D. Week 4 (Power Plots and Design Testing)

In Week 4, students continued to work on the preliminary R&D labs. Students created power vs time and power vs distance charts and ran screenings for two designs.

 

A code for testing power parameters was written first, then the AEV was attached to the straight track in the laboratory. Members split work by sharing code on Codeshare (https://codeshare.io/5z63qW) while others documented the results of the first run. The following is the code used to test the power:

First Track Run Code

celerate(4,0,25,3);
motorSpeed(4,25);
goFor(1);
motorSpeed(4,20);
goFor(2);
reverse(4);
brake(4);

The first run was not successful. The AEV did not move in the correct direction, and very little distance was covered.

Revisions were made to the first run code, and the AEV was mounted on the straight track for a second run.

Second Track Run Code

reverse(4);
celerate(4,0,25,3);
motorSpeed(4,25);
goFor(1);
motorSpeed(4,20);
goFor(2);
reverse(4);
motorSpeed(4,25);
goFor(2);
brake(4);

The second run was similar to the first. Revising the beginning of the code to reverse the motors did not move the AEV in the correct direction. Furthermore, very little distance was covered.

A third revision to the code was made. The power level for the code was increased to 30% to see if more distance would be covered. In addition, the AEV was placed on a sample track on a table versus having it run on the suspended track from the ceiling.

Third Track Run Code

reverse(4);
celerate(4,0,25,3);
motorSpeed(4,25);
goFor(1);
motorSpeed(4,30);
goFor(2);
brake(4);
goFor(5);
reverse(4);
motorSpeed(4,25);
goFor(2);
brake(4);

In this run, slightly more distance was covered. There was also a noticeable increase in power output from the motors and propellers.

A final code was written for testing the AEV on the suspended classroom track. The code was written to run at the maximum allowed speed to ensure the motors operated correctly and that the AEV moved in the desired direction.

Final Run Code

reverse(4);
celerate(4,0,40,4);
motorSpeed(4,40);
goFor(3);
brake(4);

The final code proved to be very successful. The AEV ran very quickly and covered a large distance to provide data that can be worked with properly. Power vs. Time and Power vs. Distance graphs were generated.

 

Power vs. Time

The above plot demonstrates that power increases in an approximately linear fashion as the AEV continues to increase its speed. A peak in power is seen at approximately 4.20 seconds, which is when the braking procedure began. The power then continued to at approximately the same voltage of 15.10 volts as the braking continued, then the power dropped once the AEV was removed from the track

Distance vs. Time

The above plot demonstrates a linear relationship between power and time. Although there were minor fluctuations, the AEV ran at approximately 15.80 volts for distance of 2.22 meters, then dropped sharply once power to the engines was cut and the AEV coasted for the remaining time.

For the final part of the pre R&D labs, concept screening and scoring matrices were made to determine which designs would be selected moving forward.

Concept Screening Matrix

  • Stability: Weight distribution and symmetry of design
  • Low Blockage: Whether or not there are wires and other parts on the wheel arm
  • Easy Maintenance: How easy the design would be to assemble/disassemble on a day-to-day basis
  • Durability: Existence of possible points of failure
  • Safety: Possibility of falling, crossed wires, other breaches of design rules
  • Cost: Lower cost is more desirable
  • Weight: Lower weight is more desirable
  • Arduino Access: How accessible the USB Mini port is
  • Battery Access: How easy it is to insert/remove the battery

Concept Scoring Matrix

Clearly, based on the most important criteria the group chose, Design D will be the most effective, and is the concept that will be used going forward. In the event that D is not functional, a modification Design B will be used instead.