Low power consumption and activation voltage combined with high flexibility and minimal weight make Ionic Polymer Metal Composites (IPMCs) well-suited for miniaturized underwater propulsion systems. In this series of papers, we comprehensively discuss the flow field induced by an IPMC strip vibrating in a quiescent aqueous environment by performing complementary physical experiments and numerical simulations. The experimental results are presented in this paper. Planar particle image velocimetry is used to measure the time-averaged flow field of a vibrating IPMC. The momentum transferred to the fluid is computed to estimate the mean thrust generated by the vibrating actuator. We find that the mean thrust increases with the Reynolds number, defined by the maximum tip speed and IPMC length, and is only marginally affected by the relative vibration amplitude. Detailed understanding of the flow environment induced by a vibrating IPMC can guide the optimization of IPMC-based propulsion systems for bio-mimetic robotic swimmers.

Ionic Polymer Metal Composite (IPMC) actuators have shown promise as miniature underwater propulsors due to their high flexibility, reduced weight, and low activation voltage and power consumption. In this second of two papers, we discuss numerical simulations of the flow of a viscous fluid generated by a two-dimensional cantilever IPMC actuator vibrating along its fundamental mode shape. We compute the thrust produced by the actuator as a function of its oscillation frequency and maximum tip displacement and show that it is correlated to vortex shedding. We find that vorticity production is prominent at the IPMC tip and increases as the oscillation frequency increases. We analyze the lateral force and the moment exerted by the IPMC on the surrounding fluid. Further, we study the power transferred by the vibrating IPMC to the encompassing fluid. The findings are validated via comparison with the experimental results presented in part 1 of this series.

Reported are advances made in connection with modeling of ionic polymeric metal composite (IPMC) plates undergoing large deformation under an imposed dynamic electric field. Analysis, design and prototyping of sensing or/and actuating plates made with IPMCs requires analytical models of the utilized materials and structures. This paper presents recent advances made towards the development of a computational implementation of a general theory for describing such systems in a way that allows accurate prediction of their behavior within their state space. Continuum mechanics, irreversible thermodynamics, and electrodynamics are utilized to derive the general four dimensional multi-physics field equations of materials used for artificial muscle applications. These applications are particularly important in terms of creating data sheets, thin data keyboards as well as flat speakers made with IPMC plates. The system of governing partial differential equations describing the state evolution of large deflection IPMC plates is derived. The system of these electro-hygro-thermally modified Von-Karman non-linear equations are solved numerically through an adaptive finite element approach through perspectives of geometrical and material nonlinearities. The preliminary results are presented for the case of finite deformation of an IPMC plate.

Ionic polymer-metal composites (IPMCs) are soft materials that can generate large deformation under a low voltage. IPMCs have many potential applications in biomedical, robotic and micro/nano manipulation systems. In this paper, we first present a distributed, nonlinear circuit model for IPMC, which incorporates the nonlinear capacitance, the nonlinear DC resistance, and the effect of surface resistance. The bending displacement is proportional to the total stored charge in IPMC. After discretizing the model in the length direction, we obtain a multiple-segment model which can be represented in the state space for nonlinear control design. The model is validated using experimental data, and we show that a one-segment model can predict the current and displacement response reasonably well. A model-based nonlinear controller is proposed for IPMC actuators, where feedback linearization is applied. Simulation results show that model-based nonlinear controller delivers better performance than a traditional PI controller in terms of the tracking error, control effort, and robustness to sensing noises.

In this paper, we study the free-locomotion of a miniature bio-mimetic underwater vehicle inspired by carangiform swimming fish. The vehicle is propelled by a vibrating Ionic Polymer Metal Composite (IPMC) attached to a compliant passive fin. The IPMC vibration is remotely controlled through the vehicle’s onboard electronics that consists of a small-sized battery pack, an H-Bridge circuit, and a wireless module. The planar motion of the vehicle body is described using rigid-body dynamics. Hydrodynamic effects, such as added mass and damping, are included in the model to enable a thorough description of the vehicle’s surge, sway, and yaw motions. The time-varying actions exerted by the vibrating IPMC on the vehicle body, including thrust, lift, and moment, are estimated by combining force and vibration measurements with reduced order modeling based on modal analysis. The model predictions are validated through experimental results on the planar motion of the fish-like robotic swimmer.

An ionic polymer-metal composite (IPMC) is an electroactive material that bends when electrically stimulated and generates electric current when bent. In this paper we investigate a coupled IPMC sensor-actuator using both the sensing and actuation properties of these electroactive materials. We describe the design of a coupled IPMC sensor-actuator, the feedback controller and the experimental evaluation of the system. Experimental results show the feasibility of closed-loop control of IPMC actuator with a mechanically coupled IPMC sensor.