<p> This dissertation presents the kinematic design of six-bar linkages for function, motion, and path generation by means of polynomial homotopy continuation algorithms. When no link dimensions are specified beforehand, the synthesis formulations for each design objective yield polynomial systems of degrees in the millions and billions, suggesting a large number of solutions. Complete solution sets to these systems have not yet been obtained and is the topic of this dissertation. Function generation for eleven positions is explored in most detail, in particular the Stephenson II and III function generators, for which we calculate multihomogeneous degrees of 264,241,152 and 55,050,240. A numerical reduction using homotopy estimates these systems to have 1,521,037 and 834,441 roots, respectively. For motion generation, the Watt I linkage can be specified for eight positions, producing a system of a multihomogeneous degree over 19 billion. However, for this work we focus on the smaller case of six positions, numerically reducing this system to an estimated 5,735 roots. For path generation we take a different approach. The design of path generators is formulated as RR chains constrained to have a single degree-of-freedom by attaching six-bar function generators to them. This enables us to use our results obtained on Stephenson II and III function generators to create four types of eleven position path generators: the Stephenson I linkage, two types of Stephenson II linkages, and the Stephenson III linkage. </p>

<p> Compliance in legged robotics has recently become favored over rigid leg members. The energy cost associated with rigid legged walking is high, and speeds are typically decreased with terrain changes. The use of compliant legs can provide stable walking while enabling higher maximum speeds. </p><p> Inspired by biological principals in insectoid locomotion, a physical model for energy efficient limb design was explored. A compliant leg structure was designed and replaced the rigid leg members of an insectoid robot. Velocity and ground reaction force data was gathered for both rigid and compliant lower leg members at various stiffness values for ideal and complex terrain. </p><p> Furthermore, a command was designed to maximize walking speeds. Design parameters of stiffness, command duration, and command spacing are selected. The designed command, combining the optimal value of the design parameters, produced an increased stance departure velocity value and can be implemented in insectoid robots with compliant legs.</p>

<p> Path planning is a common research topic and has applications in various fields and industries, such as AI, industrial automation, and mobile robotics. When applied to mobile systems, path planning algorithms are required to plan safe and feasible paths for a system from an initial state to a desired final state. While most path planning algorithms have been designed for rigid systems, little work has focused on path planning algorithms for flexible systems. Motion planning for flexible systems has typically involved sequential methods that plan trajectories for a system, then apply vibration control techniques for trajectory tracking. This thesis proposes new algorithms that concurrently plan a path for a flexible system while limiting the induced vibration. </p><p>

<p> Current adhesives and gripping mechanisms used in many robotics applications function on very specific surface types or at defined attachment locations. A controllable, i.e. ON-OFF, adhesive mechanism that can operate on a wide range of surfaces would be very advantageous. Such a device would have applications ranging from robotic gripping and climbing to satellite docking and inspection/service missions. The main goal of the research presented here was to create such an attachment mechanism through the use of a new hybrid adhesive technology. The newly developed adhesive technology is a hybridization of electrostatic and micro-structured dry adhesion. The result provides enhanced robustness and utility, particularly on rough surfaces. There were challenges not only in the integration of these two adhesive elements but also with its application in a complete gripping mechanism.</p><p> Electrostatic and directional dry adhesives were both individually investigated. The electrode geometry for an electrostatic adhesive was optimized for maximum adhesion force using finite element analysis software. Optimization results were then verified through experimental testing. New manufacturing techniques were also developed for electrostatic adhesives that utilized a metalized mesh embedded in a silicone polymer and Kapton film based construction, greatly improving adhesion. The micro-structured dry adhesive used was provided by Dr. Aaron Parness, from the NASA Jet Propulsion Lab (JPL), and consists of an array of vertical stalks with an angled front face, referred to as micro-wedges. The hybrid electrostatic dry adhesive (EDA) was created by fabricating the electrostatic adhesive directly on top of a dry adhesive mold. This process created an array of dry adhesive micro-wedges directly on the surface of the electrostatic adhesive. In operation the electrostatic adhesive provides a normal force which serves to pull the dry adhesive into the surface substrate. With greater surface contact more of the dry adhesive is able to engage, bring the electrostatic adhesive even closer to the surface and increasing its effectiveness. Therefore, the combination of these two technologies creates a positive feedback cycle whose whole is often greater than the sum of its parts.</p><p> An interface mechanism is needed to transmit applied loads from a rigid structure to the flexible adhesive while still maintaining its conformability. This is especially important for strong adhesion on rough surfaces, such as tile and drywall. Different concepts such as a structured fibrillar hierarchy and a fluid-filled backing pouch have been explored. Additionally, finite element analysis was used to evaluate different fribrillar shapes and geometries for the structured hierarchy. The goal was to equalize the load distribution across the adhesive while still maintaining surface compliance. A gripper mechanism was also created which used a servo for actuation and three rigid tiles with a directional dry adhesive. It was tested on a perching Micro Air Vehicle (MAV) as well as in the RoboDome facility at NASA's Jet Propulsion lab to simulate a satellite docking/capture maneuver.</p>

<p>This dissertation explores bicycle dynamics through an extension of the Whipple bicycle model and validation of the model equations equations of motion through the implementation of a robotic bicycle. An extended Whipple bicycle model is presented which makes uses of a unique set of physical parameters based on cylindrical gyrostats. The nonlinear equations of motion for this model are derived, linearized, and validated against a set of benchmark model parameters. A general formulation for the linearization of a system with configuration and velocity constraints is presented, and is demonstrated on an idealized rolling disk. The method of linearization is directly applicable to the equations of motion which result from the application of Kane's method. The linearization procedure is used to formulate the linear state space equations of motion for the bicycle model, which are then used as the plant model to design the robotic bicycle control system. The mechanical, electrical, and software aspects of the robotic bicycle are presented, along with representative results from a set of experiments.

