published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

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vii, 343 leaves : diags. tables. ; 30 cm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Statistics, 1978

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This thesis presents a method for determining range of body motion for a walking machine with feet fixed on the ground. The darkling beetle was selected as the sample subject in this study. A closed form inverse kinematic solution is used to determine if a point in space is within range of body motion. An algorithm for tracing workspace boundary is also presented. The software, developed in Microsoft QuickC, has three main parts: (1) a module for searching the workspace contours and recording the contour points, (2) a plotting program for presentation of the workspace on the screen, (3) a module to determine ranges of roll, pitch and yaw for specified foot positions. The plotting program shows four views of the workspace, including front, top, and side views, and user specified axonometric projection. Body range of motion for a representative set of foot positions is presented and analyzed. Results are presented for normal resting height (10mm) and for 8mm and 12mm heights. Body range of motion for feet positioned for the alternating tripod gait is also presented. Ranges of roll, pitch and yaw have been determined and are discussed. / Graduation date: 1991

This thesis examines the influence on range-of-motion of beetle body of changes in leg segment parameters. From beetle's leg orientation, influence of the following leg segment parameters are investigated: coxa length, coxa twist and body-coxa joint. Kinematic equations are derived for legs of the beetle. Roots of quartic polynomials obtained while solving the kinematic equations are found by using the Bairstow (1966) numerical method. Inverse kinematic solutions are obtained for each leg and used to determine whether a point is within the body range of motion or not. An algorithm developed by Mason (1957) and Cordray (1957) for tracing closed boundaries is used to find ranges of motion of the body and feet. Changes in body range of motion caused by alteration in leg segment parameters are complex and not easy to explain. Similarities between changes in body range of motion and foot range of motion are observed. A great deal more work is necessary to fully understand the importance of observed changes. / Graduation date: 1992

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This thesis investigates a simple dynamic model of the hind leg of a beetle during initiation of a step. The primary assumption was that the full load of the body was carried on the hind leg during this time. That is, the only forces on the body were that of the hind leg and gravity and their resultant produced forward acceleration. Only two dimensional models were used in this study. This was justified since the beetle is bilaterally symmetrical. However, it required the assumption that hind legs were positioned symmetrically and it limited the investigation to forward acceleration in a straight line. Models with two and three links were tested. The two link model assumed the body has no motion relative to the upper legs; that is the muscles were strong enough to prevent movement at the joint between body and leg. The three link model assumed only friction prevented movement at the joint between body and leg. Dynamic equations were developed using Lagrangian mechanics. These equations were integrated using the 4th order Runge-Kutta algorithm. Both models were driven by applying a constant torque at the joint between upper and lower segments. Driving torque was adjusted to minimize verical movement of body center of mass. Initial position of body center of mass relative to foot was varied to examine it's influence on both horizontal travel of body, center of mass and driving torque required for this travel. For both models horizontal travel was less dependent on initial height of body center-of-mass than on initial horizontal position. For both models required driving torque increased with decrease in initial height of body center-of-mass and with increase of initial horizontal distance from foot to body center-of-mass. For both models maximum horizontal travel was attained with minimum initial height of body center-of-mass and minimum initial horizontal distance between foot and body center-of-mass. For the two link model, maximum horizontal travel was approximately half of the total leg length while for the three link model the equivalent number was approximately one quarter, of total leg length. / Graduation date: 1992

While the locomotion performance of legged robots over flat terrain or known obstacles has improved over the past few decades, they have yet to equal the performance of their animal counterparts over variable terrain. This work analyzes a multi-legged reduced order model of cockroach locomotion on variable slopes which will be used as an inspiration for a future sprawled posture legged robot. The cockroach is modeled as a point mass, and each leg of the cockroach is modeled as a massless, tangentially rigid, linearly elastic spring attached at the center of mass. All of the springs are actuated to allow changes in energy to the system. This is accomplished by varying the force free length of each leg in a feed-forward manner without reliance on feedback to change the actuation scheme. Fixed points of the model are found using a numerical solver that varies the velocity and phase shift parameters while leaving all other parameters at fixed values selected to match true cockroach motion. Each fixed point is checked for stability and robustness representing how effective the model is at staying on the predetermined gait, and transport cost as a measure of how efficient this gait is. Stable and robust fixed points were successfully found for the range of heading angles encompassing those of representative cockroach motion at each slope. Cockroaches may select the gait used based on stability or efficiency. Thus, additional fixed points were found in combination with a search routine that varies the leg actuation parameters in order to optimize either stability or metabolic efficiency, gaining insights into why cockroaches use the gaits that they do. Optimized fixed points were found based on four different leg functional combination families depending on whether each leg pushes or pulls. Optimized fixed point gaits exist for every incline slope studied between level ground and vertical slopes, at a range of initial heading angles that encompass those typically used by cockroaches. The selected gaits using both a stability based and an efficiency based optimization on the modeled cockroach are very similar. Both are also similar to gaits used by real cockroaches. The forces generated by the model are qualitatively similar to the experimental forces. / Graduation date: 2012

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy / This thesis is a study of quantifiable variation in the geometric shape of the superior articular surface of the talus of higher primates, with special reference to fossil tali of Plio- Pleistocene hominids. (Abbreviation abstract ) / AC2017