Application of numerical technique in tangent analysis of a discrete step response data

Tangent analysis is the conventional method used to analyze an open-loop step response curve. It is done by drawing a tangent line at the steepest point of the step response curve. The process dynamics such as dead time and response rate can be obtained from the analysis. Later, this information is applied to the open-loop tuning rule for optimum PID calculation. With current developments in paperless recorders and digital computer control, the step response curve is available in discretized form. Accordingly, the process dynamics of the discrete step response can be analyzed numerically. It is, therefore, the intention of this paper to present the application of numerical analysis in extracting the process dynamics from discrete step response data.