Thanks for the .bin file. Something is going on here that I can’t fully explain. The plane does point up and then starts to fly backwards when you invoke QRTL. This may be because you are not pointing to home and the plane is trying to stop. You could try a test where you are pointing to home and then invoke QRTL. It would also be wise to be downwind so that the nose of the plane is facing the wind for stability. Your Q_WVANE_GAIN setting is currently at 0.
It seems that QRTL is only valid for about 3 seconds before you switch to QLOITER mode. The first two images are when the plane flips up on QRTL and the third image is when it is going backwards in QLOITER mode. The second image is looking down from above.
[Edit]: replaced attitude tracking plots with gain plots
thanks Greg. you’re right in this case the plane is pitching up because i had to put the plane in a tail-on attitude to make sure i wouldn’t be disoriented if i had to recover manually, which happened frequently. Due to the limitation of obstacles nearby, it is safer for the drone to face the wind (not via auto weathervaning) and pitch up to go back home. QRTL trajectory is okay as far as altitude and position are concerned, but the pitch attitude response is unsatisfactory. Too much overshoot. I don’t think QRTL gives the wrong pitch order, but the airframe response to the pitch order needs tuning.
I did three, four Qautotune flights in the pitch axis and it looks like the tune is unsuccessful. RAT pitch gains never changed after landing and disarming while in Qautotune mode. I checked DesPitch and actual pitch plots but it looks like DesPitch does not incorporate Qautotune command, so it just showed a couple of spikes (twitches). MP plots the gain changes along with the messages but the messages are hard to see as they overlap each other on the axis.
I had to cut back to Qloiter this time as the maneuver turned quite violent and involved roll and yaw changes as well. I think Qautotune may not work for me, but so far the current gains provide for a very flyable handling quality. I have no problem controlling the drone in any of the Q modes, even against a stiff wind. It is only when the pitch command is very abrupt, such as those of QRTL, that the response is unsatisfactory. Even then, pitch down to go home behaved better than pitching back to go home.
https://1drv.ms/u/s!Auv-5QlGCPQop3HtYLJ_uIParQEW?e=aqwnvS
Password = Password if required.
Logs and video from my flights today a bit of FBWA and a second flight of Loiter. Really happy with performance however I do need to change Max speed 24m/s is way to fast for me. actually calculating airspeed calibration - manual a/s 18m/s = GS of 16.75. So I’ll have to adjust my ratio from 1.77 to 1.54. and I will change my Aspd max to 21. Servo auto trim makes flying so much easier and my Q_Assist modes all appeared to be working well. I got plenty of warnings in FBWA . Transitions were ok - not concerning but a little ugly. In my long Loiter flight I even managed to relax enough to follow MP on the laptop and change loiter settings. Simple mission is next from manual takeoff.
spetsnaz26, I’m definately a beginner but my understanding is if changing from Fixed wing mode to a Q_Mode. QRTL and QLoiter use GPS so tries to gain immediate stationary Hover, which causes the ‘unsatisfactory behaviour’. Q-Hover doesn’t use GPS so is much gentler and glides to the hover whilst maintaining altitude > Nil aggressive pitch. Just a thought
thanks. i started QRTL while stationary so it was just the plane’s failure to properly track a pitch command. it’s damped well and does not oscillate, but overshoots way too much. I will manually tune the PID following the guide in the doc.
hey people I had my first successful transition today to FBWA and flew a few minutes without any major problem. I did however had violent roll and yaw oscillation during the initial few seconds of the transition into FBWA, and it looks like the VTOL servos got into a constant amplitude oscillation with a phase diff of 180 degrees. it did converge later when speed picks up. I don’t have access to my param right now so I can;t plot the RC outputs, but a working theory is a PID problem that turned manageable yaw error into a borderline accident. I’ve not heard anyone else talking about it in this thread so I will look around elsewhere, too.
