Try resetting to 921.6K baud using a web browser: http://192.168.4.1/setparameters?baud=921600
Documentation is here: https://github.com/dogmaphobic/mavesp8266/blob/master/HTTP.md
I too noticed some goofy behavior with regard to MIN PWM. Is there a way to set it individually for each motor? My ESCās have also been calibratedā¦
The PX4 software certainly leaves a little to be desired tuning wise. I have the PID sliders all the way down, I would LOVE some fine grain control! Can anyone give me tips?
Likewise the PX4 mode settings are VERY odd when when you are not indenting to use GPS. It seems to want to force me into having a Auto mode (albiet greyed out) in the config UI. I just want Acro and stabilize mode! Any work around on that?
Here is the maiden flight of my 180mm Sasquatch Labs Shuriken running PX4 flight stack
Finally got a day of reasonable weather, and went outside with my QR400 and Pixracer for a proper maiden flight. Glad to say that everything came back home in one piece 
My feedback as to the results goes as follows:
##Flight performance
Manual/Stabilize: good. Stock QAV250 PIDs seem adequate, however slight oscillations can be heard during throttle punches. Stick reactions are good, if a bit tame. Nicely flyable.
AltCtrl: very good. Altitude lock-in is absolutely solid (despite the Pixracer being hard-mounted with no vibration isolation), stick reactions same as in Manual.
PosCtrl: good. Position lock is good. Stick reactions and flyability generally very tame, I guess Iāll have to increase top GPS speed and controller aggressiveness a bit.
RTL: good. Despite what I presume is a bad compass calibration (more on this below), the copter returned straight to launch point on both tests. Descent seemed a bit aggressive, I switched to manual both times before it landed.
Acro: bad. Stick reaction latency is good, but thatās about it. Attitude lock-in is virtually non-existent, copter keeps slowly drifting along all axis once right stick is returned to normal. Itās flyable, but nowhere near the precision of currently dominant acro controllers (specifically Cleanflight/Betaflight). If the Pixracer/PX4 combo is supposed to be competitive in the racing scene, there is a lot of work to be done here.
##Other issues
During most of todayās flying, the copter exhibited a steady yaw drift to the right. It was barely noticeable in Manual, but very visible in PosCtrl, and for some reason also in Acro. On some occasions it could be fixed with yaw trim on the TX, but I donāt think this is the issue at hand, because I had to adjust trim a lot between modes to get it to fly straight.
I presume the reason is bad compass calibration, which Iāve done indoors in a potentially very EM-noisy area during initial setup. I wanted to re-do the calibration in the field, but had another issue that prevented me from doing that, as well as from trying some PID tuning to improve Acro performance:
Wifi connectivity with the ESP8266 (using an Android tablet with QGC) was horrible. I had constant āconnection lost to vehicle 1ā¦ connection regained to vehicle 1ā messages, during the connection and after itās completed. Also, each time after connection QGC said that āthe vehicle failed to transmit the full parameter listā, which meant I couldnāt edit the PID values or go into the compass calibration screen.
The issue here could be that I used a PX4 master build from two days ago, which is when I set the vehicle up and had the first test hover indoors. Back then, the Wifi connectivity definitely worked, I used the tablet to calibrate ACC and compass initially. Itās possible that QGC has auto-updated since, and something changed so that my PX4 build on the Pixracer is now out of date.
Final small thing: is there an option to improve MAVlink packet rates on the Telem2 output? I have an OSD connected there, and both the artificial horizon as well as Speed/Altitude readouts update really slowly, like at 1Hz or something. This is pretty horrible, the OSD itself should be able to update at 10Hz easily (itās a PlayUAVosd).
##Logs
Log of flight with Acro/FPV: http://logs.uaventure.com/view/m3djQoNDSvrYyfF4s87Ayb. Acro doesnāt seem to show correctly in LogMuncher, it should be the second large gray block on the graph: I first parked the copter in PosCtrl, put on my FPV goggles, then flew around a bit in AltCtrl before switching to Acro. Large PosCtrl block after that is me putting the goggles back down and returning the copter to launch position.
Log of pure LOS flight with a lot of yaw drift: http://logs.uaventure.com/view/sk6hPhoMUdyHqJbfMYcQoS. You can see nicely how thereās a ton of uncommanded yaw drift during PosCtrl, and less (but still some) during Manual flying.
##My next steps
- Update PX4 to the latest master build, keeping all settings. Check if this fixes QGC connectivity issues and allows me to calibrate the compass in the field.
- Recalibrate R/C to exclude the possibility of yaw channel center being offset and causing the yaw drift.
- During the next flight, when QGC connectivity works properly: try and tune the PIDs for better Acro performance. Increase Rate-I for all axis to minimize drift, possible increase Rate-P for better lock-in. Probably decrease Rate-D to prevent the audible oscillations during throttle punches in Manual.
1 Like
Thanks for the feedback, especially on Acro mode. I suspect it is never used by the guys flying in Auto modes. When you say āAttitude lock-in is virtually non-existentā, are you comparing to Cleanflightās āHorizonā mode, or pure Acro?
