Electric Cable Differential (E.C.D.)

The Electric Cable Differential (ECD) Leg was designed by Dr. Hurst for running, walking, jumping, hopping, and generally behaving in a highly dynamic manner. Large fiberglass springs are used for storing the energy of a running gait, much like the springs in a pogo stick or the tendons in a kangaroo.

The name "ECD Leg" is derived from the method of actuation and power transmission; we use electric motors, which offer much simpler and more precise computer control than pneumatic or hydraulic actuators. The motors are connected to the leg joints using steel cable wrapped around aluminum pulleys, and there are several mechanical differentials to implement the desired relationship between the electric motors, fiberglass springs, and leg joints.

There are currently two robots built using ECD Legs: A monopod, named Thumper, and a biped, named MABEL, installed in professor Jessy Grizzle's laboratory at the University of Michigan. Thumper will be used to explore the role of compliance in a running gait, while MABEL will be used to explore control theory for legged locomotion. MABEL has successfully demonstrated stable walking gaits.