<p> Mobile robots are un-manned systems and must be able to overcome the obstacles they face without human intervention. In this research we have proposed a novel retractable mechanism which converts a linear hydraulic motion into expansion of six claws at each wheel. In order to control the expansion, optimal control theory was applied and a constrained optimization problem was defined using different Simulink toolboxes and applied to the mechanism modeled in SimHydraulics/SimMechanics. The main benefit of performing both hydraulic and mechanical system simulation and also control design in the same environment is to eliminate mathematical approximation of the model and using existing Simulink simulation tools for simulation and control. Systems were modeled and controller optimization was performed. Simulation results are illustrated at the end, which show the method's versatility and reliability for controlling the mechanism operation.</p>

<p>Given a desired function for an effector, what is its appropriate shape? This thesis addresses the problem of designing the shape of a rigid end effector to perform a given manipulation task. It presents three main contributions: First, it describes the contact kinematics of an effector as the product of both its shape and its motion, and assumes a fixed motion model to explore the role of shape in satisfying a certain manipulation task. Second, it formulates that manipulation task as a set of constraints on the geometry of contact between the effector and the world. Third, it develops tools to transform those contact constraints into an effector shape for general 1-DOF planar mechanisms and general 1-DOF spatial mechanisms, and discusses the generalization to mechanisms with more than one degree of freedom. </p><p> We describe the case studies of designing grippers with invariant grasp geometry, grippers with improved grasp stability, and grippers with extended grasp versatility. We further showcase the techniques with the design of the fingers of the MLab hand, a three-fingered gripper actuated with a single motor, capable of exerting any combination of geometrically correct enveloping or fingertip grasps of spherical, cylindrical, and prismatic objects of varying size. </p>

<p>Cables are used in various fields like construction, sports, communication, and transportation. Two important fields where cables are used for this research are transportation and high-voltage power lines. In the field of transportation, cables are used in cable-riding systems like cable cars, tramways, and gondola lifts. Vibration is induced in these systems. These vibrations are undesirable. </p><p> High-voltage power line cables are important part of our lives. Inspection of these power lines is necessary to eliminate the risk of power outages. Earlier power lines were inspected by skilled humans by crawling along the power lines. This inspection task was replaced by cable riding inspection robots to eliminate the risk to human life. </p><p> This research explains various inspection robots and problems in these types of cable-riding systems. In this research, to determine the vibrations in the cable due to riding load, a new simple cable-mass system was developed. This new cable-mass system makes it easy to develop a control system to reduce the cable vibrations. </p><p> To inspect the power lines, HiBot developed an inspection robot called Expliner that travels along the live power lines. For uninterrupted inspection operation, Expliner traverses obstacles on the power lines with its intelligent acrobatic mode. In this mode, Expliner is subjected to rocking oscillation. This rocking oscillation is also induced in the cables cars. This rocking is undesirable and is unsafe. </p><p> This research introduces a method to reduce rocking in cable-riding systems. This method, called input shaping, is used to run simulations for Expliner traveling along curved cables. This research develops an input shaper to reduce rocking in cable-riding robots like Expliner. </p>

<p> Humans generally have difficulty performing precision tasks with their unsupported hands. To compensate for this difficulty, people often seek to support or rest their hand and arm on a fixed surface. However, when the precision task needs to be performed over a workspace larger than what can be reached from a fixed position, a fixed support is no longer useful. </p><p> This dissertation describes the development of the Active Handrest, a device that expands its user's dexterous workspace by providing ergonomic support and precise repositioning motions over a large workspace. The prototype Active Handrest is a planar computer-controlled support for the user's hand and arm. The device can be controlled through force input from the user, position input from a grasped tool, or a combination of inputs. The control algorithm of the Active Handrest converts the input(s) into device motions through admittance control where the device's desired velocity is calculated proportionally to the input force or its equivalent. </p><p> A robotic 2-axis admittance device was constructed as the initial Planar Active Handrest, or PAHR, prototype. Experiments were conducted to optimize the device's control input strategies. Large workspace shape tracing experiments were used to compare the PAHR to unsupported, fixed support, and passive moveable support conditions. The Active Handrest was found to reduce task error and provide better speed-accuracy performance. </p><p> Next, virtual fixture strategies were explored for the device. From the options considered, a virtual spring fixture strategy was chosen based on its effectiveness. An experiment was conducted to compare the PAHR with its virtual fixture strategy to traditional virtual fixture techniques for a grasped stylus. Virtual fixtures implemented on the Active Handrest were found to be as effective as fixtures implemented on a grasped tool. </p><p> Finally, a higher degree-of-freedom Enhanced Planar Active Handrest, or E-PAHR, was constructed to provide support for large workspace precision tasks while more closely following the planar motions of the human arm. Experiments were conducted to investigate appropriate control strategies and device utility. The E-PAHR was found to provide a skill level equal to that of the PAHR with reduced user force input and lower perceived exertion.</p>

<p> My thesis covers the design and fabrication of novel humanoid robotic eyes and the process of interfacing them with the industry robot, Baxter. The mechanism can reach a maximum saccade velocity comparable to that of human eyes. Unlike current robotic eye designs, these eyes have independent left-right and up-down gaze movements achieved using a servo and DC motor, respectively. A potentiometer and rotary encoder enable closed-loop control. An Arduino board and motor driver control the assembly. The motor requires a 12V power source, and all other components are powered through the Arduino from a PC. </p><p> Hand-eye coordination research influenced how the eyes were programmed to move relative to Baxter&rsquo;s grippers. Different modes were coded to adjust eye movement based on the durability of what Baxter is handling. Tests were performed on a component level as well as on the full assembly to prove functionality.</p><p>