Locomotion through Karman Street Using Adaptive Oscillator

Living beings locomotion´s main characteristics are oscillatory motions. These motions are sustained by a full mechanical architecture of passive and active organs, controlled by means of neural networks called Central Pattern Generators. A Karman vortex Street is a repeating pattern of swirling vortices caused by the flow´s separation of a fluid passing around bluff bodies. This phenomenon is well employed by fish that can swim using energy captured from vortices. In fact, during locomotion through Karman Streets fish swims weaving in between oncoming vortices decreasing muscle activity compared to free stream swimming. Fish holding station in a laboratory created Karman Street shows a pattern of body bending that appears to be passive, a tail beat frequency in synchrony with the vortex shedding frequency and a facing vortex strategy that reduces its energetic cost compared to regular flow swimming. This paper presents a Work in Progress description about Central Pattern Generators modeled as oscillators with frequency adaptation. These artificial CPGs are used to control a simplistic robot fish. Our first objective is to synchronize the tail beat frequency with the Karman vortex Street frequency in order to mimic some characteristics of the Karman gait.Simulations of our mono-actuated robot swimming in a simplified steady state Karman Street have succeed in frequency adaptation of the tail movement to the oncoming vortices.