The development of an electric-powered subsea robotic crawler for dredging

Abstract

The current rising global demand for ocean based recoverable minerals and natural resources is inspiring research and growing interests in the field of ocean dredging. However, current hydraulic powered dredging crawlers are prone to causing ocean pollution as a result of hydraulic leakages, heavy vibrations and noise. These underwater crawlers also consume relatively high power because of their mass. Hence, in this thesis we have modelled, designed, and manufactured a scaled-down electric powered subsea robotic crawler for underwater mining/dredging applications. The prototype is designed to compete with a scaled-down version of a real-world hydraulic powered Remotely Operated Subsea Tractor MK3 (ROST). This research also highlights the possibilities of eliminating sea pollution caused by hydraulic leakages in hydraulic-powered subsea crawlers by replacing them with electric powered ones. Furthermore, this research shows that electric powered crawlers will be lighter than hydraulic powered equivalents; hence, they will consume less energy during operation. A detailed literature review based on related research was first carried out to identify and outline the key characteristics of subsea crawlers/tractors, such as their operating principles, mechanisms, and structural design parameters. Afterward, the scaled-down prototype was modelled and assembled to meet the scaled-down basic specifications of the ROST MK3. The model comprises of a robot-driving base, a 2DOF robotic arm with nozzles at the end effector, and 2 pumps for loosening and dredging the seafloor respectively. Two DC motors connected to tank-tread chain links were used to propel the driving base as a differential drive robot. The control system was implemented using LabVIEW programming language to create a Graphical User Interface for various controls. To choose the right material for designing this model, a FEA simulation will be performed on different material. Additionally, the capacity of the forces operating on the model's structural elements will be ascertained through this simulation. The prototype is electrically powered by a 12V Nickel Metal Hydride battery with a 3000mah capacity. The NI-myRIO is used as the main microprocessor to control and interact with the necessary DC motors, servo motors, cameras, pumps, lights, and sensors. The prototype underwent land testing at the Adaptronics Advanced Manufacturing Technology Laboratory (AMTL). The drive characteristics (torque, velocity, and efficiency) of the model were tested at different angles of inclined planes which includes: 00, 150, 200 250 and 300. This research will further contribute to an alternative method of extraction using an electric powered robotic subsea crawler for ocean dredging and other applications. The crawler will be assembled and programmed to improve the quality and capabilities of its mode of operation under different ocean floor conditions, and finally, it will create a solution to the limitations of current hydraulic dredging crawler technology and a new approach to the utilization of robotic subsea crawlers for different applications.