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In this paper, we study the thrust performance of a biomimetic robotic swimmer that uses ionic polymer–metal composite (IPMC) as a flexible actuator in viscous and inertial flow, for a comprehensive understanding of IPMC swimmers at different scales. A hydrodynamic model based on the elongated body theory was developed. Based on image analysis, the parameters of the model were identified and simulation results were obtained. To obtain the hydrodynamic thrust performance of the robotic swimmer, we implemented a novel experimental apparatus. Systematic tests were conducted in the servo towing system to measure the self-propelled speed and thrust efficiency under different actuation of IPMC. The undulatory motions of the IPMC swimmer were identified. Experimental results demonstrated that the theoretical model can accurately predict the speed and thrust efficiency of the robotic swimmer. When the Reynolds number of the robotic swimmer was reduced to approximately 0.1%, its speed and thrust efficiency were reduced by 95.22% and 87.33% respectively. It was concluded that the robotic swimmer has a low speed and thrust efficiency when it swims in a viscous flow. Generally, the thrust performance of the robotic swimmer is determined by the kinematics and Reynolds number. In addition, the optimal actuation frequency for the thrust efficiency is greater in a viscous fluid. These results may contribute to a better understanding of the swimming performance of IPMC actuated swimmers in a distinct flow regime (viscous and inertial regime).

We implement a mackerel (Scomber scombrus) body-shaped robot, programmed to display the three most typical body/caudal fin undulatory kinematics (i.e. anguilliform, carangiform and thunniform), in order to biomimetically investigate hydrodynamic issues not easily tackled experimentally with live fish. The robotic mackerel, mounted on a servo towing system and initially at rest, can determine its self-propelled speed by measuring the external force acting upon it and allowing for the simultaneous measurement of power, flow field and self-propelled speed. Experimental results showed that the robotic swimmer with thunniform kinematics achieved a faster final swimming speed (St = 0.424) relative to those with carangiform (St = 0.43) and anguilliform kinematics (St = 0.55). The thrust efficiency, estimated from a digital particle image velocimetry (DPIV) flow field, showed that the robotic swimmer with thunniform kinematics is more efficient (47.3%) than those with carangiform (31.4%) and anguilliform kinematics (26.6%). Furthermore, the DPIV measurements illustrate that the large-scale characteristics of the flow pattern generated by the robotic swimmer with both anguilliform and carangiform kinematics were wedge-like, double-row wake structures. Additionally, a typical single-row reverse Karman vortex was produced by the robotic swimmer using thunniform kinematics. Finally, we discuss this novel force-feedback-controlled experimental method, and review the relative self-propelled hydrodynamic results of the robot when utilizing the three types of undulatory kinematics.

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Research on biomimetic robotic fish has been undertaken for more than a decade. Various robotic fish prototypes have been developed around the world. Although considerable research efforts have been devoted to understanding the underlying mechanism of fish swimming and construction of fish-like swimming machines, robotic fish have largely remained laboratory curiosities. This paper presents a robotic fish that is designed for application in real-world scenarios. The robotic fish adopts a rigid torpedo-shaped body for the housing of power, electronics, and payload. A compact parallel four-bar mechanism is designed for propulsion and maneuvering. Based on the kinematic analysis of the tail mechanism, the motion control algorithm of joints is presented. The swimming performance of the robotic fish is investigated experimentally. The swimming speed of the robotic fish can reach 1.36 m/s. The turning radius is 1.75 m. Powered by the onboard battery, the robotic fish can operate for up to 20 h. Moreover, the advantages of the biomimetic propulsion approach are shown by comparing the power efficiency and turning performance of the robotic fish with that of a screwpropelled underwater vehicle. The application of the robotic fish in a real-world probe experiment is also presented. C 2010 Wiley Periodicals, Inc.

Skid-steering mobile robots are widely used because of their simple mechanism and robustness. However, due to the complex wheel-ground interactions and the kinematic constraints, it is a challenge to understand the kinematics and dynamics of such a robotic platform. In this paper, we develop an analysis and experimental kinematic scheme for a skid-steering wheeled vehicle based-on a laser scanner sensor. The kinematics model is established based on the boundedness of the instantaneous centers of rotation (ICR) of treads on the 2D motion plane. The kinematic parameters (the ICR coefficient χ, the path curvature variable λ and robot speed v), including the effect of vehicle dynamics, are introduced to describe the kinematics model. Then, an exact but costly dynamic model is used and the simulation of this model’s stationary response for the vehicle shows a qualitative relationship for the specified parameters χ and λ. Moreover, the parameters of the kinematic model are determined based-on a laser scanner localization experimental analysis method with a skid-steering robotic platform, Pioneer P3-AT. The relationship between the ICR coefficient χ and two physical factors is studied, i.e., the radius of the path curvature λ and the robot speed v. An empirical function-based relationship between the ICR coefficient of the robot and the path parameters is derived. To validate the obtained results, it is empirically demonstrated that the proposed kinematics model significantly improves the dead-reckoning performance of this skid–steering robot.

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