Topics and Services

This section documents all ROS topics and services provided by the DexRobot MuJoCo node.

Input Topics

joint_commands

Control joint positions directly.

  • Type: sensor_msgs/JointState

  • Fields:

    • name: List of joint names

    • position: List of target positions

  • Example:

    from sensor_msgs.msg import JointState

msg = JointState()
msg.name = ['r_f_joint1_1', 'r_f_joint1_2']
msg.position = [0.5, 0.7]

hand_pose

Control 6-DoF floating hand pose.

  • Type: geometry_msgs/Pose

  • Fields:

    • position: Position (x, y, z)

    • orientation: Quaternion (w, x, y, z)

  • Notes:

    • Must specify --hand-pose-topic to enable

    • Position is scaled by position_magnifiers

  • Example:

    from geometry_msgs.msg import Pose

msg = Pose()
msg.position.x = 0.5
msg.position.y = 0.0
msg.position.z = 1.0
msg.orientation.w = 1.0
msg.orientation.x = 0.0
msg.orientation.y = 0.0
msg.orientation.z = 0.0

Output Topics

joint_states

Current joint positions and velocities.

  • Type: sensor_msgs/JointState

  • Fields:

    • name: List of tracked joint names

    • position: Current joint positions

    • velocity: Current joint velocities

  • Update Rate: 100Hz (default)

body_poses

6-DoF poses of tracked bodies.

  • Type: geometry_msgs/PoseArray

  • Fields:

    • poses: List of poses for tracked bodies

    • header: Standard header with timestamp

  • Update Rate: 100Hz (default)

touch_sensors

Touch sensor readings from fingertips.

  • Type: std_msgs/Float32MultiArray

  • Fields:

    • data: List of force values

  • Update Rate: 100Hz (default)

  • Units: Newtons (N)

Services

save_screenshot

Save current viewer frame as image.

  • Type: std_srvs/Trigger

  • Response:

    • success: True if screenshot saved

    • message: File path or error message

  • Example:

    # ROS2
ros2 service call /save_screenshot std_srvs/srv/Trigger

# ROS1
rosservice call /save_screenshot

Message Formats

JointState Format

header:
  stamp: <time>
  frame_id: ''
name: ['joint1', 'joint2', ...]
position: [0.1, 0.2, ...]
velocity: [0.0, 0.0, ...]

Pose Format

position:
  x: 0.0
  y: 0.0
  z: 0.0
orientation:
  w: 1.0
  x: 0.0
  y: 0.0
  z: 0.0

Touch Sensor Format

data: [0.1, 0.2, 0.3, 0.4, 0.5]  # Force values for each sensor

Example Usage

Python Interface

#!/usr/bin/env python3
import rospy
from sensor_msgs.msg import JointState
from geometry_msgs.msg import PoseArray
from std_msgs.msg import Float32MultiArray
from std_srvs.srv import Trigger

class HandController:
    def __init__(self):
        # Publishers
        self.joint_pub = rospy.Publisher(
            'joint_commands',
            JointState,
            queue_size=10
        )

        # Subscribers
        rospy.Subscriber(
            'joint_states',
            JointState,
            self.joint_callback
        )
        rospy.Subscriber(
            'body_poses',
            PoseArray,
            self.pose_callback
        )
        rospy.Subscriber(
            'touch_sensors',
            Float32MultiArray,
            self.touch_callback
        )

    def joint_callback(self, msg):
        # Process joint states
        pass

    def pose_callback(self, msg):
        # Process body poses
        pass

    def touch_callback(self, msg):
        # Process touch data
        pass

    def save_screenshot(self):
        rospy.wait_for_service('save_screenshot')
        try:
            trigger = rospy.ServiceProxy(
                'save_screenshot',
                Trigger
            )
            response = trigger()
            return response.success
        except rospy.ServiceException as e:
            print(f"Service call failed: {e}")
            return False

Command Line Interface

Monitor topics:

# Joint states
ros2 topic echo /joint_states

# Body poses
ros2 topic echo /body_poses

# Touch sensors
ros2 topic echo /touch_sensors

Send commands:

# Joint command
ros2 topic pub /joint_commands sensor_msgs/msg/JointState \
    "{name: ['r_f_joint1_1'], position: [0.5]}"

# Hand pose
ros2 topic pub /hand_pose geometry_msgs/msg/Pose \
    "{position: {x: 0.5, y: 0.0, z: 1.0},
      orientation: {w: 1.0, x: 0.0, y: 0.0, z: 0.0}}"

Next Steps