Performance Comparison between Optimised Camber and Span for a Morphing Wing

Morphing technology offers a strategy to modify the wing geometry, and the wing planform and cross-sectional parameters can be optimised to the flight conditions. This paper presents an investigation into the effect of span and camber morphing on the mission performance of a 25-kg UAV, with a straight, rectangular, unswept wing. The wing is optimised over two velocities for various fixed wing and morphing wing strategies, where the objective is to maximise aerodynamic efficiency or range. The investigation analyses the effect of the low and high speed velocity selected, the weighting of the low and high velocity on the computation of the mission parameter, the maximum allowable span retraction and the weight penalty on the mission performance. Models that represent the adaptive aspect ratio (AdAR) span morphing concept and the fish bone active camber (FishBAC) camber morphing concept are used to investigate the effect on the wing parameters. The results indicate that generally morphing for both span and camber, the aerodynamic efficiency is maximised for a 30%–70% to 40%–60% weighting between the low and high speed flight conditions, respectively. The span morphing strategy with optimised fixed camber at the root can deliver up to 25% improvement in the aerodynamic efficiency over a fixed camber and span, for an allowable 50% retraction with a velocity range of 50–115 kph. Reducing the allowable retraction to 25% reduces the improvement to 8%–10% for a 50%–50% mission weighting. Camber morphing offers a maximum of 4.5% improvement approximately for a velocity range of 50–90 kph. Improvements in the efficiency achieved through camber morphing are more sensitive to the velocity range in the mission, generally decreasing rapidly by reducing or increasing the velocity range, where span morphing appears more robust for an increase in velocity range beyond the optimum. However, where span morphing requires considerable modification to the planform, the camber change required for optimum performance is only a 5% trailing edge tip deflection relative to cross-sectional chord length. Span morphing, at the optimal mission velocity range, with 25% allowable retraction, can allow up to a 12% increase in mass before no performance advantage is observed, where the camber morphing only allows up to 3%. This provides the designer with a mass budget that must be achieved for morphing to be viable to increase the mission performance

Integrated flight control system development using CEASIOM

Flight control system design typically involves hardware and software development, requiring the definition of both continuous and discrete design parameters. The control surface topology is an example of a discrete optimization problem, whereas the tuning of control system gains is an example of a continuous one. Contemporary design practice classically involves decoupling these two problems, however, they are intrinsically linked; for example, the maximum performance attainable by the control system software is determined by the control system topology employed. The cascaded effect is that no definitive sequential roadmap of development can be established, resulting in the requirement for an iterative framework using dynamic programming or optimization methods. This paper presents a framework for aircraft design together with the Flight Control System Designer Toolkit, and the Computerised Environment for Aircraft Synthesis and Integrated Optimisation Methods. The software platform was developed for the European Framework 6 Program Simulating Stability and Control and integrates both the reliability-driven hardware analysis and the performance-driven software design. A case study is presented, based on the NASA Boeing 747–100 model, in order to demonstrate the potential impact of introducing control design early into the design process and to show the intrinsic nature of the hardware–software FCS problem

Morphing aircraft: the need for a new design philosophy

This paper proposes a novel framework for classification of morphing technology based on its functionality, operation, and the structural layout. In addition, it highlights the limitations of the conventional design approach to exploit the benefits of the technology using representative examples and results

Methods for conceptual flight control system design

The traditional approach in aircraft conceptual design sizing for stability and control employs the so called “Tail Volume” method, which basically establishes static stability of the design via empirical handbook methods. The methodology dispenses with any formal definition of the Flight Control System architecture and topology, and, does not afford visibility of critical sizing scenarios to the designer. This situation creates a measure of uncertainty when attempts are made to model the flight physics problem, thus thwarting opportunities in performing an advanced assessment of flight handling qualities. This paper reviews the work-in-progress status of an innovative software package aimed at the con- ceptual design phase called Flight Control System Designer Toolkit (FCSDT) that permits Flight Control Systems architecture definition for primary and failure modes, facilitates generation of control laws, assists the designer in apportioning control allocation sched- ules, and finally, analyse the stability and control of aircraft models. Results regarding flight control system architecture design are based on a control surface layout obtained from the Boeing 747 technical manual. Stability and control assessments were based on aerodynamic data generated by the aerodynamic model builder interface to Digital DAT- COM provided by the European funded Framework 6 Program based on the Boeing 747 geometry

Analysis of the Boeing 747-100 using CEASIOM

One of the requirements for the SimSAC project was to use existing aircraft to act as benchmarks for comparison with CEASIOM generated models. Within this paper, results are given for one of these examples, the Boeing 747-100. This aircraft was selected because a complete dataset exists in the open domain, which can be used to validate SimSAC generated data. The purpose of this paper is to both give confidence in, and to demonstrate the capabilities of, the CEASIOM environment when used for preliminary aircraft and control system design. CEASIOM is the result of the integration of a set of sophisticated tools by the European Union funded, Framework 6 SimSAC program. The first part of this paper presents a comparison of the aerodynamic results for each of the solvers available within CEASIOM together with data from the 747-100 model published by NASA. The resulting nonlinear model is then trimmed and analysed using the Flight Control System Designer Toolkit (FCSDT) module. In the final section of the paper a state-feedback controller is designed within CEASIOM in order to modify the longitudinal dynamics of the aircraft. The open and closed loop models are subsequently evaluated with selected failed aerodynamic surfaces and for the case of a single failed engine. Through these results, the CEASIOM software suite is shown to be able to generate excellent quality adaptive-fidelity aerodynamic data. This data is contained within a full nonlinear aircraft model to which linear analysis and control system design can be easily applied

Performance comparison between optimised camber and span for a morphing wing

Morphing technology offers a strategy to modify the wing geometry, and the wing planform and cross-sectional parameters can be optimised to the flight conditions. This paper presents an investigation into the effect of span and camber morphing on the mission performance of a 25-kg UAV, with a straight, rectangular, unswept wing. The wing is optimised over two velocities for various fixed wing and morphing wing strategies, where the objective is to maximise aerodynamic efficiency or range. The investigation analyses the effect of the low and high speed velocity selected, the weighting of the low and high velocity on the computation of the mission parameter, the maximum allowable span retraction and the weight penalty on the mission performance. Models that represent the adaptive aspect ratio (AdAR) span morphing concept and the fish bone active camber (FishBAC) camber morphing concept are used to investigate the effect on the wing parameters. The results indicate that generally morphing for both span and camber, the aerodynamic efficiency is maximised for a 30%–70% to 40%–60% weighting between the low and high speed flight conditions, respectively. The span morphing strategy with optimised fixed camber at the root can deliver up to 25% improvement in the aerodynamic efficiency over a fixed camber and span, for an allowable 50% retraction with a velocity range of 50–115 kph. Reducing the allowable retraction to 25% reduces the improvement to 8%–10% for a 50%–50% mission weighting. Camber morphing offers a maximum of 4.5% improvement approximately for a velocity range of 50–90 kph. Improvements in the efficiency achieved through camber morphing are more sensitive to the velocity range in the mission, generally decreasing rapidly by reducing or increasing the velocity range, where span morphing appears more robust for an increase in velocity range beyond the optimum. However, where span morphing requires considerable modification to the planform, the camber change required for optimum performance is only a 5% trailing edge tip deflection relative to cross-sectional chord length. Span morphing, at the optimal mission velocity range, with 25% allowable retraction, can allow up to a 12% increase in mass before no performance advantage is observed, where the camber morphing only allows up to 3%. This provides the designer with a mass budget that must be achieved for morphing to be viable to increase the mission performance