Vehicle Platoon Research Articles

Cooperative platoon forming strategy for connected autonomous vehicles in mixed traffic flow

Connected Autonomous Vehicle (CAV) platoon was recently proposed to improve road utilization and reduce fuel consumption. However, the mixed traffic flow of CAVs and human-driven vehicles (HDVs) will exist on the road for a long time; thus, the organization of CAVs needs to be reconsidered from the aspects of the platoon forming strategy. In this paper, a novel cooperative platoon forming (CPF) strategy is proposed to enhance the formation of CAV platoons in mixed traffic flows. A four-lane cellular automaton traffic modeling framework is constructed to simulate the interaction between CAVs and HDVs. Numerical results show that the CPF strategy is effective in enabling CAVs to be assembled into platoons. The increase in the CAV penetration rate can effectively alleviate traffic congestion and improve traffic capacity, thereby improving traffic flow and fuel economy. The findings may help improve the management of vehicle platoons.

Multi-Technology Cooperative Driving: An Analysis Based on PLEXE

Cooperative Driving requires ultra-reliable communications, and it is now clear that no single technology will ever be able to satisfy such stringent requirements, if only because active jamming can kill (almost) any wireless technology. Cooperative driving with multiple communication technologies which complement each other opens new spaces for research and development, but also poses several challenges. The work we present tackles the fallback and recovery mechanisms that the longitudinal controlling system of a platoon of vehicles can implement as a distributed system with multiple communication interfaces. We present a protocol and procedure to correctly compute the safe transition between different controlling algorithms, down to autonomous (or manual) driving when no communication is possible. To empower the study, we also develop a new version of PLEXE, which is an integral part of this contribution as the only Open Source, free simulation tool that enables the study of such systems with a modular approach, and that we deem offers the community the possibility of boosting research in this field. The results we present demonstrate the feasibility of safe fallback, but also highlight that such complex systems require careful design choices, as naive approaches can lead to instabilities or even collisions, and that such design can only be done with appropriate in-silico experiments.

Event-triggered extended state observer based distributed control of nonlinear vehicle platoons

Event-triggered extended state observer based distributed control of nonlinear vehicle platoons

Distributed Data-Driven Control for a Connected Heterogeneous Vehicle Platoon Under Quantized and Switching Topologies Communication

In this paper, a distributed data-driven control (DDC) method for a connected heterogeneous vehicle platoon under quantized and switching topologies communication is investigated. Firstly, based on the improved uniform quantizer and graph theory, the communication mode with quantized and switching topologies is designed. Then, a linearized dynamic data model named full-form dynamic linearization (FFDL) based on the input/output (I/O) data of the connected heterogeneous vehicle platoon is established, and a distributed data-driven control method is proposed. Theoretical analysis shows that the proposed DDC method can achieve uniform bounded convergence of the formation error. Finally, two numerical simulations are given based on the vehicle linearized third-order model and the vehicle longitudinal nonlinear dynamics. The simulation results are compared and analyzed, verifying the proposed algorithm's effectiveness and practicality.

Impacts of communication delay on vehicle platoon string stability and its compensation strategy: A review

Impacts of communication delay on vehicle platoon string stability and its compensation strategy: A review

VEHICLE PLATOONING SIMULATION TO AVOID COLLISION WITH PEDESTRIAN

According to a survey by the Ministry of Land, Infrastructure, Transport and Tourism, as much as 40% of the annual travel time is wasted in traffic jams. In addition, some studies have shown that the gas emitted by idling causes air pollution, and this has become a major social problem. One of the efforts to improve these problems caused by traffic congestion is the research on platooning. Most of the conventional research assumes a straight road as the experimental condition, and there is no discussion on the behavior at intersections scattered in the general roadway. In this study, a velocity control model is studied to avoid collisions with pedestrians when platoon vehicles make a turn at the intersection. A vehicle following model is defined according to Helly model which controls the vehicle acceleration according to relative speed and distance with the vehicle in front. The validity of the model is discussed from the computer simulation. Simulations were performed in some cases. The model could control the vehicles individually without collisions with pedestrians. However, these experiments were conducted only in an ideal environment by simulation. Therefore, in the future, the effectiveness of the model should be improved in actual traffic flow by conducting experiments using real vehicles.

Robust distributed model predictive control of connected vehicle platoon against DoS attacks

This paper investigates the robust distributed model predictive control (DMPC) of connected vehicle platoon (CVP) systems subject to denial-of-service (DoS) attacks. The main objective is to design a DMPC algorithm that enables the CVP system to achieve exponential tracking performance. First, a switched system model is proposed for the networked CVP system in the presence of DoS attacks. Then the sufficient conditions for the exponential stability of tracking the performance of the CVP control system under DoS attacks are obtained by constructing a specific Lyapunov function and using the topological matrix decoupling technique. In our paper, the DoS attack phenomenon is handled by introducing the frequency and duration parameters, and a quantitative relationship between the exponential decay rate of the CVP system and the DoS attacks parameters is established based on the conditions proposed in the system design, and the critical value of the DoS attack duration ratio is also derived. Finally, the effectiveness of the proposed algorithm is verified through a simulation of a CVP system consisting of one leading vehicle and three following vehicles.

