Designing of control-oriented position controller for biomimetic underwater IPMC propulsor

The demand for underwater robots is on the rise, driven by increasing needs in oceanographic engineering and the urgent exploration of underwater resources. Traditional underwater robots face practical limitations due to their large size, high operational costs, and substantial energy requirements. However, smart material-based underwater robots offer a promising solution, thanks to their unique attributes such as low power consumption, robustness, versatility, and superior efficacy compared to conventional counterparts. This article investigates the utilization of ionic polymer metal composite (IPMC) as a propeller for underwater biomimetic propulsors, leveraging its exceptional electromechanical property of converting electrical signals into mechanical deformation and vice versa. The study focuses on modeling an underwater biomimetic propulsor utilizing IPMC as a propeller tail, mimicking body caudal fin motion (BCF) for swimming. However, the motion of IPMC in an open-loop configuration presents challenges such as irregular deformation, extended settling time, water back diffusion, and hysteresis. To address these issues, the study implements three different controller design approaches—PID, Fuzzy Logic control, and H∞ control—to effectively regulate the positioning of IPMC. The primary objective is to control the tip displacement at the tail end of the biomimetic IPMC propulsor model. A key novelty of this research lies in conducting a comprehensive comparison of the controller's performance with experimental results, assessing the accuracy and swiftness with which each controller achieves the desired output motion while mitigating the effects of noise. The study also evaluates the controller's performance across two different input signals to validate its accuracy and precision.