IMU data publish configuration used in Autoware

[TZECHIN6]

Currently I am having a IMU with its official ROS2 driver, it publishes Z equals to positive 1 as result in linear z. I believe this value is converted after removing gravity.

The question in here is that, for autoware default setting/requirement, what is the expected IMU input format? I have tried but failed to find a reference or document talking about this.

An example from LIO-SAM indicated the expected IMU data format before passing into the processing node.

[TaikiYamada4]

@TZECHIN6
Autoware assumes that the acceleration is given with a [m/s^2] unit, and angular velocity with [rad/s] unit.
The gravity observed with positive values seem to be correct.
However, as far as I know, the defualt Autoware (localizing with NDT scan matching) doesn't use the acceleration from IMU and use angular velocity only.

[TZECHIN6]

Thanks @TaikiYamada4. For the positive linear z value reading, should it be 9.81 or 1.0? I saw most of the IMU ros2 provider provide 9.81 by default which do not counter the gravity. Or this is not important, as autoware would only consider the change of rate?

[liuXinGangChina]

Thanks @TaikiYamada4. For the positive linear z value reading, should it be 9.81 or 1.0? I saw most of the IMU ros2 provider provide 9.81 by default which do not counter the gravity. Or this is not important, as autoware would only consider the change of rate?

actually it should be 9.81 which represent true acc value of each axis，
Yes autoware only consider gyro of z to estimate heading

[TZECHIN6]

Thanks for the update. So for my IMU which publish linear.z in 1.0, I should update the driver to remove such compensation to gravity, or autoware provide a way to handle two different types of IMU by utilizing the imu_corrector node?

[TaikiYamada4]

So for my IMU which publish linear.z in 1.0, I should update the driver to remove such compensation to gravity, or autoware provide a way to handle two different types of IMU by utilizing the imu_corrector node?

Unfortunately, Autoware doesn't have a feature to convert [G] to [m/s^2] in imu_corrector, so it has to be converted somewhere in the driver or an additional correction node.

[TZECHIN6]

Now its clear, thanks both of you <3. For a beginner like me, how can I find those documentation or related information? Cheers

[TaikiYamada4]

Requirements should be somewhere in the design page of Autoware Documentation, but I found it odd that there is no reference about the IMU. 😢
I cannot promise I will do it soon, but I will keep in mind to update the document to mention about IMU requirements.

https://autowarefoundation.github.io/autoware-documentation/main/design/autoware-architecture/sensing/