Comment by zlsa
5 years ago
I believe this is what the engines are doing during the majority of the ascent of the Starship SN8 test vehicle[0]. You can see the engines gimbaling very slightly in a circular pattern.
5 years ago
I believe this is what the engines are doing during the majority of the ascent of the Starship SN8 test vehicle[0]. You can see the engines gimbaling very slightly in a circular pattern.
Anything controlled by a PID can easily end up in a circular pattern, so it's not a given that this was to avoid stiction.
[edit]
1 dimensional PIDs can end up in a sinusoidal dynamic equilibrium, and a 2 dimensional sine wave is an ellipse.
It's not an ellipse if the axes have different periods: https://www.wolframalpha.com/input/?i=x%3Dsin%28t%29%2C+y%3D...
(Is there a name for this kind of curve?)