Bumpity bump! Any updates? @leonardthall, PM me your address so I can send you my frame and push this project forward. Won’t have a pixhawk, receiver, or battery.
Hi Christopher and Jacko,
I really appreciate your enthusiasm!! Maybe instead of sending me a frame we can organise to chat over skype and that way you can do some tests with your frame and we can iterate things a little faster.
I will send you both a PM.
@Jacko1, I’ve just added a SITL simulator for both SingleCopter and CoaxCopter. The simulator quickly found a couple of bugs in the SingleCopter implementation and I have pushed fixes to master.
If you are feeling brave it would be great if you could try master on your SingleCopter and see if you can get a new flight log.
In SITL it runs AUTOTUNE fine, and also does auto missions, RTL etc.
To help with testing I’ve built firmware for Pixhawk for single and coax here:
They both fly fine in the simulator, so I think there is a reasonable chance they will work on real vehicles too.
@tridge Thanks for that - much appreciated. I will load that on the frame tomorrow and get some logs uploaded.
I’ve also noticed a bug that means that MOT_SV_SPEED doesn’t work. The servos will always run at 50Hz on Pixhawk. The motor ESC will run at 400Hz by default. I’m working on a patch to fix the MOT_SV_SPEED so it works properly.
Thanks for fixing the servo output issue and finding the negative thrust issue. I have fixed the cause of the negative thrust problem now. Randy will add it with the other motor library and Attitude control libraries soon.
I am looking forward to seeing how things go now!!!
Christopher, Jacko, I am looking forward to getting your feedback again. Thanks for your patience and help!!!
Sorry for my delayed response…life getting in the way again. None the less im ready to pound some hours back into the coax frame. Im going to bench test the new firmware tomorrow after work 6pm EST and I will post the video aswell.
@Leonardthall would you be interested in preforming some tests over skype I would have no issues with doing that if yout interested?
Throttle had more control…but only on the bottom 1/4 of the range then full throttle only past 1/4 stick.
Servos still buzz loud and are very jerky and slow to react to inputs. (the almost act like there are in manual as opposed to being in stabilized.
But all around I feel more confident it putting this firmware up into the air.
@maddmackx, just had a look at your log and it looks like the rate controllers were not running. For next test, can you put it in STABILIZE mode instead of ACRO, and also change your LOG_BITMASK to 65535.
update … the rate controllers were running, RATE.ROut is non-zero. Just small compared to RATE.R due to the re-scaling of the rate controller outputs. We should fix them to be on a similar scale (get rid of the centi-degree/s reporting)
they are Hextronic HXT 900 analog servos.
As for everything else i will do it tomorrow when i get home from work…i gotta be back up in 8 hours lol. But it will get done with a video to accompany it,
Just tested single copter as well.
The throttle is better across the range of moment and servos are responding. But servos still buzz so I dare not fly incase one burns out in the air.
Video and log…
Thanks for all your help with this I can test as you wish. Realy looking forward to this flying I have a 4114 size single copter under construction now!
Woops, sorry Tridge I had my log bitmask set as per Leonard’s request. Here is a repeat of the above test with it set to 65535.
Tridge, I finally got a bit of free time to run a longer test. I’ve uploaded the logs along with a video of the test.
Theres a couple things that im noticing that is unusual for my particular setup.
Im running Tmotor 3506-25 650kv motors with 40amp opto ESC’s 2-6s on a 5200 mah 4s spinning 14x6 tmotor beech wood propos and my motors are getting alarmingly hot. Ive ran this exact setup on my tbs pro and never came close to those temps. Im not sure whats going on but the exact same motor/esc combo on copter firmware runs 40-80 degrees cooler?? (im going to try swapping out the esc’s to see if that makes any difference)
Also you will see in the video that the servos are VERY twitchy and sensitive. Also…should my motors be spooling up and down when i put in pitch or roll commands?? I was under the impression that the control surfaces should be taking care of the requested inputs and not the motors??
Logs for the test in the video.
If there is more that I can do to help the testing phase along…please dont hesitate to ask.
Thanks again Guys
@Jacko1, I think you have two issues with the servos buzzing. The buzz in the video on the left servo at the very start of the video looks like it could be RF interference from the radio. I’d suggest dropping the transmit power on the 3DR radio down to 10dBm (it defaults to 20dBm).
You could also be getting RF interference from your receiver, as that looks like a X6R which has 2.4GHz telemetry output by default, and it looks like the antennas run right next to the servo cables. Either turn off telemetry or move the antennas away from the servo cables.
The servo outputs are also saturating as soon as their is any movement. As this is the first test of singlecopter we may have the default gains way off. I’d suggest greatly lowering the P, I and D gains on roll, pitch and yaw. See if you can get it so the servos move smoothly.
I’d also suggest lowering the filter frequency for the roll and pitch rate controllers. Try 5Hz.
I certainly wouldn’t try to fly it yet. Wait till everything is moving nice and smoothly.
The saturation of the servo’s is normal at this stage. I have added some code to fix this. The force applied by the servo is proportional to the lift created by the propeller. When that lift goes to zero the servo output goes to infinity. I have limited this increase in gain to be 50% of that at hover.
That is actually looking good. I have added some code that reduces the servo twitching. I get tridge to look over it tonight and provide a binary (just trying to reduce variables).
I suspect your motors are getting hot because at low throttle when you wouldn’t normally be taking off you are getting lots of rpm changes to give the flaps the airflow they need to provide the requested force. Then when you go to high throttle you are probably pushing significantly more current than you would normally on your quad. I would suggest chucking some smaller props on for your bench test. It also looks like the thrust pulsing is being fed back through the pixhawk and causing the pulsing.
Can you set these variables:
That will settle the servo’s down a little more too.
Keep in mind that you should be doing your test near hover throttle. That is where the servo movements will be what you expect in flight. You will find they get larger as the throttle drops and get smaller at maximum throttle. This is why they are very twitchy near minimum throttle. I have limited this effect so the movement don’t get larger below half throttle but I need to check this as I am working on code that is a fair way in front of master.
Hope this helps,
Here is the single copter update with some fixes:
Jacko has tested it and it looks good so far.