Design and Implementation of a Novel Robot Fish with Active and Compliant Propulsion Mechanism

Although methods about building fish-like robots have attracted much research in recent years, new techniques are still required for developing superior robot fish. This paper presents a novel robot fish propelled by an active compliant propulsion mechanism. The key innovation is the combination of an active wire-driven mechanism with a soft compliant tail to accomplish subcarangiform swimming (i.e., swimming with an “S” motion). Additionally, an effective design methodology based on a 3R pseudo-rigid-body model is proposed to design the compliant tail. First, the mathematical model based on the design methodology was derived and computer simulations were performed. Second, a prototype was fabricated and numerous experimental studies were conducted. The experiments demonstrated that the predictions of the mathematical model matched the testing results. Compared with existing robot fishes which use multi-link structure with each joint being actuated by one motor, the new robot fish has several advantages: it is simple in structure, easy to control, and capable of high speed swimming and maneuverable swimming, the maximum swimming speed reached 2.15 body length per second and the instantaneous maximum turning speed is 269°/s. Furthermore, the design methodology presented in the paper can be also used in other applications such as flexible probe of medical devices and soft manipulators.