Robot and DDS Interfaces

1. Overview

The DR02 Pro SDK communicates with the robot through ROS 2 / DDS middleware, providing complete interfaces for joint control, state reading, IMU data, peripheral monitoring, and more.

Note: Before using ROS2 tools to receive topics, check frequencies, etc., you need to source the environment variables with source /opt/robot/scripts/setup_ros2.sh.

2. Core ROS 2 Topics

Topic	Message Type	Description
/JOINTS_CMD	drdds/msg/JointsCmd	Joint control command (SDK → Robot)
/JOINTS_DATA	drdds/msg/Joints	Joint state feedback (Robot → SDK)
/IMU_DATA_HEAD	sensor_msgs/msg/Imu	Head IMU data
/IMU_DATA_BASE	sensor_msgs/msg/Imu	Base IMU data
/STEER	drdds/msg/Steer	Normalized velocity command
/REAL_STEER	drdds/msg/Steer	Actual velocity command
/GAMEPAD_KEY	std_msgs/msg/String	Gamepad button events
/BATTERY_DATA	drdds/msg/BatteryData	Battery data
/MOTION_STATE	—	Motion state transition command
/MOTION_INFO	—	Motion state information
/GAIT	—	Gait switching command

3. Robot Specifications

3.1 Basic Information

Item	Value
Robot Name	DR2PRO (enumeration value 0)
Total DOF	31
Waist DOF	3 (WaistX, WaistY, WaistZ)
Single Arm DOF	7 (ShoulderY, ShoulderX, ShoulderZ, Elbow, WristZ, WristY, WristX)
Single Leg DOF	6 (HipY, HipX, HipZ, Knee, AnkleY, AnkleX)
Neck DOF	2

Joint Ordering: Waist(3) → Left Arm(7) → Right Arm(7) → Left Leg(6) → Right Leg(6) → Neck(2)

3.2 Joint Index Mapping Table

Joint configurations vary across robot models. The following table defines the joint name corresponding to each index:

Index	Region	DR02 STD Joint Name	DR02 Pro Joint Name
0	Waist	Waist Yaw	Waist Yaw
1		x	Waist Roll
2		x	Waist Pitch
3	Left Arm	Left Shoulder Pitch	Left Shoulder Pitch
4		Left Shoulder Roll	Left Shoulder Roll
5		Left Shoulder Yaw	Left Shoulder Yaw
6		Left Elbow	Left Elbow
7		x	Left Wrist Yaw
8		x	Left Wrist Pitch
9		x	Left Wrist Roll
10	Right Arm	Right Shoulder Pitch	Right Shoulder Pitch
11		Right Shoulder Roll	Right Shoulder Roll
12		Right Shoulder Yaw	Right Shoulder Yaw
13		Right Elbow	Right Elbow
14		x	Right Wrist Yaw
15		x	Right Wrist Pitch
16		x	Right Wrist Roll
17	Left Leg	Left Hip Pitch	Left Hip Pitch
18		Left Hip Roll	Left Hip Roll
19		Left Hip Yaw	Left Hip Yaw
20		Left Knee	Left Knee
21		Left Ankle Pitch	Left Ankle Pitch
22		Left Ankle Roll	Left Ankle Roll
23	Right Leg	Right Hip Pitch	Right Hip Pitch
24		Right Hip Roll	Right Hip Roll
25		Right Hip Yaw	Right Hip Yaw
26		Right Knee	Right Knee
27		Right Ankle Pitch	Right Ankle Pitch
28		Right Ankle Roll	Right Ankle Roll
29	Head	x	Head Yaw
30		x	Head Pitch

Note: In the MotorStatus parameter group, due to the different number of joints between the STD and PRO versions, the array length is fixed at 31 for consistent display on the App side. A value of 10 indicates that the joint does not exist.

4. Robot Base Class Interface

4.1 Function Description

RobotInterface is the base class for robot access, responsible for:

• Creating ROS 2 publishers/subscribers
• Providing joint state reading (position, velocity, torque, temperature)
• Providing IMU data reading (head and base dual IMU)
• Publishing joint commands

4.2 Constructor Parameters

RobotInterface(robot_name, dof_num=31, leg_dof_num=6, arm_dof_num=7, waist_dof_num=3, neck_dof_num=2, node)

4.3 Subscribed Topics

/JOINTS_CMD    → Publish joint control commands
/JOINTS_DATA   ← Subscribe to joint state feedback
/IMU_DATA_HEAD ← Subscribe to head IMU
/IMU_DATA_BASE ← Subscribe to base IMU

4.4 Joint Command Format

Each joint has 5 parameters: kp, position, kd, velocity, torque

4.5 Joint Control Formula

$T = kp \times (pos_{goal} - pos_{real}) + kd \times (vel_{goal} - vel_{real}) + t_{ff}$

4.6 DOF Parameter Setting Interface

DR2ProInterface inherits from RobotInterface and only sets the DOF parameters:

DR2ProInterface(node, "DR2PRO") : RobotInterface("DR2PRO", 31, 12, 14, 3, 2, node)

No additional offset or direction mapping is applied; raw values are used directly.

5. Usage Examples

5.1 Subscribe to Joint Data

// Subscribe to joint data
auto subscription = node->create_subscription<drdds::msg::Joints>(
    "/JOINTS_DATA", 10,
    [](const drdds::msg::Joints::SharedPtr msg) {
        // Process joint data
        for (size_t i = 0; i < msg->joint_position.size(); ++i) {
            RCLCPP_INFO(node->get_logger(), "Joint %zu: pos=%.4f vel=%.4f",
                       i, msg->joint_position[i], msg->joint_velocity[i]);
        }
    });

5.2 Publish Joint Commands

// Create joint command publisher
auto publisher = node->create_publisher<drdds::msg::JointsCmd>(
    "/JOINTS_CMD", 10);

// Construct joint command
drdds::msg::JointsCmd cmd;
for (int i = 0; i < 31; ++i) {
    cmd.kp.push_back(600);           // PD gain Kp
    cmd.position.push_back(0.0);      // Target position
    cmd.kd.push_back(6);              // PD gain Kd
    cmd.velocity.push_back(0.0);      // Target velocity
    cmd.torque.push_back(0.0);        // Feedforward torque
}

// Publish command
publisher->publish(cmd);

5.3 Subscribe to IMU Data

// Subscribe to head IMU
auto imu_sub = node->create_subscription<sensor_msgs::msg::Imu>(
    "/IMU_DATA_HEAD", 10,
    [](const sensor_msgs::msg::Imu::SharedPtr msg) {
        RCLCPP_INFO(node->get_logger(),
                   "IMU: lin_acc=[%.2f %.2f %.2f] ang_vel=[%.2f %.2f %.2f]",
                   msg->linear_acceleration.x,
                   msg->linear_acceleration.y,
                   msg->linear_acceleration.z,
                   msg->angular_velocity.x,
                   msg->angular_velocity.y,
                   msg->angular_velocity.z);
    });

6. Deployment Locations

The SDK can run at the following locations as long as the ROS 2 / DDS network is interconnected:

Location	IP	Description
Development Host	User-configured	Must be connected to the robot’s rear Ethernet port via cable
AOS Host	10.21.33.103	On-robot compute device
NOS Host	10.21.33.106	Pre-installed with message interface library