Abstract: Aiming at the posture control problem of three-joint biomimetic robotic fish, firstly, the hardware structure and motion control system of three-joint biomimetic robotic fish was introduced. Secondly, the coordinate system was established based on the expected posture to construct the posture error model of robotic fish. Thirdly, on the basis of cascade proportional-integral
-differential (PID) control system, the posture control algorithm of biomimetic robotic fish based on cascade PID was proposed. Finally, the algorithm simulation experiment and the entity experiment were carried out on the URWPGSim2D simulation platform and the multi-underwater robots cooperative control system platform respectively. The experimental results show that, compared with the time-varying feedback control algorithm, the simulation robotic fish based on cascade PID algorithm takes longer to reach the target posture, but the position error and direction angle error decrease, which improves the accuracy of posture control. It takes 14.4 s for the biomimetic robot fish to reach the expected posture, and the posture error is (-3 px,-4 px,0.062 rad), which basically meets the application requirements such as tracking and handling, and verifies the effectiveness of the algorithm.

Key words: robotic fish, posture control, URWPGSim2D simulation platform, multi-underwater robots cooperative control system platform