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Currently, attendance issues are prevalent in academic settings. When students do not attend school, it has an effect on their education and on the community at large. This study looked at the issue of truancy at the Early Years level and focused on studying one possible solution: the Walking School Bus Program. In this program two Community Outreach Workers were hired to walk students with attendance issues to school on a daily basis. A qualitative study was completed to obtain the perspectives of key individuals involved in the Walking School Bus program.

The present study validates the Treadmill Rehabilitation Platform (TRP) protocol that assessed standing balance performance; spatial and temporal gait variability; stability measures and visual spatial cognitive task performances. Healthy individuals (mean age = 61.4± 4.4 years; n = 30) performed tasks from the TRP protocol while standing and while walking on treadmill. Moderate to High test retest reliability was observed for the TRP tool measures with a few exceptions. Standing balance decreased significantly as visual task load increased. Spatial and temporal gait variability increased whereas walking stability decreased significantly as visual task load increased. Visual task performance decreased significantly as physical load increased. In conclusion, the TRP protocol allows us to assess the ability to prioritize the division of attention when visual spatial cognitive tasks are performed while standing and during walking. Also, it allows reliable assessment of the effects of compromised attention during the tasks performances.

It has been established that legged, off-road vehicles exhibit better mobility, obtain higher energy efficiency and provide more comfortable movement than those of tracked or wheeled vehicles while moving on rough terrain. Previous studies on legged mechanism design were performed by selecting the length of each link by trial and error or by certain optimization techniques where only a static force analysis was performed due to the complexity of the mechanisms. We found that these techniques can be inefficient and inaccurate. In this paper, we present the design and the optimization of a single degree-of-freedom 8-bar legged walking mechanism. We design the leg using the mechanism design theory because it offers a greater control on the output motion. Furthermore, a dynamic force analysis is performed to determine the torque applied on the input link. The optimization is set up to achieve two objectives: i) to minimize the energy needed by the system and ii) to maximize the stride length. The kinematics and dynamics of the optimized leg mechanism are compared to the one by trial-and-error. It shows that large improvements to the performance of the leg mechanism can be achieved. A prototype of the walking mechanism with 6 legs is built to demonstrate the performance.

Impact at each leg transition is one of the main causes of energy dissipation in most of the current bipedal walking robots. Minimizing impact can reduce the energy loss. Instead of controlling the joint angle profiles to reduce the impact which requires significant amount of energy, installing elastic mechanisms on the robots structure is proposed in this research, enabling the robot to reduce the impact, and to store part of the energy in the elastic form which returns the energy to the robot. Practically, this motivates the development of the bipedal walking robots with adjustable stiffness elasticity which itself creates new challenging problems. This thesis addresses some of the challenges through five consecutive stages. Firstly, an adjustable compliant series elastic actuator (named ACSEA in this thesis) is developed. The velocity control mode of the electric motor is used to accurately control the output force of the ACSEA. Secondly, three different conceptual designs of the adjustable stiffness artificial tendons (ASAT) are proposed each of which is added at the ankle joint of a bipedal walking robot model. Simulation results of the collision phase (part of the gait between the heel-strike and the foot-touch-down in bipedal walking) demonstrate significant improvements in the energetics of the bipedal walking robot by proper stiffness adjustment of ASAT. In the third stage, in order to study the effects of ASATs on reducing the energy loss during the stance phase, a simplified model of bipedal walking is introduced consisting of a foot, a leg and an ASAT which is installed parallel to the ankle joint. A linear spring, with adjustable stiffness, is included in the model to simulate the generated force by the trailing leg during the double support phase. The concept of impulsive constraints is used to establish the mathematical model of impacts in the collision phase which includes the heel-strike and the foot-touch-down. For the fourth stage, an energy-feedback-based controller is designed to automatically adjust the stiffness of the ASAT which reduces the energy loss during the foot-touch-down. In the final stage, a speed tracking (ST) controller is developed to regulate the velocity of the biped at the midstance. The ST controller is an event-based time-independent controller, based on geometric progression with exponential decay in the kinetic energy error, which adjusts the stiffness of the trailing-leg spring to control the injected energy to the biped in tracking a desired speed at the midstance. Another controller is also integrated with the ST controller to tune the stiffness of the ASAT when reduction in the speed is desired. Then, the local stability of the system (biped and the combination of the above three controllers) is analyzed by calculating the eigenvalues of the linear approximation of the return map. Simulation results show that the combination of the three controllers is successful in tracking a desired speed of the bipedal walking even in the presence of the uncertainties in the leg’s initial angles. The outcomes of this research show the significant effects of adjustable stiffness artificial tendons on reducing the energy loss during bipedal walking. It also demonstrates the advantages of adding elastic elements in the bipedal walking model which benefits the efficiency and simplicity in regulating the speed. This research paves the way toward developing the dynamic walking robots with adjustable stiffness ability which minimize the shortcomings of the two major types of bipedal walking robots, i.e., passive dynamic walking robots (which are energy efficient but need extensive parameters tuning for gait stability) and actively controlled walking robots (which are significantly energy inefficient).

