Research On Fish Variable Stiffness: A Review

High-performance swimming of fish is related to fish species, body shape, physiological structure, and the fluid environment which they interact. Among them, biomechanical experiments show that the stiffness distribution of spine, skin, fin and other parts of fish is uneven, and fish can adjust the stiffness of body through muscle fibers, collagen and other muscle tissues. In this paper, the related biological experiments are described, and the stiffness distribution and variation rules of each part of actual fish are summarized. Model experiments and simulation are complementary to the biological experiments, the application of these methods in variable stiffness in fish is summarized. The stiffness models of fish from three aspects are summarized to carry out systematic analysis. In order to explore the swimming effect of variable stiffness fish in actual fluid environment, scholars designed variable stiffness robotic fish to simulate. This paper classifies these methods of adjusting stiffness, compares and summarizes the characteristics of each method, and provides reference for researchers to explore the mechanism of efficient swimming of fish and design energy-saving and flexible underwater robot.