Hybrid serial-parallel leg design

The idea is from a group at Disney Research, by Kevin Gim et al. - a serial-parallel leg design that allows most of the actuators to be placed in the hip (there are no motors in the knee, and only one motor in each foot), resulting in a lighter structure. The robot introduced in their paper is relatively small, making use of servo motors. For the larger size design in our project, we replace the servos with BLDC motors.