[PART, 1.0.2] Anatid Robotics / MuMech - MechJeb - Autopilot - Historical thread

[Galane]

I just used the PAR function for the first time. To keep one rover from drifting off while replacing the rover stacked in the middle, I docked it to a port on the side of the ship's core before undocking and landing the kethane conversion rover to land and recover.

After bringing up the replacement conversion rover (with moar quantum struts on its Rockomax decouplers) and getting it docked butt end first after first nose to nose docking to transfer fuel and mono from the booster - I undocked the other rover then gave it a little boost away with RCS.

Once it was far enough off, I slowed up with a counter-burst then used PAR+ to rotate so I could use RCS to thrust towards the nose of the ship. Then I set control to the bottom docking port and used TGT- so it'd point away from the target port. I then started thrusting forward a bit so the rover would cut across the nose for easy docking.

Once out in front, I shut off SASS and enabled the docking AP with force roll. Had it docked real quick.

Now I just have to bring up the two replacement sidesaddle boosters with their larger mono supplies. Might replace the other two as well to further reduce part count and increase mono supply.

What I did have a problem with on MJ is landing that rover. After it did the initial deobit burn it kept flipping this way and that, constantly doing corrections and overshooting about 100%. It settled down when I clicked abort autoland then immediately clicked VAB and land at target. It did one more correction burn then settled down to a proper landing, but missed the VAB, landing on the track between it and the pad. Oh well, down safe!

I've noticed this same overcorrect this way, then that way, then another way on craft with the ability to rotate quickly. Aborting the landing then enabling it again settles it down, but with even the briefest interruption the target tends to be missed a bit.

Put together a 48-7S, Oscar B with a couple OX-STATs and an OKTO2 and try telling it to land. When the overcorrection kicks in it'll burn all its fuel quickly doing 100+ m/sec "corrections" and end up in a skewed orbit instead of just burning retrograde then doing a minor correction or two. (I was using these as deorbitable controls to dock the sidesaddle boosters, then attempting to hit the VAB with them.)

If the correction function could be reset without interrupting the targeting... or if it had a self-check on whether or not it was commanding way out of needed range correction burns...

[Commissar]

wen doing a planetary transfer, does mechjeb compensate for gravity assists from the mun or minmus? I had an issue today where I had an... uncompensated gravity assist from the mun, which put me 500m/s deltav off target for duna, rather than the normal 10-50 m/s

[sarbian]

I finally found the time and will to get back to work on the new Docking AP and I just committed it. It's now available in dev #171.

"Conserve RCS fuel" is now disabled by default. It was harmful for the docking process.

Current version worked fine for my light and heavy test ship. I hope it does the same for you.

I did not test it with the RCS Balancer on but it should works too.

It also gets a bit far from the target to get on it's correct side. I have a correct bounding box for both the target and the ship but right now I use a quick hack to get far enough.

The whole getting on the right side is not perfect either, but for most use I think it will works fine (starting from one dock of an object to move to an other does no always choose the less dangerous way).

I'll let you test and wait for your feedback. Next I'll have to read back the last month of the thread to remember what else I need to work on

[codepoet]

Next I'll have to read back the last month of the thread to remember what else I need to work on

I am really curious as to what you have been working on in the last month. Perhaps it has been announced and I have missed it, or perhaps I just have to be patient for a bit longer!

[LameLefty]

I am really curious as to what you have been working on in the last month.

Ditto. It's been rewarding and that we get to hear about it soon.

[sarbian]

Should be out this week. It won't be that much code since I spent most of those week building and trashing code prototype.

Don't forget I spent a lot of time on the docking AP too. In the end having a break helped since I found out the problems quite fast today.

[Virtualgenius]

Its good to step away sometimes as you can look at a problem and not see it then come back and its starring you in the face and you see it straight away

[boywithumbrella]

as my question apparently got buried, I'll try once more:

If you mean they don't work with the rover AP then it most likely because they don't use the stock control scheme for wheels.

Yes, I mean the rover AP. Could you elaborate? From what I see as user, in "Rover Mode" the Multiwheels respond to the rover controls I set up in settings (WASD as default, as well as my joystick bindings) - is there another level where the control scheme is customized / can differ?

