Patent Document ID: 7809668
Application ID: 11943720

Base Claim:
1. A method of avoiding oscillatory behavior in a PID controller in a closed-loop process, the method comprising the steps of: identifying an ultimate set of tuning parameters for the closed-loop process; observing an oscillatory behavior response in the closed-loop process; identifying a damped natural frequency from the oscillatory behavior response; identifying a damping ratio from the oscillatory behavior response; calculating a modified damped natural frequency from the damped natural frequency; calculating a modified damping ratio from the damping ratio; determining the degree of oscillation of the oscillatory behavior response and determining the leading cause of the oscillatory behavior response from the calculated modified damped natural frequency and the calculated modified damping ratio of the oscillatory behavior response; and adjusting the ultimate set of tuning parameters of the closed-loop process based upon the degree oscillation of the oscillatory behavior response the leading cause of the oscillatory behavior response, thereby avoiding oscillatory behavior in the PID controller.

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Claim 2:
2. The method of claim 1 , wherein the step of identifying an ultimate set of tuning parameters for the closed-loop process further comprises: calculating an ultimate process gain and a corresponding ultimate frequency for the ultimate process gain of the closed-loop process; calculating an ultimate process time constant and a corresponding ultimate frequency for the ultimate process time constant of the closed-loop process; and calculating an ultimate process dead time and a corresponding ultimate frequency for the ultimate process dead time of the closed-loop process.