Proposed Designs
DESIGN #1 | DESIGN #2
(click to enlarge images)
The two designs Team L tested were essentially the same with the only difference being the propeller size. The team chose to keep the main design the same because using the t-shaped plated has allowed for an increased and consistent stability through testing from the original basic design. A difference in propeller size was chosen after various test runs, inconsistencies using the smaller propellers, and remembering previous knowledge gained last semester in the wind turbine lab. It was found that as propeller size increased, so did wind speed. The team hoped the increased propeller size from their prior knowledge would help solve the inconsistencies in the test runs and have a better energy efficiency due to the fact that the motors will not have to run as hard to complete the same task.
When first completing trials from the performance test, Team L noticed that the AEV was very inconsistent and often never stopped or responded to any of the commands the code outlined. The trouble with the reflective sensors was suspected, so a reflective sensor test was done to fully and correctly troubleshoot the problem. Because the test showed the serial monitor still taking in data the team knew it was not a communication problem and knew that the wires connecting the sensors to the Arduino were not the problem. It was concluded that the reflective sensors needed to be replaced, as well as the AEV, needed to be modified to help solve the problem of inconsistencies between trial runs. After the reflective sensors were replaced and the AEV was modified by replacing the 20”-20” propellers with 30”-30” propellers, the AEV started behaving according to the code written.
Arduino Code
Preliminary Arduino Code:
// Set all motors to 30% power motorSpeed(4, 30); // Continue until the reflectance sensors have read 123 marks goToRelativePosition(123); // Reverse the direction of all motors reverse(4); // Set all motors to 38% power motorSpeed(4, 38); // Continue until the reflectance sensors have read 30 marks goToRelativePosition(30); // Stop all motors brake(4); // Keep motors at current speed (0) for 7 seconds goFor(7); // Set all motors to 30% power motorSpeed(4, 30); // Continue until the reflectance sensors have read 30 mark goToRealtivePosition(30); // Stop all motors brake(4);
Click to view final Arduino code: FinalCodeTeamL
Research Supporting AEV Decision
Team L made two similar designs for the test based on the concept screening and scoring done in Preliminary Evolution of Design. Finally, they used the design with a larger size of blade and the motor mounts moved out one space to complete the performance test 1. After testing the AEV several times with two different designs, team L got to know that in order to make the AEV stop precisely at the right position, the most important thing is to make the vehicle stop gently. By comparing the two different designs for the AEV, team L finally realized the huge difference caused by the different sized propeller blades. For a gentler stop, large size blade has a comparative advantage of using lower power for braking and made the AEV more consistent under the same control program and stop at precisely the right position.
During the whole process of the experiment, team L had two basic designs to complete the test. For the first design part, team L found it difficult with keeping the consistency of AEV under the same control program command. Firstly, team L tried to change the sensor and the wire connected to it in case of sensors lacking sensitivity or something wrong with the wire. After changing, team L noticed the AEV could just make it precisely at the right positions from time to time. Under the guidance of a professor, they noticed the small size blade needed higher motor speed to reach the gate. Thus they switched to another 30”-30” blade and only need half the power to make it, which made the braking more gentle. Team L continued operating the AEV during the whole lab to find the most suitable position to do according to the command to make the time and distance more accurate.
Jiayu recommends that for better performance, AEV with a larger size blade would make the whole operation more stable because larger size propeller could move the same distance with less power which makes the AEV stop precisely between the sensors with a gentle brake. Based on the issues team L encountered during their process, Emily believes that all equipment should be thoroughly tested before jumping to other sources of error. Similarly, Alyssa believes that in the future various types of propeller blades should be thoroughly tested before settling on a specific type and size. Kamila recommends that the future AEV’s preventing coasting to a stop, as our experiences have shown that doing such results in less consistency.
To conserve power, Team L programmed the AEV to coast during specific sections of the performance test. Places coasting are used include going downhill at any point, and briefly before breaking to decrease the braking power required to stop the AEV. To increase consistency from a programming standpoint, Team L implemented an algorithm to calculate the speed of the AEV immediately before braking to determine the amount of break power necessary. A labelled graph of the power output of the AEV over time is shown below.
During the final performance test, Team L’s AEV design performed its task in 54.06 seconds, using 143.3 Joules. The total cost of the proposed AEV design, based on accuracy efficiency and capital cost, is $529,335.
