It’s always fun to look over aerial and satellite maps of places we know, seeing a perspective different from our usual ground level view. We lose that context when it’s a place we don’t know by heart. Such as, say, Mars. So [Matthew Earl] sought to give Perseverance rover’s landing video some context by projecting onto orbital imagery from ESA’s Mars Express. The resulting video (embedded below the break) is a fun watch alongside the technical writeup Reprojecting the Perseverance landing footage onto satellite imagery.
Some telemetry of rover position and orientation were transmitted live during the landing process, with the rest recorded and downloaded later. Surprisingly, none of that information was used for this project, which was based entirely on video pixels. This makes the results even more impressive and the techniques more widely applicable to other projects. The foundational piece is SIFT (Scale Invariant Feature Transform), which is one of many tools in the OpenCV toolbox. SIFT found correlations between Perseverance’s video frames and Mars Express orbital image, feeding into a processing pipeline written in Python for results rendered in Blender.
While many elements of this project sound enticing for applications in robot vision, there are a few challenges touched upon in the “Final Touches” section of the writeup. The falling heatshield interfered with automated tracking, implying this process will need help to properly understand dynamically changing environments. Furthermore, it does not seem to run fast enough for a robot’s real-time needs. But at first glance, these problems are not fundamental. They merely await some motivated people to tackle in the future.
This process bears some superficial similarities to projection mapping, which is a category of projects we’ve featured on these pages. Except everything is reversed (camera instead of video projector, etc.) making the math an entirely different can of worms. But if projection mapping sounds more to your interest, here is a starting point.
I was absolutely struck by a hack this week — [Adam Bäckström]’s amazing robot arm built with modified hobby servos. Basically, he’s taken apart and re-built some affordable off-the-shelf servo motors, and like the 6-Million-Dollar Man, he’s rebuilt them better, stronger, faster. OK, and smoother. We have the technology.
The results are undeniably fantastic, and enable the experienced hacker to get champagne robot motion control on a grape-juice budget by employing some heavy control theory, and redundant sensors to overcome geartrain backlash, which is the devil of cheap servos. But this didn’t come out of nowhere. In his writeup, [Adam] starts off with “You could say this project started when I ordered six endless servos in middle school, more than 15 years ago.” And it shows.
Go check out this video of his first version of the modified servos, from a six-axis arm he built in 2009(!). He’s built in analog position sensors in the motors, which lets him control the speed and makes it work better than any other hobby servo arm you’ve ever seen, but there’s still visible backlash in the gears. A mere twelve years later, he’s got magnetic encoders on the output and a fast inner loop compensates for the backlash. The result is that the current arm moves faster and smoother, while retaining accuracy.
Twelve years. I assume that [Adam] has had some other projects on his plate as well, but that’s a long term project by any account. I’m stoked to see his work, not the least because it should help a lot of others who are ready to step up their desktop servo-arm projects. But the real take-home lesson here is that if you’ve got a tough problem that you’re hacking on, you don’t have to get it done this weekend. You don’t have to get it done next weekend either. Keep hammering on it as long as you need, but keep on hammering. When you get it done, the results will be all the better for the long, slow, brewing time. What’s the longest project that you’ve ever worked on?
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[Engineering After Hours] wanted a highly maneuverable robot chassis with a tight turning radius. Skid steering seemed to be the perfect solution, but the available commercial options didn’t take his fancy. Thus, a custom build was the answer – with impressive results.
The build packs two large RC motors, one for each side, with each driving two wheels through a belt drive. This reduces the electronics required to the bare minimum for skid steering. It’s all assembled within a plasma-cut metal chassis which is more than tough enough to take some hard knocks.
One of the primary goals on the build was to eliminate the risk of vibrations and shock damaging the motors and gearboxes. Many off-the-shelf designs couple the wheels directly to gearbox output shafts, potentially damaging the expensive components over time. In this design, a separate bearing assembly is used to take the load from the wheels instead.
It’s a great example of how an engineering-first approach can build a sturdy ‘bot with a minimum of fuss. Outfitted with some fat off-road tyres the performance is impressive, with the ‘bot having no trouble tearing it up in mud, snow, and water.
