Programmable Kirigami: Cutting and Folding in Science, Technology and Architecture

This paper investigates the potential of kirigami-folding with the addition of strategically placed cuts at multiple scales through both computational design and physical prototyping. The study develops a novel method and workflow for generating two-dimensional (2D) kirigami patterns developed from doubly curved three-dimensional (3D) surfaces (Inverse process). Corresponding simulations of the kirigami folding motion from 2D pattern to 3D goal shape are presented (Forward process). The workflow is based on a reciprocal feedback loop including computational design, finite element analysis, dynamic simulation and physical prototyping. Extended from previous research on kirigami geometry, this paper incorporates material properties into the folding process and successfully develops active kirigami models from the DNA scale to human scale. The results presented in this paper provide an attractive method for kirigami design and fabrication with a wide range of scales and applications.

A Novel 1-DOF Deployable Mechanism for Parabolic Cylindrical Surface Approximation

This paper presents a novel deployable mechanism for approximating the parabolic cylindrical surface. The proposed mechanism, which can deploy and fold synchronously in the radial and axial directions, is constructed by double four-bar linkages and scissor linkages. In the fully deployed configuration, the mechanism can approximate a cylindrical surface. It can also be folded compactly into a bundle. The radial and axial deployable mechanisms are described and their position kinematics are solved. A synchronous mechanism is designed to ensure the synchronous movement of the radial and axial mechanisms. Geometric parameters of the mechanism for approximating a given parabolic cylindrical surface are obtained. The magnification ratio of the designed mechanism is calculated. The best choice of actuator is determined through static-load analysis.

A Shape Memory Alloy Driven Crawling Robot Utilizing a Bistable Mechanism

Shape memory alloys (SMA) can generate displacement and force via phase change and have been widely used as actuators in robotics due to their light weight and ease of control. This paper proposes a SMA-driven crawling robot which activates antagonistic SMA springs alternately through a mechanical on-off logic switching system. By introducing a cam based bistable mechanism, elastic energy is stored and released to regulate the reciprocating motion of a slider in the robot. Meanwhile, the robot feet with anisotropic friction surface are employed to convert the reciprocating motion of the slider to unidirectional locomotion of the robot. The static model of the SMA and control logic of the robot are analyzed and validated through experiments.

Integrated Origami-String System

Origami-inspired mechanical systems are mostly composed of two-dimensional elements, a feature inherited from paper folding. However, do we have to comply with this restriction on our design space? Would it be more approachable to achieve desired performance by integrating elements of different abstract dimensions? In this paper, we propose an integrated structural system consisting of both two-dimensional and one-dimensional elements. We attach elastic strings onto an origami design to modify its mechanical behavior and create new features. We show that, by introducing elastic strings to the recently proposed Morph pattern, we can obtain bistable units with programmable energy landscape. The behavior of this integrated origami-string system can be described by an elegant formulation, which can be used to explore its rich programmability.

A Novel Variable Stiffness Compliant Robotic Gripper Based on Layer Jamming

In this paper, we present a novel compliant robotic gripper with three variable stiffness fingers. While the shape morphing of the grippers is cable-driven, the stiffness variation is enabled by layer jamming. The inherent flexibility makes compliant grippers suitable for tasks such as grasping soft and irregular objects. However, their relatively low load capacity due to low structural stiffness limits their applications. Variable stiffness robotic grippers have the potential to address this challenge as their stiffness can be tuned on demand based on the needs of tasks. Layer jamming is an emerging method for variable stiffness due to its advantages of light weight, simple and quick actuation. In our design, the compliant backbone of the fingers is made of 3d printed PLA material. Four thin film materials are attached to each side of the skeleton. The working process of the robotic gripper follows two basic steps. First, the compliant skeleton is bent to a desired shape by actuating a tension cable via a servo motor. Second, upon application of a negative pressure by a vacuum pump, the finger is stiffened up owing to the increasing of the friction between contact surfaces of layers preventing their relative movement. Since the structural stiffness of the fingers is increased, their load capacity will be increased proportionally. When the air pressure is sufficiently large, the morphed shape can even be locked (no slipping). Test for stiffness of individual finger and load capacity of the robotic gripper are conducted to validate capability of the design. The results showed a 69-fold increase in stiffness of individual finger and a 30-fold increase in gripper’s load capacity.

