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Mecanum Wheels

Prerequisites

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Components

Mecanum Wheels

Mecanum wheels are a common way of giving mobile robots holonomic motion abilities. While not flawless e.g., difficult terrain traversal with mecanum wheels is much more difficult, mounting mecanum wheels to Leo Rover comes with many benefits, with the most important being:

·       Ability to strafe.

·       Great reduction in resistances seen while driving (especially when turning).

·       Chance to mount heavier payload.

What to expect?

Having finished the tutorial you'll know how to convert Leo Rover to holonomic motion mode.

Prerequisites

No items found.

List of components

·       Mecanum wheel x 4 (2 for each roller orientation)
·       Mecanum torque plate   x4

Mechanical integration

There are two ways mecanum wheels can be arranged:



While both configurations can work, “X” from the top seems to be more prevalent in robotics as it makes turning around the center more consistent. That’s why software we provide assumes the „X” configuration is being used.

Remove the 5 screws holding torque plate in place.
Remove the torque plate, rim and tire.
Slide the mecanm wheel with correct roller orientation onto the motor tube.
Attach the new, wider torque plate using the same screws you’ve removed before.
Repeat the steps for each of the 4 wheels of the rover.



Wiring and electronics connection

Software integration

Adding the wheels to the software is really simple. You only need to change a single thing in one file and restart the rover. In /etc/ros/setup.bash file there is one environment variable MECANUM_WHEELS that is exported to the system. You need to change its value to true:

/etc/ros/setup.bash

You can edit the file using this command:

And then save its content with ctrl+o and confirming with enter. You exit the program with ctrl+x.

Once it's done, you can just reboot the rover, and the wheels will be included in the software running on the robot.

Examples

Visualize Robot Model

If you have ROS installed on your computer, you can see the robot model with the mecanum wheels attached in rviz.

Before making any further steps, make sure you completed the Connecting another computer to ROS network section of ROS Development tutorial:

ROS Development -> Connecting another computer to ROS network

To see the model, start rviz, and add robot model in the display view. Chose also base_footprint as fixed frame, and you should see the rover model with mecanum wheels attached.

leo rover robot model in rviz with mecanum wheels

What next?

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