Pneumatic Actuator with Gas–Liquid Phase Change Working Fluid. Mathematical Modeling and Experimental Research

Traditional sources of pneumatic energy are not suitable for “soft” robotics devices aimed at mobile or wearable applications. One of the possible solutions to this problem is the organic low-boiling liquids as the working fluid for the pneumatic actuators. The ideal gas model to describe the properties of the gas phase, which is used in most works in this area, may lead to significant errors. This paper discusses the mathematical modeling of one-way bellows actuator with n-butane working fluid, using equation of state for real gas (Redlich – Kwong equation) and the Lee – Kesler relations to determine the pressure of the saturated gas phase. An experimental verification of the obtained solutions was carried out on the actuator model, where the working fluid is heated by a nichrome heater and cooled by a Peltier thermal module. Satisfactory agreement between the calculated and experimental data was obtained.