Research On Attitude Maneuver And Image Compensation Control For Flexible Satellite

With the development of space technology,the spatial resolution and time resolution of high-resolution remote sensing satellites are improving.In addition to the requirement of higher resolution of payloads,satellites need to have high-precision attitude control capabilities.To achieve the flexible observation of the ground targets by rapid attitude maneuver as well as improve the time resolution of remote sensing is the key to the performance of the remote sensing satellite.The low-orbit high-resolution remote sensing satellites adopt the push-scan imaging control mode.When the satellite performs the rapid attitude maneuver,it needs to synchronously complete the image motion compensation,that is,the drift angle tracking.Thus,push-scan imaging mode increases the complexity of the attitude maneuver control of these satellites.The high-resolution imaging satellites structures become more complicated,uch as large solar arrays and two-dimensional driving antennas.As a result,the coupling between the attitude and the vibration grows more serious.In order to achieve the attitude maneuver control under the Time Delay Integration(TDI)scan imaging,the rapid attitude maneuver,the vibration suppression and the precise bias angle tracking are necessary to be solved simultaneously.Therefore,this dissertation aims at solving the push-scan imaging attitude control problem and studies the path planning control methods which are suitable for fast attitude maneuver with practical engineering considerations.At the same time,in order to avoid the influence of flexible vibration on the attitude stability during the attitude maneuver,the realization of active vibration suppression control with input shaping is further invesgated.Finally,by establishing a complete image shift model,the strong coupling problem of image motion and attitude motion during the satellite three-axis attitude maneuver is solved.By using the analytical solution of the mathematical model of the image motion,the precise tracking control of the drift angle is realized,which obtains the control ability of imaging while maneuvering.The correctness of the model and the control effect are verified by simulation results.Firstly,according to the dynamic characteristics of low-orbit high-resolution optical remote sensing satellites,a multibody rigid-fleixble coupling attitude dynamic model composed of the satellite platform,the flexible solar arrays and theirs driving motors is established.Additionally,based on the traditional attitude dynamic model,the mathematical model of the system vibration frequency and damping ratio is presented from the view point of frequency characteristics.In order to minimize the settling time after attitude maneuver,this dissertation studies the influence of different path planning methods on the settling time and the control precision.The path planning strategies with triangle,trapezoid,quadratic polynomial,cubic polynomial and sinusoidal angular acceleration modes are carried out.The comparative simulation analysis shows that the sinusoidal acceleration planning method not only can reduce the satellite settling time and minimize the excitation of the flexible appendages,but also has strong robustness to the dynamic parameter uncertainties.The effect of the algorithm is verified by the on-orbit flight test.In addition to the fact that the motion path should be as small as possible to cause flexible vibration,it is more practical to avoid the vibration by active vibration suppression.Hence,the input shaping is introduced into the path planning and the drive control of the flexible arrays,such that the settling time can be reduded by combining the vibration avoidance and active suppression control.The residual vibration ratio of the input shaper is analyzed under the inaccuracy frequency and damping ratio informantion.The maneuver command modulation and the array drive control modulation algorithms are designed with input shaping.Mathematical simulations and ground verification experiments are carried out.Spcially,the full physical test of the air-floating table verifies the active suppression effect of input shaping.For the strong coupling problem between the attitude motion and the image motion in the push-scan imaging mode,a new “zero drift angle” compensation control method is proposed.Through the establishment of a complete motion model of the mapping relationship of the ground target to the camera phase point,the influences of the motion factors such as attitude angle,attitude angular velocity,orbit,and earth rotation on the image shift are all considered in the image shift motion model.The constaints that the drift anlge equels to zero and the attitude is poiting at the ground target are used to obtain the command attitude,such that the fluctuation problem caused by the change of the angular velocity during the drift angle tracking is solved.Thus the smooth attitude maneuver and the bias angle tracking control commands are obtained.The composite control algorithm of “feedforward + feedback + step saturation constraint” is used to realize the precise attitude tracking control.Simulation results show that the control precision can meet the imaging requirements.The dissertation achieves the attitude control,the flexible vibration suppression and the accuracy drift angle compensation of the high-resolution low-orbit optical satellite during the attitude maneuver imaging by obtaining the attitude maneuver path and the analytical solution of the complete image shift model,which has the significant academic value.The relevant algorithms are implemented and verified by ground physics experiments or the control of on-orbit satellites,which can be used as an important reference for engineering application.