Omnidirectional Walker With Wheeled Feet

July 26, 2022 by Danie Conradie 4 Comments

[James Bruton] is on a quest to explore all the weird and wonderful methods of robot locomotion, and in his latest project created an omnidirectional walker that can move in any direction instantaneously.

The walker actually makes use of three independent four-legged Strider mechanisms, connected in a triangle at 120deg. Wheels are attached to the bottom of each leg, oriented at a right angle to the leg’s plane of motion to allow the foot to slide. Varying the relative speed and direction of each of the mechanisms lets the robot move in any direction, similar to his ball-wheeled robot. Each strider mechanism uses a single motor and looks similar to Strandbeest walkers, but it lifts its feet to traverse rougher terrain. [James] demonstrates this with some obstacles, and found that moving in such an orientation that all three sets of legs provide the best results.

[James] planes to build a larger rideable version, but we think he should mount a chest of Sapient Pearwood to carry all his stuff and name it The Luggage.

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A Most Unconventional Lego Walker

February 11, 2022 by Lewin Day 15 Comments

Lego Technic is a wonderful thing, making it easy to toy around with all manner of complicated mechanical assemblies without needing to do any difficult fabrication. [touthomme] recently posted one such creation to Reddit – a walker design that is rather unconventional.

The design dispenses with individually-actuated legs entirely. Instead, the two front legs are joined by an axle which pivots the legs about the body, which is shaped like an oval track. The rear legs are the same. A motorized carriage then travels along the oval track. When the weighted carriage reaches the front of the oval track, it forces the body to tip forwards, pivoting around the front legs and flipping the entire body over, swinging the rear legs forwards to become the front. The cycle then repeats again.

The flipping design, inspired by a toy, is something you wouldn’t expect to see in nature, as few to no animals have evolved mechanisms capable of continual rotation like this. It’s also unlikely to be a particularly efficient way of getting around, and the design would certainly struggle to climb stairs.

Some may claim the method of locomotion is useless, but we don’t like to limit our imaginations in that way. If you can think of a situation in which this walker design would be ideal, let us know in the comments. Alternatively, consider other walking designs for your own builds. Video after the break.

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Tardygrade Walker Is A Lesson In 3D Printed Design

July 23, 2021 by Danie Conradie 12 Comments

The ability to quickly create complex parts with 3D printers has created a platform to show off mechanical design skills. This is true in the case of [Dejan Ristic]’s capable little Tardygrade walking robot, which uses only two servos and a bunch of clever 3D printed parts.

The robot’s chassis is split into two subassemblies, each with a pair of feet on diagonal corners. As one pair of feet lifts the robot, the other section of the robot can rotate before coming back down, allowing the robot to turn. One servo handles the actuation of the feet, while the other rotates the body as required. An ESP32 based controller creates a web server user interface, and power comes from a lipo cell.

The interesting part of this robot is in how [Dejan] designed it for printing and assembly. All the parts can print without support, and in the correct orientation to optimize strength. There are only six screws in the assembly holding the servo and servo horns, while everything else uses snap fits or short pieces of filament. Take a look at the videos after the break to gain some appreciation of the design effort and attention to detail that went into this robot. Even the contact surfaces of the feet were carefully designed for optimum walking over flat surfaces and small obstacles.

This reminds us of [gzumwalt]’s little 3D printed creations, like the fridge crawler and mechanical edge-avoiding robot.

Disney Imagineering’s “Project Kiwi” Bears Groot

April 26, 2021 by Zach Zeman 31 Comments

Some days, we might be forgiven for believing Boston Dynamics has cornered the market on walking robots. They (and other players) are making incredible progress in their field, but three years ago Disney, trying to create autonomous, free-walking robotic actors for some of their more diminutive film characters, found none of the existing platforms were appropriate. So they set their Imagineering department to work on “Project Kiwi”, and we are now seeing the fruits of those efforts.

Research on bipedal robots has amassed over the years, and as the saying goes, if these Imagineers saw further it was by standing on the shoulders of larger robotic platforms. However, the Project Kiwi designers have made a laundry list of innovations in their process of miniaturization, from the “marrow conduit” cooling system which forces air through hollow bones, to gearing that allows actuators to share motors even across joints. The electronics are distributed around the skeleton on individual PCBs with ribbon flex cables to reduce wiring, and almost every component is custom fabricated to meet the complex size and weight requirements.

Even in this early prototype, Disney’s roots in life-like animatronics are evident. Groot’s movements are emotive, if a bit careful, and software can express a variety of personalities through his gaits and postures. The eyes and face are as expressive as we’ve come to expect (though a keen eye for seams puts off some definite Westworld vibes). Reportedly, this version can handle gentle shoves and contact, but we do spot a safety cable still attached to the head. So there’s probably some way to go before we’ll see this interacting with the general public in a park.

Disney’s Imagineering department has been doing some amazing work with robotics and they continue to make significant innovations in the more traditional fields of animatronics. It certainly looks like one of the coolest places to work right now, and now we’re itching to build our own bipedal friends to play with.

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A Walking Rover Destined Explore Your Fridge Door

December 10, 2020 by Danie Conradie 7 Comments

It’s usually the simple ideas that sprout bigger ones, and this was the case when we saw [gzumwalt]’s single-motor walking robot crawling up a fridge door with magnets on its feet. (Video, embedded below.)

The walking mechanism consists of an inner foot and two outer feet, connected by three sets of rotating linkages, driven by a single geared motor. The feet move in a leapfrog motion, in small enough steps that the center of mass always stays inside the foot area, which keeps it from tipping over. Besides the previously mentioned ability to crawl around on a vertical magnetic surface, it’s also able to crawl over almost any obstacle shorter than its step length. A larger version should also be able to climb stairs.

As shown, this robot can only travel in a straight line, but this could be solved by adding a disc on the bottom of the inner foot to turn the robot when the outer feet are off the surface. Add some microswitch feelers and an Arduino, and it can autonomously explore your fridge without falling off. Maybe we’ll get around to building it ourselves, but be sure to drop us a tip if you beat us to it!

[gzumwalt] is a master of 3D printed devices like a rigid chain and a domino laying robot. The mechanism for this robot was inspired by one design from [thang010146]’s marvelous video library of mechanisms.

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Robot Gets Around On All Fours, Thanks To Many, Many Servos

October 13, 2020 by Lewin Day 2 Comments

As far as robots are concerned, wheels and tracks are great ways to get around when you’ve got serious work to do. However, if you want to build something that feels more animal than machine, building a walking ‘bot is the way to go. [Technovation] delivers a great example in the form of this quadruped design.

It’s a build executed in the modern style, taking full advantage of contemporary design tools and processes. The entire robot is built around twelve servo motors that provide rotation and translation to the robot’s joints. After importing the servo models into Fusion 360, [Technovation] set about building the rest of the body around them. An Arduino Uno runs the show, which addresses the many servos thanks to a Sensor Shield that has a multitude of useful outputs.

[Technovation] put a specific focus on durability and robustness during the design phase. The platform is intended as a test bed for various walking styles and gaits, and thus any hardware failures would be an unnecessary distraction from the project’s goals. The chassis is a great platform to learn on, and we expect to see further developments in future.

The eerily lifelike robots from Boston Dynamics may have set a high bar, but DIYers are still out there having a crack at building capable walking robots. Video after the break.

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Compliant Quadruped Legs Using Servos

March 22, 2020 by Danie Conradie 4 Comments

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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