Javad Tayebi, Amir Ali Nikkhah and Jafar Roshanian
The purpose of the paper is to design a new attitude stabilization system for a microsatellite based on single gimbal control moment gyro (SGCMG) in which the gimbal rates are…
Abstract
Purpose
The purpose of the paper is to design a new attitude stabilization system for a microsatellite based on single gimbal control moment gyro (SGCMG) in which the gimbal rates are selected as controller parameters.
Design/methodology/approach
In the stability mode, linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG) control strategies are presented with the gimbal rates as a controller parameters. Instead of developing a control torque to solve the attitude problem, the attitude controller is developed in terms of the control moment gyroscope gimbal angular velocities. Attitude control torques are generated by means of a four SGCMG pyramid cluster.
Findings
Numerical simulation results are provided to show the efficiency of the proposed controllers. Simulation results show that this method could stabilize satellite from initial condition with large angles and with more accuracy in comparison with feedback quaternion and proportional-integral-derivative controllers. These results show the effect of filtering the noisy signal in the LQG controller. LQG in comparison to LQR is more realistic.
Practical implications
The LQR method is more appropriate for the systems that have project models reasonably exact and ideal sensors/actuators. LQG is more realistic, and it can be used when not all of the states are available or when the system presents noises. LQR/LQG controller can be used in the stabilization mode of satellite attitude control.
Originality/value
The originality of this paper is designing a new attitude stabilization system for an agile microsatellite using LQR and LQG controllers.
Details
Keywords
Morteza Tayefi, Jafar Roshanian and Ali Ghaffari
The purpose of this paper is to identify linear model parameters of launch vehicles based on the actual flight test data. To compare the estimated parameters with the ones…
Abstract
Purpose
The purpose of this paper is to identify linear model parameters of launch vehicles based on the actual flight test data. To compare the estimated parameters with the ones obtained by two other approaches: identification based on the recorded data from six‐degree‐freedom simulation of motion and linearization of the equations of motion via small‐disturbance theory as an analytical method.
Design/methodology/approach
As the vehicle contains all the key issues in system identification such as time‐varying, unstable, nonlinear, and closed‐loop dynamics, Kalman filter method under the autoregressive with exogenous input model structure is used as a powerful method to estimate the dynamic parameters.
Findings
Simulation results demonstrate that the linear model parameters used in the vehicle design and analysis should be validated by flight test data to accurate the vehicle dynamic model as more as possible.
Practical implications
One of the most important usages of a linear model of aerospace vehicles is to design their controller. Another application of the algorithm presented in this paper is to estimate online dynamic parameters of the vehicle when they are required for the operation of the control system.
Originality/value
Being strongly affected by vehicle dynamic characteristics, linear model parameters of launch vehicles play important part in their design and analysis.
Details
Keywords
Masoud Mirzaei, Seyedeh Nasrin Hosseini and Jafar Roshanian
This paper's purpose is to deal with single point and multipoint optimization of an airfoil. The aim of the paper is to discuss optimization in several design points (multipoint…
Abstract
Purpose
This paper's purpose is to deal with single point and multipoint optimization of an airfoil. The aim of the paper is to discuss optimization in several design points (multipoint optimization) and compare the results with those of optimization at a specified design point.
Design/methodology/approach
A gradient‐based method is adopted for optimization and the flow is governed by two dimensional, compressible Euler equations. A finite volume code based on unstructured grid is developed to solve the equations.
Findings
Two test cases are studied for an airfoil with initial profile of NACA0012, with two types of design variables. And at the end a multi‐point case is presented.
Originality/value
The advantage of this technique over the other gradient‐based methods is its high‐convergence rate.