Slipping Sheets Map Multiple Bends In This Ingenious Flex Sensor

June 26, 2020 by 23 Comments

When thoughts turn to measuring the degree to which something bends, it’s pretty likely that strain gauges or some kind of encoders on a linkage come to mind. Things could be much simpler in the world of flex measurement, though, if [Fereshteh Shahmiri] and [Paul H. Dietz]’s capacitive multi-bend flex sensor catches on.

This is one of those ideas that seems so obvious that you don’t know why it hasn’t been tried before. The basic idea is to leverage the geometry of layered materials that slip past each other when bent. Think of the way the pages of a hardbound book feather out when you open it, and you’ll get the idea. In the case of the ShArc (“Shift Arc”) sensor, the front and back covers of the book are flexible PCBs with a series of overlapping pads. Between these PCBs are a number of plain polyimide spacer strips. All the strips of the sensor are anchored at one end, and everything is held together with an elastic sleeve. As the ShArc is bent, the positions of the electrodes on the top and bottom layers shift relative to each other, changing the capacitance across them. From the capacitance measurements and the known position of each pad, a microcontroller can easily calculate the bend radius at each point and infer the curvature of the whole strip.

The video below shows how the ShArc works, as well as several applications for the technology. The obvious use as a flex sensor for the human hand is most impressive — it could vastly simplify [Will Cogley]’s biomimetic hand controller — but such sensors could be put to work in any system that bends. And as a bonus, it looks pretty simple to build one at home.

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A Better Motor For Chickenwalkers

June 24, 2019 by 27 Comments

The last decade or so has seen remarkable advances in motor technology for robotics and hobby applications. We’re no longer stuck with crappy brushed motors, and now we have fancy (and cheap!) stepper motors, brushless motors for drones, and servo motors. This has led to some incredible achievements; drones are only barely possible with brushed motors, and you can’t build a robot without encoders.

For his entry into the Hackaday Prize, [Gabrael Levine] is taking on one of the hardest robotics challenges around: the bipedal robot. It’s a chickenwalker, or an AT-ST; either way, you need a lot of power in a very small space, and that’s where the OpenTorque Actuator comes in. It’s a quasi-direct-drive motor that was originally pioneered by the MIT Biomimetics Lab.

The key feature of the OpenTorque Actuator is using a big brushless motor, a rotation encoder, and a small, 8:1 planetary gear set. This allows the motor to be backdrivable, capable of force-sensing and open-loop control, and because this actuator is 3D printed, it’s really cheap to produce.

But a motor without a chassis is nothing, and that’s where the Blackbird Bipedal Robot comes in. In keeping with best practices of robotic design, the kinematics are first being tested in simulation, with the mechanical build happening in parallel. That means there’s some great videos of this chickenwalker strutting around (available below), and so far, everything looks great. This bipedal robot can turn, walk, yaw, and work is continuing on the efforts to get this bird-legged bot to stand still.

Interstellar 8-Track: The Not-So-Low-Tech Data Recorders Of Voyager

November 29, 2018 by 42 Comments

On the outside chance that we ever encounter a space probe from an alien civilization, the degree to which the world will change cannot be overestimated. Not only will it prove that we’re not alone, or more likely weren’t, depending on how long said probe has been traveling through space, but we’ll have a bonanza of super-cool new technology to analyze. Just think of the fancy alloys, the advanced biomimetic thingamajigs, the poly-godknowswhat composites. We’ll take a huge leap forward by mimicking the alien technology; the mind boggles.

Sadly, we won’t be returning the favor. If aliens ever snag one of our interstellar envoys, like one of the Voyager spacecraft, they’ll see that we sent them some really old school stuff. While one team of alien researchers will be puzzling over why we’d encode images on a phonograph record, another team will be tearing apart – an 8-track tape recorder?

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Mechatronic Hand Mimics Human Anatomy To Achieve Dexterity

October 18, 2018 by 8 Comments

Behold the wondrous complexity of the human hand. Twenty-seven bones working in concert with muscles, tendons, and ligaments extending up the forearm to produce a range of motions that gave us everything from stone tools to symphonies. Our hands are what we use to interface with the physical world on a fine level, and it’s understandable that we’d want mechanical versions of ourselves to include hands that were similarly dexterous.

That’s a tall order to fill, but this biomimetic mechatronic hand is a pretty impressive step in that direction. It’s [Will Cogley]’s third-year university design project, which he summarizes in the first video below. There are two parts to this project; the mechanical hand itself and the motion-capture glove to control it, both of which we find equally fascinating. The control glove is covered with 3D-printed sensors for each joint in the hand. He uses SMD potentiometers to measure joint angles, with some difficulty due to breakage of the solder joints; perhaps he could solve that with finer wires and better strain relief.

