Developer

APM:Plane 2.74 released

The APM dev team is delighted to announce the release of APM:Plane 2.74, a major new release with a lot of new features. This release is recommended for anyone flying fixed wing aircraft with an APM2 or PX4.

There are a lot of changes in this release, but some of the highlights are:

  • new APM_Control attitude controllers.
  • new TECS speed/height controller from Paul Riseborough.
  • two new flight modes, ACRO and CRUISE
  • new camera trigger by distance system, for better aerial mapping
  • dozens of small fixes and improvements from two months of development
  • lots more documentation, including tuning guides for all the new parameters

Scroll down for a more complete list of changes, but before that I'd like to give you a bit more detail on the highlights above.

New Attitude Controllers

The new "APM_Control" attitude controllers have been in development for a long time. Originally developed by Jon Challinger last year, they were extended by Paul Riseborough and made compatible with the existing parameter names. The key advantage of these new controllers is their improved handling of noise, and much better ability to tune for your aircraft. There is a new tuning guide in the wiki which gives detailed instructions on how to make the most of the new capabilities.

One of the big effects you will see with the new attitude controllers is better handling of pitch compensation in turns. The new PTCH2SRV_RLL parameter makes tuning for flat turns much easier, which has been a major source of frustration in the past.

The new controllers also handle sensor noise much better, especially if you use any D term in your roll or pitch controllers.

New Speed/Height Controller

The new TECS speed/height controller is the second major controller change in this release, and will make a world of difference for aircraft with an airspeed sensor. After a lot of testing I decided to make TECS the default in this release, although you can switch back to the old controllers using the ALT_CTRL_ALG parameter if need be. If for some reason you find you do need these old controllers then please let me know, as I am planning on removing the old controllers in the next release.

The previous airspeed controller for speed/height suffered from a major problem that it gave absolute priority to airspeed. If the aircraft could not achieve the target airspeed you had set then it would dive to gain speed, even to the point of diving into the ground. This made it quite fragile, and you had to be very sure of your airspeed configuration.

The new controller operates over a range of airspeed values, set using the ARSPD_FBW_MIN and ARSPD_FBW_MAX parameters. That controller will try to meet both the airspeed and altitude demands of the mission, but if it can't reach the target speed it will happily fly a bit slower, as long as it doesn't get below ARSPD_FBW_MIN. You can control the relative priorities of speed versus height using the TECS_SPDWEIGHT parameter. See the full tuning guide for details.

New ACRO flight mode

After a suggestion from Thomas in the 2.73 release thread, we have added a new ACRO flight mode.

This modes brings rate controlled stabilization to APM:Plane, and should help give you an "on rails" manual flight experience. It is a lot of fun to fly, but it is not for beginners!

We're planning on expanding the ACRO mode in future releases. Right now it is great for "locked in" flying, and also good for loops and handles inverted flight very nicely. It doesn't yet handle knife-edge or prop-hanging.

New CRUISE flight mode

After a suggestion from Hein, we now have a new CRUISE flight mode. This mode is ideal for longer distance flying without a pre-programmed mission. It is like FBWB, but also does ground track heading hold, with heading update via aileron or rudder.

I've been testing CRUISE at my local flying field, and it is the easiest mode to fly in APM. Just steer the plane around the sky, and when you stop steering it locks onto a ground track and holds it. It isn't a good mode for takeoff and landing, but once you are in the air it is great.

New camera trigger system

When using APM for aerial mapping where you want photos taken at regular distances, the previous system was to setup a grid mission with a "camera trigger" mission item at regular intervals within the mission. That worked, but led to overly large and complex missions. You can now just set a single parameter CAM_TRIGG_DIST to the number of meters of flight between photos, and the APM will take care of when to trigger the camera. This makes for much simpler missions, and also works in other flight modes, including FBWB and CRUISE.

Lots of smaller changes

As is usual with a new release after a couple of months of development there were a lot of smaller improvements based on feedback from users. Many thanks to everyone who gave feedback and contributed patches!

