The Modares Journal of Electrical Engineering
Volume:12 Issue: 1, 2012

Non-fragile observer design is the main problem of this paper. Using continuous frequency distribution، the stability conditions based on integer order Lyapunov theorem are derived for Lipschitz class of nonlinear fractional order systems. The proposed observer is stable beside the existence of both gain perturbation and input disturbance. For the first time، in this paper a systematic method is suggested based on linear matrix inequality to find an optimal observer gain to minimize both the effects of disturbance on the synchronization error and norm of the observer gain. A comparison has done between this observer and previous research on resilient observer design for nonlinear fractional order systems based on fractional order Lyapunov method. The comparison shows a much broader range of feasible response for the proposed method of this paper besides simpler computing. After presenting thediscussion، chaos synchronization is simulated to show the effectiveness of the proposed method in the end.

Surge and rotating stall phenomena are two dynamic instabilities that occur in both axial and centrifugal compressors. Surge is the stream instability phenomenon in compressor that imposes severe damages to the compressors. Nowadays، suppressing surge phenomenon is one of the most important issues in oil and gas industries، especially when flow reduction or gas reflux is considered. This research seeks to extract the required technical information about control lines، surge lines، and to present a new combined method to determine the performance curve of 6 rows of gas compressors in Asmari Kupal gas pressure boost station (National Iranian South Oil Company) made in Germany by MAN BORSIG Company، and to design a smart controller in order to increase the reliability of the control system and improve the machine performance. Finally، the system performance validity is shown by simulating a surge characteristic curve and implementing two points of the compressor operation condition

Monitoring is an essential and inseparable tool for every industrial automation system. In advanced monitoring، in addition to representation of the process conditions، fast identification and removing of the faults in different critical parts of the system is indispensable. Distributed Control Systems (DCS) are an integral part of the current automation systems and hence، advanced monitoring techniques need to be effectively adapted and implemented in these control systems. This paper presents a novel method for implementation of the advanced online monitoring on the PCS7. Model of the gas station is first developed. The effectiveness of the model is evaluated using the model data of a real gas pressure reduction station under various operating conditions. Advanced monitoring is then implemented for this station. The real-life results demonstrates that the presented method can effectively detect the system faults.

In this paper، stabilization conditions and controller design for a class of nonlinear systems are proposed. The proposed method is based on the nonlinear feedback، quadratic Lyapunov function and heuristic slack matrices definition. These slack matrices in null products are derived using the properties of the system dynamics. Based on the Lyapunov stability theorem and Sum of Squares (SOS) decomposition techniques، the conditions are derived in terms of SOS. This approach has two main advantages. First، using the polynomial model، the proposed method uses the polynomial state space matrices in the model description. Therefore، it does not need any existing modeling methods such as the Takagi Sugeno (T-S) fuzzy model which can be a source of conservativeness in the control design conditions، because the membership function information cannot be used completely in the derivation of the controller design conditions. Second، using slack matrices، one can find the matrices that leads to applicable controller design which this means it provides extra degrees of freedom. To show the effectiveness of the proposed method، a PMSM is considered in the numerical simulation.

In this paper، an optimal adaptive fuzzy integral sliding mode control is presented to control the robot manipulator position tracking in the presence of uncertainties and permanent magnet DC motor. In the proposed control، sliding surface of the sliding mode control is defined according to the information of position tracking error، derivatives، and error integral. In order to estimate bounds of the existing structured and unstructured uncertainties in the dynamics of the robot manipulator and the permanent magnet DC motor، a MIMO fuzzy adaptive approximator is designed. This helps to overcome the undesired chattering phenomenon in the control input by using fuzzy logic. Mathematical proof shows that the closed-loop system with the adaptive fuzzy integral sliding mode control in the presence of all the uncertainties has the global asymptotic stability. Furthermore، modified harmony search optimization algorithm is used to define the input coefficients of the proposed control and also to reduce the control input amplitude. In order to validate performance of the proposed controller، a case study on the SCARA robot manipulator is conducted in the presence of permanent magnet DC motor. Results of the Simulation show desired performance of the proposed controller.

Surge is one of the two destructive factors in compressors. surge is the stream instability phenomenon in compressor that imposes severe damages to the compressors. Nowadays، suppressingsurge phenomenon is one of the most important issues in oil and gas industries، especially when flow reduction or gas reflux is considered. According to Moore-Greitzer compressor model، this paper designs an active controller for surge control in constant speed centrifugal compressors. As such، the applied operator considered for surge control is Close Couple Valve (CCV) and it is designed to stabilize a centrifugal compressor system with disturbaces using nonlinear predictive controller. The proposed controller، without any information about the amount of Throttle Valve variations، could control the surge instability and reduce the distance between compressor operation point and the surge line. Finally، the compressor system with controller is simulated and the obtained results will show the efficiency of the designed nonlinear predictive controller