High Level Control for Go1

Overview

This page describes how we control Go1 with high level control mode using unitree_ros_to_real package.
You need to install necessary packages and setup your environment beforehand. (Reference)
Here is contents of this page.

• How to send command
• Commands for high level control
  • Available parameters for each mode

Environment

• Ubuntu 18.04
• unitree_legged_sdk v3.5.1 (v3.8.0)
• unitree_ros_to_real v3.5.0
• unitree_ros (version is not specified. installed on June 29, 2022)

How to send command

The image below illustrates how to send a command to Go1 using the example codes in unitree_ros_to_real, which are ros_udp.cpp and example_walk.cpp.

• You can send a command by running the ROS nodes with the following commands as described in the official document:
  In a terminal window, execute

  roslaunch unitree_legged_real real.launch ctrl_level:=highlevel
  

  This runs ros_udp with the high level control mode.
  Then, execute

  rosrun unitree_legged_real example_walk
  

  in another terminal window to run example_walk.

• In example_walk.cpp, parameters for the high level control are set to a ROS message, which is defined as HighCmd in unitree_legged_msgs package.

• It is sent to a subscriber in ros_udp.

• Then, it is converted into a command formatted for unitree_legged_sdk using rosMsg2Cmd function defined in convert.h.

• Finally, the command is sent to Go1 via UDP.

Picture of Go1

Commands for high level control

All of the commands for the high level control are listed below, which are defined in unitree_legged_sdk/include/unitree_legged_sdk/comm.h.

• std::array<uint8_t, 2> head

  • Not understood yet
  • The following parameters are set in example_walk.cpp.
  unitree_ros_to_real/unitree_legged_real/src/exe/example_walk.cpp

     high_cmd_ros.head[0] = 0xFE;
     high_cmd_ros.head[1] = 0xEF;
  

• uint8_t levelFlag

  • Flag to switch low/high level control.
  • Its entry can be HIGHLEVEL or LOWLEVEL.
  • Here, we assume it is always set to be HIGHLEVEL to use high level control.
  • default:

• uint8_t frameReserve

  • Not understood yet
  • default:

• std::array<uint32_t, 2> SN

  • Not understood yet
  • default: 0

• std::array<uint32_t, 2> version

  • Not understood yet
  • default: 0

• uint16_t bandWidth

  • Not understood yet
  • default: 0

• uint8_t mode

  • Control mode. See the sub-section for detailed explanations.
  • default:

• uint8_t gaitType

  • How to walk.
    • 0: idle
    • 1: trot
    • 2: trot running
    • 3: climb stair
    • 4: trot obstacle
  • default:

• uint8_t speedLevel

  • Walking speed. Available only if MODE = 3.
    • 0: default low speed
    • 1: medium speed
    • 2: high speed
  • default:

• float footRaiseHeight

  • Foot height in meter when it is raised up.
  • default: 0

• float bodyHeight

  • Body height in meter.
  • default: 0

• std::array<float, 2> position

  • Position in meter to move on from the current position. Available only if MODE = 3.
  • default: {0, 0}

• std::array<float, 3> euler

  • Rotation angle of the pose in radian.
  • {yaw, pitch, roll}
  • default: {0, 0, 0}

• std::array<float, 2> velocity

  • Speed to move on in meter per second ranging from -1 to +1.
  • {forward-backward, rightward-leftward}
  • default: {0, 0}

• float yawSpeed

  • Yaw rotation speed in radian per second.
  • default: 0

• BmsCmd bms

  • Holder of a BmsCmd object including uint8_t off and std::array<uint8_t, 3> reserve.
  • default:

• std::array<LED, 4> led

  • LED settings.
  • default: {}

• std::array<uint8_t, 40> wirelessRemote

  • Used to store joystick controller commands.
  • Nothing happened when I tried to control the dog by setting some values equivalent to joystick controller commands though the same parameter in HighState was changed when buttons of the joystick controller were pushed.
  • Used in unitree_legged_sdk/examples/example_wirelessHandle.cpp.
  • default: {}

• uint32_t reserve

  • Not understood yet.
  • default: 0

• uint32_t crc

  • Not understood yet.
  • default: 0

Available parameters for each mode

In this section, the modes are explained in detail and available parameters for each mode are listed.

Mode = 0

Idle, default stand.

Mode = 1

Force stand.

• bodyHeight: height of the body while standing.
• euler: pose of the body while standing.

Mode = 2

Walk at specified velocity. The dog continues to walk until it is told to stop, i.e. mode = 0, for example.

• gaitType: gait type while walking. Need to be 1-4.
• bodyHeight: height of the body while walking.
• footRaiseHeight: height of the foot. Only for gaitType = 1, 2 or 4.
• velocity: forward and rightward velocity while walking.
• yawSpeed: speed of yaw rotation while walking.

Mode = 3

Walk toward specified position. Firstly, the dog rotates euler[0] radian, and then moves toward the target position.
The dog may not walk correctly since unitree says this mode is not ready.

• gaitType: gait type while walking. Need to be 2.
• speedLevel: speed while walking. 0-2 for low to high.
• position: forward and rightward target position.
• euler[0]: yaw rotation angle.

Mode = 4

Path mode walking. This is not implemented yet.

Mode = 5

Stand down at the current position.

Mode = 6

Stand up at the current position, which is equivalent to L + A.
Sometimes the dog doesn't walk as told possibly due to a failure to change its posture. In such a case, it is useful to correct its posture with this mode.

Mode = 7

Damping at the current position, which is equivalent to L + B. This mode is suitable for software emergency. The dog refuses any commands from UDP as well as the joystick controller unless its mode is turned to mode = 6.

Mode = 8

Recovery stand at the current position.

Mode = 9

Back flip.

Mode = 10

Yaw 90 degree rotation with a jump.

Mode = 11

Put upward its hands like praying.

Mode = 12, 13

Dance.