Soft Rotating Pneumatic Actuators

When we think of pneumatic actuators, we typically consider the standard varieties of pneumatic cylinder, capable of linear motion. These can be referred to as “hard” actuators, made of rigid components and capable of great accuracy and force delivery. However, “soft” actuators have their own complementary abilities – such as being able to handle more delicate tasks and being less likely to injure human operators when used in collaborative operations. The Whitesides Research Group at Harvard University has undertaken significant research in this field, and released a paper covering a novel type of soft pneumatic actuator.

The actuator consists of a series of soft, flexible sealed chambers which surround a wooden dowel in the center. By applying vacuum to these various chambers, the dowel in the center can be pulled into up to eight different positions. It’s a unique concept, and one we can imagine could have applications in various material processing scenarios.

The actuator was built by moulding elastomers around 3D printed components, so this is a build that could theoretically be tackled by the DIYer. The paper goes into great detail to quantify the performance of the actuator, and workshops several potential applications. Testing is done on a fluid delivery and stirring system, and a tethered robotic walker was built. The team uses the term cVAMS – cyclical vacuum actuated machine – to describe the actuator technology.

The world of soft robotics is a hot bed of development, and we look forward to further work in this field. It’s not just Harvard, either – we’ve seen interesting work from Yale and from the Hackaday community too!

 

Acetone Smoothing Results in Working Motor

Here’s something only ’90s kids will remember. In 1998, the Air Hogs Sky Shark, a free-flying model airplane powered by compressed air was released. This plane featured foam stabilizers, wings, a molded fuselage that served as a reservoir, and a novel engine powered by compressed air. The complete Sky Shark setup included an air pump. All you had to do was plug the plane into the pump, try to break the pressure gauge, and let the plane fly off into a tree or a neighbor’s rooftop. It’s still a relatively interesting mechanism, and although we’re not going to see compressed air drones anytime soon it’s still a cool toy.

Since [Tom Stanton] is working at the intersection of small-scale aeronautics and 3D printing, he thought he would take a swing at building his own 3D printed air motor. This is an interesting challenge — the engine needs to be air-tight, and it needs to produce some sort of usable power. Is a standard printer up to the task? Somewhat surprisingly, yes.

The design of [Tom]’s motor is more or less the same as what is found in the Air Hogs motor from twenty years ago. A piston is attached to a crank, which is attached to a flywheel, in this case a propeller. Above the cylinder, a ball valve keeps the air from rushing in. A spring is mounted to the top of the piston which pushes the ball out of the way, allowing air into the cylinder. At the bottom of the stroke, the ball closes the valve and air escapes out of the bottom of the cylinder. Simple stuff, really, but can it be printed?

Instead of the usual printer [Tom] uses for his builds, he pulled out an old delta slightly modified for higher quality prints. Really, this is just a 0.2 mm nozzle and a few tweaks to the print settings, but the air motor [Tom] designed came out pretty well and was smoothed to a fine finish with acetone.

After assembling the motor, [Tom] hooked it up to a soda bottle serving as a compressed air reservoir. The motor worked, although it’s doubtful a plane powered with this motor would fly for very long. You can check out [Tom]’s video below.

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This Drone Can Fly, Swim, and Explode….. Wait, What?

You’ve probably heard of micro-drones, perhaps even nano-drones, but there research institutions that shrink these machines down to the size of insects. Leading from the [Wiss Institute For Biologically Inspired Engineering] at Harvard University, a team of researchers have developed a miniscule robot that — after a quick dip — literally explodes out of the water.

To assist with the take off, RoboBee has four buoyant outriggers to keep it near the water’s surface as it uses electrolysis to brew oxyhydrogen in its gas chamber. Once enough of the combustible gas has accumulated — pushing the robot’s wings out of the water in the process– a sparker ignites the fuel, thrusting it into the air. As yet, the drone has difficulty remaining in the air after this aquatic takeoff, but we’re excited to see that change soon.

