Research On Attitude Control Of Upper Stage For Multi-satellite Deployment

With the increasing of multi-satellite launch missions, the value of multi-satellite upper stage is increasing every day. However, when a part of payload is released of a multi-satellite upper stage, its moment of inertia and CM(center of mass) position changed meanwhile, which produces inertia coupling and control coupling, and leads to three axis attitude coupling at last. Aimed at solving the aforementioned control problem, this dissertation deeply studies attitude control of boost phase based on backstepping, attitude decoupling control of boost phase using sliding mode variable structure, and time optimal attitude control of post-boost phase. The main contents are as follows:Attitude control of boost phase based on backstepping. Aimed at solving the three axis attitude coupled multivariable, strong coupled complicated nonlinear control problem of multi-satellite upper stage, The unbridged attitude control law based on backstepping and the proof of its stability is given. According to the control mechanism of the multi-satellite upper stage working during boost phase, the calculation formula of control torque produced by the nozzles in rolling direction is given, so does the relationship between the control torque relative to the changed CM position and the thrust yaw angle, thrust pitching angle of the sustainer. And the numerical method of solving the thrust yaw angle, thrust pitching angle by the expected torque. In the ideal situation and considering control constraints, attitude control of boost phase based on backstepping can effectively control the attitude of multi-satellite upper stage. However, it is deficiency in response to the disturbances. Thus, a controller with stronger robustness need to be proposed.Attitude decoupling control of boost phase using sliding mode variable structure. As there is some insufficiency of the attitude controller of boost phase based on backstepping, an attitude decoupling control method of boost phase using sliding mode variable structure is proposed. For the attitude control system of multi-satellite upper stage with three axis attitude coupling, uses feedback linearization to decoupling. To make the controller more robust, the corresponding sliding mode variable structure controller is designed for each triaxial channel. And the stability of them are proved. Aimed at solving the flutter of sliding mode variable structure controller, use the exponential reaching law of function structure sliding mode control algorithm, and the flutter is successfully eliminated. whether in attitude maneuver time, accuracy of attitude parameters and angular velocity, or in terms of anti-interference, attitude decoupling control of boost phase using sliding mode variable structure is far better than that of Attitude control of boost phase based on backstepping.Time optimal attitude control of post-boost phase. To deal with the time optimal attitude control problem of post-boost phase for the multi-satellite upper stage, a time optimal attitude control method based on Gauss pseudo-spectral method is proposed. According to the control mechanism of the multi-satellite upper stage working during post-boost phase, the control torque produced by attitude control nozzle of the multi-satellite upper stage during post-boost phase is calculated in detail. That is to say the relationship between the three-axis attitudes control nozzle switching function and the control torque are given, which are considered in the description of the time optimal attitude control problem. But there is some error. And as an open-loop control method, it’s unable to suppress interference. Thus, further terminal correction by using attitude decoupling control based on sliding mode variable structure is proposed. And the control scheme of switching function for the three axis attitude control nozzle is introduced. the method is of high precision, and has strong anti-interference capability.