Executive Summary
The purpose of the labs have been to analyze the different components of the AEV, as well as different designs, to narrow down ideas for the AEV that can best complete the mission objective. This process was composed of several different specific objectives that helped to direct the lab work: what propeller type had the best performance, how accurate were the reflectance sensors, how is the design impacted by the team’s criteria, how is the code impacted by the design and physics of the AEV. The propeller has a significant impact on the thrust and power efficiency of the AEV which is why it is crucial to choose the best one. Also, the accuracy of the reflectance sensors is crucial so that the AEV moves to the correct position indicated by the code consistently. The team’s criteria are important since it is used to help make decisions between competing AEV designs. It is also important to consider how aspects like mass, balance, and inertia impact the physics of the AEV since the code needs to incorporate adjustments for all of them. These objectives help to maximize the AEV’s performance in picking up and delivering the R2-D2 unit across the track.
The AEV is important to the Alliance since they need a vehicle that can transport R2-D2 units with limited resources. Power is limited on the planet which is why it is crucial to have the AEV be as efficient with its power supply as possible. Another important factor is its ability to run along either track consistently. To meet these objectives, the AEV designs will use as little energy as possible without compromising the primary objective. Also, the code will account for all inhibiting factors while also making sure that the AEV stops at the appropriate locations and for the proper amounts of time.
There were several significant changes made to the code and final design of the AEV during Performance Tests 1-3. During Test 1, the team confirmed that the combination design performed much better than the reference vehicle that was previously used. This design incorporated the 3D printed dome and was based upon the cross-piece as the main platform. This design had a much better balance than the previous design in addition to its more appealing Star Wars appearance. In Test 2, the team decided to alter the code so that the AEV would move faster and coast more. In order to incorporate this the power for the motors was greatly increased in the initial start and other distances when the track is straight, but when the AEV would move to round the corners the power would be cut and have the AEV coast into the gate sensors and docking areas. This effectively made the AEV faster and more efficient with its power. For Test 3, the team looked into ways to make the AEV more power efficient. First, the team decided to remove the front trapezoidal pieces since they did not provide much to the AEV’s features other than the looks. In addition, the team worked to make the coasting more consistent and looked into possibilities of reducing power at certain portions of the track. Removing the pieces helped to improve the mass ratio and the energy was able to be reduced by several joules.
The lab scenario could be improved by incorporating a time element into the objectives. Currently it is satisfactory if the AEV completes the task in under two and a half minutes. It would make sense that the Alliance would want the droids to be delivered as soon as possible, though not compromising efficiency or effectiveness. The time does not have to be reduced necessarily, but it could be added that the droids should be delivered as soon as possible. Another idea could be to give bonus points based on how fast the AEV completes the task under a certain time, encouraging teams to add this other element to their AEV code and overall design process.
Table of Contents
| List of Tables and Figures | 4 |
| Introduction | 5 |
| Experimental Methodology | 5 |
| Results & Discussion | 6 |
| Conclusion & Recommendations | 13 |
| Appendix | 15 |
List of Tables and Figures
Tables:
| Table 1: Lab 5 Concept Screening Sheet | 9 |
| Table 2: Lab 5 Concept Scoring Matrix | 9 |
| Table 3: Team M Semester Schedule | 15 |
| Table 4: Final AEV Bill of Materials | 17 |
Figures:
| Figure 1: Map of the Track and Gate | 5 |
| Figure 2: AEV #1 SolidWorks Design | 7 |
| Figure 3: AEV #2 SolidWorks Design | 8 |
| Figure 4: Supplied Power vs Time | 10 |
| Figure 5: Propulsion vs Advanced Ratio 3030 Propeller | 11 |
| Figure 6: Final AEV SolidWorks Design | 16 |
| Figure 7: AEV Final Testing Scoresheet | 18 |
Introduction
The purpose of the labs in the AEV project have been to test the different components of the AEV, analyze different designs, to decide upon the AEV that can best complete the mission objective through scoring practices. The mission objective was create a vehicle that could transport R2-D2 units along a monorail system as efficiently and consistently as possible. The testing process was composed of several major tasks that helped to direct the lab work: what propeller type had the best performance, how reliable were the reflectance sensors, how does the design decided by the team’s criteria, how is the code impacted by the design and physics of the AEV. This report will help to convey how the team conducted testing, what results were taken from the testing, and how the AEV changed and performed throughout the whole process.