Here is a partial list of the changes:

  • added new GND_ALT_OFFSET parameter for ground station barometric correction
  • made it possible to set the failsafe battery voltage and battery level at runtime via parameters
  • added MIXING_GAIN parameter for controlling the elevon and v-tail mixers
  • fixed stick mixing range in AUTO modes  (thanks Soren!)
  • fixed mode logging in dataflash
  • added support for the EagleTree I2C airspeed sensor on PX4
  • added new RCMAP_* parameters for re-mapping control channels (good for DSM and SBUS receivers on PX4)
  • made it possible to configure board orientation at runtime, to make setup easier without rebooting
  • switched to new task scheduler for more accurate internal timing
  • added a new RELAY_PIN parameter for setting up camera trigger via a digital pin
  • added secondary rudder support, useful for when a separate servo is used for a nosewheel and the rudder, or for v-tail planes with nosewheels
  • fixed RTL glide slope when starting above the target RTL altitude. Descent should now be smooth over long distances. Many thanks to Kitsen13 for raising this.
  • fixed a bug with FBWB airspeed control. Many thanks to Gabor for reporting this
  • Added FS_LONG_TIMEOUT and FS_SHORT_TIMEOUT parameters. Many thanks for the suggestion by Aleck
  • fixed handling of deadzone parameters on RC channels. Many thanks to Soren for reporting this
  • many small C++ fixes from NeuroCopter. This sort of detailed review of our code is much appreciated!
  • fixed analog in handling with some unusual devices - thanks to Andi for noticing this!
  • added support for apparent versus true airspeed calculations based on pressure altitude, for better flight control at higher altitudes
  • avoid writing unchanged bytes to EEPROM, for faster updates and less wear on the chip
  • cope better with large yaw changes in the AHRS code
  • improved the reliability of USB connections on PX4
  • added PX4 support for RELAY (thanks to Marco Bauer)
  • fixed handling of high spin rates in AHRS (thanks Jurgen!)
  • removed support for the old APM1 1280 based boards.

This new release has a lot of new features that should improve the flying experience for all APM users. The APM dev teams wishes all APM users many enjoyable flights, and we hope you have as much fun flying this release as we had making it.

Happy flying!

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Replies

  • Well done!

    I went flying today with 2.74b and I have to say that it works perfect. I had a strong wind but the plane managed to fly as precisely as it never did before. The new TECS control allows to make rapid climbs without overshooting or oscillating.

    I flew mostly with the standard parameters and did no fine tuning. Even in turns the plane kept its given altitude.

  • Hello,

    I have used the TRIM_AUTO feature before as it sounded like a good idea. What are the developer's thoughts on this?

    Thanks,

    Steven

  • WoW! Great new features. Can't wait to try it on my scratch build test tank :) Thanks all the developers and suggesters of new features!

  • Hi Guys,

     

    may someone explain to me the right procedure to calibrate the airspeed sensor?

    I looked in the guide but I've not found anything.

     

    Thanks a lot!

  • Andrew, Paul

    Thanks so much for the excellent explanations and all your work to get this out to us. I am heading out tomorrow to do further tuning based on your suggestions.

    Thanks again

    Al

  • You guys ROCK. I can hardly wait to fly it! Thank you so much.

  • Hi,

    The activity seems high so I will ask a question I had about 3 months ago. Is there a way to check RTL operation on the ground? When I originally asked it was because I had "twitching" my rudder (3 Ch plane) in the RTL mode while on the ground. It was almost like some kind of Morse Code, a couple of short and some long twitches. I had GPS lock and HDOP was below 2.0. Before I could test it in the air, there was another release of firmware and the twitching went away. I didn't look back. However, with 2.74, the twitching has reappeared. Any help appreciated.

    Thanks,

    Steven

  • Paul

    Can I ask - If I am using arduplane without an airspeed sensor (I have some on order) should I use the default TECS speed/height controller on or disable it until the airspeed sensor is installed and calibrated?

    thanks

    Al

  • Moderator

    Has anyone got a working set of parameters for the SIG Rascal in the Flightgear HIL simulation?

    With v2.68 HIL I was able to get a stable plane that replicated the real life behaviour of a plane but in v2.74 HIL the plane is all over the place and I'm battling to get any sort of stable flight.

  • Hi there, I have installed this in to an X5 airplane... here are my issues if you can help please.

    1) I have the plane flying in manual mode well nice and level

    2) in FBWA mode I can tune my aileron response so that nav roll and roll are very good and responsive in the graph

    3) in FBWA mode I can NOT seem to get my pitch to keep up with the nav pitch. This I believe is causing some very large radius turns. I have NAV p term set all the way to the max at 1.0

    4) I have redone the calibration on the radio with limited endpoints on the roll in order to gain some pitch authority. This did work but not enough.

    5) I have increased the mix on the elevon mixing (in advance paramters) but anything past .7 means the plane is very difficult to control in stabilized mode.

    What I see here is the need for separate elevation and aileron "mix gains" not nav gains but mix gains.

    I have also noticed that when in stabilized mode I get pitch more authority compared to when in FBWA mode.

     

    I have attached a log file of one flight... any help appreciated!|

     

    Steve

    2013-07-16 21-23-30.tlog

    https://storage.ning.com/topology/rest/1.0/file/get/3692774803?profile=original
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