Ro-Bow, The Violin Playing Robot

There are robots that will vacuum your house, mow your lawn, and keep their unblinking electronic eyes on you at all times while hovering hundreds of feet in the air. How about a robot that plays a violin? That’s what [Seth Goldstein] built. He calls it a ‘kinetic sculpture’, but there more than enough electronics and mechatronics to keep even the most discerning tinkerer interested.

There are three main parts of [Seth]’s violin-playing kinetic sculpture. The first is a bow carriage that draws the bow across the strings using an electromagnet to press the bow against the strings. The individual strings are fingered with four rubber disks, and a tilting mechanism rotates the violin so the desired string is always underneath the bow and mechanical fingers.

As far as software goes, the Ro-Bow transforms MIDI files into robotic mechanization that make the violin sing. From what we can tell, it’s not quite as good as a human player; only one string at a time can be played. It is, however, great at what it does and is an amazing mechanical sculpture.

Video Below.

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Openhand Combines 3D Printing with Urethane Casting

Yale University brings us quite a treat with their Openhand Project.

If you’ve ever operated a robotic arm, you know that one of the most cumbersome parts is always the end effector. It will quickly make you realize what an amazing work of engineering the human hand really is, and what a poor intimation a simple open-close gripper ends up being.

[Yale] is working to bring tendon-driven robotic hands to the masses with an interesting technique of combining 3D printing and resin/urethane casting. Known as Hybrid Deposition Manufacturing (HDM), it allows the team to 3D print robotic fingers that also contain the mold for finger pads and joints, all built right into the 3D part.  The tendon-driven fingers allow for a very simple design that are not only easy to make, but have a low parts count as well. Because of the human-like tendons, the fingers naturally curl around the object, distributing it’s force much more evenly and naturally, much like a human hand would. In the videos after the break, you can see the building process, as well as the hand in action.

Best news is that it’s all open source. They also include some python libraries so you can customize the CAD files fit your needs.

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EddiePlus, the Edison based balancing robot

[Renee] dropped a tip to let us know about EddiePlus, her balancing robot creation. As its name might imply, EddiePlus is controlled by an Intel Edison processor. More specifically, [Renee] is using several of Sparkfun’s Edison Blocks to create Eddie’s brain. EddiePlus’ body is 3D printed, while his movement comes from two Pololu DC motors with wheels and encoders. The full build instructions are available as a PDF from [Renee’s] Google drive.

Eddie is able to balance and drive around on two wheels, much like a Segway. Sensor data for balance comes from Sparkfun’s LSM9DS0 based Inertial Measurement Unit (IMU) block. In this new “plus” version of Eddie, [Renee] has added encoders to the robot’s wheels. This makes it easier for him to adapt to changing loads – such as pumping iron (or banana plugs as the case may be). The encoders also help with varying terrain, as [Renee] demonstrates by tilting a board as Eddie drives on it. Eddie’s code is written in C, and available on Github.  Controlling Eddie is as easy as sending simple commands via UDP.

As you might imagine, the Intel Edison still has plenty of cycles left over after computing Eddie’s balance. [Renee] uses some of these with a webcam based teleoperation mode.

Click past the break to see Eddie in action!

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Fold a Hexapod from Pilfered Office Supplies

Hexapods are wonderful things. With their elegant gait and insect-like caricature, they’re an instant hit for coffee-table-conversation-starters. They’re also wonderfully expensive, with the redundancy of each leg chewing viciously into your pocket. This price point is a deal-breaker for many, but for others, it’s a challenge to let one’s design skills defy that barrier. [Mike Estee] is one such engineer who’s done his best to design away a stock structure with a cardboard variant that wont break the bank.

On the table, [Mike] assembles his hexapod frame from budget servos, corrugated cardboard, paper clips, and tape. The result is a hexapod frame that can be built for practically just the cost of the servos (about $80 in this case). In his posts, [Mike] details the design evolution of the frame focusing especially on the legs, which he intended to be folded from a single sheet. After a few revisions, [Mike] succeeded, and he’s graciously posted his latest revision on his blog [PDF].

While we’ve certainly seen impressive budget hexapods before, we really appreciate the elegance and simplicity of a design made entirely from a single sheet of cardboard. His progress is a step forward to reaching a ubiquitous low-cost, force-control based robot platform. While that’s a milestone many of us hope to see in the future, he’s done a fantastic job designing a proof-of-concept frame template that anyone can cut out and assemble with a couple of spare hours.

