balance_robot_algorithm

TeeterBot is a self-balancing robot simulation model for ROS / Gazebo. The dimensions and mass of each component are easily configured using launch file arguments, so it is easy to adjust physical parameters to test robustness of control algorithms.

Besides, this repo will also provide some control algorithms like LQR/MPC for self balancing robot.

Self-balancing robot simulation model for ROS / Gazebo(using LQR/MPC)

Installation

sudo apt install ros-noetic-hector-gazebo-plugins
sudo apt install xterm

#install 
sudo apt-get install libeigen3-dev

# because the program use <Eigen/Dense> directly, so we need to create a soft link to Eigen
sudo ln -s /usr/include/eigen3/Eigen /usr/include/Eigen
sudo ln -s /usr/include/eigen3/Eigen /usr/include/unsupported
sudo ln -s /usr/include/eigen3/Eigen /usr/include/signature_of_eigen3_matrix_library

cd $your_work_space/src
git clone [email protected]:66Lau/balance_robot_algorithm.git
cd ..
catkin_make

Launch Files

There are two launch files in the teeterbot_gazebo package.

teeterbot_robot.launch

This launch file spawns TeeterBot in Gazebo. The arguments of this launch file control the dimensions, mass, and behavior of the simulation:

• Name and spawn pose: These arguments set the name and initial position and heading of Teeterbot in Gazebo world frame. The start_z parameter should be equal to the wheel radius, as the origin of TeeterBot's base frame is at the focal point of its rotation.
• Physical properties: These arguments specify the dimensions and masses of the wheels and body of TeeterBot.
  • training_wheels: Set true to spawn two invisible, frictionless spheres that prevent the robot from tipping over.
• Simulation behavior settings:
  • pub_gound_truth: set true to broadcast a TF transform from Gazebo world frame to TeeterBot's base_footprint frame.
  • auto_reset_orientation: set true, and the Gazebo plugin will detect when TeeterBot falls down and automatically reset it to vertical orientation.
  • auto_reset_delay: amount of time between detecting a fallen-over Teeterbot and when the automatic reset is performed.
• Control mode: Switches the control interface to TeeterBot's motors. Set only one of these to true
  • voltage_mode: User directly controls the voltage applied to the motor
  • torque_mode: User issues a torque command to each motor, and the simulator internally regulates the motor current to achieve that torque.
  • speed_mode: User issues angular velocity commands to each motor and the simulator regulates the motor voltage inputs to achieve that command.

teeterbot_empty_world.launch

This launch file serves as an example of how to start Gazebo, include teeterbot_robot.launch, and set its arguments to configure the simulation.

Input Topics

To control TeeterBot, a separate std_msgs/Float64 topic is advertised for each wheel. The topics are advertised in the namespace of the particular robot name specified in the robot_name launch file argument. However, the names of these topics are different for each control mode:

• Voltage mode: <robot name>/left_motor_voltage and <robot name>/right_motor_voltage
• Torque mode: <robot name>/left_torque_cmd and <robot name>/right_torque_cmd
• Speed mode: <robot name>/left_speed_cmd and <robot name>/right_speed_cmd

Controller

To use different controller (lqr/lmpc/nmpc), you need to change the controller node in teeterbot_controller.launch.

• LQR
  Using matlab to get K, and multiple the states to get the control input.
• LMPC
  First, I build a desperate state space for cart-pole modle, and then I convert the code for initializing MPC matrices and MPC rollout prediction from matlab to CPP. The part of initializing MPC are included in teeterbot_controller_lmpc.cpp file, and the part of prediction will take use of function quadprog() in matlab, which I have converting it into the CPP code in directory MPC_Prediction and modified CmakeLists to make it works.
• NMPC
  ...TBD

Usage

roslaunch teeterbot_gazebo teeterbot_empty_world.launch
roslaunch teeterbot_controller teeterbot_controller.launch