Research On Motion Trajectory Planning Of Space Telescope

In recent years,with the development of space technology,the space exploration is of great expansion.On-orbit detection and tracking becomes a cutting-edge technology in the space exploration,and the demands of observating resolution are increasing dramatically.Driven by this requirement,the increment of eyepiece aperture and the massive proportion of space telescope has gradually become a trend.As a consequence,the reaction effect caused by the motion of the optical telescope cannot be ignored anymore.It has become a consensus that proper planning of the space telescope trajectory can reduc e interference obviously.Due to micro-gravity environment of the outer space,the actual work condition of the carrier base is between the fixed base and the free floating base,the disturbance analysis as well as the optimization process is more complicated.In order to simplify the problem,this paper idealized the carrier base into two working modes,i.e.the fixed base and the free floating base.It takes a deep research on space telescope from three aspects: the modeling of the system reaction disturbance,the motion trajectory planning on the fixed base and the motion trajectory plan ning on the free floating base,which aim to complete the point-to-point movemet task within the specified time as well as minimizing the total disturbance.This study includes:Firstly,this paper establishes telescope reaction model on the fixed and free-floating base separately.Based on the Newton Euler method and the rigid body dynamics theory such as coordinate transformation,theorem of angular momentum and the composition of angular velocity vector,this paper set up the telescope reaction disturbance mathematical model on the fixed base,and turns it into the form of differential-algebraic equations.While in the free floating mode,the nonholonomic constraint of angular momentum conservation is well considered.Due to the concept of perturbation jacobian matrix,the physical relation between the satellite attitude disturbance and the telescope motion is established.Secondly,the trajectory optimization problem of space telescope on fixed base is studied.Actually,the problem can be further abstract to a time continuous Bolza type optimal control problem.Comparison of the advantages and disadvantages of several kinds of optimum solution,pseudo-spectral method is regard as the most effective way to this kind of nonlinear dynamic optimal problem;In this paper,a numerical solution based on Chebyshev pseudo-spectral method is presented in sequence of the optimization goal,boundary constraint condition,initial value estimation and static optimization method.Finally,the trajectory optimization problem of space telescope in free floating mode is discussed.First of all,the L2-norm of the carrier attitude increment is chose as the performance evaluation index after careful consideration.Secondly,on the base of the kinematic equations,the local property of the generalized jacobian matrix is presented.It shows how to obtain the direction of the minimum disturbance by using the singular value decomposition(SVD).In terms of long distance point-to-point path planning problem,this paper turns it into a classic NLP which can be solved in a proper way.In order to improve the disturbance trajectory optimization performance,extra physical constraints are applied.