TrackRobot Sports Welded Steel, Not Plastic

Don’t let the knee-high size of [Hrastovc]’s creation fool you. TrackRobot weighs in at a monstrous 60 kg (130 lbs) of steel, motors, and battery. It sports two 48V motors in a body and frame made from pieces of finger-jointed sheet steel, and can reach speeds of up to four meters per second with a runtime of up to an hour. The project’s link has more pictures as well as DXF files of the pieces used for the body.

Currently TrackRobot is remote-controlled, but one goal is to turn it into a semi-autonomous snow plow. You can see TrackRobot going through its first steps as well as testing out a plow prototype in the videos embedded below.

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Here’s Why Hoverboard Motors Might Belong In Robots

[madcowswe] starts by pointing out that the entire premise of ODrive (an open-source brushless motor driver board) is to make use of inexpensive brushless motors in industrial-type applications. This usually means using hobby electric aircraft motors, but robotic applications sometimes need more torque than those motors can provide. Adding a gearbox is one option, but there is another: so-called “hoverboard” motors are common and offer a frankly outstanding torque-to-price ratio.

A teardown showed that the necessary mechanical and electrical interfacing look to be worth a try, so prototyping has begun. These motors are really designed for spinning a tire on the ground instead of driving other loads, but [madcowswe] believes that by adding an encoder and the right fixtures, these motors could form the basis of an excellent robot arm. The ODrive project was a contender for the 2016 Hackaday Prize and we can’t wait to see where this ends up.

Stepper Motor Robot Arm Has Smooth Moves

[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

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

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

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

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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