Abstract: As for fishlike robot propulsion, there exist a number of possible motion modes to achieve a prescribed swimming velocity. But for optimum efficiency, there is only one mode. The motion planning on optimum efficiency of fishlike robot is presented to achieve a prescribed velocity. The steady state swimming can be realized and the intrinsic rules for the steady velocity, power consumption and propulsive efficiency with respect to different motion modes are revealed by using the numerical simulation method. The problem of motion planning is formulated to find the motion mode that maximizes the efficiency over the motion space, which is defined by oscillating frequency f and maximum amplitude Amax, subject to the prescribed velocity. The results show that the motion mode with lower f and higher Amax can obtain optimum efficiency while subjected to the prescribed velocity. Taking 2 m•s–1 for example, the value of efficiency for the motion mode with lower f and higher Amax increases by 37.7% compared with that of higher f and lower Amax, and this trend is clearly reflected by the three-dimensional flow structure. The findings are of great significance to the acquirement of efficient motion laws, understanding of swimming mechanism and the propulsive motion design for fishlike robot.

Key words: Fishlike robot, Flow field structure, Motion planning, Optimum efficiency, Prescribed velocity