I'm building a quadruped robot a-la Boston Dynamics/MIT Cheetah. I'm not really happy with the state of legged robots in terms of affordability and performance. I've found there are two classes of robots; robots in the first sacrifice mobility for the sake of driving cost down, either limiting the legs to move in a single plane, or using lower cost, but extremely slow servo motors [1][2][3][4]. Robots in the second class don't compromise the performance of the robot, but cost at the very least $6000 [5][6][7]. I'm working on using an underactuated leg (3 degrees of freedom, but only 2 actuators instead of the typically used 3) to bring the cost down, as actuators are the largest cost center for these robots. It should also (hypothetically) have better performance than other robots which use 2 actuators per leg but constrain them to a single plane.

[1]: https://hackaday.io/project/171456-diy-hobby-servos-quadrupe...

[2]: https://stanfordstudentrobotics.org/pupper

[3]: https://open-dynamic-robot-initiative.github.io/

[4]: https://stanfordstudentrobotics.org/doggo

[5]: https://hackaday.io/project/176487-k3lso-quadruped

[6]: https://build-its.blogspot.com/2019/12/the-mini-cheetah-robo...

[7]: https://shop.bostondynamics.com/spot?cclcl=en_US&pid=aDl6g00...