Design and Control of a Miniature Structure-Climbing Robot

The present study investigates the challenges associated with the inspection of bogie, a highly complex system comprised of numerous tightly-integrated components, which pose particular difficulties due to their compact arrangement. In response to this challenge, the study proposes the use of miniature crawling robots, designed to access and inspect hard-to-reach areas with greater ease and accuracy. The success of this approach is expected to greatly alleviate the challenge of inspecting bogies, while also holding potential applications within manufacturing processes and steel structural environments. The proposed robot, referred to as BogieBot, is a miniature multi-modal and kinematically redundant climbing mechanism, specifically designed to meet the unique industrial requirements of crawling into deeper parts of the bogies, traversing from one area of the train assembly to another, adhering to vertical and inverted surfaces without falling due to gravity, and carrying payloads (such as cameras) to facilitate inspection. BogieBot, despite its small size, faces limitations in its ability to navigate holes smaller than 8 cm or adequately cover large areas due to its limited speed. BogieBot's structure consists of six couple joints, four main links, an inner body link (to carry cameras or tools), and two mechanically switchable magnetic grippers, which enable it to effectively navigate through cluttered environments and manoeuvre around tight spaces. The unique design features of BogieBot, including the utilisation of six couple joints, provide it with superior flexibility, compactness, and adaptability, enabling it to navigate challenging environments with greater ease and efficiency. The BogieBot prototype has been fabricated; nevertheless, the time limitations of the study curtailed the extent of laboratory assessments on its advanced movements. To demonstrate BogieBot's viability and effectiveness, comprehensive analyses were conducted, including forward kinematics, inverse kinematics, and dynamics. These analyses revealed the advantages of utilising redundant degrees of freedom for enhanced performance and obstacle-free movement in complex environments. Workspace analyses assessed the robot's performance during surface transitions and encounters with obstacles. Conventional control schemes were found inadequate for guaranteeing collision-free motion. Hence, an intelligent control strategy was devised to improve performance and enable collision-free motion in cluttered environments. An intelligent hybrid position and force control mechanism was developed to ensure safe interaction between BogieBot's free end and its environment. This study provides valuable insights into the development of miniature crawling robots for inspection in ferrous metal environments.