The objective of this project is the development a natural size biped robot as light as possible and with a few number of degrees of freedom. Existing humanoid robots have a high number of degrees of freedom that in most cases makes having a high weight on the legs due to the weight of the corresponding motors and actuators . This fact makes humanoid robots are very complex and expensive. This project proposes a novel design of biped robot. New mechanisms in order to develop an appropriate step (gait) by passive control techniques dynamics had been developed.