Robotic Gripper From A Squishy Ball

May 4, 2021 by Danie Conradie 11 Comments

Soft robotic grippers have some interesting use cases, but the industrial options are not cheap. [James Bruton] was fascinated by the $4000 “bean bag” gripper from Empire Robotics, so he decided to build his own.

The gripper is just a flexible rubber membrane filled with small beads. When it is pushed over a object and the air is sucked out, it holds all the beads together, molded to the shape of the object. For his version [James] used a soft rubber ball filled with BBs. To create a vacuum, he connected a large 200cc syringe to the ball via a hose, and actuated it with a high torque servo.

It worked well for small, light objects but failed on heavier, smooth objects with no edges to grip onto. This could possibly be improved if the size and weight of the beads/BBs are reduced.

For some more soft robotics, check out this soft 3D printed hand, and the flexible electrically driven actuators. Continue reading “Robotic Gripper From A Squishy Ball” →

Guitar Hero Robot Actually Shreds

May 3, 2021 by Matthew Carlson 12 Comments

Once a popular craze, most of the public has sold or stashed away their plastic video game instruments and forgotten the likes of Guitar Hero and Rockband. Having never been quite satisfied with his scores, [Nick O’Hara] set out to create a robot that could play a Guitar Hero controller. It would be easy enough to use transistors to actuate the buttons or even just a Teensy to emulate a controller and have it play the perfect game, but [Nick] wanted to replicate what it was really like to play. So after burning out a fair number of solenoids (driving them over spec) and learning on his feet, [Nick] slowly began to dial in his robot, Jon Bot Jovi.

The brains of the bot are a Raspberry Pi running some OpenCV-based code that identifies blobs of different colors. The video feed comes from a PS2 via an HDMI capture card. Solenoids are driven via an 8 channel driver board, controlled by the Pi. While it missed a few notes here and there, we loved seeing the strumming solenoid whammy rapidly on the strummer. All in all, it’s a great project, and we love the design of the robot. Whether played by a robot, turned into a synthesizer, or recreated from toy pianos and mechanical keyboards, Guitar Hero controllers offer many hacking opportunities.

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Apple-Picking Robot Stems From Labor Shortage

May 1, 2021 by Kristina Panos 35 Comments

Among all the job-related problems wrought by the pandemic, here is another one that comes as the result of people generally staying home: there are hardly any backpackers to do traditional transient backpacker jobs like picking apples. Researchers at Monash University’s Department of Mechanical and Aerospace engineering found a way to fill in the gap by building a pneumatic robot arm that can harvest an apple every seven seconds at top speed.

A suite of cameras and algorithms look for fruit amongst the foliage and carefully remove it by gripping it gently and twisting, much like a human would. In order to do this, the robot must consider the shape of the fruit, the way it’s hanging, and where to separate it from the tree while keeping damage to a minimum. A suction system helps pull the apple into the soft, four-fingered grip and then the arm twists and turns to deposit the apple into the bin.

There are a lot of upsides to this robot, including the fact that it works in any lighting and weather conditions and can ID an apple in less than 200 milliseconds. The only problem is that this operation results in the occasional missing stem — a cosmetic problem that sounds nit-picky, but would definitely prevent some stores from buying the fruit. Well, that, and there only seems to be one of these robots so far.

There are two videos after the break — a short one that gives you the gist, and a much longer one that offers a view of the suction cup, which emerges from the middle of the fingers like a xenomorph’s little mouth.

Some readers may be wondering why apples are still picked individually when shaking harvesters exists. “Shake-and-catch” tends to bruise apples, making them undesirable for produce sellers, however, apples destined for juicing have no issue with being handled roughly by the harvesters as shown in this fascinating harvest video. Robot grippers are gentle and we’ve seen all shapes and sizes that are suited to a particular need. When the needs are more general, rollers or squishy spheres might be the answer.

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Disney Imagineering’s “Project Kiwi” Bears Groot

April 26, 2021 by Zach Zeman 31 Comments

Some days, we might be forgiven for believing Boston Dynamics has cornered the market on walking robots. They (and other players) are making incredible progress in their field, but three years ago Disney, trying to create autonomous, free-walking robotic actors for some of their more diminutive film characters, found none of the existing platforms were appropriate. So they set their Imagineering department to work on “Project Kiwi”, and we are now seeing the fruits of those efforts.

Research on bipedal robots has amassed over the years, and as the saying goes, if these Imagineers saw further it was by standing on the shoulders of larger robotic platforms. However, the Project Kiwi designers have made a laundry list of innovations in their process of miniaturization, from the “marrow conduit” cooling system which forces air through hollow bones, to gearing that allows actuators to share motors even across joints. The electronics are distributed around the skeleton on individual PCBs with ribbon flex cables to reduce wiring, and almost every component is custom fabricated to meet the complex size and weight requirements.

