We consider here a class of mechanisms consisting of one or more compliant members, the manipulation of which relies on the deflection of those members. Compared with traditional rigid-body mechanisms, compliant mechanisms have the advantages of no relative moving parts and thus involve no wear, backlash, noises and lubrication. Motivated by the need in food processing industry, this paper presents the Global Coordinate Model (GCM) and the generalized shooting method (GSM) as a numerical solver for analyzing compliant mechanisms consisting of members that may be initially straight or curved. As the name suggests, the advantage of global coordinate model is that all the members share the same reference frame, and hence, greatly simplifies the formulation for multi-link and multi-axis compliant mechanisms. The GCM presents a systematic procedure with forward/inverse models for analyzing generic compliant mechanisms. Dynamic and static examples will be given and verified experimentally. We also develop the Generalized Shooting Method (GSM) to efficiently solve the equations given by the GCM. Unlike FD or FE methods that rely on fine discretization of beam members to improve its accuracy, the generalized SM that treats the boundary value problem (BVP) as an initial value problem can achieve higher-order accuracy relatively easily. Using the GCM, we also presents a formulation based on the Nonlinear Constrained Optimization (NCO) techniques to analyze contact problems of compliant grippers. For a planar problem it essentially reduces the domain of discretization by one dimension. Hence it requires simpler formulation and is computationally more efficient than other methods such as finite element analysis. An immediate application for this research is the automated live-bird transfer system developed at Georgia Tech. Success to this development is the design of compliant mechanisms that can accommodate different sizes of birds without damage to them. The feature to be monolithic also makes complaint mechanisms attracting in harsh environments such as food processing plants. Compliant mechanisms can also be easily miniaturized and show great promise in microelectromechanical systems (MEMS). It is expected that the model presented here will have a wide spectrum of applications and will effectively facilitate the process of design and optimization of compliant mechanisms.

No description available.

No description available.

No description available.

Thesis (Ph. D.)--Marquette University, 2009. / Access available to Marquette University only. Available for download on June 17, 2010. Robert J. Stango, Nicholas J. Nigro, Stephen Heinrich, Vikram Cariapa, Shuguang Huang, Advisors.

Miniature compliant grippers are designed and developed to manipulate biological cells and characterize them. Apart from grippers, other compliant mechanisms are also demonstrated to be effective in manipulation and characterization. Although scalability and force-sensing capability are inherent to a compliant mechanism, it is important to design a compliant mechanism for a given application. Two techniques based on Spring-lever models and kinetoelastostatic maps are developed and used for designing compliant devices. The kinetoelastostatic maps-based technique is a novel approach in designing a mechanism of a given topology and shape. It is also demonstrated that these techniques can be used to tune the stiffness of a mechanism for a given application. In situations where any single mechanism is incapable of executing a specific task, two or more mechanisms are combined into a single continuum with enhanced functionality. This has led to designs of composite compliant mechanisms. Biological cells are manipulated using compliant grippers in order to study their mechanical responses. Biological cells whose size varies from 1 mm (a large zebrafish embryo) to 10 µm (human liver cells), and which require the grippers to resolve forces ranging from 1 mN (zebrafish embryo) to 10 nN (human cells), are manipulated. In addition to biological cells, in some special cases such as tissue-cutting and cement-testing, inanimate specimens are used to highlight specific features of compliant mechanisms. Two extreme cases of manipulation are carried out to demonstrate the efficacy of the design techniques. They are: (i) breaking a stiff cement specimen of stiffness 250 kN/m (ii) gentle grasping of a soft zebrafish embryo of stiffness 10 N/m. Apart from manipulation, wherever it is viable, the mechanisms are interfaced with a haptic device such that the user’s experience of manipulation is enriched with force feedback. An auxiliary study on the characterization of cells is carried out using a micro¬pipette based aspiration technique. Using this technique, cells existing in different conditions such as perfusion, therapeutic medicines, etc., are mechanically characterized. This study is to qualitatively compare aspiration-based techniques with compliant gripper-based manipulation techniques. A compliant gripper-based manipulation technique is beneficial in estimating the bulk stiffness of the cells and can be extended to estimate the distribution of Young’s modulus in the interior. This estimation is carried out by solving an inverse problem. A previously reported scheme to solve over specified boundary conditions of an elastic object—in this case a cell—is improved, and the improved scheme is validated with the help of macro-scale specimens.

The principal aim of this research is the design of a more compliant horseshoe which allows the natural expansion and compression of the horse hoof. Three different simulations have been carried out in by using Finite Element Method in order to know the behaviour of the horse hoof when is analysed under the same load conditions. First the hoof will be studied without any horseshoe to obtain the produced displacement by the hoof expansion. Once the displacement of the barefoot hoof is known, an assembly, in which a sample stiff horseshoe is attached to the hoof by nails, will be performed to obtain both the hoof displacement as the horseshoe one. Finally, after three different researches about the current horseshoes, different possible alternative materials and most commons attachment methods, a more flexible horseshoe will be created and analysed. The results obtained in the three simulations will be compared and commented.

"Escapement mechanisms hold back a stream of parts driven either by mechanical or pneumatic means for a length of time and release a single part as required to an assembly station. They are used in most automatic multi-component assembly equipment. They occupy a significant design space and have dynamic characteristics of their own. This research aimed to develop a novel high speed mechanism for parts escapement that occupies less design space and contributes less to the dynamic activity of the structure. Several conceptual mechanisms were generated and evaluated. A compliant mechanism that amplifies the very small displacement of a piezo actuator was selected for detailed design. A proof of concept prototype was fabricated and tested. A piezo stack was used to bend a thin, spring steel, compliant beam. Its deflection was further amplified by attaching a comparatively rigid beam extension at the end of the compliant section. The mechanism escapes parts at 16 Hz using constrained layer damping on the beam to reduce vibrations. The concept is feasible to use on production machinery and provides advantages in terms of higher operating speeds and compactness. The concept could also be used where there is a requirement of high speed gating."

Origami has become a source of inspiration in a number of engineered systems. In most systems, non-paper materials where material thickness is non-negligible is required. In origami-inspired engineered systems where thickness is non-negligible, thickness-accommodation techniques must be utilized to overcome the issue of self-intersection. Many thickness-accommodation techniques have been developed for use in thick-origami-inspired-engineered systems. In this work several thickness-accommodation techniques are reviewed and discussed. New thickness-accommodation techniques including hybrid thickness-accommodation techniques and the split vertex technique are presented and discussed. These techniques enable new capabilities of thickness-accommodation in origami adapted design. Thickness-accommodation techniques have been developed in the context of developable origami patterns and the application of these techniques to non-developable patterns is introduced here. The capability of non-developable thick origami is demonstrated in an application example of a deployable locomotive nose-fairing.

Compliant bistable mechanisms are mechanisms that have two stable equilibrium positions within their range of motion. Their bistability is mainly due to the elasticity of their members. This thesis introduces a new type of bistable micromechanisms, the Bistable, Spherical, Compliant, four-bar Micromechanism (BSCM). Theory to predict bistable positions and configurations is also developed. Bistabilty was demonstrated through testing done on micro-prototypes. Compared to the mathematical model of the BSCM, Finite element models of the BSCM indicated important qualitative differences in the mechanism's stability behavior and its input-angle-input torque relation. The BSCM has many valuable features, such as: Two stable positions that require power only when moving from one stable position to the other, accurate and repeatable out-of-plane motion with resistance to small perturbations. The BSCM may be useful in several applications such as active Braille systems and Digital Light Processing (DLP) chips.