Untethered Fluidic Engine for High-Force Soft Wearable Robots

Fluid-driven artificial muscles exhibit a behavior similar to biological muscles which makes them attractive as soft actuators for wearable assistive robots. However, state-of-the-art fluidic systems typically face challenges to meet the multifaceted needs of soft wearable robots. First, soft robots are usually constrained to tethered pressure sources or bulky configurations based on flow control valves for delivery and control of high assistive forces. Second, although some soft robots exhibit untethered operation, they are significantly limited to low force capabilities. Herein, an electrohydraulic actuation system that enables both untethered and high-force soft wearable robots is presented. This solution is achieved through a twofold design approach. First, a simplified direct-drive actuation paradigm composed of motor, gear-pump, and hydraulic artificial muscle (HAM) is proposed, which allows for a compact and lightweight (1.6 kg) valveless design. Second, a fluidic engine composed of a high-torque motor with a custom-designed gear pump is created, which is capable of generating high pressure (up to 0.75 MPa) to drive the HAM in delivering high forces (580 N). Experimental results show that the developed fluidic engine significantly outperforms state-of-the-art systems in mechanical efficiency and suggest opportunities for effective deployment in soft wearable robots for human assistance.