Preliminary Design Report
(Note: Graphs appear small but can be increased in size when clicked on)
Results and Discussion
The first prototype design created and tested was Wesley’s design. Its main feature is that it has a vertical oriented base. The vertical orientation is important because it minimizes air resistance therefore increasing the energy efficiency of the AEV. The design is very simple otherwise to reduce the weight and the cost of extra parts. Wes’s designed the AEV with 30/30 propellers because contrary to the data that we collected, seen in Figure 1, they are the most efficient. We discovered this through testing both propellers. Using the 25/10 propellers suggested by the data in Figure 1, the AEV had to use a great deal of power to move at all, upon trying the 30/30 propellers the AEV used much less power and moved much quicker.
Figure 1: Propulsion Efficiency at different Advance Ratio
The second prototype design created and tested was Ron’s design. Ron’s design was the most different of the designs, therefore it was chosen as the second design in order to test how the different shape and whether the wings added or subtracted from energy efficiency as well as the cost. The orientation of Ron’s AEV was opposite to Wesley’s which allowed the group to analyze whether or not a horizontal orientation is more or less efficient than a horizontal orientation. The results can be seen in Figure 2. Ron’s designed used more power. It is designed after the X-wing in Star Wars. The design aimed to reduced air drag especially with the placement of the propellers under the top wings. Ron also took aspects of the sample AEV that were believed to increase efficiency and incorporated them into the his own design. Ron designed his AEV with 30/30 propellers for the same reasons as Wes.
Figure 2: Power Usage Over Time for Ron and Wes’s Designs
Melissa’s AEV design was similar to Wes’s in that it had a vertical base orientation. But it had extra parts to help reduce air drag further, it was modeled after a high speed train. However, it was decided that the cost and extra weight of the additional parts outweighed the benefits of less air resistance. Therefore this design was discarded in favor of Wes’s more basic design. Yumeng’s design was also very similar to Wes’s except that it had a horizontal base orientation and it had a different base shape that would require money to buy and it benefits are very minimal if there are any at all. Its horizontal orientation would create air resistance. Therefore Wes’s design was favored.
After analyzing the scoring and screening results of the designs in Table 1 and Table 2 below (also found in the appendix) as well as the testing results of power efficiency in Figure 1 the team decided on Wes’s design. The team had originally predicted that Wes’s design would be the most efficient because of its design and lack of extra parts. According to Figure 2, Wesley’s AEV spent 4.2 seconds to reach the gate with 32.7J energy consumed. Ron’s AEV spent 7.5 seconds to reach the gate with 40J energy consumed. Compared to Wesley’s AEV, Ron’s AEV spent more time completing the track as well as more energy. Team K will be using Wes’s design for the remainder of the project.
Table 1: Concept Scoring
Table 2: Concept Screening
Performance Test 1 proved that Wesley’s AEV had the least time and energy consumed than the three other other designs. Team K has been experimenting with two codes to figure out which is most versatile between different tracks. The first code increases absolute position and decreases reverse velocity of AEV during air brake. The second code keeps the absolute position constant and increases the reverse velocity of AEV during air brake. The two code solutions almost have the same energy efficiency but the second code is easier to adjust as it only affect the distance when creating an air brake. The two code solutions are both traveling at low speeds so no specific risk to the hardware. By doing Performance Test 2, Team K found the most flexible code solution for various tracks. The increase of the reverse air brake speed to 30 allows the AEV to stop beneath the sensor of the gate and have flexibility to move farther or nearer to the gate. This data is seen in Figure 3 and Table 3.
Potential errors that could have arisen that could have affected our testing is faulty parts, including loose wires or broken propellers, others including placing the AEV slightly off the starting point during each run, this inconsistency could affect the timing and distances in the code.
The figure below shows the plot of energy supplies of Wesley’s design. The plot was separated into three phases. The code in different phases are shown below.
Figure 3: Energy Supplies (W) during Trial Run
The table above shows the code for different phases.
Conclusion and Recommendations
Team K has chosen Wes’s design as the final design. Through testing the reference AEV and propellers in order to learn how the AEV functions along with research on aerodynamics, each member developed a design. Only through concept scoring and screening did the group actually get to compare their design to the reference AEV and evaluate its efficiency along with other important factor. Later, the group chose another design (Ron’s) with the potential of being energy efficient as well but through testing and more concept scoring and screening, the group found that Wes’s design was still optimal in the most important areas. Figure 1 in the appendix is a plot of power vs time for both Ron’s (test 2) and Wes’s (test 1) design using the same code on the straight track. Because Wes’s design was lighter, it travelled faster and finished to track quickly. Ron’s design was heavier and used more power because it took much longer to reach the same distance. This supports the conclusion that Wes’s design is more efficient than Ron’s. The specific scoring and screening data comparing the reference, Wes’s and Ron’s AEV can be seen in Table 1 and 2 in the appendix. The scoring results also show how Wes’s design is better in most all other aspects.
At the start of testing, the team realized they had a faulty propeller and had to get it replaced. The team also experienced disconnection of the motor wires multiple times during the testing process, they had to be fixed by the TA each time. Loose wiring could have affected performance throughout the test however the propeller was fixed before any testing was done so this did not affect any results. Therefore it is important to check all parts of the AEV before testing and collecting data. Other potential errors could have been starting the AEV at an inconsistent spot at the beginning of the track, a slight change could have affected the arduino code in term of marks and timing. This could be fixed by being consistent with the AEV placement for example placing the end of the back wheel at the starting mark every time, there would still be slight variations with each run but this cannot be controlled.
Team K recommends simple basic designs that use less parts also a vertical orientation for the base. Less parts allows the AEV to be lighter and therefore have less drag and be more energy efficient. It also makes the AEV cost less and easier to maintain. The vertical orientation is more aerodynamic than a horizontal orientation which will increase energy efficiency. As far as coding is concerned Team K recommends staying away from coasting the AEV to the gate and using time to judge distance. To avoid coasting, absolute position and air brakes are used to get the AEV as close to the gate as it needs to be and then reverse the motors and spike the power for a short spurt. This will give the AEV a more consistent ability to stop before running into the gate. Because distance is not affected by irregularities in the track like increased friction the AEV will make it to the gate correctly more frequently than code that relies on coasting. Using purely time to judge how far the AEV needs to go leads to inconsistency in stopping time because of things like friction.