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Accepted Manuscripts

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research-article  
Nir Shvalb, Tal Grinshpoun and Oded Medina
J. Mechanisms Robotics   doi: 10.1115/1.4035532
A configuration of a mechanical linkage is defined as regular if there exist a subset of actuators with their corresponding Jacobian columns spans the gripper's velocity space. All other configurations are defined in the literature as singular configurations. Consider mechanisms with grippers' velocity space ℝm. We focus our attention on the case where m Jacobian columns of such mechanism span ℝm while all the rest are linearly dependent. These are obviously an undesirable configuration although formally they are defined as regular. We define an optimal-regular configuration as such that any subset of m actuators spans an m dimensional velocity space. Since this densely constraints the work space, a more relaxed definition is needed. We therefore, introduce the notion of k-singularity of a redundant mechanism which means that rigidifying k actuators will result in an optimal-regularity. We introduce an efficient algorithm to detect a k-singularity, give some examples for cases where m=2,3 and demonstrate our algorithm efficiency.
TOPICS: Robots, Arches, Linkages, Actuators, Algorithms, Grippers
Design Innovation Paper  
Lee-Huang Chen, Kyunam Kim, Ellande Tang, Kevin Li, Richard House, Edward Liu Zhu, Kimberley Fountain, Alice M. Agogino, Adrian Agogino, Vytas Sunspiral and Erik Jung
J. Mechanisms Robotics   doi: 10.1115/1.4036014
This paper presents the design, analysis and testing of a fully actuated modular spherical tensegrity robot for co-robotic and space exploration applications. Robots built from tensegrity structures (composed of pure tensile and compression elements) have many potential benefits including high robustness through redundancy, many degrees of freedom in movement and flexible design. However, to fully take advantage of these properties a significant fraction of the tensile elements should be active, leading to a potential increase in complexity, messy cable and power routing systems and increased design difficulty. Here we describe an elegant solution to a fully actuated tensegrity robot: The TT-3 (version 3) tensegrity robot, developed at UC Berkeley, in collaboration with NASA Ames, is a lightweight, low cost, modular, and rapidly prototyped spherical tensegrity robot. This robot is based on a ball-shaped six-bar tensegrity structure and features a unique modular rod-centered distributed actuation and control architecture. This paper presents the novel mechanism design, architecture and simulations of TT-3, the first untethered, fully actuated cable-driven six-bar tensegrity spherical robot ever built and tested for mobility. Furthermore, this paper discusses the controls and preliminary testing performed to observe the system's behavior and performance.
TOPICS: Robots, Design, Tensegrity, Tensegrity structures, Cables, Testing, Compression, Robustness, Collaboration, NASA, Simulation, Redundancy (Engineering), Degrees of freedom, Mechanical admittance, Engineering simulation, Robotics
research-article  
Hessein Ali, Andrew P. Murray and David H. Myszka
J. Mechanisms Robotics   doi: 10.1115/1.4035985
This paper presents a methodology for synthesizing planar linkages to approximate any prescribed periodic function. The mechanisms selected for this task are the slider-crank and the geared five-bar with connecting rod and sliding output (GFBS), where any number of double-crank (or drag-link) four-bars are used as drivers. A slider-crank mechanism, when comparing the input crank rotation to the output slider displacement, produces a sinusoid-like function. Instead of directly driving the input crank, a drag-link four-bar may be added to drive the crank from its output via a rigid connection between the two. Driving the input of the added four-bar results in a function that modifies the sinusoid-like curve. This process can be continued through the addition of more drag-link mechanisms to the device, progressively altering the curve toward any periodic function with a single maximum. For periodic functions with multiple maxima, a GFBS is used as the terminal linkage added to the chain of drag-link mechanisms. The synthesis process starts by analyzing one period of the function to design either the terminal slider-crank or terminal GFBS. MATLAB's fmincon command is then utilized as the four-bars are added to reduce the structural error between the desired function and the input-output function of the mechanism. Mechanisms have been synthesized in this fashion to include a large number of links that are capable of closely producing functions with a variety of intriguing features.
