Design and Dynamic Modeling of a Multi-DOF Soft Robotic Fish with a Single Magnetic Actuator

doi:10.3901/JME.260239

Abstract

Abstract: The rapid development and widespread application of underwater soft robots are of significant importance for fields such as ocean exploration, military applications, and industrial production. However, most existing underwater soft robots rely on single actuators for single-degree-of-freedom (SDOF) motion or multiple actuators for multi-degree-of-freedom (MDOF) motion, increasing system complexity. In response, a novel soft robot fish capable of MDOF underwater motion and driven by a single magnetic actuator is presented. The magnetic actuator consists of a magnet, coil, and PET dorsal fin, while the power supply, control, and actuation systems are integrated within a soft silicone fish body to withstand harsh environments. By applying positive and negative direct currents at specific frequencies, the actuator drives the dorsal fin to provide thrust for diving. The rolling motion of the fish induces periodic deformation of the pectoral silicone fins, disturbing the water flow to propel the fish forward. Steering is achieved by adjusting the duty cycle of the dorsal fin’s driving voltage. Based on the Lagrange method, the roll motion equation of a robotic fish is established. The actual motion trajectory of the pectoral fins is simulated using a mechanical wave function. Furthermore, the dynamic models for the diving and forward motions of the robotic fish are developed by integrating the Newton-Euler formulation with the Morrison equation. Experimental data are employed to determine model parameters and validate the accuracy of the proposed models. A series of experiments—including tests on forward swimming, diving, and turning—demonstrates the fish’s MDOF underwater performance. The robotic fish achieves a forward swimming speed of 0.77 BL/s, a diving speed of 0.26 BL/s, and a minimum turning radius of 1.30 BL. Additionally, it withstands low temperatures, confirmed through tests at 2.7 ℃. This robotic fish design holds potential for flexible intelligent devices and provides new insights into soft robot design for ocean exploration.

Key words: soft robotic fish, magnetic actuator, multi-degree of freedom, dynamic modeling

CLC Number:

TP242

GUO Shihang, WANG Shenlong, HOU Jinhui, LI Yongge. Design and Dynamic Modeling of a Multi-DOF Soft Robotic Fish with a Single Magnetic Actuator[J]. Journal of Mechanical Engineering, 2026, 62(5): 215-229.

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URL: http://www.cjmenet.com.cn/EN/10.3901/JME.260239

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