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Test firmware build ready — commit 5f746e4

Download firmware for PR #11595

237 targets built. Find your board's .hex file by name on that page (e.g. MATEKF405SE.hex). Files are individually downloadable — no GitHub login required.

Development build for testing only. Use Full Chip Erase when flashing.

@breadoven Firstly I want to start by saying how much we all appreciate your work here on INAV. ❤️
And what follows is not ingratitude. But rather, just putting the facts out there.

When I setup the fixedwing auto speed mode with the IPF. I also tried a simplified version as you have here. But found it was just too lacking in many area's of safety of operation, and efficiency.
I noticed you mentioned many of these other issues. But I thought a rundown of why I added these extras, might help.

Example:

• The Min and Max throttle value the throttle controller can use. Plays a big part in how efficient the system can work. So their addition is practically a must.
  Plus if you do add those setpoints. It isn't a good idea to share them with nav_fw_min_thr and nav_fw_max_thr. Because altering them will significantly effect the way Pitch2Thr works when not using auto speed mode.

• I also tried using the throttle stick to set the speed target.
  It only worked very average. Because whether you fly with stick mode 1 or 2. Most of us move the throttle stick little by little as we make an aileron or rudder input. Causing the target speed to shift, and constantly require resetting.
  Even with a throttle deadband. It still occurred when flying in Acro.
  And using the throttle stick to set the speed target also rules out a safety shut off of auto speed mode. As you would have noticed. I used a delta (mildly faster) movement of the throttle stick, to exit auto speed mode if an emergency happens. Which it did once. And by pulling the throttle lower or even higher, it switches back to manual throttle control.
  I know the addition of a pot for speed target control, requires the use of an extra channel, But it does make it worth while. However I also tried just having the target setpoint being hard set as well, to a cruise speed that suits the pilots requirements. That too work well if channels are lacking.

• I also found that 3Dspeed required the "tailwind" safety airspeed throttle-up addition, to stay ahead of a low airspeed stall, if the plane was commanded to climb manually or by nav control when in RTH or a mission.
  Which would also require a setting, but I found it was absolutely worthwhile from a safety stall perspective.

• And Airspeed target was something that I noticed many people asked about. And i did find it advantageous for flight efficiency. The main time 3Dspeed was better, is if you wanted to make good headway into a strong headwind. And make it to your destination faster.

• I also found having the auto speed Throttle element on the OSD helped to determine how well the system was working. It provided a good visual reference when tuning and when commanding a steep dive or climb, so you could see how efficiently throttle was being feed-in, to hold the target speed.

I no this was long winded. And I'm not trying to make more work for you. But I thought it might be helpful for you to know what I also tried. So the feature can be made safer and more user friendly.
Plus if this feature is implemented to a higher standard, it leaves the door open for so many better fixedwing improvements.
e.g.
Fixed airspeed when running autotune. Which provides a more accurate FF and Rate tune.
I also tried using in with AutoLaunch. It also improved climb out efficiency, without risking a stall.
And it also help slow the plane, without risking a stall, when I tried it with fixedwing auto landing mode.

@Jetrell I probably should have said this is a work in progress. The initial build was just for basic testing in light wind but obviously is limited otherwise.

I've made some changes in the latest commits:

Added pitot
Pitot will be used by default if available. There is no means of actively selecting between pitot and ground speed ... at the moment. One issue with the virtual pitot I noticed is that its usage isn't dependent on isEstimatedWindSpeedValid so that's been added. However, the check for isEstimatedWindSpeedValid doesn't look too useful with it typically taking 15 mins to timeout and become invalid if you're not manoeuvring. This seems to have come from the research paper used for the theory but doesn't seem realistic for real world use. I think a shorter time period should be used here, probably < 5 mins.

Added stall protection when using ground speed
This is based on existing cruise throttle and pitch2throttle and sets the minimum allowed throttle.

Added low ground speed protection
This uses the existing logic which works albeit crudely but I guess it's really just a last resort thing. One issue here is the Nav Pos and Alt controllers shut off if ground speed drops below 3m/s. This doesn't make sense if you have a pitot so the logic needs reconsidering where airspeed is available.

