- Eliminate the algebraic loops
- Do not motion actuate a joint that has no inertia associated with it
Dynamics Simulation Inconsistencies in Simscape Mechanics Model
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I have been trying to model a TVC (Thrust Vectoring Control) system for a rocket (here is the link to the model: https://drive.google.com/drive/folders/1X3DG-Q__4w9lHSB3q2t2yg57n5Tu-Lx2?usp=sharing), and doing so i have found two main issues that may contradict the laws of phisics:
- If I apply a constant force to the inner gimbal parallel to its main axis, and impose a constant deviation of the inner gimbal angle respective to the actual rocket (via a revolute joint), the simulation shows the rocket rotating almost in a sinusoidal way, thus changing the diretion of rotation periodically instead of rotating all the time in the same direction.
- The second issue I find is that, if instead of applying the force paralel to the inner gimbal, I impose no joints between the differents gimbal parts (therefore making a solid), and apply the force in an angle, the simulation shows the rocket rotating all the time in the same direction but there are no oscilations in the altitude (Y) and X position graphs, as if the thrust is not pushing the rocket when it is upside down or rotated 90 degrees etc.
Thanks in advanced
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Answers (1)
Steve Miller
on 4 Jun 2021
Hi Vicente,
I downloaded your model and ran it. I didn't quite follow your explanation, but there are some improvements you can make to the model.
These two issues are tied together - you have motion actuation on the Cartesian Joint which has no inertia associated with it.
I think you are trying to place a camera that will follow the rocket using the Cartesian Joint.
As for the other points you raised, I see the rocket spinning as you expected it to, and not oscillating. If you can add some plots and an animation to explain what is different than what you expected, we can help further.
--Steve
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