Motion Planning and sensor integration

[Ty Tremblay]

Originally Posted by MichaelBick

There has been an influx of very good gyros for FRC. Specifically the NavX is accurate over long periods of time, and even has a form of sensor fusion like you were talking about. It can be set up to rezero using the magnetometer when the robot stops moving. If you can afford it, using good gyro will give you a lot of improved performance over just using encoders.

Agreed. IMUs are much more reliable than gyros.

[Jared Russell]

In practice, a decent gyro will provide a quicker and more accurate estimate of yaw rate and heading for a differentially steered robot than using wheel encoders. Wheel slip is unavoidable, hard to measure, and varies a lot as your robot accelerates, decelerates, and bounces across an imperfect floor.

There are still valid uses of the encoders for measuring your heading, though. If your encoders aren't moving, you can "hold" the gyro heading to prevent drift (this is most useful before the match starts). And if your encoders are estimating a drastically different yaw rate than the gyro, that's a good indication that the robot has become stuck and has lost traction.