SAS Pointing

[qzgy]

Hello. I have noticed that the SAS has not been very good at pointing to manuver nodes, targets, and so on recently. There would be a large amount of drift or stuttering. Has anyone else noticed that?

Edited August 15, 2016 by qzgy

[Brainlord Mesomorph]

I've had a strange issue w/ SAS lately. Sometimes the ship would start to drift off-course and the SAS wouldn't do anything about it. 

Not being unable to move the ship, or overcompensating (like usual) but not even trying. I was wondering if it was deliberate, to simulate low-tech unreliable SAS units and/or untrained pilots.

 

[suicidejunkie]

This gimbal lock has happened occasionally to me.  If you're not in the middle of aero or a time-critical landing/docking maneuver, you can switch to the space center and back to resolve it.

[Corona688]

57 minutes ago, qzgy said:

Hello. I have noticed that the SAS has not been very good at pointing to manuver nodes, targets, and so on recently. There would be a large amount of drift or stuttering. Has anyone else noticed that?

Could you be more specific?  I've noticed some things but have no idea if they're the same ones you have.

Mostly, I've noticed issues from attempting off-center 'control from here' stuff.  It may disagree with the engines on which way is left.  This is especially pronounced when you've got vectored engines mounted above the center of mass.  Related, I've never seen 50 tons spin that fast.

 

Edited August 15, 2016 by Corona688

[Red Iron Crown]

Any SAS mode other than stability assist results in stuttering corrections for me. It's most noticeable if you have control surfaces or a gimballed engine, you can watch it dance after getting close to target.

The workaround I use is to use the advanced mode to get aligned, then switch to stability assist.

[Corona688]

21 minutes ago, Red Iron Crown said:

Any SAS mode other than stability assist results in stuttering corrections for me. It's most noticeable if you have control surfaces or a gimballed engine, you can watch it dance after getting close to target.

Oh, THAT kind of stuttering.  I thought OP meant the jittering one gets when velocities are low.

That's kind of intentional, I think -- 'target' mode reacts more sharply than generic 'stabilization'.  I noticed this when doing re-entries on battery power -- reaction wheels will burn battery power at a fearsome rate when you tell the pilot to stay retrograde.  But on small craft it also does a terrific job of balancing the needle on its tip.  I've even used it for unicycle rovers and the like.

If you have gimballed engines, I suggest turning off reaction wheel and reducing gimbal range.  You can't tune the pilot, but you can tune most other things.

Edited August 15, 2016 by Corona688

[Red Iron Crown]

1 minute ago, Corona688 said:

That's kind of intentional, I think

I really don't think it is. This is the kind of thing mentioned in the devnotes when they talk about fixing SAS.  

[Corona688]

Well, I'd hoped it was intentional as in some ways it is better.  I'd hate for them to make it weaker or less responsive unless you can tune it back to where it was.

[magnemoe]

39 minutes ago, Red Iron Crown said:

Any SAS mode other than stability assist results in stuttering corrections for me. It's most noticeable if you have control surfaces or a gimballed engine, you can watch it dance after getting close to target.

The workaround I use is to use the advanced mode to get aligned, then switch to stability assist.

Yes, its also very noticeable if you have high torque / weight, just an MK1 can with probe is enough to vibrate.
It also uses lots of power, this is an major issue if you try to land something back on kerbin, you better have multiple small batteries, or power, you run out of power during decent if you set it to retrograde. Mechjeb smartass uses way less power as its smother. 
Only place I use point retrograde is at the last part after heating effects are gone and you want to reduce drag to get a few km closer to spaceport.