Achieving Human Level Competitive Robot Table Tennis

A team at Google has spent a lot of time recently playing table tennis, purportedly only for science. Their goal was to see whether they could construct a robot which would not only play table tennis, but even keep up with practiced human players. In the paper available on ArXiv, they detail what it took to make it happen. The team also set up a site with a simplified explanation and some videos of the robot in action.

Table tennis robot vs human match outcomes. B is beginner, I is intermediate, A is advanced. (Credit: Google)
Table tennis robot vs human match outcomes. B is beginner, I is intermediate, A is advanced. (Credit: Google)

In the end, it took twenty motion-capture cameras, a pair of 125 FPS cameras, a 6 DOF robot on two linear rails, a special table tennis paddle, and a very large annotated dataset to train multiple convolutional neural networks (CNN) on to analyze the incoming visual data. This visual data was then combined with details like knowledge of the paddle’s position to churn out a value for use in the look-up table that forms the core of the high-level controller (HLC). This look-up table then decides which low-level controller (LLC) is picked to perform a certain action. In order to prevent the CNNs of the LLCs from ‘forgetting’ the training data, a total of 17 different CNNs were used, one per LLC.

The robot was tested with a range of players from a local table tennis club which made clear that while it could easily defeat beginners, intermediate players pose a serious threat. Advanced players completely demolished the table tennis robot. Clearly we do not have to fear our robotic table tennis playing overlords just yet, but the robot did receive praise for being an interesting practice partner. Continue reading “Achieving Human Level Competitive Robot Table Tennis”

Robotic Ball-Bouncing Platform Learns New Tricks

[T-Kuhn]’s Octo-Bouncer platform has learned some new tricks since we saw it last. If you haven’t seen it before, this device uses computer vision from a camera mounted underneath its thick, clear acrylic platform to track a ball in 3D space, and make the necessary (and minute) adjustments needed to control the ball’s movements with a robotic platform in real time.

We loved the Octo-Bouncer’s mesmerizing action when we saw it last, and it’s only gotten better. Not only is there a whole new custom ball detection algorithm that [T-Kuhn] explains in detail, there are also now visualizations of both the ball’s position as well as the plate movements. There’s still one small mystery, however. Every now and again, [T-Kuhn] says that the ball will bounce in an unexpected direction. It doesn’t seem to be a bug related to the platform itself, but [T-Kuhn] has a suspicion. Since contact between the ball and platform is where all the control comes from, and the ball and platform touch only very little during a bounce, it’s possible that bits of dust (or perhaps even tiny imperfections on the ball’s surface itself) might be to blame. Regardless, it doesn’t detract from the device’s mesmerizing performance.

Design files and source code are available on the project’s GitHub repository for those who’d like a closer look. It’s pretty trippy watching the demonstration video because there is so much going on at once; you can check it out just below the page break.

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Moving Things With Electricity

We use electricity to move things with the help of motors and magnets all the time. But if you have enough voltage, you can move things with voltage alone. As [James] found out, though, it works best if your objects — ping pong balls, in his case — are conductive.

He wanted to add a Van de Graaff generator to add to his “great ball machine” which already has some cool ways to move ping pong balls. However, to get the electrostatic motion, [James] had to resort to spraying the balls with RF shielding spray.

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Robotic Ball Bouncer Uses Machine Vision To Stay On Target

When we first caught a glimpse of this ball juggling platform, we were instantly hooked by its appearance. With its machined metal linkages and clear polycarbonate platform, its got an irresistibly industrial look. But as fetching as it may appear, it’s even cooler in action.

You may recognize the name [T-Kuhn] as well as sense the roots of the “Octo-Bouncer” from his previous juggling robot. That earlier version was especially impressive because it used microphones to listen to the pings and pongs of the ball bouncing off the platform and determine its location. This version went the optical feedback route, using a camera mounted under the platform to track the ball using OpenCV on a Windows machine. The platform linkages are made from 150 pieces of CNC’d aluminum, with each arm powered by a NEMA 17 stepper with a planetary gearbox. Motion control is via a Teensy, chosen for its blazing-fast clock speed which makes for smoother acceleration and deceleration profiles. Watch it in action from multiple angles in the video below.

