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1	A Study of Cognate Mechanisms of Spherical Four-Bar Linkages Pai, Tung-Hsing 20 July 2000 (has links) Cognate mechanisms have been often used in design of linkages. Improper positions of fixed link or transmission angle could be improved effectively. Cognate mechanisms of planar linkages have been developed well, but the research on the spherical cognate is still wild open. There are just only spherical supplement mechanisms that have been presented by Soni(1967) until today. The aim of this thesis is to investigate the existence of spherical four-bar linkages cognate mechanisms. The geometry and properties of planar cognate mechanisms are discussed and a simulation program is written for the planar cognate mechanism. Then, the characteristics of spherical mechanisms are considered and the spherical cognate simulation program is built by using the result of planar cognate as a reference. Three examples are given to demonstrate the existence of pseudo-cognates for spherical mechanisms. four-bar linkage couple curve curve cognate spherical mechanism
2	Mechanical System Design of a Haptic Cobot Exoskeleton LaFay, Eric Bryan 24 August 2007 (has links) No description available. Haptic Exoskeleton Shoulder Mechanism Spherical Mechanism Optimization of Spherical Mechanism Cobot Exoskeleton Haptic REACH exoskeleton CVT design mechanical system design range of motion study upper extremity exoskeleton
3	Origami-Based Design of Fold States and Stability Avila, Alex 01 December 2018 (has links) Origami is a potentially elegant and powerful source of inspiration for many engineering designs. The viable shapes (fold states) of a single device allow it to perform multiple, seemingly contradictory, functions. The fold state is a large factor in the device's performance, but there are challenges in selecting and maintaining those fold states. In this thesis we analyze existing concepts for overcoming these challenges. Those concepts are compared with those that occur in origami-based devices. From this analysis fundamental gaps were identified, specifically, shortcoming in the terminology used to refer to (1) non-flat origami states and (2) sets of facets and creases. Likewise we found a need for a comprehensive categorization method of fold states. Fold states are divided into seven types based on the set of fold angles they contain: U, P, F, UP, UF, PF, and UPF. The origami-based devices are analyzed based on their functional fold states, showing an emphasis on P and PF fold states. The fold states and their functions are tabulated. We demonstrate the table as a tool in an origami-based design method. Selecting fold states for an application is just the first step for effective use of origami. Once selected, the origami fold state must be maintained during use to perform its functions. This thesis also outlines the Origami Stability Integration Method (OSIM) for integrating a wealth of stability techniques. These techniques are categorized and analyzed to assist designers in selecting a technique for a device's application. Both methods, the fold-state selection method and the OSIM, are demonstrated in designing an origami-based ballistic barrier. The barrier is designed to stow in a compact fold state and deploy to a partially folded state to provide protection during armed conflicts. Quick deployment and a stable structure make the barrier a valuable example of origami-based design, demonstrating these two methods in addressing some of origami's design challenges. origami fold states origami linkage stability design spherical mechanism Mechanical Engineering
4	Concepts for retractable roof structures Jensen, Frank Vadstrup January 2005 (has links) Over the last decade there has been a worldwide increase in the use of retractable roofs for stadia. This increase has been based on the flexibility and better economic performance offered by venues featuring retractable roofs compared to those with traditional fixed roofs. With this increased interest an evolution in retractable roof systems has followed. This dissertation is concerned with the development of concepts for retractable roof systems. A review is carried out to establish the current state-of-the-art of retractable roof design. A second review of deployable structures is used to identify a suitable retractable structure for further development. The structure chosen is formed by a two-dimensional ring of pantographic bar elements interconnected through simple revolute hinges. A concept for retractable roofs is then proposed by covering the bar elements with rigid cover plates. To prevent the cover plates from inhibiting the motion of the structure a theorem governing the shape of these plate elements is developed through a geometrical study of the retractable mechanism. Applying the theorem it is found that retractable structures of any plan shape can be formed from plate elements only. To prove the concept a 1.3 meter diameter model is designed and built. To increase the structural