Sub-Pages

Design Concepts and Constraints

        At the outset of the project group 6 considered and explored many possible ideas for an overall design and for the individual design components. Before the team could begin with concept generation some initial design constraints had to be established. These constraints would be based on the sponsor’s wishes and on the physical practicalities involved in designing a robotic system to work in such an inhospitable environment as would be present in the cave system. While the following items might not normally be considered design constraint they were developed in conjunction with the sponsor and were. They therefore placed bounds on the design space that the team later explored.

The first factors considered by the team were whether to make the robot self-propelled, to make it tethered, to make several relatively inexpensive designs or a single expensive design, whether to maintain continuous communication with the robot or to download all the data at the end of the mission, and where and how to retrieve it after the completion of a mission. After an initial meeting with the sponsor some of the initial design considerations discussed above were resolved.

It was decided that the robot would drift with the water currents, that it would be untethered, that it would be designed to be  relatively inexpensive, that all the data would be retrieve at the end of the mission, and that the robot would be retrieved after it had exited the underwater cave system. By allowing the robot to drift with the water currents in the caves, the robot would be able to provide an estimate of the water velocity by recording its own speed. More significantly, by not requiring the robot to propel itself through the water its power and computational requirements are greatly reduced. It was also decided that since the robot would be drifting with the current and since it would be traveling for several miles in underwater caves full of places to snag or rip a cable that the robot be untethered. The decision to pursue an inexpensive design that could be easily duplicated so that multiple units could be used in a single mission was based on several factors: that using several units simultaneously would allow for a more thorough exploration of the cave system, if a single unit were lost or damaged it would constitute a major loss of data or material, and that since the loss of a small percentage of units would be acceptable a simpler control and navigation system could be used, thereby further decreasing the cost. Lastly, it was also decided that the robot would store all of its data onboard to be downloaded at the end of a mission after it was retrieved from a location downstream of the point where it exited the underwater cave system.

The design space created by the above constraints are explored further in the Initial Concepts section.