Recently, smoothly-deforming aircraft structures have been investigated for their ability to adapt to varying flight conditions. Researchers aim to achieve large changes in the shape of the wings: area changes of up to 50% and aspect-ratio changes of up to 200% are being pursued. The research described in this paper aims to develop a structural concept capable of achieving continuous stable deformations over a large range of aircraft shapes. The basic concept underlying the approach is a compliant cellular truss, with tendons used as active elements. The truss members of the unit cell are connected through compliant joints such that only modest bending moments may be transmitted from one member to another. Actuation is achieved by pulling on one set of cables while releasing another set. The tendonactuated compliant truss can be made to behave locally, and temporarily, as a nearmechanism, by releasing appropriate cables. As a result, in the absence of aerodynamic forces, the structure can be morphed using relatively low forces. The cables are reeled in or released in a controlled manner while the structure is loaded, hence, the stability of the structure can be maintained in any intermediate position. Highly-distributed actuation also enables the simultaneous achievement of global shape changes as the accumulation of local ones, while the use of compliant joints rather than true rotating joints eliminates binding as a significant concern. A six-noded octahedral cell with diagonal tendon actuation is developed for a bending type deformation in the wing. Initial cell geometry is determined by "strain matching" to the local morphing deformation required by the application. A finite element analysis is performed on a wing made of these unit cells and sized for a representative UAV weighing 3000 lbs. The areas of the individual truss members are sized so that they don't fail or buckle under the air loads, while deflection at the wing tip is reduced. The octahedral unit cell is capable of achieving smooth deformations of the truss structure. The cell size is dictated by the available space and the morphing strain. The cell sizes are reasonable for strains on the order of 10% to 15% and get smaller for larger strains. Additional cell shapes are being investigated for larger area changes through a process of topology optimization using genetic algorithms. Numerous other technical challenges remain, including the details of actuation and a robust skin. Nomenclature B= kinematic matrix d = vector of displacement of joints e = vector of elongation of members l = length of truss member SR = Stress Ratio, allowable stress/actual stress,

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Morphing aircraft wings offer great potential benefits of achieving multi mission capability as well as high maneuverability under different flight conditions. However, they present many design challenges in the form of conflicting design requirements. The current research aims to develop design methodologies for the design of a morphing aircraft wing. Focus of this work is on developing an internal mechanism of the wing that can produce the desired wing shape change.This paper presents a design methodology that employs planar unit cells of pre-determined shape and layout as the internal wing structure for achieving the desired wing shape change. This method is particularly useful in cases where the desired morphing is two-dimensional in nature. In such cases, intuitive cell designs such as diamond or hexagonal shaped cells may be used in layouts that achieve desired wing morphing. The shape change depends on the cell shape as well as cell arrangement in the design domain.In this paper, a design based on the TSCh wing (NextGen Aeronautics Inc.) using cellular mechanisms to achieve a twodimensional wing shape change is discussed. Additionally, a reeling mechanism for achieving cable actuation is presented.

Compliant mechanism amplifiers are often used in conjunction with piezoelectric actuators since they do not incur displacement losses that frequently occur in pin-jointed mechanisms. In this paper the design of a compliant mechanism amplifier and piezoelectric stack actuator is presented. The application is an inertially stabilized rifle (INSTAR) in which the compliant actuator is used to make small adjustments in the position of the barrel. A topology optimization method is used to obtain the initial topology of the compliant mechanism, followed by detailed finite element analysis. The effect of geometry parameters, material selection, and epoxy bonding layers in the piezoelectric actuator are studied. A prototype actuator is fabricated and characterized experimentally. The force and displacement performance of the prototype actuator are shown to exceed the design specifications for the INSTAR application.

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