| The damping of the semi-active suspension is adjustable,and the control technology of the semi-active suspension can effectively improve the ride comfort,safety and handling stability of the vehicle.At present,the research on semi-active suspension is mainly based on the condition of moving at a constant speed to design the controller to suppress the vibration of the vehicle body.However,there may be acceleration and deceleration conditions during the actual vehicle driving.Therefore,this paper mainly studies the control method of semi-active suspension for the acceleration and deceleration conditions of vehicles driving on flat roads,so as to restrain the excessively violent pitch motion of the vehicle body and improve the ride comfort performance on the basis of ensuring the safety and stability of the vehicle.Firstly,in order to solve the problem that most of the current vehicle models assume that the pitch center and the center of mass coincide and are only suitable for uniform speed conditions,this paper establishes a half-vehicle model with a more realistic view of the pitch center based on the analysis of the suspension structure.It can accurately characterize the pitching motion characteristics of the car during acceleration and deceleration.Then,for a magnetorheological damper model that cannot be applied to all working conditions,this paper analyzes the advantages and limitations of different modeling methods.According to the acceleration and deceleration conditions studied in this paper,the model accuracy and complexity are considered comprehensively,and the modeling method of the segmentation model is given.The semi-active suspension vehicle system established in this part lays the foundation for the subsequent simulation analysis and optimization of controller design.Secondly,in order to suppress the pitching motion of the vehicle under the acceleration and deceleration conditions of the vehicle,this paper proposes an optimal control method for the semi-active suspension based on the established vehicle system.By analyzing the influence of suspension damping on pitch angle,vertical acceleration and tire dynamic load under acceleration and deceleration conditions,the performance index of evaluating vehicle ride comfort,safety and steering stability under acceleration and deceleration conditions is designed.The multi-objective optimization control problem of the variable damper is transformed into the optimal value of the constrained nonlinear system.The genetic algorithm is used to solve the problem,and the influence of the weight on the solution result in the multi-objective optimization problem is further analyzed.In order to meet the actual demand,the result of the solution is made into an online MAP of acceleration and suspension currents.The simulation results show that the optimized controller can improve the performance of the car under the condition that the acceleration does not change drastically.However,through this open-loop optimization control method,the damping working point can only be roughly adjusted,and it cannot be adapted to all working conditions.Finally,for the problem that only the open loop optimization control can’t adapt to all working conditions,this paper designs a robust feedback controller and uses the optimization controller as a feedforward controller to propose a feedforward and feedback control strategy to ensure damping.The nonlinear constraints of force and further improve the performance of the car.Under acceleration and deceleration conditions,the operating point of the damper at different accelerations is adjusted by the optimization controller,and the robust controller adjusts around the operating point to suppress the disturbance.At the same time,in order to describe the nonlinear damping force more accurately,different constraints are designed for the feedback control amount in different dynamic stroke change rate intervals.The simulation results show that the feedforward and feedback control method can improve the performance of the car under various complicated acceleration and deceleration driving conditions. |
