Pose Measurement And Tracking Control Of Spatial Non-cooperative Uniaxial Rotated Target Based On Monocular Vision

With the developing of space exploration,the technology about aerospace field has been rapid developed.Spacecraft docking,space capture,garbage cleanup and other technology have become hot researches around the world.Space non-cooperation target intersection is a difficult point,and the determination of the relative position is a key point.For this point,people have studied a lot of methods,in which visual measurements have been greatly affirmed.Visual measurement system which has the simple and low-cost features,has been a visual measurement in the approximation of the navigation.In the current visual measurement,the two targets are relatively stable in the case without taking into account the rotation of the target.Based on the predecessors’ research of monocular vision measurement system,we carry up with a detailed study about relative pose measurement and tracking control problems of non-cooperative uniaxial rotation target to improve the current visual measurement methods of some shortcomings.This provides an important reference for the future "in orbit service" mission,such as rescuing the satellite,cleaning up space garbage.First of all,this paper introduces the current situation of research on the relative attitude measurement of space non-cooperation target,and understands the technical level of current visual measurement,and analyzes some of the shortcomings,and points out the focus and direction of this paper.This paper briefly summarizes some of the principles in the visual measurement system and the theory of spacecraft attitude motion,which lay a solid theoretical foundation for the later research.Secondly,we choose the angular velocity measurement method of video information processing for the measurement of relative angular velocity of non-cooperative target.We usually use the straight line vector extracted from adjacent images to calculate the angle between two straight lines,and divide the angle by time interval to obtain angular velocity.However,this method has some drawbacks: since the angle between the vectors is within 180°,the wrong value is obtained when the turning angle is greater than 180°.In this paper,we use the plural form to express the linear vector,and use the quotient of two vectors to represent the angle between the two.In the case of the rotation angle of more than 180° and no more than 180°,by comparing the positive and negative cases of the real part and the imaginary part,the complete angle calculation formula is obtained,and the defects in the method are solved.In the last,we verify the theory by simulation.On the basis of the inverse projection theory proposed by predecessors,we use the genetic algorithm to solve the rotation matrix,which avoids the singularity problem which may occur in the SVD solution.At the same time,the number of iterations of the rotation matrix in the whole algorithm is obviously less than that of the traditional method,which have been verified through experiments.In the aspect of tracking control,two kinds of control methods,PID control and sliding mode variable structure control,are mainly considered and studied.The former is a typical traditional control method,the latter is the emerging control method.The design of the control law is carried out for the attitude velocity control respectively.The stability of the control law is proved by the Lyapunov stability theorem.Finally,on the basis of Simulink,the tracking spacecraft model is built to simulate the function of each module in the whole control system of the spacecraft,and the closed-loop control system is built.Experimental simulation results prove the stability of the control system,which can smoothly reach the desired attitude and angular velocity and complete the attitude and angular velocity tracking control.