Pure Acro. The āRattitudeā mode of PX4 should be equivalent to CFās Horizon, but I havenāt tested it. I fly FPV in pure acro a lot on my other quads, so Iād really like to have solid acro performance on the Pixracer as well.
Iāll put in some more time with Cleanflightās Acro mode to see what might be causing the difference. What are you using for max roll/pitch rates in Acro mode? The current default is 360 deg/sec. Iām pleased to hear that you find control latency to be good compared with your other quads. That means we should be able to at least match their performance.
And Iām glad to hear that you like ALTCTL; weāve been working on that a lot with the PixRacer. I assume you covered the baro; are you using foam and/or a case?
I had all rates (and mostly all settings) at default during todayās flight. 360Ā°/s is slow compared to what 250/210-class racers with Betaflight achieve (those things can turn 3-4 loops in a second and then stabilize perfectly level), but should be adequate for my 400-class frame.
The main issue was the lack of lock-in with the stick released. When you release the right stick in acro on a Betaflight racer, it locks in instantly and maintains pitch/roll angles perfectly, with zero drift. The Pixracer so far kept drifting in attitude in the same direction as the last command was given (e.g. after a sharp left roll, Iād center the stick and expect it to stop rolling - instead it sort of stops, but then keeps rolling really slowly in the same direction, I have to give counter input to stop the roll completely. Same on the pitch axis.
AltCtl was really solid, I was almost surprised No case, Iāve covered the baro with a piece of foam. The foam is sticky-taped to the frame and the Pixracer screwed on top, compressing the foam. Only minor issue is the transition from Manual to AltCtl and back. The copter is massively overpowered with manual hover throttle at ~30% - this doesnāt concern AltCtl one bit, it maintains altitude perfectly. But during the transition I have to quickly adjust throttle, otherwise I either go into descent (when switching from Manual to AltCtl with throttle at ~30%) or into quick climb (AltCtl->Manual with 50% throttle).
1 Like
A new parameter for hover throttle (MPC_THR_HOVER) is being tested now: https://github.com/PX4/Firmware/pull/3418
It lets you put hover at center stick to solve the ALTCTL transition problem.
That PR also allows you to adjust the throttle stick deadband when in ALTCTL mode, by adding parameters MPC_ALTCTL_DZ and MPC_ALTCTL_DY.
I noticed you folks borrowed ārattitudeā from OpenPilot, shall we expect āGPS Assistā as well? https://www.youtube.com/watch?v=3D8BzaadYoI
GPS Assist + Rattitude is very powerful.
Could you explain what the concept behind GPS assist is? Iām not familiar with the OpenPilot flight modes, but weāre certainly open to respond to user requests for functionality they found interesting.
Here is the historic announcement: https://www.openpilot.org/openpilot-new-feature-gps-assist/
āOpenPilot is currently working on the next release of the OpenPilot software suite and one of the key features being developed for this upcoming release is a new flight mode named GPS Assist.
GPS Assist is a first-of-its-kind flight mode that blends Attitude or Rattitude stabilized flight modes with GPS Position Hold, with or without auto throttle.
GPS Assist is the first GPS mode available on any platform that can flip, roll and fly acro all while using GPS to recover and hold position. This new flight mode also allows you to choose auto or manual throttle for even more control in acro flight.
GPS Assist is not just for new flyers, as it can be configured with a wide range of settings, from slow and easy flight characteristics to 600deg per second flips with Rattitude, all while having a GPS to fall back on for easy recovery and position hold.ā
So essentially Horizon/Rattitude with not just autolevel, but GPS position hold + altitude hold assist with the stick released. Interesting concept for sureā¦ however I feel that getting Acro working properly is slightly more important if the Pixracer is to gain any traction in the racing scene.
1 Like
Yes olex, that is more than necessary. Without a very stable ACRO the pixracer isnĀ“t usefull for itĀ“s main purpose. Beeing the next RACING FC.
So, dear development team, please focus on this first. See my other post.
Just as update: Its the sort of initial feedback we expected, given this is the first step into that area. We found a couple of things weād like to improve and will get back to you when its ready for another testing round.
olex and schlumpfteam,
Try setting parameter ATT_BIAS_MAX to 0.0, and increasing your roll and pitch rate P gains. I was able to double mine from 0.05 to 0.1, but the optimal value depends on your particular machine.
Do you have your own procedure for PID tuning?
Hi, did you solve your issue with the WiFi connection? I too made some change (I changed Channel from 11 to 4) and since then I am unable to connect via WiFi. If you solved your issue, please let me know how you did it.
Thanks
Not yet. Iām probably going to have to reflash the firmware. It seems like changing any of the wifi params with QGC makes it unusable.
Sorry to hear that. I did let our developers know and weāll provide a factory reset button in QGC. Bear with us, the racing effort is all carried by volunteers committed to offer a great user experience, but it will take a short amount of time to get everything right.
1 Like