Experimental Analysis of a Planar Reconfigurable Mechanism With a Variable Joint

Previously a specific planar reconfigurable mechanism with a variable joint (RRRR1 -RRRP2 Mechanism) was dynamically modeled. The RRRR-RRRP Mechanism functions as a RRRR mechanism in one configuration and as a in RRRP mechanism the other. The kinematics and kinetics of the RRRP and RRRR configurations were previously analyzed with a Lagrangian approach. The developed equations of motion will be validated with a physical prototype in this paper. In addition, a simplified model of the RRRR-RRRP Mechanism is also developed and compared to the experimental results. The experimental angular position of each joint on the RRRR-RRRP Mechanism will be compared to the model position analysis. Particular attention will be given to the transition point when the physical mechanism changes from an RRRR mechanism to RRRP mechanism and vice versa as it is vital to knowing this point for optimal control of the mechanism.

Behavior of Congruent Tessellation Stacks Under Torsional Loading

The combination of several layers of rigidly foldable tessellations into can produce cellular material stacks with interesting properties, especially if the resulting stack preserves the mobility of its constituting layers. To achieve this, the construction of functional joining and hinging concepts need to be developed. This paper presents a simple solution to effectively joining different 1-DOF (degree of freedom) tessellation layers. The mechanical properties of the resulting structures under torsional loads are evaluated using finite element analysis, and their potential use as structural mechanisms is discussed.

Design and Mobility Analysis of Large Deployable Mechanisms Based on Plane-Symmetric Bricard Linkage

In this paper, a class of large deployable mechanisms constructed by plane-symmetric Bricard linkage is presented. The plane-symmetric Bricard linkage is a closed-loop over-constrained spatial mechanism composed of six hinge-jointed bars, which has one plane of symmetry during its deployment process. The kinematic analysis of the linkage is presented from the perspectives of geometric conditions, closure equations and degree of freedom. The results illustrates that the linkage has one degree of freedom, and it can be deployed from the folded configuration to one rectangle plane. Therefore, the plane-symmetric Bricard linkage can be used to construct lager deployable mechanism as basic deployable unit. Four plane-symmetric Bricard linkages can be assembled to a quadrangular module by sharing the vertical bars of adjacent units. The module is a multi-loop deployable mechanism and has one degree of freedom by the mobility analysis. Large deployable mast, deployable plane truss and deployable ring are built by a plurality of plane-symmetric Bricard linkages. The computer-aided design models for typical examples are built to illustrate their feasibility and validate the analysis and design methods.

Structural Design and Forming Method of Single-Curved Surface Structure Based on Miura-Origami

With the advantage of high adaptability, Miura-origami structure with curvature shows various engineering applications such as a sandwich between two stiff facings with curvature requirements and structural support to form a circular tube. In this research, a forming method of polymer circular tube with single-curved surface origami expressed by five parameters was established and its corresponding theory was solved considering forming rationality in actual manufacturing. The components of circular tube were fabricated by the vacuum forming process and then spliced together. We conducted numerical simulation to analyze the structural performance of the tube with five parameters and shown that these parameters have a great influence on energy absorbed performance. Finally, a male mold of a part with Arc Miura-origami structure was designed and fabricated. The parts with Arc Miura-origami were manufactured using vacuum forming process and then spliced and bonded together into a two-layer tube. This research may provide a method to design and fabricate Miura-origami structure with high efficiency and quality.

A Hexagonal Prism Folding for Membrane Packaging Based on Concepts of Finite Rigid Motion and Kinematic Synthesis

This paper discusses the use of concepts of finite rigid body kinematics as well as kinematic synthesis in non-rigid, engineering folding problems. The exemplary task consists in designing a folding pattern, which allows to fold a circular sheet from a flat unfolded state into a prescribed compact spatial configuration that forms a hexagonal prism. Other two-configuration design problems may be found for instance in space applications where membranes in tensegrity reflector antennas need to be stowed in a spacecraft. The folding motion could be actuated using an appropriately designed linkage mechanism attached to the membrane, which, however, is not considered in this paper. The specific result of this work is a creative but systematic and computational procedure for crease pattern design. The approach is essentially based on the relative kinematics equations of serial kinematic chains and the finite position synthesis of linkage building blocks. These techniques sucessively combine to segment a flat bounded surface, such that it can reach the prescribed spatial configuration.

