Stepper Motor Robot Arm Has Smooth Moves

January 22, 2018 by Steven Dufresne 17 Comments

[Tobias Kuhn] had watched a YouTube video about a robot arm which used servo motors, and wanted to try making one himself. But he found it hard to get slow or smooth movements out of the servos. Even removing the microcontroller and trying to work with the servo’s driver-IC and potentiometer from an Arduino Nano didn’t get him satisfaction.

Then he found the very affordable 28BYJ-48 stepper motor. After some experimenting, he came up with a smooth moving robot arm with four steppers controlled from an Arduino Mega and A4988 stepper motor drivers. Rather than write a bunch of stepper motor code himself, he installed and ran a four-axis fork of grbl on the Arduino, turning it into a stepper motor controller. One minor hitch was that the A4988 motor drivers are for bipolar stepper motors but 28BYJ-48 steppers are unipolar. Luckily he knew of a very simple hack which our [Brian Benchoff] wrote about for turning a unipolar motor into a bipolar motor.

To tell the robot arm what to do, he built a replica arm with potentiometers in place of the stepper motors. As he manipulates the replica, the values of the potentiometers are read by a Raspberry Pi and some custom Python code which sends the appropriate G-code to the Arduino/grbl controlled robot arm. There’s a bit of a lag but when he moves the replica arm, the robot arm does the same move. See it in action in the video below.

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Big Trak Gets A New Brain

January 18, 2018 by Al Williams 30 Comments

If you were a kid in the 1980s you might have been lucky enough to score a Big Trak — a robotic toy you could program using a membrane keyboard to do 16 different motions. [Howard] has one, but not wanting to live with a 16-step program, he gave it a brain transplant with an Arduino and brought it on [RetroManCave’s] video blog and you can see that below.

If you want to duplicate the feat and your mom already cleaned your room to make it a craft shop, you can score one on eBay or there’s even a new replica version available, although it isn’t inexpensive. The code you need is on GitHub.

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Rolling Robot With Two Motors, But None Are On The Wheels

January 12, 2018 by Donald Papp 4 Comments

This unusual 3D printed Rolling Robot by [ebaera] uses two tiny hobby servos for locomotion in an unexpected way. The motors drive the front wheel only indirectly, by moving two articulated arms in a reach-and-retract motion similar to a breaststroke. The arms are joined together at the front, where a ratcheting wheel rests underneath. When the arms extend, the wheel rolls forward freely. When the arms retract, the wheel’s ratchet locks and the rest of the body is pulled forward. It looks as though extending one arm more than the other provides for rudimentary steering.

The parts are all 3D printed but some of them look as though they might be a challenge to print well due to the number of small pieces and overhangs. A short video (embedded below) demonstrates how it all works together; the action starts about 25 seconds in.

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Robotic Drive Train Is Nearly All 3D Printed

January 7, 2018 by Al Williams 2 Comments

There are lots of ways to move a robot ranging from wheels, treads, legs, and even propellers through air or water. Once you decide on locomotion, you also have to decide on the configuration. One possible way to use wheels is with a swerve drive — a drive with independent motors and steering on each wheel. Prolific designer [LoboCNC] has a new version of his swerve drive on Thingiverse. The interesting thing is that it’s nearly all 3D printed.

You do need a few metal parts, a belt, two motors, and — no kidding — airsoft BBs, used as bearings. There are 3 parts you have to fabricate, which could take some work on a lathe, so it isn’t completely 3D printed.

[LoboCNC] points out that the assembly is lightweight and is not made for heavy robots. Apparently, though, his idea of lightweight is no more than 20 pounds per wheel, so that’s still pretty large in our book. The two motors allow for one motor to provide drive rotation while the other one — which includes an encoder — to steer. Of course, the software has to account for the effect of steering each wheel separately, but that’s another problem.

This robotic drivetrain is just thing for a car-like robot. If you are a little lonesome you could always print out ASPIR, instead. Or if you want an exotic 3D printed way to move things, you might get some inspiration from Zizzy. If you want a swerve drive that doesn’t require any machining or 3D printing, you might enjoy the video from another FIRST team, below.

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See This Slick RC Strandbeest Zip Around

January 3, 2018 by Donald Papp 8 Comments

Bevel gears used to mount motors vertically.

Theo Jansen’s Strandbeest design is a favorite and for good reason; the gliding gait is mesmerizing and this RC version by [tosjduenfs] is wonderful to behold. Back in 2015 the project first appeared on Thingiverse, and was quietly updated last year with a zip file containing the full assembly details.

All Strandbeest projects — especially steerable ones — are notable because building one is never a matter of simply scaling parts up or down. For one thing, the classic Strandbeest design doesn’t provide any means of steering. Also, while motorizing the system is simple in concept it’s less so in practice; there’s no obvious or convenient spot to actually mount a motor in a Strandbeest. In this project bevel gears are used to mount the motors vertically in a central area, and the left and right sides are driven independently like a tank. A motor driver that accepts RC signals allows the use of an off the shelf RC transmitter and receiver to control the unit. There is a wonderful video of the machine zipping around smoothly, embedded below.

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Remember When Scratch-Built Robots Were Hard?

January 2, 2018 by Mike Szczys 10 Comments

Even simple robots used to require quite a bit of effort to pull together. This example shows how far we’ve come with the tools and techniques that make things move and interact. It’s a 3D printed rover controlled by the touchscreen on your phone. This achieves the most basic building block of wheeled robotics, and the process is easy on you and your pocketbook.

We just can’t stop loving the projects [Greg Zumwalt], aka[gzumwalt], is turning out. We just saw his air-powered airplane engine and now this little rover perks our ears up. The design uses the familiar trick of two powered wheels with a ball bearing to avoid problems with differential turning. But the simplicity is all in the implementation.

This bot is 3D printed using eight very simple pieces: four gears, two axles, a cap and a single tray to mount everything. The cap captures the ball bearing which pokes out a hole in the bottom of the tray to form an omnidirectional wheel. Two 9G servos modified for continuous rotation. The mating teeth of the gears are found on the wheel sections which have grooves for neoprene O-rings to provide traction. The entire thing is driven by an ESP8266 in the form of an Adafruit Feather Huzzah. This is programmed using the Arduino IDE and your phone can connect directly or through a WiFi router.

We’re not crazy, right? Robots didn’t used to be this easy to pull together? This goes for the power of 3D printing versus traditional basement fabrication methods, but in the availability of powerful yet inexpensive embedded systems and the available tools and libraries to program them. Kudos to you [Greg] for showing us how great the currently available building blocks are in the hands of anyone who wants to channel their engineering creativity. He certainly has… this chassis ultimately powers Santa’s sleigh.

Need a bigger printing challenge? Here’s a 3D printed rover that goes all-in with the suspension system.

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How The Hero Droid BB-8 Rolls

January 1, 2018 by Roger Cheng 10 Comments

By now we’ve come to expect a bountiful harvest of licensed merchandise to follow every Star Wars film. This year’s crop included many flavors of BB-8 so every fan can find something to suit their taste. At the top of this food chain is a mobile interactive “Hero Droid BB-8”. For those who want to see how it works, [TheMikeSenna] cracked open his unit to feed our curiosity.

Also called “Spin Master BB-8” for the manufacturer, this toy is impressively sophisticated for its price point. The video surveyed the mechanical components inside the ball. Showing how the droid travels, and how the head articulates.

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