Feedback-based Formation Control For Autonomous Vehicles Under Connected Environment

Platoon-based driving pattern is regarded as one of effective ways to solve the transportation problems as the benefits of this driving pattern include road capacity increase,traffic congestion mitigation,and environmental pollution reduction.However,in the traditional transportation system,vehicles are independent on a road although the driver of vehicle can perceive information from the surrounding infrastructure via the visual sensor and other auxiliary sensors.Consequently,the implementation of platoon-based driving pattern is difficult under complex traffic conditions due to the limitation of relevant information.Fortunately,vehicles equipped with on-board units(OBUs),such as connected vehicles(CVs),can exchange information with the neighboring vehicles or the roadside infrastructure within the range through the vehicle-to-vehicle/vehicle-to-infrastructure(V2V/V2I)communications.This information communication technology enables the CVs to facilitate the platoon-driving pattern by considering the comprehensive information on surrounding vehicles under the connected environment.Hence,it is of important theoretical and practical significance to study the platoon control for connected autonomous vehicles(CAVs),which can provide the theoretical and experimental basis for the development of the connected autonomous transportation system.The focus of this thesis is on platoon control for CAVs.Firstly,regarding the single vehicular string with the time-invariant leader,the control protocol is designed by considering the effects of different initial states,communication delays,and communication topologies.Then,a new control protocol is further proposed under different communication topology types to address the platoon control in the case of the time-variant leader.In addition,a group consensus-based cooperative control protocol is developed by incorporating the local consensus of vehicle states for the intra-platoon and group consensus of vehicle states for the inter-platoon such as to address the issue of multi-platoon cooperation.Finally,thenumerical experiments are performed to verify the effectiveness of the proposed control protocols.The main works of this thesis are summarized as follows: 1.Regarding the single vehicular string with the time-invariant leader,a consenusbased control protocol is proposed with consideration of the longitudinal and lateral gaps simultaneously.The existing studies on platoon control mainly focus on the longitudinal control for vehicle platoon and ignore the traffic direction and non-negative velocity constraints in practice.Hence,this thesis proposes a feedback-based control protocol for the platoon control.The feedback-based protocol is designed by considering the longitudinal and lateral gaps simultaneously as well as the communication delays.Then,the stability and consensus of the proposed control protocol is analyzed using the Lyapunov technique.Effects of different initial states(e.g.initial position),communication delays(e.g.heterogeneous delays),and communication topologies(e.g.bidirectional-leader topology)on convergence and robustness of the platoon control are investigated systematically.Results from numerical experiments demonstrate the effectiveness of the proposed protocol in terms of the convergence time and robustness with respect to the position and velocity consensus.2.Regarding the scenario of the time-variant leader,a finite-time consensus-based control protocol is proposed by considering the effects of different communication topology types.Based on Section 1,a finite-time consensus-based control protocol is further proposed under different communication topology types to address the platoon control in the case of the time-variant leader.Then,the stability and consensus of the proposed protocol is analyzed using the Lyapunov technique and LaSalle's invariance principle.Also,the effects of communication topology on convergence and robustness of platoon control are investigated.Finnally,the simulation results validate the effectiveness of the proposed control protocol in terms of convergence time and robustness with respect to the position and velocity consensus.3.Regarding the multiple vehicular strings,a group consensus based cooperative control protocol is developed by incorporateing the local consensus of vehicle states for the intra-platoon and group consensus of vehicle states for the inter-platoon.The existing studies on platoon control mainly focus on the platoon control for single string and less concern the cooperative control for multiple strings.Hence,based on Sections 1 and 2,a group consensus-based cooperative control protocol is further developed by incorporating the local consensus of vehicle states for the intra-platoon and group consensus of vehicle states for the inter-platoon such as to address the issue of multi-platoon cooperation.The proposed protocol ensures that the follower vehicles can asymptotically track the leader in each string,while different vehicular strings can form a desired platoon pattern.In addition,the stability and consensus of the proposed control protocol is analyzed using the Routh stability theory and Lyapunov technique.Finally,numerical experiments are performed for two different cooperative manners,i.e.,parallel manner and serial manner.Results from numerical experiments illustrate the effects of the proposed control protocol on road throughput and verify the effectiveness of the proposed protocol with respect to the position and velocity consensus.