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Source: https://support.unitree.com/home/en/G1_developer/basic_services_interface
The low-level communication facilitates data interaction between the user PC and the robot. It uses the DDS protocol (DDS related knowledge can be found in 《DDS Communication Interface》).
- Subscribe to the topic
rt/lowstate(type:unitree_hg::msg::dds_::LowState_) to obtain the current state of the G1. - Publish to the topic
rt/lowcmd(type:unitree_hg::msg::dds_::LowCmd_) to control all body joint motors (excluding the dexterous hand), the battery, and other devices. - To use the Dex3-1 force-controlled dexterous hand, publish to the topic
rt/dex3/(left or right)/cmd(type:unitree_hg::msg::dds_::HandCmd_) to control the dexterous hand, and subscribe to the topicrt/dex3/(left or right)/state(type:unitree_hg::msg::dds_::HandState_) to receive the hand's state.
Interface Description
Subscribe to or publish topics using the methods described in the DDS communication interface. Topic data is stored in structures defined by IDL, with commonly used structures including:
| Structure Name | Description |
|---|---|
HandCmd_ |
Dex3-1 Control |
HandState_ |
Dex3-1 Status |
IMUState_ |
G1 IMU Status |
LowCmd_ |
G1 Low-level Control |
LowState_ |
G1 Low-level Status |
MotorCmd_ |
G1 Motor Control |
MotorState_ |
G1 Motor Status |
PressSensorState_ |
Dex3-1 Tactile Feedback |
Introduction to message types
Dex3-1 Control
unitree_hg::msg::dds_::HandCmd_
struct HandCmd_ {
sequence<unitree_hg::msg::dds_::MotorCmd_> motor_cmd; // Commands for all motors in the dexterous hand
};
Dex3-1 Status
unitree_hg::msg::dds_::HandState_
struct HandState_ {
sequence<unitree_hg::msg::dds_::MotorState_> motor_state; // States of all motors in the dexterous hand
unitree_hg::msg::dds_::IMUState_ imu_state; // IMU state of the dexterous hand
sequence<unitree_hg::msg::dds_::PressSensorState_> press_sensor_state; // Pressure sensor states
float power_v; // Power voltage of the dexterous hand
float power_a; // Power current of the dexterous hand
unsigned long reserve[2]; // Reserved
};
IMU Status
unitree_hg::msg::dds_::IMUState_
struct IMUState_ {
float quaternion[4]; // Quaternion QwQxQyQz
float gyroscope[3]; // Gyroscope (angular velocity) omega_xyz
float accelerometer[3]; // Acceleration acc_xyz
float rpy[3]; // Euler angles
short temperature; // IMU temperature
};
Low-level Control
unitree_hg::msg::dds_::LowCmd_
struct LowCmd_ {
octet mode_pr; // Parallel mechanism (ankle and waist) control mode (default 0) 0:PR, 1:AB
octet mode_machine; // G1 Type：4：23-Dof;5:29-Dof;6:27-Dof(29Dof Fitted at the waist)
unitree_hg::msg::dds_::MotorCmd_ motor_cmd[35]; // Control commands for all body motors
unsigned long reserve[4]; // Reserved
unsigned long crc; // Checksum
};
Low-level Status
unitree_hg::msg::dds_::LowState_
struct LowState_ {
octet mode_pr; // Parallel mechanism (ankle and waist) control mode (default 0) 0:PR, 1:AB
octet mode_machine; // G1 Type
unsigned long tick; // Timer incrementing every 1ms
unitree_hg::msg::dds_::IMUState_ imu_state; // IMU state
unitree_hg::msg::dds_::MotorState_ motor_state[35]; // States of all body motors
octet wireless_remote[40]; // Raw data from Unitree physical remote control
unsigned long reserve[4]; // Reserved
unsigned long crc; // Checksum
};
Motor Control
unitree_hg::msg::dds_::MotorCmd_
struct MotorCmd_ {
octet mode; // Motor control mode 0:Disable, 1:Enable
float q; // Target joint position
float dq; // Target joint velocity
float tau; // Feedforward torque
float kp; // Joint stiffness coefficient
float kd; // Joint damping coefficient
unsigned long reserve[3]; // Reserved
};
Motor Status
unitree_hg::msg::dds_::MotorState_
struct MotorState_ {
octet mode; // Current motor mode
float q; // Joint feedback position (rad)
float dq; // Joint feedback velocity (rad/s)
float ddq; // Joint feedback acceleration (rad/s^2)
float tau_est; // Joint feedback torque
float q_raw; // Reserved
float dq_raw; // Reserved
float ddq_raw; // Reserved
short temperature[2]; // Motor temperature (surface and winding)
unsigned long sensor[2]; // Sensor data
float vol; // Motor terminal voltage
unsigned long motorstate; // Motor state
unsigned long reserve[4]; // Reserved
};
Dex3-1 Tactile Feedback
unitree_hg::msg::dds_::PressSensorState_
struct PressSensorState_ {
float pressure[12];
float temperature[12];
};