Research On Control Design Method Of Underactuated Mass Moment Spacecraft

The mass moment control technique is proposed as a new control method for space-craft in recent years, whose principle is to change the mass-center of the spacecraft bymoving the position of the masses inside the spacecraft with high-speed, so as to producemoment to obtain the fast attitude response and the required overload of the spacecraft.Underactuated systems are control systems with fewer control inputs than the numberof configuration variables, which are widely existed in robotics, aerospace vehicles, andtransportation vehicles. And the control of underactuated systems is becoming an activeand challenging field of research due to the lack of control inputs . Since the mass mo-ment spacecraft holds fewer actuators than the number of attitude freedom, the attitudecontrol systems of the mass moment spacecraft are typical underactuated systems.Thecontrol of underactuated attitude system is not only a practical but also a helpful work tothe development of control theory on underactuated systems.In the framework of control theory on underactuated systems , this dissertation isdevoted to special parameter optimal design and attitude control of underactuated massmoment spacecraft based on degree of controllability and control design.Firstly, due to the limitation of the internal space of the craft, an underactuatedconfiguration for attitude control, which holds two masses moving along linear lines, isproposed subjected to the mass moment spacecraft. The dynamical model of underac-tuated mass moment spacecraft is established by Lagrangian method, considering theimpacts to the inertia and aerodynamic torque caused by the moving of the masses. Fur-thermore, a simplified model of underactuated mass moment spacecraft is derived forreducing the complexity for design.Secondly, it is proposed that taking the recovery region of the underactuated statesas the index measurement, in terms of degree of controllability analysis. On one hand, atime optimal degree of controllability analysis method is derived by studying the seriesexpanding form of underactuated systems, considering the limitation of amplitude ofthe inputs. On the other, an energy optimal degree of controllability analysis method isderived by solving the energy optimal control problem due to the limitation of energyinputs.Thirdly, an optimization design method of special parameters is studied based on time optimal degree of controllability of the underactuated mass moment spacecraft. Thefunctional relation between the index of degree of controllability and the special param-eters is established based on the definition of index of degree of controllability for under-actuated systems, taking the recovery region of the attitude angle, which belongs to thedirection of degree of freedom that is underactuated when the position input is bounded,as the index measurement. An optimization design of special parameters is operated bytraversal in order to enhance the capability to change the attitude angel. The effectivenessof the design is proved by a simulation example.Furthermore, the attitude control method of underactuated spacecraft is studied, and an asymptotically stable control law is driven by passivity control method at equilibria.The matching condition is proposed to make sure that the control law is existed. Due tothe complexity of the nonlinear partial differential equations, the matching conditionis simplified and solved. The effectiveness of the control law is proved by simulationexamples.Lastly, on the basis of utilizing optimization and passivity method to implementthe underactuated system control design, the attitude control problem for a certain un-deractuated mass moment spacecraft in atmosphere is provided. Based on the analysisof the maneuver manner of the underactuated mass moment spacecraft, performance in-dex requirement of attitude control system is presented. The characteristic parametersoptimal design is implemented by considering restriction conditions of these parameters.The attitude controller law considering the Euler attitude angles as state variables is pre-sented to allow angles of attack and roll to track desired commands and angle of slide tostay close to zero, which satisfies the performance index requirement of attitude controlsystem. Finally, the close loop simulation shows the effectiveness of the characteristicparameters optimization and the attitude control method by considering disturbance mo-ment, the dynamics of mass displacement and atmospherical parameters perturbation,respectively.