Ewellix Driver

ROS2 driver for the Ewellix TLT lifts.

Setup

Add user to dialout group to ensure the driver has permissions to access the serial device.

sudo usermod -a -G dialout UserName

Ewellix Node Usage

Run the driver:

ros2 run ewellix_driver ewellix_node

Parameters:

• port: Path to device. By default, /dev/ttyUSB0.
• baud: Baud rate, on most TLT it should be set to 38400
• timeout: Timeout in milliseconds to wait for response from SCU. By default, 1000 ms.
• joint_count: Number of actuators. By default, 2.
• conversion: Encoder ticks per meter. Varies depending on lift model. On the 500mm model, 3225 encoder ticks per meter.
• rated_effort: Rated force of lift. On the 500mm model, 2000 N.
• tolerance: Distance from commanded position to consider within bounds. By default 0.005 meters.
• frequency: Publishing loop rate. By default, 10 Hz.

Running the driver with parameters:

ros2 run ewellix_driver ewellix_node --ros-args -p port:=/dev/ttyUSB0

Moving the lift:

ros2 topic pub /command ewellix_interfaces/msg/Command "ticks: 0
meters: 0.0"

ticks range from 0 to 865.

meters range from 0.0 to max height defined by the model. If both are defined, ticks takes priority over meters.

Ewellix Hardware Interface Usage

If the generate_ros2_control_tag is enabled in the ewllix_lift macro defined in ewellix_macro.xacro, the hardware interface will be loaded by the controller manager.

Using the position_controllers/JointGroupPositionController send a position command to the lift's actuators.

Moving the lift:

ros2 topic pub /lift_position_controller/commands std_msgs/msg/Float64MultiArray "layout:
  dim: []
  data_offset: 0
data: [0.0]"

data list specifies the desired position of the lower and upper joint.

Note, the command sent is applied to both actuators. Therefore, on the TLT500, send a 0.25 command to extend the lift to 500mm.

References

1. Ewellix serial control unit (SCU) installation, operation, and maintenance manual.
2. Ewellix RS232 interface for serial control unit.
3. Ewellix TLT lifting columns