Hats off to [T-Kuhn] for an excellent build and a mesmerizing device to watch. Both his jugglers do an excellent job of keeping the ball under control; his robotic ball-flinger is designed to throw the ball to the same spot every time.

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Edge-Lit Ping Pong Paddle Lights Up The Fight

[George] and his coworkers like to blow off a little lunchtime steam on the company ping pong table. We might do the same, except it’d just be us versus the wall, and most of the exercise would consist of bending over to pick the ball up off the floor. When he found a scrap piece of acrylic out in their shop, [George] got the bright idea to make an edge-lit paddle featuring the company’s logo.

Not only does the paddle look cool, it works pretty well, too, even though it’s heavier and has smooth surfaces compared to a standard paddle. To begin, [George] found a regulation-size paddle outline and imported it into SolidWorks, then designed all the necessary cuts for the LEDs and other electronics. He also designed and printed ergonomic grips to protect the goods.

Continuing the stuff-on-hand theme, [George] used through-hole LEDs and dug into the abundance of battery clips and springs they have lying around for designing prototypes, instead of making it all fancy with SMT LEDs and a rechargeable battery pack. Slip on those sweatbands, because we’re serving up the build video after the break.

We see more ping pong balls than paddles around here, and that’s probably because they make great LED diffusers.

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Glitching LED Display Proves Crowd Favorite

There’s something enchanting about the soft glow of a properly diffused LED, and this is only improved by greater numbers of LEDs. [Manoj Nathwani] was well aware of this, setting out to build a large display using ping-pong balls for their desirable optical qualities.Unfortunately, not everything went to plan, but sometimes that’s not all bad.

The matrix, built back in 2016 for EMF Camp, was sized at 32×18 elements, for a total of 576 pixels. This was achieved with the use of 12 WS2811 LED strips, with the lights set out on a 50mm grid. Cheap knock-off pingpong balls were used for their low cost, and they proved to be excellent diffusers for the LEDs.

With everything wired up to a NodeMCU, basic testing showed the system to be functioning well. However, once the full matrix was assembled in the field, things started to fall over. Basic commands would work for the first 200 LEDs or so, and then the entire matrix would begin to glitch out and display random colors. Unable to fix the problem in the field, [Manoj] elected to simply run the display as-is. Despite the problems, passers-by found the random animations to be rather beautiful anyway, particularly at night.

After the event, [Manoj] determined the issue was due to the excessive length of the data line, which in the final build was 48 meters long. While the problem may be rectified when [Manoj] revisits the project, the audience seemed to appreciate the first revision anyway.

LED displays will be a hacker staple until the heat death of the universe. Ping pong balls will also likely retain their position as a favorite diffuser. If you’ve got a great LED build of your very own, be sure to hit up the tips line!

Trick Shot Bot Flings Balls Into Wine Glass Every Time

We’ve heard of beer pong, but we’re not sure we’ve heard of wine pong. And certainly never wine pong automated with a ping pong ball throwing robot like this one.

There’s not a huge amount of detail available in the video below, and no build log per se. But [Electron Dust] has a few shots in the video that explain what’s going on, as well as a brief description in a reddit thread about the device. The idea is to spin a ball up to a steady speed and release it the same way every time. The rig itself is made of wood and spun by plain brushed DC motors – [Electron Dust] explains that he chose them over PWM servos to simplify things and eliminate uncertainty in the release point. The ball is retained by a pair of arms, each controlled by a pair of hobby servos. An Arduino spins along with everything else and counts 50 revolutions before triggering the servos to retract and release the ball. A glass positioned at the landing spot captures the ball perfectly once everything is dialed in.

Here’s hoping that build details end up on his blog soon, as they did for this audio-feedback juggling machine. And while we certainly like this project, it might be cool if it could aim the ball into the glass. Or it could always reposition the target on the fly.

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