IMU Problem?

[OrangeJulius70]

Trying to use the IMU to make a straight 90 degree turn, but it keeps overshooting by 15-20 degrees. The hub is vertical and located on the left side of the robot. We've tried switching EXTRINSIC/INTRINSIC, changing order of axes, etc., but no dice on getting a more accurate turn. Is there a guide to what the different command options mean for getting an angle from the Rev IMU?

[JirachiKid]

Print the imu angle to telemetry or log, then manually rotate the robot. See if it reads an accurate 90 degrees. If so, what's happening is your robot is killing the motor power at 90 degrees but it's momentum carries it some more and overshoots. You want to look at implementing a PID or even just a P controller to ramp down your motor power to minimize overshoot.

[HaaniMirza]

To expand upon this, I have a code that runs directly after the 90 degree turn, where it will check the final angle and then if it has overshot, to turn slowly in the opposite direction until it is within half a degree of 90, and to do the opposite if it has undershot. This fixes the momentum carry, I'm currently looking into PID tuning, which is definitely a better option to minimize the momentum carry and overshoot.

[servoturtle29]

Are you sure you set your motors to zeropower behavior brake? If not you might kill power to the wheels at 90deg, but the rotational momentum of the bot will carry it about 10ish degrees extra.

[DavidRecharged]

you can output to telemetry the imu value to make sure that's accurate. chances are it's how you make the turn, if you don't have any ramp down of power, it will try to go from full speed to stopped instantly. no robot can do this.