Biped dynamic walker modeling and control for underactuated gait cycle

A biped dynamic walker with two legs and two feet capable of walking in double support phase and allowing starting the gait cycle from rest position is proposed. The walker is actuated at the ankle joints alone with no hip actuator, fully actuated in double support phase, and unactuated in single support phase. Assuming a static configuration at the start of each single support phase, fixed point information for the gait cycle at various step lengths is extracted and represented with four parameters of a cubic polynomial. This is used as the end configuration for the position controller’s reference target in the double support phase. Actuation at the ankles considers the unilateral constraints at the front and rear feet. Even with trajectory tracking controller, low cost of transport is achieved by ensuring no negative power inputs during actuation. A proportional feedback controller is employed for cycle convergence, and the stability of gait cycles, disturbance handling, and energetic efficiency for various step lengths is shown through simulations. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature