This document expands upon the work done by Dave Wilson of Texas Instruments in the Teaching Your PI Controller to Behave series of articles. Dave Wilson’s work reduces the PI coefficients for a Cascade Proportional Integral (PI) Controller to a single parameter which I will refer to as Span (Dave referred to this as the damping factor, δ). The technique is used to maximize the phase margin for a given closed loop system.
My effort is to show how one can improve a control system’s setpoint and disturbance response, by employing a Limited Span Method (LSM).
The Method proposed herein, uses a relationship between the prefiltered velocity loop bandwidth (ω3dBf) and span, χ but in a limited span range (2 <= χ < 2.95).