A foldable arm is one of the practical applications of folding. It can help mobile robots and unmanned aerial vehicles (UAVs) overcome access issues by allowing them to reach into confined spaces. The origami-inspired design enables a foldable structure to be lightweight, compact, and scalable while maintaining its kinematic behavior. However, the lack of structural stiffness has been a major limitation in the practical use of origami-inspired designs. Resolving this obstacle without losing the inherent advantages of origami is a challenge. We propose a solution by implementing a simple stiffening mechanism that uses an origami principle of perpendicular folding. The simplicity of the stiffening mechanism enables an actuation system to drive shape and stiffness changes with only a single electric motor. Our results show that this design was effective for a foldable arm and allowed a UAV to perform a variety of tasks in a confined space.

An origami-inspired, self-locking robotic arm that can be folded flat.

Solar sail technology—A state of the art review

From stadium covers to solar sails, we rely on deployability for the design of large-scale structures that can quickly compress to a fraction of their size1–4. Historically, two main strategies have been used to design deployable systems. The first and most frequently used approach involves mechanisms comprising interconnected bar elements, which can synchronously expand and retract5–7, occasionally locking in place through bistable elements8,9. The second strategy makes use of inflatable membranes that morph into target shapes by means of a single pressure input10–12. Neither strategy, however, can be readily used to provide an enclosed domain that is able to lock in place after deployment: the integration of a protective covering in linkage-based constructions is challenging and pneumatic systems require a constant applied pressure to keep their expanded shape13–15. Here we draw inspiration from origami—the Japanese art of paper folding—to design rigid-walled deployable structures that are multistable and inflatable. Guided by geometric analyses and experiments, we create a library of bistable origami shapes that can be deployed through a single fluidic pressure input. We then combine these units to build functional structures at the metre scale, such as arches and emergency shelters, providing a direct route for building large-scale inflatable systems that lock in place after deployment and offer a robust enclosure through their stiff faces. Origami-inspired multistable structures that can be inflated from flat to three dimensions have been designed; a library of foldable shapes is created and then combined to build metre-scale functional structures.

Multistable inflatable origami structures at the metre scale.

Large-scale deployable solar panels are crucial for certain engineering applications. However, a complex network of actuators and power supplies are usually required to achieve deployment, and can be prone to failure. The single-degree-of-freedom design proposed here embeds shape-memory polymers within an elastic origami substrate, to achieve self-deployment through temperature change. The unexpected bifurcation during folding is studied by examining strain energy as a function of dihedral angle. By optimizing the geometry, tenfold self-deployment is achieved in under one minute. The results could benefit space exploration, as well as solar power generation in inaccessible areas.

https://link.aps.org/pdf/10.1103/PhysRevApplied.11.064069

Autonomous Deployment of a Solar Panel Using Elastic Origami and Distributed Shape-Memory-Polymer Actuators

Morphology plays an important role in behavioral and locomotion strategies of living and artificial systems. There is biological evidence that adaptive morphological changes can not only extend dynamic performances by reducing tradeoffs during locomotion but also provide new functionalities. In this article, we show that adaptive morphology is an emerging design principle in robotics that benefits from a new generation of soft, variable-stiffness, and functional materials and structures. When moving within a given environment or when transitioning between different substrates, adaptive morphology allows accommodation of opposing dynamic requirements (e.g., maneuverability, stability, efficiency, and speed). Adaptive morphology is also a viable solution to endow robots with additional functionalities, such as transportability, protection, and variable gearing. We identify important research and technological questions, such as variable-stiffness structures, in silico design tools, and adaptive control systems to fully leverage adaptive morphology in robotic systems.

Adaptive Morphology: A Design Principle for Multimodal and Multifunctional Robots

Ultralight Deployable Booms for Solar Sails and Other Large Gossamer Structures in Space

The 3-step DLR–ESA Gossamer road to solar sailing

Gossamer-1: Mission concept and technology for a controlled deployment of gossamer spacecraft

Deployable structures are required to either enable orbit transfer of very large structure or to make the orbit transfer of medium and small size structures more affordable Hereby, deployable booms are basic building blocks of such deployable structures 
DLR is providing a concept for deployable booms that utilize very thin CFRP material and which can be stowed by coiling 

The given paper introduces the concept of the CFRP booms and discusses the problems of their self deployment tendency Furthermore, different mechanisms are presented that are able to control the deployment Tests under artificial zero-g environment have been conducted to verify the applicability of the control concepts Hence, the paper also gives insight in objectives, setup and the results of the experiment as well as a final evaluation of the concepts Finally, an outlook on current and future projects that use the introduced booms or equivalent systems is given

Deployable Composite Booms for Various Gossamer Space Structures

DE-ORBIT SAIL is a cubesat based drag sail for the de-orbiting of satellites in a low earth orbit It is scheduled for launch in late 2014 and will deploy a 25m² sail supported by deployable carbon fiber booms designed and manufactured by DLR This boom possesses a closed cross-section formed by two omega-shaped half-shells Due to this cross-sectional design the boom features a high torsional stiffness Thereby a high bending strength is achieved compared to other boom concepts for similar applications as the boom is less sensitive to flexural torsional buckling The boom concept selection is based on a detailed analysis of three types of deployable booms which differ in their cross-sectional design From this analysis the double-omega boom was determined as most suited for DE-ORBIT SAIL For the manufacturing of the booms a novel method is used where the booms are manufactured in an integral way in one piece

/pdf/the-boom-design-of-the-de-orbit-sail-satellite-4eonscq4iv.pdf

Marco Straubel

Papers

Ultralight Deployable Booms for Solar Sails and Other Large Gossamer Structures in Space

The 3-step DLR–ESA Gossamer road to solar sailing

Gossamer-1: Mission concept and technology for a controlled deployment of gossamer spacecraft

Deployable Composite Booms for Various Gossamer Space Structures

The Boom Design of the De-Orbit Sail Satellite