The configuration spaces (c-space) of mechanisms and robots can in many cases be presented as an algebraic variety. Different motion modes of mechanisms and robots are found as irreducible components of the variety. Singularities of the variety correspond usually (but not necessarily) to intersections of irreducible components/motion modes of the configuration space. A well-known method for finding the modes is the prime (and/or primary) decomposition of the constraint ideal corresponding to the mechanisms specific constraint map. However the direct computation of these decompositions is still in many cases too exhausting at least for standard computers. In this paper we present a method to speed up the decomposition significantly. If the mechanism consists or is constructed of subsystems whose c-space can be decomposed in feasible time then the whole decomposition of the c-space of the mechanism can be constructed from the decompositions of the subsystems. Here we concentrate on the 4-bar-subsystems but the approach generalizes naturally to more complicated subsystems as well. In fact the method works for all mechanisms which are constructed of subsystems whose decomposition is already known or can be computed. Further we present a way to investigate the nature of singularities which relies on the computation of the tangent cone at singular points of the c-space and the investigation of the primary decomposition of the tangent cone itself and partially its connection to intersection theory of algebraic varieties.

This study proposes a Multi Joint Gripper (MJG) that achieves envelope grasping for unknown shape objects with simple control. In our previous study we have developed the MJG having a number of multi joint fingers. Each finger has back drivability with Variable Stiffness Mechanism (VSM) for adjusting the stiffness of joints. The MJG succeeded envelope grasping of various shape objects with no sensory feedback. We have also showed the MJG is able to handle objects by pinching with the finger tips and to shift into an envelope grasping. However, in some tasks requiring transition from pinching to envelope grasping, it occasionally failed because of difference of mode setting between pinching and grasping. In this paper, we discuss the pinching motion and the transition from pinching to envelope grasping. The finger mechanism we have proposed is mainly composed of a serially connected Differential Gear System (DGS), and it is controlled by only two actuators. One for driving all of the joints simultaneously and the other for VSM of every joints all together. We propose a novel mechanism for transition from pinching to envelope grasping , which requires no change of mechanical mode setting of the DGS. The experiments revealed that the MJG successfully achieves transition from pinching to envelope grasping with very simple control.

This study primarily proposes a procedure to design a crease pattern for beetle-inspired deployable wings based on the hindwings in relatively large-sized beetles like horn beetle or chafer. First, we discuss the representative patterns of wing supports and crease lines based on previous entomological research and propose a basic geometry for the artificial wing. Next, the flat foldability and rigid foldability of the proposed crease pattern are discussed based on origami geometry. Geometrical restrictions for flat- and rigid-foldable wings are numerically expressed as a function of the design parameters, and the Newton-Raphson method is used to compute the actual solutions. Although researchers have attempted to characterize the representative crease patterns found in beetles, only flat foldability has been considered in previous research. Our proposed method enables the design of rigid-foldable wings based on beetle-inspired patterns, which is considered beneficial in designing the deployable structures.

Directed acoustic energy is used throughout medical practices, scientific research, and engineering applications. Conventionally, arrays of transducer constituents are assembled and driven with inputs that are determined by digital signal processing methods, which guides the acoustic waves for signal transmission and reception purposes. Beamforming is the term for this approach, although inherent limitations of stability and computational efficiency hinder the outcomes. Recent efforts have revealed the broad merits of folding origami-inspired acoustic array architectures so that the transducer constituent and array shapes change, giving rise to direct control of acoustic energy radiation characteristics. Because the design of the origami tessellation used to create the array is pivotal to the adaptive acoustic energy steering, a new star-shaped foldable transducer is studied in this work for its unique inward and outward shape change characteristics. In order to facilitate this investigation, an analytical framework is developed to identify the connections between the folding-induced topology and radiated sound field. The high-fidelity boundary element method verifies the analytical model while experimental efforts validate the theoretical predictions. The adaptation of radiated sound pressure from the star-shaped transducer is shown to be several orders of magnitude, which illustrates its great potential in acoustic energy guidance and prospective applications.

