Getting a legged robot to stay upright, especially a quadruped or biped, can be a challenging undertaking. To experiment with different approaches, [James Bruton] built robot dog test platform and is playing with “dynamic compliant simulated springs“, or in other words, using the motors to act as though they were springs and dampers..
When robotic legs are kept stiff, they tend to reduce the stability of the platform due to the sudden erratic movements of the robot, especially on uneven surfaces. With a back drivable joint arrangement, [James] is using limited holding current on the motor, and the position of the motor shaft is monitored using an encoder. When a leg experiences a resisting force, with will have some “give” and then the motor will return it to it’s intended position more slowly. Using a IMU on top of the robot, it can detect when it start leaning to a side, and then temporarily soften the other side to balance the robot.
This is quite a common technique in legged robots, but [James] does an excellent job of explaining just how it works. He hopes to use the lessons learned from the test platform to improve or redesign his already impressive OpenDog.
We’ve seen a number of quadruped robots on Hackaday recently. Including Boston Dynamics’ very expensive Spot as well as a low cost robot dog that giving its big brothers a run for their money, and doing some back flips in the process. Check out James’ video after the break. Continue reading “Making A Robotic Dog Better By Adding Springiness Without Springs”
This video of littledog doing some terrain navigaion excersizes is just hilarious. We really don’t have any technological updates since last time we mentioned him, but you should watch the video anyway. [Evan] at botjunkie pointed out how tired littledog must be to absolutely collapse at the end of each run. We started out thinking that his comment was humorous, but the bot is obviously going into a tidy configuration for carrying. As we watched, we saw that [Evan] seemed very correct. Littlebot completely collapses at the end of each run, toward the end of the video, it doesn’t even bother to fold up nicely, sprawling out in a very lifelike pose of utter exhaustion. We don’t know if this is intentional, but we think it should be.
This little walking robot caught our eye. We’ve seen tons of 4 legged bots, but the design on this probably took more effort than the electronics. The design is radially symmetrical, it can walk in any direction, turn in place, and even walk upside down. The electronics weren’t forgotten though. This little bugger manages to pull a half our of use out of each battery charging. It communicates wirelessly with a custom dual Wiimote Nunchuck setup via XBEE modules. You can find much more technical details in the captions of the pictures. We’re not positive what processing power is hidden in the bot itself, but we know there’s an Arduino in one of the nunchucks. This might be the brains of the operation leaving the hardware on the bot simply to control the servos. We really like the arc-reactor-esque power display.