Synthesizing Mechanical Chains for Morphing Between Spatial Curves

This work investigates the kinematic synthesis methodology for designing a chain of three-dimensional bodies to match a set of arbitrary spatial curves. The bodies synthesized can be one of three types: a rigid segment, a helical segment with constant curvature and torsion but varying length, and a growth segment that maintains its geometry but may be scaled to become larger or smaller. To realize mechanical chains, only rigid and helical segments are used. After designing the segments, they may be aligned with the original spatial curves with their ends connected via an optimization. For two curves, these connections may be made with revolute joints to obtain high accuracy. For three or more curves, spherical joint connections allow for the best accuracy. To compare curves as is useful in morphometry, all three segment types may be employed. In this case, an accurate description of the changes between curves is important, and optimizing to connect the segments is not needed. The procedure for redefining the curves in a way that the techniques in this paper may be applied, as well as the methodologies for synthesizing the three segment types are presented. Examples include a continuum robot problem and the morphometric analyses of chochlear curves and the lambdoidal suture. This work extends the established planar techniques for synthesizing mechanisms and addressing morphometric issues that are motivated with curves in two-dimensions.

Kinematic Modeling of Origami-Based Forcep Designs

In the design of practical grasping tools such as forceps or grippers, it may be desirable to create a compact, lightweight, and easily manufactured tool. Origami inspired designs can help simplify gripper manufacturing to a single planar sheet of material while still allowing for deployment and actuation. Inflatable structures can reduce weight and be compacted. This paper explores the design of an inflatable, deployable, action origami inspired gripper through the development of a predictive model, prototype fabrication, and preliminary design assessments.

Extended Camus Theory and Higher Order Conjugated Curves

According to Camus’ theorem, for a single DOF 3-body system with the three instant centers staying coincident, a point embedded on a body traces a pair of conjugated curves on the other two bodies. This paper discusses a fundamental issue not addressed in Camus’ theorem in the context of higher order curvature theory. Following the Aronhold-Kennedy theorem, in a single degree-of-freedom three-body system, the three instant centers must lie on a straight line. This paper proposes that if the line of the three instant centers is stationary (i.e. slide along itself), on the line of the instant centers a point embedded on a body traces a pair of conjugated curves on the other two bodies. Another case is that if the line of the three instant centers rotate about a stationary point, the stationary point embedded on the body also traces a pair of conjugated curves on the other two bodies. The paper demonstrates the use of instantaneous invariants to synthesize such a three-body system leading to a conjugate curve-pair generation. It is a supplement or extension of the Camus’ theorem. The Camus’ theorem may be regarded as a special singular case, in which all three instant centers are coincident.

Geometric Simulation for Thick Origami

Origami is an art that creates a three-dimensional (3D) shape only by folding. This capability has drawn much research attention recently, and its applied or inspired designs are utilized in various engineering applications. Most current designs are based on the existing origami patterns and their known deformation, but origami patterns are universally designed for zero-thickness like a paper. To extend the designs for engineering applications, simulation of origami is needed to help designers explore and understand the designs, and the simulation must take the material thickness into account. With the observation that origami is mainly a geometry design problem, this paper develops a geometric simulation for thick origami, similar to a pseudo-physics approach. The actuation, constraints, and mountain/valley assignments of origami are also incorporated in the geometric formulation. Experimental results show that the proposed method is efficient and accurate. It can simulate successfully the bistable property of a waterbomb base, two different action origami, and the elasticity of origami panels when they are not rigid.

On the Deployment of Multistable Kresling Origami-Inspired Structures

Origami designs have attracted significant attention from researchers seeking to develop new types of deployable structures due to their ability to undergo large and complex yet predictable shape changes. The Kresling pattern, which is based on a natural accumulation of folds and creases during the twist-buckling of a thin-walled cylinder, offers a great example for the design of deployable systems that expand uniaxially into tubes or booms. However, much remains to be understood regarding the characteristics of Kresling-based deployable systems, and their dynamics during the deployment process remain largely unexplored. Hence this research investigates the deployment of Kresling origami-inspired structures, employing a full six-degree-of-freedom truss-based model to study their dynamics under different conditions. Results show that tuning the initial rotation angle of a structure gives rise to several qualitatively distinct mechanical properties and stability characteristics, each of which has different implications for the design of the deployable systems. Dynamic analyses reveal the robustness of Kresling structures to out-of-axis perturbations while remaining compliant in the axial direction. These findings suggest that Kresling-based designs can form the basis for the development of new types of deployable structures and systems with tunable performance.