ros2_control hardware interface

For applications with strong real-time and safety requirements

The hardware interface variant is designed for applications within the ros2_control framework that require strong real-time and safety requirements. This variant always uses the reading from the buffer mechanism, timed by the ros2_control master clock.

Learn more: ros2_control official documentation

ROS2 Control Tags in URDF

To use the sensor hardware interface, the following block must be included in your URDF file:

Required Parameters:

Parameter	Description
`config_file`	Path to the JSON configuration file
`tare_on_activation`	Whether to tare the sensor on HW interface activation

URDF Configuration:

<ros2_control name="<SENSOR_LINK_NAME>" type="sensor">
   <hardware>
     <plugin>bota_driver/BotaFTSensor</plugin>
     <param name="config_file">PATH_TO_JSON</param>
     <param name="tare_on_activation">true|false</param>
   </hardware>
 </ros2_control>

Note

XACRO Integration: It is advisable to include sensor links and joints leveraging the XACRO macros provided in the bota-driver package. See the ROS2 driver documentation for more details about the XACROs included in the bota-driver package.

Available State Interfaces

Once the hardare interface is loaded by the controller_manager the following state interfaces are available:

Interface Name	Type	Description
`hardware_interface_active`	Status	Indicates if the hardware interface is active
`status.throttled`	Status	Sensor throttling status flag
`status.overrange`	Status	Sensor overrange status flag
`status.invalid`	Status	Sensor invalid data status flag
`status.raw`	Status	Raw data status flag
`status`	Status	Indicates if any of the status flags are set, acting as a general summary status flag
`force.x/y/z`	Measurement	Force measurements in X, Y, Z axes
`torque.x/y/z`	Measurement	Torque measurements in X, Y, Z axes
`lin_acc.x/y/z`	Measurement	Acceleration measurements in X, Y, Z axes
`ang_vel.x/y/z`	Measurement	Angular rate measurements in X, Y, Z axes
`temperature`	Measurement	Temperature reading in Celsius
`timestamp`	Timing	Sensor timestamp in microseconds

Taring procedure

Important

The sensor is always zeroed during activation of the hardware interface if the parameter tare_on_activation is set to true in the URDF configuration.

To perform a taring procedure, the hardware interface needs to be deactivated and then re-activated.

It is important to ensure that no controller is actively using the sensor data during this process, as the state interface data will not be updated while the hardware inteface is deactivated. The hardware_interface_active will turn false during this period, indicating that the sensor data is not being updated.

An example how to do this is shown in the example repository linked below.

Safety Guidelines

A proper use of the Bota FT sensor hardware interface requires monitoring two distinct safety aspects:

Hardware Interface Status

Due to ros2_control implementation, sensor interfaces can be exposed even when hardware is disconnected. Always check hardware_interface_active before using any sensor data. If this flag turns false, the state interfaces are not being updated with sensor data, and you must not use them in your control logic.

Sensor Status Flags

The sensor provides status flags that indicate data quality and operational conditions. Always monitor these flags in your control logic and react accordingly to ensure safe operation.

Getting Started

Bota Systems provides an example including a full ros2_control setup with a Bota FT sensor. It demonstrates how to integrate the sensor into a ROS2 control system, including the necessary configuration and usage patterns.

Found the packages implementation in our official GitLab repository.

bota_example_ros2_control on GitLab