Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Safe and Operationally Efficient Longitudinal Control of Autonomous Truck Platoons

Alexander Hammerl, Ravi Seshadri, Thomas Kjær Rasmussen, Otto Anker Nielsen

TL;DR

The paper presents a hierarchical longitudinal control framework for autonomous truck platoons that guarantees safety with a high-order control barrier function, achieves string-stable spacing via a lag-aware PID regulator, and optimizes fuel efficiency on a slow timescale through an economic planner. It provides a rigorous mapping from desired transient characteristics to controller gains, accounting for first-order actuation lag, and proves convergence to the Optimal Velocity Model with Relative Velocity (OVRV) under steady-state conditions, with explicit worst-case bounds on spacing transients driven by leader jerk. Numerical case studies against canonical baselines demonstrate improved safety, reduced spacing error, and enhanced energy efficiency, validating the practical value of the layered approach in both small and large platoons. The framework relies on modest V2V communication (predecessor speed and acceleration) and offers analytical robustness guarantees that extend to arbitrary platoon sizes, supporting scalable deployment in real-world truck platooning. Future directions include field validation, integration with physics-based models, and exploring decentralized secure communication via blockchain to safeguard data exchange while preserving real-time control guarantees.

Abstract

This paper presents a hierarchical longitudinal control architecture for autonomous truck platoons that jointly addresses safety, string stability, and economic efficiency. The framework integrates a high-rate safety projection filter, a spacing-regulation layer based on a lag-aware proportional-integral-derivative (PID) controller, and a slow-timescale economic optimizer balancing fuel consumption and travel time. The safety layer guarantees collision avoidance under bounded actuation delays by enforcing forward invariance of a velocity-aware headway constraint through a high-order control barrier function. The regulation layer shapes the spacing-error dynamics into a second-order form with interpretable parameters for damping and natural frequency while explicitly accounting for actuator lag. At the macroscopic level, fuel use is modeled by a tractive-power relation that captures aerodynamic benefits of close spacing, enabling a long-term optimization of speed trajectories subject to comfort and energy trade-offs. We show that the closed-loop dynamics converge to the Optimal Velocity Model with Relative Velocity (OVRV) under undisturbed conditions and derive worst-case upper bounds for platoon stabilization time. Numerical case studies demonstrate the superiority of the proposed design over an canonical baseline controllers in both transient behavior and long-term energy efficiency.

Safe and Operationally Efficient Longitudinal Control of Autonomous Truck Platoons

TL;DR

The paper presents a hierarchical longitudinal control framework for autonomous truck platoons that guarantees safety with a high-order control barrier function, achieves string-stable spacing via a lag-aware PID regulator, and optimizes fuel efficiency on a slow timescale through an economic planner. It provides a rigorous mapping from desired transient characteristics to controller gains, accounting for first-order actuation lag, and proves convergence to the Optimal Velocity Model with Relative Velocity (OVRV) under steady-state conditions, with explicit worst-case bounds on spacing transients driven by leader jerk. Numerical case studies against canonical baselines demonstrate improved safety, reduced spacing error, and enhanced energy efficiency, validating the practical value of the layered approach in both small and large platoons. The framework relies on modest V2V communication (predecessor speed and acceleration) and offers analytical robustness guarantees that extend to arbitrary platoon sizes, supporting scalable deployment in real-world truck platooning. Future directions include field validation, integration with physics-based models, and exploring decentralized secure communication via blockchain to safeguard data exchange while preserving real-time control guarantees.

Abstract

This paper presents a hierarchical longitudinal control architecture for autonomous truck platoons that jointly addresses safety, string stability, and economic efficiency. The framework integrates a high-rate safety projection filter, a spacing-regulation layer based on a lag-aware proportional-integral-derivative (PID) controller, and a slow-timescale economic optimizer balancing fuel consumption and travel time. The safety layer guarantees collision avoidance under bounded actuation delays by enforcing forward invariance of a velocity-aware headway constraint through a high-order control barrier function. The regulation layer shapes the spacing-error dynamics into a second-order form with interpretable parameters for damping and natural frequency while explicitly accounting for actuator lag. At the macroscopic level, fuel use is modeled by a tractive-power relation that captures aerodynamic benefits of close spacing, enabling a long-term optimization of speed trajectories subject to comfort and energy trade-offs. We show that the closed-loop dynamics converge to the Optimal Velocity Model with Relative Velocity (OVRV) under undisturbed conditions and derive worst-case upper bounds for platoon stabilization time. Numerical case studies demonstrate the superiority of the proposed design over an canonical baseline controllers in both transient behavior and long-term energy efficiency.

Paper Structure

This paper contains 11 sections, 4 theorems, 81 equations, 6 figures, 4 tables.

Table of Contents

  1. Introduction
  2. System Model and Control Objectives
  3. Hierarchical Longitudinal Control Design
  4. Safety Projection Filter
  5. Spacing Regulation via PID Control
  6. Gain Tuning for Lagged Actuators
  7. Robustness Analysis
  8. Case Studies
  9. Experimental Design and Parameter Estimation
  10. Presentation Of Results
  11. Conclusion

Key Result

Lemma 1

Assume $u_i$ is continuously differentiable on $[0,\infty)$ with finite bounds for some $U>0$ and bandwidth parameter $\omega_n>0$. If the actuator is engaged consistently, $a_i(0)=u_i(0)$, then the tracking error $r_i:=a_i-u_i$ obeys the uniform bound Equivalently, with $\varepsilon := \omega_n\tau_a$, one has

Figures (6)

  • Figure 1: Velocity trajectories of the two-truck platoon under different control strategies.
  • Figure 2: Spacing-error trajectories of the two-truck platoon under different control strategies.
  • Figure 3: Velocity trajectories of the eight-truck platoon under different control strategies. Y-limits vary per panel to highlight transient shapes.
  • Figure 4: Spacing-error trajectories of the eight-truck platoon under different control strategies. Y-limits vary per panel to highlight transient shapes.
  • Figure 5: Velocity trajectories of a four-vehicle platoon during an emergency braking maneuver under different control strategies.
  • ...and 1 more figures

Theorems & Definitions (8)

  • Lemma 1: Uniform small-lag approximation $a_i \approx u_i$.
  • proof
  • Proposition 1: Convergence to OVRV equilibrium
  • proof
  • Lemma 2: Bounded jerk
  • proof
  • Proposition 2: Soft Spacing Hierarchy
  • proof