Abstract
The research presented in this paper focuses on the development of a quasi-Linear Parameter Varying (qLPV) model for the XV-15 tiltrotor aircraft. The specific category of qLPV modeling technique, known as the model stitching technique, is employed to model the time-varying dynamics of XV-15 tiltrotor aircraft over the entire flight envelope. In this modeling approach, discrete linear state-space models are interpolated through lookup tables as function of scheduling parameters with the implementation of nonlinear equations of motion. The XV-15 qLPV model is configured with four scheduling parameters: altitude, nacelle incidence angle, wing flap angle and velocity. Additionally, a computational complexity analysis is presented. In particular, computational sensitivity of qLPV models configured with lookup tables to number of states and number of scheduling parameters is demonstrated. This is done to show the feasibility of real-time implementation of qLPV models with increasing fidelity (number of states) and expanding dynamic flight envelope (number of scheduling parameters).
Highlights
Tiltrotor aircraft represent a promising solution to future civil transportation requirements [1, 2] due to their broader flight envelope compared to conventional and compound helicopters
The contribution and focus of the current paper is to develop a high-order aeroelastic quasi-Linear Parameter Varying (qLPV) model for tiltrotor aircraft representative of NASA’s XV-15 with Advanced Technology Blades (ATB) [7], with four scheduling parameters: altitude h, nacelle incidence angle i, wing flap angle f, and velocity V
The qLPV simulation model developed for XV-15 using the model stitching architecture is validated by comparing the Stability and Control Augmentation Systems (SCAS) off time responses with the data presented in the existing literature
Summary
Tiltrotor aircraft represent a promising solution to future civil transportation requirements [1, 2] due to their broader flight envelope compared to conventional and compound helicopters. The model is quasi-nonlinear in that the linear stability and control derivatives and the corresponding trim data are interpolated through the implementation of lookup tables as function of time-varying scheduling parameters, but nonlinear equations for rigid body motion and gravitational force equations are implemented. A qLPV model containing 51 states (six-degrees-of-freedom rigid body states, rotor states, inflow states and nacelle dynamics) scheduled with three parameters: velocity V, nacelle incidence angle i , and altitude, was developed for a generic tiltrotor configuration by Berger et al [21] In both studies, engine-governor dynamics were missing, limited number of rotor elastic states were modeled and wing aeroelastic states were neglected, which play an important role in Rotorcraft Pilot Coupling (RPC) events [8, 10]. These modes combine to form shortperiod mode
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