Showing papers by "Shantanu Das published in 2012"

Improved model reduction and tuning of fractional-order PIλDμ controllers for analytical rule extraction with genetic programming

Abstract: Genetic algorithm (GA) has been used in this study for a new approach of suboptimal model reduction in the Nyquist plane and optimal time domain tuning of proportional–integral–derivative (PID) and fractional-order (FO) P I λ D μ controllers. Simulation studies show that the new Nyquist-based model reduction technique outperforms the conventional H2-norm-based reduced parameter modeling technique. With the tuned controller parameters and reduced-order model parameter dataset, optimum tuning rules have been developed with a test-bench of higher-order processes via genetic programming (GP). The GP performs a symbolic regression on the reduced process parameters to evolve a tuning rule which provides the best analytical expression to map the data. The tuning rules are developed for a minimum time domain integral performance index described by a weighted sum of error index and controller effort. From the reported Pareto optimal front of the GP-based optimal rule extraction technique, a trade-off can be made between the complexity of the tuning formulae and the control performance. The efficacy of the single-gene and multi-gene GP-based tuning rules has been compared with the original GA-based control performance for the PID and P I λ D μ controllers, handling four different classes of representative higher-order processes. These rules are very useful for process control engineers, as they inherit the power of the GA-based tuning methodology, but can be easily calculated without the requirement for running the computationally intensive GA every time. Three-dimensional plots of the required variation in PID/fractional-order PID (FOPID) controller parameters with reduced process parameters have been shown as a guideline for the operator. Parametric robustness of the reported GP-based tuning rules has also been shown with credible simulation examples.

Fractional Order Modeling of a PHWR Under Step-Back Condition and Control of Its Global Power with a Robust PI{\lambda}D{\mu} Controller

Abstract: Bulk reduction of reactor power within a small finite time interval under abnormal conditions is referred to as step-back. In this paper, a 500MWe Canadian Deuterium Uranium (CANDU) type Pressurized Heavy Water Reactor (PHWR) is modeled using few variants of Least Square Estimator (LSE) from practical test data under a control rod drop scenario in order to design a control system to achieve a dead-beat response during a stepped reduction of its global power. A new fractional order (FO) model reduction technique is attempted which increases the parametric robustness of the control loop due to lesser modeling error and ensures iso-damped closed loop response with a PI{\lambda}D{\mu} or FOPID controller. Such a controller can, therefore, be used to achieve active step-back under varying load conditions for which the system dynamics change significantly. For closed loop active control of the reduced FO reactor models, the PI{\lambda}D{\mu} controller is shown to perform better than the classical integer order PID controllers and present operating Reactor Regulating System (RRS) due to its robustness against shift in system parameters.

Joining of Mild Steel Plates Using Microwave Energy

Abstract: This paper describes joining of bulk MS (mild steel) plates using a domestic microwave oven at a frequency of 2.45 GHz and a power of 900 W. Microwave Hybrid Heating (MHH) is used for joining of MS plate by placing an interlayer of Ni powder of average thickness of about 0.3 mm between two interfacing surfaces. Characterization of the joints has been carried out using X ray diffraction (XRD), SEM (Scanning Electron Microscope), and Vickers micro indentation. The back scattered electron (BSE) image shows complete melting of powder particle yielding diffusion bonding between interfacing powder particles and MS plates The average micro hardness of the joints observed to be 420 ± 30 Hv which is significantly higher than the substrate hardness of 230 ± 10 Hv. The results obtained after performing tensile test show that the joints have an average strength of 250 MPa with a percentage elongation of 6 percent

Master-slave chaos synchronization via optimal fractional order PI λ D μ controller with bacterial foraging algorithm

Abstract: Chaos synchronization in a master-slave configuration has been studied in this paper with a fractional order (FO) Proportional-Integral-Derivative (PID) controller using an intelligent Bacterial Foraging Optimization (BFO) algorithm. A comparative study has been made to highlight the advantage of using a fractional order PI λ D μ controller over the conventional PID controller for chaos synchronization using two Lu systems as a representative example. Simulation results are presented to show the effectiveness of the proposed chaos synchronization technique over the existing methodologies.