TOPICS: Linkages, Drag (Fluid dynamics), Rotation, Chain, Design, Displacement, Errors
research-article  
Shun-Kun Zhu and Yue-Qing Yu
J. Mechanisms Robotics   doi: 10.1115/1.4035986
The pseudo-rigid-body model (PRBM) used to simulate compliant beams without inflection point is well-developed. However, the problem of modeling flexural beams with inflection points with PRBM remains unsolved. In this paper, two types of PRBMs are proposed to simulate the large deflection of flexible beam with an inflection point in different configurations. These models are composed of five rigid links connected by three joints added with torsional springs and one hinge without spring presenting the inflection point in the flexural beam. The characteristic radius factors of the PRBMs are determined by solving the objective function established according to the relative angular displacement of the two rigid links jointed by the hinge via genetic algorithm. The spring stiffness coefficients are obtained using a linear regression technique. The effective ranges of these two models are determined by the load index. The numerical result shows that both the tip locus and inflection point of the flexural beam with single inflection can be simulated precisely using the model proposed in this paper.
TOPICS: Stress, Hinges, Modeling, Deflection, Displacement, Genetic algorithms, Springs, Stiffness, Compliant mechanisms
research-article  
Priyanshu Agarwal and Ashish D. Deshpande
J. Mechanisms Robotics   doi: 10.1115/1.4035987
Torque control of small-scale robotic devices such as hand exoskeletons is challenging due to the unavailability of miniature and compact bidirectional torque actuators. In this work, we present a miniature Bowden-cable-based series elastic actuator (SEA) using helical torsion springs. The 3D printed SEA is 38 mm × 38 mm × 24 mm in dimension and weighs 30 g, excluding motor which is located remotely. We carry out a through experimental testing of our previously presented linear compression spring SEA (LC-SEA) [9] and helical torsion spring SEA (HT-SEA) and compare the performance of the two designs. Performance characterization on a test rig shows that the two SEAs have adequate torque source quality (RMSE < 12 % of peak torque) with high torque fidelities (>97 % at 0.5 Hz torque sinusoid) and force tracking bandwidths of 2.5 Hz and 4.5 Hz (@ 0.2 Nm), respectively, which make these SEAs suitable for our application of a hand exoskeleton.
TOPICS: Actuators, Robotics, Seas, Torque, Springs, Torsion, Exoskeleton devices, Torque control, Performance characterization, Engines, Dimensions, Motors, Cables, Testing, Compression
research-article  
Michael Anson, Aliakbar Alamdari and Venkat Krovi
J. Mechanisms Robotics   doi: 10.1115/1.4035988
Cable-driven parallel manipulators (CDPM) potentially offer many advantages over serial manipulators, including greater structural rigidity, greater accuracy, and higher payload-to-weight ratios. However, CDPMs possess limited moment resisting/exerting capabilities and relatively small orientation workspaces. Various methods have been contemplated for overcoming these limitations, each with its own advantages and disadvantages. The focus of this paper is on one such method: the addition of base mobility to the system. Such base mobility gives rise to kinematic redundancy, which needs to be resolved carefully in order to control the system. However, this redundancy can also be exploited in order to optimize some secondary criteria, e.g. maximizing the size and quality of the wrench-closure workspace. In this work, the quality of the wrench-closure workspace is examined using a Tension-Factor index. Two planar mobile base configurations are investigated, and their results compared with a traditional fixed-base system. In the rectangular configuration, each base is constrained to move along its own linear rail, with each rail forming right angles with the two adjacent rails. In the circular configuration, the bases are constrained to move along one circular rail. While a rectangular configuration enhances the size and quality of the orientation workspace in a particular rotational direction, the circular configuration allows for the platform to obtain any position and orientation within the boundary of the base circle.
TOPICS: Cables, Optimization, Manipulators, Stiffness, Mechanical admittance, Rails, Redundancy (Engineering), Weight (Mass), Kinematics, Tension
research-article  
Qinchuan Li, Jacques Marie Hervé and Pengcheng Huang
J. Mechanisms Robotics   doi: 10.1115/1.4035989
Remote center-of-motion (RCM) parallel manipulators (PM) is fit for robotized minimally invasive surgery (MIS). RCM PMs with fixed linear actuators have advantages of high stiffness, reduced moving mass, higher rigidity and load capacity. However the available architectures of such type are very few. Using the Lie group algebraic properties of the set of rigid body displacements, this paper proposes a new family of RCM PMs with fixed linear actuators for MIS. The general motion with a remote center has 4 degrees of freedom (DoF) and is produced by the in-series concatenation of a spherical S pair and a prismatic P pair and, therefore, is said to be SP equivalent. The SP-equivalent PMs can be used in minimally invasive surgery. First, the kinematic bonds of limb chains and their mechanical generators for SP-equivalent RCM PMs are presented. Then limb chains with fixed linear actuators are then derived using the closure of products in subgroups. Structural conditions for constructing a SP-equivalent RCM PM with linear fixed actuators are revealed. Helical pairs are introduced to remove a local rotation and yield a 360-degree-rotation capability of the moving platform. Numerous new architectures with practical potentials are presented.
