How to set up a wheel odometry input?
As a heads-up, before integrating the wheel odometry into the Vision-RTK2, we suggest updating it to our latest stable release.
Overview
To increase the performance of the Vision-RTK 2, the user can input wheelspeed measurements additionally. This optional input will serve as a fourth sensor in our fusion engine, enabling higher accuracy in outages and improved stationary status detection.
The Vision-RTK2 accepts a linear velocity input for either
a single point (Rear Center) configuration,
a 4-wheel configuration or
a 2-wheel configuration
Refer to Section 5.7 of the Integration Manual for the wheel odometry integration. Here you will find the sensor configuration for our supported input protocols: UART, TCP or CAN.
Input via UART, TCP, and CANSTR
When streaming the wheelspeed information via TCP or UART, the Vision-RTK 2 expects the messages to be in our own Fixposition format. You can find more information and code examples (C++ and Python) on the FP_B-MEASUREMENT page. To input the measurements, the user needs to populate the respective field of its dimension (x, y, z).
On the other hand, CANSTR constitutes a more customizable and flexible option, e.g. regarding the message protocol selection or the bitrate setting. Users can assign a specific ID and embed customized data within the payload of either Classic CAN or CAN FD. You can also put FP_B-MEASUREMENTS information into the payload. This setup is analogous to the UART/TCP mechanism, especially when streaming wheelspeed data into the system. Moreover, CANSTR provides the capability to input and output other user-defined information. Kindly refer to the Sections 5.4.3 and 5.7.1 of the Integration Manual for more information. Lastly, more information about the Fixposition CAN frame can be found here: https://docs.fixposition.com/fd/fixposition-can-frame
Input via CAN / OBD2
Input via ROS Driver
To input the wheelspeed information to either of these methods, you must properly configure the UART or CAN ports to ensure that their respective baud rate/bitrate is sufficient to stream this information.
Lastly, if you have a ROS topic available with the wheelspeed information, you can use our ‘Fixposition Odometry Converter' node, which you can find here https://github.com/fixposition/fixposition_driver/tree/main/fixposition_odometry_converter_ros1 for ROS1 and here https://github.com/fixposition/fixposition_driver/tree/main/fixposition_odometry_converter_ros2 for ROS2 .
Currently, messages of the type ‘geometry_msgs/Twist’, ‘geometry_msgs/TwistWithCov’, and 'nav_msgs/Odometry’ are accepted.