BLDC motored wheels

Brushless DC (BLDC) motors offer high efficiency, smooth operation, and excellent power density, making them a common choice in robotics and automation. Their electronic commutation provides better control and reliability compared to traditional brushed motors.

In this project, we replace the stock wheel motors of our robot with more powerful BLDC motors, resulting in significantly higher speed and improved overall performance. This tutorial outlines the key steps and considerations involved in integrating BLDC motors into a mobile robot platform.

What to expect?

After completing this tutorial, you will have a fully operational Leo Rover equipped with BLDC motor-driven wheels

Software integration

To make the process as straightforward as possible, we've prepared a dedicated version of LeoOS that includes all the necessary software for the BLDC motor system. Simply download the image, flash it onto the SD card, and insert it into the robot.

You can follow this guide for detailed instructions on flashing the OS image:

📄Software update

Detailed guide on updating the software of Leo Rover, covering steps to access the microSD card, download and flash the latest LeoOS image.

Once the new system is installed, ensure that LeoCore is properly communicating with it by updating the firmware on the board.
Follow this guide to update the firmware:

📄Firmware update

Learn how to easily update Leo Rover's firmware from Raspberry Pi without extra cables. Step-by-step guide.

After completing the firmware update, reboot the robot or restart the ROS nodes:

ros-nodes-restart

Now you should be able to control the robot with BLDC motors in their default configuration.

Configuration

The prepared BLDC motor integration is highly configurable — you can adjust each parameter at runtime to observe how it affects the system and the rover's behavior.
This part of the tutorial will guide you through accessing one of the most convenient interfaces for configuring these parameters.

You will need ROS Jazzy installed on your computer. If you don't have ROS installed, follow this guide:

📄Install ROS on your computer

Learn how to install the Robot Operating System (ROS) on your computer.

tip

If for some reason you don't want to install ROS on your machine, you can always use the ros2 param CLI tool which will allow you to change parameter values - you just have to connect to the rover through ssh.

📄Connect via SSH

Learn how to establish an SSH connection with your Leo Rover and access its terminal using Putty or OpenSSH.

You can learn how to use ros2 param tool from this tutorial.

Before configuring any parameters, make sure your computer is connected to the rover's access point:

📄Connect to Leo Rover AP

Learn how to connect to your Leo Rover via WiFi.

Next, connect your local ROS environment to the one running on the robot.
To do so, source either the /opt/ros/jazzy/setup.bash file or the install/setup.bash file from your ROS workspace (if you have one).
Then verify the connection by running:

ros2 node list

If this command displays a list of running nodes, the connection has been established successfully. You can now launch the configuration interface:

rqt -s rqt_reconfigure

info

If this command returns an error, the plugin might not be installed. Install it by running:

sudo apt install ros-jazzy-rqt-reconfigure

In the rqt window, select the bldc_manager node from the list on the left side of the screen. You will see all available parameters that can be configured in real time.

Hover your cursor over a parameter name to display its description and learn what it controls.

The next section provides a detailed explanation of each parameter, including valid value ranges and usage notes.

Parameters

The parameters are divided into three main groups:

• node parameters - general settings that affect the ROS-related aspects of the system.
• wheel controller parameters - define the BLDC motor configuration and behavior (these apply to all motors simultaneously).
• robot controller parameters - used primarily for odometry calculations and system timeouts.
  It's recommended to leave these unchanged unless you know exactly what you're adjusting.

bldc_manager node

• mecanum_wheels (type: bool, default: false)
  Indicates whether the rover is equipped with mecanum wheels.
  When set to true, the robot operates in holonomic motion mode.
  When set to false, it uses differential motion mode.

• max_linear_velocity (type: float, default: 5.0)
  The maximum linear velocity of the robot, expressed in meters per second.
  Accepted values range from 0.1 m/s to 20.0 m/s.

  info

  Keep in mind that even though the parameter accepts high values, the physical rover may not be capable of reaching them.

• max_angular_velocity (type: float, default: 4.8)
  The maximum angular velocity of the robot, expressed in radians per second.
  Accepted values range from 0.1 rad/s to 20.0 rad/s.

  info

  As with linear velocity, higher values may exceed the physical limits of the rover's drivetrain.

• tf_frame_prefix (type: string, default: '')
  Prefix added to the names of published TF frames.

• robot_frame_id (type: string, default: base_footprint)
  The TF frame associated with the robot base.

• odom_frame_id (type: string, default: odom)
  The TF frame associated with odometry readings.

• wheel_joint_names (type: string[], default:
  ['wheel_RL_joint', 'wheel_RR_joint', 'wheel_FL_joint', 'wheel_FR_joint'])
  The names of the wheel joints used in the joint_states topic.
  The order of names is: rear left, rear right, front left, front right.

