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۱Development of a Robust Observer for General Form Nonlinear System: Theory, Design and Implementation
اطلاعات انتشار: International Journal of Robotics، چهارم،شماره۲، ۲۰۱۵، سال
تعداد صفحات: ۱۲
The problem of observer design for nonlinear systems has got great attention in the recent literature. The nonlinear observer has been a topic of interest in control theory. In this research, a modified robust sliding–mode observer (SMO) is designed to accurately estimate the state variables of nonlinear systems in the presence of disturbances and model uncertainties. The observer has a simple structure but is capable of efficient observation in the state estimation of dynamic systems. Stability of the developed observer and its convergence is proven. It is shown that the estimated states converge to the actual states in a finite time. The performance of the nonlinear observer is investigated by examining its capability in estimation of the motion of a two link rigid–flexible manipulator. The observation process of this system is complicated because of the high frequency vibration of the flexible link. Simulation results demonstrate the ability of the observer in accurately estimating the state variables of the system in the presence of structured uncertainties along with different initial conditions between the observer and the plant.

۲Optimal Trajectory Generation for Energy Consumption Minimization and Moving Obstacle Avoidance of SURENA III Robot’s Arm
اطلاعات انتشار: International Journal of Robotics، چهارم،شماره۳، ۲۰۱۵، سال
تعداد صفحات: ۹
In this paper, trajectory generation for the 4 DOF arm of SURENA III humanoid robot with the purpose of optimizing energy and avoiding a moving obstacle is presented. For this purpose, first, kinematic equations for a seven DOF manipulator are derived. Then, using the Lagrange method, an explicit dynamics model for the arm is developed. In the next step, in order to generate the desired trajectory for the arm, two different methods are utilized. In the first method, each joint motion is presented by a quadratic polynomial. In the second one, the end effector’s path has been considered as 3 polynomial functions. Also, a known moving spherical obstacle with a linear path and constant velocity is considered in robot workspace. The main goal of optimization is to reduce the consumed energy by the arm in a movement between two known points in a specified time frame to avoid the moving obstacle. Initial and final velocities of the arm are set as zero. To this end, the optimization is carried out using Genetic Algorithm. Finally, in order to obtain the most reliable solutions for trajectory generation, many optimizations with various parameters are conducted and the results are presented and discussed.
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