Figure 1.

Overview of the system with the reflex controller and the plant, the musculoskeletal model. The musculoskeletal model is standing on a platform, that is perturbed in the sagittal plane by a random square wave signal. The musculoskeletal model has nine degrees of freedom, but effectively six are used because the control is the same in the left and right leg. Each leg is operated by nine muscles. Each muscle is controlled by feedforward activation and reflex loops based on force and length information. These reflex loops are only active when the center of mass (COM) is outside of a dead zone inside the base of support. Three different controllers are created: the base model with length and force feedback, a length feedback model, and a force feedback model. The control outputs nine different signals, one for each muscle in both legs.