This article is based on several nouns about transmission performance such as limiting positions, manipulation angle, transmission angle and mechanical advantage. In order to analyse the transmission performance of the coupler-driven and crank-output linkage mechanism, this article has developed an index called Transmissivity of Mechanical Advantage (TMA) for designers, besides this useful index, this article has identified a new noun as Total Transmission Coupler Point, that means after acting a force on the same direction of coupler point moving instantly, then the output force on the crank will act on it¡¦s moving direction and make the Transmissivity Index be the best as 1. For the designers of the coupler-driven linkage mechanisms, the transmission performance and the position where the force acts on involves to coupler curves very much. Based on the result of this research, the designers are able to choose the most proper coupler curves, and the best position of the coupler point would be designed. The designers are able to pick the best one among several similar coupler curves, and also they can certainly get a best range of either the length or the angle of the coupler designed when they were designing the coupler-driven type 4-bar linkage or the Stephenson¡¦s III 6-bar linkage. The applying force must change the direction all the time when a coupler-driven mechanism is driven, and it makes this type of mechanism seems to be uncommon, but it doesn¡¦t mean this kind of mechanism is not worth of application. On the other hand, the short of research about this type of mechanism makes the designers feel helpless when they were trying to analyse the transmission performance of mechanisms were designed. This article develops not only the theorem of analysis but also builds computer programs to help the designers to analyse the transmission performance quickly and correctly

Based on the traditional six-bar toggle mechanisms, this study is focused on the design of two types of cam-link mechanisms. Six-bar toggle mechanisms are simple, and they have an extreme mechanical advantage in toggle position so that they are widely used in plastic forming machines. Cam-crank-slider and cam-double-slider linkage are the two types mechanisms that we concerned. And we find the difference between these mechanisms for kinematic and dynamic performance. The benefit of cam-link mechanisms compares to linkage mechanisms is more precision points. We can synthesize the curve profile with the demand for forming acceleration or stroke. Because we need interpret the kinematic characteristic of toggle mechanisms by using several boundaries condition of different curves. This study selects two kinds from foregoing curve for the model.

This research uses Transmissivity Index (TI) and other transmission indices to analyze the transmission performance by applying those indices to coupler-driven mechanisms with sliders. Other estimative transmission indices include Total Transmission Index (TTI) and Transmissible Mechanical Advantage (TMA). The point with best transmission performance is ¡§Effective Point,¡¨ and the combination of the effective points becomes ¡§Locus of Effective Points¡¨. In addition, this research puts the influence of mechanisms with sliders including slider-friction into consideration, and also analyzes two inverses of mechanisms with sliders. Then we can extend to study the transmission performance of six-bar mechanisms. Finally, we apply the research result into some examples, such as ping pong table mechanism, four-bar and six-bar windows operator mechanisms, rowing exercise mechanism, so that we can find the better transmission performance of those mechanisms.

Origami-based mechanisms have unique characteristics that make them attractive for engineering applications. However, origami-based design is still a developing area of design. Continued work to increase general understanding of key design parameters specific to origami-based mechanisms will increase the ability of designers to capture the potential benefits of origami-based mechanisms. This thesis presents a fundamental study of origami to assist designers in gaining a stronger understanding of the key parameters and capabilities of origami-based mechanisms. As a starting point a study of fundamental motions in action origami models (those that exhibit motions in their folded state) is presented to explore fundamental motions and actuation in origami-based mechanisms. Eleven fundamental motions are outlined and defined with the associated actuation forces that drive them. Additionally, considerations for ensuring necessary performance and force transfer characteristics in origami mechanisms are presented. This is done by exploring the effect of surrogate hinge selections, fold pattern modification, and actuation inputs on the final mechanism. A model of mechanical advantage in origami models consisting of N, degree-4, vertices (where N = 1,2,3,...) is developed and explored. From the exploration of the parameters of the mechanical advantage model it is shown that hinge selection can greatly affect the performance of an origami mechanism by determining its range of motion, precision, and mechanical advantage. Therefore, in order to better understand this important design decision, specific considerations for surrogate hinge selection are presented. These considerations discuss methods to increase performance and reduce hinge imprint, as well as develop surrogate hinges in metals. The key design parameters and considerations presented herein as well as study of origami motions serve to lay the groundwork toward the development of analysis tools and design guidelines specifically suited to origami based design.

