Matthew Santer

Topological Optimization of Compliant Adaptive Wing Structure

Load-path-based topology optimization is used to synthesize a compliant adaptive aircraft wing leading edge, which deforms in a prescribed way when subject to a single point internal actuation. The load-path-based optimization method requires the specification of a parent lattice. Increasing the complexity of this lattice means the number of parameters required for a complete representation of the structure in the topology optimization becomes prohibitive, although it is desirable to enable a full exploration of the design space. A new method based on graph theory and network analysis is proposed, which enables a substantial reduction in the required number of parameters to represent the parent lattice. The results from this load-path-based approach are compared with those obtained from the better-known density-based topology optimization method.

Compliant Bistable Dielectric Elastomer Actuators for Binary Mechatronic Systems

In this paper, a new all-polymer actuation approach for binary mechatronic systems is demonstrated. The technology consists of using Dielectric Elastomer actuators in a binary fashion by coupling them with a properly designed compliant structure. Here, a bistable actuator based around the “flip-flop” concept is implemented in which two antagonistic actuators switch a compliant truss between two stable positions. This prototype shows promising performance with output forces ranging from 1 to 3.5 N and displacements of 30% of the actuator dimension.© 2005 ASME

Concept and Design of a Multistable Plate Structure

A concept is presented for a compliant plate structure that deforms elastically into a variety of cylindrical shapes and is able to maintain such shapes due to the presence of bistable components within the structure. The whole structure may be fabricated as a monolithic entity using low-cost manufacturing techniques such as injection molding. The key steps in the analysis of this novel concept are presented, and a functional model is designed and constructed to demonstrate the concept and validate the analysis.

Testing of a Segmented Compliant Deployable Boom for CubeSat Magnetometer Missions

This paper introduces a design of a concertina-folded magnetometer boom with tape spring hinges for CubeSat use. When triggered, the boom is designed to self-deploy due to the release of stored strain energy in a predictable and repeatable fashion. The expected variation in component tolerances means that it is necessary to perform a stochastic nonlinear dynamic analysis to quantify the variation in deployment characteristics. To assist with this analysis a deployment quality metric { the speciflc deployment momentum { is developed. In order to validate the numerical analysis, experimental deployment tests with appropriate gravity o†oad are performed. It is shown that the time-dependent properties of the manufactured CFRP tape spring components can result in ∞aws that are highly detrimental to the deployment behavior.

Topology optimization of adaptive compliant aircraft wing leading edge

A network analysis technique is introduced which may be used for determining and parameterizing the load paths in a lattice structure to enable a load path-based topology optimization to be carried out in a way that permits the use of Genetic Algorithms. This technique provides the designer with a greater level of control over the problem complexity than alternative schemes and enables the use of complex starting topologies. The optimization process is implemented in commercially-available software – Samcef and Boss-quattro – and a complete design process of an adaptive compliant aircraft wing rib from conception via optimization to fabrication of a demonstration model is illustrated.

Aeroelastic Optimization of a Morphing 2D Shock Control Bump

This paper investigates transonic shock control on the RAE2822 airfoil using a deployable shock control bump designed as a morphing structure. The optimal location and shape of the bump are found with respect to minimizing drag. Structural morphing is achieved via optimizer controlled loads, constrained to respect material limitations. A systematic structured mesh generator, capable of refinement in the boundary layer and bump region, is used to generate grids of high quality for CFD analysis. Static aeroelasticity is included in the form of a weak coupling between structural and aerodynamic models. A drag reduction of 4.2 % is achieved with the bump deployed, with the geometry returning to that of the original airfoil when actuation is removed.

Optical space telescope structures: The state of the art and future directions

Future space telescopes will be required to have significantly greater aperture and lower areal density than is currently achievable. Gossamer spacecraft structures have been proposed as a means of achieving this, but the technologies are far from mature. A state-of the-art review is timely and necessary as new structural paradigms are being considered for the next generation of space telescopes. There is, however, a knowledge gap between the structural engineering community and the additional fields involved in the complete telescope system, leading to the proposal of structures which are unlikely to be launched. It is hoped that, by providing a resource by which structural engineers are made aware of the wider issues in telescope design, this review will serve to overcome this knowledge gap to facilitate productive collaboration.

Open-loop flow control at low Reynolds numbers using periodic airfoil morphing

© 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. This paper investigates the application of a periodically deforming airfoil surface for the purpose of flow control at low Reynolds numbers. A physical model has been fabricated by bonding Macro Fiber Composite actuators to the underside of an airfoil’s suction surface. This model is actuated using a high voltage amplifier and has been tested in a closed-loop wind tunnel at Rec = 5 × 10 4 . It was found that at high enough actuation frequencies such a control technique reduces drag and simultaneously increases lift { thus achieving signif- icant improvements in performance in a flight regime notorious for poor airfoil behavior. Furthermore, by delaying the onset of stall, actuation was able to increase the maximum lift achievable by this airfoil section at Rec = 5 × 10 4 which can be of benefit to small aircraft at take-off and landing where high lift coeffcients are required.

Adaptive Vortex Generator Structures for the Reduction of Turbulent Separation

The stereotypical separation control method is the vortex generator which, as a passive device, produces an influence on the flow at all times. We investigate the production of a deployable compliant separation control system that can be formed from the continuous surface of an aerofoil when and where required, and return to normal conditions when not required. The limitations in the development of a 3D finite geometry change from a surface are investigated and a systematic search of the design space is conducted to identify the ideal material parameters. Based on these results a novel method of producing a spatially finite morph is proposed through the use of a 2D lattice structure. Deficiencies are identified with the use of an objective function which reduces geometric error, based on prior knowledge of a suitable geometry, for flow within the boundary layer and an alternative objective is proposed.

Experimental Control of Turbulent Boundary Layers with In-plane Travelling Waves

The experimental control of turbulent boundary layers using streamwise travelling waves of spanwise wall velocity, produced using a novel active surface, is outlined in this paper. The innovative surface comprises a pneumatically actuated compliant structure based on the kagome lattice geometry, supporting a pre-tensioned membrane skin. Careful design of the structure enables waves of variable length and speed to be produced in the flat surface in a robust and repeatable way, at frequencies and amplitudes known to have a favourable influence on the boundary layer. Two surfaces were developed, a preliminary module extending 152 mm in the streamwise direction, and a longer one with a fetch of 2.9 m so that the boundary layer can adjust to the new surface condition imposed by the forcing. With a shorter, 1.5 m portion of the surface actuated, generating an upstream-travelling wave, a drag reduction of 21.5% was recorded in the boundary layer with Reτ = 1125. At the same flow conditions, a downstream-travelling produced a much smaller drag reduction of 2.6%, agreeing with the observed trends in current simulations. The drag reduction was determined with constant temperature hot-wire measurements of the mean velocity gradient in the viscous sublayer, while simultaneous laser Doppler vibrometer measurements of the surface recorded the wall motion. Despite the mechanics of the dynamic surface resulting in some out-of-plane motion (which is small in comparison to the in-plane streamwise movement), the positive drag reduction results are encouraging for future investigations at higher Reynolds numbers.