This thesis presents two methods for designing four-bar function generators by matching a plot of the desired function with curves and charts derived from the computer solution of the displacement equation relating the input and output angles of the four-bar linkage. A series of curves and charts is presented for various assumed ratios of link lengths. An accuracy check procedure is presented, and tabulated computer data are included so that accuracy checks can be made for the function generators designed by these methods. / M.S.

Identifying potential risk factors that affect slip-induced falls is key to developing effective interventions for reduction of injuries caused by these accidents. Existing epidemiological evidence suggests that localized muscle fatigue might be considered as an intrinsic risk factor that causes lack of balance control leading to falls. The literature on the relationship between localized muscular fatigue of the lower extremity and the gait parameters affecting slip severity is scarce. The purpose of the present study was to examine how lower extremity fatigue (quadriceps) alters gait parameters and increases slip severity. Sixteen healthy young participants were recruited to walk across an unexpected slippery floor in two different sessions (Fatigue and No fatigue). Kinematic and kinetic data were collected using a three-dimensional video analysis system and force plates during both sessions. The gait parameters important in assessing slip severity were compared for the two different sessions to evaluate the effects of fatigue. A repeated measure one-way analysis of variance (ANOVA) and multivariate analysis was employed to predict statistical significance. The results indicated a substantial increase in the heel contact velocity (HCV), required coefficient of friction (RCOF), slip distance II (SDII), peak average knee joint moment during slip recovery (kneemompeak), fall frequency and, a decrease in the transitional acceleration of the whole body COM (TA) in the fatigue session further indicating higher slip severity due to fatigue. In addition, a strong positive correlation was observed between RCOF and HCV, HCV and SDII, and, SDII and kneemompeak. These findings provide new insights into the relationship between localized muscular fatigue and slip initiation/recovery process. The present study concluded that localized muscular fatigue affects the gait parameters and increases slip severity and hence can be considered as a potential risk factor for slip-induced falls. / Master of Science

This thesis presents the development of an interactive graphics interface for MECSYN, a planar mechanism synthesis program. The purpose of this work is to produce a dynamic graphics interface, independent of a graphics device and providing a high level of user interaction. To achieve this, the proposed three-dimensional graphics standard PHIGS (Programmers Hierarchical Interactive Graphics System) is used for graphics support software. An overview of the synthesis theory is presented. The program structure is described and presented along with a listing of the graphics and interface routines of the program to aid in future development of the program (synthesis routines are not included). Several examples illustrating the features and use of the program have been included. / Master of Science

This dissertation aims to address how a change in landing substrate may change landing kinematics. To examine this possibility, mallards (Anas playtrhynchos) were used as a study species and 177 water landings were recorded through the use of two camera systems with photogrammetric capabilities. This enabled the landing trajectory and landing transition kinematics to be tracked in three dimensions. From the resulting position data three questions were pursued. Do mallards regulate landing kinematics through a ̇-constant strategy? With what kinematics do mallards land on water? Do landing kinematics respond to external factors, such as an obstacle to landing? Chapter 2 assesses the presence of a ̇-constant regulatory strategy and compares the implementation to other landing behaviors. Chapter 3 examines the variation observed in the landing kinematics of mallards, identifies the primary kinematic drivers of that variation, and detects differences in kinematic profile. Chapter 4 inspects the landing kinematics combined with the positions of all other waterfowl in the vicinity to test for the presence of obstacle avoidance behavior. / Doctor of Philosophy / Control of landing is an important ability for any flying animal. However, with the exception of perch landing, we know very little about how birds and other flyers land on a variety of different surfaces. Here, we aim to extend our knowledge in this area by focusing on how mallard ducks land on water. This dissertation addresses the following questions. Do mallards regulate landing speed and trajectory the same way as pigeons? At what speeds, angles, and postures do mallards land on water? Can mallards adjust landing behavior to avoid collisions with other birds on the water surface? Chapter 2 determines how mallards regulate landings and how it is similar and different from pigeons and several other flyers. Chapter 3 describes the speeds, angles, and postures used by mallards to land on water. In addition, this chapter finds evidence for at least two different categories of landing performed by mallards. Chapter 4 provides evidence that mallards avoid situations in which a collision with another bird is likely. However, it is unclear if this is an active choice made by the mallard or due to other circumstances related to the landing behavior. Overall, this dissertation illustrates how the landing behavior of mallards is similar to what has been documented in other animals. However there are significant differences such as higher impact speeds, and shallower angles. Both of which are likely related to the ability of water to absorb a greater amount of the impact forces than a perch or the ground would.

