| Adaptive Cruise Control System(ACC),as the main component of Advanced Driving Assistant System(ADAS),It can effectively identify the following targets in front of the vehicle in complex road environment,relieve driver fatigue and reduce the rear-end collision rate on the basis of ensuring vehicle following safety.Taking hub motor driven electric vehicle as the research object,proposed a variable shop time interval algorithm considering the speed of the vehicle and the relative speed of the two vehicles.Hierarchical control strategy was used to design the following control strategy of the adaptive cruise control system.The upper controller was designed based on the model predictive control algorithm,and the lower controller was designed based on the PID control algorithm.Matlab/Simulink and Carsim software were used to establish a co-simulation model,and simulation experiments were carried out to verify the following control strategy of the designed adaptive cruise control system.The main research contents are as follows:The working mode of adaptive cruise control system is divided into constant speed cruise mode and vehicle following cruise mode,and the switching strategy of constant speed/vehicle following cruise is proposed.On the basis of the traditional shop interval algorithm,an improved variable shop interval(VTH)algorithm was proposed.Considering the influence of the vehicle speed and the relative speed of two vehicles,two conditions were set up,including uniform and compound working conditions,and simulation experiments were conducted to verify the proposed improved variable shop interval(VTH)algorithm.The following control strategy of hierarchical adaptive cruise control system was proposed.Based on the model predictive control theory,a multi-objective optimization controller of ACC system was established,and the performance indexes and system constraints of the model predictive controller were determined.The feedback mechanism was introduced to modify the ACC system predictive model,and the relaxation factor was introduced to expand its solution feasible domain.The objective optimization problem of the system is transformed into a constrained quadratic programming problem,and the expected acceleration of the vehicle is solved.Simulation experiments are carried out to verify the following performance and response speed of the designed upper controller.The vehicle longitudinal dynamics model,inverse longitudinal dynamics model and hub motor drive EV dynamics model including hub motor model are established.Based on PID control theory,the lower controller of ACC system was designed,and the driving torque distribution strategy of hub motor was proposed to track the acceleration of the vehicle in front by ACC system and realize the following control.A C-class hatchback was selected,Matlab/Simulink and Carsim software were used to establish a co-simulation model of ACC system following control strategy,and six driving conditions including uniform speed,emergency braking,variable speed,variable acceleration,variable deceleration and urban cycle were set.Simulation experiments were carried out on the designed adaptive cruise control system.The results showed that,The following control strategy of the adaptive cruise control system proposed in this paper can achieve better speed response and tracking control and has good following performance.The research results can provide theoretical and practical basis for ACC system research. |