[Adam]’s first robot arm build was a major disappointment, when the servos he had purchased for the build turned out to be terrible at holding an angle. With limited funds, he elected to improve on what he had, learning much about precision control techniques along the way. [Adam] taught himself how to implement industrial strength control loops using hobby hardware, by implementing additional encoders into servos and taking into account velocity and torque in addition to just position. With a magnetic encoder on the servo output shaft and a tiny optical encoder hand-built for inside the motor itself, much higher accuracy is achievable by allowing the control system to compensate for backlash.
While we certainly agree that “Devil Girl From Mars” is an attractive movie title, we have yet to see this apparent British B-movie delight for ourselves. If [Cory Collins]’ fantastic build of Chani, the lumbering, terrifying robot that accompanies the vinyl-clad and caped Devil Girl in question is any indication, we bet it’s delightfully bad.
[Cory] was able to faithfully reproduce Chani — lights, lumbering and all — for less than $50. This price tag does not include the vacuum former required to make the domed head, but hey, it’s an investment into future projects.
[Cory] started by dissecting an R/C stunt car from Harbor Freight and stringing the innards up to a 3D-printed walking mechanism that’s been modified to use gear-reduced motors so it walks more slowly. While Chani is stomping around on TPU treads, the LEDs from the R/C car’s headlights shine inside of its dome. Chani’s boxy body is a big paper sculpture that looks spot-on to us when compared to the movie’s trailer.
We love the way that Chani walks — it sort of dips and glides along in a forward-facing Moonwalk fashion. As you can see in the video below, [Cory] totally nailed the robot’s gait, and it’s hilarious to watch Chani’s little coolant hose-looking arms dangle and shake as he makes his slow and menacing way across the table. Stick around for some scary nighttime footage of Chani against a thunderstorm.
When it was first announced that limits would be placed on recreational RC aircraft heavier than 250 grams, many assumed the new rules meant an end to home built quadcopters. But manufacturers rose to the challenge, and started developing incredibly small and lightweight versions of their hardware. Today, building and flying ultra-lightweight quadcopters with first person view (FPV) cameras has become a dedicated hobby onto itself.
But as impressive as those featherweight flyers might be, the CogniFly Project is really pushing what we thought was possible in this weight class. Designed as a platform for experimenting with artificially intelligent drones, this open source quadcopter is packing a Raspberry Pi Zero and Google’s AIY Vision Kit so it can perform computationally complex tasks such as image recognition while airborne. In case any of those experiments take an unexpected turn, it’s also been enclosed in a unique flexible frame that makes it exceptionally resilient to crash damage. As you can see in the video after the break, even after flying directly into a wall, the CogniFly can continue on its way as if nothing ever happened.
The modern home is filled with plenty of “smart” devices, but unfortunately, they don’t always speak the same language. The coffee maker and the TV might both be able to talk to your phone through their respective apps, but that doesn’t necessarily mean the two appliances can work together to better coordinate your morning routine. Which is a shame, since if more of these devices could communicate with each other, we’d be a lot closer to living that Jetsons life we were promised.
Luckily, as hardware hackers we can help get our devices better acquainted with one another. A recent post by [MyHomeThings] shows how the ESP8266 can bridge the gap between a Roomba and Amazon’s Alexa assistant. This not only allows you to cheaply and easily add voice control to the robotic vacuum, but makes it compatible with the Amazon’s popular home automation framework. This makes it possible to chain devices together into complex conditional routines, such as turning off the lights and activating the vacuum at a certain time each night.
The hack depends on the so-called Roomba Open Interface, a seven pin Mini-DIN connector that can be accessed by partially disassembling the bot. This connector provides power from the Roomba’s onboard batteries as well as a two-way serial communications bus to the controller.
By connecting a MP1584EN DC-DC converter and ESP8266 to this connector, it’s possible to send commands directly to the hardware. Add a little glue code to combine this capability with a library that emulates a Belkin Wemo device, and now Alexa is able to stop and start the robot at will.