FBWA was okay, if sluggish. I flew FBWA with my small fixed wing trainer a number of times before, including once with aft CG, and the control characteristics is not that different. There’s a constant need to put int nose down stick probably because my autopilot level is set a few degrees too high, at least for the speed i was flying at (~60mph, crazy!). I had several stall accidents before, and instinctively carried too much speed.
with one 6000mah battery (whopping 853g). my hover throttle is 35% and current 25A. while flying in fixed wing mode my current draw isn’t much lower, probably because I was gunning for high speed. as I get more experienced and more confident, i will try to loiter around at a more economic speed, maybe something like 16m/s or so.
hey people in case anyone’s bothered by the same transition yawing/rolling instability, before the developers come up with a formal fix, just make sure your q tilt max is small enough. I was using 65 and got into violent oscillations. I then changed it to 40 and the transition is free from oscillatory motions, although there is now a strange left yaw tendency which can be checked by yaw and roll control.
The Q_TILT_MAX works in combination with the Q_TILT_RATE_DN and FBWA_MIN settings. Having a higher Q_TILT_MAX (like 65) works in conjunction with a slower Q_TILT_RATE_DN and lower FBWA_MIN setting.
So for a tilt-rotor, the motors will tilt to the Q_TILT_MAX setting at the rate of Q_TILT_RATE_DN to build up air speed until the FBWA_MIN setting is reached. These numbers will vary on your plane setup and power level.
You can also play with the Q_TRANSITION_MS setting. I think lowering the value (in milliseconds) lets the plane start flying normal faster.
makes sense. Goes to say it takes quite a bit of tinkering and thinking to get it right. I will do more test flight in the coming days to practise transition.
One thing though, I re-read that page about transition, and the part about tiltrotors are mixed in with quadplanes’. It says that if you go less than half throttle, the rotors will tilt backwards. I wonder how this will affect transition. It looks like you have a certain degree of freedom to transition more slowly by commanding less than 50% throttle, and effectively use a less than Q Tilt Max angle, and it will take longer to reach minimum speed. then it will go down at Tilt DN rate. My problem now is that the motors are over-powered. They maintain hover at 35% throttle or so, and if I maintain 50% at transition, this thing bolts forward at 0.8g and reaches interstate speed within seconds. I don’t want go that fast, and I want to find out if there’s a technique to reach more economical speeds more smoothly.
I’m hoping for some assistance - After several successful flights I took the nimbus out today and didn’t get of the ground right tilt servo does not appear to be working. I have reloaded parameters and reloaded Arduplane 4.0.7, with no effect. I have attached the Bin and Parameter files for perusal. Next plan is to swap the L&R tilt servo leads on the pixhawk to try and identify the fault. My knowledge unfortunately for interpretting the logs is limited.
User Error - Or issue when playing with SITL Servo 10 - had changed to 10 from 76 - I had just reinstalled my MAP-02 so probably as part of that process…Anyway certainly something to be said for Preflight checks - we live to fly again…we live and we learn.
Those are two different functionalities. Typically, I always use the SERVO_AUTO_TRIM function to keep the plane flying level. However, I have never used QAUTOTUNE and have only used AUTOTUNE on one small foamie called the Wing Wing Z-84. If my VTOLs need a tweek due to some wobble or slow response, I land and make the adjustment and send it back up. It’s rather old school but helps to keep me safe.
i used autotune in both helicopter and fixed wing mode. Q didn’t work for me, but fixed wing autotune apparantly had some success tuning up the roll P gain. you need to read the documentation closely as it can inadvertently tune into unstable territories.
New to this group.
Awesome information here. I’m waiting for Nimbus kit to arrive and start building.
I have moved from Pixhawk to Matek FC’s the last few years on some of my previous builds.
Has anyone build a Nimbus VTOL yet with a Matek F765?
@GregCovey thanks Mate.
Been busy building and flying a few quads and hexacopters as well as fixed wing fpv platforms.
Haven’t been doing a lot of building or much flying the last few months due to international work commitments.
Been following the Nimbus VTOL project with interest.
Definitely going to be hitting you up for more info and advice in the future.
