Path: SC/Dynamics
% Plant for a momentum bias spacecraft with flexible solar arrays. Computes the state space description of a spacecraft with two flexible appendages where the internal momentum is fixed. If dT is not input it returns the continuous time plant. If dT is input it returns the discrete time plant. In either case, the plant is linearized. The state vector is [thetax;thetay;thetaz;x1;...xN;omegax;omegay;omegaz;v1;...vN] Where the state vector is with respect to the rotating frame defined by wo. The outputs are the angles, i.e. the first three elements in the state vector. The flex model is in the physical frame with each mass having a vector stiffness and damping If h and wo are not in the same direction or inr is not diagonal, dxdt will be nonzero and you will get constant disturbance torques. If only one output is specified it gives the right hand side of the nonlinear dynamical equations of motion. You need to use the kinematics routines to get the nonlinear kinematics equations. Since version 1. -------------------------------------------------------------------------- Form: [a,b,c,d,dxdt] = FXModel(inr,h,wo,m,r,wF,zF) [a,b,c,d,dxdt] = FXModel(inr,h,wo,m,r,wF,zF,dT) [wDot] = FXModel(inr,h,w,m,r,wF,zF,fT,mT,v,x) -------------------------------------------------------------------------- ------ Inputs ------ inr (3,3) Inertia matrix h (3,1) Internal momentum vector wo (3,1) Orbit rate vector m (1,n) Mass of the flex masses r (3,n) Positions of the flex masses wF (3,n) Frequencies of the flex masses zF (3,n) Damping ratios of the flex masses dT (1,1) Sampling period or fT (3,1) Total external force on the spacecraft c.m. mT (1,1) Total spacecraft mass v (3,n) Flex mass velocity x (3,n) Flex mass position ------- Outputs ------- a (6+6*n,6+6*n) Plant matrix b (6+6*n,3) Input matrix c (3,6+6*n) Output matrix d (3,3) Feedthrough matrix dxdt (6+6*n,1) Steady state derivative or wDot (3,1) State derivative of rates --------------------------------------------------------------------------
Common: Control/C2DZOH Math: Linear/SkewSymm
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