Time Delayed Incremental Nonlinear Control

Abstract

A sensor-based approach of Incremental Nonlinear Control is applied to flight control law design in this paper. It allows the usage of the same control law on different types of aircraft without the need for redesign. The derivation of this set of sensor-based control laws assumes fast control action. Due to actuator lags and delays, the implementation of control commands cannot necessarily be considered fast. This mitigates the stability guarantee provided by Lyapunov theory. Therefore, a novel technique to estimate the time delay margins of the incremental Lyapunov-based controlled systems is proposed in this paper. It provides an important stability measure for possible certification, aids in choosing appropriate controller gains and widens the application range of Incremental Nonlinear Control. The outcome is a simple, yet effective, control design methodology that gives control laws showing positive robustness properties with respect to model uncertainties, unknown parameters, external disturbances and time delay effects. In an example, it is applied to a DA 42 aircraft model as a (pilot-in-the-loop) rate controller. The implementation requires measurements of the aircrafts angular accelerations and control surface deflections but shows very positive results.