In this paper, we present a deformable wheel robot using the ball-shaped waterbomb origami pattern, so-called magic-ball pattern. The magic-ball origami pattern is a well-known pattern that changes its shape from a long cylindrical tube to a flat circular tube. By using this special structure, a wheel with mechanical functionalities can be achieved without using many mechanical parts. Moreover, because of the characteristic that the structure constrains its own movement, it is possible to control the whole shape of the wheel using only few actuators. And also, from analysis of the wheel structure in kinematic model, the performance of the wheel and determine the condition for actuators can be predicted. We think that the proposed design for the deformable wheel shows the possibility of using origami structure as a functional structure with its own mechanism.
A wheel drive mechanism is simple, stable, and efficient, but its mobility in unstructured terrain is seriously limited. Using a deformable wheel is one of the ways to increase the mobility of a wheel drive robot. By changing the radius of its wheels, the robot becomes able to pass over not only high steps but also narrow gaps. In this article, we propose a novel design for a variable-diameter wheel using an origami-based soft robotics design approach. By simply folding a patterned sheet into a wheel shape, a variable-diameter wheel was built without requiring lots of mechanical parts and a complex assembly process. The wheel's diameter can change from 30 to 68 mm, and it is light in weight at about 9.7 g. Although composed of soft materials (fabrics and films), the wheel can bear more than 400 times its weight. The robot was able to change the wheel's radius in response to terrain conditions, allowing it to pass over a 50-mm gap when the wheel is shrunk and a 50-mm step when the wheel is enlarged.
Self-folding origami requires a low-profile actuator to be embedded in a sheet of paper-like planar material. Various actuation methods have been employed to actively fold such sheets. This paper presents a torsion shape-memory alloy (SMA) wire actuator embedded in patterned origami structures that actively folds the origami by twisting the SMA wire. A simple wire is aligned with the fold line, and each end is fixed to a facet. The twisting of the wire directly rotates the facets. This method has the advantage of using an easily available wire SMA and the advantage of a flat form factor similar to that of sheet SMA. Generally, SMA wire is used in a linear manner or as a spring. The torsion SMA wire presented in this paper is trained to generate torsional force when heated. The amount of rotation depends on the length of the wire; a 200-μm-diameter SMA wire 12 mm in length can induce 540° rotation. SMA wires are arranged in pairs side by side to rotate the facets in both directions. Maximum torque of 70 mNcm is generated in this antagonistic arrangement. The torsion SMA wire actuators enable a novel design for a programmable folding sheet that is easily manufactured and exhibits fast folding and unfolding.
The unique characteristics of origami to realize 3-D shape from 2-D patterns have been fascinating many researchers and engineers. This paper presents a fabrication of origami patterned fabric wheels that can deform and change the radius of the wheels. PVC segments are enclosed in the fabrics to build a tough and foldable structure. A special cable driven mechanism was designed to allow the wheels to deform while rotating. A mobile robot with two origami wheels has been built and tested to show that it can deform its wheels to overcome various obstacles.
One of the major problems in utilizing origami structures is ensuring variable stiffness; a deployable structure needs to become stiff or flexible according to the requirements of its use in an application. In this study, we present a self-deploying tubular origami mechanism that switches between two distinctive states: small and flexible at its normal state and rigid and stiffened at a locked state. By embedding compact torsional SMA actuators into the mechanism in a novel way through stitching, the process of deploying from the normal to the locked state proceeds in a simple and low-profile manner. With global heating, the torsional SMA wires activate a buckling effect that draws a radical change of folding line from one diagonal to another in every unit tile of the tube, creating axial stiffness. The activated structure, which weighs only 2.9 g, can endure a load of 2.7 kg or more. Additionally, since it does not require bulky actuators, this origami structure can be highly mobile and small in size. This novel origami mechanism is expected to be useful in a wide variety of applications, such as aerospace equipment, mobile architecture, and medical devices, especially those used in minimally invasive surgery (MIS).
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