The present study validates the Treadmill Rehabilitation Platform (TRP) protocol that assessed standing balance performance; spatial and temporal gait variability; stability measures and visual spatial cognitive task performances. Healthy individuals (mean age = 61.4± 4.4 years; n = 30) performed tasks from the TRP protocol while standing and while walking on treadmill. Moderate to High test retest reliability was observed for the TRP tool measures with a few exceptions. Standing balance decreased significantly as visual task load increased. Spatial and temporal gait variability increased whereas walking stability decreased significantly as visual task load increased. Visual task performance decreased significantly as physical load increased. In conclusion, the TRP protocol allows us to assess the ability to prioritize the division of attention when visual spatial cognitive tasks are performed while standing and during walking. Also, it allows reliable assessment of the effects of compromised attention during the tasks performances.

Impact at each leg transition is one of the main causes of energy dissipation in most of the current bipedal walking robots. Minimizing impact can reduce the energy loss. Instead of controlling the joint angle profiles to reduce the impact which requires significant amount of energy, installing elastic mechanisms on the robots structure is proposed in this research, enabling the robot to reduce the impact, and to store part of the energy in the elastic form which returns the energy to the robot. Practically, this motivates the development of the bipedal walking robots with adjustable stiffness elasticity which itself creates new challenging problems. This thesis addresses some of the challenges through five consecutive stages. Firstly, an adjustable compliant series elastic actuator (named ACSEA in this thesis) is developed. The velocity control mode of the electric motor is used to accurately control the output force of the ACSEA. Secondly, three different conceptual designs of the adjustable stiffness artificial tendons (ASAT) are proposed each of which is added at the ankle joint of a bipedal walking robot model. Simulation results of the collision phase (part of the gait between the heel-strike and the foot-touch-down in bipedal walking) demonstrate significant improvements in the energetics of the bipedal walking robot by proper stiffness adjustment of ASAT. In the third stage, in order to study the effects of ASATs on reducing the energy loss during the stance phase, a simplified model of bipedal walking is introduced consisting of a foot, a leg and an ASAT which is installed parallel to the ankle joint. A linear spring, with adjustable stiffness, is included in the model to simulate the generated force by the trailing leg during the double support phase. The concept of impulsive constraints is used to establish the mathematical model of impacts in the collision phase which includes the heel-strike and the foot-touch-down. For the fourth stage, an energy-feedback-based controller is designed to automatically adjust the stiffness of the ASAT which reduces the energy loss during the foot-touch-down. In the final stage, a speed tracking (ST) controller is developed to regulate the velocity of the biped at the midstance. The ST controller is an event-based time-independent controller, based on geometric progression with exponential decay in the kinetic energy error, which adjusts the stiffness of the trailing-leg spring to control the injected energy to the biped in tracking a desired speed at the midstance. Another controller is also integrated with the ST controller to tune the stiffness of the ASAT when reduction in the speed is desired. Then, the local stability of the system (biped and the combination of the above three controllers) is analyzed by calculating the eigenvalues of the linear approximation of the return map. Simulation results show that the combination of the three controllers is successful in tracking a desired speed of the bipedal walking even in the presence of the uncertainties in the leg’s initial angles. The outcomes of this research show the significant effects of adjustable stiffness artificial tendons on reducing the energy loss during bipedal walking. It also demonstrates the advantages of adding elastic elements in the bipedal walking model which benefits the efficiency and simplicity in regulating the speed. This research paves the way toward developing the dynamic walking robots with adjustable stiffness ability which minimize the shortcomings of the two major types of bipedal walking robots, i.e., passive dynamic walking robots (which are energy efficient but need extensive parameters tuning for gait stability) and actively controlled walking robots (which are significantly energy inefficient).

