Mechanical vibration at certain frequencies may result in abnormal EIS performance of DJI O3 Air Unit. The principles are as follows:
I. IMU Resonance
The usual ESC PWM control frequency is 24 kHz by default, and the camera IMU frequency is approximately 24-30 kHz. If there is no effective vibration absorbing measure, the motor vibration may be transmitted to the camera IMU, causing resonance because the frequencies coincide. The resonance will affect the IMU data accuracy and EIS performance of the video stabilization application.* As a result, the processed video image shakes, but the live view image is not affected. Usually, frames with TPU or vibration-absorbing rubber are not prone to IMU resonance.
* Video stabilization application refers to either the DJI O3 Air Unit EIS function or third-party video stabilization software.
II. Propeller Vibration
If the rolling shutter effect appears in both the live view and the video image, it is usually because the propeller vibration (frequency is approximately a few hundred Hz) is transmitted to the camera through the aircraft frame.
Follow the steps below to troubleshoot and fix the image stabilization issue:
Step 1: Rule out the IMU resonance issue.
1. Remove the propellers from the aircraft. Make sure that the camera is securely mounted and the aircraft is placed in a stationary position on the ground. Then, enable RockSteady and start recording.
2. Start the motors and slowly push the throttle to the full throttle position. Observe the live view in the goggles. If the live view is not shaking, stop the motors and stop recording. Otherwise, check the camera and make sure that it is securely mounted.
3. Export the recorded video and check it. If the video image shakes, the issue is most likely caused by the resonance between the frame and the camera IMU.
In this case, refer to the following solutions:
a. Change the ESC PWM control frequency to 48 kHz or 96 kHz and test again.
b. If the video image shakes after solution a is adopted, apply a softer vibration-absorbing structure between the camera and the aircraft frame. Repeat the above testing procedures until the video image does not shake.
Step 2: After ruling out the IMU resonance issue, check if the video image has the rolling shutter effect caused by propeller vibration.
1. Install the propellers back and make sure that the propellers are not damaged. Fly the aircraft and start recording with RockSteady enabled.
2. Check the video image after the flight. If the video image does not have a rolling effect, the debugging is completed.
3. If the video image has a rolling shutter effect, try the following solutions:
a. Adjust the vibration-absorbing structure between the camera and the aircraft frame again.
b. Adjust the tightness of the screws that fasten the camera to the aircraft frame.
If the issue still exists after all of the above methods are completed, contact DJI Support.