TOPICS: Actuators, Surgery, Manipulators, Stiffness, Architecture, Chain, Rotation, Stress, Degrees of freedom, Generators, Algebra, Kinematics
research-article  
Henry Arenbeck, Isabel Prause, Dirk Abel and Burkhard Corves
J. Mechanisms Robotics   doi: 10.1115/1.4035990
Radiotherapy (RT) enables a selective destruction of tumor cells while the treatment area is limited to the irradiated volume. Any RT technique comes along with multiple sources of error, which can lead to a deviation of the dose that is applied to the patient. Phantoms - structures that replicate a human and include measurement technology to assess the applied dosage - are used to make such errors observable. Nowadays, RT is at a transition stage towards techniques which explicitly account for physiological motion. These techniques require phantoms generating such motion. A new kind of parallel kinematic manipulator (PKM), which is tailored to the requirements of RT-phantom technology, is presented. The PKM consists of low cost standardized mechanical components and sets the target structures, which are located inside a human equivalent area, into translational and rotational motion in three degrees of freedom. Only a part of the End-effector is located within the human-equivalent area. All remaining parts of the PKM are located outside that area. Two versions of the manipulator are presented in detail, their kinematics are derived and their kinetostatic properties are compared. This includes a workspace analysis and the analysis of the transmission behavior in general meaning the influence of the most important design parameters on the performance. It can be shown that practical differences of both kinematics are negligible while the modified version provides significant mechanical advantages. In conclusion, a first special purpose manipulator for application in the evolving field of RT-phantom technology is presented.
TOPICS: Manipulators, Radiation therapy, Phantoms, Kinematics, Errors, Rotation, Degrees of freedom, Design, End effectors, Tumors, Physiology
research-article  
Sajid Nisar, Takahiro Endo and Fumitoshi Matsuno
J. Mechanisms Robotics   doi: 10.1115/1.4035991
Minimally Invasive Surgery requires four degrees-of-freedom (pitch, translation, yaw and roll) at the incision point but the widely-used planar Remote Center of Motion (RCM) mechanisms only provide one degree-of-freedom. The remaining three degrees-of-freedom (DoFs) are achieved through external means (such as cable-pulleys or actuators mounted directly on the distal-end) which adversely affect the performance and design complexity of a surgical manipulator. This paper presents a new RCM mechanism which provides the two most important DoFs (pitch and translation) by virtue of its mechanical design. The kinematics of the new mechanism is developed and its singularities are analyzed. To achieve maximum performance in the desired workspace region, an optimal configuration is evaluated. The design is also optimized to yield maximum manipulability and tool translation with smallest size of the mechanism. Unlike the traditional planar RCM mechanisms, the proposed design does not rely on external means to achieve translation DoF, and therefore, offers potential advantages. The mechanism can be a suitable choice for surgical applications demanding a compact distal-end or requiring multiple manipulators to operate in close proximity.
TOPICS: Kinematics, Degrees of freedom, Optimization, Surgery, Manipulators, Design, Design engineering, Pulleys, Yaw, Actuators, Cables
research-article  
John W. Gerdes, Hugh A. Bruck and Satyandra K. Gupta
J. Mechanisms Robotics   doi: 10.1115/1.4035994
Flapping wing flight is a challenging system integration problem for designers due to tight coupling between propulsion and flexible wing subsystems with variable kinematics. High fidelity models that capture all subsystem interactions are computationally expensive and too complex for design space exploration and optimization studies. A combination of simplified modeling and validation with experimental data offers a more tractable approach to system design and integration that maintains acceptable accuracy. However, experimental data on flapping wing aerial vehicles that is collected in a static laboratory test or a wind tunnel test is limited because of the rigid mounting of the vehicle, which alters the natural body response to flapping forces generated. In this study, we instrument a flapping wing aerial vehicle to provide in-flight data collection that is unhindered by rigid mounting strategies. The sensor suite includes measurements of attitude, heading, altitude, airspeed, position, wing angle, and voltage and current supplied to the drive motors. This in-flight data is used to set up a modified strip theory aerodynamic model with physically realistic flight conditions. A coupled model that predicts wing motions is then constructed by combining the aerodynamic model with a model of flexible wing twist dynamics and enforcing motor torque and speed bandwidth constraints. Finally, the results of experimental testing are compared to the coupled modeling framework to establish the effectiveness of the proposed approach for improving predictive accuracy by reducing errors in wing motion specification.
