IMU class should use the robot's orientation

[jtechau]

The IMU classes (e.g. IMUSubsystem16470, IMUSubsystem16448) include methods to return values for the three gyro axes. These methods should represent rotation and direction relative to the robot's coordinate system rather than the sensor's coordinate system.

This means, for example, that the IMU class should translate the axes as appropriate so that the getYGyro() method returns the angle of the robot's left-right axis, where tipping the front of the robot up is a negative rotation. Likewise, the getZGyro() method should return the gyro's heading, where a robot counter-clockwise rotation (looking down from above) is positive. These translations may/will depend on the type of IMU used and it's orientation within the robot.

The orientation (and possibly type) of the IMU in this year's robot isn't yet known. This issue should only be closed after the orientation of the IMU in the robot has been assigned and the IMU class updated accordingly.

As a placeholder, since we're currently using Lint for testing, the translation should be defined to match the type/orientation of the IMU on Lint.

https://docs.wpilib.org/en/stable/docs/software/advanced-controls/geometry/coordinate-systems.html#robot-coordinate-system and https://docs.wpilib.org/en/stable/docs/yearly-overview/yearly-changelog.html#breaking-changes (see Danger box)

[MasonGomez1388]

IMU16448's X and Z axis are opposite of IMU16470's

[jtechau]

The ADIS16470 axis orientation can be found in the datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ADIS16470.pdf

The ADIS16448 axis orientation can be found in the datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/adis16448.pdf

These diagrams must be matched to the orientation of the sensor relative to the roboRIO. Further, the corresponding WPILib class may translate some of these axes or axis polarities, so the value returned from each class should be correlated to observed values.

[jtechau]

See also: https://www.chiefdelphi.com/t/analog-devices-adis-16470-eng-basic-java-gyro-code-help/422553