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DIY Motion Platform 2 - Page 2

DIY 3DOF Motion Platform 2

 3-DOF Platform 2 Prototype - nose up.

PAGE 1 is here    Page 3 is here


After roughly three weeks in the workshop (part time) the parts and assembly work of the prototype Platform 2 is done and it is now up and running. The design works more or less as expected, although there are probably one or two areas where it could do with a few tweaks.

The three linear actuators seem well able to move the platform with pitch, roll and heave motions. I'm using the single chip SPU and PID servo controller software to drive it. Importantly the half-scissors load support mechanism with bungee cord springs is effective in balancing the vertical platform load so that the actuators are left to accelerate the mass of the platform.

An area where I have tweaked the design is the support leg construction which has turned out to be too flexible torsionally - this effects the leg rigidity when constraining fore-aft movement of the platform. I've stiffened this by closing the x-section of the legs (good for torsional stiffness) and adding thicker flange plates to further increase the polar moment of area.

DIY 3DOF Motion PlatformOther than these changes the design seems to work well under nearly full working loads - loaded up with bags of gravel and me. 


Below are three short movie clips showing the platform in motion. The first two show principally heave motion generated during a flight in stormy weather, the last clip shows the platform motion during a quick takeoff - I've still to adjust the motion controller settings to get the magnitudes of each DOF movement correct.


Clip1   Clip2    Clip3


And just added - Clip 4 this one with the platform "loaded" with roughly 110kg and with some modest flight movement generated by FSX, I'll do something more adventurous shortly! NB the annoying squeak is rubbing between two bits of wood somewhere - I haven't found it yet.)


One interesting behaviour that has emerged is the way in which the bungee cord spring arrangement allows sideways motion of the platform to occur if it is pushed in that direction. The normal movements of the actuators don't induce much lateral movements however fast rolling during stormy weather does induce some sideways or sway movement in the rig. If a way of actuating sideways movement could be devised the platform would be able to act as a 4 DOF platform. It would be possible to eliminate any sideways motion by fitting a partial Sarrus mechanism, but I'm going to leave it at the moment to see what it feels like. I have a feeling that some small degree of sideways oscillation may benefit the simulation experience. 


It looks as if I could also make a few useful changes to the motion driver software and setup program to provide better help for builders with this type of three-point support platform, so I'll be looking into that. (This is now done and the latest version of the software includes a new configuration program specifically for 3-point support type rigs.)


Below are a few photos of the rig as it currently stands - I'll keep you posted.


DIY 3DOF Motion Platform DIY 3DOF Motion Platform


I'm now looking at the design of the computer monitor support and a enclosed hood so I can do some testing to get a proper feel for the quality of the motion cues. Go to Page 3





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