Discussions

Could Pixhawk fly conventional fixed wing for more than 40 minutes?

Posted by Anna Tian on January 12, 2015 at 11:35pm

Hi,

I’m a newbie to autopilot and Pixhawk. I plan to use Pixhawk to fly a commercial UAV (conventional fixed wing). But someone told me that Pixhawk’s attitude calculation algorithm will diverge if it flies for more than 40 minutes. Currently I don’t have a lot of time to learn about the autopilot algorithm and research into Pixhawk. I just need to choose an autopilot now.

Could someone here let me know is there any problem to have Pixhawk flying conventional fixed wing for more than 40 minutes theoretically? This might be a strange question. But I really need to confirm it. I’d also like to know about what attitude calculation algorithm does Pixhawk use, so that I could have a quick look into the introduction of that algorithm as well. Thanks.

Best,

Anna

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Replies

lvlei July 9, 2015 at 9:20pm

She is chinese
- eric > lvlei July 9, 2015 at 11:31pm
  
  哈哈
  
  Actually I think she is asking for others because she is good at English
eric July 9, 2015 at 8:54pm

Hi anna

你是中国人吗？

I'm also considering this question,and your threads inspire me ,Thanks

Just try the Pixhawk on Plane,it will be clear .

Are you in Beijing ,Beihang?
James Mark Borgaily January 16, 2015 at 10:45pm

Hi Anna

Its always a welcome to know more and more people are interested in autonomous flight. May i suggest try out using the APM boards, they are very well made, i own 3 and so far been pleased with them. I do plan Pixhawk in the future for the purpose of its faster hardware capabilities. They both use the same firmware at mission planner. Just be certain to really do the set up properly. i hope i could be of assistance and always willing to share my experience with newbies

Enjoy the flight

James.
Andre K. January 13, 2015 at 2:20am

There is no such limit.
Did the person have interests to spread such ridiculous lies ? Please say so if it was a commercial company, it's nice to know who uses lies to get a sale.
- Anna Tian > Andre K. January 13, 2015 at 6:06pm
  
  It's not a commercial company and he shall not have interests on that. Probably that's only a prejudice in his circle of friends. Engineers sometimes have special and impressive experience which usually make them have strong personal like or dislike. Never mind.
  
  Could we say the algorithm of the latest version of Pixhawk is state of art? And most performance difference between the so called milspec grade commercial autopilot and Pixhawk is from hardware but not algorithm?
  - Gary McCray > Anna Tian January 13, 2015 at 6:27pm
    
    I'm sorry Anna,
    
    But the issue you describe, is simply not an issue.
    
    Presuming you are using GPS, it will happily fly where you want for as long as you have power to do so, days shouldn't be a problem.
    
    And it has nothing to do with "the attitude algorithm" - it goes where the GPS and it's programming tell it to.
    
    That said, the current "attitude algorithm(s) are excellent and the plane is very stable & competent in flight.
    
    I don't know where you are getting this line of inquiry from, but it actually sounds naive to this group to even say something like that.
    
    A failure to grasp the basic operating principals of all our auto-pilots.
    
    Pixhawk is very solid at this point and length of time flying is in NO way a limitation.
    
    Best Regards,
    
    Gary
    - Moderator
      
      Sgt Ric > Gary McCray January 13, 2015 at 7:20pm
      
      Is there a language problem here? "Attitude algorithm", do you mean the autopilot software? People have provided links to the software code, but you say you don't have time to look at it. I don't get the issue here.
      - Anna Tian > Sgt Ric January 13, 2015 at 11:40pm
        
        Sorry for the confusing words here. I should've expressed it more clearly. I meant I didn't have time to analyze the accuracy and stability of the relevant algorithm from the detailed mathematical formula. I was looking for the name of this algorithm so that I might be able to google the name of this algorithm and read the advantages and drawbacks of this algorithm from some websites like Wikipedia.
        
        Next time I will spend more time to express my question more clear. Sorry, Sgt Ric.
        
        Dan Wilson > Anna Tian January 14, 2015 at 3:59am
        
        Hi Anna,
        
        Someone please correct me if I'm wrong but as far as I know, the pixhawk has an EKF to estimate the full state but it's quite new and is disabled by default. The attitude estimate algorithm, at least used to be based on the DCM explicit complimentary filter as proposed by Rob Mahony. It basically integrates the gyro measurements, then corrects the attitude by assuming the sensed acceleration is gravitational. There's likely some other math in there to calculate and remove body accelerations to ensure the acceleration is mostly gravitational. I think there are also some PI controller inspired components to account for gyro bias.
        
        As far as I know, the filter shouldn't diverge in normal conditions.
        
        Hope this helps.
        
        Dan