Greetings to all the experienced community members, I need some insight on what is happening with my quad.
Recently, I had done autotune with the recommended parameter as per tuning page in wiki.
The autotune was completed and I got pretty close PID in roll and pitch but for Yaw it was a lot different.
Today, when I was flying the drone, it was oscillating with small amplitude but freq were a lot observable. I would request you all to please take a look and my logs and suggest changes that can make things better for my drone
Mine is a T-motor m1000 drone. Weight 5kg, 24 inch prop (MN7005-15 anti-gravity motor).
I have some questions too.
After trying everything that could be fixed structurally the vibe is going as high as 28 sometimes when the drone stops from 7m/s. Please suggest what should i try more
The drone looses altitude (about 2m) when a high speed(7m/s) movement is done
When I arm the drone in stabilize mode, if there is even one degree tilt the motor which is up doesnt start rotating till I go over 30 percent throttle. Any remedy that i can make take-off less scary.
Can the slots at the centre plate contribute to the Vibe?
There were a lot of ‘Primary GPS changed’ messages in the latest flight after autotune, what can be reason for it to happen. And I am never able to achieve a good HDOP .
High HDOP means you have something interfering with the GPS on your drone (probably). Fix that and you fix your GPS changed messages.
Set MOT_SPIN_ARM higher. Follow the Arducopter wiki to do this.
I think you have an underpowered drone IMO. Edit: the motors seem powerful enough but I don’t know anything of your ESCs, batteries, wire gauge etc so these could be limiting current to the motors.
You need to balance your props and make sure there are rubber feet to isolate the autopilot. Also do dynamic notch tuning as per the Arducopter wiki.
Basically you need to do a bit more reading of the Arducopter wiki!
Edit: the forum has messed up my numbering in response to your numbers but I wrote 5, 3, 2, 1.
Thanks Ardent for your valuable feedback, but would like to put some comments on your suggestions
5. Reg GPS I had isolated every component of the on the quad and had tested. I never got hdop less than 1.2 using CAN port. Once had tested it with serial port and had got it 0.6 but dual GPS configuration wasn’t working due to some reason. Had read about hdop and it was said that it’s not a good way to measure GPS lock, rather GPS status and ekf gives better idea. Please suggest me more on this and correct me if possible.
3. I had change MOT_SPIN_ARM to a higher value today… And it solved the problem (thanks)
2. Reg. The drone being underpowered (as pointed out by you) may I know the reason based on which you are saying this. I am actually curious about it. Can there not be a parameter problem that is causing this. The power system has been supplied by tmotor and I haven’t changed anything in it. If at all there is a problem with power delivery not being sufficient, how can I go about detecting the problem.
My FC pad is placed on a soft rubber washer (blue colored in the picture) and there is a 6mm 3M tape between that cf pad and fc. I have already implemented throttle based Notch filtering (you can check that in logs too). I can assure you that the props are perfectly balanced.
Don’t worry about the number. Thanks for giving your time and effort for helping me out. Certainly I will re-read the wiki… But I think I need more advice from experts like you.
Hi @sanjay_pandit ,
About the Gps problem, I suggest you try to change with a new one , just to make sure what the problem is … In the past I also had Gps problem, eventhought it is expensive GPS like Here3… I think your T motor is very powerful, what KV number is that motor? I assume you use 6S battery …
Hi Tony, I have 5 GPS Here2 units and have tested all with no luck. Never got hdop less than 1.18.
The motors are t motors MN7005 230KV with 24 inch prop and the battery is 30Ah 6s li-ion with 5C rating.
Thanks for your suggestion, will try some more Here2 GPS unit from stock.
Vibrations at sudden stop from high speed always cause a spike in vibes. Since its only 28 - I think it is fine and there isn’t much you need to do to fix this.
This is most likely due to the barometer pressure getting confused due to airflow over the autopilot. Are you flying the aircraft with the pixhawk fully exposed - or is there a cover? I have checked the logs and the aircraft hovers at around 1500PWM. This means that the propulsion system is adequately sized - you have enough thrust overhead.
Like the previous user stated - just adjust MOT_SPIN_ARM and MOT_SPIN_MIN. Make sure MOT_SPIN_MIN is at least 3% higher than MOT_SPIN_ARM.
Depends on how the aircraft is designed. I don’t think vibrations are a big issue - they are actually quite low for this size of aircraft.
It is probably switching between both GPS modules if they are so close to each other. This shouldn’t be a big issue. I don’t know the reasoning for low HDOP. Maybe just the area?
Hi @sanjay_pandit
I strongly recommend you try Cuav Neo3 pro (Can bus) GPS or Neo3 (Not Can bus)… I just share my experience , not to promote their product… I don’t have any relationship with them. But I admit their Gps is excellent with RM3100 industrial grade Compass.
Thanks, Manav, for your valuable observations and comments. This shall certainly make me confident to carry out work. Acting on your suggestion, I have made some changes
I have printed a canopy cover for FC and will test it very soon.
Have made MOT_SPIN_ARM and MOT_SPIN_MIN and that problem has gone away. Even when there is slight disorientated take-off ground, all four props rotate as soon as I arm the quad.
Actually, I was advised to keep the vibe in Z-axis to be under 15 by an expert who is flying with Ardupilot for the last four years. As per him, I can lose aircraft if it’s over 20, that’s why am worried a lot. I have tried to reduce all the vibe sources that can cause problems. The only thing I haven’t used is the canopy provided by t-motor. I will use it when fully done with tuning and when I am confident to give it a mission and take a cup of tea while it flies
I am also not able to get any reason why that would be happening, but this is certainly not coz of the area I am in. (Observation: When I had once connected the gps with serial bus, I had got hdop of around 0.6, but there was some problem with the compass associated and I wanted two GPS as redundency so had put in CAN bus. Since then, I have never seen hdop less than 1.18. I had also once reverted to serial bus once just to verify and repeat that, but the mission planner never got hdop less than 1.3)
I would certainly work to make it better. Thanks for support
Hi @ton999 ,
I will certainly try to get hold of one of that Neo3 Pro gps. You don’t need to have any relationship with anyone/anything to appreciate and suggest something which is worth commendation.
I am excited and will get it very soon.
Thanks for the suggestion.
Hi @viperhawk ,
Are you sure? that will be a very small value and will be like assuming the thrust curve is linear. It does make sense in the case of Tmotor. I am not sure of the ESC type. It came integrated with the motor and is placed right below the motor.
I understand this but peaks of 20 that last less than one second is different than constant vibrations over 20 the entire flight. The latter might cause some issues. Instantaneous peaks when coming to a quick stop should be fine.
Thanks Yasin for your comments and suggestions.
I don’t have a thrust measurement setup and it will take time to either build or buy one. What will be your suggestion for mot_thrst_expo that I should try and how to verify whether that is the required value… I mean can I change from 0.6 to 0.2 with 0.1 gap and then find a good point and then narrow it down to something that fits my quad best. Is this feasible? And how would I have that I have got what I wanted
