Result and discussion
The team came up with two prototypes, Design E and Design F. Design E was built with a battery, an Arduino, two motors and propellers, an L-shaped arm, two wheels, a T-shape base and two trapezoids. Design E can be distinguished with the deployment of wings on both sides of AEV and used of two motors. The target for this design was to provide stability for AEV in straight line and in turn, and to complete the run as fast as possible. The second prototype, Design F, was built with a battery, an Arduino, one motor and propeller, an L-shaped arm, two wheels, and a rectangle shape base. This prototype focused on simplicity and energy efficiency. Regarding the system used to propel the AEV, the AEV used EP-3030 Pusher propeller configuration in forward movement (from starting point to the designated area to pick up the caboose) and used EP-3030 Puller configuration in reverse mode (from the designated area to pick up caboose till the endpoint). The team decided to use EP-3030 pusher propeller in forward mode because the propulsion efficiency is higher than for puller propeller. The decision to only use a pusher propeller when moving in forward mode is because the design would be much complex if the team opted for pusher propeller in both reverse and forward mode.
The team would need to use servo motor to change the direction of the motor to ensure the forward and reverse mode use pusher mode. This will increase the power use. The other option was to place another motor in the front of the AEV. For this system, the AEV will use the back motor in moving forward and will use the front motor in moving backward. However, this will increase the weight of the AEV. That left the team with the option to use both pusher and puller propeller. Based on the propulsion efficiency graph for EP-3030, within 30%-40% power setting, the propulsion efficiency does not differ much for pusher and puller. Thus, the team believe that this would be the best option for the AEV. Design E used 30% power setting in forward and reverse mode. Design F previously used 30% power setting in forward move and 40% power setting in forward move; however, due to inconsistency problem that the team faced in reaching the designated area to pick up the caboose, the team decided to increase the forward mode power setting to 35%. The inconsistency in forward mode faced by Design F of the AEV was that the AEV sometime struggles to even move with 30% power setting. Design E and Design F are shown in Figure 2 and Figure 3 below.
The first prototype, Design E, was based on the team’s individual AEV prototype design. All designs focused on the deployment of wings on both sides of the AEV. Affiq and Haiqal built a 90 degree wings on the AEV. Zam and Akmal combined a slanted wing and a 90-degree wing designs on the AEV. After having some detailed discussion within the team members, the team decided to only deploy a slanted set of wing on the team’s first prototype, Design E. This was because the team wanted to minimize the cost of the AEV, increase the maintenance efficiency, and to minimize the weight of the AEV. The team opted for two motors and propellers because three of the team members used two sets of propeller and motor on the individual design. They believed that two sets were required to ensure the AEV completes its mission within the time limit. In contrast, Haiqal opted for one motor because he wanted to focus on energy efficiency. The team also decided to attach the two sets of motor and propeller on the base of the AEV instead of on the wing of the AEV. Three of the team members attached the set of motors on the wings. Only Haiqal opted to attach the motor on the base of the AEV. He believed that this will transfer most of the weight of the AEV on the base instead of the AEV. The team decided to build the team’s AEV based on this concept because the AEV will be much more balance when moving as most of the weight is on the base which is the center of the AEV. This will improve the center of gravity of the AEV.
Meanwhile, the second prototype, Design F, was based on the deficiency of the first prototype. The first prototype was shaking a lot in turn and also when it was about to stop. The team tried to reduce the power setting but the situation did not change much. The team decided to build the second prototype with a completely different concept than first design. The wings did not help much in term of stability of the AEV because the speed of the AEV was not enough to require the need of the wing to influence the AEV. The team believed that the wing played a small role on the AEV because the power setting used for the AEV was not too high. A greater power setting which leads to greater speed might require the wing to provide more balance on the AEV. This comparison can be exemplified based on the difference between an F1 car and road car. An F1 car without a wing will surely decrease the speed of the car because this will cause the car to be more unstable. The team also consulted on Haiqal view on using just one motor because Haiqal’s individual design used only one motor. Based on his idea, he said that the use of one motor will be enough for the AEV to complete the MCR within the time limit and the use of one motor will surely decrease the power used. Finally, the team decided to stop using the wing concept and to use only one motor for the second prototype, Design F.
Next, the team decided not to use any extra parts from the 3D printing or from the external sources for the AEV’s final design. The team aimed to build an AEV that has a low cost and light in weight. Since the team believed that the usage of servo will not affect the performance of the AEV, the team decided to not use the servo motor to reduce the weight of the AEV and minimize the production and maintenance cost of the AEV. The total cost to produce a similar unit of the AEV is $139.14 and the weight of the design is 218 grams. For the first prototype, the design was complex because it used a lot of parts and two motors. It obviously increased the cost of the AEV itself and the team decided to come up with a new design that only uses one motor and a little number of parts for the AEV. Finally, the cost of the AEV was decreased and the AEV still can run smoothly on the track with all the modification that has been made.
