Control Surface Rotation Speed

[AngryBaer]

When flying smaller craft I have the impression that the control surfaces move much too quickly. This could be the cause of excessive over-compensation by the SAS.

Here is my craft with SAS after a climbing maneuver without any inputs. While I could reduce the Authority Limiter I wish there were a "Dampening" or "Rotation Speed" slider as well .

Looking through the Forum I found that this topic has already been  asked in KSP1 and I believe this may be a very similar issue:

I considered a bug report such as this one, but perhaps this could be solved by simply having the control surfaces rotate slower.

 

Edited June 30, 2023 by AngryBaer
typo

[Sea_Kerman]

The issue is actually mis-tuned PIDs. Too much gain, or too little damping. Making the control surfaces slower might actually make the problem worse, because then the PID (if it were tuned correctly) wouldn’t be able to react as quickly and accurately.

Edited June 30, 2023 by Sea_Kerman

[AngryBaer]

7 hours ago, Sea_Kerman said:

 Making the control surfaces slower might actually make the problem worse...

How interesting and unintuitive. Turning off SAS entirely in these situations makes it quite a bit more stable for me. I wonder if it would make sense to then take the control surfaces off of SAS and only let the reaction wheels stabilise.

Though I suppose jets don't usually have those in reality.

[dr.phees]

In my experience the vectoring of the jets is even worse. Try to take those off SAS / disable pitch vectoring. Sometimes it helps

 

By the way: I always hoped that KSP 2 would check for oscillations when using SAS and switch through a couple of PID tunings to get rid of it or at least let us manually switch between a couple. Would have been nice.

Maybe there is a way to do it via modding at some point.

Edited July 1, 2023 by dr.phees

[Lyneira]

This isn't strictly only about control surfaces but related... It would be nice to be able to control the speed at which rotation inputs change when you tap keys on the keyboard repeatedly. KSP1 had this and it makes for much smoother control of a plane while you're tapping control keys to adjust its heading.

Edited July 10, 2023 by Lyneira

[KUAR]

On 6/30/2023 at 6:00 AM, AngryBaer said:

When flying smaller craft I have the impression that the control surfaces move much too quickly. This could be the cause of excessive over-compensation by the SAS.

If you're not already aware, pressing CAPS LOCK limits the deflection of the control surfaces to an extent better suited to planes rather than rockets. It's not exactly what you're after, but it may help.

[dr.phees]

It is the old problem of KSP 1 again. If SAS is on, input should add/subtract an offset to or from the PID's target or a rotational target speed, not 'switch off' SAS until input stops.

Alternatively SAS could work by shifting trim instead of simulating steering input. While steering input is received, SAS should stop adjusting trim until input is released.

Both solutions would give us smooth steering.

This had been discussed so unbelievably often with KSP 1 and should be very obvious.

Edited July 11, 2023 by dr.phees

[AngryBaer]

10 hours ago, dr.phees said:

If SAS is on, input should add/subtract an offset to or from the PID's target or a rotational target speed

That sounds very reasonable. I'm wondering if the excessive wobble on large rocket builds is also a result of this behaviour, rather than purely joint strength.

I imagine joystick inputs would give a lot better results by having a gradient rather than jumping to 100% deflection like the keyboard. I'm sure the build can be tweaked to perform better in these high speed situations but what would really help there is the robotics controller so you can scale multiple values at once.