6DOF Motion platform - shaking when taxiing away

[MadMonty]

Hello all,

 

since February I have fulfilled myself a dream and bought a 6DOF platform from Motionsystems. After their software was rather designed for racing simulations, I got the DCS profile developed quite well in the last months with their developer to simulate all movements as realistically as possible.

 

However, there is still a bug, which - I remember from some post that I can no longer find - is probably due to DCS:

 

When I taxi off with a plane (no matter which one), the platform moves in a very jerky way.  As soon as I am taxiing, everything is fine. It only ever happens when taxiing away from a standstill. After consultation with the developer of Motionsystems, this is an output of DCS.

 

Does anyone know the problem and does anyone perhaps even know a solution?

 

Unfortunately, I am not a DIY person who has the knowledge and time to build a platform including software myself. Therefore, I am very happy to have found a "plug & play" product at Motionsystems. However, the above-mentioned problem must be solved via DCS.

 

Many thanks in advance!

[gianlu320]

Hello @MadMonty

 

I also have a motion platform, it’s a four dof but I think I am experiencing your same problem.

This happens only when you start moving from standstill right?

I believe this has to do with surge.

As I understand you use proprietary software with your motion platform, instead I am using simtools so I don’t really know how your software works.

But you could try this…

First try to temporarily disable surge and see if you still have the problem.

If the problem is gone then surge is confirmed to be the  issue.

You could try to apply a bit more smoothing to the surge axis (again, I don’t really know how the software you use works)

one other thing you could try…

before starting to taxi, apply brakes, add a bit of thrust and only then release the brakes, this should alleviate the problem

 

i hope this helps

 

[MadMonty]

Many thanks @gianlu320

 

Yes - it only happens when you stand still and start rolling. I also noticed that it is worse at low throttle (when rolling) than at full throttle (when taking).off).

 

The software from Motionsystems also includes "VR Headway", so the movements of the platform are calculated out and you always stay centred in the cockpit, no matter how the platform moves. This was very important to me because the platform is a monster with +/-30 pitch/roll and has enormous power. That's why I decided to use Motionsystems, in order to have a ready-made plug-and-play solution.

 

How do you deal with the movements of your platform, are you also able to compensate for these movements in VR? Or do you work with sensors that are attached to your platform? (Or do you end up not using VR, but I can hardly imagine that...)

 

I'll test tonight what changes or improvements I can make with the Surge settings. 

[gianlu320]

i Had a look at the motion systems website.

those are very nice platforms over there.

What model did you go for?

I am also contemplating a new platform.

I haven’t decided which type or brand yet.

 

For what regards your jerky motion from stand still, I can’t help you much since I don’t know the software you use but 

as I said, I strongly believe the problem lies with surge.

 

For what regards motion compensation I use a vive tracker mounted on the platform.

It works quite well most of the times.

The tracker gets confused quite easily under strong vibration so it doesn’t particularly like Jetseat or butt kickers but if they are properly set it works even with them.

 

I hope you can fix your problem and as I said if you apply brakes and add just a bit of power before releasing them you should see an improvement on the motion from standstill.

 

[MadMonty]

I am using a PS6-TM-150, which is the "smallest" 6DOF System of Motionsystems, which still weighs in at over 300kg.

 

 

I'll probably do a post with a detailed review during my holiday in August, now that the software transfers almost perfectly all movements from DCS to the platform...

[gianlu320]

Very nice machine!

I am definitely interested in a review and obviously I am wondering how you installed seat, hotas and all the rest so I can’t wait for your review actually.

And also I am wondering how the motion software handles the movements.

Does it simulate angles or forces?
 

Too many questions….I know

I will wait for your review

 

Dcs is amazing but on motion it’s on another level

[MadMonty]

The software simulates both angles and forces. This is exactly what was important to me, so that the most realistic feeling possible when flying is created.

 

You can explain it - just looking at the pitch function - as follows:

 

Aircraft accelerates in straight flight >pitch backwards as long as acceleration continues

Aircraft climbs >constant pitch backwards

Aircraft decelerates while climbing due to speed brakes >pitch forward, despite of climbing, as the force of decelaration are higher than pitch of climbing

Pulling positive G backwards during deceleration with speed brakes >maximum pitch backwards, as vertival G-forces are superimposed on deceleration and climb

 

This is exactly what we have developed and tested over and over again over the past few months until it fits. Now when I'm inverted, the pitch is forward. If I pull G while being inverted, the pitch goes back immediately. That in combination with the other 5 axes is ultra realistic. As you have already correctly said - once you have such a platform it will no longer work without it. The same fate as back then with the first VR glasses 

 

The only problem is still being shot down - the platform has so much force left, that you are scared of your life when the aircraft is tumbling down. I alway have to stop the platform immediately, being worried about my pit construction. The good thing on that is - you think now twice before entering a fight or attack run - just as in real life...

 

I will show my pit in my review. It ist based on the monstertech flight rig...

[gianlu320]

I also stop the motion after being shot or if I am about to do a forced landing or any other crazy thing

Your motion cueing software seems to be working really well.

I will definitely keep an eye for your review and on motion systems website.

[MadMonty]

Hey @gianlu320

 

Last night I took a closer look at the problem of jolting when rolling away.

 

It definitely seems to be sudden lateral forces that DCS sends as output when rolling away. These lateral forces are transmitted to the platform in "Sway" and "Roll". I had already reduced "Roll" on the platform anyway, because otherwise the forces during the flight resulting from wake turbulence were too high. If I now switch off "Sway", jerky "roll effects" remain when rolling away. But I can't switch them off because otherwise my turning flight would not be simulated cleanly.

 

However, I have the option of setting the "Sharpness" in my software and have now set this to zero for "Sway" and "Roll". That helps a lot, I now still feel very slight shaking movements when rolling away, but these are negligible. In this respect, thank you for your input - it has helped me a lot!

[gianlu320]

I am happy I was somewhat helpful.

very weird, I experience what you experience as well but on my rig the problem is with surge.

anyway… sway or surge or others, it doesn’t matter, if you continue adjusting your motion cueing software you will definitely find a good setting as you are already doing.

 

enjoy it!

 

[trigen]

In for example Pt Mover you have a ground and air setting. Since this is mainly a sway issue when starting to move you can set a spike filter on that force alone on the ground and not have this issue.  I dont know how their software works but i would ask them for these options.  

[MadMonty]

On 7/29/2021 at 12:05 PM, gianlu320 said:

I also stop the motion after being shot or if I am about to do a forced landing or any other crazy thing

Your motion cueing software seems to be working really well.

I will definitely keep an eye for your review and on motion systems website.

 

It took a verly long time to finalise my review, but here we go: