Research Laboratory "Nonlinear Phenomena of Vibrating Systems" of Riga Technical University was established in 1991. Investigations made in the Laboratory are directed on studying of nonlinear phenomena of dynamic systems and further adoption of these phenomena for developing of new machines and technologies. Main results of research are checked on novelty and patented. 138 patents on inventions have been received till present time. In this report main attention is given to the inventions developed within EU Project „Robotic Fish Locomotion and Sensing” (FILOSE). One-tail and two-tail vibration propulsive devices of robotic fish with varying working area of tail are proposed (patents LV 14034, LV 14077, LV 14237, LV 14289, etc). The proposed inventions make 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.