Details: Try wrapping your head around the mechanism behind this model. Using only two motors and a simple program, this robot can turn in place, avoid obstacles, and balance itself by shifting its center of gravity. The builder is intentionally not making it too obvious how it works, but I think it's possible to reverse engineer some of it. The "feet" actually spin, so the axles going down to them must be geared to power that feature. The shifting of the center of gravity could be worked in by providing extra friction somewhere in the gear train - conveniently, this design combines that with the task of lifting each foot to take steps.
Some of the clever parts of this design don't actually involve gearing at all. Putting the weight of the motors low in the legs makes the walking motion much easier on the gear train. The combination of a touch sensor and an ultrasonic sensor handles obstacle avoidance in a way that should be easy to program - and since the ultrasonic sensor is mounted loosely, it sways from side to side to allow for more thorough detection of obstacles. This is a masterpiece of showing how to get a variety of features out of very few sensors and motors.
A brief note about this "of the day" blog: It just hasn't been possible to post daily lately. Among other things, last minute plans to be at all four days of BrickFair have eaten up time that would normally be spent posting. We'll get back on schedule after we come back with a full report from the event.
Details: We've seen plenty of walkers before, but I haven't seen a fully steerable hexapod that uses only two motors before. One large Power Functions motor handles the walking motion, and a second motor articulates the body at two points to allow it to change directions. It's a surprisingly simple solution, but it works well. The other nice thing is that we now finally have a walker design that can be made with a LEGO robotics kit without using all of the motors in the kit.
Details: 222Doc claims to have created the first NXT-based biped that can climb stairs. I'll have to take him at his word for that (I'm not aware of any video to prove that, and he hasn't posted programs either). His new creation, though, is even more impressive - a quadruped robot with three-toed limbs that can climb like a sloth. That's the theory, anyway - the machinery has been tested to verify that it can handle the load of lifting it's own weight on ladders in any direction, but the programming's not done yet. This isn't quite purist - you can see some multiplexers and unofficial cable used so that the one NXT can control all of the motors (looks like 8 NXT motors and 4 Power Functions motors to me). Still - this is proof of concept for a type of four-legged walker we've never seen before. I can't wait to see one of these things crawling overhead at a LEGO or robotics event.
EDIT: This is what I get for rushing posts - it turns out that there is, in fact, a video of the X2 walking up stairs, and you can see other videos from the same builder on YouTube as well. More details about the X4 sloth 'bot can be found on the nxtasy forums.
Details: I've previously blogged a fewinterestingwalkingmachines here, but the fact of the matter is that many of those models are a bit out of reach for most LEGO fans. The availability of various parts (specifically motors and pneumatic elements) leaves a bit to be desired. However, there's one current kit (the 8049 TECHNIC Log Loader) that is widely available and actually includes all the parts you need to try out simple pneumatic circuitry and walking machines. Naturally, I took this as a challenge - can a decent pneumatic walker be built out of only the parts in that one kit? You can see the results (and full building instructions!) at the links above. Spoiler alert: it can be done, but it took me a few tries to get it working smoothly.
Details:
I've previously expressed my love for pneumatic walkers, but they have a few limitations. Pneumatic walkers can't steer, and they can't be controlled by sensors or programmable bricks. This walker used an NXT and three motors to make a walking robot that can be steered in either direction, respond to light, and sense distance. Construction details are pretty clear in the video above, but there's also a flickr set from the builder showing still photos of the walker.
Details: Every once in a while, you hear me mention that something has become a "fad" of sorts among LEGO fans. About a decade or so back, a rash of pneumatic walkers flooded LUGNET (the LEGO Users Group network) and RTL (Rec.Toys.LEGO, a USENET newsgroup from back when "USENET" and "newsgroup" were things people actually used) as Technic and Mindstorms fans tried to push the limits of what could be done mechanically without having to use expensive motors and sensors to automate creations. Pneumatic walkers are an incredibly fun application of pneumatic logic gates. Simple logic gates (of the same sort used in electronics) have long been considered a "classic project" for LEGO pneumatic elements, but the relative scarcity of those parts generally prevents people from experimenting with the field too much. The basic idea of pneumatic walkers is to have all motion control handled purely by pneumatics - no motors, gears, or sensors are needed on the machine itself. The only source of power is a pneumatic tube supplying air pressure. Each piston-forced movement is mechanically attached to another pneumatic valve, which in turn will force another pneumatic piston to trigger its linkages. Since LEGO pneumatic parts aren't quite instantaneous, they can be used in a variety of synchronized machines, including walkers. Today's featured model is a recent creation that claims to be the smallest pneumatic walker. The machine has a small footprint and only uses the smallest size of pneumatic piston. The newer studless valves are used here to great effect - I can't imagine trying to build a similar structure while needing to brace the older valve elements with bricks. Don't miss the video on Brickshelf alongside the photos.
Details: This 'bot is a pretty clever simplification of the "walker" format. Only one motor is used - a series of levers makes the rest of the motion work. The main advantage of this is that it frees up additional motors to be used for other tasks. Another interesting this about this walker is the way that the beams and motors make this something you could really only do with LEGO MINDSTORMS NXT - normally it's not too difficult to create an RCX-based version of an NXT 'bot or vice-versa, but this one would be nearly impossible to recreate with the older parts. For those of you who have a LEGO MINDSTORMS NXT kit and want directions, full building instructions are available. Of course, from there, you should come up with your own ideas for sensors and other motors, but this is a great starting point.
Details: Laurens200 is an impressive kid I found on YouTube who has a real knack for LEGO robotics. I'll probably be featuring some of his/her other 'bots in the future (and some of them are more exciting than this one, but hey, I try to pace myself). This bot is a simple walker with a whimsical wagging tail. It's quite elegant, and there's video, Brickshelf photos, building instructions, a full write-up and the original program available online. Laurens is a master at documenting his/her creations, and thanks to the sheer amount of detail written about this efficient and simple design, this is one you can try at home with your own LEGO MINDSTORMS NXT kit.
can control all of the motors (looks like 8 NXT motors and 4 Power Functions motors to me). Still - this is proof of concept for a type of four-legged walker we've never seen before. I can't wait to see one of these things crawling overhead at a LEGO or robotics event.
- normally it's not too difficult to create an RCX-based version of an NXT 'bot or vice-versa, but this one would be nearly impossible to recreate with the older parts. For those of you who have a 
