Advanced Flight Control Design and Evaluation: An application of time delayed Incremental Backstepping

Advanced Flight Control Design and Evaluation: An application of time delayed Incremental Backstepping

Koschorke, J.F.R.

Falkena, W. (mentor)
Chu, Q.P. (mentor)
Van Kampen, E. (mentor)

Aerospace Engineering

Control and Operations (C&O) - Control and Simulation Division (C&S)

Guidance, Control & Navigation

2012-06-15

The sensor-based approach of Incremental Backstepping is applied to flight control law design in this research project. It allows the usage of the same control law on different types of aircraft without the need for redesign. Apart from full state availability, the derivation of Incremental Backstepping assumes instantaneous control action. Due to actuator lags and delays, the implementation of control commands cannot necessarily be considered instantaneous. This mitigates the stability guarantee provided by Lyapunov theory. Therefore, a novel technique to estimate the time delay margins of the Incremental Backstepping controlled systems is proposed in the thesis. This provides an important stability measure for possible certification and widens the application range of Incremental Backstepping. This simple, yet effective, Lyapunov-based control technique shows positive robustness properties with respect to model uncertainties, unknown parameters, external disturbances and time delay effects. It is applied to the DA 42 aircraft as a (pilot-in-the-loop) rate controller in the scope of this thesis. The implementation requires measurements of the aircrafts angular accelerations and control surface deflections. If the latter is not available, it is shown that filters can still be used in the control system. However, the usage of filters mitigates the highly favorable robustness properties of the closed-loop system. Moreover, a controller evaluation strategy is proposed. It rates the performance and stability properties of the Incremental Backstepping controlled system in terms of the flight control system requirements. Evaluation of the Incremental Backstepping controller shows allowable input multiplicative uncertainties of up to 40% of the nominal value at the worst-case excitation frequency for a controller update rate of 100Hz. When no reference shaping is applied, the handling qualities of the incremental rate controller show to be less desirable than that of a conventional linear controller designed specifically for the DA 42. However, it is possible to improve handling characteristics by reference shaping. Furthermore, the handling characteristics of the incremental controller remain fairly constant along the flight envelope and in adverse flight conditions.

Incremental Backstepping
Time delay
Lyapunov-based control
Fly-By-Wire
Diamond DA 42
Nonlinear
Sensor-based control
SAFAR
Pilot-in-the-loop
Aircraft rate control
Flight control evaluation
SSV

http://resolver.tudelft.nl/uuid:24c0bfab-3243-4ffa-9c96-10a4721fb23a

Student theses

master thesis

(c) 2012 Koschorke, J.F.R.