Publication Date

Fall 2013

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical Engineering

Advisor

Peter Reischl

Keywords

Controls

Subject Areas

Electrical engineering

Abstract

This research yielded a real-time auto tuning algorithm to adaptively tune a proportional integral and derivative (PID) controller for a first or second-order system with internal time-delay. The method uses a 15-bit pseudo-random binary sequence as an input to obtain the closed-loop system impulse response while the system is operating. Time-delay is assessed by analysis of the estimated closed-loop impulse response and is used in the system model for closed-loop pole assessment. The fast fourier transform of the estimated impulse response produces an estimate of the frequency response data, and a non-linear regression optimization technique, utilizing MATLAB, identifies the closed-loop system transfer function based on assumed form. Closed-loop poles are then placed, based on an iterative tuning study, automatically by the algorithm to achieve a user-defined overshoot and ensure stability of the system with time-delay. This is accomplished by adjusting the PID compensator gains. The algorithm is capable of tuning the system from an initially stable set of PID gains to within 5% of the user-defined overshoot. The research demonstrates that the auto tuning method is feasible for time-delays on the order of the plant time constant but is extendable to larger time-delays.

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