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In this paper we investigate the effects of connected automated vehicles on traffic patterns. We first experimentally study traffic patterns using two connected human-driven vehicles, which are equipped with vehicle-to-vehicle (V2V) communication, and a connected automated vehicle, which is able to respond to V2V information and control its longitudinal motion. Our experimental results indicate the long-range feedback may benefit traffic flow and that car-following models with delay are able to replicate the experimental results. The data fitted models are used in simulations for a 100-car network to study traffic dynamics with partial penetration of connected automated vehicles. [ABSTRACT FROM AUTHOR]

In this paper, we present a systematic approach for fuel-economy optimization of a connected automated truck that utilizes motion information from multiple vehicles ahead via vehicle-to-vehicle (V2V) communication. Position and velocity data collected from a chain of human-driven vehicles are utilized to design a connected cruise controller that smoothly responds to traffic perturbations while maximizing energy efficiency. The proposed design is evaluated using a high-fidelity truck model and the robustness of the design is validated on real traffic data sets. It is shown that optimally utilizing V2V connectivity leads to around 10% fuel economy improvements compared to the best nonconnected design. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the performance of communication-based controller design in connected vehicle networks. A testbed consisting of a group of ground robots that can mimic the dynamics of personal vehicles is built. We show that when incorporating time delays in the modeling equations, which arise due to digital implementation and intermittent vehicle-to-vehicle (V2V) communication, the experimental results have a very good correspondence with the theoretical ones. Moreover, we demonstrate that by designing a controller for each individual vehicle in the chain plant stability and string stability can be guaranteed despite the time delays in the control loop. Then, a series of experiments is conducted for a mixture of string stable and string unstable vehicles and the effects of penetration rate of string stable vehicles in maintaining smooth traffic are evaluated. The results lay a foundation for connected vehicle system design with flexible connectivity topologies. [ABSTRACT FROM AUTHOR]

This paper presents the robustness analysis for the head-to-tail string stability of connected cruise controllers that utilize motion information of human-driven vehicles ahead. In particular, we consider uncertainties arising from the feedback gains and reaction time delays of the human drivers. We utilize the linear fractional transformation and the $M$ - $\Delta$ uncertain interconnection structure to represent the uncertainties in the block-diagonal matrix $\Delta$. The uncertain gains are directly incorporated in the uncertain interconnection structure, while the uncertain time delays are taken into account using the Rekasius substitution that preserves the tightness of the robustness bounds. This modeling framework scales are well for large-size connected vehicle systems. We demonstrate through two case studies how parameters in the connected cruise controller can be selected to ensure the robust string stability. Theoretical results are supported by the experiments that highlight the advantage of robust control designs. [ABSTRACT FROM AUTHOR]

In this paper, we investigate experimentally the impact of connected automated vehicles on the dynamics of vehicle chains with different connectivity topologies. We utilize a scaled connected vehicle testbed consisting of ground robots that can mimic the dynamics of human-driven and connected automated vehicles. We derive analytical conditions for stability and disturbance attenuation (i.e., string stability) while taking into account digital effects and delays and validate the corresponding stability diagrams experimentally. The flexibility and robustness of vehicle-to-everything (V2X) based longitudinal control among human-driven vehicles is evaluated for different connectivity topologies and the impacts of connected automated vehicles on traffic flow are highlighted. [ABSTRACT FROM AUTHOR]