Looking like a cross between a water strider and a bee, the team suggest this latest version of the RoboBee series  — a previous iteration used electrostatic adhesion to stick to walls — could be used for search and rescue, environmental monitoring, and biological studies. The capacity to transition from aerial surveyor, to underwater explorer and back again would be incredibly useful, but in such a small package, it is troublesome at best. Hence the explosions.

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Pneumatic Origami

Odds are that if you’ve been to the beach or gone camping or somewhere in between, you are familiar with inflatable products like air mattresses. It’s nothing spectacular to see a rectangle inflate into a thicker, more comfortable rectangle, but what if your air mattress inflated into the shape of a crane?

We’ve seen similar ideas in quadcopters and robots using more mechanical means, but this is method uses air instead. To make this possible, the [Tangible Media Group] out of [MIT’s Media Lab] have developed aeroMorph — a program that allows the user to design inflatable constructs from paper, plastic or fabric with careful placement of a few folding joints.

These designs are exported and imprinted onto the medium by a cartesian coordinate robot using a heat-sealing attachment. Different channels allow the medium to fold in multiple directions depending on where the air is flowing, so this is a bit more complicated than, say, a bouncy castle. That, and it’s not often you see paper folding itself. Check it out!

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Custom Cut Pinwheel Makes a Useful HVAC Duct Flow Meter

Everyone is familiar with pinwheels, and few of us haven’t crafted one from a square of paper, a stick, and a pin. Pinwheels are pretty optimized from a design standpoint, and are so cheap and easy to build that putting a pinwheel to work as an HVAC duct flow meter seems like a great idea.

Great in theory, perhaps, but as [ItMightBeWorse] found out, a homemade pinwheel is far from an ideal anemometer. His experiments in air duct flow measurements, which previously delved into ultrasonic flow measurement, led him to try mechanical means. That calls for some kind of turbine producing a signal proportional to air flow, but a first attempt at using a computer fan with brushless DC motor failed when a gentle airflow couldn’t overcome the drag introduced by the rotor magnets. But a simple pinwheel, custom cut from patterns scaled down from a toy, proved to be just the thing. A reflective optosensor counts revolutions as the turbine spins in an HVAC duct, and with a little calibration the rig produces good results. The limitations are obvious: duct turbulence, flimsy construction, and poor bearings. But for a quick and dirty measurement, it’s not bad.

Looking for an outdoor anemometer rather than an HVAC flow meter? We’ve got one made from an old electric motor, or a crazy-accurate ultrasonic unit.

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Stealing Joules From An Aluminium-Air Battery

While batteries are cheap and readily obtainable today, sometimes it’s still fun to mess around with their less-common manifestations. Experimenting with a few configurations, Hackaday.io user [will.stevens] has assembled an aluminium-air battery and combined it with a joule thief to light an LED.

To build the air battery, soak an activated charcoal puck — from a water filter, for example — in salt-saturated water while you cut the base off an aluminium can. A circle of tissue paper — also saturated with the salt water — is pressed between the bare charcoal disk and the can, taking care not to rip the paper, and topped off with a penny and a bit of wire. Once clamped together, the reaction is able to power an LED via a simple joule thief.

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Measuring Air Flow with Ultrasonic Sensors

Measuring air flow in an HVAC duct can be a tricky business. Paddle wheel and turbine flow meters introduce not only resistance but maintenance issue due to accumulated dust and debris. Being able to measure ducted airflow cheaply and non-intrusively, like with this ultrasonic flow meter, could be a big deal for DIY projects and the trades in general.

The principle behind the sensor [ItMightBeWorse] is working on is nothing new. He discovered a paper from 2015 that describes the method that measures the change in time-of-flight of an ultrasonic pulse across a moving stream of air in a duct. It’s another one of those “Why didn’t I think of that?” things that makes perfect sense in theory, but takes some engineering to turn into a functional sensor. [ItMightBeWorse] is using readily available HC-SR04 sensor boards and has already done a proof-of-concept build. He’s getting real numbers back and getting close to a sensor that will go into an HVAC automation project. The video below shows his progress to date and hints at a follow-up video with more results soon.

Here’s wishing [ItMightBeWorse] the best of luck with his build. But if things go sideways, he might look to our post-mortem of a failed magnetic flow meter for inspiration.

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