The third performance test required the AEV to complete the following requirements:
- Begin at starting dock
- Proceed to the gate
- Stop with front wheel between first and second gate sensors
- Pause for 7 seconds
- Proceed through gate
- Proceed to the loading zone at the opposite end of the track
- Connect to the caboose without the vehicle’s front wheel passing the initial position of the caboose’s front wheel
- Pause for 5 seconds
- Exit the loading zone
- Proceed to the gate
- Stop with front wheel between first and second gate sensors
- Proceed through the gate
- Return to the starting dock and stop there
In order to complete these requirements, additional lines of code were simply added to the pre-existing program used to complete performance test 2.
When pulling the caboose, the AEV motors required greater power inputs than when propelling the vehicle by itself, as was expected. Thus, the lines of code added to complete performance test 3 commanded the AEV to run at power percentages considerably higher than those used to complete performance tests 1 and 2. The same process that was used to complete these two tests was applied to this third performance test. An initial program was written and tested, observations were made, and changes were implemented accordingly.
The extra weight of the caboose affected the vehicle’s performance drastically, as the new lines of code had the AEV relying almost exclusively on motor propulsion as it traveled up to the gate. The first few times this was tested, the vehicle traveled too far before braking, however, so the absolute position at which the servo was commanded to initiate was increased. Once the program had been changed accordingly, the vehicle was able to propel itself up to the gate and stop there.
When the AEV traveled back to the starting dock, it relied primarily on the extra weight of the extra weight of the caboose pulling it down along the incline on the track. Thus, although the motors had to be run at a high power percentage in order to propel the vehicle past the gate, they were shut off almost immediately afterward, allowing the vehicle to coast all the way back to the starting dock, where the servo brake was activated. Initially, the servo brake was activated before the AEV had reached its final stopping position, but this was easily fixed by lessening the absolute position at which the servo was commanded to activate.
The entire program used to complete this performance test can be seen towards the bottom of the Arduino Programs page.