Robust helicopter sliding mode control for enhanced handling and trajectory following

Helicopters in tactical missions require superior handling and stability in turbulence. This paper proposes a sliding mode control (SMC)-based helicopter trajectory controller for enhanced handling qualities (HQs) with robustness to endogenous (modeling) and exogenous (turbulence) uncertainties. The flight control problem is posed as one of attitude, angular rate, and translational rate command tracking with closed-loop axial responses conforming to predicted level 1 HQs. The required closed-loop behavior is then enforced by a two-loop output-tracking SMC treating interaxis coupling and turbulence as matched, bounded uncertainties. To mitigate the chattering effect of SMC, a continuous control approximation using the boundary-layer concept is applied. The stability and tracking performance of the two-loop controller are analyzed. Furthermore, actuator saturations encountered during aggressive maneuvers are mitigated by reference command adaptation based on pseudo-control hedging. The proposed controller is evaluated against selected HQ temporal response criteria, two mission task elements requiring moderate to aggressive agility, and a shipboard approach in high-intensity turbulence. Simulation results highlight the controller’s trajectory tracking accuracy, adequate axial decoupling, and insensitivity to disturbances.