IMU In Use Indicator

[Don Barar]

Hello All,

I just calibrated the IMUs on my Phantom 4 Pro. After calibration the IMUs accelerometer bias are 0.003 and 0.004 for IMU 1 and IMU 2 respectively--which is good.

To the left of IMU indicators there is yellow dot adjacent to IMU1. From the key below, my impression is that this means "In Use". There is no yellow dot to the left of IMU2.

The question for the group is should one, both, or neither of the yellow dots appear to the left of the IMU?

Donald Barar

 

[msinger]

An IMU contains both an accelerometer and a gyroscope. If IMU #1 is in use, accelerometer #1 and gyroscope #1 are both being used.

 

[Don Barar]

I was hopping for a little bit more information. For example, there are two IMUs. All I ever see is number 1 in use. When does IMU 2 come into play?

Donald Barar

 

[smiller]

I was hopping for a little bit more information. For example, there are two IMUs. All I ever see is number 1 in use. When does IMU 2 come into play?

Well you can bet it does if IMU 1 fails

 

[Don Barar]

Is it standby as you suggest? Is it reference? I was hoping to develop a better understanding of the logic as nothing is published.

Donald Barar

 

[msinger]

I was hoping to develop a better understanding of the logic as nothing is published.

I haven't seen anything published either. I'm not aware of the algorithm used to determine which IMU should be used. Perhaps DJI is always defaulting to #1 when it's ready to use.

 

[smiller]

Is it standby as you suggest? Is it reference? I was hoping to develop a better understanding of the logic as nothing is published.

It would be interesting to know. I'm pretty sure the only reason for dual IMUs is redundancy and not sure if IMU 1 is always used unless a problem is detected, nor do we know exactly how an IMU fault is determined. Devices such as an IMU module usually do a bunch of internal crosschecking and if all looks good supplies a 'Data OK' output indicating that it is happy and thinks it is working OK, and of course lack of this signal indicates a problem. The P4P may do some external crosschecking as well (comparing compass to IMU for example.) The exact algorithm would be interesting reading but DJI may consider it proprietary.