Microwave Drilling of Materials

Abstract: This is proof of principle of application of ‘near-field microwave radiation’, for material drilling. We report result of experiments conducted, for microwave-drilling of materials, using two types of setups, one-inside a domestic microwave oven and second -via co-axial cable applicator. Drilling with these techniques were carried out for wood, glass, aluminium, copper, mild-steel (MS), animal bones specimens.

Impact of fractional order integral performance indices in LQR based PID controller design via optimum selection of weighting matrices

Abstract: A continuous and discrete time Linear Quadratic Regulator (LQR) based technique has been used in this paper for the design of optimal analog and discrete PID controllers respectively. The PID controller gains are selected as the optimal state-feedback gains corresponding to the standard quadratic cost function. Genetic Algorithm (GA) has been used next to optimally find out the weighting matrices, associated with the respective optimal state-feedback regulator designs while minimizing another integral performance index which comprises of a weighted sum of Integral of Time multiplied Squared Error (ITSE) and the controller effort. Next, the proposed methodology is applied with fractional order (FO) integral performance indices. The impact of these FO objective functions on the LQR tuned PID control loops is also highlighted, along with the achievable cost of control.

Theory of welding of metallic parts in microwave cavity applicator

Abstract: We have been successfully welding bulk metals and dissimilar metals by microwave radiation, by using metal powder particles in the weld zone. In this paper, we have tried to explain the insight of electromagnetic field penetration into spherical conductive powder particles and its spatial oscillatory distribution. This new developed theoretical explanation here, gives insight as to how the entire weld zone volume becomes heat source; via absorption of microwave radiation, and thus this process of welding with microwave radiation, is with inertia less heat transfer, volumetric heating with inverted temperature profile.

Design of a Fractional Order Phase Shaper for Iso-damped Control of a PHWR under Step-back Condition

Abstract: Phase shaping using fractional order (FO) phase shapers has been proposed by many contemporary researchers as a means of producing systems with iso-damped closed loop response due to a stepped variation in input. Such systems, with the closed loop damping remaining invariant to gain changes can be used to produce dead-beat step response with only rise time varying with gain. This technique is used to achieve an active step-back in a Pressurized Heavy Water Reactor (PHWR) where it is desired to change the reactor power to a pre-determined value within a short interval keeping the power undershoot as low as possible. This paper puts forward an approach as an alternative for the present day practice of a passive step-back mechanism where the control rods are allowed to drop during a step-back action by gravity, with release of electromagnetic clutches. The reactor under a step-back condition is identified as a system using practical test data and a suitable Proportional plus Integral plus Derivative (PID) controller is designed for it. Then the combined plant is augmented with a phase shaper to achieve a dead-beat response in terms of power drop. The fact that the identified static gain of the system depends on the initial power level at which a step-back is initiated, makes this application particularly suited for using a FO phase shaper. In this paper, a model of a nuclear reactor is developed for a control rod drop scenario involving rapid power reduction in a 500MWe Canadian Deuterium Uranium (CANDU) reactor using AutoRegressive Exogenous (ARX) algorithm. The system identification and reduced order modeling are developed from practical test data. For closed loop active control of the identified reactor model, the fractional order phase shaper along with a PID controller is shown to perform better than the present Reactor Regulating System (RRS) due to its iso-damped nature.

Artificial neural network based prediction of optimal pseudo-damping and meta-damping in oscillatory fractional order dynamical systems

Abstract: This paper investigates typical behaviors like damped oscillations in fractional order (FO) dynamical systems. Such response occurs due to the presence of, what is conceived as, pseudo-damping and meta-damping in some special class of FO systems. Here, approximation of such damped oscillation in FO systems with the conventional notion of integer order damping and time constant has been carried out using Genetic Algorithm (GA). Next, a multilayer feed-forward Artificial Neural Network (ANN) has been trained using the GA based results to predict the optimal pseudo and meta-damping from knowledge of the maximum order or number of terms in the FO dynamical system.

