Mecanum Wheel is referred to as the "Wheat Wheel". It is a wheel that can move in all directions. It is composed of a hub and a roller surrounding the hub, and the axis of the roller of the Mecanum wheel forms an included angle of 45° with the axis of the hub. There are many small wheels, called rollers, distributed obliquely on the rim of the hub, so the wheels can slide laterally. The roller is also a kind of small roller without power. The busbar of the small roller is very special. When the wheel rotates around the fixed wheel spindle, the envelope of each small roller will be a cylindrical surface, so the wheel can Scroll forward continuously. The combination of four such wheels enables the device to move in any direction.
And the Mecanum wheel has a mirror image relationship with the AB wheel. If the A wheel can move diagonally to the left front and right back, then the B wheel will move diagonally to the right front and left-back. According to the physical knowledge we learned in high school, the speed can be decomposed orthogonally, then the A wheel can be decomposed into the axial left and the vertical axial forward speed components; or the axial right, and the vertical axial direction after the velocity component. In this way, the velocity component of wheel B and wheel A will become a mirror image relationship.
After knowing the velocity components of the A and B rounds, we can make a relationship combination. For a four-wheeled Mecanum wheel, it is nothing more than the following combinations. AAAA, BBBB, AABB, BBAA, ABAB, BABA, ABAA, BABB...
Can any of the above combinations be able to move in any direction? The answer is: NO! The following is an example of a correct example and a wrong example, and the rest can be reasoned by yourself.
AAAA, as we said before, the speed component of wheel A is either front + left or right + rear. When all four wheels want to turn forward, each wheel will have a speed component in the left direction. This will cause the entire chassis to move to the left when moving forward. In the same way, when retreating, it will definitely move to the right, which makes it difficult to continue, because this thing has been running around uncontrollably. This is certainly not the arbitrary direction we need to move.
The correct Mecanum wheel distribution is ABAB. When the four wheels are all turned forward, the AB wheels can cancel the axial speed with each other, so that only the forward speed is left, and the chassis can move forward without running off track. The same is true for backsliding. If wheel A is rotating forward and wheel B is reversed, the forward and backward speeds will cancel, leaving only the leftward speed, so the chassis will translate to the left; on the contrary, if wheel A is reversed, Wheel B rotates forward, then the chassis will translate to the right; the wheel on the left side of the chassis rotates forward, and the wheel on the right side reverses, the chassis can rotate to the right, and vice versa, the chassis can rotate to the left.
By comparing with ordinary vehicles, we can find that when ordinary vehicles are moving, the wheels all turn in the same direction. When the vehicle using the Mecanum wheel is running in any direction, the movement direction of each wheel is different. Therefore, if the Mecanum wheel wants to move at any angle in the true sense, then each wheel must be A separate motor drive is required.
As a result, a control system is also required to master the steering speed and direction of each wheel.
Since the Mecanum wheel came out, it has been widely used in the field of industrial production. If the environment is harsh and the space is very narrow, AGV trolleys, forklifts, and other equipment using Mecanum wheel technology can advance and retreat freely.