Seeing as Multiwheels have not been updated since 0.21 asking for a compatibility patch by either you or TT would probably be pointless; but it's a pity, because I really like those wheels and would also like to use the rover AP.

[Commissar]

also, the maneuver planner autopilot suddenly decided that I can go through kerbin on my way to duna, and burned 10 minutes early... and in the wrong direction... twice....

I caught it the second time, and remade the node...

Edited February 17, 2014 by Commissar

[OrbitalDebris]

@Sarbian

Just done taking out the new MJ out for a spin, just a quick "put a ship in orbit and dock" exercise. Everything went pretty well, but the new work on the docking AP really shows - much saner use of RCS, I'd even say it passes the Turing test Great job!

[DerekL1963]

I'll let you test and wait for your feedback. Next I'll have to read back the last month of the thread to remember what else I need to work on

Looks like lots of good stuff, will give 'er a spin when I'm done with forums - and I have a mission queued that needs docking too!

While you're fixing stuff, could you look into the autoland program? When it has to make a plane change, it doesn't resume autowarp afterwards.... very annoying when the deorbit burn is half an hour away.

[sharpspoonful]

I'd hate to ask a question with a simple answer, but can someone point me to the icon pack for Blizzy's toolbar integration? I've looked in both of his threads and cannot find a DL.

[Virtualgenius]

http://forum.kerbalspaceprogram.com/threads/60933-Optional-MechJeb-Modules

If your looking for stuff that Sarbian has created he generally has it in his signature block

Edited February 17, 2014 by Virtualgenius

[Mystique]

also, the maneuver planner autopilot suddenly decided that I can go through kerbin on my way to duna, and burned 10 minutes early... and in the wrong direction... twice....

Maybe your TWR was pretty low and planner had to split burn time in 10 minutes before and 10 minutes after node. That may result in such a situation, especially if starting orbit was low enough to be unable to compensate such a burn.

[K3-Chris]

Yeah it's not a bug, it's mis-use of MJ, it can't compensate for really low TWR + low orbit, if you want to leave kerbin with TWR that low you need to manually burn multiple times, you can't complete the burn in one orbit, either increase your TWR or raise your orbit if you want to use MJ to do your escape burn.

[Carraux]

When creating a node (e.g. transfer to another planet) the node cross dances wildly on the nav-ball, showing varying burn times. For me it's pure luck to catch the one with the lowest delta-v. And for today, my ship is not able to align with the node cross at all, making it impossible to travel to another planet.

Any ideas?

[sarbian]

es, I mean the rover AP. Could you elaborate? From what I see as user, in "Rover Mode" the Multiwheels respond to the rover controls I set up in settings (WASD as default, as well as my joystick bindings) - is there another level where the control scheme is customized / can differ?

Seeing as Multiwheels have not been updated since 0.21 asking for a compatibility patch by either you or TT would probably be pointless; but it's a pity, because I really like those wheels and would also like to use the rover AP.

as my question apparently got buried, I'll try once more:

I'd have to look at TT code but I don't think it uses the "native" way of controlling rover since it existed before wheel were added to stock.

Carraux : AFAIK your problem is not related to MJ. Stock does the same.

[Mystique]

When creating a node (e.g. transfer to another planet) the node cross dances wildly on the nav-ball, showing varying burn times. For me it's pure luck to catch the one with the lowest delta-v. And for today, my ship is not able to align with the node cross at all, making it impossible to travel to another planet.

Any ideas?

Node dances can be caused by:

1. Too ideal circular orbit of your ship (usually it also causes apo- and periapsis to make some hip-hop moves);

2. Node is too precise; e.g. you're trying to make 20 m/s delta-v burn to make your orbit at target planet precisely at some altitude. It's so precise, that your ship's movements and maybe even some calculation tolerances make game unable to decide where exactly you should be pointing at to burn.

3. Your ship may be wobbling, which causes about the same problem as in p. 2.

Any more details on your situation? And, as sarbian just wrote, it's game's behavior, not MJ's.

