Sam Evans, Anthony Lokar, Concept Screening & Scoring
Alejandro Nunez, Benjamin Schneider
Group A – Instr. Richard Busick, GTA Jin Yang February 6, 2015
Executive Summary
During the concept screening and scoring process, the team became familiar with techniques to decide on the design of the Advanced Electric Vehicle (AEV). The team also became familiar with a method to score the team’s drafted concepts by creating and testing a program that made the sample AEV follow specific operations. Using the sample AEV data as a reference, the team then utilized concept screening and scoring methods for the designs. The methods assist in organizing and evaluating the team’s thoughts to create the most efficient and plausible design.
To test the sample AEV on the track, an Arduino program was created to do several functions. First, both motors were accelerated from 0 to 25% power. Next, the motors were run at the 25% power for 1.5 seconds. The motors were then programmed to run at 20% power for 3 seconds. Then, the motors ran in the reverse direction for 2 seconds at 20% power before the program was ended. When the AEV was placed on the test track it performed exactly as expected. The AEV moved forward when the motors were started and continued until it came to a stop when the program ended. See “CCS1” in the Appendix for the code used to complete these tasks.
Due to the similarities between design A and C, the team decided to combine these sketches during the concept screening phase and incorporate features of each into a new design (See Figure 1 in the Appendix). With two motors at opposite ends of the aircraft, design A+C out performed other vehicles in both balance and directional efficiency, scoring a five and four in each category respectively (See Figure 2). These were both categories the team put heavy emphasis on. The vehicle’s small base also made the AEV lighter than the sample AEV, allowing the motors to exert less power to receive same level of thrust as heavier models. With an open body and spaced out parts, it would also be relatively easy to maintain and repair. The team looks to move forward with this design.
Design B also used fewer materials than the sample AEV. The reduced weight would require less energy to propel the vehicle the same distance. The rotating motor at the bottom of the vehicle would also allow the propeller to move directions. This action minimized the need for a second motor, without hindering the vehicle’s directional efficiency when compared to the sample AEV. However, placing the motor at the underside of the body could potentially damage the motor and propellers if the AEV derailed or was dropped. This risk made it less durable than the sample AEV (see Figure 2). Also, with only one motor, the AEV would travel at a slower speed compared to the sample AEV.
Design D was based off of the sample AEV and was rated similarly in aspects such as balance, durability, and aerodynamics. The design did have less body components than the sample, reducing its weight slightly. The reduced weight meant that less energy would be required to propel the vehicle. The cylinders around the back of the propellers in design D helped direct air flow going forward. While traveling in the reverse direction though, both cylinders limit the airflow to the propeller, reducing its directional efficiency, similar to the sample. The cylinders would also have gotten in the way of maintenance of both the motors and the propellers on the vehicle, making repairs more difficult. With aid from the concept screening chart (Figure 1) the team decided not to pursue this design.
While testing the AEV on the sample track, various errors were encountered. On the sample track, the AEV began moving in the wrong direction. The team reversed all motors at the start of the code, but the issue persisted; and, upon further inspection, it was noticed that two codes had been uploaded to the AEV—the one for the trial and the one from previous operations. By checking the code and looking for errors in the sketchbook program, the team was able to identify adequately eliminate coding errors that affected the AEV’s performance on the track.
While uploading code to the Arduino, the team recommends ensuring other codes are closed on the sketchbook. If more than one code is open, both codes will be uploaded to the Arduino, and the AEV will function improperly. It is also recommended that there be a person following the AEV on the test track in case it falls or continues running past the stop mark. That way the vehicle can be retrieved before any permanent damage is done.
This experiment showed the utility in using screening and scoring techniques. By using such techniques, the team analyzed the different parts of each design and weighed the importance of each. Putting these values into a scoring matrix revealed which designs the team should develop. During this process design A+C scored the highest, and will be developed in the future.
Appendix
(Click to enlarge images)
Table 1: Concept Screening Chart
Table 2: Concept Scoring Matrix
