New designs of fin type propulsive devices of robotic fish

Dynamics of a fin type propulsive device of robotic fish moving inside water is studied. On the basis of Pontryagin's maximum principle the optimal control law for variation of additional area of vibrating tail, which ensures maximal positive impulse of motive forces acting on tail, is found. The proposed method makes it possible to minimize energy losses within operation cycles, when fin's motion is affected by water resistance forces. Thanks to that useful tractive forces increase, and operation of fin propulsive device becomes more effective. Examples on synthesis of one-tail and two-tail propulsive devices with varying working area of vibrating tail are given.