| With the rapid development of automobile industry,the challenges of energy and environment become the issue that humankind is faced with.Electric vehicle(EV)is regarded as the best choice to achieve sustainable transportation development,and electric vehicle driven by in-wheel motors has been considered as the last drive layout of electric vehicle.Meanwhile,it possesses a series of remarkable advantages such as freely distribution of driving force,highly-efficient transfer of power,vehicle weight reduction,compact structure and large available space,since ignoring the traditional car transmission mechanisms.However,owing to its special power structure distribution,the unspring mass has been increased,which causes decline of ride comfort and handling stability.Traditional shock absorber dissipates the vibration energy into waste heat to ensure ride comfort and road handling.Active suspension could provide an active controllable force to improve the damping characteristics of suspension system,but the greater the energy is consumed because of external electric power input.Regenerative shock absorber has the potential to harvest the vibration energy wasted in vibration,as well as provides a controllable damping force to get a better suspension damping characteristics,which has a good development foreground.Based on the drive wheel of a electric vehicle,an electromagnetic suspension actuator has been designed which has a large stroke,high power density and low electromagnetic force ripple,theoretical model and Finite Element(FE)model considering the slot effect are built electromotive force(EMF)and the electromagnetic force characteristics are discussed.Start with no load cogging force and load wave force;electromagnetic force ripple and EMF have been optimized through the multi-objective Particle Swarm Optimization.In addition,an external electrical circuit with various load resistances is built to analysis,energy recovery and nonlinear electromagnetic force characteristics are explored based on suspension dynamic model.Finally,the resistance controller of a self-damping electromagnetic suspension is designed.The main contents are as followed:(1)An integrated electric vehicle active wheel system is designed in this paper,which mainly contains hub,in-wheel motor and regenerative suspension system.Based on the design requirement of active wheel,an external slotted mover with three-phase coils and an internal stator with permanent magnet(PM)are employed,as well as Fractional slot per pole configuration is proposed.According to the design criteria of motor and the characteristic of PM linear motor,the design scheme of electromagnetic suspension has been study,and the initial structure design parameters has been achieved,which are the bases of subsequent analysis for electromagnetic actuator.(2)Based on Maxwell field theory,the slot effect is taken into account,theoretical model and FE model of actuator with interior coils and external PMs is established using the cylindrical coordinate vectorial formulation of magnetic flux.Static analysis of magnetic field distribution and dynamic wingdings electromagnetic characteristics are carried out,transient response analysis is described as well.In addition,electromagnetic force ripple characters and time response are studied;main influencing factors of electromagnetic force ripple and response time are pointed out.(3)Based on the linear actuator structure property,the ripple of electromagnetic force principle is studied.The Influence of cogging force and end force on force ripple is discussed.The End force characteristics associated with the armature axial length and cogging force characteristics associated with slots and poles number are presented;on the other hand.In addition,using multi-objective Particle Swarm Optimization and taking structural parameters of actuator as design variables to optimize EMF amplitude and total harmonics distortion(THD)in load,the multi-objective optimization of electromagnetic has been done and optimal Pareto set has been achieved.Based on fuzzy set theory,the optimal structure parameters have been achieved.(4)Based on the optimized actuator model,a generated voltage and generated power models are established,the research about the influences of various excitation frequencies and amplitudes and initial position on generated voltage waveforms and generated power are investigated.Meanwhile,an external electrical circuit with various load resistances is built to analysis output power,generation efficiency and damping force.According to actuator analytical model,the influences of various excitation frequencies and amplitudes on damping characteristics under load condition,which will provide a theoretical basis for controller design of the electromagnetic suspension.Actuator prototype is manufactured and tested.(5)Based on the electric vehicle active wheel system electromagnetic suspension dynamic model,coupling relationship between energy recovery characteristics and ride comfort and vehicle handing is discussed,including the influences of actuator structural parameters on generated power and the influences of generated power on suspension system dynamics performance.Based on electromagnetic suspension generated voltage model,analytical damping force and test results,a semi-analytical nonlinear electromagnetic force model for electromagnetic suspension is proposed,considering magnetic saturation effect.The Influence of linear electromagnetic damping force and nonlinear electromagnetic force on vehicle dynamic performance is carried out.According to the adjustable load,an external resistance controller is built to improve the in-wheel motor drive electric vehicle performance. |
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