Unlike biological systems, which can use muscles, robots that try to imitate them don’t have particularly fast, powerful, compact linear actuators available. This puts walking robots at a particular disadvantage, since they can’t spread their actuators along a limb and have to place them right at the joint. [Food for Robots] took on the challenge of building such a joint-mounted actuator, and shared the results in a recent video.
[Food for Robots] is building a walking robot, so he needed a compact, lightweight, and backdrivable actuator capable of producing 20 Newton-meters of torque. He’d previously built a largely 3D-printed actuator, but when he tried to exceed 10 Nm of torque with it, various parts kept breaking. He therefore machined the second iteration out of aluminum; since it didn’t need to be 3D printed, he switched from a Capstan drive to a planetary gearbox. The gearbox sits in the center of the actuator, inside the stator, and uses several stacked layers of gears to increase strength within the limits of a small CNC.
