Little Quadruped Uses Many Servos

Walking robots were once the purview of major corporations spending huge dollars on research programs. Now, they’re something you can experiment with at home. [Technovation] has been doing just that with his micro quadruped build.

The build runs twelve servos – three per leg – to enable for a great range of movement for each limb. The servos are all controlled by an Arduino Uno fitted with an Arduino Sensor Shield. Everything is fitted together with a 3D printed chassis and limb segments that bolt directly on to the servo output shafts. This is a common way of building quick, easy, lightweight assemblies with servos, and it works great here. Inverse kinematics is used to calculate the required motions of each joint, and the robot can take steps from 1 to 4cm long in a variety of gaits.

We’d love to see a few sensors and a battery pack added on to allow the ‘bot to explore further in an untethered fashion. [Technovation] has left some provision to mount extra hardware, so we look forward to seeing what comes next.

We’ve seen bigger quadrupeds do great things, too. Video after the break.

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The Adorable Robot Spot, Now In Affordable Form

If you’ve been following the Boston Dynamics project Spot, you’ve seen its capabilities and how we’re starting to see it being used in public more since its official release last year. But in a true display of how hobbyist electronics have been evolving and catching up with the big companies over the past few years, [Miguel Ayuso Parrilla] shows us his own take on the walking robot with CHOP, one of the finalists in this year’s Hackaday Prize.

CHOP is a DIY quadruped robot that works much in the same way as Spot, although in a smaller form-factor and, perhaps most impressive of all, a bill of materials that can be all acquired for under $500. The entire project is open source, meaning that anyone can built their own version of it with off-the-shelf parts and some 3D printing. If you can’t get the hardware however, you can still play with the PyBullet simulation of the mechanics that were used during the debugging process.

Running the show are two main components, a Raspberry Pi 4B and an Arduino Mega. While the Mega interfaces with the servo controllers and provides filtering for sensors like the inertial measurement unit, the Pi takes all that data in and uses a series of Python scripts in order to determine the gait of the robot and which way the servos should move through an inverse kinematics model. To control the direction in which the body of the robot should accelerate, a Bluetooth remote controller sends commands to the Raspberry Pi.

We’re excited to see home-grown projects rise to this level of complexity, which would be mostly unheard of a few years ago in the maker scene, and only presented by large tech companies with tons of money to spend on research and development. There are other quadruped robots to inspire yourself on than Spot though, like this one with a spherical design and fold-out legs. Check this one in action after the break.

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Spherical Quadruped Arduino Robot

[Greg06] started learning electronics the same way most of us did: buy a few kits, read a few tutorials, and try your hardest to put a few things together. Sound familiar? After a while, you noticed your skills started increasing, and your comfort level with different projects improved as well. Eventually, you try your hand at making your own custom projects and publishing your own tutorials.

Few are lucky to have a first-project as elaborate as [Greg06’s] quadruped robot. We don’t know about you, but for some of us, we were satisfied with blinking two LEDs instead of just one.

[Greg06’s] robot has a quadruped based, housed within a 3D printed spherical body. The legs are retractable and are actuated by tiny servo motors inside the body. [Greg06] even included an ultrasonic distance sensor for the obstacle avoidance mechanism. Honestly, if it weren’t for the ultrasonic distance sensor protruding from the spherical body, you might think that the entire robot was just a little Wiffle ball. This reminds us of another design we’ve seen before.

If that weren’t enough, the spherical head can rotate, widening the range of the ultrasonic distance sensor and obstacle avoidance mechanism. This is accomplished by attaching another servo motor to the head.

Pretty neat design if you ask us. Definitely one of the coolest quadrupeds we’ve seen.

Robotic Open Source Puppy Needs A Home

Personally, I am a fan of the real thing, but dogs aren’t an option for all. Plus, robotic dogs are easier to train and don’t pee on your couch. If you are looking to adopt a robotic companion, Stanford Pupper might be a good place to start. It’s a new open source project from the Stanford Robotics Student group,  a group of robotic hackers from Stanford University. This simple robotic quadruped looks pretty simple to build, but also looks like a great into to four-legged robots.

