The purpose of Lab 7 was to test AEV designs in order to show how it behaves when set at a constant motor speed, as well as when the motor speed is set to zero and the AEV is coasting to a stop. When the AEV is running in constant motion, both frictional and propeller forces are acting on the AEV. When the motor speed is cut, only a frictional force acts on the AEV. Using the time and distance from the AEV travel, the group was able to calculate the different forces on the AEV. Calculating these forces allowed the team to compare their numbers to the rest of the class and it also showed where possible improvements to efficiency could be made. The class average of the force of the propellor was 11.2 gm. In comparison to the team’s value (8.5 gm), the team’s model was less than average. This may be due to hardware issues or the fact that the team’s motor percent speed was set to 25% as opposed to the majority of the class who had it set to 30%. The class average of the frictional force was 4.7 gm with the team measuring at 2.6 gm. Being lower than the average suggests that the AEV model is lighter than the majority of the class which is expected because materials for aerodynamics must be added still. It is noted that only one team had a smaller frictional force value (2.5 gm). The net force of the team was calculated to be 6.0 gm which is close to the average of 6.5 gm. To achieve a greater force, the team will work to make the AEV lighter while also improving aerodynamics.
In Figure 1, the speed vs. time graph is shown and it shows the AEV accelerating from about 0-4 seconds where it reaches a max speed of 0.9 m/s. It then slows to a stop at about 13 seconds.
The second graph, Figure 2, shows distance vs. time and this graph is just an integral of the first graph. The AEV comes to a stop about 5.5 m down the track.
Another goal of Lab 7 was to test the wheel sensors to make sure they were properly functioning with minimal error. The goal of this task was to use the data stored in the AEV from each test and how far the AEV travelled in meters to determine the difference between how many marks the AEV said it travelled and how many marks should’ve been travelled based on the distance, attempting to get within a range of a 2 mark error or less. The class average of the marks error was 3.7 while the team measured a margin of 5. This is likely due to hardware issues encountered.