Wylie East Regional Qualifier Code Post-Mortem

Tags: control
Personhours: 20
Wylie East Regional Qualifier Code Post-Mortem By Mahesh and Cooper

Task: Reflect On Code Changes And Choices Made During The Wylie East Regional Qualifier

Despite putting in lots of effort in order to pull off a working autonomous before regionals, small and subtle issues that surfaced only during testing at the competition as well as various other small bugs with our autonomous routine prevented us from performing well on the field. Trying to write a full autonomous in the last week before competition was a huge mistake, and if more time was dedicated to testing, tuning, and debugging small issues with our code base, we could have accentuated the theoretical aspect of our code with actual gameplay on the field. The issues experienced during the Wylie East Qualifier can be boiled down to the following:

Improper Shutdown / Initialization of the Webcam and Vuforia

We frequently encountered vuforia instantiation exceptions after attempting to initialize the camera after an abrupt stop. We suspect this issue to have originated from the improper shutdown of the Webcam, which would likely result from an abrupt stop / abort. During later runs of our autonomous and teleop with multiple, more complex vision pipelines, we saw that attempting to reinstantiate Vuforia after it has already been instantiated resulted in an exception being thrown. This issue caused us to not play in certain matches, since our program was either stalled or its execution was delayed from restarting the robot.

Disconnection Of The Webcam (Inability To Access Camera From Rev Hub)

Ocassionally when attempting to initialize our robot, we saw a warning pop up on the driver station which read "Unable to recognize webcam with serial ID ..." indicating that either the webcam had been disconnected or was for some other reason not recognized by the rev hub. On physical inspection of the robot, the webcam appeared to be connected to the robot via USB. The solution we came up with was to quickly disconnect and reconnect the webcam, after which the warning disappeared.

This issue prevailed in other forms on the competition field, however. Sometimes, during gameplay, when the webcam was accessed, the blue lights on the rim of our webcam would not light up (meaning that the webcam was not active), and our program would stall on skystone detection. This happened despite getting rid of the driver station, warning, and is most likely another result of improper initialization / shutdown of vuforia after an abrupt stop or abort.

State Machine Issues

At the end of our autonomous, if the statemachine had completed, our robot would proceed to spin slowly in a circle indefinately. This unexpected behaviour was stopped using a stopAll() function which set all motor power values to zero, effectively preventing any functions which messed with the robot's movement to be ignored at the end of our statemachine's execution.

Lack of Testing / Tuning

By far the biggest reason why we did not perform as predicted at the qualifier was because of the lack of testing and tuning of autonomous routines. This would include running our statemachines multiple times to fine tune values to minimize error, and debug any arising issues like those that we experience during the competition. A lack of tuning made the time spent on our skystone detection pipeline completely useless as our crane did not extend to the right length in order to pick up the skystone, a direct result of inadequate testing. All of the above issues could have been prevented if they had surfaced during extensive testing, which we did not do, and will make sure we follow in the future.

Next Steps:

In the future, we ultimately plan to put a freeze on our codebase at least 1 week before competition, so that the remaining time can be spend for building, driver practice, etc. Additionally, we have agreed to extensively test any new additions to our codebase, and assess their effect on other subsystems before deploying them onto our robot.

Date | February 15, 2020