15. The system of claim 13 , wherein the damped natural frequency and the damping ratio are calculated from a dynamic analysis of the closed-loop system step response.
13. A PID controller system for avoiding oscillatory behavior in a closed-loop process, the PID controller system comprising: a characteristic frequency estimator to identify an ultimate set of tuning parameters for the closed-loop process experiencing an oscillatory behavior response; a peak detector to calculate a damped natural frequency and a damping ratio from the oscillatory behavior response of the closed-loop process; a scaling module to receive the damped natural frequency and the damping ratio and to output a modified damped natural frequency and a modified damping ratio; a fuzzy inference system to receive the modified damped natural frequency and the modified damping ratio, to determine the degree of oscillation of the oscillatory behavior response and to determine the leading cause of the oscillatory behavior response and to output a change factor vector based on the oscillatory behavior response; and an accumulator to receive the change factor vector and to output a new set of tuning parameters for the closed-loop process.