A two-loop controller has been designed for a positive output elementary Luo (POEL) converter. An H ∞ controller is used in the outer loop using the loop-shaping concepts and a sliding mode control (SMC) in the inner loop for the regulation of the output voltage in spite of the perturbations in the line and load voltages. H ∞ controller generates the current reference for the converter inductor current, whereas SMC forces the converter inductor current to follow the reference. A practical design that combines the loop-shaping technique with SMC to enhance robustness and sliding performance is proposed. The closed-loop characteristics of a typical low-power POEL converter with the proposed controller implemented in the actual switched model is validated through computer simulations and experimental hardware. The proposed controller is found to be superior because of its low distortion property, good regulating performance and insensitivity to load variations.

Brushless DC (BLDC) motors are useful in applications such as process control, robotics, industrial automation, aerospace, electric vehicles etc. due to such advantages as the elimination of rotor losses and magnetizing current. Wider usage of BLDC motors demands optimum position control for high efficiency, accuracy and reliability. For an accurate position control, the estimation of moment of inertia and friction coefficient of the motor with load is essential. This paper incorporates the computation of the moment of inertia and friction coefficient of a BLDC motor with load at different load settings and emphasizes that load has an appreciable effect on the dynamic performance of the system. To obtain the optimum position control, a proportional plus integral plus derivative (PID) controller is employed and tuned using the PARR method. Artificial neural networks are used for computing the moment of inertia and friction coefficient of a BLDC motor with load and PID controller parameters at various load settings. Simulation results of the position control system are obtained at different load settings. From the results, it is evident that the PID controlled position control system responds to the desired position with minimum rise time, settling time and peak overshoot and is in dependent of load settings.

A state‐of‐the‐art review on various identification schemes proposed for the Hammerstein, Wiener, and Volterra systems is presented with respect to the special problems arising in the identification of unknown nonlinear systems. Past and recent developments in the field of nonlinear system identification, parameter estimation, and nonlinear control schemes along with the nonlinearity issues are also deeply investigated. A comprehensive analysis on various parameter estimation approaches and nonlinear control laws are made adding credit to the noteworthy contributions, constructive arguments, and remarkable breakthroughs of researchers in various research fields. The application of most popular nonlinear control strategies for many nonlinear systems in the existing literature are presented spotlighting their merits and major shortcomings. The challenges faced in the nonlinear control field and their emergences to future directions are projected.

Brushless DC (BLDC) Drive systems find immense applications in control systems. One such application is position control that requires very good stability limits, steady state and transient responses. Hence brushless dc drive systems should respond to meet these requirements. In this paper, few BLDC motor drive systems are considered. It is found that such systems cannot yield desired performance when conventional controller design procedure is employed. Hence, a modified design methodology for controller design of such systems is suggested. Simulation results of responses of BLDC drive systems are obtained for various desired specifications. Experimental results of responses of a BLDC drive system are obtained for various desired specifications using the proposed and conventional design methodologies to justify the simulation results. It is concluded that proposed design technique is more suitable for the controller design of such BLDC drive systems. Moreover, it can be understood that the controller design technique is non-iterative.

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