[vardicd]

I just downloaded the newest dev build of this, scansat mod, and distant objects mod, and suddenly I can't access my menu in game with the escape key, and my ability to time warp is gone, but mechjeb can still timewarp on its own, I'm wondering if this is an issue caused by mechjeb, I'm testing it now by pulling the mods out one at a time, just thought I'd post here to see if anyone else has noticed.

[Carraux]

Node dances can be caused by:

1. Too ideal circular orbit of your ship (usually it also causes apo- and periapsis to make some hip-hop moves);

2. Node is too precise; e.g. you're trying to make 20 m/s delta-v burn to make your orbit at target planet precisely at some altitude. It's so precise, that your ship's movements and maybe even some calculation tolerances make game unable to decide where exactly you should be pointing at to burn.

3. Your ship may be wobbling, which causes about the same problem as in p. 2.

Any more details on your situation? And, as sarbian just wrote, it's game's behavior, not MJ's.

Ok, thank you for the clarification.

I will try a less circular orbit (and a ship which wobbles less, although it's quite stable)...

[Mystique]

Ok, thank you for the clarification.

I will try a less circular orbit (and a ship which wobbles less, although it's quite stable)...

Orbit is the main issue, MJ tends to do things mathematically perfectly and game then can't decide which point of orbit is highest or lowest. Same thing goes for inclination when you intercept a target. BTW, it may generally help to increase tolerance a bit in maneuver planner, I usually put 0.3-0.5 m/s. This way MJ won't make sudden moves at the end of the burn trying to catch "escaping" node to make such a precise corrections and it won't make thing THAT perfect.

[Starwaster]

Ok, thank you for the clarification.

I will try a less circular orbit (and a ship which wobbles less, although it's quite stable)...

Orbit is the main issue, MJ tends to do things mathematically perfectly and game then can't decide which point of orbit is highest or lowest. Same thing goes for inclination when you intercept a target. BTW, it may generally help to increase tolerance a bit in maneuver planner, I usually put 0.3-0.5 m/s. This way MJ won't make sudden moves at the end of the burn trying to catch "escaping" node to make such a precise corrections and it won't make thing THAT perfect.

There's a setting in Maneuver Planner that controls how precise MJ tries to make its burns in m/s. The default is pretty low 0.5? 0.05? Setting it higher will let MJ decide 'ok that's close enough' which will also stop that bit where it keeps turning 180 to trim the delta-V because it overshot. Of course sometimes you do want accuracy such as for re-entry burns in which case you you either impose throttle limits or use RCS to manually trim your velocity.

Hyper Edit also makes precise orbits btw

Edit: And WOW. See this is why Starwaster shouldn't post before his morning coffee. I totally said the same dang thing as one of the people I quoted just rephrased. Sorry Mystique.

Edited February 17, 2014 by Starwaster

[Starwaster]

observations re: build 179

Overall improvement in some areas including coasting instead of constant thrusting.

Better RCS fuel consumption (see above)

Avoids moving forwards until near docking axis but not quite on axis so can still hit dock at angle.

Now the bad: Easily confused if asked to start when controlling port is facing away from target.

On my first attempt I had either the wrong target port or wrong controlling port and the craft started thrusting away on RCS until I shut it off and approached the target manually. (MJ increased distance by over 200 meters)

If I undock and change ports (target and/or control) and engage AP it does not back off from the target port or axis. Such close proximity combined with the need for rotation should trigger backing off. It might back off a little but typically starts 'move forward' while still too close and before rotation (to face target) is complete.

I use identical standardized docking targets for testing. Basically a probe core with tanks on each end, solar panels and ports on the tanks. RCS on the probe core 1 set or 2 sets on each tank.

[K3-Chris]

Some bugs I have with the current dev build, some of them I've had for a while:

MJ just oscillates when you detach the root object from the ship until you set "control from here" on something, a bit weird since the game on it's own defaults the control to a pod hence the nav-ball still working.

Enabling the ascent autopilot on the pad can sometimes make MJ take off on it's own, sometimes not, it's weird. (Same craft, no control input from me before enabling ascent ap (staging, throttle etc)).

[sarbian]

Thanks for the detailed feedback Starwaster. I'll what I can do for those