There was a time when a two-legged walking robot was the thing to make. But after seeing years of Boston Dynamic’s amazing four-legged one’s, more DIYers are switching to quadrupeds. Now we can add master DIY robot builder [James Bruton] to the list with his openDog project. What’s exciting here is that with [James’] extensive robot-building background, this is more like starting the challenge from the middle rather than the beginning and we should see exciting results sooner rather than later.
Thus far [James] has gone through the planning stage, having iterated through a few versions using Fusion 360, and he’s now purchased the parts. It’s going to be about the same size as Boston Robotic’s SpotMini and uses three motors for each leg. He considered going with planetary gearboxes on the motors but experienced a certain amount of play, or backlash, with them in his BB-9E project so this time he’s going with ball screws as he did with his exoskeleton. (Did we mention his extensive background?)
Each leg is actually made up of an upper and lower leg, which means his processing is going to have to include some inverse kinematics. That’s where the code decides where it wants the foot to go and then has to compute backwards from there how to angle the legs to achieve that. Again drawing from experience when he’s done it the hard way in the past, this time he’s designed the leg geometry to make those calculations easy. Having written up some code to do the calculations, he’s compared the computed angles with the measurements he gets from positioning the legs in Fusion 360 and found that his code is right on. We’re excited by what we’ve seen so far and bet it’ll be standing and walking in no time. Check out his progress in the video below.
Humans can traverse pretty much any terrain thanks to their legs and fast-acting balancing system. So if you want a robot which should have equal flexibility, legs are a good way to go, this confirmed by all the achievements of Boston Dynamics’ robots. It was therefore natural for [Mike Rigsby] to model his robot dog after Boston Dynamics’ dog-like robot, SpotMini.
The build log on his Hackaday.io page makes for interesting reading. For example, he started out with the legs oriented like SpotMini but found that when trying to stand, the front legs worked fine but the rear ones slid or the dog shifted rearward or both happened. His solution was to take a cue from his 1990s Sony robot dog, Aibo, by reversing the orientation of the rear legs. He then upgraded his servo motors to ones with double the torque and increased the strength of the legs’ structure. In the first video below, you can see that his dog now lifts itself up to a standing position perfectly.
So far, to give it more of a dog-like personality he’s mounted Google’s AIY Vision Kit which changes a light’s color based on the degree to which a person is smiling, though we think a wagging tail would work well too. The possibilities are endless but one step at a time. See the second video below for a demonstration of the use of the Vision Kit.
Looking at this legged robot gives us the same feeling we had the first time we saw a two-wheeled balancer. At first glance it just shouldn’t work, but after a little thought it makes a lot of sense. The six-legged bot called OutRunner uses two sets of three legs to propel itself. The footfalls are staggered to mimic how a biped runs, but mechanically it’s just spinning wheels to which the legs attach. If you have a smart enough algorithm it will not only remain upright but be steerable too.
This is a Kickstarter offering to let you can get your hands on an unassembled kit for $200. That version comes with a universal camera mount but no camera. This may not sound like a problem, but look closer and you may notice what we have: The thing is remote-controlled and can run up to 20 MPH, but there’s not footage of it running slowly. We’d wager the need to keep itself balanced equates to the need to run rather than walk. Since it’s going to get away from you very quickly you probably need a camera and a wearable display (or a chase car like in the video) to make the most out of the OutRunner. But hey, who’s complaining about that? Sounds like a ton of fun to us!
When designing legged robots, we generally see an even number of legs. Mainly, we think, it is due to us modelling things after nature. But with robotics, you’re free to do whatever you want. [Iketomu-san] has built this unsettling 5 legged robot out of parts he had lying around. The gait is fairly interesting. He mentions that it could be used for robot fighting, where the odd leg would serve as a prop from behind and the two legs up front could be weapons. What kind of gait or use can you come up with for this thing?