PHYTRA1: First International Conference on Physics and Technology of Reactors and Applications (Morocco), March 1416, 2 007, G MTR (2007) _________________________________ * Corresponding author, Tel. +92-51-9290231, Ext: 3219, Fax +92-51-9290275, E-mail: h_qaiser@yahoo.com Robust Control System Design for Pool Type Research Reactor using H ∞ Loop Shaping Technique S.H.Qaiser* 1 , A.I.Bhatti 1 , M.Iqbal 2 and M.T. Khaleeq 3 1 Center for Advance Studies in Engineering (CASE),G/5-1, Islamabad, Pakistan 2 Pakistan Institute Of Nuclear Science & Technology (PINSTECH), P.O. Nilore Islamabd, Pakistan 3 Informatics Complex for Computer and Control (ICCC), H/8-1, Islamabad, Pakistan Abstract A controller for regulating output power for Pakistan Research Reactor 1 (PARR-1) has been synthesized using H ∞ loop-shaping design technique. The model of the plant was determined experimentally by using system identification techniques. The model identification was performed by moving control rod in a chirp sequence and measuring the resulting output power signal from linear channel. After data acquisition, ARX and state space models were developed with this input and output data. Based on this model a robust controller was synthesized by using H ∞ loop-shaping technique. The performance of the controller is verified by comparing with PID and LQR controllers. H ∞ Loop shaping design showed best performance among all controllers in meeting performance specifications. The robustness of the controller was also verified by varying parameter values about 20% from the nominal value. The output of the H ∞ controller remains almost same, with much degradation in PID and LQR designs, thus proving its robustness against parameter variations. Key Words- H ∞ Loop shaping controller, system identification, robust control, nuclear research reactor, linear quadratic regulator (LQR), PID 1. Introduction Pakistan Research Reactor (PARR-1) is a 10 MW swimming pool type research reactor. In this reactor 19.99% enriched uranium fuel plates are used and control rods are made of alloy of cadmium (5%), silver (80%) and indium (15%). There are five control rods. The reactor becomes critical, when these rods are withdrawn about 56% from their fully inserted position. After reactor becomes critical, a single rod is used to regulate the reactor power [1]. A controller can be defined as robust if system dynamic performance and stability criteria are met while accounting for a specified range of uncertainties and disturbances. In other words a control system has a robust design when the effects of postulated uncertainties, modeling errors, and noise expected to be prevalent under normal operations are taken into account [2]. Robust controller design for nuclear research reactors has gained much popularity, due to the advantages gained by wide range of operation, more availability of the system and rejection of disturbances due to noise or model uncertainty. Much work has been carried out in this field, but no such type of controller existed for local research reactors [2, 3]. There was a need to design such controllers for modernizing the current system to avoid problems, which are becoming more and more due to aging of the system. As a first step a controller is synthesized by using H ∞ loop-shaping design. The designed system is simulated in Matlab ® and disturbance rejection capabilities are verified by a Simulink ® model. The analytical model was used for controller simulation, but for actual controller implementation, state space and ARX models were identified experimentally by using system identification techniques. The identified model will also be used in validating analytical model.