Figured I'd share some of my more recent work; Dragoon. This is an RX-64 based quadruped robot using an ArbotiX Robocontroller and the new & upcoming RX-Bridge, which allows the ArbotiX to control higher end DX/RX/EX series Dynamixels. One of the cool things about the ArbotiX is that it is Arduino software compatible, so it uses the same Arduino IDE with some added libraries, VERY easy to use.
Walking gait is still needing tweaking, I'd guess I can nearly double the speed in the above video once tuned in. It's using an open source program called PyPose and NUKE (Nearly Universal Kinematics Engine) to implement 3 DOF Inverse Kinematics for the walking gaits. It's an easy to use GUI that allows you to punch in parameters about your 3dof Quadruped or Hexapod robot, walk through a calibration guide, and it will export a ready to go Arduino Sketch for you to use with the ArbotiX. Very powerful system and easy to get up and running. Building the robot itself took about 10 hours including CNC time, and literally the software took no more than an hour or so. All of this software and the ArbotiX itself was created by Vanadium Labs.
The robot is built out of 12 RX-64 Dynamixels and a custom frame built from 2mm 5052 Aluminum, over a weekend. I'm powering it with a 4S 1900mAh LiPo pack. Control is via a handheld gamepad style Arduino-compatible controller over an Xbee wireless connection. Oh, and those are not 'usable' wheels on the end of the feet, they dont spin and are just used to create a convenient rubber contact point at the end of the tibias. Laid out it's about 90cm across, when standing it's about 60cm wide, and weighs in at 3kg.
Given that I have a bunch of available I/O, I might also experiment with autonomous navigation for this quad.
Anyway, that's all for now. I'll keep updating this as I make progress.
Very cool 4 legged walker, they seem to be pretty tough to make compared to 6 legs. Are those wheels on the bottoms of the legs? Whats the thought behind that design decision?
Sideways strafing should actually be just as quick as the forward and reverse walking gaits since the robot is more or less symmetrical.
The wheels aren’t functional (they don’t spin), just a simple way to create rubber contact points between the tibia plates.
Honestly the NUKE software + ArbotiX made this thing a walk in the park to get moving, I only had to modify the Sketch that was exported to tune the robot’s gait a bit. All the IK + control solution was already taken care of for me.
They really aren’t any more difficult than a hex – as long as you move the legs quickly. If the legs move very slowly, then yes, a quad will often fall towards that, but if you keep the COG low and move the legs quickly, it works just fine.
-Fergs (Creator of ArbotiX/NUKE, and guy who has never built a hex, cause he’s too cheap to buy the extra 2 legs)
You could use AX-12s, like Issy, the original NUKE powered quad. The robotis servos have the ability to return their position to the host controller, something cheaper servos lack (and even something a number of more expensive servos lack). NUKE won’t work here, because we can’t capture things like the minimum/maximum position, or the neutrals. Robotis servos also use a serial bus instead of PWM - so NUKE is setup for that as well.
If you’re tyring to use cheap PWM servos, you’d probably have better luck using something like an SSC-3/Basic Atom and hacking the Pheonix IK.
Hope to see more of it!