Design and Development of a Parallel Multi-Cascaded PID Control Method for the Novel Spherical Underwater Robot

Micro underwater robots operating in complex environments are susceptible to external perturbations, coupling, and uncertainties that lead to mission failure or poor maneuverability. In this paper, a parallel multi-cascaded PID control strategy was proposed for the novel Spherical Underwater Robot (SUR) to enhance the attitude stabilization and trajectory tracking. Based on the SUR kinematic and dynamic models, a multi-vector propulsion scheme was designed to realize multi-degree-of-freedom motion. Then, the performance of the SUR in the presence of nonlinear external perturbations is simulated by Simulink and the parameters of the multi-vector driving were optimized. Finally, motion experiments of the SUR in a real environment were conducted to evaluate further the effectiveness and feasibility of the proposed parallel multi-cascaded PID control system, and the experimental results validated the control accuracy of the SUR with good tracking performance during underwater operation.