Velocity PID Programming: Terms dependent on time

[Cal578]

Originally Posted by Tom Line

Correct pseudocode
Prop = (setpoint - measured_value) * Prop Gain
Der = (error - previous_error)/dt * Der Gain
Feed_Forward = Last_Output
Output = prop + int + Feed_Forward

We're getting closer.
1. The "int" term needs to be defined. I think you want:
Int += error * dt * IntGain
2. I don't think we usually want Feed_Forward for positional control, and if we did, it wouldn't just be the last output. This implementation looks like another integration (it keeps adding the output to the last output). Feed Forward is where you have a predicted function of what input is needed to achieve the desired setting. The great thing about Feed Forward is that the rest of the PID algorithm only needs to account for the non-idealness of the prediction function and the other errors introduced in the system.