Null-space control allocation for generalized load reduction in eVTOL aircraft

Abstract Electric Vertical Takeoff and Landing (eVTOL) aircraft rely on distributed electric propulsion systems to generate lift and control forces during low-speed flight. Under external disturbances or internal faults, some rotors may experience disproportionately high loads, leading to thermal stress and long-term reliability degradation. To mitigate such risks, this paper proposes a control allocation method guided by Lyapunov stability theory that minimizes a generalized p -norm of the control load. By exploiting the null space of the control effectiveness matrix, the proposed method asymptotically reduces either overall or peak control load without altering the achieved virtual control. This null-space update supports both conventional and incremental control allocation architectures. In contrast to optimization-based approaches that require solving constrained problems online, the proposed null-space update is lightweight and well-suited for safety-critical flight control systems. Simulation results on a high-fidelity lift-plus-cruise eVTOL platform demonstrate the effectiveness of the method in reducing both overall and peak rotor loads, even in the presence of rotor failures.