bend sensors

2 Articles

Budget-Friendly Bend Sensor Deforms With Precision

September 14, 2020 by 5 Comments

We’re pretty familiar with budget resistor-based bend sensors at this point, but this sensor is in a totally different class. Instead of relying on resistive elements, [Useok Jeong] and [Kyu-Jin Cho] devised a bend sensor that relies on geometric properties of the sensor itself. The result is a higher-fidelity measuring device made from a pretty widely available collection of stock parts.

We’ll admit, calling this device a bend sensor might be a bit of a stretch, so let’s dig into some of the operating principles. What we’re actually measuring is the accumulated angle, the sum of all the curvature deformations along the length of the sensing element. The sensor is made of 3 main pieces: an outer extension spring-based wire sheath; a flexible, tensioned inner wire core that’s fixed at one end; and a small displacement sensor that measures the length changes in the wire’s free end. The secret ingredient to making this setup work is a special property of the outer wire sheath or spring guide. Here, the spring guide actually resists being compressed while being bent.  Because the inner radius of the bend remains a constant length, the center wire core is forced to elongate. With the excess wire spooled up at the sensor base, we simply measure how much we collected, apply some math, and get a resulting angle! What’s more, the folks behind this trick also demonstrate that the length and angle relationship is linear with an R-square of 0.9969.

One of the best parts about this sensor is how reproducible it seems from from a modest collection of stock parts. Spring guide (aka: extension spring) is available from McMaster-Carr and DR Templeman, and that flexible core might be readily substituted with some wire rope.

It’s not everyday that new topologies for bend sensors pop into the world, let alone linear ones. To learn more, the folks behind the project have kindly made their research paper open access for your afternoon reading enjoyment. (Bring scratch paper!) Finally, if you’re looking for other bend-related sensors, have a look at this multi-bend measurement setup.

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Hackaday Prize Entry: Hands|On Gloves Speaks Sign Language

October 11, 2016 by 7 Comments

The Hands|On glove looks like it’s a PowerGlove replacement, but it’s a lot more and a lot better. (Which is not to say that the Power Glove wasn’t cool. It was bad.) And it has to be — the task that it’s tackling isn’t playing stripped-down video games, but instead reading out loud the user’s sign-language gestures so that people who don’t understand sign can understand those who do.

The glove needs a lot of sensor data to accurately interpret the user’s gestures, and the Hands|On doesn’t disappoint. Multiple flex sensors are attached to each finger, so that the glove can tell which joints are bent. Some fingers have capacitive touch pads on them so that the glove can know when two fingers are touching each other, which is important in the US sign alphabet. Finally, the glove has a nine degree-of-freedom inertial measurement unit (IMU) so that it can keep track of pitch, yaw, and roll as well as the hand’s orientation.

In short, the glove takes in a lot of data. This data is cleaned up and analyzed in a Teensy 3.2 board, and sent off over Bluetooth to its final destination. There’s a lot of work done (and some still to be done) on the software side as well. Have a read through the project’s report (PDF) if you’re interested in support vector machines for sign classification.

Sign language is most deaf folks’ native language, and it’s a shame that the hearing community can’t understand it directly. Breaking down that barrier is a great idea, and it makes a great entry in the Hackaday Prize!

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