Design of cable-driven modules for hyper-redundant manipulators

The interior of the wing compartments of the aircraft are highly confined, thus making it impossible for any conventional robotic arm to perform inspection directly. The traditional method used is to disassemble the components to perform the inspection and then re-assembling back. This is extremely time-consuming and aircraft companies are constantly on a lookout to reduce time taken for maintenance and repairs. A hyper-redundant manipulator, capable of manoeuvring in highly confined space, offers potential to address this concern. In this project, the objectives are to design and evaluate cable-driven modules suitable for the development of a hyper-redundant manipulator. A review and patent search is conducted to identify and compare the mechanisms used in the design of hyper-redundant systems. This is followed by the testing of a commercially available pneumatic muscle. The repeatability of the pneumatic muscle tested is found to be good but the hysteresis property is poor, thus making it unsuitable for further development. Three prototypes with different backbones (spring steel, hydraulic tube, extension spring) were also tested. It is found that the hydraulic tube has the best performance in terms of flexibility and motion stability. Significant permanent deformation is observed in the spring steel backbone after going through a series of bending. For the extension spring, while the prototype is able to move smoothly under the control, it is noted that the point of bending is changing with the different angles of bending. From the tests, it can be concluded that the proposed cable-driven modules with a flexible backbone structure are able to achieve the flexibility needed for the hyper-redundant manipulator. Further improvement and work are included in the report.