Showing papers by "Jeroen Ploeg published in 2014"

Lp String Stability of Cascaded Systems: Application to Vehicle Platooning

Abstract: Nowadays, throughput has become a limiting factor in road transport. An effective means to increase the road throughput is to employ a small intervehicle time gap using automatic vehicle-following control systems. String stability, i.e., the disturbance attenuation along the vehicle string, is considered an essential requirement for the design of those systems. However, the formal notion of string stability is not unambiguous in literature, since both stability and performance interpretations exist. Therefore, a novel definition for string stability of nonlinear cascaded systems is proposed, using input-output properties. This definition is shown to result in well-known string stability conditions for linear cascaded systems. The theoretical results are experimentally validated using a platoon of six passenger vehicles equipped with cooperative adaptive cruise control.

Controller Synthesis for String Stability of Vehicle Platoons

Abstract: Cooperative adaptive cruise control (CACC) allows for short-distance automatic vehicle following using intervehicle wireless communication in addition to onboard sensors, thereby potentially improving road throughput. In order to fulfill performance, safety, and comfort requirements, a CACC-equipped vehicle platoon should be string stable, attenuating the effect of disturbances along the vehicle string. Therefore, a controller design method is developed that allows for explicit inclusion of the string stability requirement in the controller synthesis specifications. To this end, the notion of string stability is introduced first, and conditions for L2 string stability of linear systems are presented that motivate the development of an H∞ controller synthesis approach for string stability. The potential of this approach is illustrated by its application to the design of controllers for CACC for one- and two-vehicle look-ahead communication topologies. As a result, L2 string-stable platooning strategies are obtained in both cases, also revealing that the two-vehicle look-ahead topology is particularly effective at a larger communication delay. Finally, the results are experimentally validated using a platoon of three passenger vehicles, illustrating the practical feasibility of this approach.

Cooperative adaptive cruise control: Network-aware analysis of string stability

Abstract: In this paper, we consider a Cooperative Adaptive Cruise Control (CACC) system, which regulates intervehicle distances in a vehicle string, for achieving improved traffic flow stability and throughput. Improved performance can be achieved by utilizing information exchange between vehicles through wireless communication in addition to local sensor measurements. However, wireless communication introduces network-induced imperfections, such as transmission delays, due to the limited bandwidth of the network and the fact that multiple nodes are sharing the same medium. Therefore, we approach the design of a CACC system from a Networked Control System (NCS) perspective and present an NCS modeling framework that incorporates the effect of sampling, hold, and network delays that occur due to wireless communication and sampled-data implementation of the CACC controller over this wireless link. Based on this network-aware modeling approach, we develop a technique to study the so-called string stability property of the string, in which vehicles are interconnected by a vehicle following control law and a constant time headway spacing policy. This analysis technique can be used to investigate tradeoffs between CACC performance (string stability) and network specifications (such as delays), which are essential in the multidisciplinary design of CACC controllers. Finally, we demonstrate the validity of the presented framework in practice by experiments performed with CACC-equipped prototype vehicles. cop. 2014 IEEE.

Analysis and design of controllers for cooperative and automated driving

Abstract: Nowadays, throughput has become a limiting factor in road transport. An effective means to increase the road throughput is to decrease the intervehicle time gap. A small time gap, however, may lead to string instability, being the amplification of velocity disturbances in upstream direction. String-stable behavior is thus considered an essential requirement for the design of automatic distance control systems, which are needed to allow for safe driving at time gaps well below 1 s. However, the formal notion of string stability is not unambiguous in literature, since both stability interpretations and performance interpretations exist. Therefore, a novel definition for string stability of nonlinear cascaded systems is proposed, using input–output properties. This definition is shown to result in well-known string stability conditions for linear cascaded systems. Employing these conditions, string stability is obtained by a controller that uses wireless intervehicle communication to provide information of the preceding vehicle. The theoretical results are validated by implementation of the controller, known as Cooperative Adaptive Cruise Control, on a platoon of six passenger vehicles. Experiments clearly show that the practical results match the theoretical analysis, thereby indicating the practical feasibility for short-distance vehicle following.

Lateral string stability of vehicle platoons

Abstract: This internship report is part of a larger assignment which is an analysis of lateral string stability and the development of a controller design method with guaranteed lateral string stability. Lateral string stability is an issue when a look-ahead sensing method is used in combination with a vehicle-following control strategy. The coupling between vehicles enables errors to increase while they propagate upstream through a string of vehicles. Communicating desired yaw rate or lateral acceleration and use this information for controller design could be an option to achieved guaranteed lateral string stability. One of the applications of lateral control will be conducting maneuvers like merging or lane changes. During these maneuvers the side-slip angles of the tyres stay within the interval of linear tyre response, this means that side-slip angles of the tyres are within 0:5. On this interval the non-linear and linearized tyre model have the same linear response. This makes is possible to use a linearized vehicle model with linear tyres for the modeling of the lateral and yaw dynamics of the vehicle. This is validated using experimental data and it is shown that the response of the linearized vehicle model is almost equal to the actual vehicle response.