The rapid release of energy in mechanisms is often limited by conversion of potential energy to kinetic energy. The use of a flywheel to store energy over time eliminates this constraint. Using this principle, a lightweight and compact energy transmission mechanism has been developed for robotic combat applications. The purpose of the proposed design is to throw an opposing robot ten or more feet into the air. This design incorporates a flywheel, a self-resetting dog clutch with built in shock absorbing rubber for impact mitigation, and an optimized four-bar linkage to deliver the energy. A mathematical model of the dynamic system has been developed to analyze and aid in the design process. Testing of subsystems was performed to validate the design. A final design is proposed with the recommendation that it be built and tested. A validated design is applicable to many real-world problems that require rapid kinetic energy release including reconnaissance robots required to hop high fences.

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.

Linkage mechanisms have been investigated for ages. The characteristics of planar four-bar linkages, though most fundamental of all, have laid the theoretical foundation of research and advancement of other linkages. Most papers have focused only on the standard crank-driven, torque-input four-bars, leaving the coupler-driven, force-input types comparatively less studied. Transmission performance is an important issue of mechanism design. In this thesis, an index that couples the coupler curve and the transmissivity of mechanical advantage for the coupler-driven, force-input four-bar is proposed. The new index, called the CCTMA, is used when its shape, length, curvature, and symmetry are inspected. A WS curve and a WS angle are also defined to facilitate the use and understanding of the CCTMA. A straightforward procedure is also presented for designing coupler-driven, force-input four-bar linkages. The idea of the CCTMA is introduced into the design process to exclude input coupler points what have unsatisfactory transmission properties. This procedure is also valid for improving existing coupler-driven, force-input four-bar mechanisms.

The following study focuses on the design and validation of an underactuated robotic gripper built for the Tactical Hazardous Operations Robot (THOR). THOR is a humanoid robot designed for use in the DARPA Robotics Challenge (DRC) and the Shipboard Autonomous Fire Fighting Robot (SAFFiR) project, both of which pertain to completing tasks associated with disaster response. The gripper was designed to accomplish a list of specific tasks outlined by the DRC and SAFFiR project. Underactuation was utilized in the design of the gripper to keep its complexity low while acquiring the level of dexterity needed to complete the required tasks. The final gripper contains two actuators, two underactuated fingers and a fixed finger resulting in four total degrees of freedom (DOF). The gripper weighs 0.68 kg and is capable of producing up to 38 N and 62 N on its proximal and distal phalanges, respectively. The gripper was put through a series of tests to validate its performance pertaining to the specific list of tasks it was designed to complete. The results of these tests show the gripper is in fact capable of completing all the necessary actions but does so within some limitations. / Master of Science

The kinematic analysis of an articulated twin body, four-wheel, robotic vehicle is presented. Polaris, a research platform and contending robotic vehicle in the Intelligent Ground Vehicle Competition (IGVC) at Virginia Tech, was redesigned in 2006 to improve the mobility of the vehicle by incorporating an innovative four-bar linkage that connects the two bodies. The new linkage design minimizes vehicle off-tracking by allowing the rear wheels to closely track the path of the front wheels. This thesis will outline the theoretical kinematic model of the four-bar linkage as applied to a twin-bodied, differentially driven vehicle. The kinematic model is validated through computer simulation as well as experimentation on a fully operational robotic vehicle. The kinematic model presented here outlines the foundations for an autonomous, four-wheel drive, multi-body control system and opens avenues for dynamically controlling the tracking of the vehicle's rear body with an actuated linkage configuration. / Master of Science

This work is initiated from an observation of the rolling-sliding kinematic behavior observed in the motion of the knee joint. We use the slip ratio as a parameter to analyze the rolling-sliding properties of a mechanism, and also propose a method to design new mechanisms with specific slip ratio. In this research, we first verify the many definitions of the slip ratio, then modify a best definition to suit various rolling-sliding motions. Most importantly, we propose two types of rolling-sliding mechanism design. By changing the parameters of the mechanism, we can adjust its slip ratio curve to be close to a desired curve. In addition, when the idea of adjustable link length is used in the design of the mechanism, exact slip ratio curve as specified can be generated by the use of some cams.

Flap, aileron, rudder, elevator, speed brake, stick, landing gear and similar movable systems used in aerospace industry have to operate according to the defined requirements and mechanisms used in those systems have to be synthesized in order to fulfill those requirements. Generally, without the use of synthesis tools, synthesis of mechanisms are done in CAD environment by trial-error and geometrical methods due to the complexity of analytical procedures. However, this approach is time consuming since it has to be repeated until the synthesized mechanism has suitable mechanism properties like transmission angle and connection points. Due to above reasons, a software developed for synthesis of mechanisms within the CAD environment can utilize all the graphical interfaces and provides convenience in mechanism design. In this work, it is aimed to develop a four-bar mechanism synthesis tool which is compatible with CATIA V5 by considering the requirements of aerospace industry. This tool performs function, path and motion synthesis and shows suitable mechanisms in CATIA according to input obtained from CATIA and mechanism properties.

The aim of this study is to present a design approach for compliant bistable four-link mechanisms. The design constraints are the two positions of the mechanism, the force required to snap between the positions and the fatigue life of the designed mechanism. The theory presented here will be applied to the door lock mechanism used in commercial dishwashers, which is originally designed as a rigid inverted slider crank mechanism snapping between two positions with the force applied by a spring. The mechanism is re-designed as a compliant bistable four-link mechanism and a prototype has been manufactured.

This thesis is a study in the application of kinematics coupled with elastic body mechanics. Most studies in kinematics assume all mechanism links to be inelastic. Furthermore, the methods of kinematic synthesis have generally been developed to meet requirements of displacement, velocity and acceleration. The work presented in this thesis differs in two important aspects. First, one grounded link of a four-bar linkage is replaced by a cantilevered beam in flexure to produce a force generating mechanism. Second, the synthesis method presented here allows the generation of these mechanisms in closed form for prescribed force generation. A compound archery bow that incorporates four-bar linkages has been developed as an example. This design relies on the non-linear mechanical advantage of the four-bar linkage and the bow mechanics to provide a resistance curve that is more compatible with the human strength curve. In addition, by modifying the bow kinematics, more potential energy can be stored, and thus potentially more kinetic energy can be transferred to the arrow than with previous bows. / Master of Science

In designing devices to produce straight-line motion, the designer has a fundamental choice between selecting sliding devices or selecting pinned linkages. Although they are more complex to design and implement, linkages will often prove a less expensive, more efficient, and generally more satisfactory option than simple sliders. The objective of this thesis is to provide a tool to the designer that serves as an aid in making intelligent decisions in the selection of four-bar linkage type straight-line-mechanisms. This thesis provides research into the selection, evaluation, and implementation of existing straight-line mechanism designs. Twenty-two straight-line mechanisms are compared for both compactness and fidelity of the straight-line path. Also, figures showing position, velocity, and acceleration of each a included. The functional product of to this work is a software program called Straight-line. Straight-line gives the designer a graphical environment from which a wide variety of straight-line mechanisms can be quickly analyzed and evaluated. The software also provides a new type-synthesis technique that allows the designer to generate a straight-line-mechanism by graphically inputting a desired path. / Master of Science