The HECS wing was developed by NASA Langley Research Center and has a nonplanar, hyper-elliptically swept leading and trailing edge as well as spanwise camber. For this wing, the leading and trailing edges are swept back according to a hyper-elliptical equation. The span of the wing is also defined with hyper-elliptical anhedral giving it nonplanar spanwise camber. A single-degree-of-freedom mechanism is developed to provide a means for the wing to continuously change shape from its nonplanar to planar configuration. The mechanism uses a repeating quaternary-binary link configuration to translate motion from one segment to the next. A synthesis of the mechanism is performed, such that with one input to the first segment of the chain, the other wing segments move into their desired positions. Linear aerodynamic theory is applied to the HECS wing configuration at certain morphed positions in order to predict the aerodynamic loads. This work performs a linear static analysis of the mechanism at different morphed positions. A finite element representation of the mechanism as a structure is developed. Using the predicted aerodynamic loads, a structural analysis is performed. The analysis investigates different materials and cross sections of the members to determine a need for redesign due to failure from buckling and bending stress. From the analysis of the mechanism, a design is finalized which lightens the structure as well as increases the strength. These results are beneficial for the next phase of model development of the mechanism. / Master of Science

This body of work presents methods for the optimization, analysis, and control of mixed serial-parallel structures known as SP-Stacks. A SP-Stack is a series of Stewart Platforms (SPs) linked via their top and bottom plates to create a serial chain of parallel mechanisms. SP-Stacks are unique in their bridging of the benefits of parallel architectures (high rigidity, strength, and precision) and serial architectures (reach and manipulability), at the cost of being extremely overactuated. SP-Stacks are also difficult to provide kinematic solutions for, as neither forward nor inverse kinematics of a system are closed form. The first work presented focuses on presenting algorithms and optimization functions pertaining to the kinematic configuration of a SP-Stack. It first presents two methods of fast inverse kinematics (IK) for the SP-Stack which do not take forces into account. The outputs of those more simplistic solvers as used as initial conditions for a Nonlinear Program (NLP) algorithm which optimizes the internal configuration of a SP-Stack such that the end effector (EE) plate remains at the desired location, and the maximal force experienced on any actuator is minimized. The second work presented focuses on hardware testing some of the constituent algorithms and conclusions drawn from the first paper and determining methods of compensating for, in software, detected defects in hardware and hardware measurement systems. This work also demonstrates a different form of force-optimization - compliance control (CC), which is executed on both a single SP responding to external forces, and a 2 SP-Stack responding to regular internal perturbation. Conclusions drawn from these works are useful for stacks of an arbitrary number of SPs, can be extended to other mixed-kinematic systems, and advance the capabilities of these systems to be useful contributors in field robotics. / Master of Science / A stewart platform (SP) is a type of robot which consists of two plates interconnected by six linear actuators in parallel, which allow the robot to either translate or rotate about any axis in space. SPs are limited in their ability to move, as their parallel construction limits their workspace. In order to counteract this, SPs can be stacked on top of one another, creating a SP-Stack. The SP-Stack is capable of using its status as a mixed serial-parallel system to move in a significantly larger area (an advantage derived by the serial component of its architecture) and retain extraordinary rigidity and strength (an advantage from its parallel architecture). As each SP has 6 Degrees of Freedom (6DoF), enabling the previously described free-space motion, a SP-Stack possesses 6n DoF, making it overactuated. An overactuated system has multiple internal configurations which allow for a desired end effector configuration. The body of work presented herein focuses on manipulating the overactuation of SP-Stacks to achieve desirable results such as finding configurations which are most resistant to external loading (optimization of actuator forces) or algorithms which allow SP-Stacks to comply with external loading (compliance control (CC)). The first work presented herein focuses on determining an optimal configuration for a 4 SP-Stack such that the maximum force experienced by any one of its linear actuators is minimized, given a known external force. This work also presents two methods of generating initial configurations for the SP-Stack which are fed into the optimization algorithm which produces the final solution, as well as providing details on the constraints which govern the movement and validity of configurations for the system. The second work presented expands on the work done in the first, moving into hardware testing for verification of algorithms which calculate forces experienced by the linear actuators. The hardware testing showcases some errors that can be introduced by low fidelity hardware, along with methodologies for counteracting those errors. Finally, the second work introduces CC, the ability for a robot to move itself to adapt to incoming forces, and applies it to a physical 2 SP-Stack as a demonstrator.

This study includes an experimental evaluation of a prototype trailing-arm suspension for heavy trucks. The primary goal of this new suspension is to match or improve the kinematics and dynamic performance of an existing "Z-bar" suspension. Significant reductions in cost, weight, and number of parts are the main reasons for this redesign. A permanent facility is constructed to support the testing of different heavy truck suspensions. For actuation of the vehicle suspension, hydraulic actuators are used in the kinematics tests in a quasi-dynamic manner. For the dynamic tests, the vehicle is excited using two hydrodynamic actuators. A collection of forces, displacements, velocities, and accelerations are measured during the tests using transducers that were installed on the suspension and test vehicle. The test measurements are analyzed in both time and frequency domains and then the results of the two suspensions were compared to establish the dynamic merits of the prototype suspension. The kinematics tests include vertical stiffness, roll stiffness, and roll steer measurements for each suspension. The results from the kinematics tests show that the trailing-arm suspension exhibits kinematics traits that are quite similar to the "Z-bar" suspension, within the context of the tests conducted in the study. The dynamic testing consists of three input signals commonly used for such tests, namely: a chirp signal input, a step signal input, and a range of pure tone inputs. The test results show that the resonant frequencies of the two primary suspensions differ by an amount that is most likely too small to affect ride dynamics. The two suspensions, however, exhibit significantly different damping characteristics. The new suspension has much less frictional damping than the existing suspension. This is expected to provide better ride characteristics, assuming that the primary dampers (shock absorbers) are properly tuned for the vehicle that the new suspension was designed for. / Master of Science

