What is omni wheel ? this question might be the reason why you’re here right now. If you’re new in robotics field and still don’t know about these wheels, you’re in the right place. In this article we’re going to talk about what omni wheels are and how they work.
The Omni Directional Wheel is a kind of wheel that can freely role in more than one direction.
This is the main reason why they have become so popular among robotic students, industrial robot manufacturers and even unprofessional people who are just interested in creating robots.
In order for robots to move on a solid surface, there are several solutions. The most popular solution is using wheels and legs. But Due to aesthetic purposes, wheels are the most used equipment in robots.
Generally speaking, omni directional wheel is mostly used in mobile robots such as junior soccer robots, small size robots, and middle size robots since it does not need to rotate first for moving from one point to another in a straight path. It has some extra wheels along its circumstance which allows the wheel roll laterally in addition to the normal rotation.
Small, medium and junior soccer robots are used in robocup competitions.
But What is robocup?
If you have not heard about this exciting competition, you need to know that RoboCup is a scientific competition which is designed and held to help lots of fields like mobile autonomous robotic, soccer robots, electronics, robot wheels, image processing to develop. This opportunity is one of the reasons behind development of different robots like soccer robots and rescue robots.
In middle size leagues (MSL) which is a soccer league in robocup competitions, the time a robot needs to reach to the ball is really important. The faster the ball gets, the chances of scoring a goal will increase and with an Omni Directional Wheel, this will be possible.
Another application of these wheels is that by using them, a non-holonomic robot can be changed to a holonomic one. The non-holonomic robots are slower than holonomic due to two main reasons. the first reason is forward/backward movement and the second reason is rotating. But by using Omni Directional Wheel, a robot can rotate and move in every desired direction without changing the direction of the wheels.
As we mentioned earlier, omni wheels move in any direction but in this section, we’re going to talk about how they actually work.
First of all, we have to say that omni wheels have small rollers. These rollers are mounted around the wheel and make side to side movement possible. In fixed robot wheels, movement of wheel is prior to the movement of robots. In other words, robots with fixed wheels can only move if their wheels start moving.
In order to understand how omni wheels work, you need to know about rollers.
Rollers are the only reason that omni wheel can move side to side. Omni wheels can have a few or many rollers. The rollers are made out of rubber to minimize the amount of friction caused by rolling on the ground.
These rollers have a crucial role in robot movement. if you search for these wheels you can see that there is an empty space between each roller. if the space between rollers are considerable, chances are, the wheel will rub against the ground. so in order to prevent rolling friction, this empty space must be filled.
This empty space can be filled with mounting more rollers on the wheel. but there is another way to fill this empty space. We can also use a double plate omni wheel. these specific wheels consist of two omni wheels which are attached together in way that can fill the empty spaces between their rollers. This way when the rollers start moving, there will be no friction between the wheels and the ground.
if you want to get more information on omni wheels and how they work, you can check out our article “get rolling with omni directional wheels” which was published on servomagazine as a guest post.
After getting familiar with omni directional wheels and how they work, you may be wondering how you can choose them based on your specific needs.
When you’re trying to choose these wheels for your robot, there are some things you need consider.