Dynamic modeling and gait analysis of batoid swimming

This paper develops a dynamic model of batoid swimming for the purpose of gait analysis and feedback control design for robotic underwater vehicles. A general framework is first laid out for modeling of multi-body mechanical systems placed in an environment. The class of systems is supposed to capture dynamics of animal locomotion or mobile robots inspired by biology. The underlying mechanism of propulsion is to gain thrust from the environmental forces through periodic body movements. The framework is then applied to modeling of batoids that swim by flapping their wings. The body geometry and stiffness of the model are fixed using experimental measurements from an Atlantic ray and cownose ray. Periodic movements (gaits), that minimize the power consumption while maintaining a given swim speed, are determined from an optimal gait theory. Consistently with biological observations, it is found that an undulatory gait is optimal for the Atlantic ray with oval wings, and an oscillatory gait is optimal for the cownose ray with triangular wings.