The purpose of this research is to present an alternative multibody dynamic model for soft robots and to analyze the intrinsic mechanism of motion. It is difficult to directly apply traditional robot modeling methods due to the large structural deformation of soft walking robots. This paper establishes the dynamic modeling of a soft robot system with contact/impact based on the corotational formulation of the special Euclidean group $SE$ (2). The experiments are designed to verify the dynamic model of the robot. The history of the marked points on the robot prototype is measured in real time by an ARAMIS Adjustable Camera System. Based on the dynamic model, we conducted an in-depth analysis of the entire process through which the robot achieves directional walking utilizing complex friction characteristics. Notably, the robot’s kick-up phenomenon attracted our attention, and an analytical model for predicting the critical drive acceleration is proposed. The conditions and mechanisms of the robot’s kick-up are analyzed, and effective direction is provided for designing new drive laws. Finally, several sets of key parameters affecting the walking efficiency are analyzed using the multibody model, which can provide scientific guidance for the material selection and optimization of the robot. The presented dynamic modeling approach can be freely extended to other soft robots, which will provide valuable references for the design and analysis of soft robots.
