<p> Above elbow prosthesis control has trended toward increasing the number of control channels in the human-prosthetic system, to provide simultaneous joint control. Several methods have had varying success, such as Targeted-Muscle-Reinnervation (TMR) and Electromyograph (EMG) pattern recognition. While the number of control channels is increased, the fundamental control loop is still based on amputees placing the prosthetic end effector through visual feedback. In most clinical uses prosthetic joints are driven with a standard proportional EMG antagonistic muscle controller (S). The S controller can be difficult for the amputee as nonintuitive muscle contractions are needed to overcome internal joint and induced external torques, in particular from gravity. To address these issues, two new controllers, which use gravity and friction compensation techniques, have been developed to share the control of the prosthetic elbow joint and reduce control effort on prosthetic users. The new controllers were tested against the S proportional control by having 10 test subjects reach to 6 targets in their user workspace utilizing a Utah Arm 2 testbed. Motion capture cameras recorded the reaching motions. The controllers were compared using quantitative metrics which define the approach, time to target and smoothness (jerk), and holding, steady state error and variance, stages of a reaching motion. A qualitative metric was also used which surveys a test subject's effort in performing a reach. It was found that when considering the new controllers using the combined data for all test subjects at all targets they outperformed the S controller, except in smoothness. It was also found that the new controllers statistically performed best over the S controller at target locations where the humerus was in flexion at approximately 45deg, except in smoothness. Smoothness is predicted to be more influenced by the joint friction in the elbow joint. Only one friction compensation method was tested. Further studies on friction affects by varying joint impedance is suggested. Considering these findings, including gravity compensation in the control for active prosthetic elbow joints is found to improve the control over the standard proportional control, as captured in the majority of the physical metrics and in test subject ratings. </p>

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Certain natural phenomena have been identified as having fractal properties in their patterns. That is, their seemingly random patterns contain a level of order and deterministic properties that are more complex than previously thought. Centre of Pressure (COP) traces are one of these phenomena. By using a fractal dimension analysis of COP, it is possible that we can gain more information about control during quiet stance than traditional analyses have previously allowed. This Thesis considered a group of young healthy participants and a group of elderly healthy participants to compare traditional measures of COP (range and velocity of sway, and total excursion area) against a fractal dimension analysis of COP. Results indicated that both types of analyses are able to distinguish between eyes open and eyes closed in the elderly group. However, the fractal dimension analysis more accurately detects differences between the participant groups when standing with their eyes closed. Based on these results it is suggested that a fractal dimension analysis is more informative about posture control than traditional measures. Recommendations for future research include the development of model that incorporates non-linear properties of control and for further work investigating gait and balance from a dynamical systems perspective. / School of Physical Education

<p> This thesis research is focused on advancing image processing techniques and algorithms used for detecting skin melanoma. We have modified previous image processing approaches and developed computational algorithms for quantifying morphological features of a mole image. Applying the algorithms to 20 mole images downloaded from educational websites, we have identified three cut-off ratios to distinguish melanoma images from benign mole images. More specifically, the higher the boundary irregularity ratio, and/or the asymmetry ratio, and/or the color variation ratio, the high chance the mole is melanoma leading. The irregularity ratio cutoff is identified as 1.96, suggesting 96% more circumference length than that of a circle with the same area. One finds that the cut-off ratio for assessing asymmetry of the mole image is 0.109, representing the degree of asymmetry as approximately 11% to place a mole image into the melanoma group. Evaluation of the color variation of the moles leads to a cut-off ratio of the color variation as 0.334. Statistical analyses have been performed to determine the confidence of cut-off ratios, varying from 63% to 81%, for placing a mole image into its correct groups. The algorithms have also been implemented to assess "changes" of mole images over time observed by a dermatologist. Using a &plusmn;14% as the definition of changes, the algorithm identifies 9 of the 10 mole images as changed over time. Among the irregularity, asymmetry, color variation, and size ratios, 5 out of the 9 moles have shown changes in one ratio, 2 out the 9 moles have experience changes in two ratios, 1 mole has shown changes in three ratios, and only 1 mole shows changes in all four ratios. The computational results are consistent with the general observations that human eyes are sensitive to size changes and color variation changes, and may not be very good to distinguish changes in border irregularity and asymmetry. The developed algorithms can be helpful to assist a physician in evaluating subtle changes of mole images that may not be very sensitive to the eyes.</p>

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Vaulting is a discipline in Men's and Women's Artistic Gymnastics. While the springboard contact is not judged, the success of the rest of the vault is underpinned by it. The purpose of this study was to develop an understanding of the mechanics of the springboard contact phase of gymnastic vaulting. An analysis of hopping in place, forward hopping and running jumps on a force platform showed that the force-mass centre displacement relationship during ground contact approximated that of a mass rebounding on a linear spring. Subsequently, two mass-spring models were developed using a symbolic mathematics package. Both models represented the gymnast as a rigid cylinder, with personalized linear and angular inertia characteristics, connected at its mass centre to a linear spring. A one spring model combined the springiness of the gymnast and the springboard in a single linear spring, while a two spring model treated them as separate linear springs. Handspring vaults performed by an elite male gymnast at a range of approach speeds and springboard settings were analysed to provide model inputs. Springboard properties were empirically determined and revealed that the springboard stiffness varied appreciably depending upon feet contact position. Given the touchdown kinematics and takeoff angle of the gymnast, the models estimated spring stiffness and linear and angular takeoff velocities, the spring stiffness and takeoff vertical velocity estimates showing some sensitivity to spring angle at touchdown. Simulations in which the touchdown kinematics and spring stiffnesses were systematically adjusted, identified their influence on takeoff kinematics and provided an insight into the mechanics of springboard. contact. Estimated (leg) spring stiffnesses were consistent with those reported in the literature for other activities and'simulation results showed that simple rebounds accounted for the majority of the takeoff velocities. Spring angle at touchdown was found to be most effective at modifying each of the takeoff variables, however to produce a selective effect on takeoff required a combination of adjustments to the touchdown. In proposing strategies for gymnasts, their ability to control each of the touchdown variables has to be considered.