Emulating a human walking gait in a double pendulum interacting with the incoming vortices

We discuss a method to impose desired trajectories on a double pendulum placed in flow. In a long-term project, we are designing a robot to provide assistance to patients with walking disabilities by manipulating the flow of water in an underwater treadmill to enable the patients to follow a desired walking trajectory. In the present work, we show this concept using a double pendulum. A cylinder forced to rotate upstream the double pendulum controls the shedding frequency and strength of the vortices that interact with the double pendulum. These vortices then interact with a hydrofoil that is attached to the double pendulum and produce trajectories very similar to the human walking gait trajectories.