A method for determining parameters of hyperelastic materials and its application in simulation of pneumatic soft actuator

This paper presents a method for determining material constants of hyperelastic material used for building the soft robotic actuators. Sixty testpieces were made of silicone rubber with a shore A hardness from 20 A to 45 A. Each of them was then subjected to the uniaxial tensile test to obtain the stress–strain relationship, which is a key factor to evaluate the compatibility of the common six forms of strain energy density function for hyperelastic material. The sum of square error was used to determine the most relevant constitutive models, which are Ogden third order, Polynomial second order, and Yeoh, as well as parameter values of the corresponding materials. To analyze the appropriateness of these models for computation, six pneumatic soft actuators were built from materials with different hardness and tested for various pressures. From the simulation and experimental results, the model Yeoh has yielded the highest accuracy. This outcome forms a firm basis for the determination of suitable material in the computation and simulation of the pneumatic soft actuator. Besides, the obtained experimental results in this paper could be included in the database of hyperelastic material with different hardness for further simulation in the related field.