Research On Dynamic Modelingand Control Of Solar Sail Spacecraft With Complex Mechamisms And Structures

The spacecraft with unique propulsion advantage is one of the researchpriorities and focuses in the field of aerospace. Solar sail, which makes use ofsunlight as the propulsion thrust, has been one of the hotspots. Solar sail has thefeatures of light-weight, geometric nonlinearity, complex mechanisms and structures.The problems are important for solar sail to operate on orbit. Therefore, thedissertation will carry out research on structural statics and dynamics, attitudedynamics, and rigid-flexible coupling dynamics and control. The detail is asfollowing.First, the dissertation analyzes the structural statics for solar sail consideringgeometric nonlinearity, then the thrust loss is carried out based on structuraldeformation. The solar sail support beam is considered as the main stiffness supportstructure and the film surface will be deformation with the support beam. The staticanalysis is carried out for the conditions of infinity and two points connectingbetween support beam and the film undergoing static force generated by lightpressure. The element equations are derived based on the principle of virtual work.Then the whole structure equations are assembled. The reduced equations arederived by considering boundary conditions. Newton-iterative algorithm is proposedto deal with the nonlinear algebraic equations. The thrust loss caused by thedeformation is given based on static analysis. The computational results indicatethat the nonlinear axial displacement is comparatively large, and the thrust loss forinfinity points connecting style is smaller than two points connecting style under thecondition of identical parameters.Second, the dissertation studies the structural dynamics for solar sailconsidering geometric nonlinearity. The support beam is considered as the mainsupport structure. The vibration analysis of nonlinear beam undergoing static forcegenerated by light pressure, the force generated by sliding mass and control vanes iscarried out. The axial and transverse vibration equations with the properties ofstrong coupling, nonlinearity and time-varying coefficient matrix are established byLagrange equation method. The vibration equations are transformed into nonlinearalgebraic equations utilizing implicit unconditionally stable Newmark-β algorithmfor each time step. The nonlinear algebraic equations are solved by Newton-iterativealgorithm. Based on the analysis above, the vibration response affected by the massand velocity of the sliding mass, the angular velocity of the force generated bycontrol vanes are analyzed in detail. The computational results indicate that the massand velocity of sliding mass affect the vibration response, and the angular velocity of the force generated by control vanes hardly affects vibration response.Third, the dissertation gives the attitude dynamics for large-flexible solar sailconsidering complex mechanisms such as control boom, sliding mass, control vanes.The basic configuration and assumptions, the related reference frames, thegeneralized coordinates, the coordinate transformations are given. The position andvelocity vectors of payload, sliding mass, and support beam are derived. And thegeneralized external torque caused by control vanes is given. The attitude dynamicsequations having the properties of nonlinearity and coupling are obtained byLagrange equation method. The attitude dynamic modeling is the basis for therigid-flexible coupling dynamic analysis and control.Fourth, the dissertation carries out rigid-flexible coupling dynamics and controlstudies for solar sail. The rigid-flexible coupling dynamic equations for controllersdesign and dynamic simulations are derived based on vibration analysis and attitudedynamic modeling above-mentioned. Based on above work, the studies ofattitude/vibration control are carried out for solar sail on geostationary orbit (GEO).The controllers designed by optimal proportion and integral (PI) and linear quadraticregulator (LQR) are given for the problem of constant disturbance torque caused bythe center of pressure and the center of mass of solar sail. And the simulations andthe comparations are given. The theory analysis and simulations indicate that theLQR and optimal PI regulators can give a compromise between the dynamicresponse performance of attitude angles, angular velocities and control input torques.The PI regulator has more advantage to eliminate the steady state attitude angleserror for solar sail.