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

[Neutrinovore]

I'm having more and more of an increasing problem with Mechjeb and it's auto-guidance.

It seems that it ALWAYS over corrects - it ends up wobbling back and forth because it's over correcting.

I've proven that it's not my rocket designs by using the SAS which can keep it rock steady.

I often have to intervene to keep it going where it should.

What is the issue? Almost like I need to turn down the gain on it or something.

Which you can do, as I've just recently discovered. I'm always learning new things about MechJeb, lol.

Anyway, open up MJ's 'attitude adjustment' window. One of the few things you can adjust there is the 'Tf' value. It always defaults to 0.3 for me. I've found that if I have a really tiny probe, like a mapsat, setting this to around 0.15 to 0.2 makes the maneuvers much more crisp, and it doesn't take nearly as long to acquire a new heading when executing maneuver nodes.

However, for your purposes, M3, try setting the value higher for large rockets. Perhaps 0.7 to 0.9 or even more, you'll have to fiddle with it to find an optimal value for each rocket. But like you were saying, this seems to have the exact effect of 'turning down the gain', so your big rocket stacks (hopefully) shouldn't shake themselves to pieces anymore, or perpetually oscillate around a maneuver node, etc.

Anyway, I hope this helps. Good luck!

[sarbian]

I look into finding a way to more or less autotune Tf (some number derived for torque / mass most likely), but for now you'll have to tune it yourself. It's easier than the 5 numbers of the old pid however

[Starwaster]

That sucks, but i don't want cheat either. So with tech node unlock ascent guidance, IMHO this is my favorite feature in MechJeb:D

There is no cheating. It's your sandbox (even if you aren't in sandbox mode)

If you go along with it then it's because you chose to, but that's ok too if that's what you want.

[M3Man03]

Which you can do, as I've just recently discovered. I'm always learning new things about MechJeb, lol.

Anyway, open up MJ's 'attitude adjustment' window. One of the few things you can adjust there is the 'Tf' value. It always defaults to 0.3 for me. I've found that if I have a really tiny probe, like a mapsat, setting this to around 0.15 to 0.2 makes the maneuvers much more crisp, and it doesn't take nearly as long to acquire a new heading when executing maneuver nodes.

However, for your purposes, M3, try setting the value higher for large rockets. Perhaps 0.7 to 0.9 or even more, you'll have to fiddle with it to find an optimal value for each rocket. But like you were saying, this seems to have the exact effect of 'turning down the gain', so your big rocket stacks (hopefully) shouldn't shake themselves to pieces anymore, or perpetually oscillate around a maneuver node, etc.

Anyway, I hope this helps. Good luck!

Thanks much! I'll give it a shot.

What does Tf mean anyways?

[Neutrinovore]

Thanks much! I'll give it a shot.

What does Tf mean anyways?

No clue. I've always wondered myself, actually.

[Starwaster]

Thanks much! I'll give it a shot.

What does Tf mean anyways?

term factor.

[Neutrinovore]

term factor.

Huh. Okay. Could you elaborate a little more?

[Guest]

It's really weird. I haven't had this stuttering problem before. Only since .22!

I'm running at max graphics 60fps and the game goes from 60 to 0 every 5 seconds. Any fixes yet?

[Dax]

I'm new to kerbal and mods, I think I installed it correctly and the parts show up in the builder but there is no button to show the windows during launch in sandbox or career mode. Did I do something wrong or am I looking in the wrong place? Thanks

[Galane]

Having some big improvements to the spaceplane and rover sections would be most welcome.

As it is now, pretty much all the plane function does is put it onto a heading. It doesn't hold altitude or attitude or do landings, at least not very well. I tried using Ascent Guidance with the stock planes but all that does is flip the plane up on its starboard side then execute a right angle turn. Managed to slam right into the VAB once. Would be nice if the game would at least leave scorch marks.

Rover guidance could use a cruise control, operating throttle and brakes to maintain a set speed, even when freewheeling down hills. What I've found is less grabby than the brakes is disabling all or most of the motors at the front and pulsing in reverse to slow down, sort of like old west pioneers dragging a log behind a horse drawn wagon.

Such a control would have to have an adjustable brake and throttle pulsing control since those are full on or full off. It'd also need to check whether or not any of the wheels are off the ground and let off the throttle or brake because that's a likely indicator the rover is about to go end over end.

