A High Torque 3D Printed Harmonic Drive

May 24, 2021 by Danie Conradie 5 Comments

Actuators that are powerful, accurate, compact, and cheap are like unicorns. They don’t exist. Yet this is what [3DprintedLife] needed for a robotic camera arm, so he developed a custom 3D printed high torque strain wave gearbox to be powered by a cheap NEMA23 stepper motor.

Strain wave gears, otherwise known as harmonic drives, are not an uncommon topic here on Hackaday. The work by deforming a flexible toothed spline with a rotating elliptical part, which engages with the internal teeth of an outer spline. The outer spline has a few more teeth, causing the inner spline to rotate slowly compared to the input, achieving very high gear ratios. Usually, the flexible spline is quite long to allow it to flex at one end while still having a rigid mounting surface at the other end. [3DprintedLife] got around this by creating a separate rigid output spline, which also meshes with the flexible spline. Continue reading “A High Torque 3D Printed Harmonic Drive” →

Omnibot From The 80s Gets LED Matrix Eyes, Camera

May 18, 2021 by Donald Papp 8 Comments

[Ramin assadollahi] has been busy rebuilding and improving an Omnibot 5402, and the last piece of hardware he wanted to upgrade was some LED matrix eyes and a high quality Raspberry Pi camera for computer vision. An Omnibot was something most technical-minded youngsters remember drooling over in the 80s, and when [ramin] bought a couple of used units online, he went straight to the workbench to give the vintage machines some upgrades. After all, the Omnibot 5402 was pretty remarkable for its time, but is capable of much more with some modern hardware. One area that needed improvement was the eyes.

The eyes on the original Omnibot could light up, but that’s about all they were capable of. The first upgrade was installing two 8×8 LED matrix displays to form what [ramin] calls Minimal Expressive Eyes (MEE), powered by a Raspberry Pi. With the help of a 3D-printed adapter and some clever layout, the LED matrix displays fit behind the eye plate, maintaining the original look while opening loads of new output possibilities.

Adding a high quality Raspberry Pi camera with wide-angle lens was a bit more challenging and required and extra long camera ribbon connector, but with the lens nestled just below the eyes, the camera has a good view and isn’t particularly noticeable when the eyes are lit up. Having already upgraded the rest of the hardware, all that remains now is software work and we can’t wait to see the results.

Two short videos of the hardware are embedded below, be sure to give them a peek. And when you’re ready for more 80s-robot-upgrading-action, check out the Hero Jr.

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Actively Balancing A Robot With A Gyroscope

May 17, 2021 by Danie Conradie 9 Comments

Self-balancing robots are a common hacker project, but we don’t often see them using spinning gyroscopes to achieve that balance. Robot master [James Bruton] decided to build a robotic platform with active gyroscopic stabilization, starting from a simple proof of concept.

A gyroscope can balance, but cannot actively counteract external forces directly. However, if the gyroscope is tilted around an axis it will exert a force perpendicular to that axis of tilt, known as gyroscopic precession. By tilting the gyroscope with an actuator, and orienting the gyroscope correctly, gyroscopic precession can be used for stabilization. This is known as a control moment gyroscope. [James] demonstrated this with a 3D printed proof of concept, which is used as an IMU to measure the angle of tilt, and use a PID loop to correct the imbalance with a servo actuating the gyroscope.

His second platform used a pair of gyroscopes spinning in opposite directions to compensate for any unintended gyroscopic precession along another axis. A pair of roller skate wheels allow the entire platform to roll along. Due to a slight imbalance in the platform, [James] noticed that the gyroscopes will continue to creep in one direction, until reaching the end-stops and falling over. By adding a second software controller to keep track of how much the gyroscopes have to move to maintain balance, it can continuously calculate and update the balancing point. This prevents the gyroscopes from hitting the end stops.

Control moment gyroscopes are commonly used for attitude control on spacecraft, and to reduce the rolling motion of boats in waves. [James] has plans to combine a control moment gyroscope with the more conventional balancing method, to balance a robot on a single wheel.

We’ve seen a two wheeled RC cars use gyroscopes before, but without the active control part.
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3D Printed Tank Takes On The Elements

May 16, 2021 by Lewin Day 4 Comments

Commercially available radio control tanks are fun and all, but sometimes you’ve just got to build your own. [Let’s Print] did just that, whipping up a tank on his 3D printer before taking it out in the snow.

