Active Control And Energy Consumption Analysis Of Motor-driven Vehicle Suspensions

The vehicle suspension is one of the most important component parts which influences the performance requirements of the car.Passive suspensions cannot meet people's demand on ride comfort very well.Because of the use of actuators and control algorithms,active suspensions can achieve a great improvement on isolating passengers from vibration and shock arising from road roughness.However,there exist problems of high energy consumption,complex structure and low reliability in the active suspension system,which restricts its wide application in industrial area.The dissertation focuses on the active control and energy consumption analysis of motor-driven vehicle suspensions to realize good ride comfort and energy regeneration at the same time.The main researches are summarized as follows:From the point of energy saving,this dissertation presents a self-powered criterion of the active suspension and an energy regeneration implementation scheme.A linear DC motor is employed as the suspension actuator and energy flow in the electric circuit of the motor is analyzed.The working state of the motor is categorized into three zones based on combinations of different working states of the motor and power supply.When the motor operates in a specific zone,road vibration energy can be accumulated and transferred to electrical energy to charge the power supply.The criterion to realize a self-powered suspension is presented form the perspective of energy balance to judge whether a certain active suspension can be self-powered or not,and a motor parameter condition is given which can be referred to when selecting the DC motor to establish a self-powered suspension.An energy implementation scheme is presented to make the active suspension which has the potential to be self-powered achieve energy-saving target in the real application.In the implementation scheme,operating electric circuits are designed based on different working status of the actuator and power source and it is realizable to accumulate energy from road vibration and supply energy to the actuator by switching corresponding electric circuits.The control of active suspensions is one kind of multi-objective control problem.Ride comfort is regarded as the main performance to be optimized.Meanwhile,good road handling,the limit of suspension structure and actuator saturation are represented as time-domain constraints.To manage a trade-off between the conflicting control objective and driving behavior,a constrained H? control scheme is suggested and the state feedback controller gain is obtain by virtue of solving linear matrix inequalities(LMIs).After determining the parameters of the suspension and the DC motor,the designed active suspension has the capability to be self-powered and meet the proposed motor parameter condition.Applying the energy regeneration scheme to the constrained H? active suspension,a self-powered suspension system is achieved which is able to maintain good ride comfort and does not need an external power source.In this dissertation,a constrained adaptive backstepping control scheme is proposed for the quarter-car suspension with parameter uncertainties,in which the primary control objective is to stabilize the vertical motion of the vehicle body and in the meanwhile the suspension mechanical structure constraint can be satisfied.In terms of dealing with the hard constraint,a specific nonlinear filter is presented in order to integrate the main control objective and time-domain constraint into a single controlled variable.In addition,a barrier Lyapunov function is employed to ensure the defined controlled variable converge to zero and stay in the allowable limit,that is,the vertical motion of the vehicle body is stabilized and the suspension deflection restriction will not be transgressed.Experiments are carried out on the active suspension test plant to verify the effectiveness of the designed control scheme.The energy consumption of the active suspension plant with the proposed controller is figured out and its potential of energy recovery is demonstrated in details to provide theoretical basis for energy harvesting in further study.The self-powered suspension criterion and implementation scheme are developed by means of designing the operating circuit to realize energy regeneration.In the last chapter,energy optimized self-powered suspension realization scheme is proposed from the point of improving the control algorithm.An energy-storage device instead of a power source is employed to be connected to the actuator.When designing the energy optimized controller,a linear quadratic regulator is solved in which the quadratic performance function index includes suspension performance and active force.Meanwhile,active force and energy stored in the energy-storage device should satisfy the given constraint limits.When the energy-storage device reaches the saturation point or the stored energy reduces to its minimum,an energy management variable will change its value to guarantee the stored energy within the allowable range.In case of the energy management variable falling outside its interval,cut the connection between the actuator and energy-storage device and the suspension operates in the passive form.To simplify the algorithm,a suboptimal controller and self-powered realization scheme are given,and simulation is carried out in terms of this suboptimal control scheme.The simulation results indicate that the self-powered realization scheme is effective in improving the suspension performances and ensuring the stored energy will vary in the permissible range so that energy saving is achieved.