Research On Longitudinal Motion Control Strategy Of Vehicle Adaptive Control Cruise System

With the rapid growth of the number of cars,the traffic environment is under great pressure and challenges.As one of the core technologies of advanced driving assistance system,vehicle adaptive cruise control(ACC)system is of great significance in reducing the driver’s control burden,improving road traffic efficiency and avoiding the incidence of part of the traffic accidents.The target acceleration decision of ACC vehicle and the modeling and optimal control strategy design of vehicle longitudinal dynamics are two key problems to be solved for improving the performance of ACC system.Considering that the existing researches are facing difficulties and deficiencies in solving constrained multi-objective cooperative control problem for vehicle longitudinal acceleration decision-making,nonlinear modeling of vehicle longitudinal dynamics and optimal control strategy design of vehicle longitudinal dynamics,the research on longitudinal motion control strategy of vehicle ACC system is proposed in this dissertation,thus a theoretical and technical basis for further improving the control performance of vehicle ACC system can be provided.Firstly,a decision-making control method for target acceleration of vehicle ACC system based on genetic algorithm optimization is proposed.The following prediction model of ACC system is established,and the acceleration decision-making multi-performance index system considering tracking,safety and fuel economy is designed.The constrained multi-objective collaborative decision-making optimal control problem of ACC vehicle based on model predictive control is then established.Finally,the genetic algorithm is introduced to optimize the solution process of the control problem.Secondly,the nonlinear mathematical model of the vehicle longitudinal dynamics system is established.By determining the specific model structure of the vehicle longitudinal dynamics system,the nonlinear dynamics analysis and modeling of the system main components,i.e.the engine,torque converter,automatic transmission,transmission system,wheel,brake system and tire are then carried out.Finally,the above subsystem models are combined,thus the overall nonlinear mathematical model of vehicle longitudinal dynamics system can be formed.Thirdly,the tire longitudinal slip control strategy based on sliding mode control algorithm is designed.The overall control structure of the ACC vehicle longitudinal dynamics based on tire slip control is determined.On this basis,the inverse model of the vehicle longitudinal dynamics is solved and the switching logic of driving and braking control is formulated.Then the tire longitudinal slip sliding mode and PID control strategies are both designed.Finally,by combining two simulation conditions,the simulation comparisons of the system control performance for the two control strategies are conducted.Finally,in order to further improve the longitudinal dynamics control performance of the ACC vehicle,the nonsingular terminal sliding mode control strategy of the tire longitudinal slip is further designed.The first task is to conduct the finite time arrival and stability analysis of the terminal sliding mode control algorithm,and the main methods which can weak the chattering phenomenon of the control algorithm are mastered.On this basis,the nonsingular terminal sliding mode control strategy of the tire longitudinal slip is further designed.Finally,based on the two simulation conditions,the performance comparison between the nonsingular terminal sliding mode control strategy and the traditional sliding mode control strategy is completed.According to the simulation results,it can be concluded that the vehicle longitudinal dynamics control performance has been further improved by adopting the nonsingular terminal sliding mode control algorithm.