The following thesis applies equations of motion used in linear locomotion (gait analysis) to the analysis of the purely rotational motion of the fouetté or tour à la seconde. Modifications to the method of analysis include the creation of several MATLAB programs to compute improved estimates of the moment of inertia tensor, three-dimensional angular momentum about the dancer’s centre of mass. The results of this investigation—the quantification of angular momentum and external moments—are compared to similar results from gait analysis to demonstrate how the dancer maintains balance during rotational motion. The variables calculated by the MATLAB programs are particularly relevant in the field of balance control research in the context of inputs into the body’s balance control systems.

Bicycle dynamics and behaviors have been vastly studied through modeling and simulation. Due to the complexity, software models are often assumed subjecting to di erent nonholonomic constraints in order to simplify the models and control algorithms. A real life autonomous bicycle faces perturbances from the road, wind, tire deformation, slipping among other external forces. Limitations of simulations will not always allow these to apply. All these issues make the autonomous bicycle research very challenging. To study the bicycle control problems a few research results from the literature are reviewed. A nonlinear bicycle model was used to conduct control simulations. Model based nonlinear controllers were applied to simulate the balance and path tracking control. A PID controller is more practical to replace the non-linear controller for the balance control. Simulation results of the di erent controllers are compared in order to decide the proper control strategies on the hardware platform. The controller design of the platform complies with practicality based on the hardware con guration. Two control schemes are implemented on the test platform; both are developed with PID algorithms. The rst scheme is a single PID control loop in which the controller takes the roll angle feedback and balances the running platform by means of steering. If the desired roll angle is zero the controller will try to hold the platform at the upright position. If the desired roll angle is non-zero the platform will be balanced at an equilibrium roll angle. A xed roll angle will lead to a xed steering angle as the result of balance control. The second scheme is directional control with balance consisting of two cascaded PID loops. Steering is the only means to control balance and direction. To do so the desired roll angle must be controlled to achieve the desired steering angle. The platform tilts to the desired side and steering follows to the same side of the tilt; the platform can then be lifted up by the centrifugal force and eventually balanced at an equilibrium roll angle. The direction can be controlled using a controlled roll angle. Many implementation issues have to be dealt with in order for the control algorithm to be functional. Dynamic roll angle measurement is implemented with complementary internal sensors (accelerometer and gyroscope). Directional information is obtained through a yaw rate gyroscope which operates on the principle of resonance. To monitor the speed of the platform, a rotational sensor was formed by using a hard drive stepper motor attached to the axis of the vehicle's driving motor. The optoelectronic circuit plays the vital role to ensure the system functionality by isolating the electromagnetic noise from the motors. Finally, in order to collect runtime data, the wireless communication is implemented through Bluetooth/RS232 serial interface. The data is then plotted and analyzed with Matlab. Controller gains are tuned through numerous road tests. Field test results show that the research has successfully achieved the goal of testing the low level control of autonomous bicycle. The developed algorithms are able to balance the platform on semi-smooth surfaces. / UOIT

The following thesis applies equations of motion used in linear locomotion (gait analysis) to the analysis of the purely rotational motion of the fouetté or tour à la seconde. Modifications to the method of analysis include the creation of several MATLAB programs to compute improved estimates of the moment of inertia tensor, three-dimensional angular momentum about the dancer’s centre of mass. The results of this investigation—the quantification of angular momentum and external moments—are compared to similar results from gait analysis to demonstrate how the dancer maintains balance during rotational motion. The variables calculated by the MATLAB programs are particularly relevant in the field of balance control research in the context of inputs into the body’s balance control systems.

The following thesis applies equations of motion used in linear locomotion (gait analysis) to the analysis of the purely rotational motion of the fouetté or tour à la seconde. Modifications to the method of analysis include the creation of several MATLAB programs to compute improved estimates of the moment of inertia tensor, three-dimensional angular momentum about the dancer’s centre of mass. The results of this investigation—the quantification of angular momentum and external moments—are compared to similar results from gait analysis to demonstrate how the dancer maintains balance during rotational motion. The variables calculated by the MATLAB programs are particularly relevant in the field of balance control research in the context of inputs into the body’s balance control systems.

The following thesis applies equations of motion used in linear locomotion (gait analysis) to the analysis of the purely rotational motion of the fouetté or tour à la seconde. Modifications to the method of analysis include the creation of several MATLAB programs to compute improved estimates of the moment of inertia tensor, three-dimensional angular momentum about the dancer’s centre of mass. The results of this investigation—the quantification of angular momentum and external moments—are compared to similar results from gait analysis to demonstrate how the dancer maintains balance during rotational motion. The variables calculated by the MATLAB programs are particularly relevant in the field of balance control research in the context of inputs into the body’s balance control systems.

