Path: LunarMissions/LunarLanding
% Implements a 2nd order guidance law in 3 dimensions
Uses a 2nd order controller to provide guidance for landing.
Demonstrated in a cartesian system.
'initialize' computes the time to land from the tolerance.
'update' updates the control accelerations.
You generally want zeta to be 1. Lower omegas will reduce the control
accelerations. An omega of 0.01 gives roughly the Apollo LM landing
guidance. If it is much lower you can overshoot and then have to return
to the landing site.
Type SecondOrderGuidance3D for a demo of lunar landing. This replicates
the demo in SecondOrderGuidance.
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Form:
d = SecondOrderGuidance3D
a = SecondOrderGuidance3D( action, x, d )
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Inputs
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action (1,:) 'initialize' or 'update'
x (6,1) State [r;v]
d (.) Data structure
.x (6,1) Target [r;v]
.tol (1,1) Tolerance for damping
.zeta (1,1) Damping ratio
.omega (1,1) Undamped natural frequency (rad/s)
.t (1,1) Time to damp
.rP (1,1) Equatorial radius
.mu (1,1) Gravitational constant
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Outputs
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a (3,:) Control accelerations
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AerospaceUtils: Coord/DownrangeAndAltFromTarget AerospaceUtils: Coord/TargetFromRPVD Common: Database/Constant Common: Graphics/NewFig Common: Graphics/Plot2D Common: Graphics/TimeLabl Common: Graphics/XLabelS Common: Graphics/YLabelS Math: Integration/RK4 Math: Linear/Mag Math: Linear/Unit
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