Design and Control of CRAM : A Highly Articulated Cable-driven Remote Access Manipulator for Confined Space Inspection

The use of robotics for inspection operations in hazardous environments such as confined spaces has seen significant recent advancement. Removing the need for human entry to such spaces is desirable due to safety and time benefits, with associated cost reduction. Challenges arise when navigating a robotic manipulator in a constrained environment, leading to a need for highly articulated motion and a large number of Degrees of Freedom (DoF). Tendon/cable-driven manipulator systems are used to realise large length-to-diameter ratios by removing the need for lifting the weight of actuators. This paper presents the design of a Cable-driven Remote Access Manipulator (CRAM), which requires only one actuator per DoF and achieves bending angles of ±90◦. CRAM’s feeding motion is provided by a linear sliding rail and it has a changeable end effector to be used for a variety of inspection operations. The mechanical design, system architecture and a kinematic control scheme are detailed. A working prototype is presented, with experiments validating the design concept.