HobbyKing Cheetah: Building Running Robots from Hobby Motors

[Ben Katz] is building a running robot from hobby level brushless motors, all on his blog under the tag, “HobbyKing Cheetah.

One of the features of fancy modern industrial motor and controller sets is the ability for the motor to act as a mass-spring-damper. For example, let’s say you want a robot to hold an egg. You could have it move to the closed position, but tell the controller you only want to use so much force to do it. It will hold the egg as if there was a spring at its joint.

Another way you could use this is in the application of a robot leg. You tell the controller what kind of spring and shock absorber (damper) combination it is and it will behave as if those parts have been added to the mechanism. This is important if you want a mechanical leg to behave like a biological leg.

[Ben] had worked on a more formal project which used some very expensive geared motors to build a little running robot. It looks absolutely ridiculous, as you can see in the following video, but it gives an idea of where he’s going with this line of research. He wanted to see if he could replace all those giant geared motors with the cheap and ubiquitous high performance brushless DC motors for sale now. Especially given his experience with them.

So far he’s done a very impressive amount of work. He’s built a control board. He’s characterized different motors for the application.  He’s written a lot of cool software; he can even change the stiffness and damping settings on the fly. He has a single leg that can jump. It’s cool. He’s taking a hiatus from the project, but he’ll be right back at it soon. We’re excited for the updates!

Real World Race Track is Real Hack

[Rulof] never ceases to impress us with what he comes up with and how he hacks it together. Seriously, how did he even know that the obscure umbrella part he used in this project existed, let alone thought of it when the time came to make a magnet mount? His hack this time is a real world, tabletop race track made for his little brother, and by his account, his brother is going crazy for it.

His race track is on a rotating table and consists of the following collection of parts: a motor, bicycle wheel, casters from a travel bag, rubber bands (where did he get such large ones?), toy car and steering wheel from his brother, skateboard wheels, the aforementioned umbrella part and hard drive magnets. In the video below we like how he paints the track surface by holding his paint brush fixed in place and letting the track rotate under it.

From the video you can see the race track has got [Rulof] hooked. Hopefully he lets his brother have ample turns too, but we’re not too sure. Some additions we can imagine would be robotics for the obstacles, lighting, sounds and a few simulated explosion effects (puffs of flour?).

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Hackaday Prize Entry: The Green Machine

For Hackers, rapid prototyping is made easier using basic building blocks such as the Raspberry Pi, Arduino and the huge variety of add on shields for home brew projects. But we don’t see too many real world Industrial applications or machines built using these off-the-shelf electronics. [SlyScience] built The Green Machine – an industrial grade, automated spray painting device to help coat polycarbonate tubes consistently.

The Green Machine is essentially a linear drive that can move a spray gun across a spinning clear tube and coat it evenly with the desired color. These tubes are used as color filters – they slide over standard T5, T8 or T12 fluorescent lamps – and are used in advertising, special effects, films and similar applications. For almost 10 years prior to this machine, the task was done manually. The HPLV (high pressure, low volume) spray gun used for this process needed skilled hands to get consistent results. It was easy to ruin a tube and cleaning them was not possible. [SlyScience] figured things out on the go – teaching himself and figuring out all of the software and hardware pieces of the puzzle. The welded steel frame is about the only “custom” part in this build. Everything else is COTS. Check out the video of The Green Machine in action below, and if you have any tips to help improve the build, chime in with your comments.

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The Most Powerful Diesel Engine

Ever. Literally.

A gearhead friend of ours sent along a link to a YouTube video (also embedded below) promising the world’s most powerful engine. Now, we’ll be the first to warn you that it’s just an advertisement, and for something that you’re probably not going to rush out and buy: the Wärtsilä 14RT marine engine.

A tiny bit of math: 96 cm cylinder diameter times 250 cm piston stroke = 1,809,557 CC. And it generates around 107,000 HP. That’s a fair bit, but it runs at a techno-music pace: 120 BPM RPM. With twelve cylinders, we’d love to hear this thing run. Two-strokes make such a wonderful racket! Wonder if they’ve tried to red-line it? It’s a good thing we don’t work at Wärtsilä.

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Hackaday Prize Entry: Industrial Servo Control On The Cheap

[Oscar] wonders why hobby projects ignore all the powerful brushless motors available for far less than the equivalent stepper motors, especially with advanced techniques available to overcome their deficiencies.  He decided it must be because there is simply not a good, cheap, open source motor controller out there to drive them precisely. So, he made one.

Stepper motors are good for what they do, open-loop positioning along a grid, but as far as industrial motors go they’re really not the best technology available. Steppers win on the cost curve for being uncomplicated to manufacture and easy to control, but when it comes to higher-end automation it’s servo control all the way. The motors are more powerful and the closed-loop control can be more precise, but they require more control logic. [Oscar]’s board is designed to fill in this gap and take full advantage of this motor control technology.

The board can do some pretty impressive things for something with a price goal under $50 US dollars. It supports two motors at 24 volts with up to 150 amps peak current. It can take an encoder input for full closed loop control. It supports battery regeneration for braking. You can even augment a more modest power supply to allow for the occasional 1 KW peak movement with  the addition of a lithium battery. You can see the board showing off some of its features in the video after the break.

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Cyclists Use Tiny Motors to Cheat

Blood doping is so last decade! The modern cyclist has a motor and power supply hidden inside the bike’s frame.

We were first tipped off to the subject in this article in the New York Times. A Belgian cyclocross rider, Femke Van den Driessche, was caught with a motor hidden in her bike.

While we don’t condone sports cheating, we think that hiding a motor inside a standard bike is pretty cool. But it’s even more fun to think of how to catch the cheats. The Italian and French press have fixated on the idea of using thermal cameras to detect the heat. (Skip to 7:50 in the franceTVsport clip.) We suspect it’s because their reporters recently bought Flir cameras and are trying to justify the expense.

The UCI, cycling’s regulatory body, doesn’t like thermal. They instead use magnetic pulses and listen for the characteristic ringing of a motor coil inside the frame. Other possibilities include X-ray and ultrasonic testing. What do you think? How would you detect a motor inside a bike frame or gearset?

A Simple And Educational Brushless Motor

Sometimes there is no substitute for a real working model to tinker with when it comes to understanding how something works. Take a brushless motor for example. You may know how they work in principle, but what factors affect their operation and how do those factors interact? Inspired by some recent Hackaday posts on brushless motors, [Matt Venn] has built a simple breadboard motor designed for the curious to investigate these devices.

The rotor and motor bodies are laser-cut ply, and the rotor is designed to support multiple magnet configurations. There is only one solenoid, the position of which relative to the magnets on the rotor can be adjusted. The whole assembly is mounted on the edge of a breadboard, and can be rotated relative to the breadboard to vary the phase angle at which the drive circuit’s Hall-effect sensor is activated by the magnet. The drive circuit in turn can have its gain and time constants adjusted to study their effects on the motor’s running.

[Matt] has made all the design files available in his GitHub repository, and has recorded a comprehensive description of the motor’s operation in the YouTube video below the break. Continue reading “A Simple And Educational Brushless Motor”