the relative velocity and absolute velocity

[saruca1784]

hello，I wanna figure out which node converts
relative velocity from sensors to absolute velocity since the control & planning modules use the absolute velocity , please give me some hints. Do lidar & radar pipeline both have this process?
I find the convert process in radar_tracks_msgs_converter node, below the lines,

 compensated_velocity.x += odometry_data_->twist.twist.linear.x;

    compensated_velocity.y += odometry_data_->twist.twist.linear.y;
    compensated_velocity.z += odometry_data_->twist.twist.linear.z;

However, there is no value about odometry_data_->twist.twist.linear.y(I checked the /localization/kinematic_state insimulation ,and there is no radar data in official sample-rosbag), I wonder whether the velocity of y axis is compensated?
Thanks~ @youtalk

[scepter914]

Hello,
The value of odometry_data_->twist.twist.linear.y means the lateral slip.
So I think it is about 0 if the speed of the vehicle is not fast.
I don't know what you do, but it cannot be used to usual cases.

[saruca1784]

thanks a lot，actually I found out that only sqrt
of x and y axis' velocity are used and this value is assigned to twist.linear.x in the node radar_tracks_msgs_converter.
However in the node decorative_tracking_merger:
function:
autoware_perception_msgs::msg::TrackedObjectKinematics objectKinematicsVXMerger, sub_obj_.kinematics.twist_with_covariance.twist.linear.y . velocity of y axis is used, but actually it's zero as the sqrted veolcity only assigned to twist.linear.x in node radar_tracks_msgs_converter.
that's very weird and hard to figure out how this is designed.

[scepter914]

The detail design depends on each developer for each package because what to do in each package is different.
So if you think there are bug in a package, would you ask the question of it nad report it by issue on autoware.universe?

[saruca1784]

yes, i will put an issue soon