Maja +APM help needed.

Hello everybody! 

Before the MAJA I had a partially home built flying wing and it was tracking the mission route like a bloodhound with default PIDs and no Autotune and just a little NAVL1_PERIOD modification down to 15.So I bought a Maja and now I am having extremely hard time getting it to fly straight not to mention to follow the line.

outside is a calm and sunny day and it is wobbling both vertically and horizontally and the line tracking is basically non existent.

attached is the TLOG and the param file,

my config is: 

Maja 220 airframe

Joker 3548-1100kv

12*6 folding prop

3 cell 16000mAh turnigy

AUW:3800g

many thanks in advance!

Tom

param flight.txt

2015-01-13 09-45-30.tlog

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  • The Autotune helped a little bit, increasing the rudder mix was a bad idea initially at that stage,

    now after the re-auto-tune might be a better idea as now the MAJA gains altitude in the turns.

    looking at the fpv camera it feels like the plane banks but the yanking is delayed .5 seconds. I'll try that next time. 

    I never get to go out and test 1 thing, I always test or do something that takes precedence, which is funny because I will not be flying anything is the plane falls out of the sky due to overstressed material. 

    • Pall, I hope you have reworked and reinforced the rudders and hinges on the Maja, as they are super sluggish and ineffective and especially the ailerons can have a negative yaw effect on the plane. I do replace the whole rudders on the Majas I build, but reinforcing should help.
      Folding props on a Maja makes no sense, as this airframe needs the motor on all the time and a fixed propeller is easier to balance.
      The Maja is very sensitive on a CG too far back, and on a poorly aligned elevon and wing geometry. Try to check the alignment and put the cg at least 5mm into the front and check again. The airplane should do a straight dive in manual mode when pushed into with no tendency to dive more or level out. And this airframe requires active steering on all three axis as it tends to slip through the curves. The airplane should fly good without autopilot first before trying to tune the ap-parameters.
      I use the Maja for aerial surveys a lot and if correctly tuned, its a good and reliable plane. I have flight times of up to 90 minutes and an area coverage of up to 100ha with an image overlap of 70%.
      Good luck and regards
      Marc
      • HI Mark,

        I dod not reinforce the hinges, but after aproximately 100 hours of flight they still hold with no problem. I had to change the motor, as I needed more power. A 10" prop is not enough for the 4kg AUW so I have 12x6 which touches the ground at landing. 

        I guess the main problem I created for myself is due to the 4kg. 

        Meanwhile I have Ironed out most of the problems I had, but there is one I couldn't iron out:

        it starts to turn arround ok, but in the second half of the turn it looses speed and altitude. NAVL1 is 20 and max bank angle is 35. it looses about 5-6 meters in altitude. I fly with 4*3000mAh 4 cell. 65ha in 40 minutes landing with 50% according to telemetry. 

        I would really appreciate a .param file to see the differences. What speed are you flying at? 

  • its snaking around, but the course is the same everytime, it just need some PID adjustments. the gains seems too big, so it overshoots everytime. have you already tried the autotune? what about navl1_period?

    one more things is the roll to yaw mixing. as the maja´s tail is so close to the wing, you may need to add lots of rudder with the aileron to keep the turns coordinated. have you tried that?

    also, a bigger distance between the lanes helps on the start of the line. keeping them so close forces the plane to a high angle, and the start of the line is very bad. with the wrong parameters it takes too long to align itself. 

    • I did the autotune and than reset the values to default as I didn't like the way it was flying and I started to adjust PIDs  manually. I managed to iron out the roll instability but it is still pitching up and down throughout the entire course. Demand height is 130m plane is flying between 125 and 133. it needs about 1000m to get it between 128 and 131.

      the snaking at the turns was somewhat solved by increasing the navl1_period from 17 to 18. Tomorrow I will try to increase to 19 to see what happens.

      Thanks for the idea with the additional rudder mixing. I will try that tomorrow, as well as a brand new autotune.

      I was better off with the flying wings, and they were more efficient too.

      unfortunately I cannot get the lines more apart as I need the overlap and the height is already 130m which results in almost 5cm/pixel (way too big for my taste:-)).

      what are you flying?

      Thanks for the Ideas again!

      • Moderator

        Its a very short coupled airframe so it will be very sensitive to CG position. Is it spot on recommended? I have never flown a Maja thats just an observation based on looks!

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