seyed aliakbar kasaeian; Masoud Ebrahimi
Volume 11, Issue 2 , September 2018, , Pages 21-31
Abstract
The present study aims to present a safe, robust and fast orbital rendezvous guidance. The scheme improves the rate of convergence to equal point until the chaser spacecraft reaches the proximity target. Then, the robust guidance structure is transformed in order to avoid singularity and provide safe ...
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The present study aims to present a safe, robust and fast orbital rendezvous guidance. The scheme improves the rate of convergence to equal point until the chaser spacecraft reaches the proximity target. Then, the robust guidance structure is transformed in order to avoid singularity and provide safe rendezvous for reaching the target. Switching is conducted in the guidance scheme by utilizing a self-defined sign function. Moreover, a new modified saturation function is employed instead of the discontinuous part of the sliding mode. The Lyapunov function approach guarantees the asymptotic stability. Numerical simulations are conducted by both linear and nonlinear models of relative dynamics. Mean anomaly, angular velocity, and eccentricity of target orbit are considered as the uncertainties. Finally, the results indicate the performance and robustness of the proposed guidance in the presence of non-linearity, uncertainties, and disturbances, compared to the conventional sliding mode.
Ali Reza Aghalari; Ahmad Kalhor; Farhad Shamim
Volume 8, Issue 1 , April 2015, , Pages 73-77
Abstract
In this paper, a designing procedure of a Variable Speed Control Moment Gyro (VSCMG) for performing an agile maneuver in an attitude control simulator is described, then a prototype is fabricated and finally the test results are presented. The design of actuator mechanism is based on simulator limitations ...
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In this paper, a designing procedure of a Variable Speed Control Moment Gyro (VSCMG) for performing an agile maneuver in an attitude control simulator is described, then a prototype is fabricated and finally the test results are presented. The design of actuator mechanism is based on simulator limitations (power consumption, dimensions and weight, simplicity) and direction of produced torque.Two DC electrical motors are used for controlling the angular velocity of flywheel and the gimbal slew rate. The motors controller and driver units are designed and implemented, so that the maximum accuracy, minimum errors and best response time could be accessible. Structural Design is based on strength, stiffness, volume and weightalso Necessary analysis are performed using ANSYS. Finally the functional tests of actuator such as measuring the produced torque (using simulator and load transducer), accuracy of gimbal position and gimbal slew rate, accuracy of flywheel rotational speed and power consumption are performed and then the results are presented.