TOPICS: Stress, Actuators, Wings, Flight, Motors, Design, Modeling, Aircraft, Errors, Strips, Wind tunnels, Optimization, Testing, Vehicles, Instrumentation, Propulsion, Kinematics, Dynamics (Mechanics), Torque, Sensors, Data collection
research-article  
Venkatasubramanian Kalpathy Venkiteswaran, Omer Anil Turkkan and Hai-Jun Su
J. Mechanisms Robotics   doi: 10.1115/1.4035992
This paper seeks to speed up the topology optimization using a pseudo-rigid-body (PRB) model, which allows the kinetostatic equations explicitly represented in nonlinear algebraic equations. PRB models can not only accommodate large deformations, but more importantly reduce the number of variables compared to beam theory or finite element methods. A symmetric 3R model is developed and used to represent the beams in a compliant mechanism. The design space is divided into rectangular segments while kinematic and static equations are derived using kinematic loops. The use of the gradient and hessian of the system equations leads to a faster solution process. Integer variables are used for developing the adjacency matrix, which is optimized by a genetic algorithm. Dynamic penalty functions describe the general and case-specific constraints. The effectiveness of the approach is demonstrated with the examples of a displacement inverter and a crimping mechanism. The approach outlined here is also capable of estimating the stress in the mechanism which was validated by comparing against Finite Element Analysis. Future implementations of this method will incorporate other pseudo-rigid-body models for various types of compliant elements and also try to develop multi-material designs.
TOPICS: Topology, Compliant mechanisms, Optimization, Kinematics, Deformation, Stress, Finite element methods, Design, Finite element analysis, Euler-Bernoulli beam theory, Algebra, Displacement, Genetic algorithms
research-article  
Frederick Sun and Jonathan B. Hopkins
J. Mechanisms Robotics   doi: 10.1115/1.4035993
This paper introduces a general method for analyzing flexure systems of any configuration, including those that cannot be broken into parallel and serial subsystems. Such flexure systems are called interconnected hybrid flexure systems because they possess limbs with intermediate bodies that are connected by flexure systems or elements. Specifically, the method introduced utilizes screw algebra and graph theory to help designers determine the freedom spaces (i.e., the geometric shapes that represent all the ways a body is permitted to move) for all the bodies joined together by compliant flexure elements within interconnected hybrid flexure systems (i.e., perform mobility analysis of general flexure systems). This method also allows designers to determine (i) whether such systems are under-constrained or not and (ii) whether such systems are over-constrained or exactly-constrained (i.e., perform constraint analysis of general flexure systems). Although many flexure-based precision motion stages, compliant mechanisms, and microarchitectured materials possess topologies that are highly interconnected, the theory for performing the mobility and constraint analysis of such interconnected flexure systems using traditional screw theory does not currently exist. The theory introduced here lays the foundation for an automated tool that can rapidly generate the freedom spaces of every rigid body within a general flexure system without having to perform traditional computationally expensive finite element analysis. Case studies are provided to demonstrate the utility of the proposed theory.
TOPICS: Bending (Stress), Screws, Mechanical admittance, Algebra, Space, Finite element analysis, Shapes, Compliant mechanisms
research-article  
Landen Bowen, Kara Springsteen, Saad Ahmed, Erika Arrojado, Mary Frecker, Timothy Simpson, Zoubeida Ounaies and Paris von Lockette
J. Mechanisms Robotics   doi: 10.1115/1.4035966
A concept recently proposed by the authors is that of a multi-field sheet that folds into several distinct shapes based on the applied field, be it magnetic, electric, or thermal. In this paper the design, fabrication, and modeling of a multi-field bifold is presented that utilizes magneto-active elastomer (MAE) to fold along one axis and an electroactive polymer, P(VDF-TrFE-CTFE) terpolymer, to fold along the other axis. In prior work a dynamic model of self-folding origami was developed which approximated origami creases as revolute joints with torsional spring-dampers and simulated the effect of magneto-active materials on origami-inspired designs. In this work, the crease stiffness and MAE models are discussed in further detail, and the dynamic model is extended to include the effect of electroactive polymers (EAP). The accuracy of this approximation is validated using experimental data from a terpolymer-actuated origami design. After adjusting crease stiffness within the dynamic model, it shows good correlation with experimental data, indicating that the developed EAP approximation is accurate. With the capabilities of the dynamic model improved by the EAP approximation method, the multi-field bifold can be accurately modeled. The model is compared to experimental data obtained from the fabricated multi-field bifold, and is found to predict well the fold angles of the sample. This validation of the crease stiffness, MAE, and EAP models allows for more complicated multi-field applications to be designed moving forward with confidence in the simulated performance.
