Super-Twisting Sliding Mode Control for Crack Sealing Manipulator

In this work, the branch of the tree robot is controlled for crack sealing of concrete pipe. This tree robot is utilised for repair and maintenance purposes. It can maneuvers inside vertical pipes, horizontal pipes and surfaces. A CAD model of the pipe has been modelled in Solidworks, and a mimic of the existing crack is simulated inside the pipes. From the observation and simulation study in Solidworks, it can easily be observed that only the upper branch (i.e., the fifth branch) performs the repair task. Furthermore, the crack repair has been assured for the branch of the tree robot. However, due to the presence of uncertainty and disturbances, the end-effector of the tree robot doesn't follow the desired crack trajectory. Sliding mode control (SMC) is a well-known method to address such types of problems. While conventional SMC addressed a part of the issue, Non-singular fast terminal sliding mode control (NFTSMC) is investigated for precise tracking. However, these methods suffer from chattering issues and chattering inside a concave surface (inside a pipe) is not preferable. To reduce chattering, Super-twisting sliding mode control has been proposed in this work. After performing the simulation and numerous iterations, it has been found that the STSMC produce less chattering than NFTSMC. Furthermore, the work exploits the Lyapunov candidate function to ensure asymptotic stability.