Omni wheel

An omnidirectional drive, english omnidrive called, is a drive with a special wheel design, with which a vehicle can travel at any time in any direction. Most of this drive is used in robotics and heard at football robots next to the Omnivision for years as standard.

Design and function

The core of an omnidirectional drive is a so-called Allseitenrad or omnidirectional wheel, called from the English also Omniwheel. On the peripheral surface of a main gear more, generally barrel-shaped auxiliary wheels are mounted, whose axes of rotation lie at a right angle to the axis of rotation of the main wheel.

If the main gear driven, block the auxiliary wheels and serve as a running surface of the main wheel. If the drive is stopped and the vehicle is moving in a different direction, for example by a second, mounted at right angles Omniwheel, rotate the auxiliary wheels and thus minimize the frictional resistance of the wheel. Through this kind of construction, a fast movement in almost any angle is possible to the direction of the main wheel.

Alternative designs

To overcome the two main drawbacks of the Allseitenrades, the rough running and low load, there are two alternatives substantially.

The Mecanum wheel is similar to the Allseitenrädern, but has much less auxiliary wheels. They are basically designed as spherical rollers arranged greater than the Allseitenrad and 45 ° to the axis of rotation. Through the other shape of the auxiliary wheels, it is possible to realize a closed contour of the tread, which enables a smooth operation as similar to a normal wheel. However, smaller Mecanum wheels have problems on uneven ground and require a more complex storage in order to avoid the static overdetermination.

Mecanum wheels are used either in smaller robots for research or to move very large loads.

A two-axis module is an integrated module, including a classic drive, which can also be actively rotated and oriented about its vertical axis. This solution is technically the most complex, but also has clear advantages. The single large drive wheel can drive even on rough or dirty terrain and even over small obstacles (cable, joints), without causing slippage and thus Odometrieproblemen. Since all wheels are driven and actively steered, static overdetermination is harmless in many cases and does not lead to loss of control of the vehicle. A vehicle with two-axis modules may indeed omnidirectional but not always move smoothly since before riding in some cases only briefly, the wheels need to be aligned.

Two-axis modules are used primarily in the research of service robots such as the Care-O- bot 3 and in the DESIRE technology platform.