I spent a good chunk of Saturday afternoon hanging out at the Homebrew Robotics Club booth at Maker Faire Bay area. They have a ton of really interesting robot builds on display and I just loved hearing about what went into these two in particular.
It’s obvious where BugBot gets its name. The six-legged walker is the creation of [Mark Johnston] who built the beast in a time where components for robots were much harder to come by. Each leg is driven by a very thin strand of muscle wire which contracts when high voltage is run through it. One of the really tricky parts of the build was finding a way to attach this wire. It has a very low melting point, so trying to solder it usually results in melting right through. His technique is to wrap the wire around the leg itself, then slide a small bit of brass tubing over it and make a crimp connection.
PIC microcontroller and muscle wire connections visible in this closeup
The underside of BugBot is impressive too! Two hoops normally hold the battery which is not shown here
At the heart of the little bug is a PIC microcontroller that is point-to-point soldered to the rest of the components. This only caused real problems once, when Mark somehow bricked the chip and had to replace it. Look close and you’ll see there’s a lot of fiddly bits to work around to pull that off. As I said, robot building was more difficult before the explosion of components and breakout modules hit the scene. The wireless control components on this were actually salvaged out of children’s RC toys. They’re not great by any stretch of the imagination, but it was the best source at the time and it works! You can find a demo of the robot embedded after the jump.
An Android robot was on display, but of course, I was most interested in seeing what was beneath the skin. In the image above you can see the mask sitting to the left of the “Pat” skeleton. Ralph Campbell has been working on this build, and plans to incorporate interactive features like facial recognition and gesture recognition to affect the gaze of the robot.
Overview of “Pat” without skin
Hoops are coat hangers soldered together
Inside each of the ping pong ball eyes is a Raspberry Pi camera (actually the Adafruit Spy Camera because of its small board size). Ralph has a separate demonstration for facial recognition that he’s in the process of incorporating. But for me, it was the mechanical design of the bot that I find fascinating.
The structure of the skull is coat hanger lashed and soldered together using magnet wires. The eyes move thanks to a clever frame made out of paper clips. The servos to the side of each eye move the gaze up and down, while a servo beneath the eye takes care of left and right. A wooden match stick performs double duty — keeping the camera in place as the pupil of the eye, and allowing it to pivot along the paperclip track of the vertical actuator. It’s as simple as it can be and I find it quite clever!
Did you know that under the right conditions, nylon can be used as a type of artificial muscle? We certainly didn’t until we came across [Brandon T. Wood]’s Material Linear-Actuator for Robotics entry for the 2018 Hackaday Prize.
When [Brandon] first learned about Nylon Linear Material Actuators (NLMAs), he became determined to find a repeatable and practical method of making and experimenting with them. This is how it works: hyper-wound coils of nylon, when heated, will contract along their length while expanding in width. Upon cooling, they return to their original shape.
[Brandon] has been busy mainly with the kind of work that is important but not very flashy: finding accessible methods to reliably create strands of artificial nylon muscles cheaply and reliably. His current method uses a jig to wind nylon fishing line until it coils upon itself tightly, then twist a length of nichrome wire around the outside to act as a heater. Using this method, the coils can be electrically controlled. [Brandon] is currently experimenting with creating bundles of individual nylon coils to act all together as one big muscle, because while one wire isn’t particularly strong, a bundle could be quite another story. It’s definitely unusual and is doing a lot of work to turn a known phenomenon into something hackable, which makes it lovely to see in this year’s Hackaday Prize.
There are individuals who push tools, materials, and craftsmanship to the limit in the world of micro RC aircraft, and [Martin Newell] gives some insight into the kind of work that goes into making something like a 1:96 scale P-51 Mustang from scratch. The tiny plane is 100% flyable. It even includes working navigation lights and flashing cannons (both done with 0402 LEDs) and functional, retractable landing gear. It weighs an incredible 2.9 grams. Apart from the battery, everything in the plane was built or assembled from scratch. A video is embedded below.
But if you had all of the parts on hand (a highly liquid MIDI-driven relay board that connects straight up to a soundcard, some muscle wire, tape, and a whiteboard pen, naturally) we’re pretty sure that you would. You can watch the dancing pen in a video below the break.
The project is really about documenting the properties of [serdef]’s muscle wire, and he found that it doesn’t really contract enough with a short piece to get the desired effect. So he added more wire. We’ve always meant to get around to playing with muscle wire, and we were surprised by how quickly it reacted to changing the voltage in [serdef]’s second video.
It’s hard to resist the temptation to tear apart a shiny new gadget, but fortunately, iFixIt often does it for us. This helps to keep our credit cards safe, and reveal the inner workings of new stuff. That is definitely the case with the Microsoft Surface Book teardown that they have just published. Apart from revealing that it is pretty much impossible to repair yourself, the teardown reveals the mechanism for the innovative hinge and lock mechanism. The lock that keeps the tablet part in place when in laptop mode is held in place by a spring, with the mechanism being unlocked by a piece of muscle wire.
We are no strangers to muscle wire (AKA Nitinol wire or Shape Metal Alloy, as it is sometimes called) here: we have posted on its use in making strange robots, robotic worms and walls that breathe. Whatever you call it, it is fun stuff. It is normally a flexible wire, but when you apply a voltage, it heats up and contracts, much like the muscles in your body. Remove the voltage, and the wire cools and reverts to its former shape. In the Microsoft Surface Book, a single loop of this wire is used to retract the lock mechanism, releasing the tablet part.
Unfortunately, the teardown doesn’t go into much detail on how the impressive hinge of the Surface Book works. We would like to see more detail on how Microsoft engineered this into the small space that it occupies. The Verge offered some details in a post at launch, but not much in the way of specifics beyond calling it an “articulated hinge”.
UPDATE: This post was edited to clarify the way that muscle wire works. 11/4/15.
This earthworm robot comes to us from researchers at the Massachusetts Institute of Technology. It is made up of mostly soft parts and manages to inch its way along the ground.
The robot’s “skin” is made from a tube of polymer mesh that will hold up to an awful lot of bending and stretching. As with its biological namesake, locomotion is facilitated by circular muscles. In this case muscle wire, when stimulated with electricity, contracts around the mesh casing. By coordinating these contractions the robot is able to inch its way along.
But it’s not just the method of travel that makes this research project interesting. The bot is also extremely resistant to damage. The video after the break shows the device withstanding several whacks from a mallet and being stepped on by the team that created it.
Behold the Dynamic Autonomous Sprawled Hexapod (DASH). The video above was presented at the 2009 International Conference on Intelligent Robots and Systems. In it we see the toils of a team from UC Berkeley’s Biomimetic Millisystems Lab. They’ve developed a robot propulsion system that mimics some of the best aspects of cockroaches and other insect bodies: speed, economy of motion, ability to survive large falls without damage, and the capability to traverse obstacles. Let’s take a look at how they put this together after the break. Continue reading “DASH: clever construction and resilience in robotics”→