The fish fin is primarily composed of muscle tissue and the peduncle joint, which work together to enable flexible and efficient movement. Similarly, the fins of robotic fish are designed to mimic this structure, with the motor system being widely used to drive their motion [1], [2]. Among these, permanent magnet synchronous motors (PMSM) are the most common configuration. In this configuration, the stator generates a rotating magnetic field that drives the rotor, which contains permanent magnets, simulating the function of muscles. This approach provides high magnetic energy density and minimal energy loss. The bearings between the rotor and stator act as joints, but they restrict movement to a fixed rotational degree of freedom. Using a fixed rotary motor to drive the fish tail makes it difficult to replicate the compliance of the “muscle + joint” system, and often results in an oversized motor-driven fin power unit. Small bionic robotic fish platforms often use motor-driven fins as the primary propulsion mechanism. Yu et al. developed a bionic sailfish robot using multiple motors to independently drive the dorsal and caudal fins, enabling coordinated fin motion for high-performance swimming [3]. Korkmaz et al. employed a series of motors to simulate the oscillations of a fish’s body, optimizing the oscillation patterns to control swimming dynamics [4]. Zhou et al. constructed a manta ray-like robot with three motors driving one of the manta ray’s wings, with the motors working in tandem to replicate various swimming modes [5]. Masoomi et al. created a tuna-like robotic fish driven by a single motor that actuates a multi-link tail mechanism to generate undulatory motion for propulsion [6]. However, the reliance on motors and linkage mechanisms for generating fin oscillations often leads to larger overall volume and more complex structure, limiting space for more efficient sensors or additional payloads, such as batteries.