Control Of Regenerative Braking Systems For The Four-wheel Independently Actuated Electric Vehicles

The environmental pollution has become extremely serious with the number of traditional vehicles increasing,therefore,the new energy vehicles have aroused widespread attention all over the world.Electric vehicles are powered by energy storage equipment and have several advantages in terms of small noise and environmental friendliness.Among all types of electric vehicles,the four-wheel independently actuated electric vehicle(FWIA-EV)with in-wheel motor is one of the most prospective electric vehicles.The control of regenerative braking systems for FWIA-EVs consists of the vehicle states estimation and the feedback controller design.In this thesis,the following parts will be researched:(1)The modeling and analysis of vehicles:Firstly,the modeling of the tire-road friction forces is presented.The tire model utilized in this thesis is the Dugoff’s tire model,and the relationship between the tire friction forces and the vehicle states is analyzed.Secondly,the modeling of the ve-hicle is given by ignoring the road grade and the bank angle.Finally,the wheel dynamics equation is presented,and the relationship between tire friction forces and braking torques is analyzed.(2)Design of the vehicle modular observer:Based on the tire friction force model and the vehicle dynamics equation,a modular observer is proposed to estimate vehicle velocities.The modular observer consists of the longitudinal tire forces estimation and the velocities estimation.Firstly,the longitudinal tire forces estimation is proposed according to the analysis of wheel dy-namics,and the input-to-state stability theory is utilized to demonstrate the convergence of the observer.Then,on the basis of the estimation value of the longitudinal tire forces,the design of vehicle velocities observer is proposed,and the Lyapunov stability theory is utilized to prove that the estimation error is uniformly bounded.(3)Design of the regenerative braking system controller:A hierarchical controller is proposed to track the desired velocity of drivers and to improve the energy recovery of vehicles when the vehicle is under straight-line braking maneuvers.The hierarchical strategy consists of the upper layer sliding mode controller and the lower layer optimization algorithm.Then the CarSim is utilized to validate the performance of the hierarchical controller.The energy recovery performance is compared with another strategy and the simulation results show the improvement of energy recovery.