This dissertation outlines the design and development of the first fully-soft, snake robot and its snake-inspired skin. Soft robotics takes advantage of soft materials to, among other things, improve robot interactions with complex, unstructured environments. Due to the interplay between the soft material and the environment, minor tweaks to the morphological design of the robot can produce major changes in behavior when using the same control input. The research goal of this dissertation was to determine how the locomotion a soft snake robot, using a lateral undulation gait, can be improved by targeting a specific environmental interaction through the confluence of body design, gait design, and interfacial mechanism design.
Understanding how these three areas of design can affect one another is key in developing robots that are adaptable in a range of environments. Each design area is addressed in a chapter of this dissertation to illustrate how changes to one area propagate to others, and how that can be an advantage to improving the locomotion of a soft robot. Chapter 3 examines how the body design of the robot changes its locomotion capabilities in granular media, focusing on interactions between the body and the ridges formed in the media. Chapter 4 illustrates how improvements to the gait can also be driven by interactions between the robot's body and the granular media.
The design and implementation of an interfacial mechanism to further improve locomotion is described in Chapter 5. Kirigami, a Japanese art form involving the patterning of cuts in thin materials, is used to create a snake-inspired skin. The skin design targets directional friction, a morphological characteristic vital to snake locomotion in two axes. Most skins implemented for snake robots focus only on the longitudinal axis for creating directional friction. However, lateral undulation, the gait employed throughout this work, requires a significant lateral resistance to successfully create locomotion. This interfacial mechanism is designed specically for the kinematics of the soft actuators as well as the production of directional friction in two axes, which required the creation of a new set of radial kirigami lattices.
Each chapter demonstrates how improvements to locomotion can come from designing the morphological characteristics of the robot alongside the development of a gait and interfacial mechanisms by targeting specific, bioinspired interactions between the robot and the environment. The final iteration of system resulted in a soft robot and it's snake-inspired skin with a 530% improvement in velocity over the original robot with no skin. The main contributions of this dissertation are:
1. The development of the first fully-soft snake robot.
2. A skin for lateral undulation with two axes of directional friction
3. A set of new kirigami lattice structures that can be used for bending actuators
4. A framework in which to investigate bioinspired design of robots in three areas of design: morphology, gait, and interfacial mechanisms.