Week 9 marked the beginning of preparing for the first performance test. In order to do so, two AEV designs were tested with one final design being chosen. Furthermore, a code was developed so the AEV would run properly when picking up the caboose and stopping at the gate.
In order to succesfully complete the the first performance test, the AEV had to start on flat surface, climb up a slight incline, and brake in front of a gate for seven seconds until the gate was lifted. So long as the AEV stopped and passed through the gate without running into it, the test would be passed
To begin, the working AEV design was disassembled so a second design could be tested (see Team E Designs, Prototype Assembled AEV 2 for reference). The energy analysis procedure was repeated from using the previous code from Week 7. Shown below are the AEV and the plots comparing energy usage.
Prototypes 1 and 2 Energy Usage Comparison
Assembled Prototype 2
The Prototype Assembled AEV 2 ran well, decreasing energy usage by approximately 2 Joules. The working design was then modified to reflect prototype 2, leading to the final design for performance testing. The design was also modified so the servo may be fixed on. An aluminum foil casing was created to house the servo. Shown below is the final SolidWorks design AEV, as well as the AEV with the servo casing. Not pictured is the brake arm, which was constructed from aluminum, a flat bracket, and a 90 degree bracket surrounded with rubber and duct tape. When the servo is triggered, the arm swings up and the rubber hits the rail, effectively braking the AEV immediately.
Final Design Sketched in SolidWorks
Final AEV Design
Before completing the first performance test, the AEV was run on a straight track to test the servo. The initial angle of rotation was set to 60 degrees. After realizing too much stress was placed on the arm, the angle was readjusted to 48 degrees and a reverse function was added to the code to allow the AEV to move in the proper direction. Lastly, the marks units was adjusted to go for 280 marks. In three trial runs, the AEV stopped short of the gate for the proper amount of time, then successfully continued through.
Performance Test 1 Code
//reverse all motors to ensure correct direction of movement
reverse(4);
//initialize servo to correct direction
rotateServo(10);
//run all motors until vehicle reaches gate
motorSpeed(4,35);
goToAbsolutePosition(280);
//stop all motors and rotate brake to active position until gate opens
brake(4);
rotateServo(48);
goFor(7);
//return servo to rest position, run motor through gate and stop all motors
rotateServo(10);
motorSpeed(4,30);
goToAbsolutePosition(360);
brake(4);
The first performance test was a success. The AEV stopped short of the gate with room to spare and braked for 7 seconds, proving the effectiveness of the servo arm. No damage occurred to the AEV and no safety violations occurred either.
The Distance vs Time plot measures the success of the AEV during the test. The horizontal line between 7 and 14 seconds demonstrates the ability of the AEV to stop before the gate, and the slope afterwards shows that it was able to move forward once the gate opened.
The Power vs. Distance Plot measured a relatively linear pattern for the first 3 1/3 meters; about 9 watts were being used, demonstrating a lower energy output compared to previous designs. The power spiked just before 4 meters, demonstrating the brake command for the servo arm.
The Velocity vs Time graph represents the speed of the AEV at any given moment during the trial run. As expected, speed built up until the brake feature caused a near-vertical relationship, showing how quickly the vehicle stopped when the servo arm swung up.
The Voltage vs Time plot demonstrates the voltage usage during the test. The voltage peaked during the braking sequence, demonstrating the high power usage of the servo.