Distributed Extremum-Seeking Control with Applications to High-Altitude Balloons

The real-time optimization of large-scale systems is a difficult problem due to the need for complex models involving uncertain parameters and the high computational cost of solving such problems by a decentralized approach. Extremum-seeking control (ESC) is a model-free real-time optimization technique which can estimate unknown parameters and can optimize nonlinear time-varying systems using only a measurement of the cost function to be minimized. In this thesis, we develop a distributed version of extremum-seeking control which allows large-scale systems to be optimized without models and with minimal computing power. First, we develop a continuous-time distributed extremum-seeking controller. It has three main components: consensus, parameter estimation, and optimization. The consensus provides each local controller with an estimate of the cost to be minimized, allowing them to coordinate their actions. Using this cost estimate, parameters for a local input-output model are estimated, and the cost is minimized by following a gradient descent based on the estimate of the gradient. Next, a similar distributed extremum-seeking controller is developed in discrete-time. Finally, we consider an interesting application of distributed ESC: formation control of high-altitude balloons for high-speed wireless internet. These balloons must be steered into a favourable formation where they are spread out over the Earth and provide coverage to the entire planet. Distributed ESC is applied to this problem, and is shown to be effective for a system of 1200 ballons subjected to realistic wind currents. The approach does not require a wind model and uses a cost function based on a Voronoi partition of the sphere. Distributed ESC is able to steer balloons from a few initial launch sites into a formation which provides coverage to the entire Earth and can maintain a similar formation as the balloons move with the wind around the Earth.

Measuring Scope of Practice Enactment among Primary Care Registered Nurses in Ontario

Background: Primary care is the sector of health care in which patients first establish contact with the health system, are provided person-focused care over time for all new or common needs, and receive coordinated integrated health services provided elsewhere by other members of the health care team. Registered Nurses (RNs) in Canada provide care within this sector in varying roles. The extent to which RNs enact their full scope of practice in primary care settings in Canada is not known. The Actual Scope of Practice questionnaire (ASCOP) is a 26 item Likert scale questionnaire developed by researchers in Canada and validated in the acute care setting to measure the extent to which RNs apply the knowledge, skills and competencies of the professional full scope of practice. Similar to the acute care setting, there is a need to measure scope of practice enactment in the primary care setting. Objectives: The overall aim of this thesis was to measure scope of practice enactment in the primary care setting. Two research objectives were addressed: (1) to revise and adapt the ASCOP questionnaire for use in the primary care setting, and (2) to determine internal consistency, construct validity, and sensitivity of the modified instrument, the ASCOP-PC. Methods: To address the first objective, a narrative literature review and synthesis and an expert panel review was conducted. To address the second objective a cross-sectional survey of 178 RNs working in primary care organizations in Ontario was conducted Results: The ASCOP, with few modifications, addressed key attributes of nursing scope of practice in the primary care setting. The ASCOP-PC yielded acceptable alpha coefficients ranging from 0.66 to 0.91 and explained variances from 44.2 to 62.6. Total mean score of 5.16 suggests that RNs within these models of care almost always engage in activities reflected in the ASCOP-PC. Interpretation: Findings from this study support the use of a the modified ASCOP questionnaire as a reliable and valid measure of scope of practice enactment among primary care nurses in the primary care setting.