Modular Continuum Mobile Robot: Design, Modeling, and Motion Planning

Sun, Yinan

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Modular Continuum Mobile Robot: Design, Modeling, and Motion Planning

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Snakes and other creatures with flexible continuous bodies are a remarkable source of inspiration for mobile search-and-rescue robots. Their unique slender body structure and multiple locomotion modes are well-suited to negotiate with highly unstructured and unpredictable environments. The design, manufacturing, modeling, and control techniques of snake robots make it possible to imitate the structure, mechanical properties, and locomotion gaits of snakes, opening up new possibilities in robotics research. Unlike the creatures, most of existing snake robots are modular designed with rigid structures for locomotion conducting. The lack of flexibility reduces the snake robots' potential of adapt to complex environment. Continuum robots are also well-suited to rescue and exploration applications because of their flexible and continuous structure. Continuum solutions are widely utilized on novel manipulators, presenting promising potential as robotic tools because of their ability to safely conform to the shape of the objects and environments they interact with. The unique property to perform shape changing on their structure, such as length, bending angle, and bending direction continuously along their arc length, makes them possible to negotiate much more complicated environments. However, considering their versatility, continuum robots also offer great potential to be configured as mobile robots for search-and-rescue applications in unstructured environments. In this dissertation, novel mobile robots are presented, combining the modular design of snake robots and the flexible continuous structure from continuous robots, which enables their potential of multiple locomotion modes and the ability to negotiate complex environments. This dissertation introduce our research work on a continuum mobile snake robot purely inspired by natural snakes with slender body, and a continuum salamander robot inspired partially by salamanders, combined with suitable engineering techniques for better performance. The continuum soft snake robot is made of modules that can actively deform in 3D. We conducted rigorous studies to access its performance under a range of conditions, including gait parameters, number of modules, and different environmental conditions. We developed a flexible 3D-printed wave-spring sheath to support the robot modules, increasing the snake’s performance in climbing steps three-fold. Finally, we introduce a simulator and a numerical model to provide a real-time simulation of the soft robotic snake. With the help of the real-time simulator, it is possible to develop and test new locomotion gaits for the soft robotic snake within a short period of time, compared to experimental trial and error. As a result, the soft robotic snake presented in this dissertation is able to traverse diverse surfaces, perform several bio-inspired and custom gaits, and climb over steps. The continuum salamander robot consists of a cable-driven bellows-like origami module mounted between sets of powered wheels. The origami structure allows the body to deform as necessary to adapt to complex environments and terrains, while the wheels allow the robot to reach speeds of up to 303.1~mm/s (2.05~body-length/s). Considering the unique locomotion of this mobile robot, we analyze the locomotion under experimental results and reasonable assumptions, then build a Euler-spiral-based kinematics model to describe the continuum robot motion. Based on the model, we also explore feasible motion planning methods and deploy on the robot in real world experiments.

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