A Peek at MotionPSX

[Garry Richards]

MotionPSX is the fourth component of the VisualPSX Suite. It enables PSX to drive the motion platform for Matt Sheil's magnificent sim and is in final beta testing to be ready for Worldflight 2014. Forum members might be interested in how it works and what it does to enhance the PSX experience. If so, read on.

MotionPSX accepts data from PSX that reveal how it is accelerating and rotating in 3 dimensions. These physical inputs are adjusted and fed to the motion platform's controller. This is a piece of hardware containing firmware that moves the platform in various ways. It does not follow the pitch and bank of the aircraft (as some arcade simulators do) but instead moves to produce specific physiological effects on the pilots. With the help of gravity and the wraparound visual scenery these movements elicit psychological responses that give the impression that the cockpit is moving as it would be in real life. The effect is quite convincing!

From outside it is usually impossible to guess what PSX is doing. For instance, during the takeoff roll the platform begins to pitch up as the aircraft accelerates. Inside the cockpit the pilots see the aircraft still level and racing down the runway, but they feel themselves being pushed back in their seats and interpret this as forward acceleration.

The controller has many parameters that can be adjusted and these, together with the adjustments possible in MotionPSX enable the platform to simulate the feel of a heavy 747 rather than the much lighter aircraft for which it was originally designed.



The platform is hydraulically driven and can tilt forward and backwards and from side to side over a considerable range and can also move vertically up and down. It can move at dangerous speeds that could injure or even kill anyone struck by it or being thrown around inside the cockpit. For this reason there is a safety fence around it, a rotating beacon to warn that it is active and a loud horn to warn that the hydraulic rams are being pressurised. Personnel inside the cockpit have to be fully harnessed before the platform is activated. MotionPSX limits its outputs to safe levels but of course software or hardware could fail.



MotionPSX connects to the controller hardware through a serial port and to the PSX main and boost servers.



The Axes tab is used to calibrate the main inputs to the controller. AccFwdX, AccRightY and AccDownZ are accelerations forward, sideways and vertically. VelPitch and VelBank are rotational velocities for pitch and bank. The calibration algorithms in MotionPSX were developed and their values set by trial and error to produce the best feel when manoeuvring PSX.

The controller also accepts a heave input intended for producing a sharp bump at touchdown. We also use it for various other single bumps and can send bumps repeatedly to create a continuous vibration useful for ground rumble and air drag effects.





The output can be monitored continuously if necessary and shows the raw inputs, their scaled outputs and the packets being sent. In use these values are changing continuously.



The photo shows outputs during a landing roll (before outputs had been calibrated).

Worldflight 2014 begins on Sunday 2nd November.

[Jeroen Hoppenbrouwers]

This was all developed on a Saturday evening after a few beers, right?

Hats off!


Hoppie

[brian747]

Brilliant, Garry!    

No war stories of wild rides during testing?    

Cheers,

Brian

[Garry Richards]

Hoppie,

As you know from your own work, software development is really easy, takes no time at all and earns you heaps of money. And error-free code flows best when the beer is also flowing. :twisted:

Brian,

There were some exciting moments early on before we tamed the beast, but that was long ago and thankfully only dimly remembered. :shock:

Cheers,

[kiek]

Yes, real programmers only need a Fortran compiler and a beer.  

[Jeroen Hoppenbrouwers]

There were some exciting moments early on before we tamed the beast, but that was long ago and thankfully only dimly remembered. :shock:

http://www.hyway.com.au/747/2006-1.php





.

[John Golin]

I haven't felt her rock and roll yet, too busy getting the other avionics working, but I am hearing good things about the motion Garry!

https://onedrive.live.com/redir?resid=C8934858E7840CED!41810&authkey=!AJQHkdEsCyqR5ss&v=3&ithint=photo%2cjpg