efficiency of the proposed retractable roof concept it is investigated if the original plan shape can be adapted to a spherical surface. The investigation reveals that it is not possible to adapt the mechanism but the shape of the rigid cover plates can be adapted to a spherical surface. Three novel retractable mechanisms are then developed to allow opening and closing of a structure formed by such spherical plate elements. Two mechanisms are based on a spherical motion for the plate elements. It is shown that the spherical structure can be opened and closed by simply rotating the individual plates about fixed points. Hence a simple structure is proposed where each plate is rotated individually in a synchronous motion. To eliminate the need for mechanical synchronisation of the motion, a mechanism based on a reciprocal arrangement of the plates is developed. The plate elements are interconnected through sliding connections allowing them mutually to support each other, hence forming a self-supporting structure in which the motion of all plates is synchronised. To simplify the structure further, an investigation into whether the plate elements can be interconnected solely through simple revolute joints is carried out. This is not found to be possible for a spherical motion. However, a spatial mechanism is developed in which the plate elements are interconnected through bars and spherical joints. Geometrical optimisation of the motion path and connection points is used to eliminate the internal strains that occur in the initial design of this structure so a single degree-of-freedom mechanism is obtained. The research presented in this dissertation has hence led to the development of a series of novel concepts for retractable roof systems. 690.15
5	Achieving Complex Motion with Fundamental Components for Lamina Emergent Mechanisms Winder, Brian Geoffrey 01 March 2008 (has links) (PDF) Designing mechanical products in a competitive environment can present unique challenges, and designers constantly search for innovative ways to increase efficiency. One way to save space and reduce cost is to use ortho-planar compliant mechanisms which can be made from sheets of material, or lamina emergent mechanisms (LEMs). This thesis presents principles which can be used for designing LEMs. Pop-up paper mechanisms use topologies similar to LEMs, so it is advantageous to study their kinematics. This thesis outlines the use of planar and spherical kinematics to model commonly used pop-up paper mechanisms. A survey of common joint types is given, as well as an overview of common monolithic and layered mechanisms. In addition, it is shown that more complex mechanisms may be created by combining simple mechanisms in various ways. The principles presented are applied to the creation of new pop-up joints and mechanisms, which also may be used for lamina emergent mechanisms. Models of the paper mechanisms presented in Chapter 2 of the thesis are found in the appendix, and the reader is encouraged to print, cut out and assemble them. One challenge associated with spherical and spatial LEM design is creating joints with the desired motion characteristics, especially where complex spatial mechanism topologies are required. Hence, in addition to a study of paper mechanisms, some important considerations for designing joints for LEMs are presented. A technique commonly used in robotics, using serial chains of revolute and prismatic joints to approximate the motion of complex joints, is presented for use in LEMs. Important considerations such as linkage configuration and mechanism prototyping are also discussed. Another challenge in designing LEMs is creating multi-stable mechanisms with the ability to have coplanar links. A method is presented for offsetting the joint axes of a spatial compliant mechanism to introduce multi-stability. A new bistable spatial compliant linkage that uses that technique is introduced. In the interest of facilitating LEM design, the final chapter of this thesis presents a preliminary design method. While similar to traditional methods, this method includes considerations for translating the mechanism topology into a suitable configuration for use with planar layers of material. paper mechanism pop-up popup pop up mechanism linkage paper engineering paper crafts origami kinematics spatial mechanism planar mechanism bistable multi-stable spherical mechanism ortho-planar compliant PRBM pseudo-rigid-body model Lamina Emergent Mechanism LEM sheet goods planar layer complex joint elemental joint spatial joint degrees of freedom mechanism modeling mechanism design serial joint chain parallel series fundamental components complex motion revolute prismatic spherical cylindric universal half planar RSSR RCCC RSRC RTRT Altmann Bricard Bennett Goldberg 6R 4R joint axis angular offset paper joint V-fold circular arch figure-8 single slit double slit tube strap arch knee mechanism 45 degree fold solid shape floating layer tent Mechanical Engineering

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