<p>Traditional robots and soft robots have often been treated as two distinct options for design, a dichotomy between stiffness and compliance. In reality, they compose two ends of a spectrum, and there has been research to soften traditional robots and stiffen soft robots. The latter option has seen a large variety of techniques to actively and selectively create stiffness in an otherwise soft robot. The common disadvantage concerning all of them is the need for constant energy input. In this work, a first-of-its-kind method for a permanent stiffness of a growing robot is explored and tested.</p> <p>First, I show the qualitative and quantitative testing of the stiffening method, expanding insulation foam, both by itself and when applied to a vine robot. With this knowledge, I investigate a design to apply the foam to a growing robot as it moves, taking advantage of the properties of the foam to coat a vine robot as needed. This selective foam placement unlocks various unique capabilities like adhering to its environment, imparting & resisting large forces, and isolating sections of its body. Finally, these traits are highlighted in three demonstrations, proving the efficacy of this unique method as well as affirming the utility of permanently stiffening a soft robot. In the future, the work in this thesis can help open the way for permanent deployable robotic structures and soft robots in roles more traditionally used for rigid robots.</p>

Quadruped robots can traverse a multitude of terrains with greater ease when compared to wheeled robots. Traditional rigid quadruped robots possess severe limitations as they lack structural compliance. Most of the existing soft quadruped robots are tethered and are actuated using pneumatics, which is a low grade energy source and lacks viability for long endurance robots. The work in this thesis proposes the development of a continuum actuator driven quadruped robot which can provide compliance while being un-tethered and electro-mechanically driven. In this work, continuum actuators are developed using mostly 3D printed parts. Additionally, the closed loop control of continuum actuators for walking is developed. Linear Quadratic Regulator (LQR) and pole placement based methods for controller synthesis were evaluated and LQR was determined to be better when minimizing the actuator effort and deviation from set-point. These continuum actuators are composed together to form a quadruped. Gait analyses on the quadruped were conducted and legs of the quadruped were able to trace the gaits for walking and galloping. / Fyrfotarobotar kan lättare korsa en mängd olika terränger jämfört med hjulrobotar. Traditionella styva fyrfotarobotar har kraftiga begränsningar då de saknar strukturell följsamhet. De flesta befintliga mjuka fyrbenta robotar är kopplade till en eller flera kablar och drivs av pneumatik, vilket är en lågkvalitativ energikälla och lämpar sig inte för robotar med lång uthållighet. Arbetet i denna avhandling föreslår utvecklingen av en continuum ställdonsdriven fyrfotarobot, som ger följsamhet samtidigt som den ¨ar frånkopplad och elektromekaniskt driven. I detta arbete framställs continuum ställdon med mestadels 3D-printade delar. Dessutom utvecklas dessa ställdons slutna kontrolloop för gång. Linjärkvadratisk regulator (LQR) och metoder baserade på polplacering utvärderades för styrsyntes, och det fastställdes att LQR presterade bättre när man minimerar ställdonets ansträngning samt avvikelse från referensvärde. Continuum ställdon sammansattes för att bilda en fyrbent robot. Gånganalyser utfördes på roboten och dess ben kunde följa gång- och galopprörelser.

Animals exploit soft structures to move smoothly and effectively in complex natural environments. These capabilities have inspired robotic engineers to incorporate soft actuating technologies into their designs. Developing soft muscle-like actuation technology is one of the grand challenges in the creation of soft-body robots that can move, deform their body, and modulate body stiffness. This paper presents the development of smart pneumatic McKibben muscles woven and reinforced by using conductive insulated wires to equip the muscles with an inherent sensing capability, in which the deformation of the muscles can be effectively measured by calculating the change of wire inductance. Sensing performance of a variety of weaving angles is investigated. The ideal McKibben muscle models are used for analysing muscle performance and sensing accuracy. The experimental results show that the contraction of the muscles is proportional to the measured change of inductance. This relationship is applied to a PID control system to control the contraction of smart muscles in simulation, and good control performance is achieved. The creation of smart muscles with an inherent sensing capability and a good controllability is promising for operation of future soft robots.