bxi_rl_controller_ros2_example

Introduction

This repository contains a framework of developing controllers for BXI robots, including:

• A reinforcement learning based sample controller program;
• A Mujoco simulator based on ROS2;
• The BXI Hardware envrionment based on ROS2
  The binary ROS2 packages of ROS2 environment and mujoco can be find here:bxi_ros2_pkg
• The binary ROS2 package bxi_ros2_pkg/ directory：

1. communication：the robot communication package, including custom communication package formats.
2. description: contains the robot description files, including urdf, xml and the meshe files.
3. mujoco: Mujoco simulator based on ROS2. Controller programs a recommened to be verified in Mujoco before deploy to the robot hardware.
4. hardware: The robot hardware package. This node publishes all sensor data of the robot and receives control commands.
5. hardware_arm: The hardware control package for the upper-body-only version of the robot. This node publishes information about the robot's upper-body arms and receives control commands.

The bxi_ros2_pkg is a unified framework for both simulation and hardare:
ROS2 structure simulation:
ROS2 structure hardware:

• Control program src/ directory：：

1. src/bix_example: demo of the initialization process and basic message receiving and sending functions.
2. src/bix_example_py: a demo of learming based control policy.
3. src/bix_example_py_elf3: a demo of learming based control policy elf3.
4. remote_controller: reads the Xbox/PS input and publish the commands. Work with both the robot hardware and the simulation environment.
5. src/bix_example_py_arm: a demo of upper body control.

Usage

Descripiton Files

1. elf2-trunk:Elf2 v1，base link is trunk(torso)，elf2-trunk_dof12: only 12 leg joints are free joints. dof25: all joints are free.
2. elf2-ankle:Elf2 v2: ankles torques are increased 50Nm.
3. elf2-foot: Elf2 v3: sole changed: 1 shaping to human foot for wearing shoes. 2 symmetric soles change to asymmetric, like human feet.(deprecated)
4. elf2-footv4: Elf2 v4: sole change : sole shape change back to regular rectangle with oval ends. Asymmetric sole.
5. elf2-arm: arms only.
6. elf3_dof29 : Elf3 version with dof29

Switch between hardware and simulation environment

1. hw is short forhardware，all launch files with suffix hw are to launch real hardware. Please use them carefully.
2. The simulation environment and the robot hardware share the same control program. You only need to apply different launch files to switch between simulation and hardware. Topics for simulation code are with the simulation/ prefix, while topics for the hardware are with the hardware/ prefix. For details, please refer to the topic parameter settings in src/example.
3. The robot in the simulation environment is initialized with a virtual suspension. After startup, the suspension needs to be released. While suspension-related signals are ignored when operating on robot hardware).
4. There is a global odometer topic odm in the simulation env, while this topic is not available in hardware environment.

System Environment Setup

1. Ubuntu 22.04，with ROS2 version humble. mujoco requires libglfw3-dev.
2. Copy ./script/bxi-dev.rules to /etc/udev/rules.d/
3. To set up remote controller auto-start, edit ./script/ros_elf_launch.service, copy to /etc/systemd/system/, and used the systemctl tool to enable the auto-start service.

Startup Process

In both simulation and hardware, the motors are in a disabled state when started, and all parameters are uncontrollable. The startup process consists of two steps:

1. Enable position control of the motors. The motors can implement position control by setting three parameters:pos kp kd. As of Elf2 hardware, when received the 1st reset command, it's joints rotate to zero position and keep it for 10 seconds.
2. Enable all control parameters. The motors can be set with pos vel tor kp kd. As of Elf2 hardware, when received the 2nd reset command, it's joints start taking control input.
   For startup examples, please refer to src/bxi_example_py.

Running a demo control program

1. Copy the ROS2 binary packagesbxi_ros2_pkg to /opt/bxi/bxi_ros2_pkg , activate it： source /opt/bxi/bxi_ros2_pkg/setup.bash . Run it as root on robot hardware.
2. In bxi_rl_controller_ros2_example directory, run bash build.sh to compile all sources in ./src director. When compilation is done，run source ./install/setup.bash to activate the environment of current packages.
3. Run whole body demos：

• ros2 launch bxi_example_py_elf3 example_launch_demo.py : start simulation + controller program(learning based)
• ros2 launch bxi_example_py_elf3 example_launch_demo_hw.py start robot hardware + control policy

Tips for control program

1. The control commands in the topic must be sent in the specified joint order. The order of joints refer to the example src/bix_example
2. Both the simulation environment and the hardware robot have an out-of-control protection. The protection is triggered if control commands are lost for more than 100ms. Once triggered, the motors will be disabled, and the system must be reinitialized before it can be used again.

Hardware Protection

In addition to communication timeout protection, the hardware node also includes torque protection, overspeed protection, and position protection.

1. There is an error counter built into the hardware node. When the error count reaches 1000, the motor will exit the enabled state.
2. The error counter logic: increases the error count by 50 if receive a motor speed overrun ; increases the error count by 100 if receive a torque overrun ; decreases the error count by 1 if receive normal motor messages, with a minimum value of 0.
3. When the position overrun protection is triggered, the error count is not increased. The overrun direction control will be disabled, the motor can only rotate in the opposite direction.
4. Please contact us to get the detailed overrun values. It is not recommended to modify them unless necessary.

Notes

Large-sized robots may pose risks. Check instructions carefully before operation!
All control programs must go through simulation before deploying on robot hardwares.
Press the stop button immediately if any abnormality occurs!