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Revision as of 13:48, 8 May 2014 by Sedlacek (talk | contribs) (Parts List)


Omniwheels are wheels with small rolls around the circumference which are perpendicular to the rolling direction of the wheel. Thus the wheel possesses the ability to slide in axial direction with great ease. Omniwheels are used in systems with omnidirectional drive mechanism like the Robotino 3. Since these systems only use three wheels, the wheels need the ability to slide in perpendicular direction. The main benefit of this drive mechanism is the capability to drive in every direction e.g. you can move your robot sideways without rotating it. However there are also some downsides. In order to guarantee a smooth motion, the outer contour of the rolls has to form an exact circle. This is illustrated in figure ##.

REC omniwheel

REC omniwheel
Barrel-shaped roll of the REC omniwheel(including bush bearings)

The wheels used in the Robotino 3 system do not provide the exact geometry mentioned above. The consequence is that the robot oscillates when carrying out certain motions e.g. rotating with high velocity. This problem formed the impulse for developing an omniwheel which resolves this issue.

The corpus is milled out of aluminium in order to provide a high accuracy and low weight. The rolls are custom produced. They are constructed as a turned part of polycarbonate which is surrounded by a casted part made of polyurethane. The solid PC core provides rigidity and holds the sintered bush bearings which are used to reduce the friction. To avoid runmarks on smooth grounds the PU is transparent. Furthermore the PU-material provides a certain flexibility to adapt to ground bumps and supplies a good grip on smooth grounds.

For using these wheels on the Robotino 3, the REC omniwheels are mounted on custom developed shafts which have to be attached to the robot. The wheels are fixated on the shaft with a lock ring. The torque is transferred by a feather key.

Parts List

The following parts list tabulates the parts needed for a set(=3 pcs.) of REC omniwheels.

Description Quantity
REC omniwheel corpus 3
REC omniwheel shaft 3
REC omniwheel rolls 48
flat headed screw with hexagon socket - ISO 7380-M4x10 – steel 10.9 (zinc-plated) 48
Unterlegscheibe DIN 9021-4,3 - Stahl 48
Sicherungsring für Wellen – DIN 471-15x1 - Federstahl 3
Sicherungsring für Wellen – DIN 471-17x1 - Federstahl 3
Passscheibe – DIN 988-17x24x0,1 - Stahl ca. 15
Passfeder DIN 6885-A-5x5x20 – Stahl C45K 3
Zylinderstift ISO 2338 - 4h8x36 - Automatenstahl 1.0718 48
Zylindergleitlager 4x8x12 E7/r7 - Sinterbronze 96