Chitralekha Mahanta

A novel approach for ANFIS modelling based on full factorial design

Adaptive neural network based fuzzy inference system (ANFIS) is an intelligent neuro-fuzzy technique used for modelling and control of ill-defined and uncertain systems. ANFIS is based on the input-output data pairs of the system under consideration. The size of the input-output data set is very crucial when the data available is very less and the generation of data is a costly affair. Under such circumstances, optimization in the number of data used for learning is of prime concern. In this paper, we have proposed an ANFIS based system modelling where the number of data pairs employed for training is minimized by application of an engineering statistical technique called full factorial design. Our proposed method is experimentally validated by applying it to the benchmark Box and Jenkins gas furnace data and a data set collected from a thermal power plant of the North Eastern Electric Power Corporation (NEEPCO) Limited. By employing our proposed method the number of data required for learning in the ANFIS network could be significantly reduced and thereby computation time as well as computation complexity is remarkably reduced. The results obtained by applying our proposed method are compared with those obtained by using conventional ANFIS network. It was found that our model compares favourably well with conventional ANFIS model.

Adaptive second order terminal sliding mode controller for robotic manipulators

Abstract In this paper an adaptive second order terminal sliding mode (SOTSM) controller is proposed for controlling robotic manipulators. Instead of the normal control input, its time derivative is used in the proposed controller. The discontinuous sign function is contained in the derivative control and the actual control obtained after integration is continuous and hence chatterless. An adaptive tuning method is utilized to deal with the system uncertainties whose upper bounds are not required to be known in advance. The performance of the proposed control strategy is evaluated through the control of a two-link rigid robotic manipulator. Simulation results demonstrate the effectiveness of the proposed control method.

Integral backstepping sliding mode control for underactuated systems: swing-up and stabilization of the Cart-Pendulum System.

In this paper an integral backstepping sliding mode controller is proposed for controlling underactuated systems. A feedback control law is designed based on backstepping algorithm and a sliding surface is introduced in the final stage of the algorithm. The backstepping algorithm makes the controller immune to matched and mismatched uncertainties and the sliding mode control provides robustness. The proposed controller ensures asymptotic stability. The effectiveness of the proposed controller is compared against a coupled sliding mode controller for swing-up and stabilization of the Cart-Pendulum System. Simulation results show that the proposed integral backstepping sliding mode controller is able to reject both matched and mismatched uncertainties with a chattering free control law, while utilizing less control effort than the sliding mode controller.

Chattering free adaptive multivariable sliding mode controller for systems with matched and mismatched uncertainty.

In this paper, a chattering free adaptive sliding mode controller (SMC) is proposed for stabilizing a class of multi-input multi-output (MIMO) systems affected by both matched and mismatched types of uncertainties. The proposed controller uses a proportional plus integral sliding surface whose gain is adaptively tuned to prevent overestimation. A vertical take-off and landing (VTOL) aircraft system is simulated to demonstrate the effectiveness of the proposed control scheme.

A fast converging robust controller using adaptive second order sliding mode.

This paper proposes an adaptive second order sliding mode (SOSM) controller with a nonlinear sliding surface. The nonlinear sliding surface consists of a gain matrix having a variable damping ratio. Initially the sliding surface uses a low value of damping ratio to get a quick system response. As the closed loop system approaches the desired reference, the value of the damping ratio gets increased with an aim to reducing the overshoot and the settling time. The time derivative of the control signal is used to design the controller. The actual control input obtained by integrating the derivative control signal is smooth and chattering free. The adaptive tuning law used by the proposed controller eliminates the need of prior knowledge about the upper bound of system uncertainties. Simulation results demonstrate the effectiveness of the proposed control strategy.

Identification of uncertain nonlinear systems for robust fuzzy control.

In this paper, we consider fuzzy identification of uncertain nonlinear systems in Takagi-Sugeno (T-S) form for the purpose of robust fuzzy control design. The uncertain nonlinear system is represented using a fuzzy function having constant matrices and time varying uncertain matrices that describe the nominal model and the uncertainty in the nonlinear system respectively. The suggested method is based on linear programming approach and it comprises the identification of the nominal model and the bounds of the uncertain matrices and then expressing the uncertain matrices into uncertain norm bounded matrices accompanied by constant matrices. It has been observed that our method yields less conservative results than the other existing method proposed by Skrjanc et al. (2005). With the obtained fuzzy model, we showed the robust stability condition which provides a basis for different robust fuzzy control design. Finally, different simulation examples are presented for identification and control of uncertain nonlinear systems to illustrate the utility of our proposed identification method for robust fuzzy control.

Optimal second order sliding mode control for nonlinear uncertain systems.

In this paper, a chattering free optimal second order sliding mode control (OSOSMC) method is proposed to stabilize nonlinear systems affected by uncertainties. The nonlinear optimal control strategy is based on the control Lyapunov function (CLF). For ensuring robustness of the optimal controller in the presence of parametric uncertainty and external disturbances, a sliding mode control scheme is realized by combining an integral and a terminal sliding surface. The resulting second order sliding mode can effectively reduce chattering in the control input. Simulation results confirm the supremacy of the proposed optimal second order sliding mode control over some existing sliding mode controllers in controlling nonlinear systems affected by uncertainty.

Combined online and offline assamese handwritten numeral recognizer

This work describes the development of an Assamese handwritten numeral recognizer. Online handwritten numeral recognition system is developed using x, y coordinates as the feature and Hidden Markov Model (HMM) as the modelling technique. Offline handwritten numeral recognition system is developed using vertical projection profile and horizontal projection profile (VPP-HPP), zonal discrete cosine transform (DCT), chain code histogram (CCH) and pixel level information as features and vector quantization (VQ) as the modelling technique. The confusion patterns of online and offline systems are analysed. Based on this, the two systems are further combined to obtain a final numeral recognition system. The combined system exhibits improved performance over the individual approaches, demonstrating the significance of different natures of information present in each mode.

Adaptive backstepping control for DC-DC buck converters using Chebyshev neural network

This paper proposes a novel control technique for the Buck type DC-DC converters using adaptive backstepping control and Chebyshev neural network. To enhance the transient performance of both the capacitor voltage and the inductor current under nominal conditions, input voltage fluctuations and load variations, this control algorithm has been proposed. The systematic design of backstepping controller has been improvised by incorporating the approximation of unknown load resistance parameter by a single layer Chebyshev neural network. Results have been compared with a recently developed adaptive terminal sliding mode control technique. The proposed method significantly improves voltage and current transient performances.

Assamese online handwritten digit recognition system using hidden Markov models

This work describes the development of Assamese online handwritten digit recognition system. Assamese numerals are the same as the Bangla numerals. A large database of handwritten numerals is collected and partitioned into two parts of equal size. The first part is used for developing the Hidden Markov Models (HMM) based digit models. The (x, y) coordinates and their first and second time derivatives are used as features. The second part of the database is tested against the models to evaluate the performance. The digit recognition system provides an average recognition performance of 96.02%. A large amount of confusion is observed among the numerals 5 & 6. The new distance feature is used as an additional feature and the models are retrained. The performance for numeral 5 & 6 increases from 91.60% & 95.40% to 95.30% & 94.90%. As a result, the confusion reduces significantly and the average recognition performance increases to 97.14%.