Locomotion modeling of a triangular closed-chain soft rolling robot

This paper presents a novel triangular closed-chain soft rolling robot. The proposed robot uses the least number of soft actuators (i.e. three) among current closed-chain soft rolling robots and can achieve faster rolling locomotion. To verify its feasibility in theory, we build a state-space model for simulating its rolling locomotion based on the continuum deformation and the rolling dynamics. Different from previous pseudo-rigid and finite element models, this model is fully analytical and continuous. To validate this model, we conduct experiments of rolling locomotion with a prototype constructed by three Curl Pneumatic Artificial Muscles (CPAMs). The results show that the proposed robot can roll forward with an average velocity of 20-21 mm/s on level ground and 12-13 mm/s on 8 degrees inclined ground. The error of the mass center trajectories and average velocities between the simulation and experiment is within 10%. The proposed soft robot can be expanded into parallel or tetrahedron morphology to enable the steering movement, and it has potential applications in the space exploration and medical operation.