research-article  
Mark M. Plecnik and Ron Fearing
J. Mechanisms Robotics   doi: 10.1115/1.4035967
In this work, a new method is introduced for solving large polynomial systems for the kinematic synthesis of linkages. The method is designed for solving systems with degrees beyond 100,000, which often are found to possess a number of finite roots that is orders of magnitude smaller. Current root-finding methods for large polynomial systems discover both finite and infinite roots, although only finite roots have meaning for engineering purposes. Our method demonstrates how all infinite roots can be avoided in order to obtain substantial computational savings. Infinite roots are avoided by generating random linkage dimensions to construct start-points and start-systems for homotopy continuation paths. The method is benchmarked with a four-bar path synthesis problem.
TOPICS: Kinematics, Linkages, Polynomials, Dimensions
Technical Brief  
Anurag Purwar, Shrinath Deshpande and Qiaode Jeffrey Ge
J. Mechanisms Robotics   doi: 10.1115/1.4035899
In this paper, we are presenting a unified framework for generating planar four-bar motions for a combination of pose- and practical geometric-constraints and its implementation in MotionGen, an indigenously developed app for Apple's iOS and Google's Android platforms. The framework is based on a unified type- and dimensional-synthesis algorithm for planar four-bar linkages for the motion generation problem. Simplicity, high-utility, and wide-spread adoption of planar four-bar linkages have made them one of the most studied topics in Kinematics leading to development of algorithms and theories that deal with path-, function-, and motion generation-problems. Yet to date, there have been no attempts to develop efficient computational algorithms amenable to real-time computation of both type and dimensions of planar four-bar mechanisms for a given motion. Moreover, there are no computational tools available to help mechanism designers solve this problem in an intuitive fashion while providing high-level, rich options to enforce practical constraints. MotionGen solves this problem effectively by extracting the geometric constraints of a given motion to provide the best dyad-types as well as dimensions of a total of up to six four-bar linkages. The unified framework also admits a plurality of practical geometric constraints, such as imposition of fixed- and moving-pivot and -line locations along with mixed exact- and approximate-synthesis scenarios.
TOPICS: Kinematics, Dimensions, Linkages, Algorithms, Design, Computation, Humanoid robots
research-article  
Dion Hicks, Taufiqur Rahman and Nicholas Krouglicof
J. Mechanisms Robotics   doi: 10.1115/1.4035879
Voice coil actuators are simple electro-mechanical devices which are capable of generating linear motion in response to an electrical input. The generic cylindrical design of commercially available actuators imposes a large variety of limitations on the end-user. The most prominent is the requirement to design and fit extra components to the actuator in order to increase functionality. To solve this issue, a novel voice coil actuator was created which reconfigures the standard cylindrical design with one of a rectangular structure. The novel actuator incorporates planar magnets in a modified Halbach array configuration to ensure compactness and an exceptionally intense, uniform magnetic field. The moving coil is substituted with a printed circuit board encompassing numerous current conducting traces. The board contains a miniature linear rail and bearing system, unified drive electronics and highly adaptive position feedback circuitry resulting in a compact, highly dynamic and accurate device. In pursuit of optomechatronic applications, two distinct parallel kinematic mechanisms were developed to utilize the high dynamics and accuracy of the novel actuator. These devices were configured to function in only rotational degrees of freedom and because of their underlying kinematic structures can be referred to as parallel orientation manipulators. In particular, two structures were defined, 2-PSS/U and 3-PSS/S in order to constraint their payloads to two and three degrees of rotational freedom, respectively. The resultant manipulators are highly dynamic, precise and fulfill size, weight and power requirements for many applications such as sense and avoidance and visual tracking.
