Date of Award
Doctor of Philosophy (PhD)
Mechanical & Aerospace Engineering
Mechanical micro-drilling finds widespread use in diverse applications ranging from advanced manufacturing to medical surgery. This dissertation aims to develop techniques that allow programming of robots to perform effective micro-drilling tasks. Accomplishing this goal is faced with several challenges. Micro-drills suffer from frequent breakage caused from variations in drill process parameters. Micro-drilling tasks afford extremely low feed rates and almost zero tolerance for any feed rate variations. The accompanying robot programming task is made difficult as mathematical models that capture the micro-drilling process complexities and sensitive variations in micro-drill parameters are highly difficult to obtain. Therefore, an experimental approach is adopted to identify the feasible parameter space by carrying out a systematic characterization of the tool-specimen interaction that is crucial for understanding the robotic micro-drilling process. The diameter of the hole to be drilled on a material is a primary defining factor for micro-drilling. For the purposes of this dissertation, micro-drills are defined as having a diameter less than or equal to 1 mm. The Sawyer and KUKA collaborative robots that meet the sensitive speed requirements have been chosen for this study. A regression analysis revealed a relationship between feed rate and reaction forces involved in the micro-drilling process that matched the underlying mathematical model of the tool-specimen interactions. Subsequently, this dissertation addresses the problem of destabilization in robotic micro-drilling caused by the low impedance of the collaborative robot’s cantilever structure. A semi-robotic method that combines force-controlled adaptive drill feed rate and human-assisted impedance enhancement strategy is developed to address the destabilization problem. This approach is inspired by the capability of humans to stabilize unstable dynamics while performing contact-based tasks by using selective control of arm mechanical impedance. A human-robot collaborative kinesthetic drilling mode was also developed using the selective compliance capability of the KUKA robot. Experimental results show that the Sawyer and KUKA robots can use the developed strategies to drill micro-holes of diameters up to a minimum of 0.6 mm and 0.2 mm, respectively. Finally, experiments involving drilling in different materials reveal the potential application of the collaborative robotic micro-drilling approach in composite repairs, micro-channels, dental drilling, and bone drilling.
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"Collaborative Robotics Strategies for Handling Non-Repetitive Micro-Drilling Tasks Characterized by Low Structural Mechanical Impedance"
(2022). Doctor of Philosophy (PhD), Dissertation, Mechanical & Aerospace Engineering, Old Dominion University, DOI: 10.25777/jek8-dq16