Omni-CrawlerDevelopment of the Tracked Vehicle with Circular Cross-Section to Realize Sideways Motion

By:Mohamed Mostafa

Problems with tracked vehicles Tracked vehicles are not

capable of sideway motion Therefore it is difficult for it to avoid the obstacles that includes narrow spaces immediately .

Tracked vehicles move on the soft ground( e.g. sand) the edge of the vehicle could sink in the ground.

Solution

Replace the tracks with circular section

The Omni-crawler in action.

http://www.youtube.com/watch?v=0-M3SrsYo1g

How does it work?

The basic concept of the Crawler with circular section is shown in this Fig. The crawler has a circular section. And this crawler module has the active rotational axis. Therefore, the sideway motion can be realized by this configuration.

The prototype

The geared motor rotates the inner shaft ‘s bevel gear s changing its rotational direction to the vertical direction so the shaft of the motor and sprocket is rotated at the end.

At The end of the front and rear of the inner mechanism unit, there are a shaft for the sideling motion of the crawler. By rotating these shafts in rolling axis actively, the sideway motion can be realized.

Prototype cont.

In order to realize smooth sideling motion, the shape of the section of the crawler should be circular. The lug of the crawler is shown in this Fig.

The Surface of the Lug module, the rubber is set to the lug supporter.

The full design

experimentations

A. Step Climbing MotionAs one of the basic mobility

criteria of this robot, the ability to produce step-climbing motion should be confirmed. One example of such a motion is shown in the Fig.

The height of the step is 36mm.

experimentations

B. Gap Traversing

The ability of the vehicle to gap traversing was also confirmed as shown in the Fig

experimentations

C. Moving on Pipe The vehicle’s

mobility on the outside edge of a pipe was also confirmed. It was observed that the prototype with the Omni-Crawler mechanism can traverse along small and large pipes without any adjustments

experimentations

C continued

The ability to move on the surface inside the pipes was also confirmed.

experimentations

D. Moving on Soft Grounds

The vehicle’s ability to move on soft ground was also confirmed, as shown in Fig. 15. We used “Toyoura” sand as the soft ground. The average diameter of this sand particle is about 0.2mm, and the density of this sand is 2700kg/m3. It was observed that this prototype with the Omni Crawler mechanism can move on soft ground smoothly with a low level of sink.

Questions

References

http://web.mit.edu/mobility/publications/IROS08_1351_MS.pdf

http://web.mit.edu/mobility/publications/IROS_1413.pdf