Hybrid Membrane–Solenoid Valves for High-Flow, Precisely Controlled Soft Robotic Actuation

Abstract

Fluid-driven soft robots promise high-dimensional motion and cost-effective scalability, but their performance is constrained by the limited flow capacity of compact solenoid valves and the integration challenges of large membrane valves. This paper introduces a modular hybrid valve architecture that couples a high-flow membrane valve with an integrated miniature solenoid pilot. The resulting composite element achieves both high mass flow rates and precise electronic control while maintaining a compact, lightweight, and fabrication-friendly design. We present the design, modeling, and control strategies for these valves, and evaluate their performance through three experiments: tank pressure regulation, actuation of a weight-curling robot, and integration into a planar two-stage tossing robot. Across all cases, the hybrid membrane valves significantly outperformed solenoid valves, exhibiting faster pressurization and venting, higher bandwidth, and over a five-fold increase in mechanical power output. These results demonstrate that membrane-solenoid hybrid valves provide a scalable and integrable solution for overcoming the “piping-problem,” enabling hyper-actuated soft robotic systems.