Tracking consensus for uncertain nonlinear multi‐agent systems under cloud‐based event‐triggered coordination

AbstractThis paper considers the cloud‐based event‐triggered coordination problem of uncertain high‐order nonlinear multi‐agent systems. The communication among agents is realized by indirect and asynchronous access to a shared cloud database. A self‐triggered extended state observer (ESO) is first designed to estimate the total uncertainty. Based on the output of the ESO, an event‐triggered controller is proposed. It is proved that under the proposed output feedback controller, the multi‐agent system can track a virtual leader. We also show that Zeno behavior from output sampling or controller update will never happen. Finally, a numerical example and a vehicle platoon example are provided to corroborate the obtained theoretical results.

Coordinated control of longitudinal and lateral movements considering dynamics for distributed drive electric vehicle platoon on curved roads

The control goal of the vehicle platoon is to maintain the same speed and desired distance. Most current studies are based on simplified vehicle models, and the leader’s state is also rarely considered. However, under complex working conditions, such as low adhesion or curves, the lateral stability of the platoon will be difficult to guarantee, and tracking errors of desired speed and spacing may further increase. To solve the above problems, a new hierarchical coordinated control strategy is proposed. Taking distributed drive electric vehicles (DDEVs) as research objects, the upper control level establishes a stability situation assessment model according to the vehicle’s dynamic characteristics. At the medium control level, variable weight model predictive control (MPC) coordinates conflicts between longitudinal tracking and lateral stability. A correction term is also introduced to revise the prediction model. At the same time, the weight of different control objectives of the leader and following vehicle was adjusted, respectively. Torque distribution is carried out at the lower level controller. Finally, the control strategy is tested on a hardware-in-the-loop (HIL) platform. The results show that the proposed control strategy can ensure lateral stability while improving the tracking performance of the vehicle platoon.

Eco-CSAS: A Safe and Eco-Friendly Speed Advisory System for Autonomous Vehicle Platoon Using Consortium Blockchain

Future worldwide 6G research will drive the evolution of emerging intelligent control technologies, such as intelligent speed advisory systems (ISA), to a more advanced generation. As a special type of ISA, consensus-based speed advisory systems (CSAS) can be widely used to recommend a consensus speed for a vehicle platoon, enabling minimizing energy consumption or emissions over a planned route. Recently, speed recommendation services that protect data privacy (i.e., how to obtain an optimal speed in a privacy-preserving way) have drawn tremendous attention. However, current approaches could still encounter service trust issues with central servers and the malicious behavior of vehicles. Furthermore, existing research lacks considering road safety constraints (i.e., safe distance between adjacent vehicles and road speed limits) that are essential for the practical deployment of CSAS. To address the above issues, this paper proposes Eco-CSAS, a safe and eco-friendly consensus speed advisory system using blockchain. We formulate an optimization problem subject to the minimum following distance and maximum road speed limit to minimize the energy consumption of the automatic vehicle platoon. In addition, we introduce a consortium blockchain and cryptographic primitives to ensure service trust and data privacy. We implement the system on the Hyperledger platform, and experimental results show that the system can achieve speed recommendations in a trustworthy and privacy-preserving manner while ensuring a secure platoon.

The Upper Bounds of Cellular Vehicle-to-Vehicle Communication Latency for Platoon-Based Autonomous Driving

Cellular vehicle-to-vehicle (V2V) communications can support advanced cooperative driving applications such as vehicle platooning and extended sensing. As the safety critical applications require ultra-low communication latency and deterministic service guarantee, it is vital to characterize the latency upper bound of cellular V2V communications. However, the contention-based Medium Access Control (MAC) and dynamic vehicular network topology brings many challenges to model the upper bound of cellular V2V communication latency and assess the link capability for quality of service (QoS) guarantee. In this paper, we are motivated to reduce the research gap by modelling the latency upper bound of cellular V2V with network calculus. Based on the theoretical model, the probability distribution of the delay upper bound can be obtained under the given task features and environment conditions. Moreover, we propose an intelligent scheme to reduce upper bound of end-to-end latency in vehicular platoon scenario by adaptively adjusting the V2V communication parameters. In the proposed scheme, a deep reinforcement learning model is trained and implemented to control the time slot selection probability and the number of time slots in each frame. The proposed approaches and the V2V latency upper bound are evaluated by simulation experiments. Simulation results indicate that our network calculus based analytical approach is effective in terms of the latency upper bound estimations. In addition, with fast iterative convergence, the proposed intelligent scheme can significantly reduce the latency by about 80% compared with the conventional V2V communication protocols.

