Abstract: Wall climbing robots can be used to undertake missions in many unstructured environments. However, current wall climbing robots have mobility difficulties such as in the turning or accelarating. One of the main reasons for the limitations is the poor flexibility of the spines. Soft robotic technology can actively enable structure deformation and stiffness varations, which provides a solution for the design of active flexible spines. This research utilizes pneumatic soft actuators to design a flexible spine with the abilities of actively bending and twisting by each joint. Using bending and torsion moment equilibriums, respectively, from air pressure to material deformations, the bending and twisting models for a single actuator with respect to different pressure are obtained. The theoretical models are verified by finite-element method simulations and experimental tests. In addition, the bending and twisiting motions of single joint and whole spine are analytically modeled. The results show that the bionic spine can perform desired deformations in accordance with the applied pressure on specified chambers. The variations of the stiffness are also numerically assessed. Finally, the effectiveness of the bionic flexible spine for actively producing sequenced motions as biological spine is experimentally validated. This work demonstrated that the peneumatic spine is potential to improve the spine flexibility of wall climbing robot.

Key words: Active spine , · Bionic design , · Soft robot , · Gecko locomotion , · Finite-element modeling