The Multi-Appendage Robotic System (MARS) built for this research is a hexapod robotic platform capable of walking and performing manipulation tasks. Each of the six limbs of MARS incorporates a three-degree of freedom (DOF), kinematically spherical proximal joint, similar to a shoulder or hip joint; and a 1-DOF distal joint, similar to an elbow or knee joint. Designing walking gaits for such multi-limb robots requires a thorough understanding of the kinematics of the limbs, including their workspace. The specic abilities of a walking algorithm dictate the usable workspace for the limbs. Generally speaking, the more general the walking algorithm is, the less constricted the workspace becomes. However, the entire limb workspace cannot be used in a continuous, statically stable, alternating tripedal gait for such a robot; therefore a subset of the limb workspace is dened for walking algorithms. This thesis develops MARS limb workspaces in the knee up conguration, and analyzes its limitations for walking on planar surfaces. The workspaces range from simple 2D geometry to complex 3D volumes. While MARS is a hexapedal robot, the tasks of dening the workspace and walking agorthm for all six limbs can be abstracted to a single limb using the constraint of a tripedal, statically stable gait. Based on understanding the behavior of an individual limb, a walking algorithm was developed to allow MARS to walk on level terrain. The algorithm is adaptive in that it continously updates based on control inputs. Open Tech developed a similar algorithm, based on a 2D workspace. This simpler algorithm developed resulted in smooth gait generation, with near-instantaneous response to control input. This accomplishment demonstrated the feasibility of implementing a more sophisticated algorithm, allowing for inputs of all six DOF: x and y velocity, z velocity or walking height, yaw, pitch and roll. This latter algorithm uses a 3D workspace developed to aord near-maximum step length. The workspace analysis and walking algorithm development in this thesis can be applied to the further advancement of walking gait generation algorithms. / Master of Science

Clinicians rely on perceptual analysis in the assessment and diagnosis of motor speech disorders. However, connecting perceptual measures to quantitative data has proved challenging. This study uses correlational analyses to explore the relationship between perceptual, acoustic, and kinematic measures. Twenty typical speakers provided speech samples of rapid syllable repetition and speech tasks, which were then rated by 12 listeners for precision and steadiness on a visual analog scale. Data was analyzed to identify significant correlations between the measures. We found evidence of a modest perceptual-acoustic relationship, with results suggesting that acoustic rate may be correlated with perceptual features. Our findings also suggest a significant perceptual-kinematic relationship, as several kinematic measures of displacement demonstrated significant correlations with precision and steadiness ratings. We found that speakers with more consistent speech movements received higher steadiness ratings, and speakers with faster articulatory movements were rated as more precise. This study supports the use of perceptual analysis in clinical practice and points towards establishing connections between perceptual, acoustic, and kinematic measures used in speech analysis.

Hand and finger movements are underrepresented in biomechanical studies, primarily due to the challenge of tracking the hands and fingers. Several limitations are associated with marker-based motion capture, including interference with natural movement, and require the tedious, time-consuming application of numerous markers. Advancements in computer vision have led to the development of markerless motion capture systems yet validation of markerless systems for the upper extremities is limited, especially the hand and fingers. The purpose of this study was to develop and assess a markerless motion capture system capable of tracking hand and finger kinematics. A markerless system using four synchronized webcams was developed. Camera pairs were organized in different angles Centre90° (C/90°), Left45°/Right45° (L45°/R45°), and Centre/Left45° (C/L45°). Motion capture was performed with both marker-based and markerless systems. Twenty healthy participants performed five dynamic hand tasks with and without markers. Three-dimensional joint positions were defined using a musculoskeletal model in OpenSim. No significant differences were observed between C/90° and C/L45° markerless camera pairs and the marker-based system. The L45°/R45° camera pair differed significantly from other markerless pairs in several tasks but agreed with the marker-based system for the index finger during flexion. For most of the fingers, no significant differences were found across the different camera pairs. Correlations and error for the concurrent finger flexion task revealed high consistency among all the camera pairs, with R² above 0.90 and RMSD below 10°, the thumb showed greater variability. The R² and RMSD varied depending on the camera comparison and finger for each task. Markerless motion capture for the hands and fingers is possible with little difference to marker-based systems and is dependent on the camera orientation used. / Thesis / Master of Science in Kinesiology