Saturday, October 30, 2021

Centi (#6) - Playing with the Design


Perhaps it is time for some new perspective after a pause of 2 years.  For a "Weekend Project", I decided to re-examine the Centipede design that I had started before.  At this time, I have a bit more experience with gears and how to make the daisy-chain of gears that would be necessary for this type of robot.  I wanted to verify, with a physical test, how such a mechanism could fit together and if the gear train would have enough torque for it to actually move the robot.  For this test, I have learned much more about the potential, and as well as some limitations.

Centipede Robot V4 - Frame and Gears

I really liked the Hexagonal design of the previous version. Making the CAD files for that design was a lot of enjoyment.  However, that design was just not practical. It required too much printing, and ultimately did not solve any issues that could be designed away. The coverings prevented the ability to fix the leg-lever without taking it apart. So, at this part in the design process it needed to be simplified.

The new Design re-uses the ball-Socket universal joint from the previous version. It creates a frame, that will have a train of gears on it.  With proper use of variables for the distance and separation between the gears, it was possible to make this design parameter driven. I could create a 3 or 4 leg frame or any number.  In fact, I started with 4 legs, and for just the Proof-of-Concept, I reduced it down to 3.

I was able to quickly print out the new design.  I was able to re use the chopsticks as well as the ball and socket parts.  I also had some 3D printed gears already in the works from the Tilt! and Gear-box projects. I am currently satisfied with using the 1.5 modulus for the Gear teeth to radius design. It is larger than 1.0 and much easier to print and start using.

Assembly of the Prototype

Completed Prototype Test frame for Centipede Robot

Here is the proof of concept constructed and working. At the end, I use a gearbox to drive the prototype. The short video is on my YouTube channel.

Wow, ultimately it could look like this with 18 legs. This would be about 40 cm wide and 50+ cm long (without a head).  

18 leg Centipede Robot

So this all seems possible, with a bit more printing and design work. I think for the full version, It would need to have a complete cycle on downlegs.

If you have more interest in what research is being done with Myriapod robotics. Here is a paper written by Yasemin Ozkan-Aydin while at Georgia Tech:  A systematic approach to creating terrain-capable hybrid soft/hard myriapod robots  While their approach is to build small single actuated legs, I am attempting to use recycled motors with minimal actuation. My approach is considerably more challenging (needless constraints?). I feel that the research in there paper will have faster and more interesting results.

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