When I placed the mid360 upside down, the localization of Fast LIO drifted away.

[66Lau]

Hi!
When I placed the mid360 upside down and modified the roll axis to 180 degrees in the Livox config file, the localization of Fast LIO drifted away. Did I miss some steps when I trying to place mid360 up side down?

[Ecstasy-EC]

What do you mean by "modified the roll axis to 180 degrees" in the config file?

[66Lau]

Sorry, for ambiguity, I mean I changed the extrinsic_parameter in MID360_config.json like the code below.

"lidar_configs" : [
    {
      "ip" : "192.168.1.12",
      "pcl_data_type" : 1,
      "pattern_mode" : 0,
      "extrinsic_parameter" : {
        "roll": 180,
        "pitch": 0.0,
        "yaw": 0.0,
        "x": 0,
        "y": 0,
        "z": 0
      }
    }
  ]

However, I found that this extrinsic_parameter can only change the pose of the pointclouds, but not IMU. As a result, the localization drifted away. When I try to use mid360 build the map in the tilted installation or inverted installation, the PCD looks very strange because it takes camera_init as the base coordinates.

So I want to modify the code to map the imu in the inclined state to the horizontal state

I may have found a way to achieve this, just use static_transform_publisher to publish the transfrom from camera_init to foot_init if the installation of mid360 is not vertical and take the foot_init as the base coordinates


But is not the routine method mentioned in navigationTutorialsRobotSetupTF that "we need a way of transforming the laser scan we've received from the "base_laser" frame to the "base_link" frame."

Is there any better way?

[Ecstasy-EC]

As we build the map in the IMU frame, I would suggest conducting a gravity alignment during the initialization step. Read the IMU to identify the gravity direction, and record a transformation matrix to translate your IMU to the gravity frame. After that, you only need to transform the point cloud via that matrix when publish the point clouds. You'll obtain the point cloud in the gravity frame by doing so.

[66Lau]

Make sense, appreciate!!