Numerical study of polymer embedded metal hydride-based self-sensing actuator

Abstract

Metal hydride actuators have amassed increasing attention over the past decade owing to their desirable operational characteristics, such as a high power-to-weight ratio, noiseless and vibration-less operation, lightweight, safety and environmental friendliness. Essentially, there are two ways in which we can attain actuation using hydrides. Primarily, actuation force is generated by the hydrogen gas pressure changes associated with charge–discharge process. Alternatively, the incompressible volumetric changes in the hydride bed during sorption can also result in actuation. However the studies reported on this type of actuators are rare and mostly deal with bimorph actuators. The present study investigates the effect of soft silicone rubber composited metal hydride bed within a hollow stainless steel spring for its potential use as a self-sensing actuator element. LaNi5 is used as the metal hydride alloy. For an equivalent quantity of hydride by mass, the estimated actuation stroke and force for the composite bed actuator are better than their powder bed counterpart (12 mm and 100 N, respectively, in contrast to 5.84 mm and 60 N), due to improved heat transfer. Bed thickness, coil pitch and coil diameter are important geometric parameters which control the performance of the device. As previously reported, hydrogen supply pressure and heat transfer coefficient are found to be important operating parameters controlling the force –stroke characteristics of the actuating element. The simulation study has been executed using COMSOL Multiphysics™ commercial code.