David
The GPS 196 is only able to output at 0.5Hz i.e. every 2 seconds. I originally
used an AVMap EKP-V and that also did 4800 baud and 2 second update. The AP
function
ok but I did notice some interesting features. It would capture a track
by overrunning and then turning back and also on change of direction it would
overrun the turning point and then do an S-Type recapture. Once you got used
to it it was ok but you defiantly didnt want to be close to airspace when using
and expecting it to turn 1 nm from an infringement!
I now use a Garmin 760 and that updates at 1 sec intervals and does pretty much
the same thing as there is no pre-emptive turn message so it does the s-turn
to capture and change direction.
I assume that you are using Mod 75 from the Europa Club Website?
I didnt install mine so cannot truthfully answer questions on install or stops
but certainly all the turns limit to half standard tun rate and I have never had
any problems with full deflections and needing to Take-back-control. That said
i do get occasional dropouts in rough Wx and you dont notice until you see
that you appear to be driving off track.
Id have to investigate the settings for torque etc in my mine, and I need to do
it as they are not recorded anywhere so have no reference if they get
electronically
lost. I I get a chance this week Ill let you know.
Alan
> On 3 Jan 2023, at 13:10, David Cripps <dpc@knightonweb.com> wrote:
>
> So, I've slowly been making some progress on this, having mocked up the whole
system out of the aircraft. I have now been able to test it in the workshop and
yesterday in a car (it needed to be moving to get a track signal). See attached
photo. However, I now have a couple more questions/observations!
>
> i) It seems that the Skymap III that I used in these tests works in terms of
making the servo move and display a track on the Trutrak, so that's progress!
However, I note from the Skymap manual that it only gives its GPS info every 2
seconds, rather than the once every second that the Trutrak recommends to avoid
'wandering'. Peter, in your post you mentioned that you were using a Skymap
III - have you ever had a problem with this (assuming your A/P is the Trutrak
Digitrak too)? Alan, is the Garmin 196 that you've mentioned as suitable, able
to be set to give data at the 'once per second' rates, as from the manual it
seems it may too default to once every 2 seconds?
>
> ii) I noticed when testing in the car, that when the track that was displayed
in the Trutrak was close to what we were actually tracking (as read from the
Skymap), that the servo was more or less static, and moved in the correct
direction
when there was a small deviation between what was set on the Trutrak and
what we were tracking. However, because our roads are not straight, there were
frequently occasions when the actual track from the Skymap was miles away from
that set on the Trutrak. In that situation the servo went a bit crazy and
rotated
its arm by many more degrees than it could ever do in the plane. Is this
to be expected in this rather 'offline' mode? I can imagine that when the
Trutrak
senses that its control input is not creating the sort of aircraft track
change that it had expected, that it just moves the servo even further in order
to try to get aircraft to do something?
>
> iii) Clearly my mock-up does not provide any sort of 'force feedback' to the
servo control arm (ie the arm is completely free to rotate as it likes). In an
aircraft, would this be taken care of by aerodynamic feedback via the aileron
torque tube? What happens to the servo when it reaches the full movement that
the aileron would allow (the point when the control column hits its roll stops)?
>
> iv) I can imagine that I wouldn't want the servo ever applying full aileron to
create a turn as that would make for a very violent manoeuvre! I see that there
are settings that can be adjusted in the Trutrak set-up menus that control
activity level and also control maximum torque. What values have people set in
theirs? I note that when I have set the recommended value of 12 for the torque,
it is almost impossible to override the servo arm when the A/P is engaged
(though I appreciate that with no control column attached the leverage I can
apply
to the servo arm with my fingers is very low. I also appreciate that normally
if one wanted to override the A/P you would disengage it first).
>
> v) Lastly (for now!) has anyone fitted physical 'stops' to the servo body that
the servo arm would hit to ensure that the servo can never try to move the
pushrod
beyond the point where full aileron is applied?
>
> Apologies for all the questions but I want to make sure it is really working
correctly before I contort myself to fit it into the aircraft itself!
>
> Best regards
>
> David
>
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