Secure Data Sharing With Flexible Cross-Domain Authorization in Autonomous Vehicle Systems

As an increasingly prevalent technology in intelligent autonomous transportation systems, autonomous vehicle platoon has been indicated the ability to significantly reduce fuel consumption as well as heighten highway safety and throughput. However, existing efforts rarely focus on protecting data confidentiality and authenticity in autonomous vehicle platoons. How to ensure secure and high-fidelity platoon-level communication is still in its infancy. This paper makes the first attempt for efficient and secure communication across autonomous vehicle platoons. Specifically, we present PDSM-FC, the first privacy-preserving data share mechanism with flexible cross-domain authorization over distinctive platoons. The key insight of PDSM-FC is the design of a new ciphertext conversion technique, which allows a ciphertext to be easily converted into another type of ciphertext, facilitating efficient access by all entities holding the legitimate authorization. As a result, PDSM-FC can achieve high-fidelity data communication between two unique platoons in ciphertext, so as to complete specific tasks including platoon integration. Rigorous security analysis shows that PDSM-FC is secure against various attacks such as collusion, forgery and chosen-plaintext attacks. Moreover, theoretical evaluation and extensive experiments demonstrate the practicability of PDSM-FC in terms of functionality, storage and computation overheads.

Data-Driven Dynamic Event-Triggered Fault-Tolerant Platooning Control

This paper addresses the dynamic event-triggered (DET) fault-tolerant model-free adaptive platooning control (MFAPC) problem of vehicle platoon systems subject to sensor faults. First of all, a novel redefined output is introduced to assist in proving the synchronous tracking of the position and velocity. Based on which, the equivalent dynamic linearization technique is used for transforming the nonlinear vehicular platooning systems into an linear data model. Then, an observer is designed to introduce the estimation of the pseudo-partial derivative (PPD) parameter, which can also eliminate the symbol restriction on it. In addition, a DET mechanism is introduced to save network resources more effectively, and the neural network method is applied to deal with the sensor faults for the safe vehicle driving. Further, a novel DET-based fault-tolerant MFAPC strategy is developed to realize the vehicular position and velocity tracking only using the input-output data. At last, an example is provided to prove the effectiveness of designed MFAPC framework.

Communication delay-aware cooperative adaptive cruise control with dynamic network topologies-a convergence of communication and control

Wireless communication-enabled Cooperative Adaptive Cruise Control (CACC) is expected to improve the safety and traffic capacity of vehicle platoons. Existing CACC considers a conventional communication delay with fixed Vehicular Communication Network (VCN) topologies. However, when the network is under attack, the communication delay may be much higher, and the stability of the system may not be guaranteed. This paper proposes a novel communication Delay Aware CACC with Dynamic Network Topologies (DADNT). The main idea is that for various communication delays, in order to maximize the traffic capacity while guaranteeing stability and minimizing the following error, the CACC should dynamically adjust the VCN network topology to achieve the minimum inter-vehicle spacing. To this end, a multi-objective optimization problem is formulated, and a 3-step Divide-And-Conquer sub-optimal solution (3DAC) is proposed. Simulation results show that with 3DAC, the proposed DADNT with CACC can reduce the inter-vehicle spacing by 5%, 10%, and 14%, respectively, compared with the traditional CACC with fixed one-vehicle, two-vehicle, and three-vehicle look-ahead network topologies, thereby improving the traffic efficiency.

On the Relationship between Traffic Hysteresis and String Stability of Vehicle Platoons

On the Relationship between Traffic Hysteresis and String Stability of Vehicle Platoons

Cooperative Lane-Change Motion Planning for Connected and Automated Vehicle Platoons in Multi-Lane Scenarios

Multi-vehicle motion planning (MVMP) has become an emerging paradigm in connected and automated vehicles (CAVs). The cooperative lane-change movements with the coexistence of platoons and CAVs are typical scenarios on the muti-lane roads. This paper proposes an optimal control framework with the advantages of completeness and universality for platoons and CAVs’ cooperative lane-change motion planning in different task scenarios. Two typical cooperative scenarios are designed for the subsequent study of optimal modeling. The platoons’ reconfiguration and original shape maintenance are considered to reflect the universality of moving objects and the diversity of cooperative tasks. Approximately geometric contour models, dynamic externally tangent rectangle and inflated rectangle, are utilized to describe the platoon’s profile. Analytical complete collision avoidance constraints among different motion objects are constructed effectively. Other necessary constraints and the weighted cost function that minimizes lane-change time and motion energy are comprehensively considered. The optimal control models are established for the desired scenarios. Moreover, a numerical solution method combined with the simultaneous direct collocation method based on the trapezoidal rule and the barrier function method is proposed to obtain the optimal schemes. Simulation and contrast experiments are conducted for two scenarios. The results indicate that the cost function’s weight coefficients and specific lane-change tasks influence the cooperative motion planning effects and verify that the proposed optimal control framework is of reasonability, effectiveness, and unification.

