Rationale

            As the mechanical engineer for my team’s ROV project, I am tasked with constructing a manipulator used to pick up, carry, and relocate items within a swimming pool, while not impeding the motion of the ROV. For this task I have created three alternate solutions. My alternate solutions include the horizontal claw system, the modified horizontal claw system, and the vertical claw system. The manipulators need to be able to perform a wide range of tasks, including manipulating seals and locks, collecting samples, and relocating items from the pool to the surface. Each solution is viable and can complete the tasks assigned.

            My 1^st alternate solution is a horizontal claw system. It has one pincer like claw coming off of either side of the arm. The arm is straight and rectangular in shape in order to fit into Sean’s hull design. It utilizes a tooth arm and gears in order to function. There is one 1” gear and one pincer has a 1/8” gear, while the other has a ½” and ¼”. The arm will be 6 inches long. Each claw will be 2 inches long. The claw will be composed of plastic and will use a pneumatic power system to power it. There are many pros and cons to the horizontal design. The system will be powered using pneumatics, which while not as accurate as an electric motor; it is a very reliable power source. It is also a simple power source that is unlikely to fail or impede the ROV in any way. Although, the air pressure from the pneumatic power system may disrupt the buoyancy of the ROV slightly. Similar to the vertical design, this design allows the claw to be able to very easily grab items in the pool, but not necessarily be able to hold on to the item that well during transit.

            My 2^nd alternate solution is a modified version of the horizontal claw system. It has a pincer-like claw on each side of the arm, but it has a top and bottom set in order to create a cage as well. There will be bars running from top to bottom in order to enclose the cage. This will allow the ROV to grab and hold on to objects more easily. Once again the arm is straight and rectangular in shape to accommodate Sean’s hull design. It utilizes a tooth arm and gears to function. There is one 1” gear and one pincer has a 1/2” gear, while the other has a ½” and 1/2”. The arm will be 6 inches long. Each claw will be 2 inches long and the bars that form the cage will be 2 inches tall. The claw will be composed of PVC piping and will be powered using pneumatic power. There are many pros and cons to this design. This design is similar to the horizontal claw system in principle, but it expands that design with the two level addition and the cage. This is the major benefit of this particular design. It can grab items in the pool just as well as the other two designs and the cage allows it to better contain the objects once they are picked up. This makes relocation of items within the pool much easier and safer. The system will be powered using an electric motor, which will enable us to accurately manipulate the claw. One motor will be to open and close the claw and one motor will be to rotate the claw so that it can take on additional tasks. Although, the air pressure from the pneumatic power system may disrupt the buoyancy of the ROV slightly.

            My 3^rd alternate solution is a vertical claw system. It is similar to the horizontal system, although it is in a different position and has different gear ratios. It has a claw coming off the top and bottom of the claw arm. Once again the arm is straight and rectangular in shape to accommodate Sean’s hull design. The claw will come together to encase the object on the top and the bottom. The gear ratio will not be equal and will allow the bottom claw to move faster than the top claw. This is so that the bottom can scoop up the object quickly and then have the slower top claw come down and close on top of it. The arm will be 6 inches long. The claws will be 2 inches long each. The claw and arm will be composed of PVC and will use an electric motor to power it. There are both pros and cons to this design. The vertical design with its unique gear ratio, where the bottom comes up faster to meet the top, allows it to scoop up items easily. This would allow the ROV to be able to grab certain items that could be in difficult positions. Also, has pincer like claws which are excellent for grabbing items. Although, I am worried that this claw design is not optimal for holding on to the items while in transit around the competition area. The claw is powered with an electric motor, which may be more accurate, but is also prone to becoming water logged and shorting out. It is also more complicated and more likely to malfunction than the pneumatic power system.

            In conclusion, as my final solution I have chosen solution two, or the modified horizontal system. It is the two level horizontal claw with the cage. It is powered using two electric motors, one to open and close and one to rotate the angle of the claw. This design most effectively meets the requirements of the design. It most easily can pick up and secure items for transport around the pool. It also has the easiest to use and most reliable power source. Overall, the horizontal claw design is the most efficient design to complete all of the competition tasks, and the design matrix further backs this statement up.