{ This paper shows the application of fuzzy logic based duty ratio control technique to reduce torque ripple in an induction motor employing Direct Torque Control (DTC). This technique increases the number of voltage vectors beyond the available eight discrete voltage vectors without any increase in the number of semiconductor switches in the inverter. In addition, this work incorporates Model Reference Adaptive System based observer to estimate rotor speed. Look-up table based on-line tuning PI controller is proposed for outer speed control loop to achieve swift response, less overshooting and precision speed control to have wide torque-speed characteristics. A new algorithm for optimized value of stator flux based on the maximum reference value of electromagnetic torque is proposed to operate in conjunction with duty ratio control. The performance of the proposed drive system is evaluated through digital simulation using MATLAB-SIMULINK package. The simulation results clearly depict the superiority of devised method over the existing methods of DTC },

{During our studies of the techniques of conception (design) and modelling of linear and nonlinear microwave circuits, we noticed the big need to a method able to improve the analysis and the understanding of circuits, which often function in high frequency. Therefore, we propose, in this paper, a new methodology to study a microwave filter with localized elements (Chebychev low-pass filter) by a joint application of the bond graph approach and the scattering formalism. This study consists of, on the one hand, determining and simulating the scattering parameters of this filter and on the other hand, to modeling the incident and reflected wave propagation since the source towards the load through this filter. In fact, the modelling of these various wave propagation amounts modelling the scattering matrix constituted by the scattering parameters of the studied filter on a particular type of bond graph model often named: “Scattering Bond Graph”},

{This paper presents a detailed analysis of the switching loss characteristics of various existing discontinuous PWM (DPWM) algorithms, which use only one zero state and advanced DPWM (ADPWM) algorithms which use only one zero state with active state division. These DPWM algorithms reduce the switching losses at any operating conditions when compared with conventional space vector PWM (CSVPWM). Moreover, to reduce the complexity involved in the conventional space vector approach, the proposed PWM algorithms are developed by using the concept of imaginary switching times. By analyzing the switching loss characteristics, the minimum switching loss PWM algorithms are developed for induction motor drives. The theoretical evaluation is validated through the numerical simulation studies},

{ In this paper, we present an adaptive fuzzy control for a class of unknown nonlinear systems. The strategy of control uses the adaptive fuzzy system Takagi-Sugeno (T-S) to approximate the part of the primary control. In order to guarantee the stability and high performance, the auxiliary part is incorporated in the control law. The proposed compensation control is combined a Hermite function and sliding mode control (SMC). The Hermite function is used to predict and to remove the fuzzy approximation and attenuates the influence of the external disturbances. However, the SMC is designed to ensure the stability and a good tracking. The parameters of the control are adjusted on line by the adaptive law with stability and convergence analysis using the Lyapunov approach. The robust and the stability of the control scheme are proved and simulation results are given to verify the effectiveness of the proposed approach},