Updated 2/15/05

 Here is a new rear protection bumper design we just came up with for our indoor traversing robot that may be just what your looking for in an inexpensive and very effective bumper design for small robots. The design started to gel when we had to add an extension to the back of the bot to accept the rear drop off sensor array, and an elegant bumper design had to cover the extension plus some of the side areas. We have many hours of "field" testing on this design, and it has held up very well in gentle as well as ramming impact situations.

 Rear view of robot, just below the power switch you can see an extension plate of lexan that will carry the additional sensors for ground detection and drop off sensing. The bumper consists of two .032 inch thick brass strips about a foot long purchased from the hardware store. The inner hoop is connected on both ends with machine screws into the base of the robot. It loops around gently, and connects on both ends to hold it taught. It is connected in the middle with lacing cord to the lexan extension, however the end screws alone were adequate for support and tension.

Mounted on four nylon standoffs, two each side right on the first brass band is a second band, about an inch shorter. It is mounted with nylon screws for electrical isolation and is a constant distance of about 1/4 inch from the inner band. The idea is when force is applied to any part of the band, it deflects inward, touching the inner band and making an electrical contact, thus alerting the robot that it has backed into something and to stop backing up.

Now here's the neat trick - see the next image!

  When you press on any part of the band (except right next to the nylon spacers of course) the band deflects inward, and the other parts of the band expand OUTWARD like pushing jello around. This gives it the proper spring tension on any surface of impact.
  Now here is a side impact, note that the opposite side bulges outward in a springy, and will then return to the neutral position ready for the next impact. Even ramming into hard walls will not dent the brass, and it is sensitive to the light touches as well for our 10 pound robot.

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