- The paper proposes a novel delay-based spacing policy incorporating a time-delay to track spatially varying reference velocity profiles, beneficial for vehicles on variable terrain.
- It introduces "disturbance string stability," a new definition that explicitly accounts for external disturbances affecting all vehicles in a platoon, not just the leader.
- Numerical results confirm the delay-based policy effectively maintains string stability and uniform velocity error bounds under disturbances, showing spacing policy is key.
String Stability and Delay-Based Spacing Policy for Vehicle Platoons Subject to Disturbances
The paper by Besselink and Johansson introduces a novel approach for addressing the issue of string stability within vehicle platoons, particularly under the influence of external disturbances. Central to this paper is the development of a delay-based spacing policy allied with a new perception of string stability, termed "disturbance string stability."
Overview of Contributions
- Delay-Based Spacing Policy: The proposed spacing policy innovatively incorporates a time-delay factor, which ensures that all vehicles in a platoon track a spatially varying reference velocity profile. This is particularly beneficial for scenarios involving heavy-duty vehicles navigating variable terrains, such as hilly regions, where a constant reference velocity may not be optimal due to fuel efficiency concerns. The delay-based policy presents a significant leap over conventional constant spacing and constant headway policies, which were shown to be less effective in accommodating varying topographies.
- Disturbance String Stability: Extending the conventional notion of string stability, disturbance string stability explicitly accounts for external disturbances affecting each vehicle within the platoon. Unlike traditional methods that often solely focus on linear systems or consider disturbances limited to the lead vehicle, this new definition incorporates perturbations due to initial conditions and external influences on all vehicles, providing a more robust analysis of stability.
- Control Strategy Design: The paper proposes a control design that guarantees the tracking of the delay-based spacing policy while ensuring disturbance string stability with respect to a spatially varying reference velocity. The novel strategy circumvents the complexities often associated with time-domain designs by framing the control problem within the spatial domain, thereby simplifying the synthesis process and avoiding delay-dependent synthesis techniques.
Numerical Results and Implications
The simulations presented in the paper validate the delay-based spacing policy's effectiveness in maintaining string stability under disturbance conditions. Quantitatively, the findings demonstrate uniform bounds on velocity errors in the platoon, signifying a consistent behavior pattern among vehicles, even when subjected to external perturbations.
Furthermore, the research highlights how the choice of a suitable spacing policy, rather than the specifics of the control design, primarily determines string stability. This insight opens pathways for utilizing a variety of controllers to maintain disturbance string stability while adopting the proposed spacing policy.
Practical and Theoretical Implications
Practically, this approach offers significant benefits for intelligent transportation systems, particularly in heavy-duty vehicle applications where maintaining uniform velocity profiles can result in improved fuel efficiency and reduced aerodynamic drag. Theoretically, the introduction of disturbance string stability adds a new dimension to the analysis of interconnected systems, broadening the potential application scope beyond purely linear dynamics.
Future Considerations
Future developments could explore extending the proposed framework to heterogeneous vehicle platoons, considering vehicles with diverse dynamics and control requirements. Additionally, the integration of this delay-based strategy within broader intelligent transportation infrastructures could be pursued, ensuring seamless communication and coordination across multiple vehicular networks. The implications for global spacing policy adaptation offer a fertile ground for continued exploration within the field of automated vehicular control.
In conclusion, the research by Besselink and Johansson provides a comprehensive paper into vehicle platoon control, illustrating promising advancements in delay-based policies and stability analysis under disturbances. Through continued exploration, this work can significantly contribute to the enhancement of autonomous vehicle systems' robustness and efficiency.