Motion tweaking
This page describes some of the findings with Ian's Motion software and the DIY Motion Platform III

One has to realize that there are huge compromises in trying to mimic the forces during flight with a 3DoF platform. For example, simulating fore-aft or sideways sustained forces can only be achieved by tilting the platform to let gravity act on the occupant. However the tilting action to achieve the desired angle can be unwanted in itself, thus generating false force cues. To minimize the false cue, the tilting action has to be slowed down, but this then results in time delays of the desired force cue. Thus a compromise must be made between delays and false force cues. It is also important to realize that the occupant position with respect to the  platform rotation point will affect the magnitude in which the false force cues are felt. Generally, the closer the pilot's CG is to the platform rotation point, the better.
Driving the heave motion would seem straightforward, but in fact is quite complicated. During flight, vertical acceleration is very dynamic. The limited platform heave range will often result in saturated force cues. This needs to be overcome by applying some sort of dynamic compression and high-low pass filtering. It should also be noted that MSFS does not output very accurate vertical accelerations. X-plane performs much better in this respect.

The type of airplane, weather settings, your way of flying, they all come into play when tuning the platform. Most likely you will need different BFF config settings for different planes and conditions.   Below you can download my current config files that I use now: Note that these both use  the independent rig setting. I use these files in combination with the GWbasic program as shown on this page.

For small GA airplanes: Small-GA.bff

For bigger commercial A/C: Boeing737.bff

The fine-tuning of the motion cues is very tricky and time consuming. The video's show the basic platform motion versus flight conditions, but making your brain "believe" is another matter entirely. Motion can be convincing, but when it's wrong, it actually makes the feeling of flight less convincing. More is definitely not better. In trying to make your brain "believe", it is absolutely necessary to use a fully enclosed platform, without any external clues. Wide scenery screens will help a lot in fooling your brain. If you feel nauseous, you are doing something wrong, unless you're flying through a thunderstorm.

During the extensive testing phase, I have come to realize that the best way to achieve the correct motion cues is by checking them out separately. To simplify things, I have almost always used the Cessna 172 in light turbulence weather conditions, doing traffic patterns, and a Boeing 737 for testing the bigger commercial aircraft.


~~Under construction~~

Slow heave motion is not easily felt.  The heave motions need to be fast. (<0.5sec or so) therefore heave range need to be a much as possible, to avoid maxing out. The sensitivity of Ian's software needs to be tweaked a lot, and will vary for different planes.
The platform response is quite fast, therefore the low pass filter in the heave can be set at lowest value possible that will not produce oscillations.  

Examining heave flight data also shows that FS2004 has some limitations with respect to vertical accelerations on ground. Touch-down heave does not seem to produce realistic results; It is far too much. We believe that FS treats the whole airplane as a solid structure, without any gear suspension. This would explain the steep high peaks during touch-down and riding over grass land. This can be compensated by editing the .BFF file settings:
;When aircraft is on ground
;When aircraft is in air
This will reduce the on-ground heave excursions by half.


~to be continued~




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