On Connected Autonomous Vehicles With Unknown Human Driven Vehicles Effects Using Transmissibility Operators

This study proposes an algorithm for fault detection and mitigation of mixed autonomous and human-driven vehicle platoons based on transmissibility identification. This work is motivated by the fact that on-road human-drivers&#x2019; behaviour is unknown and difficult to be predicted. Transmissibility operators are mathematical operators that relate one subset of outputs to another in the same system. The transmissibility superiority is represented in the in-dependency on the system excitation signals. We reformulate the system dynamics to render the system inputs, external disturbances, as well as the human-drivers&#x2019; behaviour along with any other nonlinearities as independent excitation signals on the system. Therefore, the transmissibility operators become independent of the human-drivers&#x2019; behaviour and robust against external disturbances. Transmissibilities are then applied to detect and localize physical and cyber faults within the platoon. Then these faults are mitigated using a transmissibility-based sliding mode controller. The controller stability and the string stability are investigated while the controller is active and the faults are mitigated. We validate the proposed algorithm on a model of the platoon obtained using the bond graph approach. Moreover, we apply the proposed algorithm experimentally to a platoon consisting of three robots (i.e. two autonomous robots and a human-driven robot), that is connected using wireless communications. <i>Note to Practitioners</i>&#x2014;The existence of connected autonomous vehicles depends greatly on the smooth transition between the current on-road human-driven vehicles to autonomous vehicles. The typical methods of securing dynamic systems depend on estimating the system behaviour and responses. Increasing the number of autonomous vehicles on roads necessitates the typical securing techniques to estimate the human-drivers&#x2019; behaviour. Thus, securing the connected autonomous vehicles during this transition is challenging since the on-road human-driver behavior is unknown and difficult to be estimated. Moreover, connected autonomous vehicles should adapt to their environment while maintaining their role within the autonomous platoon. This adaptation includes adapting to the unknown human-driver behaviour. This inspired the authors to develop the proposed transmissibility-based fault mitigation. The proposed technique is shown to be able to handle unknown human-driver behaviors, different driving conditions such as road irregularities and different weather conditions, and different physical and cyber faults (i.e., in the vehicles or in the communication links). The platoon stability is then investigated while the faults are mitigated, and shown to guarantee the platoon stability.

Study of the Flow Characteristics Due to the Effect of Offsetting in Platoon of Sport Utility Vehicles

Study of the Flow Characteristics Due to the Effect of Offsetting in Platoon of Sport Utility Vehicles

An extendable maneuver management framework with fault‐tolerant mechanism for vehicle platoon control system in highway scenario

AbstractVehicle platoons can encounter many complex scenarios in practice that were not considered in the design, which reveals the need to add new maneuvers. Platoon control system will face the challenge of the lack of maneuver scalability in practical applications. To address this problem, this study introduces an extendable maneuver management framework with fault‐tolerant mechanism on the basis of the hierarchical architecture for the platoon control system. Maneuvers and roles are two dimensions, based on which the management strategies are decoupled. They enable each vehicle in the platoon to execute management strategies of various maneuvers and make it possible to expanding new behaviors into existing strategies. The fault‐tolerant mechanism is designed as a maneuver triggered by hardware failures to remain safe before taking over. Furthermore, three typical maneuvers are selected for case studies to illustrate the management strategies in this framework. Finally, a comprehensive simulation scenario integrating different maneuvers is designed and a real‐world implementation using micro‐vehicles is conducted. The results demonstrate that the proposed two‐dimensional framework could effectively address various maneuvers and satisfy the computational real‐time requirements.

Exploring the Role of Sampling Time in String Stabilization for Platooning: An Experimental Case Study

In this article, we investigate the behavior of vehicle platoons operating in a predecessor-following configuration, implemented through sampled-data control systems. Our primary focus is to examine the potential influence of the sampling time on the string stability of the platoon. To address this, we begin by designing a string-stable platoon in continuous time. Subsequently, we consider the controller discretization process and proceed to simulate and implement the designed control strategy on an experimental platform at a scaled-down level. Through experimental testing and some theoretical results, we analyze the effects of different sampling times on the string stability performance of the platoon. We observe that an inappropriate selection of the sampling time can lead to a degradation in string stability within the platoon, making the choice of the sampling time crucial in maintaining the desired string stability properties. These findings highlight the importance of carefully considering the sampling time in the implementation of control systems for platooning applications.