Kinematic Study of a Soft-and-Rigid Robotic Digit for Rehabilitation and Assistive Applications

This paper presents the kinematic study of a pneumatically actuated soft-and-rigid robotic digit designed to be used in exoskeleton-based hand rehabilitation and assistive applications. The soft-and-rigid robotic digit is comprised of three inflatable bellow-shaped structure sections (soft sections) and four semi-rigid sections in an alternating order which correspond to the anatomy of a human finger. The forward and backward bending motions at each soft section (joint) are generated by pressure and vacuum actuation, respectively. The goal here is to investigate the compatibility of the soft robotic digit’s kinematic parameters such as range of motion, center of rotation, and lengthening at the joints with the required anatomical motion of the human finger to ensure proper function and safe interaction. The soft robotic digits were fabricated using silicone rubber materials in a compression molding process for the experimental study. The kinematic parameters of both a human and soft robotic index finger were measured using a motion capture system. The obtained results show that the robotic digit was able to provide the required range of motion: 0–90° at the metacarpophalangeal (MCP) joint, 0–100° at the proximal interphalangeal (PIP) joint, and 0–70° at the distal interphalangeal (DIP) joint. Furthermore, the data show the center of rotation of each soft section (robotic joint) was remotely coincident with that of the corresponding index finger. The lengthening of the three soft sections of the robotic digit were measured to be 7mm, 7mm, and 2mm for the MCP, PIP, and DIP, respectively. The corresponding values for the dorsal skin lengthening of a human index finger is 11mm, 15mm, and 5mm and are longer than the achieved lengthening in the robotic digit.

Design and Static Analysis of Elastic Force and Torque Limiting Devices for Safe Physical Human-Robot Interaction

This paper presents the static analysis of elastic force and torque limiters that aim at limiting the forces that a robotic manipulator can apply on its environment. First, the design of one-degree-of-freedom force and torque limiting mechanisms is presented. It is shown that a single elastic component (spring) can be used to provide a prescribed preload and stiffness in both directions of motion along a given axis. Then, the mechanisms are analyzed in order to determine the nonlinear relationships between the motion of the mechanism and the extension of the spring. These relationships can then be used in the design of the force and torque limiters. Finally, the force capabilities of the mechanisms are investigated and numerical results are provided for example designs.

Solution Region Synthesis Method for Six Positions Synthesis of 5-SS Spatial Linkage

This paper presents a systematic approach to perform the dimensional synthesis of spatial 5-SS (spherical-spherical) link-ages for six specified positions of the end-effector. The dimensional synthesis equations for a SS link are formulated and solved. We synthesize five SS links to connect the base and end-effector, and then obtain the one-degree-of-freedom spatial 5-SS linkage, which can move through six specified positions. We use the solution region method to build the planar solution region expressing the linkages, due to there are infinite linkages for six positions synthesis. It is convenient to select the linkages from the solution region for designers. The applicability of the proposed approach is illustrated by the example.

MeKin2D: Suite for Planar Mechanism Kinematics

MeKin2D is a collection of subroutines for kinematic simulation of planar linkages using a modular approach, for synthesis and analysis of disk-cam mechanisms with various types of followers, and for involute gear generation. The original set of subroutines accompanies as supplementary materials a book by this same author released in 2014. These, as well as other subroutines added since the book has been released are presented in the paper, together with examples accompanied by animations.

Topological Reconfigurations of Bennett-Based Linkages

This paper presents the methodology of topological reconfigurations with composite Bennett linkages. A new family of diverse reconfigurable Bennett linkages is discovered. The framework is based on the parallel combination of Bennett chains. Two kinds of expansible frameworks are addressed in detail. The topological reconfigurations of Bennett-based linkage with multiple working-phases can be attained from the composite framework of the compositing Bennett chain by eliminating the revolute angle between its adjacent links. Several examples are provided not only to interpret the construction of extant ones but also to develop more complicated ones. The proposed method systematically discovers all possible permutations of number of joints and links for topological variants of the resultant linkages. The spatial linkage built based on the presented methodology may be either overconstrained or underconstrained because some of their DOFs may not follow the mobility as predicted by Chebychev-Grübler-Kutzbach criterion.