Eversion in Inflatable Soft Robotics: Actuators & Robots

To overcome problems associated with actuation and safe human-robot interaction, researchers have taken inspiration from nature - specifically from plant life (vines and roots) and from the animal kingdom, examples being elephant trunks and octopus arms. This effectively led to the emergence of a new field within robotics - that of soft robotics. Its key goal was to address the issue of safety in human-robot interaction, which had always been problematic when working with traditional rigid non-compliant devices. Soft robots, on the other hand, are compliant by definition. As the title indicates, this dissertation focuses on two key topics: soft robotic structure, which comprises robots and actuators, and eversion-based growth (elongation) when actuated. Soft robotics also involves the development of soft actuators which are used in applications such as rehabilitation, search and rescue, and in a variety of medical procedures. As a rule, current soft actuators either apply low force as they are made from soft materials or have limited stroke length because of design constraints. In order to address these issues, this dissertation proposes a novel eversion-based elongating actuator. The proposed soft eversion actuator (i) applies greater force, (ii) elongates along its longitudinal axis by tens of meters resulting in greater stroke length, and (iii) varies its structural stiffness. While the eversion principle has had some degree of traction in relation to robots themselves, it has not need considered n relation to actuation. This Ph.D. dissertation proposes novel inflatable structures capable of elongating and contracting along the main axis by way of the eversion principle for actuation purposes. The developed actuators prove to be superior with regards to stroke length, energy to force relationship, weight, and ease of integrability, than other linear actuators (such as dielectric actuators, McKibben Muscles, etc.). This dissertation aims to evaluate the new eversion actuator for a range of applications. A methodology for developing soft eversion actuators from fabric is also presented and discussed. Among other benefits, the use of fabric reduces the construction time when compared to rubber based soft robots. The strength of fabric-based actuators is demonstrated by creating a soft wearable glove for the telerehabilitation therapy of clenched hand/fingers patients, and a soft inflatable structure with variable stiffness for hand rehabilitation. As actuators are part of a (robotic) system, the effectiveness of the proposed eversion actuator is demonstrated through an artificial muscle used in rehabilitation. Navigation of the growing eversion robot using inflatable pouches is also discussed, with reference to specific applications such as field of inspection, search-rescue, exploration, and tasks in hazardous or inaccessible environments. The pouches that enable bending are integrated into the body of eversion robot, and using the proposed technique, the robot achieves a bend angle of almost 146o, with an average standard deviation of less than 2o. Control schemes for the robot are also discussed, followed by a brief study of the implementation of the robot in an extreme environment