A low-power, jamming, magnetorheological valve using electropermanent magnets suitable for distributed control in soft robots

Abstract

Abstract Magnetorheological (MR) valves are an attractive way to make reliable valves with no moving parts. MR fluid valves operate by powering an electromagnet positioned near a constriction through which MR fluid is flowing. However, these valves are high-power devices, consuming on the order of watts of power while closed, and the electromagnets and flow paths are relatively bulky. Due to their power draw and size, they are unsuitable for many miniaturized and portable applications which would otherwise benefit from a solid state valve. In this paper, we introduce a low power, jamming MR valve that makes use of an electropermanent magnet, which can provide either a strong magnetic field or no field, with no continuous power draw and no moving parts. The resulting valve has overall dimensions of 4× 4×6mm, a mass of 0.476g, material costs of $7.32 per valve USD at quantity 100, holds over 415 kPa of pressure, and leaks only 0.02g of fluid over a 24h period when held at 105 kPa. These valves are well suited for use in soft robots, e.g. robots composed of stretchable elastomers and may allow for increased degrees of freedom in soft robotic designs. We discuss the design considerations for making MR valves, study the effect of different fluids and valve sizes, develop a numerical framework for simulation and further valve design, and demonstrate the use of a MR valve to control the actuation of a soft robotic appendage.