General aviation force feedback yoke for Cessna sim

[IanH1960]

Hi OP,

In the first instance try in the Pry_S.cfg file setting the elevator and aileron disengage values high - say 200 each. This will effectively disable the AP disengage feature and let you see what the basic AP following movement is trying to do.

Try this and see what happens - if it still disengages then can you zip up and send me the Logs folder - I'll have a look and see what the software is saying... I'll also be able to see what chip firmware versions you have on the cards.

Ian

[Cessna172sim]

Perfect. I'll send your advices to Ville and ask him to try to raise the values first and if this doesn't help, will send you the files.

//OP

[iwik]

Hi OP,
I too are waiting for Ian's ffb pedals. Re the AP i think i found the same thing
and cant remember what my setting was but found increasing the value somewhat can get you to a point where quite a lot of resistance is required
for ap to release.
Les

[Cessna172sim]

Thanks for the info. In our case we didn't even need to touch the yoke before the autopilot disengaged. It took appr. 3 seconds until the autopilot dropped off and went back to manual steering. We will first try what Ian already suggested and raise the value from 20 up to 200. Like said, we only tried to run the autopilot with the value increased from default 20 to 60. In our case the system might need a bit more resistance to disconned since there are more mechanical joints to cause extra friction. We actually added few drops of silicon based lubrication to C172 yoke shaft and now it's slick like a bacon in the belly.

Will report tomorrow. Until then, cheers from cold, rainy and chilly Pirkkala, Finland.

//OP

[iwik]

OP,
It works well when going.Look forward to how it goes.
From a lovely Frosty Sunny Morning in New Zealand.
Les

[IanH1960]

Hi OP,

Once you have tried the change I suggested and we see what happens there are a couple of other things we'll look at.

The amount of effort the system puts into trying to follow the AP is controlled by other settings, and I tended to set these to default at fairly light forces to keep forces low and limit the possibility of damage in DIY systems. It may be that with the additional effort to move your real Cessna control mechanisms the default AP following effort is a bit low and the controls aren't following properly - so the auto disengage (which is triggered by the size of the position error ie the difference between the positon demanded by the AP and the actual position of the controls at any moment) triggers and switches the AP off.

One factor controlling this is the PID settings which control the position following movement - increasing the elevator P term in the Pry_S.cfg file is one possibility. The bigger this P term is the more force is generated when a position error appears. It may be the default P gain is too low for your heavier system. (This may be term Les is thinking off - increasing the P gain also causes a bigger force to be required by the pilot to move the controls away from the demand position when they are in AP following mode).

The other is the overall cap level applied to the position following forces - this is set in the 20X2 chip firmware as a safety feature but can be adjusted by changing the programming and re-flashing the chip.

Once Ville has tried with the large trigger error settings and he can see the movement then we'll know a bit more...

Ian

[Cessna172sim]

Hi Ian,

Thanks for the info. I just received info from Ville that the AP value is now raised to 200 and AP now works OK and doesn't disengage anymore.

I also received the latest log and config files. Could you kindly drop me email to my robots[at]jippii.fi address so I can send the files for you to check.

BR,
OP

Hi OP,

Once you have tried the change I suggested and we see what happens there are a couple of other things we'll look at.

The amount of effort the system puts into trying to follow the AP is controlled by other settings, and I tended to set these to default at fairly light forces to keep forces low and limit the possibility of damage in DIY systems. It may be that with the additional effort to move your real Cessna control mechanisms the default AP following effort is a bit low and the controls aren't following properly - so the auto disengage (which is triggered by the size of the position error ie the difference between the positon demanded by the AP and the actual position of the controls at any moment) triggers and switches the AP off.

One factor controlling this is the PID settings which control the position following movement - increasing the elevator P term in the Pry_S.cfg file is one possibility. The bigger this P term is the more force is generated when a position error appears. It may be the default P gain is too low for your heavier system. (This may be term Les is thinking off - increasing the P gain also causes a bigger force to be required by the pilot to move the controls away from the demand position when they are in AP following mode).

The other is the overall cap level applied to the position following forces - this is set in the 20X2 chip firmware as a safety feature but can be adjusted by changing the programming and re-flashing the chip.

Once Ville has tried with the large trigger error settings and he can see the movement then we'll know a bit more...

Ian

[IanH1960]

Hi OP,

Okay...

If you don't need the control movement AP disengage feature then you can probably continue with the higher position error trigger settings.

If you do want to be able to AP disengage by moving the controls then these are the checks you'll need to go through..

1. Use the Zero button on the CL software each time you start it - after the cards have been calibrated and after a successful Ping has been done to ensure the cards are responding. This will instruct the cards to drive the yoke to what it thinks the true yoke zero position is and the CL software will compare this to the joystick axis zero position. The AP following position demands will then be calculated more accurately.

2. Try reducing the trigger error settings in steps and each time re-starting the CL software (repeat the Ping and Zero's each time you restart the software) until you start to see the false disengage behaviour returning.

3. If the trigger settings are still above about 50 say then the control movement AP disengage probably won't feel satisfactory - ie you'll have to move the controls further than you want to get the AP to disengage. In which case....

4. Try increasing the P term gains in the Pry_S.cfg file to sharpen up the position following effort. But don't go much above doubling the existing value... If this doesn't allow smaller trigger settings to be used then you may need to try 5.....

5. ...raise the position following force cap level by re-flashing the 20X2 chip - I can help with the appropriate settings if you get this far...

If you are happy using the normal instrument buttons for AP disengage then you don't need these tests..

I've dropped you an email.

Ian