There must be some weird physics around crater edges on the Mun. I've tried lots of times to do a Dukes of Hazzard style jump to dispose of rovers but most of the time when I get close to the edge the rovers will tip up on their left wheels, spin sideways and flip over instead of going straight off the edge.

[Starwaster]

Huh. Okay. Could you elaborate a little more?

http://lmgtfy.com/?q=term+factor

[Neutrinovore]

http://lmgtfy.com/?q=term+factor

Okay, fine, that wasn't really helpful. I was thinking that maybe YOU would care to impart a little of YOUR knowledge on this matter, specifically as it relates to MechJeb's 'Attitude Adjustment' module, but it seems that was asking far too much of someone who so obviously has far better things to do than enlighten the great unwashed such as my lowly self.

Sorry for wasting everyone's time, I'll not inflict myself upon you any further.

[TranceaddicT]

I really think it stands for Time Factor.

It's a variable in the PID (proportional-integral-derivative) controller

http://forum.kerbalspaceprogram.com/threads/49381-Mechjeb-How-to-make-SASS-chill-out-stop-wasting-RCS-and-shaking-things-apart?p=641736&viewfull=1#post641736

"Tf is how frequently she'll recalculate. .15 is a good middle ground value, but adjusting it can help when dealing with a ship that flexes, or with varyingly responsive ships. Basically, if your rocket flexes back and forth at approximately the same rate that sassy is figuring control inputs, they'll resonate and you'll get more and more flex. .05 is the lowest (fastest) I go, and .3 is the absolute highest (slowest). Play with it until the wobbles go away. It's kinda like caffeine and sleeping pills for Sassy- Too slow and she'll be sluggish, too fast and you'll get control inputs jiggling all over the place. "

[Carl]

One request for mechjeb. Currently not going docking systems in career mode so i tend to build my current designs around my standardised class D Booster. It has more than enough Dv to put the final stage + Lander in orbit with more than enough fuel for the final stage to handle all of the decent. Obviously though the final stage isn't designed for landing but as mechjeb is set up it's nearly impossible to safely jetison the final stage at the last second as the breif loss of thrust causes mechjeb to overshoot or crash the Lander. Would it be possible to have mechjeb perform the landing as now under autopilot, but at some pre-determined safe height, jettison everything below a set stage so that only that stage and everything above get's landed?

[sarbian]

It's really weird. I haven't had this stuttering problem before. Only since .22!

I'm running at max graphics 60fps and the game goes from 60 to 0 every 5 seconds. Any fixes yet?

Do you have errors in the log ? Did you try the dev version ?

I'm new to kerbal and mods, I think I installed it correctly and the parts show up in the builder but there is no button to show the windows during launch in sandbox or career mode. Did I do something wrong or am I looking in the wrong place? Thanks

Did you add the part on the ship ?

Does your install looks like that ?

KSP\GameData\MechJeb2
                                    \Plugins\MechJeb2.dll
                                    \Parts
                                         \MechJeb2_AR202\...
                                         \MechJeb2_Pod\...

@TranceaddicT / Neutrinovore : it not exactly that anymore. Now it's the response time of a low pass filter.

In the end it works the same and you should lower the value for agile ships and increase it for the sluggish one.

@Galane yeah spaceplane need love but see my post on the previous page. Rover are on my list.

@Carl unlikely for now, it would mess up the landing sim precision.

Edited November 8, 2013 by sarbian

[mbvanities]

Mine looks like that but I’m having the same issue

[Galane]

The trick to a MechJeb landing on Kerbin without parachutes is to ensure the part of the ship you'll be landing has enough fuel to make it down, at least after the initial deorbit burn.

So do the deorbit burn and when MJ shuts it down, quickly hit the spacebar to jettison the deorbit stage. If you have enough fuel and a TWR high enough, MJ will safely bring your ship down.

Put a little power and a probe core on the deorbit stage and MJ can land it too! IIRC I had it bring the lander down first, then the deorbit stage. It parked it perfectly upright just on the engine gimbal, no RCS, and then it didn't fall over.

That's a two stage lander. It has three radially mounted engines and tanks which are used for Mun landing and Mun Liftoff, then they're popped loose for the single engine to take over. This pic is from the final test to ensure it could land on Kerbin, before it went to the Mun.

MechJeb's landing accuracy tends to vary between pinpoint precision and missing the target by several kilometers. I dropped a couple of beacons consisting of the thin probe core, a clampotron jr and a PB-NUK on the Mun. (Likely didn't need the RTGs since it's possible to target a powerless but remotely controllable ship.) They're about 3.5 KM apart and I'm lucky if MJ will put a lander within a kilometer of either one.

