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Overview

A simple example project that demonstrates how to create a custom driver using the actuator_array_driver base class. This example uses a simulated servo motor to demonstrate the driver operation while avoiding hardware dependencies.

For details on how to create your own Actuator Array Driver, see the tutorials page.

ROS Nodes

example1_driver

This is a very simple example demonstrating the use of the Actuator Array Driver base class. This example makes use of convinience classes provided in the base class to read a simple list of actuators from the parameter server and set up the standard Actuator Array Driver communication interface. This example does not make use of the robot description. Instead, the init_actuator_ function manually fills in some of the useful properties for each actuator. A Dummy Actuator class is used to simulate the operation of a real R/C Servo motor. This removes the need to have specific hardware to test the basic Actuator Array Driver system.

Subscribed Topics

command (sensor_msgs/JointState)

  • A message containing the desired position of one or more joints controlled by this driver.

Published Topics

joint_states (sensor_msgs/JointState)

  • The current state of each joint controlled by this driver.

Services

stop (std_srvs/Empty)

  • Instruct the driver to stop all actuators immediately.

home (std_srvs/Empty)

  • Instruct each actuator to return to its home position.

Parameters

robot_description_parameter (string, default: robot_description)

  • The example1_driver node does not use any urdf information, so this parameter should be set to an empty string.

joints (string)

  • An array of joint names to be controlled by this driver.

Configuration Files

cfg/Example1Joints.yaml

  • An example yaml configuration file specifying a set of joints to control.

Launch Files

launch/example1.launch

  • A simple launch file that starts the example1_driver node and the actuator_array_gui for control.

example2_driver

This example extends example1_driver to use the robot description file. Because the base class was designed to use the robot description information, there are very few code changes. The only different is the custom 'init_actuator_' function now makes use of information obtained from the robot description instead of using hard-coded defaults. The only extra work really involved is in the creation of the robot description file itself.

Subscribed Topics

command (sensor_msgs/JointState)

  • A message containing the desired position of one or more joints controlled by this driver.

Published Topics

joint_states (sensor_msgs/JointState)

  • The current state of each joint controlled by this driver.

Services

stop (std_srvs/Empty)

  • Instruct the driver to stop all actuators immediately.

home (std_srvs/Empty)

  • Instruct each actuator to return to its home position.

Parameters

robot_description_parameter (string, default: robot_description)

  • This is the name of a parameter on the parameter server that holds the robot description urdf, not the robot description itself.

joints (string)

  • An array of joint names to be controlled by this driver.

Configuration Files

cfg/Example2Joints.yaml

  • An example yaml configuration file specifying a set of joints to control.

robots/robot2.urdf.xacro

  • A urdf file describing a simple, four-link robotic manipulator.

Launch Files

launch/example2.launch

example3_driver

In this example, a timer is used to trigger read events instead of the built-in spin() function. The YAML configuration file associated with Example3 provides additional properties, such as a channel number and home position for each servo. The custom 'init_actuator_' function demonstrates how to read these additional fields from the XMLRPS structure. Also, as a demonstration, the various helper functions are called directly, instead of using the all-in-one 'init()' function. Again, a Dummy Actuator class is used to simulate the operation of a real R/C Servo motor. This removes the need to have specific hardware to test the basic Actuator Array Driver system.

Subscribed Topics

command (sensor_msgs/JointState)

  • A message containing the desired position of one or more joints controlled by this driver.

Published Topics

joint_states (sensor_msgs/JointState)

  • The current state of each joint controlled by this driver.

Services

stop (std_srvs/Empty)

  • Instruct the driver to stop all actuators immediately.

home (std_srvs/Empty)

  • Instruct each actuator to return to its home position.

Parameters

robot_description_parameter (string, default: robot_description)

  • This is the name of a parameter on the parameter server that holds the robot description urdf, not the robot description itself.

joints (string)

  • An array of joint names to be controlled by this driver.

Configuration Files

cfg/Example3Joints.yaml

  • An example yaml configuration file specifying a set of joints to control. Each joint in this file contains additional information, such as a channel id and home position.

robots/robot3.urdf.xacro

  • A urdf file describing a simple, four-link robotic manipulator.

Launch Files

launch/example3.launch

Wiki: actuator_array_example (last edited 2012-02-19 22:16:03 by StephenWilliams)