Noncertainty Equivalent Adaptive Backstepping Control for Advanced Fighter Subject to Unsteady Effects and Input Constraints

Chijun Zhou,Jikun Ye,Humin Lei,Changxin Luo,Jihong Zhu,Kenneth M Sobel

doi:10.1155/2021/6669380

Abstract

This paper presents a noncertainty equivalent adaptive backstepping control scheme for advanced fighter attitude tracking, in which unsteady effects, parameter uncertainties, and input constraints are all considered which increase the design difficulty to a large extent. Based on unsteady attitude dynamics and the noncertainty equivalent principle, a new observer is first developed to reconstruct the immeasurable and time-varying unsteady states. Afterwards, the unsteady aerodynamics is compensated in the backstepping controller where the command filter is introduced to impose physical constraints on actuators. In order to further enhance the robustness, the noncertainty equivalent adaptive approach is again used to estimate the uncertain constant parameters. Moreover, stability of the closed-loop system that includes the state observer, parameter estimator, and backstepping controller is proven by the Lyapunov theorem in a unified architecture. Finally, simulation results show that performance of the deterministic control system can be captured when attractive manifolds are achieved. The effectiveness and robustness of the proposed control scheme are verified by the Herbst maneuver.

Highlights

Flight envelopes are substantially extended by the fourth generation fighter which directly leads to urgent demands for higher performance control laws
This paper is devoted to the constraint adaptive backstepping control design for the advanced fighter, where robust tracking of the predefined trajectories has been achieved
Unsteady effects, parameter uncertainties, and input constraints are all considered which brings forward a great challenge for the control design

Summary

Introduction

Flight envelopes are substantially extended by the fourth generation fighter which directly leads to urgent demands for higher performance control laws. A novel approach for stabilization and adaptive control of uncertain nonlinear systems based on immersion and invariance (I&I) methodology has been proposed in [23] and further developed in [24, 25] This method gives a noncertainty equivalent adaptive (NCEA) law which is different from the traditional certainty equivalent adaptive (CEA) method. Due to the advantages in prescribing estimate error dynamics and separately synthesizing controller and estimator, this method shows great potential for uncertain nonlinear systems with complex structures It relies on solving a partial differential equation (PDE), which is difficult for multivariable systems [27]. Simulations and conclusions are given in fifth and sixth sections, respectively

Unsteady Attitude Dynamics

Unsteady State Observation

Constraint Adaptive Backstepping Control

Methods

Numerical Simulations and Discussions

Conclusions