A Concentrated Solar Power on Demand (CSPonD) system heats a tank of molten salt with sunlight, storing the sun’s energy thermally and generating electricity when needed using a heat exchanger. To prevent the heated salt from forming thermal gradients (reducing the heat exchanger’s efficiency) or overheating (and becoming corrosive), a thermal mixing element mixes the heated salt both axially and radially. Since the mixing element can only move axially within the tank, it contains internal, radial channels to induce radial flow of the salt. These channels are constructed from tabbed wall-components, whose tabs seat into and extend past slots in the top- and bottom-plates of the mixing element. The top- and bottom-plates are constructed from multiple panels with overlapping slots, allowing the panels to form the plates when the tabs are inserted. This interlocking design allows majority of the mixing element to be rapidly manufactured at a low cost from sheet metal and simplifies transportation. In situ, the assembled components fasten together by bending the over-extending tabs, minimizing the number of fasteners needed.

As the role of robotics continues to expand beyond highly structured manufacturing applications to other domains, including medical and service applications, safe operation in the presence of people is becoming increasingly important. Many existing safety systems rely on fragile and sophisticated joint torque sensors and control models that greatly add to the expense and complexity of the robot system. This paper presents the “Fusion Clutch”, a mechanical system for decoupling high-impedance actuators from the output, such as a robot arm, in the event of a collision. In its nominal configuration, the clutch couples the transmission to the output via a spring-loaded bi-stable mechanism that is able to quickly decouple the two in the event of a collision with very low activation force. After the actuator is disengaged, the clutch also applies a brake to the output that prevents it from falling under the force of gravity but allows the operator to still reposition it. This prevents a robot arm from pinning the operator after the mechanism had been activated. Experimental results validate the small force required to activate the mechanism, along with a substantial decrease in force impulse during impact.

Comparatively slow growth in power storage and generation makes power-efficient designs desirable for legged robot systems. One important cause of power losses in robotic systems is the mechanical antagonism phenomenon, i.e. one or more motors being used as brakes while the others exert positive energy. This two-part paper first develops a rigorous understanding of mechanical antagonism in multiactuator robotic limbs. We show that, for a 6-DoF robot arm, there exist 4096 distinct regions in the force-velocity space of the end effector (the regions are distinguishable by the sign of the actuator powers). Only sixty-four of these regions correspond with operating points where all actuators exert positive power into the system. In the second part of the paper, we formulate a convex optimization problem which minimizes mechanical antagonism in redundant manipulators. We solve the optimization problem which becomes the derivation for a new, power-optimal, pseudoinverse for non-square Jacobians. In fact, two such pseudoinverses are derived: one for statically determinate systems, such as serial manipulators, and one for statically indeterminate systems, such as parallel manipulators.

We introduce a novel input device for the teleoperation of extensible continuum robots. As opposed to previous works limited by kinematically dissimilar master devices or restricted Degrees-of-Freedom (DoF), a kinematically similar input device capable of nine degrees-of-freedom is designed and used. The device is capable of achieving configurations identical to a three-section continuum robot and simplifies the control of such manipulators. In this paper, we outline the design of the input device and its construction. Implementation of the new master device and its effectiveness in regulating a physical system is also discussed.

A passively controlled infinitely variable transmission modeled and experimentally investigated by Cyders (2012), has potential to be combined with a number of different types of mechanisms. The mechanism’s incorporation into a hydraulic pump has many applications of interest; the CVT approach to a positive-displacement pump could provide a combination of the advantages of both positive-displacement and centrifugal pumps in one machine. This work had two main objectives: first, an inverse dynamic analytical model was developed using piece-wise techniques that simulated the behavior of the CVT/PD pump system. Second, this simulation was compared against experimental results, which were generated from data taken from an example system prototype. Predictions were made using an inverse-dynamics model, and were compared against experimental findings generated from a prototype of the system. The simple approach to modeling provided results sufficient to describe the overall pressure-flowrate behavior of the pump at low speeds, but a more sophisticated dynamic approach is still necessary to improve model agreement at high speeds when second-order effects begin to dominate.