The tank is a fairly straightforward build, relying on a pair of brushed motors for propulsion, controlled by twin speed controllers hooked up to standard radio control hardware. Everything else is bespoke, however, from the 3D printed gearboxes, to the chassis and the rather aggressive-looking tracks. The pointed teeth of the latter leave deep indentations when the tank cruises around on mud, though weren’t quite enough to stop the little tank from getting high-centered in deep snow.

The build isn’t for the impatient, however. [Let’s Print] notes that the tracks alone took over 80 hours to run off in PETG, let alone the rest of the frame and gearboxes. However, we’re sure it was a great learning experience, and great fun to drive outside. Now the next step is surely to go bigger. Video after the break.

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Robotic Bartender Built With Industrial-Grade Hardware

May 15, 2021 by Lewin Day 12 Comments

Robotic bartenders are a popular project around these parts. If there’s one thing hackers love, after all, it’s automating tasks – as much for the challenge as for the actual time saved. This build from a group of [Teknic Servo] engineers is an impressive example of what can be done with some industrial-grade hardware.

The bartender is built as a demo project for the ClearCore controller, [Teknic’s] industrial-grade device capable of interfacing with a whole bunch of servomotors and sensors to get the job done. The controller is hooked up to a bunch of ClearPath servomotors that handle spinning the bottle carousel, muddling or stirring the beverage, or transporting the drinking glass through the machine. There’s also several interlocks to avoid the patron coming into contact with the bartender’s moving parts while it’s working, and a standard bar-style mixer dispenser actuated with solenoids to keep things simple. Drink selection and control is via a touch screen, with sliders for selecting preferences such as alcohol content and sweetness.

The bartender is certainly capable of producing a neat drink (pun intended), and serves as a great example of how easily a project can be put together with industrial-grade hardware. If you’ve got the budget, you might find using an industrial plug-and-play components quicker than assembling development boards, motor controller shields and other accessories on breakout boards. There’s always more than one way to get the job done, after all.

We’ve seen some great barbots over the years, from builds relying on robotic arms to those focused on ultimate speed. Video after the break.

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Random Robot Makes Random Art

May 14, 2021 by Bryan Cockfield 4 Comments

For the price of a toothbrush and a small motor with an offset weight, a bristlebot is essentially the cheapest robot that can be built. The motor shakes the toothbrush and the bristle pattern allows the robot to move, albeit in a completely random pattern. While this might not seem like a true robot that can interact with its environment in any meaningful way, [scanlime] shows just how versatile this robot – which appears to only move randomly – can actually be used to make art in non-random ways.

Instead of using a single bristlebot for the project, three of them are built into one 3D printed flexible case where each are offset by 120°, and which can hold a pen in the opening in the center. This allows them to have some control on the robot’s direction of movement. From there, custom software attempts to wrangle the randomness of the bristlebot to produce a given image. Of course, as a bristlebot it is easily subjected to the whims of its external environment such as the leveling of the table and even the small force exerted by the power/communications tether.

With some iterations of the design such as modifying the arms and control systems, she has an interesting art-producing robot that is fairly reliable for its inherently random movements. For those who want to give something like this a try, the code for running the robot and CAD files for 3D printing the parts are all available on the project’s GitHub page. If you’re looking for other bristlebot-style robots that do more than wander around a desktop, be sure to take a look at this line-following bristlebot too.

Thanks to [johnowhitaker] for the tip!

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Leap Motion Controls Hands With No Glove

May 8, 2021 by Al Williams No comments

It isn’t uncommon to see a robot hand-controlled with a glove to mimic a user’s motion. [All Parts Combined] has a different method. Using a Leap Motion controller, he can record hand motions with no glove and then play them back to the robot hand at will. You can see the project in the video, below.

The project seems straightforward enough, but apparently, the Leap documentation isn’t the best. Since he worked it out, though, you might find the code useful.

An 8266 runs everything, although you could probably get by with less. The Leap provides more data than the hand has servos, so there was a bit of algorithm development.

We picked up a few tips about building flexible fingers using heated vinyl tubing. Never know when that’s going to come in handy — no pun intended. The cardboard construction isn’t going to be pretty, but a glove cover works well. You could probably 3D print something, too.

The Unity app will drive the hand live or can playback one of the five recorded routines. You can see how the record and playback work on the video.

This reminded us of another robot hand project, this one 3D printed. We’ve seen more traditional robot arms moving with a Leap before, too. Continue reading “Leap Motion Controls Hands With No Glove” →