Custom Ackermann Controller for ROS2

This ROS2 package provides an enhanced Ackermann steering controller with a smooth bicycle kinematic model, designed for accurate robot simulation and navigation in ROS2 Jazzy. It handles numerous edge cases.

Key Features

• Smooth Bicycle Kinematics: Implements δ = atan(L*ω/v) for accurate, Nav2-compatible steering. The controller logic is designed to prevent jerks and ensure smooth motion.
• Robust Edge Case Handling:
  • Turning in Place: Manages commands with only an angular.z component (and linear.x is zero), allowing the robot to remain stationary.
  • Velocity Deadzone: Velocities below 0.001 are treated as zero to prevent minor drift from joystick noise.
  • Handles various other scenarios to ensure stable and predictable behavior.
• Persistent Steering: Maintains the current steering angle even when the robot is stopped, allowing for precise maneuvering.
• Command Timeout with Auto-Reset: If no commands are received for 2 seconds, the steering angle gradually and smoothly returns to the center position.
• Teleoperation Options:
  • PS4 DualShock 4 Controller (Recommended): Uses joy and teleop_twist_joy for responsive control.
  • Standard Keyboard: Uses the standard teleop_twist_keyboard for basic control.

Demonstration

Below is a demonstration of the Ackermann controller in action within a Gazebo simulation, controlled using a PS4 controller.

Ackermann.Drive.Bot.operated.using.a.PS4.controller.webm

Dependencies

• ROS2 Jazzy Jalisco
• ros-jazzy-teleop-twist-joy
• ros-jazzy-joy

To install dependencies:

sudo apt-get update
sudo apt-get install ros-jazzy-teleop-twist-joy ros-jazzy-joy

Installation

1. Navigate to your ROS2 workspace's src directory:

   cd ~/prototype_autonomous_bot_cir_ws/src

2. (If not already present) Clone the repository:

   # git clone <your-repo-url>

3. Build the package using colcon:

   cd ~/prototype_autonomous_bot_cir_ws
   colcon build --packages-select custom_ackermann_controller

4. Source the workspace:

   source install/setup.bash

Usage

To run the full simulation, open three separate terminals.

Terminal 1: Launch Robot Simulation

source ~/prototype_autonomous_bot_cir_ws/install/setup.bash
ros2 launch bot_description gazebo.launch.py

Terminal 2: Run the Ackermann Controller

source ~/prototype_autonomous_bot_cir_ws/install/setup.bash
ros2 run custom_ackermann_controller ackermann_twist_controller

Terminal 3: Choose a Teleoperation Method

Option A: PS4 Controller (Recommended)

Ensure your PS4 controller is connected via Bluetooth or USB. You may need to set permissions for the joystick device:

sudo chmod 666 /dev/input/js0

Launch the joystick teleop node:

source ~/prototype_autonomous_bot_cir_ws/install/setup.bash
ros2 launch custom_ackermann_controller joystick_teleop.launch.py

PS4 Controller Mappings:

Control	PS4 Input	Function
Movement	Left Stick Up/Down	Forward/Backward (linear.x)
Steering	Left Stick Left/Right	Turn Left/Right (angular.z)
Enable	L1 Button	Must hold to activate movement
Turbo	R1 Button	Hold for faster movement

Option B: Standard Keyboard Teleop

This uses the standard ROS2 keyboard teleop but does not support simultaneous forward and turning commands.

source ~/prototype_autonomous_bot_cir_ws/install/setup.bash
ros2 run teleop_twist_keyboard teleop_twist_keyboard

Nodes & Scripts

ackermann_twist_controller

The core node that subscribes to /cmd_vel (Twist messages) and converts them into Ackermann steering and velocity commands. It publishes Float64MultiArray messages to the `/forward_position_contro[...]

test_ps4_controller.py

A diagnostic script to test the PS4 controller. It subscribes to the /joy topic and displays crucial real-time information, including the raw data received from the controller and the corresponding [...]

Launch Files

joystick_teleop.launch.py

Launches the joy_node for joystick communication and the teleop_twist_joy node with pre-configured parameters for a PS4 DualShock 4 controller.