Abstract A material undergoes progressive damage that creates micro-cracks and induces its breaking. To determine its life time, very costly experimental trials are achieved. To overcome this problem, different strategies have been developed using experimental results. These strategies have given different models that predict the mechanical behavior of materials with few and low costs tests. Most of the existing methods for... A material undergoes progressive damage that creates micro-cracks and induces its breaking. To determine its life time, very costly experimental trials are achieved. To overcome this problem, different strategies have been developed using experimental results. These strategies have given different models that predict the mechanical behavior of materials with few and low costs tests. Most of the existing methods for modelling the fatigue of a material have focused on the estimation of the coefficient of fatigue strength σ f and on the coefficient of ductility in fatigue εf . In this work, we study the performance of a dozen of methods proposed in the literature to estimate these coefficients and to predict the life time of the material. We have determined the errors committed in the theoretical models in relation to experimental data. To this end, we have compared the results obtained by these methods with the experimental results on a basis of 82 steels. We have established a protocol to compare the results, which consists in computing the error committed by each model on the estimation of the coefficients of fatigue. The analyses of the results have shown that none of the models can estimate correctly both of the coefficients. We then identified two models that estimate accurately both coefficients σ'f and ε'f separately. Read More Read Less

Abstract This paper proposes a method for designing a sensor less induction motor drive based on a robust rotor flux observer. The industrial world demands reliable and inexpensive systems. For this reason, the number of sensors is reduced. Accordingly, this study will focus on the design of a robust rotor flux observer using both the Lyapunov theory and the linear matrix... This paper proposes a method for designing a sensor less induction motor drive based on a robust rotor flux observer. The industrial world demands reliable and inexpensive systems. For this reason, the number of sensors is reduced. Accordingly, this study will focus on the design of a robust rotor flux observer using both the Lyapunov theory and the linear matrix inequality (LMIs). Thus, the development of an estimator of the rotor speed. The proposed solution always results in a stable and robust controller against variations of resistances. The solution is evaluated by simulation. Read More Read Less

Abstract This paper presents the backstepping nonlinear control of an induction motor. This control is based on the stability of the system from the Lyapunov theory with taking account the nonlinearity of our system. To validate the effectiveness and robustness of the proposed solution some simulation results are provided.... This paper presents the backstepping nonlinear control of an induction motor. This control is based on the stability of the system from the Lyapunov theory with taking account the nonlinearity of our system. To validate the effectiveness and robustness of the proposed solution some simulation results are provided. Read More Read Less

Abstract Actually, in the majority of mechanical systems such as industrial robots, mobile robots with embarked structure, etc… the end-effector mass widely exceeds that of the supported load, and lot of works do not take it into account in their algorithms. These systems must be designed based on dynamic model; moreover the synthesis of the algorithm of an autonomous manipulator must... Actually, in the majority of mechanical systems such as industrial robots, mobile robots with embarked structure, etc… the end-effector mass widely exceeds that of the supported load, and lot of works do not take it into account in their algorithms. These systems must be designed based on dynamic model; moreover the synthesis of the algorithm of an autonomous manipulator must be accomplished by taking into account nonlinearity and complexity of its dynamic model, this is in order to increase the control effectiveness. Currently, tasks involving a high precision welding of complex forms with high characteristics are very required in industry in general. This paper introduces the modeling of the end-effector movement equations to allow a tracking of welding cords with complex forms in the acceptable working zone. Read More Read Less