Even in this early prototype, Disney’s roots in life-like animatronics are evident. Groot’s movements are emotive, if a bit careful, and software can express a variety of personalities through his gaits and postures. The eyes and face are as expressive as we’ve come to expect (though a keen eye for seams puts off some definite Westworld vibes). Reportedly, this version can handle gentle shoves and contact, but we do spot a safety cable still attached to the head. So there’s probably some way to go before we’ll see this interacting with the general public in a park.

Disney’s Imagineering department has been doing some amazing work with robotics and they continue to make significant innovations in the more traditional fields of animatronics. It certainly looks like one of the coolest places to work right now, and now we’re itching to build our own bipedal friends to play with.

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Sanity Check Your Engines With This Dynamometer

April 14, 2021 by Sonya Vasquez 2 Comments

As you get ready to pop the hood of your RC car to drop in a motor upgrade, have you ever wondered how much torque you’re getting from these small devices? Sure, we might just look up the motor specs, but why trust the manufacturer with such matters that you could otherwise measure yourself? [JohnnyQ90] did just that, putting together an at home-rig built almost from a stockpile of off-the-shelf parts.

To dig into the details, [JohnnyQ90] has built himself a Prony Brake Dynamometer. These devices are setup with the motor shaft loosely attached to a lever arm that can push down on a force-measuring device like a scale. With our lever attached, we then power up our motor. By gradually increasing the “snugness” of the motor shaft, we introduce sliding friction that “fights” the motor, and the result is that, at equilibrium, the measured torque is the maximum amount possible for the given speed. Keep turning up that friction and we can stall the motor completely, giving us a measurement of our motor’s stall torque.

Arming yourself with a build like this one can give us a way to check the manufacturer’s ratings against our own, or even get ratings for those “mystery motors” that we pulled out the dumpster. And [JohnnyQ90’s] build is a great reminder on how we can leverage a bit of physics and and a handful of home goods to get some meaningful data.

But it turns out that Prony Brake Dynamometers aren’t the only way of measuring motor torque. For a disc-brake inspired, have a look at this final project. And if you’re looking to go bigger, put two motors head-to-head to with [Jeremy Felding’s] larger scale build.

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Scratch-Built Robot Arm Looks Like Something Off The Factory Floor

April 10, 2021 by Dan Maloney 13 Comments

[Jeremy Fielding] is rightly impressed with the power and precision of industrial robot arms. The big arms that you see welding cars on assembly lines and the like are engineering feats in their own right, which is why his leap into scratch-building one in the home shop promises to be quite an adventure, and one we’re eager to follow.

From the look of the video below, [Jeremy]’s arm is already substantially complete, so it seems like he’ll be releasing videos that detail how he got to the point where this impressively large and powerful arm took over so much of his shop. He’s not fooling around here — this is a seven-axis articulated arm built from aluminum and powered by AC servos. [Jeremy] allows that some of the structural parts are still 3D-printed prototypes that he’s using to finalize the design before committing to cutting metal, a wise move as he notes that most of the metalworking skills he needs to complete the build are still fairly new to him. It still looks amazing, and we’re looking forward to the rest of the series to see how he got to this point.

We always appreciate [Jeremy]’s enthusiasm and presentation style, and we generally learn a lot from his videos. Whether it’s a CNC table saw, a homebrew dynamometer, or supersonically melting baseballs, his videos are always great to watch.

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Harmonic Drive Uses Compliant Mechanism To Slim Down

April 7, 2021 by Dan Maloney 15 Comments

[Levi Janssen] has a secret: he doesn’t like harmonic drives. But rather than abandon the torque-amplifying transmission completely, he decided to see about improving them using 3D-printed compliant mechanisms.

For the uninitiated, harmonic drives, also known as strain-wave gears, are a compact, high-torque gearbox that has become popular with “robotic dog” makers and other roboticists. The idea is to have a rigid, internally-toothed outer ring nested around an externally-toothed, flexible cup. A wave generator rotates within the inside cup, stretching it so that it meshes with the outer ring. The two gears differ by only a couple of teeth, meaning that very high gear ratios can be achieved, which makes them great for the joints of robot legs.

[Levi]’s problem with the harmonic drive is that due to the depth of the flexible spline cup, compactness is not among its virtues. His idea is to couple the flex spline to the output of the drive through a flat spring, one that allows flexion as the wave generator rotates but transmits torque efficiently. The entire prototype is 3D-printed, except for the wave generator bearings and stepper motor, and put to the test.

As the video below shows after the excellent introduction to harmonic drives, the concept works, but it’s not without its limitations. Even lightly loaded, the drive made some unpleasant crunching sounds as the PLA springs gave out. We could easily see that being replaced with, say, a steel spring, either machined or cut on a water-jet machine. That might solve the most obvious problem and make [Levi]’s dream of a compact harmonic drive a reality. Of course, we have seen pretty compact strain-wave gears before.

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