In the friction stir welding (FSW) process, heat and mechanical work are coupled to produce a solid state weld. The process variables are pin tool rotation speed, translational weld speed, and downward plunge force. The strain-temperature history of a metal element at each point on the cross-section of the weld is determined by the process variables plus the individual flow path taken by the particular filament of metal flowing around the tool and ending on that point. The strain-temperature history determines the properties of a metal filament on the weld cross-section. To control the mechanical properties, the strain-temperature history must be carefully controlled. Indirect estimates of the flow paths and the strain-temperature histories of filaments comprising friction stir welds can be made from a model, if the model provides sufficient information. This paper describes experimental marker studies designed to trace the metal flow streamlines as influenced by variations in the process parameters.

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<p>This thesis investigates two significant problems in control and coordination of complex teleoperation systems as they relate to the operation of a mobile robotic manipulator. The first part of the thesis focuses on the design of a control framework to resolve kinematic redundancy in teleoperation of a mobile robotic manipulator. Apart from the redundancy, workspace considerations for the operator and robot and asymmetry of master and slave systems pose significant design challenges in such telerobotic systems . The second part of the thesis considers psychophysical aspects of teleoperation from the operator's perspective. This part presents a method for automatic {\em optimal} positioning of a single camera for a remotely navigated mobile robot in systems with a controllable camera platform. In each part, a constrained optimization problem is formulated and solved in real time. The solution of these optimization problems are integrated seamlessly into the teleoperation control framework in order to assist the operator in accomplishing the main task. The proposed control framework in the first part allows the operator to concentrate on the manipulation task while the mobile base and arm joint configurations are automatically {\em optimized} according to the needs of the task. Autonomous control subtasks are defined to guide the base and the arms towards this optimal configuration while the operator teleoperates the end-effector(s) of the mobile arm(s). The teleoperation and autonomous control tasks have adjustable relative priorities set by the system designer. The work in the second part enables the operator to focus mainly on navigation and manipulation while the camera viewpoint is automatically adjusted. The workspace and motion limits of the camera system and the location of the obstacles are taken into consideration in camera view planning. A head tracking system enables the operator to use his/her head movements as an extra control input to guide the camera placement, if and when necessary. Both proposed controllers have been implemented and evaluated in teleoperation experiments and user studies. The results of these experiments confirm the effectiveness of these controllers and demonstrate significant improvements compared to other existing controllers from the literature included in the studies.</p> / Master of Applied Science (MASc)