As the title said, how come FGFS's PIDs don't use Ki or Kd?
I know PI simple has Ki.
it0uchpods wrote in Thu Jan 26, 2017 6:01 pm:Care to explain more about normal equations?
Soitanen wrote in Sun Jan 29, 2017 11:16 am:Sure, I'll show in reverse direction.
This chain is stable independent on any mode (VS, LVL CHG or something else). You just feed target VS into calculation and get aircraft follow this value.
4. This is calculation of vertical speed. It depends on selected AFDS mode. Simpliest - just VS hold.
If we say about LVL CHG, I use relationship between TAS, alpha, total thrust and total drag, weight of aircraft and target speed difference. You can see example in 738 737-fcc-a.xml lines 485-527. No PID. Earlier I used PID for this, but it's good for automatic, but bad for FD mode. If you don't follow FD bar very good, it start to go somewhere in bad position, due to nature of PID controller.
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