Grid and Polytopic LPV Modeling of Aeroelastic Aircraft for Co-design

Abstract

Future aircraft tend to have increased flexibility that leads to increased aeroservoe-lastic (ASE) effects. Therefore, future aircraft control systems need active control to suppress ASE effects. Active flutter suppression can be effectively done in the linear parameter varying (LPV) framework. Control surface sizing for aircraft is traditionally done by iterations. In this approach engineering rules are used to determine the size of the control surfaces and the control laws are designed afterwards. Such method, besides being time consuming, might have further challenges in the future due to the coupling between the flexible and rigid body dynamics. Instead, ”co-design” was recently proposed. In the co-design approach parametric aircraft models are developed based on which the control surface sizing and the control design are optimized in a single step. The purpose of this paper is to create a control oriented, parametric control surface model of the mini MUTT aircraft that can be applied for co-design. The resulting control oriented LPV model needs to have sufficiently low dynamic order, which is achieved by the ”bottom-up” modeling approach. A grid based LPV model is obtained from the nonlinear model by Jacobian linearization and the Tensor Product (TP) type polytopic model is obtained from the grid based LPV model via TP model transformation. The resulting low order parametric control surface LPV models are assessed with the v-gap metric. These models can serve as the basis of simultaneous baseline/flutter suppression control synthesis and control surface sizing optimization.