Let’s see what comes to your mind if we talk about the most important invention of all time. Is it fire because it gives us warmth, the ability to cook our meals, and protection?
Well, how about wheels? Most people often describe the wheel as the most important invention of all time. People had to use boats to cross oceans, walk long distances, and carry heavy loads before the creation of the wheel. Vehicles have progressed from horses and carts to automobiles, bicycles, wagons, and even airplanes.
Because of this, transportation, travel, and even agriculture and industry were all fundamentally altered.
A wheel is a circular frame made of solid, semi-solid, or spoked material that can spin on an axle to generate forward or backward motion.
Traditionally and commercially used wheels are easy to imagine in your head. You see wheels in cars, bikes, trucks, planes, etc. These are similar designs, although they differ in material, weight, size, steel belts, and structure.
Depending on their utility in the vehicle, they are given corresponding properties.
But in this reading segment, let us talk about an advanced and unique wheel that serves a flexible motion in all directions. These wheels are called Mecanum wheels.
What is Mecanum Wheel?
A mecanum wheel is a standard wheel to which a set of rollers have been attached, each of which rotates about an axis 45 degrees to the plane of the rotation. It was invented by Bengt Erland Ilon, an engineer in a Swedish company at that time.
This wheel is an omnidirectional wheel design for a land-based vehicle to move in any direction. It is also sometimes called the Swedish wheel. With the ability to move the car in any direction without turning the wheel, this wheel appears as an advancement in the mobility sector.
Mecanum wheel-fitted robots or industrial machines can make a 180-degree turn without taking much space, whereas a typical forklift takes a lot of space and time to achieve the same task.
Mecanum-wheeled machines achieve all these crazy movements in all directions, but their wheels never tilt.
Let us understand the brilliance of the mecanum wheels in depth.
The design behind Mecanum Wheel
The spark of genius that birthed the invention of the mecanum wheel must have occurred when the inventor used a roller angle of 45 degrees.
He used many such free-to-rotate rollers throughout the periphery of the wheel. The side plates will adequately hold the rollers if you make some projections on them. As shown in the image below
Many rollers are arranged at a 45-degree angle and held between the structures on the wheel’s exterior.
The shape of the rollers is designed so that the rim of the all-directional wheel is round. The angled peripheral rollers convert some of the force applied in the direction of the wheel’s rotation into a force perpendicular to the rotation.
This type of wheel can roll indefinitely due to the rubberized rollers attached at an angle around its entire rim. Mecanum wheels can spin in place with low torque and low ground friction because of their design.
But stills remains the question of how does it help in omnidirectional movement?
Types of Mecanum Wheels
Two different designs are popular
One type holds the rollers between the wheel’s frame and the wheel’s frame, and the other has the rollers from the center.
1. The first type of Mecanum wheel has the rollers held at both ends.
This type has a greater load capacity, but they have a disadvantage. When traveling sideways and meeting an inclined plane, the metal rim can collide with the plane.
2. The second type of Mecanum wheel has the rollers held at both ends.
This has lower load capability because the wheels are cantilevered. However, it is much better at dealing with obstacles and inclined planes.
How does this wheel work?
Depending on the direction and speed of each wheel, the resulting combination of all these forces creates a total force vector in any desired order, allowing the platform to move freely in the direction of the resultant force vector without changing the wheels themselves.
As soon as this electric motor-powered mecanum wheel touches the ground, a frictional force is generated at the contact point. The direction of this frictional force depends on the direction of the wheel, whether it is forward or backward.
We have divided this force into a forward/backward and right/left component. The two forward and backward vectors cancel out when the wheels on one side are spun in opposite directions, but the two sideways vectors add up.
When you switch directions with the other two wheels, you increase the number of sideways vectors by four. The combination of these four frictional forces from four wheels on a vehicle gives the vector sum force causing the motion in the desired direction.
The resultant force could provide torque at the of the vehicle if the driver wants to rotate the vehicle.
As you can see above, T1, T2, T3, and T4 are the frictional forces at the contact points of the four wheels, respectively. These forces add up, and the resultant force or torque provides the movement in the desired direction.
A vehicle can move in various directions with minimal space requirements simply by changing the rotational motion speed and direction of each wheel. This is because each wheel’s sum of the force vectors results in linear motion and rotations.
When all four wheels turn at the same rate, the vehicle will move forward or backward because the longitudinal force vectors add up while the transverse force vectors cancel each other out.