• wheel_odom_twist_covariance_diagonal (type: float[], default:
  [0.0001, 0, 0, 0, 0, 0.001])
  The diagonal elements of the covariance matrix for standard wheel odometry twist readings.
  The array must contain exactly six values representing variances for linear x, linear y, linear z, angular x, angular y, and angular z.

• wheel_odom_mecanum_twist_covariance_diagonal (type: float[], default:
  [0.0001, 0.0001, 0, 0, 0, 0.001])
  The diagonal elements of the covariance matrix for mecanum wheel odometry twist readings.
  The array must contain exactly six values representing variances for linear x, linear y, linear z, angular x, angular y, and angular z.

Wheel Controller

• max_torque (type: float, default: 1.5)
  The maximum torque that the motors can produce (in newton-meters).

• pid_constants (type: float[], default: [0.2, 0.5, 0.0])
  The proportional (P), integral (I), and derivative (D) constants of the PID controller.
  The array must contain exactly three non-negative values.

  warning

  This is one of the most critical parameters, as it significantly affects how the rover drives.
  Incorrect configuration can result in poor control, unstable motion, or even motor damage.

  When using the D component, keep its value low (preferably below 0.0001).
  A high derivative value can make the motors noisy and increase the risk of overheating or failure.

• pid_integral_max (type: float, default: 20.0)
  The upper limit for the output of the integral component in the PID controller (in radians per second).
  The value must be non-negative.

• profile_velocity (type: float, default: 6.0)
  The target velocity for the velocity profile motion mode (in radians per second).
  Acceptable values range from 0.0 rad/s to 60.0 rad/s.

• profile_acceleration (type: float, default: 6.0)
  The target acceleration for the velocity profile motion mode (in radians per second²).
  Acceptable values range from 0.0 rad/s^2 to 100.0 rad/s^2.

• motion_mode (type: int, default: 0)
  The motion mode used by the motor controller.
  Possible values are:

  • 0 - VELOCITY_PID
  • 1 - VELOCITY_PROFILE
  • 2 - IDLE
  info

  You can read about the VELOCITY_ modes here. In IDLE mode the motors don't produce any torque.

• min_velocity (type: float, default: 0.1)
  The minimum velocity for a wheel to be considered rotating (in radians per second).
  This threshold is used to detect when the rover is stationary, allowing the system to disable motor effort to conserve power when appropriate.

Robot Controller

• diff_drive/wheel_radius (type: float, default: 0.0625)
  The radius of each wheel (in meters).
  Valid range: 0.01-0.2.
  Used only when the mecanum_wheels parameter is set to false.

• diff_drive/wheel_separation (type: float, default: 0.358)
  The distance between the centers of the left and right wheels (in meters).
  Valid range: 0.1-1.0.
  Used only when mecanum_wheels is false.

• diff_drive/angular_velocity_multiplier (type: float, default: 1.76)
  A scaling factor for angular velocity.
  The angular velocity in the cmd_vel command is multiplied by this value,
  while the calculated odometry's angular velocity is divided by it.
  Valid range: 0.01-5.0.
  Used only when mecanum_wheels is false.

• mecanum/wheel_radius (type: float, default: 0.0635)
  The radius of each mecanum wheel (in meters).
  Valid range: 0.01-0.2.
  Used only when mecanum_wheels is true.

• mecanum/wheel_separation (type: float, default: 0.354)
  The distance between the centers of the left and right mecanum wheels (in meters).
  Valid range: 0.1-1.0.
  Used only when mecanum_wheels is true.

• mecanum/wheel_base (type: float, default: 0.3052)
  The distance between the centers of the front and rear mecanum wheels (in meters).
  Valid range: 0.1-1.0.
  Used only when mecanum_wheels is true.

• mecanum/angular_velocity_multiplier (type: float, default: 1.0)
  A scaling factor for angular velocity in mecanum drive mode.
  The angular velocity in the cmd_vel command is multiplied by this value,
  while the odometry's angular velocity is divided by it.
  Valid range: 0.01-5.0.
  Used only when mecanum_wheels is true.

• input_timeout (type: int, default: 500)
  The timeout (in milliseconds) for cmd_vel messages.
  The controller is disabled if no command is received within this period.
  Setting this value to 0 disables the timeout.
  Valid range: 0-2000.

• effort_timeout (type: int, default: 500)
  The timeout (in milliseconds) before motor effort is released.
  If the robot remains stationary for this duration, motor effort is set to zero.
  Valid range: 100-2000.