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Robust Adaptive Sliding-Mode Control for Damaged Fixed-Wing UAVs

Mark Spiller, Lennart Kracke, Johannes Autenrieb

TL;DR

The paper tackles damage-tolerant control for fixed-wing UAVs by introducing a robust adaptive sliding-mode controller (RASMC) that handles aerodynamic coefficient perturbations and partial loss of control effectiveness. It develops a damage-aware nonlinear flight dynamics model and proves Lyapunov-based stability for both static-gain SMC and adaptive-gain RASMC, including uncertainty bounds. The approach is embedded in an existing autopilot with inner- and outer-loop control and demonstrated in simulations on a damaged Proteus UAV, achieving stable states with bounded tracking errors and reduced chattering via a boundary layer. The work advances the practical resilience of UAV autopilots and sets the stage for future work on actuator dynamics and saturation limits.

Abstract

Many unmanned aerial vehicles (UAVs) can remain aerodynamically flyable after sustaining structural or control surface damage, yet insufficient robustness in conventional autopilots often leads to mission failure. This paper proposes a robust adaptive sliding mode controller (RASMC) for fixed-wing UAVs subject to aerodynamic coefficient perturbations and partial loss of control surface effectiveness. A damage-aware flight dynamics model is developed to systematically analyze the impact of such impairments on the closed-loop behavior. The RASMC is designed to ensure reliable tracking and stabilization, while a gain adaptation law maintains low control effort under nominal conditions and increases the gains as needed in the presence of aerodynamic damage. Lyapunov-based stability guarantees are derived, and assumptions on admissible uncertainty bounds are formulated to characterize the limits within which closed-loop stability and performance can be ensured. The proposed controller is implemented within an existing UAV autopilot framework, where outer-loop guidance and speed control modules provide reference commands to the RASMC for attitude stabilization. Simulations demonstrate that, despite significant aerodynamic damage and control surface degradation, all closed-loop states remain stable with bounded tracking errors.

Robust Adaptive Sliding-Mode Control for Damaged Fixed-Wing UAVs

TL;DR

The paper tackles damage-tolerant control for fixed-wing UAVs by introducing a robust adaptive sliding-mode controller (RASMC) that handles aerodynamic coefficient perturbations and partial loss of control effectiveness. It develops a damage-aware nonlinear flight dynamics model and proves Lyapunov-based stability for both static-gain SMC and adaptive-gain RASMC, including uncertainty bounds. The approach is embedded in an existing autopilot with inner- and outer-loop control and demonstrated in simulations on a damaged Proteus UAV, achieving stable states with bounded tracking errors and reduced chattering via a boundary layer. The work advances the practical resilience of UAV autopilots and sets the stage for future work on actuator dynamics and saturation limits.

Abstract

Many unmanned aerial vehicles (UAVs) can remain aerodynamically flyable after sustaining structural or control surface damage, yet insufficient robustness in conventional autopilots often leads to mission failure. This paper proposes a robust adaptive sliding mode controller (RASMC) for fixed-wing UAVs subject to aerodynamic coefficient perturbations and partial loss of control surface effectiveness. A damage-aware flight dynamics model is developed to systematically analyze the impact of such impairments on the closed-loop behavior. The RASMC is designed to ensure reliable tracking and stabilization, while a gain adaptation law maintains low control effort under nominal conditions and increases the gains as needed in the presence of aerodynamic damage. Lyapunov-based stability guarantees are derived, and assumptions on admissible uncertainty bounds are formulated to characterize the limits within which closed-loop stability and performance can be ensured. The proposed controller is implemented within an existing UAV autopilot framework, where outer-loop guidance and speed control modules provide reference commands to the RASMC for attitude stabilization. Simulations demonstrate that, despite significant aerodynamic damage and control surface degradation, all closed-loop states remain stable with bounded tracking errors.
Paper Structure (5 sections, 2 theorems, 50 equations, 2 figures)

This paper contains 5 sections, 2 theorems, 50 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Modeling of Damaged Fixed-Wing UAV
  3. Robust Attitude Controller Design
  4. Simulation Study
  5. Conclusions

Key Result

Theorem 1

Consider the control law with where $\tilde{\Theta}=\Theta-\Theta_r$ is the control tracking error, $\Theta_r = ^T$ are the reference attitude angles, $\Lambda\in\mathbb{R}^{3\times3}$ is chosen so that matrix $\bar{\Lambda}=-\Lambda$ is Hurwitz, $K=\mathrm{diag}(k)\in\mathbb{R}^{3\times3}$ is a diagonal matrix of the controll is the sliding variable. Let $B_{ij}\in\mathbb{R}$ be bounds of $\f

Figures (2)

  • Figure 1: Autopilot with inner- and outer-loop control layers (feedback of the system states not visualized).
  • Figure 2: Controller performance evaluation of RASMC

Theorems & Definitions (4)

  • Theorem 1: Static gain SMC
  • proof
  • Theorem 2: RASMC
  • proof