Research On Rapid Maneuver And Stabilization Method For Agile Satellites

Agile satellites are able to achieve rapid attitude maneuver in a short time, andtherefore they are very suitable to be applied into the high resolution Earthobservation system project of our country. Reasonable path planning mayeffectively shorten the time needed to complete the maneuver task, step up thecontrol efficiency and precision. At the same time, excellent attitude controller mustbe designed. In this paper, problems about rapid maneuver and ability for agilesatellites are intensively studied.First of all, considering a rigid body adopting the control moment gyros asactuators, attitude kinetic equations and dynamic equations are established. On thebasis of Euler rotation theory, the rapid maneuver path is divided into three parts:acceleration section, constant speed section and deceleration section, and Hermiteinterpolation is used for the angular velocity of turning points. Based on the errorquaternions and error velocities, error kinetic equations and error dynamicequations are established. Simulation results show the advantages of path planning.Secondly, the actuator schemes for agile satellites are studied. For the inherentsingularity problem of single gimbal control moment gyros, singularity mechanismis analyzed, pseudo-inverse steering law, singularity robust inverse steering law,generalized singularity robust inverse steering law, and predicted robust inversesteering law are compared with each other, simulations show that the latter twosteering laws could escape from the system singularities, but bring in torque errorssimultaneously. Taking single gimbal control moment gyro’s and reaction wheel’sdifferent advantages, a union actuator is proposed. In addition, studies on thestructure and operation principle of variable speed control moment gyros are carriedout, meanwhile steering law based on pseudo-inverse solution and null motion isdesigned. Simulation results show that the VSCMG system of pyramidconfiguration could supply accurate control torque, and never encounter anysingularities, so become ideal actuators for agile satellites.Lastly, for the rapid maneuver and stabilization task of agile satellites, a PDcontroller based on error quaternions and error angular velocity is designed, itsstability is proved by Lyapunov direct method. On the foundation of that, a cascadesaturation PID controller is designed with consideration of the actuators’ torquesaturation and the maximum angular velocity limitation, the integral separationcoefficient and integral impairing coefficient are added in order to solve the integral saturation problem. This controller’s command torques won’t overstep themaximum threshold, actuator causes small torque errors, and the system gets higheraccuracy. As the sliding mode variable structure control is able to deal with thesystem parameter indeterminacy and environmental disturbance, a self-adaptionsliding mode controller is proposed. This controller could solve the indeterminacyof moment of inertia in a better way, and realize rapid maneuver and stabilizationwith high accuracy for agile satellites.