The team have performed four type of performances tests to investigate the AEV condition in many aspects such as the design, coding, and energy efficiency. Based on those performance tests, the AEV have undergone multiple cycle of designing in every process of performance test to make it more stable and have an efficient energy. For the performance test 1, the team constructed two different AEV with different concepts and physical design. The team decided to maintain the usage of the 3.0 inch propellers in a push configuration when moving forward to the R2D2 area and a pull configuration when moving back to the initial point of the track. This is because the team has analyzed the efficiency of the propellers during the System Analysis 1 lab and found out that it would have adequate thrust to pull the cargo back to the starting point.
The team started with the first design that called as the ‘Design E’ and then, the second design which was the final design of the team called ‘Design F’. The design E or the first prototype was the product of the creative design skills lab which every team member needs to come up with their own ideas on the design of AEV and the team needs to choose one of them to proceed with the next lab. The first prototype used two pusher motors that placed on the back of the AEV. The team also used the T-shape arm as the base of the AEV and deploy the wings on the side of the AEV to maintain the stability and center of the gravity of the AEV when moving in the straight and curve track at the lab. However, the first prototype has problems because it uses a lot of energy, it is not stable when moving on the track, and it is experiencing heavy shaking upon stop before the gate. Meanwhile, the idea of second prototype was come from the discussion between the team members about the theory of the helicopter that only uses one motor on top of its body to fly on the sky. The team was provoked to generate the ideas and finally the team come up with a much simpler design which only consists of one motor and one rectangular shape as the base of AEV. Both designs were finalized and the team noticed that the modification that has been made on the AEV brings more positive impacts because it used less amount of energy and the second prototype obtained a higher score in the concept screening and scoring which was held among the team members. Thus, the team agreed to proceed with the second prototype as the team’s final AEV design.
For the performance test 2, the team decided to focus on the code that controls the movement of the AEV on the track. This performance test is the most difficult test because it needs to undergo numerous number of error and trials to minimize the energy used by the AEV. Initially, the code was developed with more focusing on the distance travelled by the AEV on the track. The distance was calculated to produce the exact marks for the AEV needs to travel along the track. The team decided to use reverse function to stop the AEV at the gate, cargo area, and final point of the track. The coding was working smoothly on the track but it uses a lot of energy. The reverse code counter the forward movement of the AEV, thus producing spike on the graph which shows that it uses a lot of energy even though it only uses for a second. The team used 30% of power for the forward move of the AEV to the cargo area and 50% of power when coming back to the final point. Finally, the team found out that the AEV uses 265.99 Joules of energy when it is implemented with this type of coding. Next, the team decided to try a new coding with a different approach that more focused on the time taken for the AEV to reach from one point to one point. The team is focusing on the ‘goFor’ code compare to the ‘goToAbsolutePosition’ code which was used in the first coding because the team believed that the AEV will work smoothly if the time is measured accurately for the AEV to move to one point. The track was divided into four quarters. The team used the stopwatch to measure the time taken for the AEV to move in between the point in the quarters with a 30% motor speed. After several trials, the AEV was successfully completed the track and it was observed to use more energy compared to the first coding. There is an increase usage of energy from the previous code so the team decided to proceed with the first coding that focusing on the distance travelled by the AEV for the final testing of AEV in the performance test 4.
When preparing for the final testing on lab performance test 3, the team encountered a few problems. The team found out that the AEV was experiencing inconsistency every time it was tested on the track. After several runs, the team come up with two hypotheses of the AEV’s inconsistency on the track such as the number of mark used for the coding is not equivalent to the calculation that has been made based on the length of the track and the power of battery that affects the coding to run on the AEV. The main problem with the AEV was it does not consistently stop between the two sensors, thus blocking the gate and the rest coding of the AEV. So, the team decided to have a discussion with the instructor and the teaching assistants to find the solution for the problems. The team found out that the second hypothesis is true, which means that the battery power is affecting the coding of the AEV. The battery power needs to be larger from a certain value so that the coding will run smoothly. After several times testing the AEV, the team will check for the battery voltage so that it beyond the minimum requirement of the standard battery. Next, the team found out that there are many scratches on the reflective tape on the wheel of the AEV. The scratches are affecting the sensor to count the marks travelled by the AEV, thus resulting on the coding of the AEV. The team get a suggestion from the teaching assistant to change the tape and later, the AEV run smoothly and complete the MCR. The team also have made some improvements on the AEV such as using the 40% of motor speed instead of 30% because the team realized that the AEV is running very slow when using 30% of power and it will affect the inertia of the AEV. The team wants to have an optimum value of inertia to stop the AEV in the range of the sensors. The team also did not use the mini-servo motor because it will produce spike in the energy level of the AEV, thus increase the amount of energy used.
