Design of fluidic components towards electronic-free control of soft robots

Soft Robotics is an emerging field that make use of compliant materials to develop versatile robotic systems. Within the context of soft robotics, fluidic soft robots use medium such as air or water for actuation. Such an actuation method allows for e.g. inflation and deflation of cavities within the compliant body of the robots and and enables high adaptability and deformability, useful e.g. to achieve tasks such as gripping and locomotion. As a result, the embodied deformability of the hardware makes soft robots ideal for navigating in harsh, unknown environments or completing delicate gripping tasks. Efforts in literature have focused on achieving complex behavior as well as embedding autonomy and intelligence in the robot. However, as for the control of soft robots, still electronic controllers are mostly used, therefore introducing mechanical-electronic interfaces and limiting the advantages of soft robots. A recent trend in soft robotics research focuses on bringing sensing and control under the same medium of the actuation, using fluids not only to transmit power but also to carry information, making use of fluidic circuits rather than standard electronic ones. This thesis takes a step into the research on what is accomplishable in terms of electronic-free fluidic control for soft robots. Our approach draws inspiration from the hydraulic analogy between the pressure and flow in fluidic circuits and the voltage and current in electronic circuits. While this analogy is useful for visualizing and understanding the behavior of fluidic circuits, yet it presents some limitations that we also discuss in this work. The focus of this thesis is to develop fluidic control components which behave similarly to their electronic counterparts, and to lay the foundation for control strategies by implementing them in fluidic circuits. Starting from simple basic components such a transistor, and using them as building blocks, we develop increasingly complex fluidic circuits for soft robots and eventually prove the potential of our approach by demonstrating the control of a bending actuator equipped with a haptic feedback sensor. With these results, we pave the way for bridging the gap between power and information flow in soft robots and for the design of complex control system through fluidic circuits.