Realistic rudder TRIM

[Ourorborus]

So I am currently working on a DIY rudder pedals to replace my aging Saiteks. Whilst mindstorming the centring mechanism I thought what if I made the Centre Point adjustable with a stepper motor? Then I could use the stepper motor to provide a realistic trim function. i.e. trim the pressure out without physically re-centring the axis.

 

I could do this with a motor/trim control hardwired to the steppermotor and use that instead of the in game trim. Then I thought the ultimate solution would be to use the in game trim to drive the motor. Not to hard to do with an Arduino Leonardo, the stepper simply becomes an output.

 

The problem: if, for example, I applied half left rudder trim in game, and that physically moved the centre point of the axis to half left. The potentiometer of the axis would still register half left PLUS the game aerodynamic model would register the trim as half left causing the final effect to be full left. In short is there a way to edit a Lua to make the in game trim feed a forcefeedback axis and have zero effect on the aerodynamic model?

Edited April 28, 2020 by Ourorborus

[RustBelt]

I think if you just build the Rudder pedals as a DirectX Force Feedback unit (IE make the electro guts of it out of a Sidewinder FFB 2.) it should do that. Although no telling if it can be strong enough to notice and/or not burn out the wee motors. Feet have lots of power behind em.

 

You could go completely nutbar and use the FFB Motor from the FFB2 to run a hydraulic or pneumatic sector valve driving an actuator connected to the pedals or a spring return mechanism on the pedals. Then it's just a matter of adjusting the feedback response so the motor and Pot still THINK things are working as they should.

[Ourorborus]

Cheers rust. I think I have a solution without hacking a doner device. If I can ouput the trim position telemetry that can add a variable to the Arduino sketch that I can then use to offset the centre.

[RustBelt]

Slick, but the problem may be that you trim in rudder trim, and the game models that, then you also are deflecting the rudder, which the game then also responds to.

[Ourorborus]

That was essentially the problem I was concerned about. The solution I intend to try will be to add an offset to the axis output based on the trim input.

 

Thus:

 

Trim setting from the sim will adjust the physical centre point of the pedals AND apply a software offset (in the opposite direction) to the axis output.

 

eg. imagine the rudder axis extends from -4 to +4 with the natural centre being 0.

 

If you press on the left pedal a little it will go to -1, a lot -4.

 

If I adjust the in game trim left until the -1 position, the centring mechanism will move so that the physical centre is at -1.

 

If I do nothing else the game will now apply the -1 (left) trim AND the -1 axis input.

 

To Solve I intend to make the axis input the pot position - the trim position from the game.

 

Thus if trimmed to the -1 position, the axis will output the zero position whilst being physically centred at the -1 position.

 

………….hopefully. I am still working on the design and print for the non trimmable version, but designed such I can easily modify it to the trimmed version once it works.

[RustBelt]

Very interesting. That should work.