I have a F450 quad with APM 2.6 AC3.2. Recently I'm getting BAD DCM Heading error and the copter goes into LAND mode. This is happening very frequently. I have mounted my GPS Compass on a mast. I didn't face this problem earlier. Compassmot showed mag interference of 3%. So what is causing this? Pls help me in identifying problem.
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As I mentioned, I got a new compass and the problem persists. Raising the GPS+DC unit to about 10 cm has not helped either. The dataflash log auto-analysis is showing 3%-9% interference. The same auto-analysis is showing Test: IMU Mismatch = NA for all logs. I haven't been able to search this on forums satisfactorily.
Last night I was experimenting. I had the ESCs disconnected from the power module with only APM powered up. I armed the motors, simulated a takeoff, switching between flying modes and towards then end physically lifted ( not too harsh ) the quad and bang - DCM Bad Heading popped on HUD!! So no mag/compass interference as motors were disconnected. ErrYaw spiked, AccX, AccY, Acc Z also spiked.
APM is tied secure to the frame via zip ties. I will put it on foam and see if it makes a difference. Other I am thinking of borrowing an APM and redoing entire calibration before downgrading current APM to 3.1.5 as I lose SONAR support ( at least the RNGFND_ parameters disappear ) to check.
Log attached.
2015-04-27 00-02-31 1.bin.log
This is getting even more frustrating. I changed my APM board ( but again 2.6 ). Reflashed it to AC 3.2.1, Reset the board and did a full set up - all 9 yards including compass calibration and compassmot. So now I have a new APM, new GPS+DCM, height raised etc etc. The board is mounted on an anti-vibration caddy with four gel pegs at the corners.
I flew and no I still get a DCM bad heading - EKF error. In fact the AltHold is not as great as the previous board.
I even got a DCM Bad heading on the previous board while lifting the copter by hand to simulate a slow take off and ESCs pluged off i.e. motors not running. So mag interference is out of the question. I thought bad accels / gyros but new board too is not helping. Just cannot fly in any other mode than stabilize. Copter runs off in Land, Loiter, PosHold ( I have a loose tether to prevent accidents and flyaways ).
Logs attached. Just don't know what else to do...
2015-05-03 11-50-01.log
I'm not convinced lifting the copter is a valid test, but I don't know for sure.
However, in this latest log you have vibration problems - look at IMU->GyrY. It's going up to 10 at times. It needs to be generally less than 3. On my pixhawk the vibs are down at 1 or so, spiking to 2. Have a look at other things than the APM mounting - are the motors pointing up, are they running smoothly etc, etc.
One other thing I notice is that the copter looks underpowered. Look at RCOUT 1-4 - there is clipping in the output as it goes to maximum. I'm not sure this would cause your issues, but it might be contributing.
Did you try 3.1.5
@Andy - to your post on AccY ( not GyrY ), let me check why I am getting this despite mounting on a anti-vibration ( Anti-vibration Shock Absorber ). Thx
Sorry my my bad - IMU->AccY, NOT IMU->GyrY
By lifting the copter the mag interference is ruled out I think.
IMU->GrY seems to be ranging between +1 and -1. It does hit +2 just before line 25 and -4 just before 35. That is when the quad hits the ground - bouncy landing. Unless I am reading this wrong.
Motors are all good and are mounted on a flat base..
The copter is underpowered; agree. I am running a 0845 props on EMAX MT 2213 920 kV running of 4S 5000 mAH battery. But will it be the cause for BAD DCM Heading?
I have a limit on prop size as the frame is a self designed 3D printed 315 mm motor-to-motor.
I think I will reflash and try AC 3.1.5. The primary reason for 3.2.1 was SONAR and between the devil and the deep sea, I will give up Sonar for normal flying.
Will report what happens.
Likely culprit is the compass (bad compass, loose wire, poor calibration). But you should post a log.
Thx - Let me re-calibrate compass and redo the connectors/check wiring. In the meanwhile, I am attaching the logs.
2015-04-19 14-48-10.log
2015-04-19 14-48-10.bin
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