In this paper, the relay auto-tuning method is improved by modifying the Zeigler-Nichols method to obtain the improved value of the controller gains of a TITO unstable system. The effect of the higher order harmonic terms are also taken into consideration while designing the controllers. The proposed method is simulated on two 2×2 unstable transfer function matrices. The implementation of the method does not need the knowledge of the transfer function matrix. The performance of the proposed method is compared with the conventional method of relay tuning. The present method gives improved response and reduced interactions. The present method is also robust. © 2016 IEEE.

Manickam Chidambaram

Controllers

Decentralized control

Factory automation

Transfer functions

AUTO-TUNING METHODS

Autotuning

Controller gain

Conventional methods

DECENTRALIZED CONTROLLER

Higher order harmonics

TRANSFER FUNCTION MATRIX

TWO INPUT - TWO OUTPUTS

Transfer matrix method

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

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

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Improved relay auto-tuning method for unstable TITO systems

IEEE International Conference on Emerging Technologies and Factory Automation, ETFA

In the present work, an improved continuous cycling method is proposed for tuning proportional-integral-derivative (PID) controllers for unstable systems. The method involves the determination of the controller settings by solving the magnitude criterion and the phase angle criterion for the system. Subsequently, incorporating the transfer function of the PID controller, with unity proportional gain, with the system model and again solving the amplitude and the phase angle criteria to get the updated gain of the controller. The proposed method is applied by simulation on (i) a second-order system with one unstable pole and (ii) a nonlinear model of a bioreactor. The method is also extended for the relay tuning method to automate the improved continuous cycling method. The controller settings significantly enhance the performances (integral time absolute error) of both the servo and the regulatory problems and also give a robust performance. The present method is compared with the reported methods based on the ultimate cycle and with the method proposed by Jeng and Fu [“Closed Loop Tuning of Set Point Weighted Proportional-Integral-Derivative Controllers for Stable, Integrating and Unstable Processes: A Unified Data Based Method”, Ind. Eng. Chem. Res., 54, pp. 1041–1058 (2015)]. © 2016, © 2016 Indian Institute of Chemical Engineers.

Indian Chemical Engineer

Improved Continuous Cycling Method of Tuning PID Controllers for Unstable Systems

A method is presented to identify the steady-state gain matrix of a multivariable (SSGM) unstable system under closed-loop control. Effects of disturbances and measurement noise on the identification of SSGM were also studied. Davison's method (Davison, 1976) was modified to design single-stage multivariable PI controllers using only the steady-state gain matrix of the system. Since the overshoots in the responses are larger, a two-stage P-PI control system is proposed. Based on the SSGM, a simple proportional controller matrix was designed by the modified Davison's method (1976) to stabilize the system. Based on the gain matrix of the stabilized system, diagonal PI controllers were designed. The performance of the two-stage control system was evaluated and compared with that of single-stage multivariable controllers. Simulation results on two examples show the effectiveness of the proposed methods for both servo and regulatory problems. © 2015, Taylor & Francis Group, LLC.

Chemical Engineering Communications

Steady-State Gain Identification and Control of Multivariable Unstable Systems

A method is proposed based on the equivalent transfer function (ETF) model to design multivariable proportional integral (PI) controllers for unstable multivariable systems with delay. The simplified decoupler decomposes the unstable multiloop systems into independent loops with ETFs as the resultant decoupled process model having unstable poles. PI controllers are designed for the diagonal elements of ETFs by the synthesis method meant for unstable first order plus time delay (FOPTD) systems. Since the overshoot is higher for the unstable systems, a double-loop control structure (inner-loop diagonal proportional (P) controllers with the decoupler and outer loop only with diagonal PI controllers) is proposed to get a reduced overshoot. Two examples of two input two output (TITO) unstable systems are considered to demonstrate the simplicity and effectiveness of the proposed method. © 2014 American Chemical Society.

Industrial and Engineering Chemistry Research

Design of proportional integral controllers with decouplers for unstable two input two output systems

Relay Auto Tuning of Decentralized PID Controllers for Unstable TITO Systems

International Journal of Control, Automation and Systems

Equivalent transfer function based multi-loop PI control for high dimensional multivariable systems

Journal	Data powered by TypesetIEEE International Conference on Emerging Technologies and Factory Automation, ETFA
Publisher	Data powered by TypesetInstitute of Electrical and Electronics Engineers Inc.
ISSN	19460740
Open Access	No