Cylindrical developable mechanisms are devices that conform to and emerge from a cylindrical surface. These mechanisms can be formed or cut from the cylinder wall itself. This paper presents a study on adapting traditional hinge options to achieve revolute motion in these mechanisms. A brief overview of options is given, including classical pin hinges, small-length flexural pivots, initially curved beams, and an adaptation of the membrane thickness-accommodation technique. Curved lamina emergent torsional (LET) joints are then evaluated in detail, and a thin-walled modeling assumption is checked analytically and empirically. A small-scale cylindrical developable mechanism is then evaluated with Nitinol curved LET joints.

The regional sandwiching of compliant sheets (ReCS) technique presented in this work creates flat-foldable, rigid-foldable, and self-deploying thick origami-based mechanisms. Regional sandwiching of the compliant sheet is used to create mountain-valley assignments for each fold about a vertex, constraining motion to a single branch of folding. Strain energy in deflected flexible members is used to enable self-deployment. This work presents the methods to design origami-based mechanisms using the ReCS technique, including volume trimming at the vertex of the compliant sheet and of the panels used in the sandwich. Three physical models, a simple single fold mechanism, a degree-four vertex mechanism, and a full tessellation, are presented to demonstrate the ReCS technique using acrylic panels with spring and low-carbon steels. Consideration is given to the risk of yielding of the compliant sheet due to parasitic motion with possible mitigation of yielding by decreasing the thickness of the sheet.

Dielectric elastomer (DE), as a group of electro-active polymers, has been widely used in soft robotics due to its inherent flexibility and large induced deformation. As sustained high voltage is needed to maintain the deformation of DE, it may result in electric breakdown for a long-period actuation. Inspired by the bistable mechanism which has two stable equilibrium positions and can stay at one of them without energy consumption, two bistable dielectric elastomer actuators (DEAs) including a translational actuator and a rotational actuator are proposed. Both the bistable actuators consist of a double conical DEA and a buckling beam and can switch between two stable positions with voltage. In this paper, the analytical models of the bulking beam and the conical DEA are presented first, and then the design method is demonstrated in terms of force equilibrium and moment equilibrium principle. The experiments of the translational bistable DEA and the rotational bistable DEA are conducted, which show that the design method of the bistable DEA is effective.

Herein, we discuss the folding of highly compliant origami structures—“Soft Origami.” There are benefits to be had in folding compliant sheets (which cannot self-guide their motion) rather than conventional rigid origami. Example applications include scaffolds for artificial tissue generation and foldable substrates for flexible electronic assemblies. Highly compliant origami has not been contemplated by existing theory, which treats origami structures largely as rigid or semirigid mechanisms with compliant hinges—“mechanism-reliant origami.” We present a quantitative metric—the origami compliance metric (OCM)—that aids in identifying proper modeling of a homogeneous origami structure based upon the compliance regime it falls into (soft, hybrid, or mechanism-reliant). We discuss the unique properties, applications, and design drivers for practical implementation of Soft Origami. We detail a theory of proper constraint by which an ideal soft structure's number of degrees-of-freedom may be approximated as 3n, where n is the number of vertices of the fold pattern. Buckling and sagging behaviors in very compliant structures can be counteracted with the application of tension; we present a method for calculating the tension force required to reduce sagging error below a user-prescribed value. Finally, we introduce a concept for a scalable process in which a few actuators and stretching membranes may be used to simultaneously fold many origami substructures that share common degrees-of-freedom.

A great number of kinematic, kinetostatic, and dynamic models of human diarthrodial joints, such as the hip, the knee, and the ankle, have been presented in the literature. On the contrary, comprehensive models of the lower limb are lacking and often oversimplify its anatomical structures by considering only 2D motion. This paper will focus on the 3D kinematic model of the articulation that involves four bones: the tibia, fibula, talus, and calcaneus. In particular, a new spatial equivalent mechanism with one degree of freedom is proposed for the passive motion simulation of this anatomical complex. The geometry of the mechanism is based on the main anatomical structures, namely the talus, the tibia, and the fibula bones at their interface, on the main ligaments of the ankle joint, and on the interosseus membrane of the leg. An iterative refinement process is presented, that provides the optimal geometry of the mechanism which allows the best fitting of simulation versus measurement data. Simulation results show the efficiency of the proposed mechanism that is believed to play an important role for future developments of models of the whole human lower limb.

In this paper, a locomotion mechanism for mobile robots inspired by how single celled organisms use cytoplasmic streaming to generate pseudopods for locomotion is presented. Called the whole skin locomotion, it works by way of an elongated toroid, which turns itself inside out in a single continuous motion, effectively generating the overall motion of the cytoplasmic streaming ectoplasmic tube in amoebae. With an elastic membrane or a mesh of links acting as its outer skin, the robot can easily squeeze between obstacles or under a collapsed ceiling and move forward using all of its contact surfaces for traction, even squeezing itself through holes of a diameter smaller than its nominal width. Therefore this motion is well suited for search and rescue robots that need to traverse over or under rubble, or for applications where a robot needs to enter into and maneuver around tight spaces such as for robotic endoscopes. This paper summarizes the many existing theories of amoeboid motility mechanisms and examines how these can be applied on a macroscale as a mobile robot locomotion concept, illustrating how biological principles can be used for developing novel robotic mechanisms. Five specific mechanisms are introduced, which could be implemented to such a robotic system. Descriptions of an early prototype and the preliminary experimental and finite element analysis results demonstrating the feasibility of the whole skin locomotion strategy are also presented, followed by a discussion of future work.