This thesis presents a technique for the optimal synthesis of planar five-link mechanisms that produce a desired mechanical advantage function over a specified path. Since a five-bar linkage has two degrees of freedom, small deviations from the specified path are possible without significantly altering the mechanical advantage function. The research shows one potential application, the design of strength machines, where it is important to control force while allowing the user freedom of motion. In the past, closed-form analytical synthesis techniques have been used to design mechanical-advantage-generating linkages. This method is time consuming and case specific. However, optimal synthesis techniques apply to the general case and present a robust solution procedure. This thesis uses the non-linear pattern search technique of Hooke and Jeeves to synthesize five-bar linkages. The search technique matches user strength curves and mechanism resistance curves to produce a five-link mechanism. This mechanism produces the desired mechanical-advantage function and serves as the basis for strength training machines. Unlike analytical synthesis, optimization allows direct incorporation of a greater number of design constraints, thus resulting in solutions that are more practical. The pattern search technique aims to minimize a given objective function that depends primarily on the force generating capabilities and kinematic constraints on of the linkage. / Master of Science

Series elastic actuators (SEAs) have numerous benefits for force controlled robotic applications. This thesis presents the design and assembly of a set of compact, lightweight, low-friction linear SEAs for the legs of the Tactical Hazardous Operations Robot (THOR). The THOR SEA pairs a ball screw driven linear actuator with a configurable titanium leaf spring. A removable pivot changes the effective cantilever length, setting the compliance to either 372 or 655 kN/m. Unlike typical SEAs which measure actuator load through spring deflection, an in-line axial load cell directly measures actuator forces up to the commandable peak of 2225 N. The continuous operating range of the actuator is computed, along with an evaluation of the range of motion and torque profiles for the parallel hip and ankle joints. With a focus on a large power-to-weight ratio and small packaging size, the THOR SEAs are well-suited for accurate torque control of the parallel joints on the robot. Linearly actuated joints, especially ones driven through a crank arm, tend to suffer from a loss of mechanical advantage toward the ends of its limited range of motion. To augment the range of motion and mechanical advantage profile on THOR, an inverted Hoeken's linkage straight line mechanism is paired with a linear SEA at the hip and knee pitch joints on the robot. The resulting linkage assembly is capable of delivering nearly constant peak torque of 115 Nm across its 150 degree range of motion. The mechanical advantage profile of the Hoeken's linkage actuator is computed for the nominal case, as well the deviation resulting from maximum deflection of the titanium beam. / Master of Science

This thesis presents elliptical rolling contact joints as an alternative to circular rolling contact and conventional revolute joints where high quality force transmission "low friction and backlash" with variable output are desired. Parameters specific to the joint and its position are developed in terms of relative link angles and elliptical surface geometry. These parameters are used to generate the basic forward kinematics for elliptical rolling link toggle mechanisms with oscillatory motion and high mechanical advantage. As large compressive loads are characteristic of such mechanisms, stress conditions are identified and principles for joint stability with variable, precision outputs are discussed. Finally, application is made to self-adjusting passive force closures with a case study of the MUSCLE Brake (Multi-toggle Self-adjusting Connecting-Linked Electromechanical) disc brake caliper. Elliptical rolling contact joints are shown to offer several benefits over circular rolling contact, including: reduced Hertz contact stresses and flexure bending stresses, variable output velocity, maximum use of contact interface by distributing small rotations across surfaces of small curvature, reduced forces on stabilizing members, increased mechanical advantage due to eccentricity, and no-slip pure rolling provided exclusively by connecting links (or flexures) without the need for gear teeth or friction.