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Showing 2 results for Moment of Inertia
Mohammad Amini, Hassan Salarieh, Aria Alasty,
Volume 13, Issue 4 (7-2013)
Abstract
In this paper a method for online identification of satellite moment of inertia tensor parameters based on recursive least squares method, is presented. It is assumed that the satellite actuators are three orthogonal reaction wheels. Dynamic equations of the satellite are extracted in a special manner. The only available sensor is a three axes rate gyro which measures the angular velocity of satellite in the body coordinate system. Due to existence of noise in this sensor, the regressor matrix used in least squares method, changes stochastically. So in this case, the classic least squares method is not useful, and it cannot converge. For solving this problem, a modified least squares method with robust scheme is presented and its stability is proved using Lyapunov stability theory. The presented method can be used online in presence of measurement noise and other sensor imperfections. Simulation results have shown that this method can identify inertia parameters of the satellite with less than 3 percent error comparing to real parameters before and after changes.
Alireza Arab Golarche, Mohammad Moghiman, Seyyed Mohammad Javadi Malabad,
Volume 15, Issue 12 (2-2016)
Abstract
Unlike HAWT, Darrieus wind turbines is faced with the self-start problem and high fluctuations at output torque. Because of the need for techniques based on meshing and coupling Eulerian fluid equations and the Lagrangian equations for moving rigid body, the calculation of rigid body acceleration and fluctuations torque of VAWT is very complicated and it is a function of the moment of inertia of the turbine. In most studies, regardless of this effect, the angular velocity of turbine is assumed to be fixed. In this study, for calculating the turbine rotational speed and position, the sum of wind-driven aerodynamic forces and external forces caused by friction and generators are calculated and placed into Newton's second law to calculate the acceleration, and integrating it in time steps. The simulation is performed unsteady and dynamic mesh is used for moving the rotor. The results could check the interaction between wind and rigid blades on the in the process of increasing the rotational speed of turbine, and simulate the rotor from the moment of rest until the turbine reaches its final rotational speed. The causes of reduction in torque at low rotational speed is investigated and it has been shown that high dynamic stall and passing high exergy flow into the rotor without interaction with blades results the power reduction. Moment of inertia has significant impact on the frequency and amplitude of rotational velocity, fluctuations of output torque and output power, which is important in mechanical analysis of blades’ fatigue.