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Foundation ::
Engineering Applications ::
TWOBODY
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TWOBODY
Improved Implementation of LaGrange Multiplier
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SOURCE CODE AVAILABLE
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The Lagrange multiplier method has been used for many years by engineers to develop equations of motion in multibody problems. Use of the Lagrange multiplier has an advantage over some other formulations in that it preserves the original simple form of the equations of motion for each body. However, in typical time-varying dynamics simulations that use the Lagrange multiplier, computational instability can occur because integration error causes the two (or more) attached bodies to drift apart and violate the constraints. The computational instability usually happens suddenly, and the computed values "blow up" within a few time steps.
TWOBODY utilizes a new programming technique which eliminates computational instability in multibody simulations that use the Lagrange multiplier. This new technique uses the constraint equations, instead of integration, to determine the coordinates that are not independent. TWOBODY employs a simple model, consisting of a solid rocket booster and a parachute connected by a frictionless swivel, to illustrate the new technique.
TWOBODY carries the NASA case number MFS-28774. It was originally released as part of the COSMIC collection.
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