| With the continuous increase in the number of space vehicles,on-orbit clearance,on-orbit refueling,and on-orbit maintenance technologies for spacecraft are becoming effective methods to alleviate the tension of space orbit resources and maintain space order.The space circumnavigation observation mission is a preceding indispensable process of the above tasks,which demands the controlled active spacecraft to circumnavigate around its non-cooperative target and keep the space-borne camera always pointing to the noncooperative target.Then,the controlled active spacecraft can provide sufficient image and data support for rapidly formulating a proximity operation scheme.In fact,the key technology of space circumnavigation missions is the high-precision attitude-orbit synchronization control technology,which is also a necessary generic technology for many kinds of complex space contact operation tasks.However,since there are many difficulties in analytical solution and stability analysis of nonlinear systems,the theoretical research and experimental verification of this technology are not perfect.Therefore,the modeling and control of the space circumnavigation mission is still an open problem with great theoretical value and practical significance.The challenge for designing an effective controller of the space circumnavigation mission is multifaceted: in addition to the typical adverse factors such as propulsion system saturation constraints,model parameter drift,and space perturbation,the orbit maneuver dynamics of the controlled active spacecraft is also strictly constrained by attitude pointing conditions,and the real-time adjustment of the active spacecraft’s attitude further increases the difficulty of modeling the relative orbit motion.Therefore,the kinematics and dynamics of this mission have some remarkable characteristics: the system states are coupled,the coupling relation is not fully known,and the constraint logics are complex.To realize the control objective under the aforementioned challenge,the author thoroughly investigates the implementation achievement of many kinds of space proximity relative motion and the major research results of nonlinear systems’ sliding-mode control,this dissertation expounds on some key technical difficulties of the attitude-orbit synchronously modeling and control of space proximity relative motions;then,according to the unit quaternion method and the Newton dynamical method,this dissertation constructs attitude-orbit coupling kinematical and dynamical model for simultaneously describing attitude and orbital maneuver of the space circumnavigation mission,and gives corrections of the propsoed model under measurement uncertainties;furthermore,several high-precision attitude-orbit synchronization control methods for this mission are discussed in detail from the perspectives of actuator output constraints,state constraints,performance(approximate)optimization,fast convergence,and gain autonomous estimation;theoretical proofs and simulation verifications of the main conclusions are also given.The main contributions of this dissertation are as follows:To avoid the discontinuous switching in the modified-Rodriguez-parameters-based proximity attitude-orbit synchronous maneuver model when describing a large-angle attitude maneuver,this dissertation establishes a global nonsingular model of the mission via the unit-quaternion-based attitude description method.In addition,the mathematical connections between the active spacecraft’s desired angular velocity and angular acceleration and the relative orbital position of the two satellites are given analytically.The resulting model can clearly show couplings between the attitude and orbital systems.Considering that the attitude and orbit tracking errors may be large when the controlled active spacecraft is disturbed by mismatched uncertainties and constrained by actuator’s saturation limits,and there is no explicit constraint on the maneuver boundary,then this dissertation makes corrections to the aforementioned space circumnavigation model by considering measurement uncertainties and maps the active spacecraft’s attitude and orbital tracking errors to an exponential attenuation boundary.Furthermore,the effective estimations of unmatched uncertainties are realized by means of a finite-time disturbance observer,and the finite-time reaching law of the employed nonsingular terminal sliding-mode surface is given under state and input constraints;the stability analysis under the finite-time stability framework of nonautonomous systems proves the effectiveness of the proposed controller.Since the conventional Lyapunov-based control methods are conservatism and there are no explicit performance constraints of the controlled plant,this dissertation proposes an effective "fuel-time" performance index and a corresponding(approximate)optimal controller to fit the requirements of the space circumnavigation observation mission.In the proposed controller,an actor-critic network is introduced based on the adaptive dynamic programming technique to approximate the numerical solution of the corresponding HJB equation.Thanks to the introduction of two non-quadratic terms in the proposed "fueltime" performance index,the obtained approximate optimal controller can strictly meet the saturation constraint of the space-borne propulsion system,and the node weights of the actor and critic networks will not be updated quickly when the initial values of the controlled system are large.To solve the problems that the rate for reaching the chosen nonsingular terminal sliding-mode surface decreases with the convergence of system states,and the chattering of the corresponding first-order sliding-mode controller is large,this dissertation proposes the globally Lipschitz continuous practical terminal sliding-mode manifold and its corresponding chattering-reduced controller.The derived super-twisting-algorithmbased practical terminal sliding-mode controller can establish a high gain dynamics at the equilibrium and significantly reduce the chattering typical in first-order sliding-mode controllers.Furthermore,based on the adaptive dynamic programming technique framework,an approximate optimal reaching law of the chosen practical terminal sliding-mode manifold is given.Simulation results show that the proposed approximate optimal controller can synchronously drive the active spacecraft’s attitude and orbital tracking error to reach the selected practical terminal sliding-mode manifold and further converge to a small neighborhood of the origin.To improve the convergence rate of the aforementioned practical terminal slidingmode manifold in the unit neighborhood of the equilibrium,this dissertation further proposes a so-called fast practical terminal sliding-mode controller and its super-twistingalgorithm-based controller,which can keep the generalized velocity of the controlled system at a high level in the annular neighborhood of the equilibrium.Furthermore,considering the mission requirements,such as the output constraints of the propulsion system,external disturbance with unknown upper bound,and rough dynamical feedback of the desired angular acceleration,this dissertation designed a fuzzy adaptive supertwisting practical terminal sliding-mode controller for the studied space circumnavigation mission.The proposed controller realizes accurate feedback of unknown dynamics using hierarchical fuzzy approximation technology and finite time observation technology.In addition,by introducing the auxiliary fuzzy output with high gain into the anti-saturation compensation system,the precision loss of the attitude and orbital tracking error caused by fuzzy auxiliary output can be effectively reduced.Furthermore,the adaptive updating strategy can reduce the conservatism of gain selection of the classical super-twisting sliding-mode controller,and the employed hyperbolic tangent function can effectively reduce the system instability risk caused by rapid parameter updating.Finally,the author gives conclusions and prospects of this dissertation. |
PDF Full Text Request