Over on Instructables, I found a tree-climbing robot built by a high school senior. This is a great project, especially since it was done by someone with no formal engineering experience. The basic idea is a segmented robot with a front half and a back half, connected by a telescoping spine. Each half has four legs tipped with a sharp spike. The front half grips the tree with its legs, and the spine retracts, raising the back half. Then the back half grips, the front half loosens, and the spine extends, raising the front half. The front half grips the tree, and the process repeats, with the robot climbing sort of the way an inchworm does.
Most of the robot is built from a length of 3/4 inch x 1/8 inch aluminum bar. He cut, bent, drilled, and filed pieces of the bar to make legs, the frame, and various clamping bits. The linear slide that guides the spine is made from round steel bar and brass tubing. The original plans called for a rack and pinion to extend and retract the spine. In the end, he used a threaded rod to save money. He also repurposed a hard drive bearing as a thrust bearing for the threaded rod. An old laptop battery serves as the power source for the leg motors.
He used 7rpm DC gear motors to control the legs and another DC hobby motor to extend and retract the spine. The motor controller used three full H bridge L298 chips, and the overall control was provided by an Arduino. To be able to climb different sized trees, the Arduino samples the position of the legs. When it senses that they are slowing down, it assumes they have gripped, and it turns off the power.
Improvements?
I think this is a pretty good project. In fact, it has been entered in the Epilog laser cutter challenge over on Instructables. There’s always room for improvement, however. In the case of this project, I think it’d be improved with a lot fewer screws, drilled holes, and filed grooves. Generally, make the thing simpler. Instead of attaching a T pin to the end of each leg to provide a sharp point, the point could be part of the leg material. Or the leg could simply be made from steel rod bent to shape and sharpened on the end.
It also would be nice not to have to use four gear motors to drive the legs. Instead of a motor per leg, a linear actuator could be attached to one leg and pull the other leg toward it, similar to the cable-operated brakes on a bike. The return action could be provided by the actuator, or simply by a spring.
I agree with William for the most part. Having been the user and or technician working on the end product, I am often frustrated with the lack of forethought that sometimes goes into the engineering and design of a product.
For example, It was pointed out that the t-pins were an "unnecessary extra" and that the climbing 'points' could be designed right into the legs... this may be fine for initial usage but what happens when the tip gets blunted or dull over time? Or worse yet, somehow bends? Then you have to disassemble and rework an entire leg rather than replacing a single tip.
There have been many times when I have had to rework some aspect of a product that has failed to meet expectations once it hit a real world scenario. On the one hand, it is good business for me in correcting these flaws, however these flaws are still sad to see when things could have been done so much better.
We as designers and engineers need to remember and actively think about the environment our products will be working in and the abuses to which they may be subjected... this greatly improves the perceived value and noted reliability of our products.
This is a great project and excellent implementation. Its nice to see some engineering enthusiasm in young people. We need the next generation of engineers to be engaged now. Several times I have volunteered as a Science Fair judging in past years. American innovation is alive and well in the youth of America and this tree climbing robot is another great example!
Thanks for the comments everyone. The original sketch showed two legs connected with a gear mechanism, with one leg moved by a motor and the other moving in an equal and opposite motion via the gear. The inventor didn't use that approach due to complexity, but using a single motor for each pair of legs is certainly doable without sacrificing the ability to grip an asymmetrical object. Think about bicycle brakes which are able to grip the rip with two independent arms, using only a single pull. Hopefully the author will enter his project into an Instructables contest (or science fair) because I think it's a winner.
Back in the early 1960's I remember a wiz kid who's science fair entry was an electron microscope. Now that's a device that would really be out of the range of the average child and parent to build.
A simple robot like the tree climber could be built by someone with access to a machine shop or metal working shop in school. Putting together the control electronics and programming the micro processor might be a harder challenge unless the kid's parent or teacher worked in the field or there was access to a good robotic development kit.
I recall a citywide science fair, back in the early 1960's, where I exhibited a simple traffic control system with wireless capability to turn the intersection lights red to permit emergency vehicles the right of way. The model was made of cardboard and construction paper, painted flashlight bulbs and a box of relays I crudely put together along with a 27 MHz model airplane R/C receiver. The brightest student in my school was also there with an entry, a mockup of a heart lung machine with flowing liquid, which her parents and her science teacher collaborated on. They all snubbed me until the end of the day when the prize winners were announced. My entry won the only award for our school. The girl's project with all of her adult help was one of at least three heart lung machines entered in the fair. Mine was crude, hand made by the entrant and was original. The judges were quite astute.
The girl and her parents were eventually graceful enough to congradulate me. Her science teacher was not!
This robot could save cost & time for a tree surgeon to remove old limbs. The robot could carry a cord for a rope, even run it over a bad limb to be pulled down. It may also be good for tree-mounting personal radio antennas. I could see a local HAM club in the future buying one to lease to their members.
If climbing or scaling objects is the intended application, then a commercialized, proven version of this robot could have helped scale the Washington Monument to check for damage this week. If you look at it in that lights, you can envision tons of use cases.
This reminds me of some of the really neat projects out there that encourage kids to be explore robitics and other engeering related fields. The one I can think of off of the top of my head is the Lego League. A group of Girl Scouts from Gilbert started off building a robot to score some points on a competition table and ended up creating a prosthetic hand for a little 3 year old girl and going all the way to nationals and I believe they got to go to Washington D.C.
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