The hand that the glove controls is a marvel of design, like something on the end of a Hollywood android’s arm. Each finger joint is operated by a servo in the forearm pulling on cables; the joints are returned to the neutral position by springs. The hand is capable of multiple grip styles and responds fairly well to the control glove inputs, although there is some jitter in the sensors for some joints.

The second video below gives a much more detailed overview of the project and shows how [Will]’s design has evolved and where it’s going. Anthropomorphic hands are far from rare projects hereabouts, but we’d say this one has a lot going for it.

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Soft Robotic Jellyfish Get Pumped In The Atlantic

October 6, 2018 by 5 Comments

In a recent paper in Bioinspiration & Biomimetics, researchers at Florida Atlantic University describe the process of building and testing five free-swimming soft robotic jellyfish. The paper contains build details and data on how three different variables – tentacle stiffness, stroke frequency, and stroke amplitude – affect the swimming characteristics of each bot. For a more in-depth build log, we found the original masters thesis by Jennifer Frame to be very thorough, including processes, schematics, parts lists, and even some Arduino code.

Though a landlubber may say the robots look more like a stumpy octopus than a jellyfish, according to the paper the shape is actually most similar to a juvenile “ephyra stage” moon jellyfish, with 8 short tentacles radiating from a central body. The flexible tentacles are made of a silicon rubber material from Smooth-On, and were cast in 3D printed molds. Inside the waterproof main body is a Teensy 3.2 microcontroller, some flash memory, a nine-axis IMU, a temperature sensor, and a 9 V battery.

There are two flexible resistors embedded in the body to measure tentacle flex, and the actual flexing is done by pumping seawater through open circuit hydraulic channels cast into the tentacles. Two 3 V mini pumps are sufficient for pumping, and the open circuit means that when the pumps turn off, the tentacles bleed off any remaining pressure and quickly snap back to their “neutral” position without the use of complicated valves.

Another simple feature is two hall effect sensors that were mounted in the body to enable waterproof “wireless communication” with the microcontroller. The wireless protocol of choice: manually waving magnets over the sensors to switch the robot between a few predefined operating modes.

There’s a soothing, atmospheric video after the break, where you can see the robots in action off the coast of Florida.

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Researchers Squeeze Out A New Breed Of Robot Locomotion

September 30, 2017 by 24 Comments

Researchers have been playing around with various oddball forms of robot locomotion; surely, we’ve seen it all, haven’t we? Not so! Lucky for us, [researchers at Stanford] are now showing us a new way for robots to literally extrude themselves from point A to point B.

This robot’s particular motion for mechanism involves unwinding itself inside out. From a stationary base, a reel caches meters of the robot’s uninflated polyethylene body, which it deploys by pressurizing. Researchers can make full 3D turns by varying the amount of inflated air in outer control chambers. What’s more, they can place end effectors or even payloads at the tip of the growing end with their position held in place by a cable.

As we can imagine, any robot that can squeeze its way up to 72 meters long can have dozens of applications, and the folks at Stanford have explored a host of nooks and crannies of this space. Along the way, they deploy complex antenna shapes into the air, deliver small payloads, extinguish fires, and squeeze through all sorts of uninviting places such as flytraps and even a bed of nails. We’ve placed a video below the break, but have a look at Ars Technica’s full video suite to get a sense of the sheer variety of applications that they imparted upon their new creation.

Biomimetics tends to get us to cry “gecko feet” or “snake robots” without thinking too hard. But these forms of locomotion that come to mind all seem to derive from the animal kingdom. One key element of this soft robot is that its stationary base and vine-like locomotion both have its roots in the plant kingdom. It’s a testament to just how unexplored this realm may be, and that researchers and robots will continue to develop new ways of artificially “getting around” for years to come.

Thanks for the tip, [Jacob!]

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I’m BatBot

February 3, 2017 by 10 Comments

How would you like a bat bot for your next pet drone? Researchers from the University of Illinois at Urbana-Champaign’s Coordinated Science Laboratory and from the California Institute of Technology, created a bat drone. This is not your regular drone; it’s not a styrofoam, bat-shaped, four-propeller kind of drone. It’s a drone that mimics not only the shape but the movement of the bats wings to achieve flight.

The biomimetic robotic platform, dubbed Bat Bot B2, is an autonomous flying robot. The wing mechanics are controlled by a brushless DC motor for the wing flapping along with four wings actuators to provide linear motion that allows the wings to further change shape in flight. The wings are made of a 56-micron, silicone-based membrane (thinner than an average condom), which for sure helps with their elasticity as well as reducing overall weight, which is only 93 grams.

The bat has only made twenty flights so far, ranging up to 30 meters with some rough landings. It’s not much yet, but the prototype looks pretty slick. We covered another bat bot back in 2012 but the original information is no longer available, and we don’t know what happened to that project. There was also no video. In contrast, you can watch Bat Bot B2 glide.

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