Effects of Passive Biarticular Muscles on Walking Performance for Bipedal Robots

The first goal of this paper is to investigate the effects of passive biarticular muscles on the walking performance of a bipedal robot. Second goal is to achieve a stable walking gait with the bipedal robot model that has these biarticular muscles. To achieve this, we first compare the optimal trajectories of a default bipedal robot model with the same model that also has biarticular springs. The comparison was made with respect to walking efficiency, speed and minimum input torque requirements criteria using direct collocation methods. We show that the model with biarticular muscles outperforms the default model in all the investigated criteria and also proper parameters for the biarticular springs can be chosen using the described optimization method. Then, we introduce a feedback+feedforward controller to track the obtained optimal trajectories with a bipedal robot with biarticular muscles. Through simulations, we show that using the proposed controller, stable walking gaits can be achieved with good tracking performances.