Research On Attitude Planning And Control In Scanning Mode Of Agile Satellite

Scanning mode of agile satellite is a complex operating mode with broad application prospects,which can enable continuous imaging for any earth surface area.This imaging mode has a variety of complex technical requirements for attitude control in the process of maneuvering and imaging.In addition,high standards of the maneuvering speed,attitude pointing accuracy and attitude angular precision are required in the maneuvering and imaging.In order to overcome these issues,this paper investigate the motor control strategies and algorithms to fully exploit the available capacity and attitude maneuver precision process control methods,and identify the impact of attitude maneuver ability and attitude control precision maneuvers important design elements to support the optimization of agile platform.The mainly work is as follows:Firstly,the relevant mathematical models of agile satellite control system are obtained,which consist of the definition of the attitude control system commonly used coordinate system,the gesture description method and its conversion relationship,attitude kinematics,rigid body dynamics model,a flexible dynamic model and the theory of attitude sliding modal control.Secondly,the influence of flexible appendage vibration of scanning process on the attitude pointing accuracy and stability analysis under the scanning mode is investigated.When the angular acceleration ? of the main factors that stimulate the flexible vibration motor is not zero,a reasonable attitude maneuver flexible path to suppress vibration is planned.And based on the current investigation of the attitude maneuver path,the acceleration section and deceleration section asymmetric attitude path are designed,then establish the optimal model of the path parameter and the optimal motorized path is obtained by using the optimization algorithm.Simulation results show that the proposed sinusoidal angular jerk attitude paths exhibits better inhibition for the flexible appendage vibration.Speed photographic imaging process models and integration time model of the scanning are also established to design the attitude maneuver path by using the uniform-changes and speed-altitude ratio.Experimental results show that the constant rate of change in speed-altitude ratio photography attitude path can effectively reduce the integration time of the imaging process frequent adjustments.Thirdly,the union attitude determination principle of the "Gyro + Star sensor" under maneuvering is investigated to establish the gyro measurement model.The measurement model of star sensor is derived under rapid mobility based on the analysis of the influence of stellar angular velocity on CCD imaging-defocusing.The state equation and measurement equation are established and lineated,then Extended Kalman Filter(EKF)is used for data processing to analyze the accuracy.Aiming at the unknown statistical characteristics of systematic noise and large error of strong nonlinear,EKF algorithm is improved by observing the noise of the system noise and measuring the noise in real time.Jacobi matrix is improved by iterating the observed matrix in real time to ensure the estimated value and observed value have a higher degree of matching.Simulation results show that the algorithm exhibits effectiveness in the case of large angle maneuver,which meet the requirements of attitude accuracy and stability in push-broom mode of agile satellite.Lastly,the principle and conformation of the single gimbal control moment gyroscope(SGCMG)are established and pentagonal pyramid configuration SGCMGs singularity analysis is also carried out.We select zero movement on SGCMGs pseudo-inverse steering law for avoiding singular configurations to establish a framework for the servo motor model.High precision control of the switching process is obtained by complex combination control of scanning mode with input shaper and sliding mode control?Aiming at the sensitive issue of traditional input shaper right attitude for the interference in the closed loop,a robust input shaper order with inner loop is designed to suppress the flexible appendages motivated due to vibration motor.By tracking the attitude planning-path accurately with sliding mode control,the singular state of SGCMG is avoiding effectively.Meanwhile,in order to ensure the effective target capture during the scanning imaging process of the imaging mode,the drift angle which is produced by the sub-satellite point speed inconsistency with the scanning speed is analyzed.Correction control of drift angle is obtained by compensating of the yaw attitude to control the image motion reasonable for the requirement of high imaging precision.Simulation results show that the designed controller can effectively solve practical problems corresponding to verify the effectiveness of the control strategy design and reasonable.