Biped robots have not achieved the efficient and harmonious locomotion of the human beings, capable of walking and running on unstructured terrains, with obstacles, holes and slopes. With this in mind, researchers started the development of biomimetic solutions to control the locomotion of biped models. This work presents a new solution of motion control of bipedal robots with adaptable stiffness, by exploring effects of joint stiffness in modulating walking behavior. Further, torque adjustment is achieved through a biomimetic controller that mimics and adjusts the natural dynamics of the robot to the environment. Specifically, the torque adjustment is made using AFOs (adaptive frequency oscillator) to generate the correct equilibrium positions that will be applied to the impedance control that computes the torque of each joint. Results show that the biped model is capable of walking in several types of terrain, including flat terrain, ramps, stairs and flat terrain with obstacles.

In humans, the system that controls several biomechanical tasks has a modular organization (muscle synergies). While the muscle synergies in human walking were already studied deeply, this phenomenon in robotic system is not so explored and could bring simpler controllers requiring a minor number of parameters. So, the purpose of this work is to acquire and interpret synergies from selected joint signals in order to answer some specific research questions regarding the verification of synergistic control of a biped robot in a walking activity, e.g, the number of synergies, their activation profiles, their mechanical role, their quality to reproduce/control walking motions, etc. The selected robotic system was the Darwin-OP robot when walking both with a model based and a bio-inspired controller. Tests were performed with the simulated and real robot. The results appear to suggest that the extraction of synergies are quite useful for the robotic locomotion, since with only 2 synergies, is possible to reconstruct the signals of the studied joints. The biomechanical role for each determined synergy is described based on the functional transformation between sensorimotor signals and biomechanical output. Besides, the robustness of the determined synergies is verified in the locomotor activation pattern across strides and across speeds when the mechanical requirements do not change to a large extent.