Quaternion-Based Sliding Mode Control for Six Degrees of Freedom Flight Control of Quadrotors

TL;DR

This work tackles robust 6-DOF quadrotor flight control by developing a cascaded quaternion-based sliding mode controller that uses a coordinate-free attitude generation to achieve global stability and avoid quaternion unwinding. The outer-loop position controller and inner-loop attitude controller are integrated with a trajectory generator that yields q_d, ω_d, and α_d directly on the quaternion manifold, avoiding Euler-angle simplifications. Stability is established via a Lyapunov function ensuring robust performance against model uncertainties and disturbances. In simulations, the proposed method outperforms geometric and Euler-based SMC approaches, achieving lower actuator effort and faster convergence, particularly during aggressive maneuvers.

Abstract

Despite extensive research on sliding mode control (SMC) design for quadrotors, the existing approaches suffer from certain limitations. Euler angle-based SMC formulations suffer from poor performance in high-pitch or -roll maneuvers. Quaternion-based SMC approaches have unwinding issues and complex architecture. Coordinate-free methods are slow and only almost globally stable. This paper presents a new six degrees of freedom SMC flight controller to address the above limitations. We use a cascaded architecture with a position controller in the outer loop and a quaternion-based attitude controller in the inner loop. The position controller generates the desired trajectory for the attitude controller using a coordinate-free approach. The quaternion-based attitude controller uses the natural characteristics of the quaternion hypersphere, featuring a simple structure while providing global stability and avoiding unwinding issues. We compare our controller with three other common control methods conducting challenging maneuvers like flip-over and high-speed trajectory tracking in the presence of model uncertainties and disturbances. Our controller consistently outperforms the benchmark approaches with less control effort and actuator saturation, offering highly effective and efficient flight control.

Figures (10)

• Figure 1: Quadrotor model and coordinate frames.
• Figure 2: Controller architecture.
• Figure 3: Quaternion error for flip-over maneuver scenario. The different initial values of the geometric controller are due to the difference in its reference generation method within its position controller.
• Figure 5: Position error in flip-over maneuver scenario.
• Figure 7: Thrust generated by each motor in the flip-over maneuver scenario.