Final Testing of the Rov Arm

My Rov arm, which was mounted upon Team Decepticons Rov, competed in the 2008 New England Regional MATES competition. The arm was required to grab simulated rock crabs, where it could attain a maximum of five for 20 points each. Each rock crab was made from a 1 and ½” ABS. Attached to this were eight pipe cleaners for legs, and two bent pipe cleaners for antennas. For every crab lifted off the pool bottom ten points were awarded by the competition. For every crab brought to the surface an additional 10 points were awarded. The arm was also required to be maneuvered into a simulated hydrothermal vent where the temperature gauge mounted to its side could obtain a reading. A maximum of 100 points were awarded if the temperature readout is within 2 degrees Celsius. Lesser amounts were given for lower accuracy. The vent was a ½” PVC pipe mounted vertically at the bottom of the pool.
Initial testing was done in the small pool in the systems lab, as well as out of water. A shortened tether was attached to the arm and all functions of the arm were tested. At this point everything worked as planned. The arm was able to pick up five pounds of weight and hold it with no issues.
After the Rov was completely assembled the final tether was filled and attached to the arm. The arm was then submerged in the pool. With the new tether attached the arm opened and closed much slower, but with the same force. The arm was able to grip a rock underwater and hold onto it as it was pulled out of the pool. The arm was also able to grab onto small waffle balls with weights inside that were close in size to the rock crabs. Further testing was done after minor modifications were made to the design. After boring out the syringe holes to a larger diameter the system operated at nearly twice the speed.
While obtaining the temperature, a readout of 54 degrees Celsius was shown. This was within 2 degrees Celsius of the actual temperature and 100 points were awarded to our team. The thermometer setup had a quick response time and showed the temperature within one second of being placed over the vent. When grabbing the rock crabs one crab was obtained and brought to the surface for 20 points. Five points were later deducted for pulling on the tether. Pulling on the tether had nothing to do with the arm and was necessary as the craft was not moving due to the propulsion system. On the second attempt to capture a rock crab the hydraulic control syringe at the top of the pool broke. Too much pressure was applied while lifting the first crab and the arm locked into place. When trying to reset the arm the rubber seal separated from the plastic plunger, breaking the vacuum seal of the system. This prevented our team from capturing another crab, although we only had two minutes left at this point.
Our team ended up placing 6th out of 14 teams. The total score can be seen on the attached sheet. Shown below in Figure 1 is our Rov completing a task during the competition.

Expectations

After construction of the robotic arm is completed it is expected that it will function correctly. It is important that the arm be able to clamp onto both a small item, and a larger heavy item. The arm must be tested in the pool to judge the arms performance while submerged. To test this multiple items will be placed on the bottom of the pool. These items will mimic those of the competition as much as possible. The entire rov will then be assembled and used. This not only tests to see that the robotic arm functions correctly but that the entire Rov functions as well. This is a time where many adjustments can be made. The robotic arm will also be expected to have at least two degrees of motion. This will allow the arm to be maneuvered into place. This will be tested first out of water to ensure that a reasonable range of motion is achieved, as well as in water to be sure that the arm functions the same and all components are waterproofed correctly. The arm must also be strong enough to hold at least ten pounds of weight, while the more the better. This however will not be tested until the point of destruction as it will not be possible to build an entirely new arm in time.

Testing Procedures

To test the robotic arm three separate tests must be performed. The first step involves testing the range of motion in a dry environment. This involves connecting the robotic arm to the Rov and setting up the control station. All ranges of motion will be tested to their extremes multiple times. Upon completion of this test a similar one will be performed in the water. The Rov will be submerged in the test tank and all components will be tested. The third test involves construction of items that resemble those of the competition. It is impossible to predict what exactly these items will be, but it can be assumed that the arm must be capable of moving a small and delicate item, as well as a larger heavy item. Through careful examination of the rules released in January the items will be designed and constructed. After the construction of these items they will be gently placed on the bottom of the test tank as not to cause damage. The entire Rov will then be placed in the water and a slow run will be performed to become accustomed to all controls of the Rov. Once all tasks are completed they will be re-set in the bottom of the pool. Now the Rov will be tested operating at its maximum speed. This will be timed and the data will be used to predict the Rov’s performance in the competition. The pool used in the competition can be seen in Figure 1 below.

Figure 1
MATES competition test tank (MATES).

1. Assemble Rov arm onto Rov.
2. Connect all control wires through tether to the control box.
3. Using the control box operate the robotic arm through all ranges of motion out of water.
4. Submerge Rov in test tank.
5. Using the control box operate the robotic arm through all ranges of motion in water.
6. Place previously constructed items resembling those of the competition on the bottom of the test tank.
7. Slowly complete all tasks to be sure they are possible using the current set up.
8. Reset items on the bottom of the test tank.
9. Complete all tasks as fast as possible while using a timer.