Study on the three-axes attitude controller design of Satellite using reaction wheel

Attitude controller of small satellite was designed in this paper. Four reaction wheels give a control torque to the satellite. At first, the design of wheel speed controller was performed by using linear model and then it was considered that each nonlinear effect to this system by inserting nonlinearity. The design purpose of wheel speed controller is that the outputs(wheel angular velocity or wheel angular momentum) show the fast response to the desired momentum. The PI controller was used in order to get the fast response speed without overshoot. Three-axis attitude control was performed by using precede reaction wheel model after completing wheel speed controller. Reaction wheels have a 'pyramid' configuration which all four wheels are skewed and one wheel is a redundancy. Same as the wheel speed controller, PI controller was used and designed to coincident with the given bandwidth of the satellite. If the inputs that compensate the attitude error due to the external disturbances or perform the mission of the satellite are given to the attitude controller, it can be acquired that attitude error, wheel angular momentum, angular velocity of the satellite, and etc.