Understanding possible variations in muscle activation patterns and its functional implications to movement control is crucial for rehabilitation. Inter-/intra-subject variability is often observed in muscle activity used for performing the same task in both healthy and impaired individuals. However, the extent to which muscle activation patterns can vary under specific neuromuscular conditions and differ in function are still not well understood. Current musculoskeletal modeling approaches using optimization techniques to identify a unique solution cannot adequately address such questions. Here I developed a novel computational framework using detailed musculoskeletal model to reveal the latitude the nervous system has in selecting muscle activation patterns for a given task regarding neuromechanical constraints. I focused on isometric hindlimb endpoint force generation task relevant to balance behavior in cats. By identifying the explicit bounds on activation of individual muscles defined by biomechanical constraints, I demonstrate ample range of feasible activation patterns that account for experimental variability. By investigating the possible neuromechanical bases of using the same muscle activation pattern across tasks, I demonstrate that demand for generalization can affect the selection of muscle activation pattern. By characterizing the landscape of the solution space with respect to multiple functional properties, I demonstrate a possible trade-off between effort and stability. This framework is a useful tool for understanding principles underlying functional or impaired movements. We may gain valuable insights to developing effective rehabilitation strategies and biologically-inspired control principles for robots.

The high incidence of falls and fall-related injuries among Canadians over the age of 65 continues to be a key public health issue. As the current proportion of individuals within this cohort of the population is predicted to double by the year 2031, the absolute number of individuals experiencing falls, fall-related injuries and subsequent hospitalization will increase dramatically. While a fall in any direction can lead to injury and reduced quality of life, lateral falls have been shown to be prevalent and can be particularly devastating because of the increased probability of hip fracture. Forward stepping tasks, whether initiated volitionally or by external perturbation, pose a challenge to stability, as they require the precise regulation of the spatial and temporal characteristics of the whole body centre of mass (COM) in relation to a changing base of support (BOS). Despite our understanding of both proactive and reactive mechanisms for balance control at movement initiation during such stepping tasks, there appears to be little understanding or consensus regarding the origins of age-related decline in mediolateral stability, which can manifest during the restabilisation phase, at movement termination. From this, the global objective of this thesis was to develop further understanding regarding such age-related differences in mediolateral dynamic stability control during the restabilisation phase of forward stepping. Notwithstanding the well documented differences between volitional and perturbation-evoked stepping until the time of foot-contact, we have proposed the control of the COM during the restabilisation phase of such stepping tasks to be a central determinant of age-related differences in mediolateral dynamic stability, common to both forms of stepping. We quantified the COM kinematics during the restabilisation phase and calculated the magnitude of incongruity between the peak and final, stable, COM position, in addition to the intertrial variability of this incongruity. Further, we analysed the orientation of the net ground reaction force (GRF) with respect to the COM, which allowed us to draw conclusions regarding the mechanisms that may be responsible for the age-related differences in the COM kinematics. To vary the challenge to control, we included conditions in which individuals were required to step with altered step width. In addition, we attempted to probe the extent and means by which individuals could alter the dynamics of stepping over time, with trial repetition. In general, we found that overshoots of the final COM position were common to all forms of stepping and may serve the functional role of simplifying reactive control during the restabilisation phase. The magnitude and intertrial variability of incongruity, however, were greater among the older adults during all forms of stepping. We believe such increased COM incongruity is likely indicative of greater instability within this group, which may be associated with the increased time required to reorient the net GRF in a manner necessary to oppose the total body angular momentum that developed during the swing phase. Particularly interesting was the use of proactive strategies by older adults, which may have the potential to offset instability that arises due to difficulty with reactive control during the restabilisation phase. The present work provides support for previous studies, which have suggested that the control of mediolateral stability may be particularly challenging for older adults. Further, our work provides evidence that the challenges associated with mediolateral stability control have important links to the restabilisation phase and are common to both volitional and reactive stepping. This work highlights the need to further explore the control of mediolateral stability and develop therapeutic interventions to reduce such incidence of instability among older adults.

The high incidence of falls and fall-related injuries among Canadians over the age of 65 continues to be a key public health issue. As the current proportion of individuals within this cohort of the population is predicted to double by the year 2031, the absolute number of individuals experiencing falls, fall-related injuries and subsequent hospitalization will increase dramatically. While a fall in any direction can lead to injury and reduced quality of life, lateral falls have been shown to be prevalent and can be particularly devastating because of the increased probability of hip fracture. Forward stepping tasks, whether initiated volitionally or by external perturbation, pose a challenge to stability, as they require the precise regulation of the spatial and temporal characteristics of the whole body centre of mass (COM) in relation to a changing base of support (BOS). Despite our understanding of both proactive and reactive mechanisms for balance control at movement initiation during such stepping tasks, there appears to be little understanding or consensus regarding the origins of age-related decline in mediolateral stability, which can manifest during the restabilisation phase, at movement termination. From this, the global objective of this thesis was to develop further understanding regarding such age-related differences in mediolateral dynamic stability control during the restabilisation phase of forward stepping. Notwithstanding the well documented differences between volitional and perturbation-evoked stepping until the time of foot-contact, we have proposed the control of the COM during the restabilisation phase of such stepping tasks to be a central determinant of age-related differences in mediolateral dynamic stability, common to both forms of stepping. We quantified the COM kinematics during the restabilisation phase and calculated the magnitude of incongruity between the peak and final, stable, COM position, in addition to the intertrial variability of this incongruity. Further, we analysed the orientation of the net ground reaction force (GRF) with respect to the COM, which allowed us to draw conclusions regarding the mechanisms that may be responsible for the age-related differences in the COM kinematics. To vary the challenge to control, we included conditions in which individuals were required to step with altered step width. In addition, we attempted to probe the extent and means by which individuals could alter the dynamics of stepping over time, with trial repetition. In general, we found that overshoots of the final COM position were common to all forms of stepping and may serve the functional role of simplifying reactive control during the restabilisation phase. The magnitude and intertrial variability of incongruity, however, were greater among the older adults during all forms of stepping. We believe such increased COM incongruity is likely indicative of greater instability within this group, which may be associated with the increased time required to reorient the net GRF in a manner necessary to oppose the total body angular momentum that developed during the swing phase. Particularly interesting was the use of proactive strategies by older adults, which may have the potential to offset instability that arises due to difficulty with reactive control during the restabilisation phase. The present work provides support for previous studies, which have suggested that the control of mediolateral stability may be particularly challenging for older adults. Further, our work provides evidence that the challenges associated with mediolateral stability control have important links to the restabilisation phase and are common to both volitional and reactive stepping. This work highlights the need to further explore the control of mediolateral stability and develop therapeutic interventions to reduce such incidence of instability among older adults.

