Positioning of A2 IMU over gimbal's pan motor???

[Bartman]

Hi folks,

I'm in the early stages of a new build and I've got my A2 IMU right in the center of the lower frame plate. In the user manual they recommend getting it as near the center as possible. But, with the GH3 Zenmuse attached, the pan motor for the gimbal is directly below the IMU. The motor is basically a collection of magnets surrounding a collection of electro-magnets and I'm guessing the strong magnetic fields produced by the motor will interfere with the IMU.

Has anyone assembled their A2 and gimbal like this? Problems?

I've noticed that the DJI S1000 and S800 have the IMU offset to the front of the frame, maybe for this reason? The reply I got from DJI was unclear so I have to follow up to get clarification but was wondering if there are any examples from the real world worth discussing.

Thanks,
Bart

 

[Benjamin Kenobi]

I've got mine only an inch away from the pan motor (just in front). I've seen pictures of guys with it on the actual pan itself.

How close will it be to the motor? Touching or a little bit of separation? I've tried to get an idea of the magnetic field by holding a screw driver near the motor and see when I feel the pull. It seems to be on the side rather than the top that it is magnetic.

Not a definitive answer I know, sorry.

 

[Carapau]

Bart the reason for getting the IMU near the center is because this is where DJI reckon that vibes tend to be a their minimum. If in doubt I would just place it away and enter the right numbers in the IMU positioning part of the assistant software. I have build loads of different machines with IMUs in all sorts of positions and as long as you get the location numbers right in the assistant software, I see no difference in performance (admittedly these builds have all been with WKM but I don't think there is a great deal of difference between the two in terms of IMU positioning).

 

[deluge2]

The manual suggests placing the A2 IMU at a 'low vibration position', going on to say that 'Based on DJI's experience, there is less vibration near the aircraft's center of gravity.' Since the IMU software configuration includes specifying its position relative the CG in terms of X, Y, and Z coordinates, one does not have to precisely follow the location advice. You mention the IMU offset in the s800. There are two locations DJI specifies, one to the rear on the center frame, the other *farther to the rear* on a separate tray mounted on the lower 'H-frame' assembly which has dampers to reduce vibrations transmitted from the arms/center frame unit. So the DJI-described mount points are not 'offset to the front of the frame'. Perhaps you're recalling the alternate s800 IMU locations that others have documented on this forum?

While the fact that you got a reply from DJI at all is in some sense 'good news' it's not a surprise that it was not clear or helpful. Perhaps the DJI reps who post here will offer some useful advice. Since there are reports of success with IMU locations fore and aft of the CG, I suggest you consider these based on your concerns regarding RF/magnetic fields. The metal case of the IMU means it's essentially in a Farady cage, so RF may not be an important issue. However magnetic fields could still be an issue, as there's no easy way to shield against them. I don't know how sensitive the IMU components (accelerometers, gyros, altimeter) are to magnetic fields.

Steve

Hi folks,

I'm in the early stages of a new build and I've got my A2 IMU right in the center of the lower frame plate. In the user manual they recommend getting it as near the center as possible. But, with the GH3 Zenmuse attached, the pan motor for the gimbal is directly below the IMU. The motor is basically a collection of magnets surrounding a collection of electro-magnets and I'm guessing the strong magnetic fields produced by the motor will interfere with the IMU.

Has anyone assembled their A2 and gimbal like this? Problems?

I've noticed that the DJI S1000 and S800 have the IMU offset to the front of the frame, maybe for this reason? The reply I got from DJI was unclear so I have to follow up to get clarification but was wondering if there are any examples from the real world worth discussing.

Thanks,
Bart

 

[soler]

The GPS puck contains a compass which be effected to magnetic fields, but the IMU has gyros and accelomerers. You coul position the IMU where you plan and then see from the assistant software if moving the gyro has any effect.

 

[fdproductions]

Bartman, I suggest leave the IMU inside the frame but place if it very carefully if using on your evo, I suggest using heavy cardstock paper. Perforate to exact dimensions of the opening in the upper deck. Anchor the IMU with dual lock on the face of the imu and mount to your phone or any other flat object this way you won't have to worry about your fingers getting in the way.

Some of the best aerial footage comes from being really close to your subject, so God forbid you graze and hit something on your retracts or hit your GH/5D/NEX and nothing else the imu will most likely be more forgiving than if the IMU is mounted anywhere other than the center of the airframe. Generally spacing your electronics out and mounting downlink systems are probably just as important as builds. hope this is helpful, i will suggest mounting your satellites for your gimbal tx to the face of the gimbal mounts, if your running JR satellites its perfect because the two red illuminated bulbs also help for orientation.