Research On Issues Of Dynamics And Control For Complex Remote Satellite

With the development of space technolog, the structure of modern spacecraft is more and more large, flexible and complex. Especially for the high-precision and high-resolution remote satellite, there are various motion types, multiform tasks and higher control precision. Therefore, more and more factors should be considered in modeling and control of the system. The effects of body flexibility, liquid s loshing in container, contact and impact in clearance joint of driven mechanism on the dynamics performance and attitude control of satellite are significant. The research on dynamics modeling and attitude control for high-precision flexible remote satellite is necessary to achieve high-stablity and high-precision index, which has impartant significance of theory and engineering application. The thesis is focus on the engineering application demand and for the high-precision large remote satellite. Large flexible remote satellite attitude dynamics and control is studied in this dissertation. The remote satellite model studied is a representative one, with a number of flexible components, four fluid-filled tanks as well as rotating camera and antennas. The issuses on deployment of flexible appurtenance, couping dynamics characteristics and attitude control of the remote satellite are investigated theoretically and applied. The main contents are as following:First, the complete dynamics model for the flexible remote satellite is presented. The dynamics feature of flexible multibody remote satellite is analyzed. The complete dynamic equations of motion of the flexible remote satellite have been derived based on the principle of virtual power. The equations includes satellite displacement equation, satellite attitude equation, vibration equations of flexible components, sloshing equation of fluid-filled tanks, rotating equation of camera and rotating equation of antennas, which is the basis of the subsequent chapters.Second, the effects of joint clearance on appurtenance deployment and attitude motion of satellite are investigated. The mathematic model of clearance joint for multibody system is estibalished. The contact model is performed using a nonlinear continuous contact force model and the friction model is considered using a modified Coulomb friction model. Then, the contact models are a pplied to the aerospace field and for the deployment of flexible solar panels with clearance joints. The numeric simulation of the deployment of solar panels with clearances on satellite is presented. The effects of clearance on the appurtenance deployment and attitude motion of satellite are discussed.Third, the coupling dynamics characteristics of flexible remote satellite after the appurtenance deployment and locking are analyzed. Based on the dynamics modeling of the flexible remote satellite, the effects of virous disturbing factors on the attitude of satellite are presented. The dissymmetry of the satellite configuration causing the coupling between satellite displacement and attitude as well as the coupling between different satellite attitude channels is ptesented. The satellite attitude influenced by the vibration of flexible components and sloshing of liquid in the tanks are discussed. is useful for designing satellite attitude control.Then, on the basis of the dynamics modeling and analysis, the attitude control technique is studied. Two different types of attitude controller are designed for flexible multibody remote satellite, which are PID attitude controller and H∞ robust attitude controller. H∞ controller is designed by solving H∞ mixed sensitivity problem. The center rigid body is chosen for the object of control while the vibration of flexible components and sloshing of liquid being chosen for multiply uncertain disturb. The rand of the H∞ control is 4 and the high rank problem of H∞ control is avoided. The attitude control for satellite is discussed and it ’s proved that the controller is robust.Finally, the satellite attitude composite control is designed against disturb caused by rotating of camera and antennas. The feedforward control for satellite attitude is designed with camera and antenna rotary. Due to the coupling between satellite displacement and attitude, the feed-forward control of the composite control is designed by considering both satellite displacement equation and satellite attitude equation. Disturbs for satellite attitude are reduced by the composite control. Then, the pointing composite control of camera and antennas are designed. The pointing composite control of camera is based on PID control. The pointing angle compensation of satellite attitude is calculated and the effects of satellite attitude on camera pointing are analyzed. The precision of camera pointing is improved using the coordinated control of camera pointing and satellite attitude.