[ratdude747]

Originally Posted by Ether

If you want want to use the WPI library PIDs, you can create "setpoint" and "process_variable" inputs for them as follows (assuming angles in degrees):

angle_error = target_angle - measured_angle;
angle_error -= 360*floor(0.5+angle_error/360);

then:

setpoint = angle_error;
process_variable = 0;

OR

setpoint = 0;
process_variable = -angle_error;


The disadvantage of the first approach is that the Derivative term will be disabled since the WPI Lib PIDs only look at the derivative of the process_variable.

The disadvantage of the second approach is that, although the Derivative term will be active, it will respond to changes in BOTH the measured_angle as well as the target_angle, so be careful how you adjust it.

Notice that the first two lines of code above (calculating the angle_error) calculate the shortest angle distance to the target. You need extra conditional logic only if you want to change the sign of wheel speed. See the discussion here.

i already have the sign change code.

my concern is it going all the way around from say 0 to 7pi/4 as opposed to only moving a distance of pi/4.

my only real knowedge of pid is you give it a setpiont and a process variable and it controls a motor within given range of outputs. a lot of the nuts and bolts i have yet to learn.