The abstraction of biological folding mechanisms can lead to the development of novel foldable solutions for engineering problems. Examples of biological structures that are analogous to foldable engineering solutions are discussed and serve as inspiration for this research effort. Numerous folding mechanisms exist in nature and have not been considered for engineering solutions simply because they are not well-known or studied by designers. These folding mechanisms may provide useful design inspiration for novel engineering applications. To retrieve meaningful biological design analogies, information retrieval techniques are employed and a text-based search algorithm is developed to return useful passages where folding mechanisms in nature are observed. The search algorithm integrates tailored keywords and filtering methods to retrieve passages from an extensive biological corpus. Keywords are established using literature review and WordNet. The search algorithm is validated using an inter-rater reliability analysis and statistical methods for information retrieval. Passages describing biological systems are evaluated and potential engineering applications are discussed to demonstrate the functionality of the search algorithm. Methods for improvement and areas for future work are discussed.

This paper deals with a 6R single-loop overconstrained spatial mechanism that has two pairs of revolute joints with intersecting axes and one pair of revolute joints with parallel axes. The 6R mechanism is first constructed from an isosceles triangle and a pair of identical circles. The kinematic analysis of the 6R mechanism is then dealt with using a dual quaternion approach. The analysis shows that the 6R mechanism usually has two solutions to the kinematic analysis for a given input and may have two circuits (closure modes or branches) with one or two pairs of full-turn revolute joints. In two configurations in each circuit of the 6R mechanism, the axes of four revolute joints are coplanar, and the axes of the other two revolute joints are perpendicular to the plane defined by the above four revolute joints. Considering that from one configuration of the 6R mechanism, one can obtain another configuration of the mechanism by simply renumbering the joints, the concept of two-faced mechanism is introduced.

Designing structures through the means of origami brings many advantages for engineering applications. In current research, the underlying origami principle is often selected based on experience out of a range of known patterns and then manually altered to fit the design problem. This tedious and time-consuming procedure, if automated through computational tools, has the potential to facilitate the design of origami engineering applications. This however requires efficient kinematic simulation of origamis that is also able to accommodate to design requirements specific to foldable structures. In this paper, a simulator is implemented that is able to model the motion of origami vertices without the need for mountain-valley assignments and with a path of deployment as activation. The formulation of constraint equations through these vertex positions does not restrict the system to certain folding configurations, which is why the approach is able to detect different rigid body modes resulting from single activations. Finding rigid body modes can be beneficial for the search of design alternatives conforming to certain input requirements. The results of the simulation show promise for the incorporation of the simulator within an automated procedure for the design of origamis.

We study the wave propagation behavior in Miura-ori patterns by using the Bloch-wave analysis framework. Our investigation focuses on acoustic bandgaps that act as stopping bands for wave propagation at certain frequencies in periodic solids or structures. We show that bandgaps can be created in two-dimensional periodic Miura-ori patterns by introducing material inhomogeneity. First, we perform Bloch-wave analysis of homogeneous Miura-ori patterns with finite panel rigidity and find that no bandgaps are present. We then introduce bandgaps by making the pattern non-uniform — by changing the mass and axial rigidity of origami panels of alternating unit cells. We discuss the dependence of the magnitude of the bandgap on the contrast between material properties. We find that higher magnitudes of bandgaps are possible by using higher contrast ratios (mass and stiffness). These observations indicate the potential of origami-based patterns to be useful as acoustic metamaterials for vibration control.

A hexapod robot with parallel leg mechanism has been developed for rescue missions in nuclear power plants. The 1-UP & 2-UPS parallel leg mechanism has high payload but limited workspace which prevents the robot from climbing steep stairs. In this paper, a simple graphic method is proposed to estimate the robot’s stair-climbing capability based on its legs’ workspaces. The influence of the robot’s pitch motion on its payload capability is analyzed. Then a new waist mechanism which consists of a dual-parallelogram architecture is designed for the robot to increase its stair-climbing capability. Finally a simulation is carried out to demonstrate the robot’s stair-climbing capability with the help of the waist mechanism, and a prototype has been built and tested.

