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Tutorial: Adding a New Type of Robot to Quad SDK

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thomas_lee6710 edited this page Jul 10, 2024 · 20 revisions

Users can add a new robot to Quad-SDK by adding a number of files describing their robot. Unitree A1 and Ghost Spirit 40 are currently supported and can be used as examples when adding a new robot.

1. Create Robot Description Files

In the /quad_simulator package, modify the following:

  • Add a /quad_simulator/<robot_name>_description folder which contains sdf and urdf to be loaded by Gazebo and RBDL. To enable the quadruped to work with the existing codes, the name of joints and links should be in the order of:
    • body
      • 8 → hip0 → 0 → upper0 → 1 → lower0 → jtoe0 → toe0
      • 9 → hip1 → 2 → upper1 → 3 → lower1 → jtoe1 → toe1
      • 10 → hip2 → 4 → upper2 → 5 → lower2 → jtoe2 → toe2
      • 11 → hip3 → 6 → upper3 → 7 → lower3 → jtoe3 → toe3

where 0-11 are actuator joints and jtoe<0-3> are fixed joints. All the rest are links. The legs are in the sequence of: front left, rear left, front right and rear right. The names of collision plugin for toes have to be toe<0-3>_collision.

We recommend to change xacro files and generate the sdf and urdf through

rosrun xacro xacro --inorder -o urdf/<robot_name>.urdf xacro/robot.xacro DEBUG:=false
gz sdf -p urdf/<robot_name>.urdf > sdf_mesh/<robot_name>.sdf

In the /quad_utils package, modify the following:

  • Add a /quad_utils/config/<robot_name>.yaml file based on the robot's actual parameters

2. Modify Launch Files

In the /quad_utils/launch package, modify the following:

  • Add case to use robot_name_description files in load_robot_params.launch and load_global_params.launch 
    <group if="$(eval arg('robot_type') == '<robot_name>')">
        <rosparam command="load" file="$(find quad_utils)/config/<robot_name>.yaml" />
        <param name="robot_description_sdf" textfile="$(find <robot_name>_description)/sdf_mesh/<robot_name>.sdf" />
        <param name="robot_description" command="cat $(find <robot_name>_description)/urdf/<robot_name>.urdf" />
    </group>

Most launch files default to robot_type:=spirit. When calling any launch file with robot_type as an argument, change it to: robot_type:=<robot_name>

Successful completion of steps 1 and 2 can be tested by launching the simulator

roslaunch quad_utils quad_gazebo.launch robot_type:="<robot_name>"`

Robot should drop into environment in sitting position.

3. Generate NMPC Controller Files

  • Install Matlab
  • Download files from quad-sdk/nmpc_controller/scripts/
    • Change parameter.name on line 36 in main.m to your <robot_name>
  • Run matlab scripts to generate custom NMPC files

4. Implement Custom NMPC Controller Files

  • Upload generated .cpp files to /nmpc_controller/src/gen/
    • eval_g_<robot_name>.cpp
    • eval_hess_g_<robot_name>.cpp
    • eval_jack_g_<robot_name>.cpp
  • Upload generated .h files to /nmpc_controller/include/nnmpc_controller/gen/
    • eval_g_<robot_name>.h
    • eval_hess_g_<robot_name>.h
    • eval_jack_g_<robot_name>.h
  • Add references to newly generated nmpc files
    • Add to add_library(…) list in /nmpc_controller/CMakeLists.txt
    • Add include statements in /nmpc_controller/include/nmpc_controller/quad_nlp.h
  • In /nmpc_controller/include/nmpc_controller/quad_nlp.h
    • add ROBOT_NAME to enum SystemID { }
    • modify static const int num_sys_id_ to match number of elements in enum SystemID { }
  • In /nmpc_controller/src/nmpc_controller.cpp
    • Add case to switch (robot_id_) with robot_ns_ string and default_system SystemID
    • Ensure case number matches order in enum SystemID { } list from quad_nlp.h
  • In /nmpc_controller/src/quad_nlp.cpp
    • load basic leg controller functions for the Robot_NAME platform

5. Update Local Planner

local_planner/src/local_planner.cpp

  • Add case for robot_name_ == “robot_name” to set type = ROBOT_NAME

6. Robot Driver

  • Create custom hardware interface
    • Save as
      • robot_name_interface.cpp in robot_driver/src/hardware_interfaces
      • robot_name_interface.h in robot_driver/include/hardware_interfaces
  • Add call to custom hardware interface
    • hardware_interface_ = std::make_shared<RobotNameInterface>
  • Add interface files to robot_driver/CMakeLists.txt
  • Add include statements for interface files in robot_driver/include/robot_driver.h

Successful completion of steps 1-6 can be tested by launching the simulator and standing the robot

# Launch simulator
roslaunch quad_utils quad_gazebo.launch robot_type:="<robot_name>"

# Stand robot
rostopic pub /robot_1/control/mode std_msgs/UInt8 "data: 1"

# Walk with global planner
roslaunch quad_utils quad_plan.launch robot_type:="<robot_name>"

7. Tune Parameters

If the robot model is not working correctly in simulation, tune the robot's parameters in /quad_utils/config/<robot_name>.yaml and the desired_height parameter in /local_planner/local_planner.yaml

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