Design and actuation optimization of a 4-axes biped robot for walking and running

Several French laboratories, joint in the CNRS Project "Control of Legged Robots", have defined a biped robot intended to experiment walking and running gaits. This biped is made of one trunk and two legs without feet, animated by means of four active articulations. This paper describes the design of the prototype, closely combining technological considerations and dynamics ones. The geometrical parameters and actuation characteristics are defined with the aim of generating walking and running gaits with rather large velocities. Each gait is synthesised with optimization criterion including the energy consideration with respect to actuator performances. During the single support phase and the flight phase, the biped is under-actuated. The synthesis of the corresponding trajectories is carried out by means of a local optimization method, and the cyclic constraints being handled as equality constraints. The optimal gear ratio of the speed reducers is computed.