A command filtered backstepping approach is presented that uses adaptive function approximation to control unmanned air vehicles. The controller is designed using three feedback loops. The command inputs to the airspeed and flight-path angle controller are x c , γ c , V c and the bounded first derivatives of these signals. That loop generates comand inputs μ c , α c for a wind-axis angle loop. The sideslip angle command β c is always zero. The wind-axis angle loop generates rate commands P c , Q c , R c for an inner loop that generates surface position commands. The control approach includes adaptive approximation of the aerodynamic force and moment coefficient functions. The approach maintains the stability (in the sense of Lyapunov) of the adaptive function approximation process in the presence of magnitude, rate, and bandwidth limitations on the intermediate states and the surfaces.

Backstepping-Based Flight Control with Adaptive Function Approximation

The design of an adaptive backstepping flight control law for the F-16/MATV (multi-axis thrust vectoring) aircraft is discussed. The control law tracks reference trajectories with the angle of attack a, the stability-axes roll rate p s , and the total velocity V T . Furthermore, the sideslip angle β has to be kept at zero. B-spline neural networks are used inside the parameter update laws of the backstepping control law to approximate the uncertain aerodynamic forces and moments. Command filters are used to implement the constraints on the control surfaces and the virtual control states. The stability of the parameter estimation process during periods of saturation is guaranteed by using a modified tracking error definition, in which the effect of the saturation has been filtered out. The controller and its performance are evaluated on a nonlinear, six-degrees-of-freedom dynamic model of an F-16/MATV aircraft in a number of simulation scenarios.

Nonlinear Flight Control Design Using Constrained Adaptive Backstepping

In this paper, the robust adaptive controller is investigated for the longitudinal dynamics of a generic hypersonic flight vehicle. The proposed methodology addresses the issue of controller design and stability analysis with respect to parametric model uncertainty and input saturations for the control-oriented model.The velocity and attitude subsystems are transformed into the linearly parameterized form. Based on the parameter projection estimation, the dynamic inverse control is proposed via the back-stepping scheme. In order to avoid the problem of “explosion of complexity,” by introducing a first-order filtering of the synthetic input at each step, the dynamic surface control is designed. The closed-loop system achieves uniform ultimately bounded stability. The compensation design is employed when the input saturations occur. Simulation results show that the proposed approach achieves good tracking performance.

Dynamic surface control of constrained hypersonic flight models with parameter estimation and actuator compensation

Nonlinear disturbance observer based robust backstepping control for a flexible air-breathing hypersonic vehicle

This paper treats the problem of synchronized control of spacecraft formation flying (SFF) in the presence of input constraint and parameter uncertainties. More specifically, backstepping based robust control is first developed for the total 6 DOF dynamic model of SFF with parameter uncertainties, in which the model consists of relative translation and attitude rotation. Then this controller is redesigned to deal with the input constraint problem by incorporating a command filter such that the generated control could be implementable even under physical or operating constraints on the control input. The convergence of the proposed control algorithms is proved by the Lyapunov stability theorem. Compared with conventional methods, illustrative simulations of spacecraft formation flying are conducted to verify the effectiveness of the proposed approach to achieve the spacecraft track the desired attitude and position trajectories in a synchronized fashion even in the presence of uncertainties, external disturbances and control saturation constraint.

6 DOF synchronized control for spacecraft formation flying with input constraint and parameter uncertainties.

This article presents a new method for on-line approximation based backstepping control in the presence of known magnitude, rate, or bandwidth constraints on the intermediate states or actuators The presentation is based on developing the design and analysis for a second-order system - these results can be recursively extended to higher order systems The new results allow on-line learning to continue even when known magnitude, rate, or bandwidth constraints are in effect, even though those constraints do not allow the control objectives to be met for the duration of those constraints

/pdf/on-line-approximation-based-control-of-uncertain-nonlinear-87m4p6qvuq.pdf

On-line approximation based control of uncertain nonlinear systems with magnitude, rate and bandwidth constraints on the states and actuators

This document derives stable on-line approximation based control algorithms for application to the longitudinal control (7, LY, Q, V) for an uninhabited combat air vehicle (UCAV). The objectives of the control approach are to stabilize the aircraft dynamics and achieve accurate command tracking in the presence of significant nonlinear model error. This error could be due to decreased modeling effort during the design process or the result of events that occur during the vehicle flight (i.e., battle damage). Lyapunov stability analysis and simulation demonstrations of the achieved performance are included.

M. Sharma

Papers

On-line approximation based control of uncertain nonlinear systems with magnitude, rate and bandwidth constraints on the states and actuators

On-line approximation based aircraft longitudinal control