[0.24] Gimbal Auto Trim 1.1 (Sept 2)

[sarbian]

looks fine.

[colmo]

I appear to be missing something - the gimbal doesn't appear able to keep things remotely stable. It might be the rough spaceplane + booster I threw together to test. Does the craft have to be nearly balanced to have a hope?

[sarbian]

Did you replace the default gimbal with a MM patch ? Did you see the engine turn more than the default gimbal ?

It's not a magic fix and it has an impact to how your ship fly.

Yes, your ship need to be somehow balanced if you want it to be still flyable. Changing the direction of thrust may help with some thing but it may makes other things worse since your direction of thrust is not aligned with the "up" of your ship.

Some design fly better with it, some fly worse. I should make a nice graph to explain why

[colmo]

Did you replace the default gimbal with a MM patch ? Did you see the engine turn more than the default gimbal ?

It does...sometimes. The usual result is the ship inverting itself and crashing into the launchpad, or else not compensating enough and arcing low over the ground to crash a kilometre away.

It's not a magic fix and it has an impact to how your ship fly.

Yes, your ship need to be somehow balanced if you want it to be still flyable. Changing the direction of thrust may help with some thing but it may makes other things worse since your direction of thrust is not aligned with the "up" of your ship.

Some design fly better with it, some fly worse. I should make a nice graph to explain why

It's not quite the magic box of tricks the thrust balancing mods are (it's always best to have the thrust vector pointed retrograde!). My expectations were perhaps too high.

Edited April 28, 2014 by colmo

[Pondafarr]

Trying to wrap my head around the mechanics.

OP sates: When activated on one or more engines they will orient themselves so the Direction of Thrust stays aligned with the Center of Mass. (Sarbian 1)

Does this mean the individual engine's thrust vector, or the ship's combined thrust?

This could be important when designing a puller-type Nuclear Asteroid Tug...my fuel tanks are aft of the engines, so CoM is also aft of the engines. Once I'm locked onto the asteroid, I expect the function should be "normal" due to CoM shift.

Please elaborate the mechanics as if you were talking to a slow 5-year old (extra points for MS Paint drawings)

Thanks!!

[sarbian]

The engine with auto trim active moves so the combined thrust of all the engines will be aligned with the center of mass.

I'll do the painting later

[Pondafarr]

Perfect! That means there is no functional difference for tractor or pusher configurations. i can keep my Asteroid Tug en route to my first capture

Sarbian, you are DA MAN!

[Pondafarr]

Ok, I have a problem, Auto Gimbal must think my CoM is outside the ship. the ship operates normal without the plugin enabled, and autotrim is WAY out of calibration when enabled.

any known fixes? (this ship was assembled in orbit, so I don't have a single craft file)

Auto Gimbal NOT engaged:

Auto Gimbal engaged:

[sarbian]

I may have an idea (I m doing stupid things with symmetry). I'll build a test version tomorrow.

Even if you don't have the ship, could you put your save somewhere ? (the persistent.sfs file in the save folder)

Edited April 30, 2014 by sarbian

[Pondafarr]

trying dropbox for the first time, hope this works...damn, that file is 7.6 meg...

Craft is called "Grabber 1", and yes, i know I made a few errors (forgot to add enough Mono to Grabber 1, so had to send Grabber 2 to upgrade), otherwise I would not have had so many engines. Next iteration will be cleaner. My symmetry should be ok though...no extra fuel tanks show in TAC Fuel Balancer.

https://www.dropbox.com/s/itiz46x7b494hdo/persistent.sfs

Grabber 1 (Ship core)

https://www.dropbox.com/s/8ixhe6hxtcqvykn/Grabber%201.craft

Grabber 2 (Aft Engine Pod)

https://www.dropbox.com/s/aib6v0yrxkfzjzu/Grabber%202.craft

Edited April 30, 2014 by Pondafarr

[anything]

maybe im doing it wrong also

made a basic symmetrical 4 engine ultra-wide test rocket, disabled one engine, and it seems to flip even more out of control than without the auto gimbals.

[sarbian]

I found out the problem. It does that when the Center of Thrust is in front of the Center of Mass.

I fixed it but I want to add a few more things before I release a new version.

[Zeroignite]

Oooh. Hm, would it be possible to use something like the "control from here" for the vectored axis of the engines, so an off-center craft goes the direction you point it on the navball?

[Pondafarr]

Awsome Sarbian! I can live without the auto gimbal for a few days, but I'm sure I'll need it once I reach this 'Roid I'm chasing

[quantumpion]

Aside from shuttles, will this mod make regular craft which are slightly off balance easier to control? E.g. a tiny probe unbalanced due to a science instrument on one side?

[Pondafarr]

Thats the idea...it adjusts the center of thrust to align with the center of mass. So, if your probe is slightly out of balance, it should trim the engine to correct for the imbalance. I would suggest two things: ensure your center of thrust is aft of the center of mass, and setting max trim to a low number, 1-5 degrees, or you may end up with the neat trick I described above (at least until the next version comes out)

[quantumpion]

Does the mod correct the navball so that if you have a craft where the line of thrust through the COM is not parallel to the command module's prograde direction, the craft's acceleration will be in the expected direction and not slide off course?

[Pondafarr]

AFAIK, no. The nav ball is a controlled by wherever you have "control from here" enabled. This mod focuses on the COM and COT.

[quantumpion]

Is it possible to add a tweakable option to control a craft from its center of thrust?

[kujuman]

Is it possible to add a tweakable option to control a craft from its center of thrust?

I imagine this would be possible, but it would be a bad idea. With CoT moving everytime you make a control input, there are going to be really bad feedback loops in the control (like when you "Control From Here" on a really wobbly part ). A much better solution would be to add a node on the NavBall displaying the current CoT. Hmmm, time to head over to the Enhanced NavBall thread...

[EDIT: Back from thread]

I did some proof of concept work, using something like enhanced NavBall would work pretty well. Of course, your CoT solver looks (I only glanced at the code) way better than the solver I used (the one KSP uses in the VAB and SPH).

http://forum.kerbalspaceprogram.com/threads/50524-0-23-5-Enhanced-Navball-1-2?p=1138899&viewfull=1#post1138899

Edited May 5, 2014 by kujuman

[quantumpion]

Hmm, your ideas are intriguing to me and I wish to subscribe to your newsletter.

[whaaw]

hello my log is full of this:rgumentOutOfRangeException: Argument is out of range.

Parameter name: index

at System.Collections.Generic.List`1[unityEngine.Transform].get_Item (Int32 index) [0x00000] in <filename unknown>:0

at GimbalAutoTrim.ModuleGimbalAutoTrim.updateThrust () [0x00000] in <filename unknown>:0

at GimbalAutoTrim.ModuleGimbalAutoTrim.OnFixedUpdate () [0x00000] in <filename unknown>:0

at Part.ModulesOnFixedUpdate () [0x00000] in <filename unknown>:0

at Part.FixedUpdate () [0x00000] in <filename unknown>:0

(Filename: Line: -1)

i have alot of mods installed can i ignore this?

[Pondafarr]

My first response would be:

Does your ship go where you want it to go?

[sarbian]

It's not good but won't make anything but the plugin fail. I need to take more time to fix that and the math (math currently does not works for all cases)

[FellipeC]

Epic win! BTW Mechjeb could account for the direction of thrust dont being exact in center, like in shuttles.