TOPICS: Actuators, Design, Kinematics, Manipulators, Rails, Electronics, Printed circuit boards, Weight (Mass), Dynamics (Mechanics), Electromechanical devices, Magnets, Magnetic fields, Degrees of freedom, Feedback, Bearings
research-article  
Lawrence W. Funke and James Schmiedeler
J. Mechanisms Robotics   doi: 10.1115/1.4035878
This paper presents a general method to perform simultaneous topological and dimensional synthesis for planar rigid-body morphing mechanisms. The synthesis is framed as a multi-objective optimization problem for which the first objective is to minimize the error in matching the desired shapes. The second objective is typically to minimize the actuating force/moment required to move the mechanism, but different applications may require a different choice. All possible topologies are enumerated for morphing mechanism designs with a specified number of degrees of freedom and infeasible topologies are removed from the search space. A multi-objective genetic algorithm is then used to simultaneously handle the discrete nature of the topological optimization and the continuous nature of the dimensional optimization. In this way, candidate solutions from any of the feasible topologies enumerated can be evaluated and compared. Ultimately, the method yields a sizable population of viable solutions, often of different topologies, so that the designer can manage engineering tradeoffs in selecting the best mechanism. Three examples illustrate the strengths of this method. The first examines the advantages gained by considering and optimizing across all topologies simultaneously. The second and third demonstrate the method's versatility by incorporating prismatic joints into the morphing chain to allow for morphing between shapes that have significant changes in both shape and arc length.
TOPICS: Degrees of freedom, Chain, Optimization, Errors, Genetic algorithms, Pareto optimization, Shapes, Tradeoffs
research-article  
Jelle Rommers, Giuseppe Radaelli and Justus Herder
J. Mechanisms Robotics   doi: 10.1115/1.4035881
Recently, there has been an increased interest in origami art from a mechanism design perspective. The deployable nature and the planar fabrication method inherent to origami provide potential for space and cost efficient mechanisms. In this paper, a novel type of origami mechanisms is proposed in which the compliance of the facets is used to incorporate spring behavior: Compliant Facet Origami Mechanisms (COFOMs). A simple model that computes the moment characteristic of a Single Vertex COFOM has been proposed, using a semi-spatial version of the Pseudo-Rigid Body (PRB) theory to model bending of the facets. The performance of this PRB model has been evaluated numerically and experimentally, showing good performance. The PRB model is a potential starting point for a design tool which would provide an intuitive way of designing this type of mechanisms including their spring behavior, with very low computational cost.
TOPICS: Manufacturing, Design, Modeling, Springs
Technical Brief  
Yang Liu and J. Michael McCarthy
J. Mechanisms Robotics   doi: 10.1115/1.4035882
This paper describes a mechanism design methodology that draws plane curves that have finite Fourier series parameterizations, known as trigonometric curves. We present three ways to use the coefficients of this parameterization to construct a mechanical system that draws the curve. One uses Scotch yoke mechanisms for each of the terms in the coordinate trigonometric functions, which are then added using a belt or cable drive. The second approach uses two coupled serial chains obtained from the coordinate trigonometric functions. The third approach combines the coordinate trigonometric functions to define a single coupled serial chain that draws the plane curve. This work is a version of Kempe's Universality Theorem that demonstrates that every plane trigonometric curve has a linkage that draws the curve. Several examples illustrate the method including the use of boundary points and the discrete Fourier transform to define the trigonometric curve.
TOPICS: Theorems (Mathematics), Cables, Linkages, Chain, Design, Design methodology, Fourier series, Fourier transforms, Belts
Design Innovation Paper  
Zhe Xu, Connor McCann and Aaron M. Dollar
J. Mechanisms Robotics   doi: 10.1115/1.4035863
A wide range of engineering applications, ranging from civil to space structures, could benefit from the ability to construct material-efficient lattices that are easily reconfigurable. The challenge preventing modular robots from being applied at large scales is mainly the high level of complexity involved in duplicating a large number of highly integrated module units. We believe that reconfigurability can be more effectively achieved at larger scales by separating the structural design from the rest of the functional components. To this end, we propose a modular chain-like structure of links and connector nodes that can be used to fold a wide range of 2D or 3D structural lattices that can be easily disassembled and reconfigured when desired. The node geometry consists of a diamond-like shape that is one twelfth of a rhombic dodecahedron, with magnets embedded on the faces to allow a forceful and self-aligning connection with neighboring links. After describing the concept and design, we demonstrate a prototype consisting of 350 links and experimentally show that objects with different shapes can be successfully approximated by our proposed chain design.
TOPICS: Chain, Design, Shapes, Engineering systems and industry applications, Diamonds, Geometry, Magnets, Robots, Structural design, Engineering prototypes, Space frame structures

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