Kinematics and statics of eccentric soft bending actuators with external payloads

Abstract Soft bending actuators, born with the considerable capacity of structural flexibility and environmental adaptability, have been widely favored for years. However, the highly nonlinear coupling between force and deformation in such robots are very complex, especially considering the external payloads. This paper puts forward a concept of eccentric soft bending actuators (ESBAs) that can exhibit different output characteristics by modifying the geometric parameters. A virtual trajectory based kinematic model is introduced to describe the deformation of ESBAs so that the screw theory based product of exponentials (POE) formula is applied to the analysis of such soft tentacle-like structures for the first time. Following this, the static model takes the input pressure, external payloads, and material parameters into account by utilizing the principle of minimum potential energy, making a generalized mathematical expression. The proposed model is then verified via finite element methods (FEM), and finally through experiments. An application example shows that the Particle Swarm Optimization (PSO) is introduced to find appropriate geometric parameters to make an ESBA have maximum stiffness.