Yes / Older people have an increased risk of falling during locomotion, with falls on stairs being particularly common and dangerous. Step going (i.e., the horizontal distance between two consecutive step edges) defines the base of support available for foot placement on stairs, as with smaller going, the user's ability to balance on the steps may become problematic. Here we quantified how stair negotiation in older participants changes between four goings (175, 225, 275, and 325 mm) and compared stair negotiation with and without a walking approach. Twenty-one younger (29 ± 6 years) and 20 older (74 ± 4 years) participants negotiated a 7-step experimental stair. Motion capture and step-embedded force platform data were collected. Handrail use was also monitored. From the motion capture data, body velocity, trunk orientation, foot clearance and foot overhang were quantified. For all participants, as stair going decreased, gait velocity (ascent pA = 0.033, descent pD = 0.003) and horizontal step clearance decreased (pA = 0.001), while trunk rotation (pD = 0.002) and foot overhang increased (pA,D < 0.001). Compared to the younger group, older participants used the handrail more, were slower across all conditions (pA < 0.001, pD = 0.001) and their foot clearance tended to be smaller. With a walking approach, the older group (Group x Start interaction) showed a larger trunk rotation (pA = 0.011, pD = 0.015), and smaller lead foot horizontal (pA = 0.046) and vertical clearances (pD = 0.039) compared to the younger group. A regression analysis to determine the predictors of foot clearance and amount of overhang showed that physical activity was a common predictor for both age groups. In addition, for the older group, medications and fear of falling were found to predict stair performance for most goings, while sway during single-legged standing was the most common predictor for the younger group. Older participants adapted to smaller goings by using the handrails and reducing gait velocity. The predictors of performance suggest that motor and fall risk assessment is complex and multifactorial. The results shown here are consistent with the recommendation that larger going and pausing before negotiating stairs may improve stair safety, especially for older users. / This study was supported by the New Dynamics of Aging (RES-356-25-0037).

Accurately simulating human motions is a major function of and challenge to digital human models and integrating humans in computer-aided design systems. Numerous successful applications of human motion simulation have already demonstrated their ability to improve occupational efficiency, effectiveness, and safety. In this dissertation, a novel motion simulation model using fuzzy logic control is presented. This model was motivated by the fact that humans use linguistic terms to guide their behaviors while fuzzy logic provides mathematical representations of linguistic terms. Specifically in this model, fuzzy logic was used to specify a neural controller which was generally considered as the part in the postural control system that plans human motions. Fuzzy rules were generated according to certain trends observed from actual human motions. An optimization procedure was performed to specify the parameters of the membership functions by minimizing the differences between the simulated and actual final postures. This research contributed to the field of human movement science by providing a motion simulation model that can accurately predict novel human motions and provide interpretations of potential human motion planning strategies. Understanding balance control is another research focus in this dissertation. Investigating balance control may aid in preventing unnecessary fall-related incidents and understanding the postural control system. Since human behaviors are generally effective and efficient, balance control models (both two- and three-dimensional) based on an optimal control strategy were developed to aid in better understanding balance control. Specifically, the neural controller was considered as an optimal controller that minimizes a performance index defined by physical quantities relevant to sway. Free model parameters, such as weights of relevant physical quantities and sensory delay time, were determined by an optimization procedure whose objective was to minimize a scalar error between simulated and experimental center-of-pressure (COP) based measures. Many factors, such as aging, localized muscle fatigue, and external loads, have been found to adversely affect balance control. At the same time, behaviors during upright stance are commonly characterized by COP-based measures. Thus, changes in COP based measures with aging, LMF, and external loads were addressed by using the proposed models, and possible postural control mechanisms were identified by interpreting these changes. Findings from these studies demonstrated that the proposed models were able to accurately simulate human sway behaviors and provide plausible mechanisms regarding how the postural control system works when maintaining upright balance. / Ph. D.