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

r4m0n

By r4m0n
in KSP1 Mod Releases

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King Arthur

King Arthur

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Has anyone else had an issue where MechJeb is at the end of executing a maneuver, and when it gets down to, say, 0.3m/s left it starts chasing the blue marker around the HUD? Sometimes it won't have to chase the marker and just leaves the engines stuck on with only that 0.3m/s left to go.

The underlying cause is actually with KSP itself. You will notice if you fly the manuever node yourself that the node will start to wobble around towards the end of the burn (starting from ~0.3m/s left as you said), MJ is simply trying to follow the node as it wobbles due to reasons completely unrelated to MJ itself.

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Valley

Valley

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Is there anyway MJ 2 can dock without RCS? I was watching the Spirit Of Kerbin Youtube series and those tiny carrier fighters were amazing...and I don't think they used RCS if I remember right. When dealing with tiny ships is there anyway for MJ 2 to use just allow itself to aim, use the main engine lightly and to float into a docking ring? I am trying to design as small as ship as I can and RCS and the fuel to run them is something I would like to do without.

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Morlock

Morlock

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Has anyone else had an issue where MechJeb is at the end of executing a maneuver, and when it gets down to, say, 0.3m/s left it starts chasing the blue marker around the HUD? Sometimes it won't have to chase the marker and just leaves the engines stuck on with only that 0.3m/s left to go.
The underlying cause is actually with KSP itself. You will notice if you fly the manuever node yourself that the node will start to wobble around towards the end of the burn (starting from ~0.3m/s left as you said), MJ is simply trying to follow the node as it wobbles due to reasons completely unrelated to MJ itself.

I do not think that is not a problem of MJ. MJ has an attitude control problem. Here's a mod that fixes this:

MJ2 with "in test" patch (last 8 aug 13) : http://www.sarbian.com/sarbian/MechJeb2.dll / Source : https://github.com/sarbian/MechJeb2/tree/Raf04_Sarbian

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Resender

Resender

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OK,the one problem I currently have.

I got an Apollo style mission ,so i unlock the lander and turn around to pick it up with the command section.

I align the hatches for easy eva,I enable autodock (either mechjeb or orda) a few meters before docking the command module makes a 45° spin.

Anybody who can give an explanation

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DerekL1963

DerekL1963

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OK,the one problem I currently have.

I got an Apollo style mission ,so i unlock the lander and turn around to pick it up with the command section.

I align the hatches for easy eva,I enable autodock (either mechjeb or orda) a few meters before docking the command module makes a 45° spin.

Anybody who can give an explanation

Do you have your MJ box mounted at an angle? Did you click on the docking port on the active craft and select "control from here" and select the proper docking port on the passive target?

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Yedin

Yedin

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Ok, thanks, I'll give this a shot in a minute.
I do not think that is not a problem of MJ. MJ has an attitude control problem. Here's a mod that fixes this:

MJ2 with "in test" patch (last 8 aug 13) : http://www.sarbian.com/sarbian/MechJeb2.dll / Source : https://github.com/sarbian/MechJeb2/tree/Raf04_Sarbian

I tried maneuvering around in a clean install of KSP, with a stock Orbiter 1A craft, and I couldn't get below around 4.0m/s without the marker going haywire in some direction. So this issue happens even without Mechjeb.

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Castun

Castun

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I tried maneuvering around in a clean install of KSP, with a stock Orbiter 1A craft, and I couldn't get below around 4.0m/s without the marker going haywire in some direction. So this issue happens even without Mechjeb.

Floating-point errors due to the game rounding numbers off. This is also why the map's apoapsis/periapsis/closest approach markers often jitter around when not in warp.

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MorisatoK

MorisatoK

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I noticed something weird with Sarbian's patched version when using the ascent guidance: I'm currently building up a space station and lifting up quite a few similar to nearly identical payloads with the same lifter. (And for the sake of testing it also happened with identical payloads)

Lift 1, no problem – love the force roll option for docking! Lift 2, again, no problem. Lift 3, the rocket won't lift off, no matter how often I reset, go back to Space Center/VAB and try to relaunch the rocket. It's spinning to the sides, doing loops and in the end crashes. This is also persistent after going back to the main menu and loading the save again.

Only solution is to restart KSP. Then it's possible to launch another two rockets, the third will freak out again until the next restart of KSP.

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Morlock

Morlock

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Floating-point errors due to the game rounding numbers off. This is also why the map's apoapsis/periapsis/closest approach markers often jitter around when not in warp.

Rounding errors are unavoidable, but still this way the PID should generate a maximum of stable response. However, the official PID often tends to wobble in large ships, even when rounding errors are negligible. A possible solution is to generate a more stable reference previous to the PID (for example with a filter), the reference of attitude would be constant if it was not for the rounding errors.

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Morlock

Morlock

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I tried maneuvering around in a clean install of KSP, with a stock Orbiter 1A craft, and I couldn't get below around 4.0m/s without the marker going haywire in some direction. So this issue happens even without Mechjeb.

I would like to see a video of this ...

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Yedin

Yedin

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A video? I'll see what I can put together! I'd additionally like to add that 4m/s was a little high of an estimate (sorry), it is usually 1m/s and below that the blue marker dances around so much that it is not possible to catch it even at the lowest percents of engine power. This appears to be the issue that would make mechjeb chase it around (mechjeb is a more accurate pilot than I am).

