This paper presents a novel robotic fish, iSplash-I, with full-body coordination and high performance carangiform swimming motion. The proposed full-body length swimming motion coordinates anterior, mid-body and posterior displacements in an attempt to reduce the large kinematic errors in the existing free swimming robotic fish. It optimizes forces around the center of mass and initiates the starting moment of added mass upstream. A novel mechanical drive system was devised operating in the two swimming patterns. Experimental results show, that the proposed carangiform swimming motion approach has significantly outperformed the traditional posterior confined undulatory swimming pattern approach in terms of the speed measured in body lengths/ second, achieving a maximum velocity of 3.4BL/s and consistently generating a velocity of 2.8BL/s at 6.6Hz.

This paper presents a millimeter scale robotic fish, namely iSplash-MICRO, able to accurately generate the posterior undulatory pattern of the carangiform swimming mode, at intensively high frequencies. Furthermore an investigation into anterior stabilization was made in an attempt to reduce the large kinematic errors and optimize forces around the center of mass. Applying large scale dorsal and pelvic fins relative to body size enabled predictable optimization of the anterior and posterior displacements. During the field trials, the small fish with a length of 50mm has generated an equivalent average maximum velocity to real fish, measured in body lengths/ second (BL/s), greatly improving previous man-made systems, achieving a consistent free swimming speed of 10.4BL/s (0.52m/s) at 19Hz with a low energy consumption of 0.8 Watts.

This paper introduces a new robotic fish, iSplash-II, capable of outperforming real carangiform fish in terms of average maximum velocity (measured in body lengths/ second) and endurance, the duration that top speed is maintained. A new fabrication technique and mechanical drive system were developed, effectively transmitting large forces at high frequencies to obtain high-speed propulsion. The lateral and thrust forces were optimized around the center of mass, generating accurate kinematic displacements and greatly increasing the magnitude of added mass. The prototype, with a length of 32cm has significantly increased the linear swimming speed of robotic fish, achieving consistent untethered stabilized swimming speeds of 11.6BL/s (i.e. 3.7m/s), with a frequency of 20Hz.