Here's some previous version of MechJeb being a little too precise on hitting its target. Fortunately I was able to drive it off then back the first one out of the way and use RCS to flip the second one upright after it tipped on its side while driving off.

If it would hit those beacons like this all the time, that would be very nice.

Edited November 8, 2013 by Galane

[sarbian]

I edited my previous post a second ago to reply for the spaceplace/rover.

The precision comes mostly from the landing sim, so if some design miss by a large amount it's most likely that the sim messed up. Post screens and/or cfg of the landers and I'll have a look.

[Galane]

This should be all stock. http://pastebin.com/Yda16emj

It's the rover I used to place the beacons. I used hyperedit to put it in Mun orbit, then landed with MechJeb to drop the docking port mounted beacons. The way it's built, would be no problem to stick a rocket underneath to get it places the normal way. With the beacons dropped and less than a half tank of fuel it can do a Mun escape to Kerbin orbit by going straight up. (I was trying to crash it for disposal, didn't expect it to just fly away.)

16,000 unit Kethane mining rover that has trouble hitting targets with MechJeb. http://pastebin.com/5YpBZwGi

Mods needed, Kethane, Stretchy Tanks, KSPX (for the reaction wheel on the bottom), this thing and possibly ReStock but maybe not. I've built too many things to keep track of what's in all of them.

I could post the 32,000 unit lander but it definitely needs ReStock, adds Infernal Robotics to the list for the landing gear extensions and has the spring strength increased to 10 on the stock landing legs. (I'd also have to yank off its special parallel stack launcher and save it as just the lander if you'd just want to test the lander.)

[Carl]

@Carl unlikely for now, it would mess up the landing sim precision.

I don't see how. It's just as accurate with me manually ejecting the stage during decent as it is ejecting it in orbit and de-orbiting on lander power only. It's just annoying because you have to time it perfectly just prior to where mechjeb needs to begin the landing stage burn or it results in you slamming into the ground.

[CAPFlyer]

He told him to clear the box that enables / disables the option and that is the correct solution and offered his opinion on why he (jean) might not have realized that the option was there, because for whatever reason the answer was staring him in the face and he wasn't seeing it. what more do you want from Galane?

First, since jean took down the pic, I can't see what he was seeing, but from the description it sound like he had it unchecked but it was still active. If that's not correct, then I apologize. However, I do not apologize for the rest of my post that the rest of the post belonged elsewhere. It was not germane to the problem at hand (i.e. how to help jean) and it was not an actual specific technical issue, just his opinion on how UI should be done.

[Starwaster]

First, since jean took down the pic, I can't see what he was seeing, but from the description it sound like he had it unchecked but it was still active. If that's not correct, then I apologize. However, I do not apologize for the rest of my post that the rest of the post belonged elsewhere. It was not germane to the problem at hand (i.e. how to help jean) and it was not an actual specific technical issue, just his opinion on how UI should be done.

Oh the box was very much checked and the rocket was at terminal velocity so that part of the plugin was definitely behaving as it should have.

And since apparently the UI is the very embodiment of perfection with no room for improvement then I guess Jean just has no excuse and should have known better. PEBCAK error; case closed.

[AlmightyR]

How can I add the new version of MechJeb to my pods (career mode)? It doesn't seem to be working no matter what I try.

First, I tried adding just the MechJebCore module, using MM; Didn't work.

Then I expanded that by adding the MechJebLocalSettings stuff to it; Still didn't work.

Then I tried expanding further and adding the MechJebAR202 module; Yet still didn't work.

Then I tried asking for help in the forums; I hope it works.

[Starwaster]

How can I add the new version of MechJeb to my pods (career mode)? It doesn't seem to be working no matter what I try.

First, I tried adding just the MechJebCore module, using MM; Didn't work.

Then I expanded that by adding the MechJebLocalSettings stuff to it; Still didn't work.

Then I tried expanding further and adding the MechJebAR202 module; Yet still didn't work.

Then I tried asking for help in the forums; I hope it works.

Post the MM codes you're using and let's take a look at it.

[AlmightyR]

Post the MM codes you're using and let's take a look at it.

I was using MM extension and didn't realize pods no longer have the ModuleCommand module.

*whisper* Damn you SQUAD! Stop changing standards for no reason! *whisper*

Got it working now.

Thanks for the will to help.