Plotting Location w/ Accellerometer Project

[Invictus3593]

Originally Posted by Ether

If you're using a properly-programmed true swerve drive*, you can compute position and orientation of the vehicle from the encoders on the wheels. But this introduces a different set of errors due to the dynamic response of the steering and wheel speeds in response to rapid changes in command. And all it takes to throw the computation off is one good bump that changes the orientation of the vehicle.

If you're using a skid-steer drivetrain, the relationship between the powered-wheel encoder readings and the actual vehicle movement during turns gets muddied considerably in ways that may not be easily predictable. Probably not a good solution.


*ie independent steering and drive for each wheel, with properly programmed steering angle and wheel speed for each wheel.

What about tank drive? Would it totally throw everything off?

While not accelerometer related, there have been a number of posts over the years describing issues with the "drift" associated with gyros over time and the error this causes when calculating field position. One method I've experimented with that seems to work well to compensate/eliminate most of this error utilizes two gyros. A high rate gyro for most turns (250 to 500 deg/sec), and a low rate gyro (30 deg/sec) for higher accuracy in slow curves and determining when the robot is stationary (for zero compensation). With the higher resolution of the low rate gyro, it is much easier to determine when you can automatically adjust the zero point. This method does break down when the robot is in continuous motion, but typically there are periods of time within a match (and certainly before the match starts), where the gyro can update its zero point. During bench testing, I was able to achieve a heading drift of under 2 degrees per hour when stationary. The heading calculation algorithm would automatically switch between the gyros at a 20 deg/sec rate (67% of full scale of the low rate gyro).

I'm not too familiar with gyros. Do you have any sample code I could take a look at?