Design and flight testing of manual nonlinear flight control laws

Abstract

This paper describes the design of a manual flight controller, based upon nonlinear model-based control laws. These control laws include the previously developed concept of Pseudo Control Hedging (PCH). This PCH algorithm adapts the reference model for the system output in case of unachievable commands due to control input saturation. This control algorithm has been applied in the body angular rate control loops of a high fidelity simulation model of the VFW-614 ATTAS (Advanced Technologies Testing Aircraft System) laboratory aircraft, where its beneficial influence has been illustrated. Test flights have been performed with ATTAS to evaluate the flight control technique in a relevant environment. Nomenclaturegain L; M ; N combined aerodynamic and thrust moment around the body X/Y/Z axis [Nm] N 1 fan speed [s -1 ] OS overshoot [rad] S wing area [m 2 ] V airspeed [m/s] b wingspan [m] c mean aerodynamic chord [m] g gravity constant [m/s 2 ] n x ; n y ; n z load factor along body X/Y/Z axis [-] p; q; r roll, pitch and yaw rate around the body X/Y/Z axis [rad/s] u input u b ; v b ; w b airspeed velocity components along body X/Y/Z axis [m/s] u e ; v e ; w e airspeed velocity components along earth fixed X/Y/Z axis [m/s] x; y; z position coordinates along X/Y/Z axis [m] (reference frame varies) x state vector Subscript 0 constant term A with respect to aerodynamic reference frame bwith respect to body fixed reference frame e with respect to earth fixed reference frame k with respect to kinematic reference frame a; e; r aileron, elevator and rudder c; comm commanded * Researcher,

Stability and Robustness Analysis and Improvements for Incremental Nonlinear Dynamic Inversion Control

“…The relation between attitude angles and angular rates is based on a kinematic equation independent of aircraft characteristics, see Eq. (21). Therefore, this loop is based on the standard NDI technique instead of INDI.…”

Design and Piloted Simulator Evaluation of Adaptive Safe Flight Envelope Protection Algorithm

“…The longitudinal control law is somewhat different than the setup as described in Ref. [27], because it has been extended to a C * control law.…”

“…However, the linear controller has shown to be capable to deal with these modeling errors, as discussed in Ref. [27]. …”

“…More detailed information is available in Ref. [27]. It should be noted that this dynamic inversion is not perfect due to the presence of the multiplicative uncertainties in the aerodynamic model.…”

“…Global overview of the control structure seteup, with nonlinear dynamic inversion, linear controllers, reference models and pilot command filtering, modified from Ref. [27] In Fig. 3, it can also be seen that the linear control input is based upon two orders of derivatives of the reference model, as is also described in Eq.…”