A simple and optimal method is suggested for the calculation of the set point weighting parameter in PID controllers for unstable FOPTD systems. This method requires equating the coefficients of s and s3 both in numerator and denominator of closed loop transfer function for a servo problem. This method gives an uncomplicated equation for the set point weighting parameters (β) and (γ). The performance of the proposed set point weighted controller that uses the β and γ is then compared with that of a method in which the β and y values are obtained by two degrees of freedom controller design technique. The proposed method provides significantly improved closed loop performances when compared to the methods in the literature. © 2018

Manickam Chidambaram

Controllers

Degrees of freedom (mechanics)

Three term control systems

Time delay

CLOSED LOOP TRANSFER FUNCTION

Closed-loop performance

Delay systems

instrumentation

SET POINT WEIGHTING

SET POINT WEIGHTING PARAMETERS

TWO DEGREES OF FREEDOM CONTROLLERS

Unstable system

Process control

Fulltext

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IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

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IIT Madras

IFAC-PapersOnLine

Using the direct synthesis method, a proportional - integral - derivative (PID) controller in series with a lead-lag compensator is designed for control of the open-loop unstable second order plus time delay processes with/without a zero. Set-point weighting is considered for reducing the overshoot. The method has two tuning parameters, and guidelines are provided for selecting the two tuning parameters. The method gives significant improvement in load disturbance rejection performances. The designed controller is also robust for uncertainties in the process parameters. Illustrative examples are considered to show the performances of the proposed method. Significant improvement is obtained when compared to recently reported methods. © 2006 American Chemical Society.

Industrial and Engineering Chemistry Research

Enhanced two-degrees-of-freedom control strategy for second-order unstable processes with time delay

The methods proposed by Astrom and Hagglund for selection of set-point weighting parameters for stable systems are extended to unstable first-order plus time-delay (FOPTD) systems. Since these methods require the real part of the dominant pole, an analytical solution is derived for calculation of dominant poles of the closed-loop system given the PID controllers settings. For PID controller settings given by DePaor and O'Malley and Clement and Chidambaram, the set-point weighting parameters are calculated and simple equations are given for the parameters in terms of ε (ratio of time delay to dominant time constant). Simulation results on an unstable FOPTD transfer function model and higher-order transfer function model show that the overshoot is significantly reduced by employing the set-point weighting parameters in the PID controller. The performances of the closed-loop servo responses for all the extended methods are compared.

Journal of the Franklin Institute

Set-point weighted PID controllers for unstable systems

Journal of Process Control

Enhanced design of cascade control systems for unstable processes with time delay

Chemical Engineering Research and Design

IMC PID controller tuning for stable and unstable processes with time delay

Optimal H2 - IMC based PID Controller Design for Multivariable Unstable Processes

Simple method of calculating dynamic set-point weighting parameters for time delayed unstable processes

Journal	Data powered by TypesetIFAC-PapersOnLine
Publisher	Data powered by TypesetElsevier B.V.
ISSN	24058963
Open Access	Yes