Hardware Interfacing directly form the cockpit controls:
For the DIY motion platform I, interfacing directly from Yoke
movements and signals derived from the Force Feedback stick were used.
When planning the interfacing, it is important to realize what kind of
motion you want to achieve. The article in Motion systems clearly states
that you would want to achieve the initial forces that act on your
body when starting a certain aircraft maneuver. This would imply that one
should take the derivative of the aircraft movement in order to
simulate the initial accelerations. Although this is probably a rather
simplistic approach, I have based my hardware interfacing experiments on this
principle.
The above circuits show some possibilities for deriving motion platform
drive signals from the cockpit controls movement. For isolation purposes, I
used dual potmeters or dual contact switches. For isolating the FF stick
signals I fed the PWM signal of the FF circuit through a fast opto-coupler
(having push-pull output).
The circuit in between the control and the buffer is a differentiating
network, that will slowly return to center. A resistor can be connected
parallel to the differentiating capacitor, in order to keep the platform
tilted with a constant yoke deflection (for simulating the back pressure
during a climb)
The
bread-board with several filters
The list above shows what cockpit controls can be used for generating
platform drive signals.
I found that the interfacing of all these controls takes lots of
tweaking: Sensitivity, time-constants, polarity, the results are not always
what you expected. Sometimes a certain motion feels right only with certain
maneuvers, but totally fake with other flight conditions.
The motions I actually liked best were the pitch rotation and small
bumps and vibration signals that I got from the FF yoke signals.
In the new DIY motion platform II and III, I have used motion cues derived from the flight parameters in Flight Simulator.