In this research, two actuation systems were introduced, inertial and magnetic actuation. In the inertial actuation, the robot used the transfer of momentum to navigate, and this momentum could be generated by spinning masses and wheels. Recent studies in our System Laboratory proved that a wide range of inertially actuated locomotion systems could be generated. This can be achieved by using a family tree approach, starting from a very simple system, and progressively evolving it to more complex ones. The motion diversity of these robots inspired us to extend their locomotion from a macro scale to millimeter and micro scales. This dissertation was devoted to studying the control and locomotion of inertially and magnetically actuated multi-scale robotic systems. Three different robotic scales were presented: macro robot, millirobot, and microrobot. The work was significant because it showed that the agility and maneuverability of motion modes generated by inertial actuation could also be generated by magnetic actuation for smaller-scale robotic systems.
We first introduced the wheeled baton robot, which is an inertially-actuated car-like robot. The main advantage of this robot was that it could function in a simple wheeled vehicle mode as well as many other dynamic modes. Inertial actuation enabled the robot to perform high mobility maneuvers and in-air acrobatics. A mathematical model was developed, and different modes of motion of the system were identified, and the equations of motion were derived. Then, a modal transition flow diagram was presented based on the actuation torques. We designed a nonlinear tracking controller to regulate the control variables to implement the described modes of motion. Finally, we designed and built an experimental prototype to verify the existence of the locomotion modes. We demonstrated experimentally that a simple car-like robot could generate several locomotion modes.
An external magnetic field can be used in remotely controlling magnetic millirobots and microrobots, making them promising candidates for biomedical and engineering applications, including cell manipulation and therapy. This work presented a low-cost millirobot that was simple in design, easy to fabricate, highly scalable, and can be used as modular sub-units within complex structures for large-scale manipulation. Individual millirobots were highly agile and capable of performing a variety of locomotive tasks such as pivot walking, tapping, and tumbling. A comparative study was presented to demonstrate the advantages and disadvantages of each locomotion mode. Our experimental data showed that the pivot walking was the fastest and the most stable of the motion modes examined. Further, we focused on the pivot walking mode, and a mathematical model of the system was developed, and the kinematic model was derived. We proposed two controllers to regulate the gait of the pivot walker. The first one was a proportional-geometric controller. The second controller was based on a gradient descent optimization technique. These control algorithms enabled the robot to generate stable gait while tracking a desired trajectory. Using simulations, the robustness of proposed controllers was established for different sweep angles. The two controllers exhibited excellent performance. Finally, to extend the functionality of our millirobots, we presented two systems utilizing multiple millirobots combined: a stag beetle and a carbot. Using a powerful electromagnetic coil system, we conducted extensive experiments to establish feasibility and practical utility of the magnetically actuated millirobot.
Following the successful magnetically actuated millirobot, we extended this research to a micro-scale. We presented a teleoperation scheme to control magnetically actuated microrobots. The system was developed to allow human operators to control the motion for magnetically actuated microrobots and feel their interactions with the environment. A haptic interface constituted the core of the teleoperation system. It was used to provide the operator with force feedback to control the microrobots. In particular, virtual interaction forces were computed and transmitted to the human operators to guide them in performing path following tasks. The operating field of the microrobots was haptically rendered to avoid contacts with obstacles. Finally, a basic set of experimental trials were conducted, demonstrating that the average path tracking error was reduced by 67% when haptic feedback was used.
Bioengineering and Biomedical Engineering, Mechanical Engineering
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Al Khatib, Ehab, "Control and Locomotion of Inertially and Magnetically Actuated Multi-Scale Robotic Systems" (2020). Mechanical Engineering Research Theses and Dissertations. 26.
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