Experimental Control Loader (Force Feedback) Software

IMPORTANT Sept 2011 - this version of the software and system has now been superseded by a brushless motor system - See the new DIY FFB Flight Yoke.

IMPORTANT - This software DOES NOT drive of-the-shelf force feedback joysticks. It is intended for DIY builders wishing to EXPERIMENT with their own higher force flight control loader designs.

Following a number of requests from site visitors I've made available the flight sim control loader (force feedback) software developed during the various force feedback projects described on the site. The software calculates and exports force feedback levels used to drive electric motor loaded DIY flight controls.

The software is experimental and I've made it available for free (for personal non-commercial use).

The software is capable of providing 8, 10 or 16 bit force demands at up to 500Hz refresh rates. It works for MS FS9/X systems. It can be run on the same PC as the flight sim software or on a LAN PC if the CPU loading on the flight sim PC is too high to allow the high force loop refresh rates needed.

To operate effectively the software must be used in an overall system as described below. Even then the quality of the force feedback you obtain will be critically dependent on the quality of the electric motors you use and the quality of the design and build of the force transmission and other mechanical elements in your controls.

To generate actual motor torques the output from the software must be externally processed and passed to motor speed controllers which drive the motors. For builders who wish to experiment with their own flight control designs but who do not have expertise in building the required microcontroller based hardware the 64SPU-1 micro-controller card available on the site can be used - see above right. The 64SPU-1 card is available un-programmed ready for programming with sample flash programs I can provide or with your own PICAXE .bas code.

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If you require the sample control loader PICAXE 20X2 flash programming for the 64SPU-1 card please email me.

Making an effective control loading system is a fascinating project, but it can be a fairly unforgiving task - so if you do try it go into your project with your eyes (and your wallet) open!

System

Click on the image below for a system layout diagram. There are a set of NOTES which should be read in conjunction with the layout diagram. Please examine the layout diagram very carefully and read ALL of the notes as they are important. The system illustrated in the diagram uses Devantech MD03 8 bit motor controllers to drive DC motors - these could be changed for other controllers if you have or can develop suitable microcontroller programming to instruct them. The 64SPU-1 card shown in the system could also be replaced with your own signal processing hardware - the data output formats of the control loader software are given in the Quick Start Guide.

The system requires the flight controls to be built using a 12 bit joystick card with precision pots. This is because the control loader software taps directly into the resulting joystick 12 bit position reporting through the windows operating system - it does not use dedicated stick position reporting pots/encoders. The reporting MUST be 12 bit with maximum pot electrical travel utilisation. I have used Leo Bodnar's BU083A 12 bit card.

Software

The BFF Control Loader software has two main programs - the BFF CL Setup application and the main BFF Control Loader application.

BFF CL Setup is used to configure and save the control loading parameters for individual aircraft or other flight conditions. The settings are saved in .cfg configuration files which can be selected when the main BFF Control Loader software is run.

The setup program can also be used to adjust individual settings whilst the control loader software is active - this allows adjustments to be made and the effects on the force levels and feel to be determined quickly. CARE is needed when using this feature

I have not written an extensive user manual for this experimental software. However there are fairly detailed tool-tips available - move the mouse over any of the Elevator axis input fields for details. The inputs for the Aileron and Rudder axes have the same definitions as those for the Elevator axis.

The main BFF Control Loader application provides the live force level output. It can be run on the flight sim PC or on a LAN PC. It pulls live flight data from FS9/X using Pete Dowson's FSUIPC. It also pulls 12 bit flight control position data from the windows joystick interface and combines the two to calculate the force feedback levels. The flight data and joystick movement/force calculations are done through two separate processes so as to maintain the high force loop refresh rates needed for stable operation of the system.

The main force elements of the loading are -

• Control and trim surface aerodynamic loads

• Control surface prop wash effects

• Control surface weight and acceleration loads

• Buffeting effects from stall and landing gear

• Engine vibration effects

• Fixed balance loads

• Damping, friction and motor back-EMF compensation forces (all position reporting quality dependent).

Each of these is adjustable and can be removed from the loading completely if required.

The loading model uses the control axis position and velocity as the indicator of control surface position and velocity. Airspeed, aircraft accelerations, engine condition, gear position and stall state are all taken from FS9/X. Trim surface position is taken from the independent trim pot positions. Aerodynamic loads are calculated from control surface deflection and airspeed. For more information see the pop-up tool tips in the BFF CL Setup application.

IMPORTANT - I've put the speed of movement related terms into the software to allow them to be experimented with. How effective these terms can be will depend strongly on the quality of the control movement reporting, the system refresh speeds and the quality of the motors and transmissions - ie on the rest of the system design. Remember the software is just one element of an effective control loading system - the entire system MUST be right to get good results.

I've put together a quick start guide to assist with initial setup and use of the software.

The guide includes details of the serial data output formats used by the software to export the force demands to allow you to program your own processing hardware should you wish.

If you experiment with the software let me know how you get on.

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