IMU calibration issue with I2.

[Casey53]

My I2 was doing some hard braking and I noticed it sitting crooked and not level once it stopped. The gimbal and camera were level on the screen, but the bird was titled sideways by maybe 30 degrees in hover.

I decided to do another IMU cal and I'm not too crazy about the two parts where they have you rest the bird upright on the sides as it wobbles with me holding it and the legs are sort of flimsy in that position and some have reported them being crooked too. The sitting flat, and on the front and rear lower legs are okay and I don't have to hold onto it, but the sides aren't and I think I did the first ones resting on the legs (Which are tilted in a bit and not the motors?) and the screen's demo shows it 90 degrees upright.

So I pulled out some 3"x18" plastic ruler out of the sewing room (Used as a cutting wheel ruler.) and used it as a carpenter's square to make it 90 degrees on the side by holding it against the two legs and the level surface rather than wobble on the side. Maybe an aluminum carpenter's square would also work being non-magnetic although I don't think the compass would be influenced in IMU cal but don't know hence the plastic one.

Need to try a flight again and see if it sits level after hard braking.

 

[NickU]

Just rest it on the leg skids rather than the motors when it's on its left/right side, no need for it to be vertical.... tbh, it's better not to hold it as you will introduce errors via micro movements/vibration during the cal process. Fwiw, front/back for I2 aren't vertical, neither are the Cals for the phantoms - they're angled during the process too, so it isn't important for that part of the process.

 

[Casey53]

Just rest it on the leg skids rather than the motors when it's on its left/right side, no need for it to be vertical.... tbh, it's better not to hold it as you will introduce errors via micro movements/vibration during the cal process. Fwiw, front/back for I2 aren't vertical, neither are the Cals for the phantoms - they're angled during the process too, so it isn't important for that part of the process.

Nick, I tried resting it on the left and right side, but with the lighter X4S camera it will fall over onto its top on mine the way the legs are slanted. I have to hold it upright and then it wobbles too much for me and the "Good to proceed" signal seems slower too. I think when I had the X5S camera it would rest on the sides without me holding it, but I am short lenses due to their version updates so I'm back to using the X4S.

The IMU calibration instructions on the screen show it being 90 degrees upright and maybe on the motors and not the slanted legs for the side calibrations so I'm unsure of the resting it on its side legs part. Don't know if that is hard-coded into the IMU calibration numbers or not so I went with the plastic square to balance it upright. I've seen the guy's video of where he has some digital counter showing the numbers plus-to-minus on tilting the IMU board around which seem important to the thing getting a good level. My wobbling isn't probably any good if it ends up with a count of +4999 on one side and the other side is -4100.

When I did a high-speed stop into a hover it parked itself sideways which bothered me and some guy who was watching it said, "It doesn't look level to me either, and I hung drywall for years and can spot that being crooked." I thought it was going to land on one leg for a while until I flew it around a bit more and it leveled itself out. Hence, a re-cal of the IMU with the square.

 

[cvanhoose]

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The IMU calibration instructions on the screen show it being 90 degrees upright and maybe on the motors and not the slanted legs for the side calibrations so I'm unsure of the resting it on its side legs part.

Don’t go by the screen. My mavic calibration shows to rotate on its side when it is suppose to be nose down during compass cal.

 

[Casey53]

Don’t go by the screen. My mavic calibration shows to rotate on its side when it is suppose to be nose down during compass cal.

But that's for the Compass on the Mavic. I'm doing the IMU calibration on the I2 which does 5 sides for the IMU. I2 compass is a different calibration and some wobble might be tolerable there (Spinning and just resting on the bottom, and then on one side.). If you can find that guy doing the IMU board calibration, the numbers are critical as to the tilt.

Fwiw, the old P4 used to be with the compass flat and then on the back or front, but then they changed it to the bottom and on the side for the compass. They also changed the IMU on the P4 from 2 positions to six.

 

[NickU]

I see what you mean about the weight - just tried it without the x5s!

The main thing is that the I2 is 'quiet' and stable, i.e. not moving, rather than perfectly vertical during the calibration. So if it's resting on the motor cans and is stable, then that's fine. Equally if it's keeled over onto the leg skids, then that's fine too.... just so long as it's not moving

If you ever watch the IMU values prior to take off, you'll see it picks up the slightest of movements, even from light wind, and hides the display offset values saying that the aircraft is moving... they reappear when it thinks it's steady again.

 

[NickU]

The IMU screen displays are a bit misleading with the images they show, it caused some confusion when they first changed the cal routines when they introduced the p4p.

Best thing to do after the cal is set the aircraft down somewhere stable and watch the IMU readouts, if they stay in the green and nice n low, then the cal should be good to go. If they're constantly popping up in yellow or red territory, then best to recal again.

 

[Casey53]

As to being stable and wobble free, I ain't!

More I hold it on its side, the more it wobbles (Legs aren't really that stable, imho.). Then when I look at the iPad to see what's next and and back at it, it's slanted or wobbling even more without that ruler holding it! Like telling your kids to "Sit still!" and then they fidget even worse in the back seat.

I may go grab a 6"x24" ruler at some quilter's store I found online for $17 to get rid of my I2 IMU wobbles - and "instability" issues too!

 

[NickU]

As to being stable and wobble free, I ain't!

Happens to us all, age & beer