https://github.com/ethanlipson/PyLX-16A/blob/master/documentation.md

ros2_lx16a_driver

A ROS 2 package designed to interface with the LX-16A servo motors. This package enables control and monitoring of servo motors through ROS 2 services and topics.

Table of Contents

1. Features
2. Tested Configuration
3. Package Structure
   • Key Components
4. Installation and Usage
   • Prerequisites
   • Installation
   • Running the Node
5. Interfaces
   • Topics
   • Services
   • Parameters
6. LX-16A specifications
7. License
8. Acknowledgments

Features

• Servo parameter configuration (e.g., angle limits, voltage limits, temperature limits).
• Torque enable/disable functionality.
• Position and velocity control.
• Retrieval of servo status and diagnostic information.
• Dynamic discovery of connected servos.

Tested Configuration

• ROS 2 Distribution: Humble
• Operating System: Ubuntu 22.04
• Hardware Interface: USB connection via BusLinker-V2.5

Package Structure

ros2_lx16a_driver
├── assets
│   ├── LX-16A_servo_motor_specifications.png
│   └── lx16a_spec.py
├── CMakeLists.txt
├── package.xml
├── params
│   └── lx16a_params.yaml
├── README.md
├── src
│   ├── __init__.py
│   └── lx16a_node.py
└── srv
    ├── GetLX16AInfo.srv
    ├── SetLX16AParams.srv
    └── SetLX16ATorque.srv

Key Components

1. lx16a_node.py:

   • Implements the main ROS 2 node (lx16a_controller) for managing LX-16A servos.

2. Service Definitions:

   • GetLX16AInfo.srv: Retrieves detailed information about a specific servo.
   • SetLX16AParams.srv: Configures servo parameters.
   • SetLX16ATorque.srv: Enables or disables torque for a servo.

3. Parameter File:

   • lx16a_params.yaml: Defines default parameters such as angle limits, voltage limits, and communication settings.

Installation and Usage

Prerequisites

• ROS 2 Humble installed on Ubuntu 22.04.
• Python 3.x with pylx16a library.

Installation

1. Clone the repository into your ROS 2 workspace:

   cd ~/ros2_ws/src
   git clone <repository-url> ros2_lx16a_driver

2. Install dependencies:

   pip install pylx16a

3. Build the package:

   cd ~/ros2_ws
   colcon build --packages-select ros2_lx16a_driver

4. Source the workspace:

   source install/setup.bash

Running the Node

1. Connect the LX-16A servo motors to your computer via the BusLinker-V2.5.

2. Launch the node:

   ros2 run ros2_lx16a_driver lx16a_node

3. Optionally, provide a parameter file:

   ros2 run ros2_lx16a_driver lx16a_node --ros-args --params-file params/lx16a_params.yaml

Interfaces

Topics

• /cmd_pose_lx16a (std_msgs/Float32MultiArray): Command positions for the servos. (Each command index in the array matches the id of the commanded motor)
• /cmd_vel_lx16a (std_msgs/Int32MultiArray): Command velocities for the servos. (Each command index in the array matches the id of the commanded motor)

Services

• /lx16a_get_info (GetLX16AInfo): Retrieve detailed servo information.
• /lx16a_set_params (SetLX16AParams): Configure servo parameters.
• /lx16a_set_torque (SetLX16ATorque): Enable or disable torque for a servo.

Parameters

• default_angle_offset (int): Default angle offset for servos (degrees).
• default_angle_min (int): Minimum angle limit (degrees).
• default_angle_max (int): Maximum angle limit (degrees).
• default_voltage_min (int): Minimum voltage limit (millivolts).
• default_voltage_max (int): Maximum voltage limit (millivolts).
• default_temperature_limit (int): Maximum temperature limit (Celsius).
• log_level (int): Logging verbosity level.
• port (str): Serial port for the LX-16A bus.
• scan_connected_servos (bool): Automatically scan for connected servos.

LX-16A specifications:

The servomotor characterization can be found in the assets folder.

The rotational speed curve as a function of voltage was derived by measuring the motor shaft speed in motor mode, under no-load conditions, with a 100% speed command, using a tachometer for precise measurement.

License

This package is released under the BSD 3-Clause License.

Acknowledgments

This package leverages the pylx16a library.