A Research On Handling Stabilization Of The Four-wheel Independently Drive Articulated Electric Coach

Our country is still a little far from other developed countries in term of vehicle industry which is an important part of the national economy.Therefore,there is still much room for our development and growth,especially in electric vehicle.What’ more,nowadays,the total number of the vehicle is growing gradually,and it trigger some problem about environment and energy.The advantages of electric vehicle,such as zero-emission characteristics,make it develop faster.From a macro perspective,China should closely seize opportunities of developing electric vehicles and its core technology with the pace of globalization to reach the advanced level.In electric vehicles,high-performance distributed drive electric vehicles are one of the heated topics.The electric motor is mounted directly in the vicinity of the wheel or just in the wheels.The advantages include efficient transmission,short power transmission path and small space in need.And its unique advantages will make it possible for the electric vehicles to share a large market.There are a wide range of electric vehicles.However,applications and research on the articulated bus is relatively weak.Articulated bus has attracted enormous concern due to its large transportation volume and its handling stability is closely related to comfort and safety of passengers.Therefore,it is very necessary to analyze and design its handling stability.The articulated bus in this paper combines with the distributed drive system.There are two compartments.The front compartment owns the steering axle and one drive axle.The rear compartment owns only one drive axle.Vehicle dynamics system of the articulated vehicle is more complex than other kinds of vehicle due to the coupling function of the hitch plate.There are quite a number of concern of its dynamics which is related to vehicle stability.And the concern are similar to other vehicles more or less,including folding,rollover,flick,swing.In conclusion,study on electric articulated buses have unique meaning.This paper bases on the project “control and safety technology of multi-axle independent drive bus(2014BAG02B00)" granted by the National Science and Technology Ministry.Matlab / Simulink software was used for articulated vehicles modeling and control strategies designing,and research on handling stability.Details are listed as follows:First,after the dynamics system analysis is conducted,the vehicle model including tire model is analyzed and built which lay the foundation for the subsequent research on control strategy.Vehicle model is the basis of research on vehicle dynamics.It should be noticed that independent wheel drive articulated buses in this paper is different from the traditional fourwheel independent drive wheels and articulated buses.And there are not any software designed for independent drive articulated bus.So the vehicle model is established based on Matlab / Simulink,including linear model and complex model of three and five degree of freedom(DOF).Due to existence of magic tire formulas,it is necessary to obtain vertical load at the tire.Therefore,this paper emphasizes deduction of the whole dynamics of the vehicle to gain vertical load.Second,based on the electric articulated vehicle in this paper,multi-motor control strategy is designed.Handling stability is not only related to parameters of the vehicle system and operating condition,but also the control strategy.It is possible to control the compartments at the same time in this paper.According to its character,direct yaw moment control is chosen and the control strategy is designed,including high level controller and low level controller.The high level controller is responsible for calculation of expected yaw moment with linear quadratic regulator.And the low level controller could calculate expected motor torque according to expected yaw moment.Finally,the factors that affect handling stability and the reason why the controller improve handling stability are analyzed.In addition,the three DOF and five DOF extended model are compared to explain the necessity of experiment of five DOF extended model.The single lane change test and the step input test is carried on to verify the effect of the control strategy proposed in the paper.