“They observed that many quadrupedal, mammalian animals feature a distinguished functional three-segment front leg and hind leg design, and proposed a “pantograph” leg abstraction for robotic research.”
- MIT Cheetah
1 DOF (degree of freedom). 1 motor. Miranda wants jointed legs, and I don’t want to work out inverse kinematics, so this looks ideal. Maybe a bit complicated still.
The simpler force diagram:
Kinematic primitives for walking and trotting gaits of a quadruped robot with compliant legs (Alexander Badri-Spröwitz et al, 2014)Compliance is a feature, made possible by springs typically.
A homemade attempt here with the Mojo robot of the Totally Not Evil Robot Army. Their robot only uses 9g servos, and can’t quite pick itself up.
I did an initial design with what I had around, and it turns out compliance is a delicate balance. Too much spring, and it just mangles itself up. Too little spring and it can’t lift off the ground.
Further iterations removed the springs, which were too tight by far, and used cable ties to straighten the legs, but the weight of the robot is a little bit too much for the knee joints.
I will likely leave it until I have a 3d printer, some better springs, and will give it another try with more tools and materials available. Maybe even hydraulics, some day,
Some more research required, too.