Toward a Comprehensive Impossibility Result for String Stability

Farnam, Arash; Sarlette, Alain

doi:10.1109/tac.2019.2929967

Cited by 9 publications

(5 citation statements)

References 20 publications

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“…Theorem 1 for any h > 0 seems to contradict known results about string instability of ACC [21], [22], [23], [24]: however, such results use h = 0. Meanwhile, as some literature reports string instability of ACC for small h [4], [25], [26], let us remark that there is no contradiction as well: there, a different ACC control law with less degrees of freedom is adopted…”

Section: Remark 3 (String Stable Acc) String Stability Of Acc Inmentioning

confidence: 59%

Collision Avoidance in Longitudinal Platooning: Graceful Degradation and Adaptive Designs

Liu

Baldi

Hirche

2023

IEEE Control Syst. Lett.

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An externally positive system has the property of giving a nonnegative output for any nonnegative input. By making the inter-vehicle spacing a nonnegative output, this system property is significant for collision avoidance in platooning. Yet, existing platooning results based on external positivity just apply to adaptive cruise control (ACC): as ACC uses on-board sensing only, these results do not apply when onboard sensing is integrated with inter-vehicle communication, as in cooperative adaptive cruise control (CACC). This work provides an integrated external positivity design for CACC. When unreliable communication requires transitions between CACC and ACC, the design still guarantees graceful degradation in terms of collision avoidance and disturbance rejection. Such graceful transitions can be attained also in the presence of vehicle parameter uncertainty, via a suitable adaptive control design.

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Section: Remark 3 (String Stable Acc) String Stability Of Acc Inmentioning

confidence: 59%

Collision Avoidance in Longitudinal Platooning: Graceful Degradation and Adaptive Designs

Liu

Baldi

Hirche

2023

IEEE Control Syst. Lett.

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“…, 1, let F i be given by (17). Define a 3 × 3(N + 1) matrix by (20), shown at the bottom of the next page.…”

Section: String Stabilizing Automated Vehiclementioning

confidence: 99%

“…Recent results include a delay-based spacing policy [12], modeling automated vehicles by partial differential equations [13], and dealing with heterogeneity in vehicle dynamics [14]- [18]. Limitations or impossibility of string stability in the absence of communication was studied both theoretically [19], [20] and experimentally [21].…”

mentioning

confidence: 99%

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

Liu

Besselink

Baldi

et al. 2023

IEEE Trans. Intell. Transport. Syst.

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The interaction between automated and humandriven vehicles in mixed (human/automated) platoons is far from understood. To study this interaction, the notion of headto-tail string stability was proposed in the literature. Headto-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 headto-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.

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“…Notably, utilizing a time-gap policy based on absolute velocity allows to achieve string stability, compare remark in [39]. Such a policy aims to track an inter-vehicle distance of h •v which is the distance covered by the ego vehicle at constant current ego velocity v over a time span of duration h. The position error is therefore defined as…”

Section: Vehicle Modelmentioning

confidence: 99%

String Stable and Collision-Safe Model Predictive Platoon Control

Gratzer

Thormann

Schirrer

et al. 2022

IEEE Trans. Intell. Transport. Syst.

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Automated vehicle platooning bears high potential to increase traffic efficiency, improve road safety, and reduce fuel consumption. To realize platoons with small inter-vehicle distances, collision safety is the most crucial concern and needs to be considered carefully. Moreover, it is desired to attenuate disturbances along the platoon which is known as string stability. While model predictive control concepts achieve efficient, situation-aware, and safe platooning, establishing string stability properties is difficult. In this work string stability is characterized for a generic feedback setting. A workflow to design an extended time gap spacing policy is proposed for a safety-extended distributed model predictive platooning controller. It provides safe, tightly-packed platoon operation with robust string stability near steady-state even without vehicleto-vehicle-V2V-communication. Platoon performance is further improved by exploiting V2V-communication. Finally, the resulting closed-loop platoon dynamics are validated in a high-fidelity co-simulation study.

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Toward a Comprehensive Impossibility Result for String Stability

Cited by 9 publications

References 20 publications

Collision Avoidance in Longitudinal Platooning: Graceful Degradation and Adaptive Designs

Collision Avoidance in Longitudinal Platooning: Graceful Degradation and Adaptive Designs

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

String Stable and Collision-Safe Model Predictive Platoon Control

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