This is the first version of the design, but it looks pretty complete, built around a carbon fiber and 3D printed frame. The carbon fiber parts have to be cut out on a router, but you can order them pre-cut here, and you might be able to adapt it to easier materials. The Pupper is driven by twelve servos powered from a 5200 mAh 2S LiPo battery and a custom PCB that distributes the power. That means it could run autonomously.

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Compliant Quadruped Legs Using Servos

Walking robots that move smoothly are tricky to build and usually involve some sort of compliant leg mechanism — a robot limb that can rebound like natural physiology for much better movement than what a stiff machine can accomplish. In his everlasting quest to build a real working robot dog, [James Bruton] is working on an affordable and accessible Mini Robot Dog, starting with the compliant leg mechanism.

The 3D printed leg mechanism has two joints (hip and knee), with an RC servo to drive each. To make the joints compliant, both are spring-loaded to absorb external forces, and the deflection is sensed by a hall effect sensor with moving magnets on each side. Using the inputs from the hall effect sensor, the servo can follow the deflection and return to its original position smoothly after the force dissipates. This is a simple technique but it shows a lot of promise. See the video after the break.

A project can sometimes develop a life of its own, or in the case of [James]’s OpenDog, spawn experimentally evolving offspring. This is number four, and it’s designed  to be a platform for learning how to make a quadruped walk properly, and to be simple and cheap enough for others to build. We’re looking forward to seeing how it turns out.

If you missed it, also check out this robot’s weird sibling, self-balancing Sonic.

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Quadruped Robot Disguises Itself As A Ball

When the Skynet baseball bot swarms attack, we’ll be throwing [Carl Bugeja] some dirty looks for getting them started. He’s been working on 4B, a little quadruped robot that can transform itself into a sphere almost perfectly.

Before [Carl] was distracted by the wonders of PCB actuators more than a year ago, he started working on this little guy. He finally found some time to get it moving on its own, and the preliminary results look promising to say the least. Inside the 6 cm sphere is a total of 12 servos, 3 for each leg. All of the mechanical parts were 3D printed in nylon on an SLS machine, and the custom PCB has a BLE microcontroller module, an IMU and IR proximity sensors onboard. Everything is open source with all the files available on the Hackaday.io project page.

The microcontroller runs a full inverse kinematic model, so only the desired tip and base coordinate for each leg is input and the servo angles are automatically calculated. Ultimately [Carl] aims to have the robot both walking and rolling controllably. So far he’s achieved some degree of success in both, but it still needs some work (see the videos below. We’re eager to see what the future holds for this delightfully creepy bot.

Walking robots are always an interesting challenge. For more of our future overlords, check out this adorable little cat and this truly terrifying strandbeest.

Amazing Open Source Quadruped Capable Of Dynamic Motion

The more we read about [Josh Pieper]’s quadruped, the mjbots quad A0, the more blown away we are by his year of progress on the design. Each part of the robot deserves its own article: from the heavily modified brushless motors (with custom planetary gears) to the custom motor driver designed just for this project.

[Josh], realized early on that the off-the-shelf components like an ODrive just weren’t going to cut it for his application. So he designed his own board, took it through four revisions, and even did thermal and cycle testing on it. He ended up with the compact moteus board. It can pump out 400 Watts of peak power while its 3Mbit control protocol leaves plenty of bandwidth for real time dynamic control.

The motors and gearboxes are also impressive. It took thorough experimenting and taking inspiration from other projects  before he arrived at a 8108 quad copter motor modified and upgraded so heavily its own mother wouldn’t recognize it. This is all packed into a leg unit with three degrees of freedom that puts even the fanciest servo based quadruped to shame.

Finally it’s all packed into a neat four-legged robot frame with batteries and a Pi. You can get a video summary of the robot here or after the break, and we recommend reading his blog for some more images and details.

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