Abstract
This paper treats a robust adaptive trajectory-tracking control design for a rotorcraft using a high-fidelity math model subject to model uncertainties. In order to control the nonlinear rotorcraft model which shows strong inter-axis coupling and high nonlinearity, incremental backstepping approach with state-dependent control effectiveness matrix is utilized. Since the incremental backstepping control suffers from performance degradation in the presence of control matrix uncertainties due to change of flight conditions, control system robustness is improved by combining the least squares parameter estimator to estimate time varying uncertainties contained in the control effectiveness matrix. Also, by selecting a suitable gain set by investigating the error dynamics, a uniform trajectory-tracking performance over operational flight envelope of the rotorcraft is ensured without resorting to the conventional gain scheduling method. To evaluate the proposed controller, comparative results between IBSC and Adaptive IBSC are provided in this paper with sequential maneuvers from the ADS-33E-PRF. The proposed method shows improved tracking performance under variations in control effective matrix in the flight simulation. Robust and stable parameter estimation is also guaranteed due to the implementation of the DF-RLS algorithm for the least squares estimator.
Highlights
With recent advances in the flight control system (FCS) technology, enabling safe and reliable operation of the aircraft became a fundamental requirement for FCS design.many challenges arise when designing a safe and robust rotorcraft FCS due to its highly nonlinear and inherently unstable dynamics
This paper mainly focuses on an effective solution of these issues in the design of the trajectory-tracking controller for the rotorcraft using the adaptive backstepping control design
The conventional linear control design has been still widely used for the rotorcraft and representative successful applications can be found in its implementations on the JUH-60A [2] and AH-64D [3]
Summary
With recent advances in the flight control system (FCS) technology, enabling safe and reliable operation of the aircraft became a fundamental requirement for FCS design. The performance of EF-RLS is often sensitive to a pre-selected forgetting factor which is typically chosen by a trial-and-error process Considering these issues, various techniques such as variable forgetting [27,28] and direction forgetting [29,30,31] are widely investigated. The main contributions of this paper can be summarized as follows (1) The design of an adaptive IBSC (AIBSC) using the LS-based parameter estimator, (2) its applications to the rotorcraft trajectory-tracking problem using the high-fidelity math model, (3) the proposal of the effective gain selection strategy uniformly applicable over OFE, and (4) the validation of the proposed control solutions using various rotorcrafts’ mission-task-elements (MTEs) over a wide range of operating conditions.
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