Attitude Determination And Control System Of A Three-Axis Stabilized Satellite

It is necessary for satellite to control specific movement to realize some function on the orbit. One of the most significant technologies is attitude determination and attitude control and attitude determination is the precondition of attitude control.Most of satellites were configured high-precision sensors such as star sensor, solar sensor. However, once these sensors can't work normally, the attitude determination system couldn't determine attitude accurately. To improve robustness of the attitude determination system, in this dissertation, a new Sensor-Combination method is proposed, which is composed of gyroscope, infrared earth sensor and magnetometer, when the high-precision sensors are off-work. One of the most important advantages of this method is its low cost.Not only is satellite affected by constant disturbance such as air torque and sun pressure torque, but also affected by periodical disturbance which is sun pressure torque typically when satellite is running on the orbit. The integral controller is applied to suppress the disturbance in conventional methods. Nevertheless, the satellite is still severely affected by periodical disturbance which may result in vibration of attitude and flywheel angular momentum, which is surely not desired. A new controller, which is added by periodical disturbance filter based on conventional methods, is designed to suppress those fixed frequency periodical disturbance. Simulation results for the satellite model illustrate the precise pointing control and vibration suppression.It is well known that the high-accuracy angular velocity sensors such as gyroscope are normally costly. Once the angular velocity sensors couldn't work properly, the full state control law couldn't work normally either even though the dear sensors are affordable. A new output feedback control law which is independent of angular velocity state is proposed for non-linear model in this dissertation. This method is valuable especially when the rate sensors are off-work. The control system could work normally without adding any hardware.After completing simulation work with matlab and validating of the theory, it's naturally to design accordingly real time simulation software to prepare for hardware in loop evaluation. Structure method is applied to design satellite real time simulation software normally, whereas it is not easy to maintain and extend. Data and function effects each other in the program, new data must be added accordingly if an extra function is added, we must modify all the related functions which cause huge work burden. Structured method is replaced by Object oriented method to improve the performance of the software.