Looking at bigger picture, it can be concluded that the EP 3030 has a greater efficiency overall. Even though the EP-2510 propeller has a greater efficiency at low power setting; however, at 15%-25% power setting, the AEV can barely move. This shows that to only consider the efficiency of the propeller at this power setting is irrelevant in deciding of what type of propeller to be used. As the team was looking to move the AEV between 30%-40% power setting, this is the range on the figures that the team should consider in making decision for the AEV. Within this range, the propulsion efficiency for between pusher and puller of EP-2510 differs quite a lot. This is the reason on why the team decided against using EP-2510 propeller. Moreover, EP-3030 propeller produces a greater speed on the same power setting than the EP-2510 propeller. Within 30%-40% on EP-3030 propeller, the propulsion efficiency between pusher and puller configuration does not differs a lot. That is why the team decided to mix both configuration to reduce the complexity of the construction of the AEV. To create an AEV with only pusher configuration will requires the use of servo motor, or it will require a more complex design to place one motor at the front of AEV and another motor at the back of the AEV. Thus, the use of one motor that will use both pusher and puller propeller would be the better way for the AEV. The propulsion efficiency vs advance ratio graph for both types of propellers configuration are shown in Figure 5 and Figure 6.
Generally, the phase breakdowns are divided into four major phases. The first phase is when the AEV moves from the starting point to the gate. This phase includes Phase 1 to Phase 7. The second major phase is when the AEV moves from gate to the point where it will pick up the caboose. This phase includes Phase 8 to Phase 14. The third phase is when the AEV moves from the point it pick up the caboose back to the gate. This phase includes Phase 15 to Phase 21. Finally, the last phase is when the AEV moves from the gate back to the endpoint. This phase includes Phase 22 to Phase 26. The power used against time with phase breakdown is shown in Figure 6.
All the four major phases used almost the same functions. According to Table 3, most of energy was being consumed when goToAbsolutePosition(marks) is used. The three major phases used almost the same function which were reverse(motors), motorSpeed(motors,speed), goToAbsolutePosition(marks), goFor(time), and brake(motors). All of the four major phases have the same pattern except that the last phase (from gate back to the starting point) where the reverse(motors) function was not used. The peak of the graph can be seen where reverse(motors) and motorSpeed(motors, speed). No peak was seen at the fourth major phase. Moreover, the most energy was consumed when goToAbsolutePosition(marks) is used. This can be seen at Phase 2,9,16, and 23.
In Performance Test 4, which is the final testing, the team needed to run the AEV for two times and being evaluated by the instructional team. For the first run, the AEV ran smoothly in the first quarter and the second quarter. The only problem was the AEV did not stop for 5 seconds when it has connected with the R2D2 and team was deducted with 4 marks. On the third quarter, the AEV failed to stop in between of the two sensors and the AEV needs to be stopped with hand so that it will not pass the second sensors. The team was again deducted by another 2 marks for that. For the fourth quarter of the track, the AEV run smoothly and manages to stop in the right places without hitting the green foam. The team only gets 34 marks over 50 for the first run of the AEV. The teaching assistant did not give any marks for the fourth quarter because the team has used hands to stop the AEV on the third quarter. After discussing with the teaching assistant, there is a confusion in the grading of the final testing and the team still have the second chance to improvise the score. The main problem for the first run was the AEV did not stop for enough time on the second quarter and the mark used on the coding for the third quarter was a bit larger and the AEV did not stop in between the sensors. For the second run, the team only gets 42 marks over 50. The AEV starts smoothly in the first and second quarters. Unfortunately, the AEV did not stop on the first gate and 2 marks was deducted for that. For the third quarter, the AEV faced the same problem with the first run. The AEV did not stop in between the two sensors and the team need to use hand to pull the AEV towards the first sensor. When the AEV starts to move towards the fourth quarter, it faced a big problem since the AEV did not stop between the final ranges that stated in the MCR. The team believed that the battery was the main reason for the inconsistency that happens during the run. After the run, the team decided to check the battery level using the voltmeter and the team found out that the battery level was below the minimum requirement for the coding to work smoothly on the track.