Performance analysis of a cooperative adaptive cruise controller subject to dynamic time headway

The current paper shows string stability of a platoon of vehicles when the spacing policy within the platoon is dynamic, i.e., it has time-varying parameters. This problem setup is to address the safety issues that arise due to malfunction of some redundant sensing/communicating devices installed on the vehicles. In such a faulty situation, the controller is still functional due to the redundancy of the sensing/communicating devices as well as estimating resources which provide the controller with the required information. However, the accuracy of the controller will be reduced. This loss of accuracy should be compensated by doing a more conservative design of safety important parameters such as the safe inter-vehicle distance, which is selected based on the string stability requirement. The decision of a change in the inter-vehicle distance, or equivalently the spacing policy, is made by a so called 'safety checker' function which can be introduced into the loop of vehicle and controller. Here, it is shown that an adopted cooperative adaptive cruise controller renders the string of vehicles stable even if the spacing policy is time variant. The stability requirement of the closed-loop system is that the switching signal suggested by the safety checker unit being piecewise constant, i.e., the safe inter-vehicle distance policy does not change continuously. © 2013 IEEE

Interaction protocols for cooperative merging and lane reduction scenarios

This paper presents the interaction protocols developed for execution of two common scenarios in daily traffic using cooperative automated vehicles. The first proposed scenario addresses merging of a (semi-)automated car on a highway within a platoon of (semi-)automated vehicles. The second scenario is an extension of the first scenario with a focus on a lane reduction where a platoon of automated vehicles merges into a second one on a different lane. The proposed interaction protocols are characterized by a sequence of maneuvers to execute the scenarios together with the corresponding communication message sets. Moreover, the vehicle control system should be equipped to implement these protocols. Therefore, the design strategy should address the interaction protocol as well as the control system design. The most important feature of the proposed design strategy is to decompose the scenarios into a sequence of basic maneuvers. This method provides a generic solution which can be implemented to other scenarios, too. Also, the thought behind the design approach is to follow the pattern that human drivers interact in similar daily traffic occasions as well as to ensure a distributed decision making mechanism where no fixed supervisor is required. In both scenarios, the platoon controllers are active to achieve the common control objective of platooning. However, for realization of the proposed scenarios, additional controllers are needed to perform the scenario-specific tasks

A Multi-Layer Control Approach to Truck Platooning : Platoon Cohesion subject to Dynamical Limitations

This paper presents a multi-layer approach to Cooperative Adaptive Cruise Control (CACC) to improve the platoon cohesion subject to limited vehicle actuation capabilities. The objective of the design is to guarantee that the vehicles in the platoon keep their desired relative position, while maintaining desirable platoon properties in terms of disturbance attenuation. To this end, a multi-layered control architecture is proposed. On the lower layer, a unidirectional CACC is employed, involving information exchange in upstream direction. On the upper layer, a coordination variable is exchanged from each vehicle towards its direct preceding vehicle, thus yielding downstream information exchange. As a result, the leading vehicle is aware of the capabilities of the following vehicles, and therefore, is able to adapt its motion, if needed. Consequently, cohesion of a heterogeneous platoon is guaranteed, even in the case of physical limitations, like engine power limits. The developed technique is verified through simulations and experiments

Artificial potential functions for control of automated vehicles

In this abstract, a nonlinear vehicle-following control strategy is presented. With a proper choice of an artificial potential function, in addition to vehicle following, other requirements in terms of a smooth gap closing and collision avoidance are embedded in the control design. The choice of a specific controller associated with the selected potential function is motivated through evaluating performance metrics. The controller which has an overall best performance in terms of these metrics is used to realize the objectives of vehicle following, gap closing, and collision avoidance in a vehicle platoon

Obstacle Avoidance Control Design: An Experimental Evaluation in Vehicle Platooning

In this paper, an obstacle avoidance controller (OA) based on the impedance control method is developed. The main goal of the OA controller is to guarantee robust gap making for a merging vehicle within a platoon of vehicles which are longitudinally automated. The proposed OA controller is developed in a simulation environment and later implemented and evaluated on test vehicles. Experimental results show the effectiveness of the proposed method for robust gap making and collision avoidance scenarios

Cooperative adaptive cruise control: an artificial potential field approach

In this paper, in addition to the main functionality of vehicle following, cooperative adaptive cruise control (CACC) is enabled with additional features of gap closing and collision avoidance. Due to its nonlinear nature, a control objective such as collision avoidance, cannot be addressed using a linear controller such as a PD controller. However, the artificial potential functions can be adopted to design controllers which accommodate multiple (nonlinear) control objectives in a single design. By defining an appropriate control law, the system state is always driven to the minima of the designed potential function which guarantees the required performance of the system