Predictive Control for Alleviation of Gust Loads on Very Flexible Aircraft

Abstract

In this work the dynamics of very flexible aircraft are described by a set of nonlinear, multi-disciplinary equations of motion. Primary structural components are represented by a geometrically-exact composite beam model which captures the large dynamic deformations of the aircraft and the interaction between rigid-body and elastic degrees-of-freedom. In addition, an implementation of the unsteady vortex-lattice method capable of handling arbitrary kinematics is used to capture the unsteady, three-dimensional flow-field around the aircraft as it deforms. Linearization of this coupled nonlinear description, which can in general be about a nonlinear reference state, is performed to yield relatively high-order linear time-invariant state-space models. Subsequent reduction of these models using standard balanced truncation results in low-order models suitable for the synthesis of online, optimization-based control schemes that incorporate actuator constraints. Predictive controllers are synthesized using these reduced-order models and applied to nonlinear simulations of the plant dynamics where they are shown to be superior to equivalent optimal linear controllers (LQR) for problems in which constraints are active.

Modal-Based Nonlinear Estimation and Control for Highly Flexible Aeroelastic Systems

“…In this regard, model predictive control is experiencing a growing interest in control of very flexible aircraft for its versatility and ease with which constraints (on states and/or inputs) are handled. It has widely been used both in gust and manoeuvre load alleviation [7][8][9] and in trajectory tracking [10] problems. However, linearisation of the discretised state-space representation of aeroelastic systems about a reference steady state or a sequential linearisation about the instantaneous configuration has been the main strategy when applying MPC.…”

Data-driven nonlinear aeroelastic models of morphing wings for control

“…Currently, several studies have applied MPC to AWE, although they rely on simplified models [79][80][81][82][83][84]. For flexible aerospace structures [85][86][87][88][89], most control strategies rely on linearized models valid only around a single steady-state trim position or on successive linearization of the underlying system. These models do not allow for optimal control actions over a large range of flight speeds.…”

Proof of Concept for a Hardware-in-the-Loop Nonlinear Control Framework for Very Flexible Aircraft

“…In this regard, model predictive control, which is able to explicitly account for nonlinear dynamics and to directly handle hard constraints on state and control inputs, offers a compelling approach. Indeed, it is experiencing a growing interest in control of very flexible aircraft and application examples can be found in gust and manoeuvre load alleviation [8][9][10] and in trajectory tracking [11] problems. Either linearisation of the discretised state-space representation of the aeroelastic systems about a reference steady state or a sequential linearisation about the instantaneous configuration has been the main strategy to date and nonlinear internal models have been so far elusive.…”