Fluidic Control of Untethered Underwater Soft Robots

Abstract

Soft robots offer considerable advantages relative to traditional, rigid robots, including: versatility, safety, and rich dynamic behavior. A common approach for actuating soft robots is to use pumps and valves to control pressures and flow rates through fluidic channels embedded in a soft material, to cause desired deformations. Usually, an electronic control board carries the pumps, valves, and other components to control this fluid flow. Currently, many existing hydraulic control systems are designed with application-specific performance requirements, forcing researchers to either invest substantial time and effort into developing custom hardware or constrain their soft robotic systems to the limitations of available control platforms. To address these issues, we present an approach to controlling soft robots underwater that can be achieved with a compact, hydraulic control system. We demonstrate this approach with hardware design housed in a 3D-printable enclosure that is water-resistant up to 1 m for 30 min. The system features three independently controlled pumps, each capable of reversible actuation, with a combined maximum pressure of 0.9 MPa and a maximum f low rate of 3.6 L/min. Additionally, we present an approach to f low sensing using onboard RPM sensors, which avoids adding impedance to the fluid channels and, when combined with our direct pump drive approach, enables precise and simultaneous control of multiple soft actuators. This system offers an accessible platform to accelerate the development of future underwater soft robots.