In this paper, we present a systematic design framework for gear shift schedule using hybrid system theory primarily intended for automated vehicles. The longitudinal motion of the vehicle is regulated by a PI controller that determines the required axle torque. The longitudinal dynamics of the vehicle with a gear box is modeled as a hybrid system, and an optimization-based gear shift schedule design is introduced. This guarantees that the propulsion requirements are delivered while minimizing fuel consumption. The resulting dynamics is proven to be stable in the presence of constraints. We apply our framework to heavy-duty vehicle gear shift schedule design and evaluate the performance of the controller using numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the identification of the configuration and the dynamics of connected vehicle systems, where wireless vehicle-to-vehicle communication is used to access the motion data of vehicles that are beyond the line of sight. In particular, we first construct a causality detector to determine whether the information received from distant vehicles is relevant to the motion of the receiving vehicle. Then, we design a link-length estimator to identify the number of vehicles between the broadcasting vehicle and the receiving vehicle, which is required for appropriately incorporating the received data into the vehicle control system. Finally, a dynamics identifier is proposed to approximate the nonlinear time-delayed dynamics of vehicle chains, which is needed for the controller design to achieve desired system-level performance. The presented analytical results are validated through numerical simulations using synthetic data and on-road experiments. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a vehicular string traveling on a single lane, where vehicles use connected cruise control to regulate their longitudinal motion based on data received from other vehicles via wireless vehicle-to-vehicle communication. Assuming digital controllers, the sample-and-hold units introduce time-periodic time delays in the control loops and the delays increase when data packets are lost. We investigate the effect of packet losses on plant and string stability while varying the control gains and determine the minimum achievable time gap below which stability cannot be achieved. We propose two predictor feedback control strategies that overcome the destabilizing effect of the time delay caused by the sample-and-hold unit and packet losses. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate the design of connected cruise control that exploits wireless vehicle-to-vehicle communication to enhance vehicle mobility and safety. A hierarchical framework is used to reduce the complexity for design and analysis. A high-level controller incorporates the motion data received from multiple vehicles ahead and also considers information delays, in order to generate the desired longitudinal dynamics. At the lower level, we consider a physics-based vehicle model and design an adaptive sliding-mode controller that regulates the engine torque, so that the vehicle can track the desired dynamics in the presence of uncertainties and external perturbations. Numerical simulations are used to validate the analytical results and demonstrate the robustness of the controller. [ABSTRACT FROM AUTHOR]

In this paper, linear quadratic regulation is used to obtain an optimal design of connected cruise control (CCC). We consider vehicle strings where a CCC vehicle receives position and velocity signals through wireless vehicle-to-vehicle communication from multiple vehicles ahead. Communication delay, driver reaction time, and heterogeneity of vehicles are considered. The optimal feedback law is obtained by minimizing a cost function defined by headway and velocity errors and the acceleration of the CCC vehicle on an infinite horizon. We show that, by decomposing the optimization problem, the feedback gains can be obtained recursively as signals from vehicles farther ahead become available, and that the gains decay exponentially with the number of cars between the source of the signal and the CCC vehicle. Such properties allow graceful degradation of CCC performance under imperfect communication. The effects of the cost function on the head-to-tail string stability are also investigated and the robustness against variations in human parameters is tested. The analytical results are verified by numerical simulations at the nonlinear level. The results allow us to significantly reduce the complexity of CCC design. [ABSTRACT FROM PUBLISHER]

In this paper we investigate connected cruise control in which vehicles rely on ad hoc wireless vehicle-to-vehicle communication to control their longitudinal motion. Intermittencies and packet drops in communication channels are shown to introduce stochastic delays in the feedback loops. Sufficient conditions for almost sure stability of equilibria are derived by analyzing the mean and covariance dynamics. In addition, the concept of $n\sigma$ string stability is proposed to characterize the input–output response in steady state. The stability results are summarized using stability charts in the plane of the control gains and we demonstrate that the stable regimes shrink when the sampling time or the packet drop ratio increases. The mathematical tools developed allow us to design controllers that can achieve plant stability and string stability in connected vehicle systems despite the presence of stochastically varying delays in the control loop. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate the effects of heterogeneous connectivity structures and information delays on the dynamics of connected vehicle systems (CVSs), which are composed of vehicles equipped with connected cruise control (CCC) as well as conventional vehicles. First, a general framework is presented for CCC design that incorporates information delays and allows a large variety of connectivity structures. Then, we present delay-dependent criteria for plant stability and head-to-tail string stability of CVSs. The stability conditions are visualized by using stability diagrams, which allow one to evaluate the robustness of vehicle networks against information delays. To achieve modular and scalable design of large networks, we also propose a motif-based approach. Our results demonstrate the advantages of CCC vehicles in improving traffic efficiency, but also show that increasing the penetration of CCC vehicles does not necessarily improve the robustness if the connectivity structure or the control gains are not appropriately designed. [ABSTRACT FROM PUBLISHER]