Added a NAV_CTL_SPEED flag
Allows activation in all Nav phases where it makes sense including during most Auto landing phases.

Things that need further work:

1. Adding Max/Min throttle settings - this is trivial to do so not an issue. Although is this not more related to Max throttle than Min ? As mentioned above min speed using ground speed is dynamically set by cruise throttle and pitch2throttle settings. And with pitot I don't see the issue with allowing idle throttle, e.g. in dives.
2. Using speed demand methods other than throttle - probably a personal preference thing but I can see the issue with the other control axis upsetting the set throttle position.

I also found having the auto speed Throttle element on the OSD helped to determine how well the system was working. It provided a good visual reference when tuning and when commanding a steep dive or climb, so you could see how efficiently throttle was being feed-in, to hold the target speed.

I'm not sure what you mean here. The normal OSD throttle display shows the Auto Speed throttle setting the same as any other auto throttle mode. The only OSD element that's been added for this PR displays the selected speed, (300U) or (ASPD) if Autospeed mode is ON but not active. This could be changed to show if airspeed or ground speed is being used I guess, e.g. G: 300U vs A: 300U.

isEstimatedWindSpeedValid doesn't look too useful with it typically taking 15 mins to timeout and become invalid if you're not manoeuvring.
I think a shorter time period should be used here, probably < 5 mins.

I totally agree. The wind can swing in as little as a couple of hundred meters. So 15mins seems extreme. I figured it was just set this high, so virtual wind/airspeed wouldn't become invalid and cause issues with something that was relying on it.

Although is this not more related to Max throttle than Min ?

Max throttle is more beneficial for power efficiency. But limiting Min throttle to a value higher than zero. Has two benefits that I found.

1. The first could stop a possible ESC desync, in the case of the plane pulling a loop in Acro mode. It will shut the throttle down in the diving half of the loop. And then the p term will apply Max throttle in the climbing half of the loop. I've seen it throttle-up very hard and fast.
2. The other is that a propeller (disc) that is spinning at lower speeds creates more drag, than a propeller that has stopped spinning. This is useful to help the auto speed mode hold the target speed in a dive.

The normal OSD throttle display shows the Auto Speed throttle setting the same as any other auto throttle mode. The only OSD element that's been added for this PR displays the selected speed

Sorry, I could have worded that better.
What I meant was not Nav Auto throttle.. It's OSD element will be displaying what auto speed mode is outputting when the plane is in a navigation mode.
But when the plane is in Auto speed mode and flying in Acro, Angle , AngleHold, Horizon or Manual. That OSD element will only display the manual throttle value. Not the output of the Auto Speed mode controller.
That was why I mentioned having it as its own throttle element is very useful.

1. The first could stop a possible ESC desync, in the case of the plane pulling a loop in Acro mode. It will shut the throttle down in the diving half of the loop. And then the p term will apply Max throttle in the climbing half of the loop. I've seen it throttle-up very hard and fast.

There is filtering on the throttle output that damps the rate of change so maybe it's not an issue in this case.

2. The other is that a propeller (disc) that is spinning at lower speeds creates more drag, than a propeller that has stopped spinning. This is useful to help the auto speed mode hold the target speed in a dive.

This PR honours motor stop where applicable, Acro, Manual etc, but it could be changed to prevent that and have Idle as the minimum allowed always. I left motor stop behaviour as is to avoid surprises, e.g. in Manual, although that could be fixed by only allowing activation when in flight.

The normal OSD throttle display shows the Auto Speed throttle setting the same as any other auto throttle mode. The only OSD element that's been added for this PR displays the selected speed

Sorry, I could have worded that better. What I meant was not Nav Auto throttle.. It's OSD element will be displaying what auto speed mode is outputting when the plane is in a navigation mode. But when the plane is in Auto speed mode and flying in Acro, Angle , AngleHold, Horizon or Manual. That OSD element will only display the manual throttle value. Not the output of the Auto Speed mode controller. That was why I mentioned having it as its own throttle element is very useful.

This shows the Auto throttle OSD display whenever Auto Speed is active, so it also works for non Nav modes.

although that could be fixed by only allowing activation when in flight.

I think that would be a good way to go about it.