Experimental Methodology
The objective is to move the AEV through a gate and connect with the cargo, returning through the gate and stopping in the Drop-off Area. The AEV must start in the Drop-off Area, trigger the first sensor without triggering the second sensor, wait seven seconds for the gate to open, proceed to connect with the cargo, wait five seconds, return to the gate and trigger only the first sensor, wait seven seconds, and proceed to the Drop-off Area and stop.
Figure 1: Map of the Track and Gate
This procedure is centered around the AEV which is composed of several different key components: the Arduino Nano, the electric motors, the reflectance sensors, the propellers, the arm and wheels, body frame components, battery, and connecting bolts and screws.
Several different tests were used to help determine the effectiveness and aspects of these AEV features. One of the first tests was using a wind tunnel to determine whether the 3030 or 2510 propeller configuration was more effective. This consisted of taking data from each propeller after they were placed in a wind tunnel. The data was then used to determine which propellor would be implemented. The physical design was tested next, deciding between each group members’ drafts. These designs would be constructed and run along the track. Visual observation would be used to judge certain aspects like balance, and numerical data would be extracted from the AEV using MATLAB files. The team would then use all this information to fill out scoring matrices for each of the designs. Following this process, the reflectance sensors were tested in order to determine how accurate they were. The AEV would run along the straight track, which had a tape measure hooked up to it, and then the data would be extracted. The team would compare the physical marking on the track to the data given by the sensors to figure out the error. If the error was small enough, the team would continue using them, otherwise, the team would try to fix or replace the sensors. The last bit of testing involved three performance tests which focused upon design, code, and efficiency. The first test had two of the team’s designs run the track and compare observations and data. The second test had the team draft two different codes to complete the mission objective and see which one performed better. The third and final test had the team try different methods to improve the vehicle’s efficiency. The efficiency can be measured from the energy reading that is recorded by the AEV and the AEV’s mass.
Results & Discussion
The two Advanced Energy Vehicle designs that were analyzed by the group were relatively similar to each other in terms of appearance and basic construction. Both designs utilized the cross or “X-shape” piece as the main structural foundation with the “T-shape” arm used for both as the wheel mount for the overhead track. The first AEV design, pictured below as Figure 1, was a basic skeleton derivative of the further refined second AEV design.
Figure 2: AEV #1 SolidWorks Design
The first design features an open layout with the Arduino unit attached on top, the battery pack hung underneath, and the two motors mounted to 1’’ x 3’’ rectangular pieces in the rear (pusher configuration). The second AEV design, pictured on the next page as Figure 2, included increased stability due to the addition of several components.
Figure 3: AEV #2 SolidWorks Design
In addition to increased stability due to a more slender, aerodynamic design, the additional components, notably the dome shaped piece and the two forward trapezoidal pieces, were added to enhance the creativity of the AEV appealing to the Star Wars theme of the MCR with a Millennium Falcon inspired design. The second design also included a double bracket piece attached to one trapezoid in the front of the AEV to attach to the magnetic trailer system. The additional weight brought on by the added components for the second AEV design resulted in alterations to the code which will be discussed later.
The team’s initial four designs created in Lab 4 were screened for performance, efficiency, appearance, cost, etc. and were initially concentrated down into the current AEV #1 design and a combination of two previous designs. The combination design eventually evolved to become very similar to the first AEV design and would later become the AEV #2 design with the addition of the Millennium Falcon components. The team’s concept scoring sheet from Lab 5, pictured on the next page as Table 1, depicts the initial four designs considered by the group.
Table 1: Lab 5 Concept Screening Sheet
The reference design was a standardized AEV design that the group used to juxtapose their own designs. “Tom’s Design,” because of its comparatively good screening score went on to become the reference design in the concept scoring matrix, pictured below as Table 2. Eric’s and Charlie’s designs were combined to create the combination design which led to the development of the AEV #2 design.