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Ball Balancing Robot Uses New TOF Sensor

By now, you’ve most likely have seen or even played with an ultrasonic distance sensor. They work by emitting a sound, and then listening for the “ping” to return. The sensor can then tell how far an object is away by calculating the time in between. With sound waves traveling at 343.2 meters per second (768 mph), it’s no small task to measure the short time it takes for the sound to be emitted, then hit something a few feet away, and return. Now, imagine trying to do that with light.

Light in comparison moves at a whopping 299,792,458 meters per second (or about 671 million miles per hour). You’re going to have to have a pretty fast finger on a stopwatch to measure the time it takes for light to bounce back from an object a few inches away.

[Paul Bristow] is doing just that with the use of a new Time of Flight (ToF) sensor called the TeraRanger One. Developed in cooperation with CERN, this sensor uses a very narrow beam of light (listed as +/- 2 degrees) to accurately measure the position of an object to a resolution of 5mm, with distances up to 14 meters away. It boasts an impressive update rate of >1000 samples a second, and is very micro-controller friendly with UART, I2C, SPI, and PWM output.

[Paul] and his fellow hackers at the Post Tenebras Lab Hackerspace in Geneva got their hands on this sensor, and in a short time had a ball balancing robot up and running. The crude program is not running a PID controller, so the results seen in the video after the break aren’t that impressive. Also, the sensor isn’t exactly cheap at about $180 USD. Despite that, it will be interesting to see what applications these sensors will be used for. If you have any ideas, leave them in the comments below.

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Cute Tiny Robot Gets a Pair of Hacked Eyes

One day while at our poor, poor Radio Shack, [davidhend] purchased a little 6-legged walking robot. It came with an infrared remote that allowed a user to control its movements from afar. After a few minutes of making the robot walk around [davidhend] got bored and decided it would be a great toy to hack.

His plan was to make the robot autonomous and able to avoid obstacles. To start off, the robot was taken apart enough to expose the circuit board. There he found a ST1155A bi-directional motor driver that was controlled by an on-board microcontroller. After checking out the ST1155A data sheet, [davidhend] thought he would be able to drive it with an Arduino. So, out came the soldering iron and all the unnecessary components were removed from the original circuit board.

An off the shelf PING))) sensor was mounted on the front of the robot and is responsible for detecting obstacles. That information is then sent back to the Arduino Nano which controls the motor driver to make the robot back up, turn and then start walking straight again until another obstacle is detected. [davidhend] made his Arduino Code (.zip file) available to anyone who wants to make a similar project. Check out the video after the break!

Oh, and if you plan to run down to the Shack to pick up a robot of your own you better do it like right now.

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Spline Thieving Makes Hobby Servos Even More Useful

For years the proprietary spline pattern of rc servos has been a dealbreaker for hobbyists who want to add custom shafts and gears to their servos. First, different servo sizes have different spline sizes, and each vendor equips their servos with different patterns. True, some special vendors sell custom gears that mate to these patterns, but, overall, the hard-to-replicate pattern has severely limited the output options for servos.

This pattern didn’t deter [JB], however. With some clever CAD skills, and two working implementations, he’s demonstrated that these spline patterns can be (1) harvested and (2) added into custom components, opening a new suite of design opportunities involving servos.

To capture the spline, [JB] imports an image into Solidworks, and traces the pattern on a properly scaled image. From there, he can embed this pattern directly into a physical model for fabrication.

To make parts that preserve this pattern, [JB] has two options. With his FormLabs printer, he can print components that already have the pattern feature, allowing him to press-fit custom links directly onto servos. Alternatively, for a sturdier component, he presents the milling method. With this technique, he drills a circle of bolt holes onto the desired output shaft and then mills out the center. From here, the shaft can also be directly pressed onto the servo spline where each spline groove fits snugly into the edge of the previously-drilled holes.

So, how well do they work? According to [JB] he’s actually managed to do some damage to himself before damaging to the 3D-printed part while trying to strip the pattern. The end-goal is to insert these shafts into transmissions for a miniature combat robot, another one of [JB’s] projects which is well-underway. Until then, we’re looking forward to seeing more servos tightly-integrated into upcoming projects.