I previously used the Ziegler method to tune the parameters of my PID controller to control my robot's position. I then implemented fuzzy logic for self-tuning the parameters. I have two inputs to the fuzzy logic controller; one is the position error and the error rate. I know that my problem might be due to not understanding the effect of each parameter very well. The problem is that I am confused in setting up the fuzzy rules. When do I need to use high and low values for Kp, Kd and Ki to achieve the best tuning? Is it that Kp must be very low when the error is almost zero (hence, the robot is at the desired position)? The same question applies for all of the three parameters.