A Position Estimation Method for Pneumatic Actuators Based on Flow and Pressure Sensors

Pneumatic actuators are lightweight, compact, and capable of generating compliant motions due to the compressibility of air. Despite their advantages, measurement and control challenges significantly limit their industrial applications. Typically, a simple open-loop position control method is applied to pneumatic cylinders, controlling the piston’s predetermined moving distances without sensor feedback. External position sensors, which are conventionally used for feedback control, increase system complexity and reduce adaptability, particularly in underwater environments. In this study, we propose a new method to estimate the position of pneumatic cylinders using a flow and a pressure sensor that can be positioned away from the cylinder. This results in a compact, lightweight design and prevents disconnections and contacts between the piston and external sensors. In addition, the system could be used underwater without concerns about waterproofing external sensors. We evaluate the basic performances of the proposed method by estimating pneumatic cylinder positions with a simple experimental system. The experimental results demonstrated that our method could estimate piston positions with an error of approximately 1 mm.