Flight mechanical analysis of a solar-powered high-altitude platform

Abstract

The German Aerospace Center (DLR) is currently developing an unmanned experimental solar-powered fixed-wing high-altitude platform designed to be stationed in the stratosphere for several days and to carry payload for earth observation missions. This paper deals with a flight mechanical analysis of the aircraft within the preliminary design phase. For this purpose, it briefly describes all disciplines involved in the preliminary design and gives an insight into their methods used. Subsequently, it presents an assessment of the aircraft in terms of stability and control characteristics. Doing so, it first deals with a dynamic stability investigation using a non-linear 6-degrees-of-freedom flight dynamic model with a simple quasi-stationary approach to account for flexibility, in which the aerodynamic derivatives are given for different airspeed-dependent flight shapes. The investigations show that the aircraft is naturally stable over the complete flight envelope. It does not have a typical short period mode. Instead, the corresponding mode involves altitude and airspeed changes to a large extent. At low airspeeds, the Dutch roll and spiral modes couple and form two non-classical modes. Second, it presents a control surface design evaluation process for the aircraft based on a flight mechanical requirement. This requirement addresses the necessary control authority to counteract the aircraft’s responses due to gust encounters to not exceed afore-defined limits and to prevent the aircraft from entering a flight condition that it cannot be recovered from.

Evaluation of the controllability of a remotely piloted high-altitude platform in atmospheric disturbances based on pilot-in-the-loop simulations

“…In the flight dynamics model, the aircraft aerodynamics is modelled using aerodynamic derivatives as described in [13]. Nevertheless, in [13] a two-point aerodynamic model was used for the longitudinal motion to separate the influences of wing-body (including the payload bay) and horizontal tailplane (HTP). This signifies that the aerodynamic forces and moments are calculated for these points separately.…”

“…For intermediate airspeeds, linear interpolation is performed at each time step during the simulation runtime. The aerodynamic derivatives are provided by the aerodynamics department as described in [13] and calculated using the vortex lattice method Athena Vortex Lattice (AVL) [15,16] for the flight shapes at the respective airspeeds.…”

Comparative Study and Airspeed Sensitivity Analysis of Full-Wing Solar-Powered UAVs Using Rigid-Body, Multibody, and Rigid-Flexible Combo Models

“…Ma, Zhu, and Zhou [13] conducted an analysis to identify the reasons behind the poor accuracy of taxiing trajectories of a full-wing UAV, determined the relationship between the uncertainty of model parameters in the 6-DOF equations and the control accuracy, and experimentally calibrated the aerodynamic and propeller model parameters. Hasan et al [14] focused on the wind disturbance characteristics of large-scale solar-powered UAVs and noted that airspeed variations can cause structural deformations that impact motion modes. Benassi and Aquilini [15] highlighted changes in design requirements for stratospheric solarpowered UAVs and emphasized that structural dynamics need to be considered during takeoff and landing phases, even though they only account for 1% of the total flight time.…”

Coupled Aerodynamics–Structure Analysis and Wind Tunnel Experiments on Passive Hinge Oscillation of Wing-Tip-Chained Airplanes

“…Numerous studies have been conducted regarding aircrafts with high-aspect ratios in the past [2][3][4]. However, for certain cases, it could be difficult to increase the wing span over a certain length.…”