The Mecanum wheel is a type of omnidirectional wheels which can be used to steer four wheels vehicle by controlling the rotation of individual wheel without changing the direction of the wheels.
It can also be used for conveyor wheels to move and turn objects omnidirectional ways.
The Project Crab
A Japanese hobbyist Osamu Ohashi built a Mecanum Wheel Rover using affordable components. He named his project “Crab” based on the sidewalk capability that Mecanum wheels provide.
Mr Ohashi also has shared the building instructions for his rover on GitLab.
Build Guide: Project Crab (Mecanum Wheels Rover)
Although his rover movements are already taking advantages of the Mecanum wheels, the project Crab is still in progress he indicates. The rover could become a self-driven robot soon in the future.
Mecanum Wheel Use Cases
The precise motor controls could be complex to steer a rover using Mecanum wheels, but its direction and the movement are unrelated as a result. This means immediate movement in any direction can be performed without preliminary actions nor an extra space to do so.
Also, it could change the facing direction while travelling in a particular direction.
Evasive Manoeuvres
The movement of a device steered by Mecanum wheels are hard to predict. It can move in any direction without any preliminary actions. Which makes it ideal for robot sport/battle situation where quick movements are required.
Chasing & Catching
Chasing & Catching a running animal/human is a challenging task for a robot. However, there may be an opportunity for a device using Mecanum wheels by being able to make a quick move in any direction without preliminary actions. I found a couple of example cattle chase robots on the internet, but I haven’t yet seen one using Mecanum wheels.
I had an opportunity to chase cattle in a large open space myself. It requires speed and physical strength to keep up with cattle movements that constantly making sudden changes in direction. I tried with a 4WD vehicle but it was too slow to keep up with their movements. I’ve given up and gone back to a traditional horse riding method in order to chase them.
Camera, Video & Gun Shooting
The rover with Mecanum wheels not only can move in any direction, but also can do so without losing control of its facing direction. In theory, the rover could continuously record a video of a moving object from different angles while travelling with the object. In other words, it could move like the moon travelling & rotating around the earth without changing the facing direction against the earth.
Combine this feature with evasive manoeuvres and chasing ability with a gun instead of a camera might make the rover into a unique weapon.
Flexible in Confined Space
There are different ways to steer a land-based vehicle. Our ordinal cars for example requires additional space to steer its direction. The 2 wheels rover (such as robot cleaners) can turn virtually without additional space but facing direction must be changed to make turns. A vehicle using Mecanum wheels should be able to take a turn in a confined space without even changing its facing direction.
This may be ideal for an inspection robot to travel a narrow trail with multiple sharp turns without changing facing direction and adjust its position without losing sight of what is inspected.
Rotating Sphere
The device with Mecanum wheels could be placed inside of a sphere to control a sphere rotation (like the BB8?).
By making an idea upside down, Mecanum wheels can be a base to rotate a Globe Sphere automatically.
Conclusion
The Mecanum wheels have new features on top of what ordinal wheels offer. Which makes it easier for us to apply this technology by replacing the ordinal wheels. However, our ideas can easily be trapped within the limitation of ordinal wheels at the same time.
I think rover with Mecanum wheels are best controlled by a computer to squeeze out the full potential.
The movement such as changing the facing direction independent to the travelling direction requires complex motor controls probably with gyrosensor feedback (especially when it is moving based on the movement of a different object).
If I’m the one controlling the rover, I prefer to have 2 separate controls similar to first-person shooter games:
- to move towards different directions (WASD)
- to rotate vehicle while it is on the move (Mouse)
I wish I have the device right now to try this myself.