Table 2: Lab 5 Concept Scoring Matrix
The final cost of the completed AEV was $162.46 and was broken down in the bill of materials, shown in the appendix. The team was able to lower the cost from the previous designs to the final design be eliminating the two forward trapezoid pieces, reducing the number of angle brackets, and refining the custom dome-shaped piece to have a simpler design which eliminated the need for supporting pieces. Additionally, the team was able to hand-paint and substitute trapezoidal pieces made from index cards to lessen the cost while still achieving the desired Millennium Falcon appearance. The performance tests had a large impact on the team’s design process and ultimately lead to a great deal of change in the final AEV design. Through the results of the performance tests, the team was able to agree on the AEV #2 design as the basis for the final AEV due to its increased stability and resistance to swaying erratically on turns and during bursts of power. The team also was able to maximize efficiency through the performance tests by eliminating unnecessary components to the AEV such as extra angle brackets and the forward trapezoids.
When observing the different designs perform on the track the lab group first tested out design one. When design 1 runs the design starts off slowly and gathers speed over time. Throughout the turn the design remains stable without any wobbling that could result in a potential fall thus causing harm to the vehicle. The repeatability of this design stays consisting throughout testing and hardly varies trial to trial. Below can be seen a graph of power supplied over time. The graphs of the two are similar due to the fact the code used for the graph only involved a constant output of power over a period of time not distance so only one graph is shown.
Figure 4: Supplied power vs time
When observing design two run the track using the same code the two vehicle behave incredibly similar. The main differences between the two designs is weight, and when testing the difference can be seen clearly. The second design speeds up much slower compared to the first and stops slower. The lab group expected this change because of the excess weight placed upon the AEV. While the weight changes the actions of the AEV the energy consumed by the AEV stays relatively the same. After talking the lab group came to the conclusion that this was because of the way the code is written; it is written in such a way that the motors are on for a set amount of time in the beginning in order to first get the AEV going. This initial jolt of energy allows the AEV to overcome static friction and get the AEV moving so when the motors remain at a constant speed the AEV is able to still accelerate quickly.
Figure 5 Propulsion vs Advanced Ratio 3030 propeller
When the lab group saw the results from the wind turbine lab the lab group came to the conclusion that the 3030 propellor works best at a speed that is not too fast. So in order to take this factor into account the lab group decided to slowly sleep up the AEV in order to keep efficiency up. This allows the propellers to use less energy while at the same time keeping efficiency high.
The Performance test allowed the lab group to come to a fairly important decision about the coding. The Performance test caused the lab group to look at the preferred method of stopping. During the performance test the lab group noticed some variability in the distance the AEV took to stop. It appeared the longer it took the AEV to come to a rest the more inconsistent to vehicle was. This led to the conclusion of stopping the AEV with a backwards thrust from the motors. This change in code allowed the location of where the AEV stops to be more accurately determined which is important for the opening and closing of the gate. Even a couple inches off could either cause the AEV to stop short or go to far.
During final testing the AEV was tested a total of two times with the first run being one of the worst in the class and the second being one of the highest scoring vehicles. The first time the AEV was tested the lab group was unaware that time was a factor in the final scoring of the run so the AEV moved very slowly completing the run in about 2 minutes. The AEV also stopped short of the first gate causing points to be lost for moving the AEV into the appropriate area to trigger the gate. However, the rest of the run the AEV performed exactly as expected completing the run without further errors. In this run the AEV, which weighs .294 kg, used 418 Joules of energy with an Energy to Mass ratio of 1421.8. The final score for this run was 57.6.
After learning from the first run the lab group discussed a new course of action to take, eventually coming to the mutual agreement that the code needed to be changed to allow the AEV to move faster. The lab group then increased the motorSpeed commands 10% – 15% as well as increasing the brakes. After a couple trials it became clear that the AEV was moving exponentially faster than previously, so that left the lab group to solve the problem of using too much energy. It was observed in the practice runs that the AEV was speeding up through the turns even though the AEV had ample speed to round the curve and reach the gate.What was done in order to fix this was the lab group cut off the power supplied to the motors 100+ marks away from where the AEV was normally stopping. Then the AEV was to coast to a specified mark where a reverse function was called and motorSpeed was initiated for one second to bring the AEV to a halt.
