Articles written in Sadhana

    • A new design method for FIR notch filter using Fractional Derivative and swarm intelligence


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      In this paper, a new design method for the finite impulse response (FIR) notch filters using fractional derivative (FD) and swarm intelligence technique is presented. The design problem is constructed as a minimization of the magnitude response error w.r.t. filter coefficients. To acquire high accuracy of notch filter,fractional derivative (FD) is evaluated, and the required solution is computed using the Lagrange multiplier method. The fidelity parameters like passband error, notch bandwidth, and maximum passband ripple vary nonlinearly with respect to FD values. Moreover, the tuning of appropriate FD value is computationally expensive.Therefore, modern heuristic methods, known as the constraint factor particle swarm optimization (CFI-PSO), which is inspired by swarm intelligence, is exploited to search the best values of FDs and number of FD required for the optimal solution. After an exhaustive analysis, it is affirmed that the use of two FDs results in 21% reduction in passband error, while notch bandwidth is slightly increased by 2% only. Also, it has been observed that, in the proposed methodology, at the most 66 iterations are required for convergence to optimum solution. To examine the performance of designed notch filter using the proposed method, it has been applied for removal of power line interference from an electrocardiography (ECG) signal, and the improvement in performance isaffirmed.

    • Terminal adaptive control for a class of uncertain underactuated systems


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      This paper presents a backstepping-based terminal adaptive control solution for a class of uncertain underactuated systems with two degrees of freedom. The control scheme developed in this work is based on the finite time stability approach for the terminal convergence of system outputs. Due to the physical restrictionsassociated with underactuated systems, classical backstepping approach is not applicable to this class of nonlinear systems and hence an approximate version is developed by designing a suitable error surface. Control term is developed in two steps: first, non-singular pseudo-control terms are developed for the dimensions of the configuration space and thereafter a feasible control term is designed to ensure the finite time convergence of error surface. The error surface is designed such that its finite time convergence in turn implies the terminal convergence of configuration variables. To ensure a well-defined control term over the entire state space, control components are embedded with corrective terms. Corrective terms are designed so as to avoid the singularity of the control term and to preserve the desired controller response up to certain extent. A fuzzy logic system is usedfor the approximation of unknown systems dynamics. Simulation results demonstrate the effectiveness of the control approach.

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