We described a tensegrity robotic fish and detailed its overall structure, stiffness, and mechatronics. The main flexible structure of the robotic fish body was composed with a series of rigid segments linked with tensegrity joints by means of tension elements. Each rigid segment can rotate around tensegrity-compliant joint and have no direct contact with each other. The dominant vibrational mode of the tensegrity robotic fish can be excited by a single harmonic input to mimic the desired kinematics of locomotion. For our tensegrity robotic fish, the experimental results showed that its maximum stride length was about 0.5 body length per cycle; its Strouhal number was roughly between 0.45 and 0.55 near the biological data of carangiform swimmers. Two different vibrational modes that can be achieved would be demonstrated by the harmonic analysis technique. The results indicated that the swimming performance can be improved by using tensegrity joints.
Keywords: swimming performance; tensegrity joint; tensegrity robotic fish.