Nonlinear Incremental Control for Flexible Aircraft Trajectory Tracking and Load Alleviation

Abstract

This paper proposes a nonlinear control architecture for flexible aircraft simultaneous trajectory tracking and load alleviation. By exploiting the control redundancy, the gust and maneuver loads are alleviated without degrading the rigid-body command tracking performance. The proposed control architecture contains four cascaded control loops: position control, flight path control, attitude control, and optimal multi-objective wing control. Since the position kinematics are not influenced by model uncertainties, the nonlinear dynamic inversion control is applied. On the contrary, the flight path dynamics are perturbed by both model uncertainties and atmospheric disturbances; thus the incremental sliding mode control is adopted. Lyapunov-based analyses show that this method can simultaneously reduce the model dependency and the minimum possible gains of conventional sliding mode control methods. Moreover, the attitude dynamics are in the strict-feedback form; thus the incremental backstepping sliding mode control is applied. Furthermore, a novel load reference generator is designed to distinguish the necessary loads for performing maneuvers from the excessive loads. The load references are realized by the inner-loop optimal wing controller, while the excessive loads are naturalized by flaps without influencing the outer-loop tracking performance. The merits of the proposed control architecture are verified by trajectory tracking tasks and gust load alleviation tasks in spatial von Kármán turbulence fields.

Review of the Flight Control Method of a Bird-like Flapping-Wing Air Vehicle

“…Model-based controllers [ 61 ] enable the simulation and analysis of the model, thereby enhancing control accuracy. However, their implementation requires the development of intricate models beforehand and a high level of modeling proficiency.…”

Morphing wing design using integrated and distributed trailing edge morphing

“…The conflict can be prevented if the aircraft features a sufficiently high number of control surfaces such that several control tasks can be addressed simultaneously. This would allow addressing both the attitude control of the aircraft body (pitch, roll, yaw) and aeroelastic control (load alleviation, flutter control etc) by continuously adjusting the same set of control surfaces (control allocation) [29]. When combined with morphing, more objectives can be achieved in control architecture, such as shape and drag optimisation, leading to a more optimal lift distribution.…”

“…As a result, this inhibits the use of the morphing mechanism for multi-objective flight control and limits its use as a direct replacement of conventional control surfaces for rigid body motion control (ailerons, rudders and elevators). Various control design studies highlight the necessity and effectiveness of multi-objective flight control, load alleviation, and drag reduction performed by distributed multi-flap systems such as the VCCTEF in [26,27] and conventionally flapped over-actuated aircraft models [29].…”

Aeroelastic Wing Demonstrator with a Distributed and Decentralized Control Architecture

“…The aeroservoelastic SmartX-Neo wing is controlled by a linear-quadratic regulator (LQR) controller [16]. This is a linear optimal control method that provides the optimal feedback gain matrix K to stabilize the system.…”