K
I was reading VanDoren's TUNING FUNDAMENTALS Basics of Proportional-Integral-Derivative Control from Control Engineering Online http://www.controleng.com/archives/1998/ctl0301.98/03a305.htm I am in the middle of a big but friendly argument with a guy in Seattle about how PID works in a motor controller. assuming PID = Kp * err + Kd * (err - err[i-1]) Ki * (sum of err[n]for n = 0 to i) The fundamental difference we have is whether a voltage output (or PWM) is set directly by the PID or if the PID changes the existing voltage output. PWM = PID // His case or PWM = PWM[i-1] + PID // My case My argument is in the case of an aircraft heading the plant (the aircraft) continues flying in the heading with no outside influences. In the case of the motor, to be similar, the motor must continue the same speed until something outside influences it. My proof is when there is no error, the equations should default to: PWM = 0 // His case -- the motor stops? PWM = PWM[i-1] // My case -- it continues with the previous value Is the PID equation is used to adjust the output up or down, or does it produce the output value directly? Kip