A minimal sensing and communication control strategy for adaptive platooning

Several cooperative driving strategies proposed in literature, sometimes known as cooperative adaptive cruise control strategies, assume that both relative spacing and relative velocity with preceding vehicle are available from on-board sensors (laser or radar). Alternatively, these strategies assume communication of both velocity states and acceleration inputs from preceding vehicle. However, in practice, on-board sensors can only measure relative spacing with preceding vehicle (since getting relative velocity requires additional filtering algorithms); also, reducing the number of variables communicated from preceding vehicle is crucial to save bandwidth. In this work we show that, after framing the cooperative driving task as a distributed model reference adaptive control problem, the platooning task can be achieved in a minimal sensing and communication scenario, that is, by removing relative velocity measurements with preceding vehicle and by removing communication from preceding vehicle of velocity states. In the framework we propose, vehicle parametric uncertainty is taken into account by appropriately designed adaptive laws. The proposed framework is illustrated and shown to be flexible to several standard architectures used in cooperative driving (one-vehicle look-ahead topology, leader-to-all topology, multivehicle look-ahead topology)

Stability and String Stability Analysis of Formation Control Architectures for Platooning.

This thesis presents theoretical results for stability and string stability of formation control architectures for platooning. We consider three important interconnection topologies for vehicles travelling in a straight line as a string: leader following, cyclic and bidirectional. For the leader following topology we discuss modifications that allow reduced coordination requirements. In the first case we consider the use of the leader velocity as the state to be broadcast to the followers, rather than the standard use of the leader position. This selection yields a formation control architecture that achieves string stability even under time delays in the state broadcast, while reducing typical coordination requirements of leader following architectures. For the second modification we change the way in which the leader position is sent across the string to every follower. This technique keeps some of the good transient properties of the standard leader following architecture but eliminates most of the coordination requirements for the followers. However, we show that this technique does not provide string stability when time delays are present in the communication. The second topology that we discuss is a cyclic one, where the first member of the platoon is forced to track the last one. We discuss two strategies: one where the inter-vehicle spacings may follow a constanttime headway spacing policy and one where an independent leader broadcasts its position to every member of a cyclic platoon. For both strategies we obtain closed form expressions for the transfer functions from disturbances to inter-vehicle spacings. These expressions allow us to show that if the design parameters are not properly chosen, the vehicle platoon may become unstable when the string size is greater than a critical number. On the contrary, if the design parameters are well chosen, both architectures can be made stable and string stable for any size of the platoon. The final topology that we consider is bidirectional, where every member of the platoon, with the exception of the first and last, use measurements of the two nearest neighbours to control their position within the string. Although the derivations are more complex than in the two previous unidirectional cases, we obtain closed form epressions for the dynamics of the platoon. These expressions are in the form of simple transfer functions from disturbances to vehicles. They allow us to obtain stability results for any size of the platoon and understand the behaviour of the least stable pole location as the string size increases. All of the results obtained are illustrated by numerical examples and ad-hoc simulations

Stability and String Stability Analysis of Formation Control Architectures for Platooning.

This thesis presents theoretical results for stability and string stability of formation control architectures for platooning. We consider three important interconnection topologies for vehicles travelling in a straight line as a string: leader following, cyclic and bidirectional. For the leader following topology we discuss modifications that allow reduced coordination requirements. In the first case we consider the use of the leader velocity as the state to be broadcast to the followers, rather than the standard use of the leader position. This selection yields a formation control architecture that achieves string stability even under time delays in the state broadcast, while reducing typical coordination requirements of leader following architectures. For the second modification we change the way in which the leader position is sent across the string to every follower. This technique keeps some of the good transient properties of the standard leader following architecture but eliminates most of the coordination requirements for the followers. However, we show that this technique does not provide string stability when time delays are present in the communication. The second topology that we discuss is a cyclic one, where the first member of the platoon is forced to track the last one. We discuss two strategies: one where the inter-vehicle spacings may follow a constanttime headway spacing policy and one where an independent leader broadcasts its position to every member of a cyclic platoon. For both strategies we obtain closed form expressions for the transfer functions from disturbances to inter-vehicle spacings. These expressions allow us to show that if the design parameters are not properly chosen, the vehicle platoon may become unstable when the string size is greater than a critical number. On the contrary, if the design parameters are well chosen, both architectures can be made stable and string stable for any size of the platoon. The final topology that we consider is bidirectional, where every member of the platoon, with the exception of the first and last, use measurements of the two nearest neighbours to control their position within the string. Although the derivations are more complex than in the two previous unidirectional cases, we obtain closed form epressions for the dynamics of the platoon. These expressions are in the form of simple transfer functions from disturbances to vehicles. They allow us to obtain stability results for any size of the platoon and understand the behaviour of the least stable pole location as the string size increases. All of the results obtained are illustrated by numerical examples and ad-hoc simulations

On Structural and Safety Properties of Head-to-Tail String Stability in Mixed Platoons

The interaction between automated and human-driven vehicles in mixed (human/automated) platoons is far from understood. To study this interaction, the notion of head-to-tail string stability was proposed in the literature. Head-to-tail string stability is an extension of the standard string stability concept where, instead of asking every vehicle to achieve string stability, a lack of string stability is allowed due to human drivers, provided it can be suitably compensated by automated vehicles sparsely inserted in the platoon. This work introduces a theoretical framework for the problem of head-to-tail string stability of mixed platoons: it discusses a suitable vehicle-following human driver model to study mixed platoons, and it gives a reduced-order design strategy for head-to-tail string stability only depending on three gains. The work further discusses the safety limitations of the head-to-tail string stability notion, and it shows that safety improvements can be attained by an appropriate reduced-order design strategy only depending on two additional gains. To validate the effectiveness of the design, linear and nonlinear simulations show that the string stability/safety trade-offs of the proposed reduced-order design are comparable with those resulting from full-order designs.</p

Multibody dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: Formulations and Numerical Methods, Efficient Methods and Real-Time Applications, Flexible Multibody Dynamics, Contact Dynamics and Constraints, Multiphysics and Coupled Problems, Control and Optimization, Software Development and Computer Technology, Aerospace and Maritime Applications, Biomechanics, Railroad Vehicle Dynamics, Road Vehicle Dynamics, Robotics, Benchmark Problems. The conference is organized by the Department of Mechanical Engineering of the Universitat Politècnica de Catalunya (UPC) in Barcelona. The organizers would like to thank the authors for submitting their contributions, the keynote lecturers for accepting the invitation and for the quality of their talks, the awards and scientific committees for their support to the organization of the conference, and finally the topic organizers for reviewing all extended abstracts and selecting the awards nominees.Postprint (published version

Bibliography of Lewis Research Center technical publications announced in 1993

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1993. All the publications were announced in the 1993 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses