Formation Control Of Mutiple Direct-drive Pure Electric Autonomous Vehicles Under Complex Enviroments

Compared with traditional centralized driving vehicles including internal combustion engine vehicles(ICEV)and centralized driving electric vehicles(CDEV),the driving torque coming from all the driving wheels of distributed driving electric vehicles can be controlled independently and accurately.In addition,various kinds of control strategy can be achieved based on the distributed driving electric vehicles.In recent years,considering compared with traditional vehicles,the autonomous vehicles having significant advantages in the aspect of safety,intelligentization and networking,lots of institutes including traidtioanl auto enterprises,science and techology companies and universities conduct the prospective study on the automobile-related technology.The research object of this paper is four-wheel independently driving pure electric autonomous vehicle.A new formation method named dynamic virtually leader-follower method is proposed in this paper and transform the vehicle-formation issue under complex environments into vehicle-following issue hierarchically based on the graph theory.The main work contents include the following four aspects:(1)Vehicle kinematic model and formation mathmatical model on the flat road are established.Combined with the advantages of the traditional leader-follower method and virtual strcture based method,a new formation method named dynamic virtually leader-follower method is proposed and a new formation mathematic model is established in this paper.In the end,formation control stategy based on the Lyapunov function to make sure that the following vehicle can follow the leading vehicle as requirements.(2)Seven DOFs total vehicle dynamic model of 4WIDPEV is established with some sub-model including tire and motor model.The co-simulation platform between CarSim and Simulink is built to verify the effectiveness of the above dynamic model.(3)Decoupling control strategy is adopted to transform the vehicle-formation issue into vehicle-following from longitudinal and lateral direction indepently.For the former,driving torque distributed proportionally control strategy is proposed and longitudinally vehicle-following control strategy based on fuzzy control is designed.As for the latter,considering the lateral error and heading angle error comprehensively when following the leading ones,equivalent comprehensive lareral error is proposed and fuzzy PID control algorithm is adopted to achieve the laterally vehicle-following.In the end,considering the laeral stability on the process of laterally vehicle-following under high velocity,Laterally vehicle-following and torque distribution coordination control strategy for following vehicle is proposed.(4)Considering the roll and pitch motion on the complex land,five DOFs vehicle kinematic and dynamic model are established and according to the space projection method relevant formation mathematical model is established.In the end,the number of formation vehicles are extended to more than two vehicles and formation control strategy for multiple vehicles based on the graph theory is designed to make sure that these vehicles can drive with obstacle avoidance,in addition,the formation can change the type actively according to the complexity of the surroundings based on the above control strategy.