PFD unstable when airspeed is enabled

Hi everyone, This is my first Forum/ APM Experience... I am trying to have my X8 fly with the airspeed sensor but I am having a really strange behavior. 

I have the APM 2.5 directly from 3Drobotics, Came totally assembled with their Airspeed sensor. I loaded the version 2.73 of Arduplane and basicly trew the aircraft in the air after a couple of ground tests. 

On the groundm what bugs me the most is the PFD moving up and down a couple of degrees (+- 5) at about 1hz This happens only when the ''use airspeed'' fonction is enabled otherwise the PFD is rock solid. (no need to mention that the plane is level and not moving. )

The Airspeed sensor is also quite erratic itself when on the ground but I thought no big deal since the sensor usually is not accurate for small pressures diferences. 

Flew OK but there are a lot of strange behaviors in the air as well... First one is that It would slow the throttle down when in downwind... Usually if it would be flying with a true airspeed it should increase throtle to compensate the altitude loss of a more agressive bank turn... Seems tol me like it is in fact flying Ground speed while in Airspeed mode and the reverse is true, It would increase throtle when in downwind if the option is disabled... 

It might sound quite confusing. So I would like to know if there are solution to theses problems : 

1. Why is the PFD is ossiclating when ''use airspeed'' is enabled

2. Is there a way other then the ''use airspeed'' variable to know if the APM is using and thrusting the airspeed sensor. 

Thanks! 

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –

Replies

  • Developer

    Hi Michael,

    The airspeed being erratic on the ground is normal, as the airspeed goes as square root of pressure difference. It will settle down once you above about 5m/s, and get more and more accurate as it gets faster. Do make sure you calibrate it though, by plotting airspeed and groundspeed from a flight pattern and adjusting ARSPD_RATIO.

    The PFD (which we usually call the HUD in this forum) should only be affected by the airspeed if you don't have GPS lock. Once you have 3D GPS lock the APM will use the GPS velocity numbers to do centripetal correction. If you don't have GPS lock it will use the cross-product of airspeed vector with the gyros, which is why it affects attitude at very low speeds.

    To know why it is lowering the throttle downwind I'd need to see a tlog (telemetry log). If flying with ALT_CTRL_ALG=0 and ARPSD_USE=1 then it should be adjusting throttle to maintain airspeed.

    You might also like to try the new 2.74beta3 release with ALT_CTRL_ALG=2 to use the new TECS speed/height controller. That is a much more sophisticated airspeed controller, and will completely replace the existing controller in a future release. Have a look at the tuning guide for more information.

    Also have a look at the tuning guide for the new attitude controllers. Those include better roll compensation factors.

    If you post a tlog then we can go into a more detailed analysis of the flight.

    Cheers, Tridge

This reply was deleted.

Activity

DIY Robocars via Twitter
Friday
DIY Robocars via Twitter
RT @_JonMyer: 🏎 We need your help in naming my #AWS DeepRacer Underground Track 🏎 @davidfsmith's track is going to be referred to as 𝗔𝗪𝗦 𝗗…
Oct 22
DIY Robocars via Twitter
RT @gclue_akira: 仕事もおわったし、電脳化にとらい #マリオカートハック https://t.co/4IU90hCLgm
Oct 22
DIY Robocars via Twitter
This is the hashtag to follow all the people in Japan who are hacking the new Nintendo Mario Kart with the real AR… https://twitter.com/i/web/status/1319281354664677376
Oct 22
DIY Robocars via Twitter
RT @gclue_akira: @chr1sa @diyrobocars jupyter mario https://t.co/P0oHdjlCRq
Oct 22
DIY Robocars via Twitter
RT @_JonMyer: 🚨Our 1st AWS DeepRacer Community Race is Underway on http://twitch.tv/aws 🚨 Join us to find out which member of your commu…
Oct 20
DIY Robocars via Twitter
Oct 19
DIY Robocars via Twitter
RT @BackyardRobotcs: After an admittedly long wait, the new Tinymovr R3.3 motor controller is now available https://tinymovr.com 🥳
Oct 19
DIY Robocars via Twitter
RT @_JonMyer: 🏎 1 hr left before the #AWS #DeepRacer Community 🏎 Top 5 Race tomorrow LIVE on Twitch 1st Place = $50 Amazon GC or AWS Credit…
Oct 19
DIY Robocars via Twitter
Oct 16
DIY Robocars via Twitter
Oct 15
DIY Robocars via Twitter
Oct 14
DIY Robocars via Twitter
RT @davidfsmith: Race virtually with The AWS DeepRacer Community Race and then join us on the track to see how your times compare on the ph…
Oct 14
DIY Robocars via Twitter
Oct 14
Hiroki Tanaka liked Hiroki Tanaka's profile
Oct 13
DIY Robocars via Twitter
RT @breadcentric: It's now!
Oct 13
More…