopment’’(Approval no.:2012AA111106), takes the extended-range sanitationgarbage vehicle with four-motor driving as the object, studies the matching method ofthe extended-range vehicle with multi-motor driving and the dynamics features of thefour wheel nonlinear steering vehicle from3different aspects, which are the vehiclenonlinear model, the motion stability and the structural stability of nonlinear dynamic.From the studies, gets the matching method of the extended-range vehicle withmulti-motor driving and the rules of four wheel steering, provides theoretical basisand the research gist for the study of dynamic system matching of the extended-rangevehicle with multi-motor driving and the application of four wheel steeringtechnology in vehicles. The main work is as follows:First the paper puts forward the power matching principles and methods of theextended-range vehicle with multi-motor driving based on the traditional powermatching method. Takes the extended-range sanitation garbage vehicle withmulti-motor driving as the object, gets the initial power matching results of theextended-range sanitation garbage vehicle with multi-motor driving base on thetraditional matching theory of the dynamic system; it researches the driving methodeffects on the power system matching of the studied vehicle, finds that when thestudied sanitation garbage vehicle drives by multi-motor the number of motor is noless than four, or the vehicle may not be able to realize the start; Then analyses theefficiency area of the driving motor and the range extender, obtains the high efficiencyarea which the extended-range vehicle with multi-motor driving works coordinated toameliorate the vehicle efficiency.Takes the extended-range heavy vehicle with four wheel driving as example,builds the nonlinear steering dynamic model with a multidimensional and thelongitudinal and lateral coupling, carries on steering simulation for the extended-rangevehicle with four-motor driving, obtains the results as follows: finds that the model is with good following effect and can be used to research the control strategy of thevehicle handling stability from handling performance simulation; From the vehiclesteering dynamics simulation knows that the steering stability of vehicle at a lowspeed is better than that at a high speed, regardless of the vehicle high speed and lowspeed, the steering stability becomes lower with the increasing angles. Then conductsthe four wheel steering simulation, when the vehicle steers at a low speed, controls therear wheel and the front wheel steering with reverse direction to advance the steeringflexibility because the steering stability is not the main influence factors now; whenthe vehicle steers at a high speed, controls the rear wheel and the front wheel steeringwith homodromous direction to enhance the steering stability because the vehiclestability at a high steering speed is worse than that at a low steering speed.Based on the movement stability theory of nonlinear dynamic, constructs theLyapunov function of the extended-range heavy vehicle with four-motor driving, doesthe qualitative research on the nonlinear movement stability of the extended-rangeheavy vehicle with four-motor driving, gets that the vehicle at the initial status isasymptotically stable in the sense of Lyapunov; conducts the mensurable research onthe vehicle nonlinear steering is asymptotically stable in the initial state of theneighborhood, which is in accord with the Lyapunov results. Studies the four wheelsteering effect on the equilibrium point of the vehicle nonlinear steering, and knowsthat when the vehicle steers with a high speed, the steering stability is depravationwith the rear wheel and the front wheel steering reversely; as the increasing of the rearwheel angle, when the rear wheel and the front wheel steering with homodromousdirection, the dynamic system of heavy vehicle can not easily reach the instabilitystate of the equilibrium point, the steering stability increases; Analyses the front wheelangle impacts on the equilibrium point of the vehicle steering dynamic system, withthe increasing of the front wheel angle, the vehicle steering stability reduces; And alsogets that the steering stability is not easy to the instability with a low steering speed.The conclusion is in conformity with the3rdchapter.Studies the structural stability of nonlinear dynamic, knows that the extended-range vehicle with four-motor driving does not occurs Hopf bifurcation but raises thestatic saddle-node bifurcation base on the nonlinear dynamic theory of the staticbifurcation and the dynamic Hopf bifurcation when steady steering; Analyses thevehicle speed effect on the bifurcation of the nonlinear steady steering vehicle, gets asthe vehicle speed increasing, the bifurcation critical value can be easily reached, the steering stability of the vehicle reduces; Studies the front wheel angle effect on thebifurcation of the nonlinear steady steering vehicle, knows that with the increasing ofthe front wheel angle, the bifurcation critical value of the vehicle steering decreases,the steering stability of the vehicle lowers; Analyses the rear wheel angle effect on thebifurcation of the nonlinear steady steering vehicle, gets the bifurcation critical valueof the vehicle steering becomes lessen when the rear wheel and the front wheelsteering with reverse direction, the steering instability can be easily attain and thesteering stability of the vehicle reduces. the bifurcation critical value of the vehiclesteering adds and the steering stability of the vehicle increases when the rear wheeland the front wheel steering with homodromous direction. Then from the balancedomain to analyses the nonlinear steering vehicle of the extended-range vehicle withfour-motor driving, gets that when the rear wheel and the front wheel steering withhomodromous direction, the balance domain of steering vehicle reduces, thepossibility of the equilibrium instability state raises when vehicle steering, it is easilyfor the steering vehicle to be instability; When the rear wheel and the front wheelsteering with reverse direction, the balance domain of steering vehicle raises, it is hardfor the steering vehicle to be instability and the stability improves; And the rear wheelsteering effect on the speed bifurcation relates to the size value of the front wheelangle, the greater the front wheel angle, the rear wheel steering has the smaller effecton vehicle nonlinear steering.