It has been established that legged, off-road vehicles exhibit better mobility, obtain higher energy efficiency and provide more comfortable movement than those of tracked or wheeled vehicles while moving on rough terrain. Previous studies on legged mechanism design were performed by selecting the length of each link by trial and error or by certain optimization techniques where only a static force analysis was performed due to the complexity of the mechanisms. We found that these techniques can be inefficient and inaccurate. In this paper, we present the design and the optimization of a single degree-of-freedom 8-bar legged walking mechanism. We design the leg using the mechanism design theory because it offers a greater control on the output motion. Furthermore, a dynamic force analysis is performed to determine the torque applied on the input link. The optimization is set up to achieve two objectives: i) to minimize the energy needed by the system and ii) to maximize the stride length. The kinematics and dynamics of the optimized leg mechanism are compared to the one by trial-and-error. It shows that large improvements to the performance of the leg mechanism can be achieved. A prototype of the walking mechanism with 6 legs is built to demonstrate the performance.

Background & Objectives: Participation in cognitive, social and physical activity (PA) may play a role in prevention of cognitive decline in older adults. Literature supporting the benefits of healthy lifestyle behaviours, especially PA, on cognition continues to accumulate. Moreover, a strong association between gait and cognitive health is increasingly being recognized. Yet, a firm understanding of the individual differences and between-person effects of PA on cognition and gait of older adults is lacking. Thus, the primary objective of the main study was to distinguish the within- and between-person sources of variation in PA on cognition in a group of inactive older adults. Study 2 examined the within- and between-person effects of a) PA on gait and b) gait on cognition. Study 3 examined the social cognitive predictors of walking. Methods: The between- and within-person of PA on cognition were examined in a single-group longitudinal design. Participants (n=159) were enrolled in a four-month supervised walking program and provided with materials and coaching to promote the adoption of behaviours to enhance and maintain their cognitive health. Group participants walked at least 3 times per week at a brisk intensity and were encouraged to get 150 minutes of moderate-to-vigorous PA per week. At baseline, participants completed measures of social cognitive predictors of walking. Assessments of cognition, diet, fitness, gait, PA and other health behaviours occurred at baseline, and at 6, 9, 12, and 16 weeks follow-up. Results and Discussion: Multilevel models revealed significant: 1) within-person effects of PA on select measures of executive functioning and 2) consistent between-group effects of cognitive activity, but not other lifestyle behaviours, on cognition. Study 2 revealed consistent significant 1) within-person effects of PA on gait velocity and stride time variability during dual task walking, 2) between-person effects of PA on gait velocity during both dual task and normal walking, and 3) between-person effects of gait velocity and stride time variability on cognition during both normal and dual task walking. Significant within-person effects of gait on cognition were limited. In study 3, self-monitoring emerged as a significant predictor of change in walking. Conclusion: Distinct patterns of within- and between-person effects on the PA, cognition and gait were observed. Further work will need to continue to clearly elucidate the within- and between-person sources of variation in relations between PA, gait and cognition using well-designed longitudinal and experimental designs. / Graduate / 0633 / 0623 / kkowalsk@uvic.ca

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