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The robotic snake shown here is called R7[1]. This was built at Hughes Aircraft in the late 1980's
before snake-like robots began to "take-off." I call it R7 because when I heard that I had funding
to build a robotic snake for inspection purposes I rushed home and quickly sketched 10 different
robot designs. This robot was the 7th robot I sketched. This robot was actually
preceded in construction by another robot (unnamed).
This other robot was built in 1 month as a proof of concept. I typically like to build
a proof of concept design very rapidly and then use that experience to build
a good final design.
R7 took much longer to design (about 3 months).
R7 carries a CCD element at its tip.
The key innovations of R7 are 1) the motor are remote from the axes being driven. Power is transmitted to the joints via low force/ high velocity cables. At each joint we have a 11:1 reduction drive. The use of a reduction drive allows the use of low force cables. The use of low force
cables reduces the load on the structure as well as significantly reduce
cable wear.
I was able to generate very high movment speeds (the tape shows rather slow movement.)
2) The second innovation is that we use double differential drives, coupled together to get
a smooth bending motion. The system has a total of 16 axes but has only 8 degrees of freedom
due to the coupling.
Another innovation, not related to robots, was the development of an abrasion resistant cable.
A fellow engineer and I were able to vapor deposit conformal coating using a plasma chamber. This
increased the longevity of the delicate Kevlar cable by 5 orders of magnitude.
The video you see on this page is of R7s first day of operation. I think that was around May of 1987.
In the video, only 5 of the 8 degrees of freedom are active. Can you tell which ones?
This robot was funded by a Hughes IR&D grant.
[1] M. Anthony Lewis and David Zehnpfennig, R7: A Snake-Like Robot for 3-D Inspection, IROS 1994, Munich.