NavX MXP Continuous Angle to Calculate Derivative

[notmattlythgoe]

Originally Posted by dougwilliams

You should be able to use some modulo arithmetic operations to solve the jump from 0 / 360. I'm not sure how you have it configured but on our we have the issue because it jumps from -180 / 180.

Question though - what are you trying to achieve by closing the loop to a specific turning speed? We use the same setup and close the loop on the current field orientation angle. In that way you can have the robot quickly turn when it's farther away from the set point, and slow down as it approaches where you want it to be so you have minimal overshoot.

One thing we've been trying is using a closed loop to control the rate at which the robot turns and then use a P controller to tell the first controller how fast to turn based on how far away from our target angle we are.

[MichaelBick]

Originally Posted by notmattlythgoe

One thing we've been trying is using a closed loop to control the rate at which the robot turns and then use a P controller to tell the first controller how fast to turn based on how far away from our target angle we are.

We did something similar this year. We ended up running a rotational velocity P controller with feedforward as the baseline of our turn controller. We summed the output without the feedforward, and limited to +-20% voltage to help prevent windup. A PD controller on turning angle was the input to the velocity controller.

There was definitely a noticeable improvement on the conventional PID controller. One problem we were facing without the velocity controller was that our turns were highly dependent on momentum. We really would have liked to run the velocity loop underneath our teleop driving code too, but integral windup caused a lot of unpredictable behavior over long periods of time.