Artificial Neural Network Based Prediction of Optimal Pseudo-Damping and Meta-Damping in Oscillatory Fractional Order Dynamical Systems

Abstract: This paper investigates typical behaviors like damped oscillations in fractional order (FO) dynamical systems. Such response occurs due to the presence of, what is conceived as, pseudo-damping and meta-damping in some special class of FO systems. Here, approximation of such damped oscillation in FO systems with the conventional notion of integer order damping and time constant has been carried out using Genetic Algorithm (GA). Next, a multilayer feed-forward Artificial Neural Network (ANN) has been trained using the GA based results to predict the optimal pseudo and meta-damping from knowledge of the maximum order or number of terms in the FO dynamical system.

Genetic Algorithm Based Improved Sub-Optimal Model Reduction in Nyquist Plane for Optimal Tuning Rule Extraction of PID and PI{\lambda}D{\mu} Controllers via Genetic Programming

Abstract: Genetic Algorithm (GA) has been used in this paper for a new Nyquist based sub-optimal model reduction and optimal time domain tuning of PID and fractional order (FO) PI{\lambda}D{\mu} controllers. Comparative studies show that the new model reduction technique outperforms the conventional H2-norm based reduced order modeling techniques. Optimum tuning rule has been developed next with a test-bench of higher order processes via Genetic Programming (GP) with minimum value of weighted integral error index and control signal. From the Pareto optimal front which is a trade-off between the complexity of the formulae and control performance, an efficient set of tuning rules has been generated for time domain optimal PID and PI{\lambda}D{\mu} controllers.

Optimizing Continued Fraction Expansion Based IIR Realization of Fractional Order Differ-Integrators with Genetic Algorithm

Abstract: Rational approximation of fractional order (FO) differ-integrators via Continued Fraction Expansion (CFE) is a well known technique. In this paper, the nominal structures of various generating functions are optimized using Genetic Algorithm (GA) to minimize the deviation in magnitude and phase response between the original FO element and the rationalized discrete time filter in Infinite Impulse Response (IIR) structure. The optimized filter based realizations show better approximation of the FO elements in comparison with the existing methods and is demonstrated by the frequency response of the IIR filters.

Realization of fractional order differintegrals

Abstract: This paper presents a new and a simple approach to realize a two port network, having transfer function to approximate a fractional order differintegrals (s±α, where, −1< α < 1). In this paper, cascade network connection of the finite number of basic two port network each consisting of an operational amplifier, a capacitor and a resistor is implemented. This is to realize the poles-zeros placement alternately along the negative real axis of s-plain i.e interlacing of poles and zeros. This realizes the fractional order transfer function over a specified bandwidth. Its bode phase plot could be maintained constant over the specified frequency range. The underlying theory is discussed and the design procedure is developed here.

Estimation, Analysis and Smoothing of Self-Similar Network Induced Delays in Feedback Control of Nuclear Reactors

Abstract: This paper analyzes a nuclear reactor power signal that suffers from network induced random delays in the shared data network while being fed-back to the Reactor Regulating System (RRS). A detailed study is carried out to investigate the self similarity of random delay dynamics due to the network traffic in shared medium. The fractionality or selfsimilarity in the network induced delay that corrupts the measured power signal coming from Self Powered Neutron Detectors (SPND) is estimated and analyzed. As any fractional order randomness is intrinsically different from conventional Gaussian kind of randomness, these delay dynamics need to be handled efficiently, before reaching the controller within the RRS. An attempt has been made to minimize the effect of the randomness in the reactor power transient data with few classes of smoothing filters. The performance measure of the smoothers with fractional order noise consideration is also investigated into.