-------------------------------------------------------------------------- Formation flying maintenance simulation. *** Notes on Usage *** The input data for this function can be created automatically for different test cases, using the "FFMaintenanceTests" function. To generate a default data structure: >> simOptions = FFMaintenanceTests; Once this function has run and the outputs have been created, use the "FFMaintenancePlotter" function to plot the data. *** Inputs *** Supply the initial state of the reference (el0) and the initial relative state (dEl0), define the desired relative motion (goals), the maneuver window (window), maneuver parameters (params), the error deadband (deadband), the noise (noise), how many orbits to simulate (nOrbits), the number of simulation points per orbit (nSPO), the disturbance options (distOpt), the cross-sectional area, mass, and the control method to use. *** Estimated Absolute and Relative States (ECI) *** The estimated absolute and relative ECI position and velocity are provided by adding noise to the true state. This emulates the data provided by a relative navigation unit. *** Estimated Relative State (Hills) *** The estimated relative position and velocity in the Hill's frame is computed via a transformation from the estimated absolute and relative ECI position and velocity. This computation is performed in the "AbsRelECI2Hills" function. *** Estimated Orbital Elements *** The estimated mean orbital elements and mean orbital element differences are computed from the estimated absolute and relative ECI position and velocity. This computation is performed in the "ECI2MeanElements" function. *** Desired Orbital Elements *** At each step in the simulation, the initial goals are used along with the current estimate of the mean orbital elements to compute the desired orbital element differences. *** Desired Relative State (Hills) *** The desired element differences are transformed to the Hill's frame, defining the desired relative position and velocity. *** Relative State Error (Hills) *** The relative position errors and relative velocity errors are computed by comparing the desired and estimated states. *** Deadband *** A constant position deadband is defined in the relative Hill's frame. It is a parallelapiped, for each side may have different lengths. If the relative state error exceeds 75%% of the deadband "box" in any axis, a maintenance maneuver is planned. *** Maneuver Planning *** The "ImpulsiveManeuver" function is called when the deadband is exceeded, and when no other maneuver is pending. It is supplied with the current estimate of the orbital elements, the formation goals, and a set of parameters. It solves for a burn sequence, consisting of the in-plane and out-of-plane delta-v's required to eliminate the error in the mean element differences, as well as the times at which to apply the delta-v's. *** Delta-V *** A delta-v is introduced by applying a constant thrust over a finite amount of time. The times at which thrust is applied is determined by the burn sequence, which is provided by the ImpulsiveManeuver function. Since version 7. -------------------------------------------------------------------------- Usage: simData = FFMaintenanceSim( simOptions ); -------------------------------------------------------------------------- ------ Inputs ------ simOptions (.) Data structure with the following fields: - el0 (1,6) Initial reference orbital elements (Alfriend format) [a,theta,i,q1,q2,W] - dEl0 (1,6) Initial orbital element differences (Alfriend format) - goals (.) Goals data structure defining desired relative motion - window (.) Data structure defining the desired maneuver window - params (.) Data structure defining several maneuver parameters - deadband (1,3) x,y,z dimensions of the position error deadband "box" - noise (1,4) Standard deviation of noise for the following sources: noise(1) - absolute position [m] noise(2) - absolute velocity [m/s] noise(3) - relative position [m] noise(4) - relative velocity [m/s] - nOrbits (1) Number of orbits to simulate - nSPO (1) Number of simulation points per orbit - distOpt (1,3) Disturbance options (flags) (1) solar: whether to simulate with solar pressure or not (2) drag: whether to simulate with drag or not (3) J2: whether to simulate with J2 or not - mass (1,2) Mass of reference and relative [kg] - aera (1,2) Cross-sectional area of reference and relative [m^2] - controlMethod (1) Which control method to use: - closed form solution (1) - linear programming (2) ------- Outputs ------- simData (.) Simulation output data structure with the following fields - time (1,:) Time vector [orbits] - fH (3,:) Applied thrust in Hills frame [kN] - rE (3,:) True ECI position of reference - vE (3,:) True ECI velocity of reference - rE_est (3,:) Estimated ECI position of reference - vE_est (3,:) Estimated ECI velocity of reference - rH (3,:) True Hills-frame relative position - vH (3,:) True Hills-frame relative velocity - rH_est (3,:) Estimated Hills-frame relative position - vH_est (3,:) Estimated Hills-frame relative velocity - rH_des (3,:) Desired Hills-frame relative position - vH_des (3,:) Desired Hills-frame relative velocity - dElMean (6,:) True mean element differences - dElMean_est (6,:) Estimated mean element differences - dElMean_des (6,:) Desired mean element differences - elRefMean_est (6,:) Estimated mean elements of reference - fDiffDragH (3,:) Hills-frame differential drag force - fDiffDragE (3,:) ECI-frame differential drag force - fDiffSolarH (3,:) Hills-frame differential solar force - fDiffSolarE (3,:) ECI-frame differential solar force - fDiffJ2H (3,:) Hills-frame differential J2 force (apparent) - fDiffJ2E (3,:) ECI-frame differential J2 force (apparent) - deadband (1,3) Size of the position error deadband "box" (same as input)

AeroUtils: AtmosphericCalculations/AtmDens2 AeroUtils: Coord/QHills Common: Control/C2DZOH Common: Database/Constant Common: Quaternion/QForm Common: Quaternion/QTForm Common: Time/JD2000 Common: Time/JD2T Common: Transform/Altitude Common: Transform/RPhiTheta2Cart FormationFlying: Analysis/FFMaintenancePlotter FormationFlying: Analysis/FFMaintenanceTests FormationFlying: Control/ImpulsiveLPManeuver FormationFlying: Control/ImpulsiveManeuver FormationFlying: Control/LinOrbLQG FormationFlying: Coord/IsCircGeom FormationFlying: DataStructures/PlanningParameters_Structure FormationFlying: DataStructures/Window_Structure FormationFlying: Transformation/AbsRelECI2Hills FormationFlying: Transformation/DeltaElem2Hills FormationFlying: Transformation/ECI2Hills FormationFlying: Transformation/ECI2MeanElements FormationFlying: Transformation/FFEccDeltaElem2Hills FormationFlying: Transformation/FFEccGoals2Hills FormationFlying: Transformation/FFEccHills2DeltaElem FormationFlying: Transformation/Goals2Hills FormationFlying: Transformation/Hills2DeltaElem Math: Integration/RK4 Math: Integration/RK4TI Math: Linear/Mag Math: Linear/Unit Orbit: GravityModels/LoadGravityModel Orbit: OrbitCoord/Alfriend2El Orbit: OrbitCoord/OrbElemDiff Orbit: OrbitMechanics/AGravity OrbitMiniToolbox: Support/EarthRot OrbitMiniToolbox: Support/El2RV OrbitMiniToolbox: Support/M2Nu SC: BasicOrbit/OrbRate SC: BasicOrbit/RV2El SC: Disturbances/SolarF SC: Ephem/Eclipse SC: Ephem/SunV1