- By rotating the vehicle’s wheels in opposite directions, the transverse vectors cancel out. Still, the longitudinal vectors generate a torque around the vehicle’s central vertical axis, causing the vehicle to spin in place.
- When one set of diagonal wheels is rotated in one direction, and the other set is rotated in the opposite direction, the resulting vector sum is transverse rather than longitudinal, causing the vehicle to move laterally.
- So the combination of all these variations helps the vehicle to rotate and move in any direction.
The image above shows all the various combinations of wheel motions that, in resultant, give the direction of motion of the vehicle.
Uses of Mecanum Wheels
Uses of Mecanum wheels involve application in Robotics, wheelchairs, Transfer vehicles, etc. The maneuverability provided by omnidirectional vehicles can be utilized. It can also be vital in numerous other applications, such as search and rescue missions, military activities, planetary explorations, and mine operations.
This wheel is commonly used in robotic applications requiring a high degree of maneuverability, such as those experienced by NASA for hazardous environment exploration.
In hazardous environments where it is too dangerous to send in unprotected personnel, a mobile base could be used to perform remote inspections, site surveys, and operations.
Further applications of tech are being explored, and various alterations of technology are being studied as well.
It also has medical applications like wheelchairs. The OMNI is a standalone wheelchair developed to allow high mobility in complex environments and to have modes of operation that will help the user have higher degrees of independence. This wheelchair has been designed for individuals with severe mental and physical disabilities.
Back then, in 1980, Us Navy bought the patents of invention from the inventor and started research and development processes to see its applications in transportation. These vehicles are now in production.
Mecanum wheels find widespread application in FIRST Tech Challenge, one of the world’s leading youth robotics competitions.
Advantages of Mecanum wheel
- Compact size: The wheels are compact and tightly packed with rollers in between. They are easy to carry and fit well with the vehicle.
- Omnidirectional Capabilities: Mecanum wheels give vehicles and robots autonomous omnidirectional capabilities, while regular wheels don’t. The omnidirectionality that such wheels provide makes the vehicle extremely maneuverable, which could be very helpful in different indoor and outdoor applications.
- High loading capacity: These wheels are very durable and can handle high loads on them. Rollers attached to it increase the strength of the wheel to handle pressure.
Disadvantages of Mecanum Wheel
- Due to the susceptibility of Mecanum wheels to slippage, the lateral and longitudinal distances traveled by a vehicle with such wheels are not the same for the same amount of wheel rotation.
- Vibrations: The second drawback is that the wheel is always in contact with the ground, but the point of contact moves along a line perpendicular to the wheel axis. There are horizontal vibrations are caused by lateral motion.
- Efficiency: Another disadvantage of the Mecanum design is the inefficient use of the motors’ kinetic energy supplied to the wheels.
- Last but not least, its obstacle-overcoming prowess is direction-dependent.
Improving Designs and prospects
To overcome the Mecanum wheel difficulties when moving on rough terrain, researchers and developers have developed two new concepts for this type of wheel, using the principle of “steeping on obstacles.”
- The first one is the concept of the “elliptical Mecanum double wheel.” The wheel consists of two elliptically Mecanum wheels coupled with a special mechanism. The role of the mechanism is to move the components in such a way that the resulting motion would provide the same to the vehicle as a traditional Mecanum wheel would.
- The second concept is the “semicircular Mecanum double wheel .”The idea was to modify the elliptically shaped wheel seen in the image above and replace it with a wheel with half circular and half elliptical profiles, as shown in the image below.
In this case, as the double wheel rotates, the smooth motion of a regular Mecanum wheel is achieved, while the ability to overcome small obstacles when traveling laterally is kept.
In contrast to the elliptical wheel, the semicircular wheel includes three types of rollers (4 of type 1, 2 of type 2, and 7 of type 3), and the total number of rollers is 13. s. This type of wheel is capable of overcoming obstacles of heights up to 37.5% of the wheel’s radius.
Also, both of these types of wheels can move in soft dirt. The wheel would pile up a small amount of dirt and then step on it, thus avoiding being blocked by large amounts of dirt.
Currently, various applications of mecanum wheels are being explored along with unique and better concept designs to maximize the wheel’s utility and quality experience.
The maneuverability provided by omnidirectional vehicles can be utilized and can be very important in both outdoor applications, such as search and rescue missions, military activities, planetary explorations and mine operations, long loads transportation, and indoor applications, like small goods transportation, powered robotic wheelchairs or shopping carts.
Wheels are indeed one of the most important inventions of all time, and mecanum wheels are a potential next step in its evolution.
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