After all the changes to the code the AEV was tested once more. The results of these tests shocked even the lab group who even after implementing these changes did not expect the AEV to perform at such a high level. The AEV decreased it’s run time from 120 seconds to 52 seconds, a 68 second difference. The total energy used decreased from 418 Joules to 268 Joules, a 150 Joule difference. The Energy to Mass ratio went from 1421.8 to 911.6. The overall score for the run changed by 20.1 from 57.6 to 82.7, one of the highest scores in the class.
Conclusion and Reccomendation
Upon completion of the AEV project it was found that each individual portion leading up to the final design was crucial. First the group had to decide what propeller type was the best choice and after the wind turbine lab the 3030 propeller was a seen as the superior choice. One thing the group noted was that in order to keep the AEV more efficient, it is better for the propellers to spin more slowly as this would keep the power needed by the propeller down and would allow for the efficiency to be increased.
Once the propeller was chosen the group decided to go with a Millennium Falcon design for the group’s AEV. Initially the group was between two designs however the second design was chosen because with the addition of the two trapezoidal pieces and dome shape, this allowed for added weight which in turn made the AEV much more stable around corners. When the first design was tested it worked well, however, the group noted that it was too wobbly when going around the corners of the track and the group decided the Millennium Falcon design not only was aesthetically more appealing, but was more functional.
The code had to be altered between the first design and the Millennium Falcon design because the added weight made the AEV too heavy to move with the original code. The group decided to keep with the slow moving AEV code because if the group allowed for the AEV to coast to a stop, it was inconsistent and the AEV would hit the second sensor at the gate. The group decided to alter the design once again and the final design for the group’s AEV ended up being the Millennium Falcon inspired design, however, the trapezoidal pieces were replaced with index cards in the shape of trapezoids, the metal angle brackets were removed, and the dome shape and new index cards were painted to resemble the actual Millennium Falcon. This brought the overall weight down while still keeping the rigidity and stableness that the group wanted to achieve. This ended up being the final design because it offered the greatest stability, creativeness, and consistency when testing.
When the final design was completed and tested, the AEV did not perform the way the group thought it would. The total energy used was 418 joules, the energy to mass ratio was 1421.8, the run took 120 seconds, and the overall score was 57.6 which was one of the lowest of the class. The group decided to keep the design still, but had to alter the code significantly. The group decided that the time factor was the aspect that hurt the overall score the most. The new code utilized this idea and the group decided to simply make the AEV finish the run as fast as possible and the AEV coasted in some spots to reduce the amount of energy used.. With the final test the group was able to significantly improve results. The time went from 120 seconds to 52 seconds, total energy dropped from 418 to 268 joules, the energy to mass ratio was 911.6, and the overall score rose to 82.7. The group believes that its AEV is the best design not only because the group’s overall score was the highest in class, but also because of the creative Millennium Falcon inspired design. With the new and improved code utilizing the idea of finishing as fast as possible and allowing the AEV to coast in some areas, this brought the best overall results and performance. What the group would recommend for AEV projects in the future would be to make using the servo motor a necessity. Although the group did not use them, the group noticed that other groups were having a lot of success with stopping their AEV with the servo motor and it was very effective. Using reverse thrust functions work, but having a servo motor dedicated to braking would be much more efficient. Another thing that would be very useful is to allow groups to come and test their AEV on the tracks outside of class because the group felt it was necessary to have more time to test. There was a lot of time in class, however, because all groups were trying to test at the same time, our group did not always test as much as what would have been preferred. Overall the group felt that the AEV project was set up very nicely and the fact that it was a semester long project allowed for the ability to redesign the AEV to make it as efficient as possible and to make it perform as well as it did.
Appendix
Table 3: Team M Semester Schedule
Figure 6: Final AEV SolidWorks Design
Table 4: Final AEV Bill of Materials
Figure 7: AEV Final Testing Scoresheet