Obaid Ur Rehman

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Wireless Sensor Networks (WSN) are becoming popular day by day, however one of the main issue in WSN is its limited resources. We have to look to the resources to create Message Authentication Code (MAC) keeping in mind the feasibility of technique used for the sensor network at hand. This research work investigates different cryptographic techniques such(More)
For a class of multi input and multi output nonlinear uncertain systems with input coupling term, a robust feedback linearization method combined with a minimax linear quadratic regulator (LQR) control is proposed. The uncertainties in the system and the presence of input terms in the low order derivatives of the outputs due to the input coupling makes the(More)
A new approach to designing a robust nonlinear controller for longitudinal flexible body models of canard configured airbreathing hypersonic flight vehicles with significant couplings and interactions is presented. The methodology uses a robust feedback linearization method to feedback linearize the nonlinear air-breathing hypersonic flight vehicle model(More)
This paper presents a design of an internal reference model based optimal linear quadratic Gaussian controller (LQG) for a piezoelectric tube (PZT) actuator used in the atomic force microscope (AFM). This control scheme minimizes the steady-state error and provides improved closed-loop bandwidth and enables the controller to track reference triangular(More)
This work presents a robust approach to estimate the continuously varying phase of an optical system. Here we extend the adaptive homodyne estimator scheme by using a nonlinear guaranteed cost robust filter in the feedback loop to improve the estimator performance. The nonlinear robust filter is designed by using a copy of the sector bounded nonlinear(More)
Precise tracking of a randomly varying optical phase is key to metrology, with applications in optical communication. Continuous phase estimation is known to be superior in accuracy as compared to static estimation. The underlying parameters in the model are, however, prone to changes owing to unavoidable external noises or apparatus imperfections. The(More)
This paper presents a systematic approach to the design of a robust dynamic state feedback controller using copies of the plant nonlinearities, which is based on the use of IQCs and minimax LQR control. The approach combines a linear state feedback guaranteed cost controller and copies of the plant nonlinearities to form a robust nonlinear controller.