...or I could just be doing it wrong ;)

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Starwaster

Starwaster

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Oh okay. So the fact that it is taking my 7 stage rocket that I've used a lot to put stuff into geosynch and out to Mun, and committing the gravity turn at 5.4km instead of 10 to 11 where I normally do it doesn't really mean that 5.4km is the "better" place to do that turn?

I get the impression that there are presently quite a few known problems with this version as it functions either with 0.21 KSP else with other mods? I have RemoteTech running, but not using the Flight Computer. I just had MJ fail me on an Ascent that I turned over to full auto right after launch (really just to see how it works). First it didn't prevent overheats and my central engine blew up. Next it didn't actually relinquish control of the throttle or attitude when I clicked "Deactivate Autopilot" and then finally it sent my rocket into a spin at about 30km that caused it to break apart and fall out of the sky. Can try replicate or provide more details as needed.

It starts its turn at 5km because not everyone agrees about where is best to start the turn. The people who made the mod thought that was a good value (and it often is) so that's what they put in there.

But they also know that not everyone agrees on where is best to start the gravity turn which is why they put in the ability to edit your ascent path. Your ascent path has always been your responsibility to determine before each and every launch and you should get in the habit of checking your ascent path before each and every launch because in addition to everyone not agreeing what's best here: Not all rockets will do well on a given ascent path.

As for loss of control and blown up engines, that's also not a bug. As others have stated, damage could have resulted in your inability to control your craft. Another possibility is that one of the GUI windows had focus. That's not specific to MJ, that's common to most GUI interfaces.

As for your engine blowing up, all MJ does is lower the throttle so that you're not incurring heat buildup past a certain point due to excessive throttling.

But there are other sources of heat besides the throttle. Just today I was launching a difficult payload and the ullage retro rockets on two spent stages played their exhaust plumes over two of my engines as they were jettisoned. The engines were already hot and they exploded. That wasn't a problem with MechJeb, that was a PEBCAK issue and you better believe Starwaster went back to the drawing board and got his **** together and fixed his rocket so he could go to space today.

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Starwaster

Starwaster

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@Sarbian

I just downloaded your latest dll file. Looks ok so far, seems like even less oscillation than before. I'm not sure what you changed so I don't know what I should be looking for regarding testing. Sorry if you said and I missed it, I looked over the last few pages.

One thing though: Landings. I just initiated autolanding procedures for KSC. The good news is that it put me right back on the launch pad. So if you did anything to the landing code, good for you.

However, it left me hovering at 500m above the pad. I had to abort + 'land anywhere' to get it to touch down... It was almost as if I had used the hold vertical option to hover. I've not seen anything quite like that when landing....

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viperwolf

viperwolf

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@Sarbian

I just downloaded your latest dll file. Looks ok so far, seems like even less oscillation than before. I'm not sure what you changed so I don't know what I should be looking for regarding testing. Sorry if you said and I missed it, I looked over the last few pages.

One thing though: Landings. I just initiated autolanding procedures for KSC. The good news is that it put me right back on the launch pad. So if you did anything to the landing code, good for you.

However, it left me hovering at 500m above the pad. I had to abort + 'land anywhere' to get it to touch down... It was almost as if I had used the hold vertical option to hover. I've not seen anything quite like that when landing....

Im getting confused on the plugins, So is this a new plugin that will replace the Gamedata/scaledspacedumper? or does this replace the plugin under gamedata/mechjeb/

Sorry for my ignorance or missing the post

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sarbian

sarbian

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I think I'll create a new thread for "my" patch. I was waiting for R4m0n answer but he did not reply to my PM.

The more I wait, the more people are confused about this patch ...

Since MJ2 is GPL3 it's not a problem to fork, but I would feel better with R4m0n explicit consent...

Just to clarify it again : "my" dll is a build with patch that other dev submitted to the MJ2 github. The main feature is the reduced oscillation by Raf04.

I'll post a thread and details later.

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viperwolf

viperwolf

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scaledspacedumper??? That's not related to Mechjeb.

Sarbian created a new mechjeb2.dll that goes in gamedata/mechjeb2/plugins. Do a search of Sarbian's posts and you should find the link.

Oh yeah you are right sorry, that extra plugin was for Kethane i think.

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raygundan

raygundan

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Hey, I read back a few pages but couldn't find if this issue had been brought up yet. Would it be possible to have a toggle to disable landing gear deployment during auto-land? I've been bringing some pretty convoluted payloads down to my Mun base recently, often encased in shipping rigs, and when all the landing legs deploy at once things get... Messy :( I'd like the option to manually deploy only those landing legs that I need.

I ran into the same problem. Built a compact multi-part payload that has some landing legs in the middle of the stack that should remain stowed. MechJeb deploys *all* the landing legs, though, which causes premature explosion. A simple checkbox to disable landing gear auto-deploy would be more than sufficient. I can assign the ones needed for landing to a group and trigger them manually.

There does not, unfortunately, appear to be a way to change which parts are associated with the default landing gear action group, or at least it doesn't work. There is a "gear" group, but removing the unwanted legs from it doesn't stop them from deploying.

So, add my vote to yours, along with a pretty-please to the developer and a heaping amount of thanks for the amazing MechJeb mod.

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