#MAKE
04/21/16
How to use omnidirectional wheels and mecanum wheels?
Below we will analyze the three most common ways to use them to get basic movements, after understanding them you will see that you have no problems to understand complex systems too. The analyzed conditions have many axes of symmetry, and this greatly facilitates the work, but in some situations it might be useful to have asymmetrical systems to favor one direction than another. In fact, simplifying everything it can be reduced to a vector sum and therefore the possible combinations are practically infinite..
Using four omnidirectional wheels on a robot, positioned as in the graph above, and managing the speed of rotation of each of them, we can make the robot move in any direction. The animation shows the basic movements that are obtained by combining the speed and direction of rotation of these special wheels; these ones could already be enough, but the possible combinations are actually unlimited. This happens because, to calculate the speed and the trajectory of the robot movements, we must calculate the resultant of the speed vector sum of the wheels and the moment sum produced by them: if they are both different from zero, the robot will move along a circular trajectory of radius larger or smaller depending on what combinations we choose; instead, if the speed sum is equal to zero and the moment sum isn't, the robot will rotate on itself; while, if the moment sum is equal to zero and the speed sum isn't, then the robot will make a rectilinear movement. Of course, in reality these movements are approximated because it is difficult to have all four wheels on the ideal position and it is also difficult to make them move with the ideal speed: these approximations cause errors that in most of cases can be ignored, but you should keep it in mind if you need precise movements.
This is our ThunderRobot that uses four of these wheels: watch the video.
Do you want to try to make a robot that goes in all directions too? Buy now the kit of four omnidirectional wheels of the measure that is more suitable for you and you will also have the opportunity to ask us to customize the motor shaft hole according to what you need.
Exactly like in the previous situation, using three omnidirectional wheels on a robot, positioned as in the graph above, and managing the speed of rotation of each of them, we can make the robot move in any direction. Most of the considerations that we made in the description of the case with four wheels are equal for this case, the main differences are that with three wheels the maximum speed is lower and the difficulty of managing the movements is greater. However, having a wheel in less, and so a motor in less too, the robot is lighter and this can be useful in situations where weight is an important factor. The animation shows the basic movements that are obtained by combining the speed and direction of rotation of these special wheels. Pay attention that in the cases of shift to the right and to the left the arrows are smaller, this indicates that to make these movement the speed of these wheels must be 50% of the wheel of the opposite side; this because, as mentioned before, in order to make the robot make a rectilinear movement we need that the moment sum produced by the wheels is zero.
This is our ThunderOmnibot that uses three of these wheels: watch the video.
Do you want to try to make a robot that goes in all directions too? Buy now the kit of three omnidirectional wheels of the measure that is more suitable for you and you will also have the opportunity to ask us to customize the motor shaft hole according to what you need.
Using four mecanum wheels on a robot, positioned as in the graph above, and managing the speed of rotation of each of them, we can make the robot move in any direction. The animation shows the basic movements that are obtained by combining the speed and direction of rotation of these special wheels. How they work is very similar to how the omnidirectional wheels work, in fact, also in this case to calculate the speed and the trajectory of the robot movements, we must calculate the resultant of the speed vector sum of the wheels and the moment sum produced by them. Pay particular attention that in the animation, near the wheels, there are letters A and B, these indicate the two types of mecanum wheels, RH and LH, which work in the opposite way. For example, when a RH wheel is sliding to the left it also rotates forward, while a LH wheel rotates backwards. Therefore, combining these features, you get the movements shown in the animation (You can see that the combinations are the same that are described in the animation of four omnidirectional wheels).
Do you want to try to make a robot that goes in all directions too? Buy now the kit of four mecanum wheels of the measure that is more suitable for you and you will also have the opportunity to ask us to customize the motor shaft hole according to what you need.
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