Tuesday, October 20, 2009

Motion Racing Seat Update

It's been a while since my last post because I'm so busy...(yeah yeah I know everyone says that :-) ).

We're working on an exciting new iPhone game at Megadev which is starting to look great.
That coupled with me trying to sort out the business plan, pitch and tech demo for my new startup idea is taking pretty much all my time outside of the day job.


Anyway, this weekend I did find a few hours to work on my Motion Racing Seat again. After many months ticking over in the background I've finally got the whole thing bolted together properly including sturdy wheel and pedal mounts.


Having the pedals and wheel mounted securely makes a big difference to the feeling of immersion. I've made the horizontal width of the frame quite small deliberately to mimic what it is like for me inside a single seat cockpit. IIt feels great now and I even end up bracing myself with my knee's against the frame as I enter fast corners (exactly what I used to do in my Formula Ford!).

Apart from the frame, I also took some time to finish off the motion algorithms. After a lot of debugging they're finally silky smooth. They are a simple implementation off fairly standard motion cuing algorithms used in larger simulators:

    High-pass filtered g-force is scaled and applied directly to the platform angle.
    This is where you feel the onset of acceleration in any direction. It's especially effective longitudinally (fore/aft) and is scaled to be larger laterally (sideways) to compensate.
    This filtering smooths out the hard edge of the motion (where the seat stops moving abruptly), this reduces false motion cues that damage the overall effect.

    Low-pass filtered g-force is scaled and applied to the platform in the washout.
    This is where the larger sustained platform tilt comes from, it is applied slowly so you don't notice the motion application.
    What you do hopefully feel is the gravity coupling effect and physical sensations of pressure caused by the seat angle.

    Finally there is a low-pass output smoothing.
    In many games (especially Rfactor) the output is quite harsh over bumps in the track - unrealistically so and detracts from the g-force sensation (The 2 amp DC motors also driving the platform give serious kick, the smoothing helps take away the pain induced from a 1st gear-shift in an F1 car)!

Other than my own motion software, the seat could also be compatible with the open source X-Simulator software with a few minor tweaks - although my motion software is much simpler to use (all automatic).


So while It's not the best motion sim out there, the great thing is that it's produced from mostly off the shelf components, doesn't need any special tools to put together and is very cheap (comparatively). Power comes from a single laptop sized power supply (but 24v at 4 amps), so there is a lot of power but it's not hugely dangerous either.


I'm kicking around the idea of putting the plans on the net and possibly selling the few difficult to source components as a kit with the motion software. I would assume there are some pretty massive legal obligations to fulfil there for safety and public liability insurance? so maybe that will never happen - but you never know.


After watching Jenson Button win the F1 World Championship this Sunday (good lad!) I took the sim for a spin around Interlagos, Brazil in RFactor and it was really great and much more immersive than before by an order of magnitude.

A few things left to tidy up though... the lower frame is a bit to0 small so the sim is not quite as stable as it should be and the motor controller needs the wiring tidied up with the whole lot mounting under the seat somewhere.

Shouldn't be too hard to finish it off... hope I can find the time soon.

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