Series Elastic Actuated Needle Valve and Sealing Equilibrium Flow Rate Models for Precise Position Control in Single-Acting Water-Hydraulic Actuators

Water hydraulics offer low viscosity, high-pressure capability, and environmental compatibility, making them ideal for teleoperated systems in extreme environments. However, achieving stable low-flow control and reliable sealing remains a key challenge owing to the complexity of current valve designs, and their limited precision at low-flow rates. To address this issue, we developed a compact needle valve—called Series Elastic Actuated Needle Valve (SEANV)—which incorporates a series elastic element, along with a sealing equilibrium model to predict its sealing behavior. Preliminary experiments using a single-acting actuator confirmed improved position tracking; however, these did not quantitatively characterize the flow control performance. Therefore, we conducted a detailed experimental evaluation of the flow and sealing characteristics of SEANV under various single-acting actuator conditions. The results demonstrate the enhanced low-flow resolution, achieving an RMSE of 0.516 × 103 mm3/s, and robust sealing perfor- mance, with leakage maintained within ±50 mm3/s, thereby validating the applicability of the proposed model to compact water-hydraulic systems.