As mechanisms with origami-like movement increase in popularity, there is a need for conducting electrical power across folds. This need could potentially be filled by the use of surrogate folds. Surrogate folds are a localized reduction in stiffness in a given direction allowing the material to function like a fold. Current methods for conducting across folds are reviewed along with current opportunities. A framework for designing conductive surrogate folds that can be adapted to fit specific applications is presented. Equations for calculating the resistance in single surrogate folds as well as arrays are given. Prototypes of several conductive joints are presented and discussed. The framework is then followed in the designing and manufacturing of a conductive origami-inspired mechanism.

Linear guides are extensively employed in several industrial applications. Miniaturization, minimal friction, cost efficiency and low maintenance are the major challenges faced while developing a linear motion system. This paper presents design and realization of such systems, overcoming the aforementioned challenges. Linear guidance mechanisms, suitable for implementing latching in Refreshable Braille Displays are proposed, where uniform behavior under eccentric loading is required. Several low cost, reliable and efficient guide mechanisms with predetermined dimensional constraints have been designed. Seven mechanisms are illustrated and analyzed in this paper, which includes both, traditional contact-based mechanisms and compliant mechanisms that offer contact-less motion. The paper further compares the functionality, cost feasibility and ease of manufacturing and assembly of these mechanisms.

A novel thickness-accommodation technique for origami based mechanisms is introduced. This technique modifies a zero-thickness pattern by splitting each vertex along the minor folds into a system of two vertices. The modified fold pattern then has thickness applied to it and the resulting mechanism is kinematically equivalent to the modified fold pattern. Origami patterns that are rigid-foldable and only have two panels that stack between folds are utilized in the technique. The technique produces thick origami mechanisms where all panels lie in a plane in the unfolded state without any holes or protrusions and maintain a single degree of freedom. Steps for synthesizing split-vertex mechanisms are presented and examples of split-vertex mechanisms are shown. Advantages and potential applications of the technique are discussed.

Large antenna reflectors used in space have to be folded before launching. Silicone rubber is commonly used as antenna material due to its ability to maintain a shape without external supports upon deployment. However, localized vertices could appear during the folding process, which might lead to material yielding and unrecoverable deformation after deployment. In this paper, the cross folding process of a thin elastic sheet, a common folding method in packaging a reflective membrane, was studied numerically with the aim of eliminating material failure in the sheet. The deformation, stress distribution, and peak stress of the sheet and the dependency of those properties on geometrical parameters were systematically investigated. Based on these studies, two methods, i.e., central hole method and central slit method, were explored to reduce the peak stress caused by cross folding. The results showed that a central slit parallel to the first folding crease was the most effective in reducing the peak stress without causing significant damage to the antenna.

In this work, we present a strategy to design and construct 3D shape paper models that can be automatically folded and glued using a robotic machine. Here, we use concepts of “kirigami”, that is a combination of folding and cutting paper, and “norigami”, that combines folding with gluing of the paper. A software was developed in order to create crease patterns using a two-dimensional polyline profile and rotating it around an axis by a unit of 2 π/N rad (N>2). The gluing areas were modified to permit free allocation and movement. The proposed method is also evaluated and validated to construct several 3D shapes using paper-like materials by hand, or using a special machine developed in our previous researches.

A novel biped robot based on a 4-UPU (universal-prismatic-universal) parallel mechanism with actuation redundancy is presented. The biped robot consists of two platforms and four UPU serial chains as limbs. The actuation method of the mechanism is determined based on the mobility and singularity analysis. The singular positions of the mechanism are identified and then eliminated using a redundant actuator. To meet different requirements, the multiple motion modes of the robot are discussed and simulated in the gait analysis. Moreover, the robot has special gaits for reset and self-rescue if overturned. Kinematic analysis of the mechanism and walking stability analysis are carried out in detail. Physical prototype experiments indicate that the proposed biped robot is feasible. Through properly planning the motion modes, the biped robot can quickly pass through rugged terrain containing slopes and obstacles.