Experimental Study on Bending Stiffness of a Soft Pneumatic Filament-polymer Actuator

Due to the advantages of soft material actuators, the soft material actuators become the important elements in automatic robots in recent years. The bending stiffness in the driving direction is an important parameter for pneumatic soft actuator, which directly affects the mechanical properties, like bending angle and deformation ability. In this study, a composite filament rectangular soft actuator (FRSA) is designed. The bending stiffness in the driving direction is variable as the actuator parameters are changed and such FRSA actuator can be used to adjust bending stiffness. The influences on bending stiffness from the material parameters and charged compressed air are studied experimentally. Experiments are carried out at variable filament diameters, cover ratios, inner wall thicknesses and compressed air pressures. The experimental data show that the bending stiffness increases with the increment of filament cover ratio. However, when the cover ratio is larger than 85%, the bending stiffness tends to be stable. At the same cover ratio, the bending stiffness of FRSA increases firstly and then decreases with the increment of the filament diameter. The composite filament actuator with larger cover ratio is more sensitive to the compressed air pressure, and its bending stiffness increases rapidly with the increment of the air pressure. Particularly, the actuator with 100% cover ratio gets the bending stiffness of 26.4 N/m at 120 kPa, which is 21% higher than that without compressed air.