Miniature Robotic Fish Research Articles

A Magnetically Actuated Miniature Robotic Fish with the Flexible Tail Fin

A Magnetically Actuated Miniature Robotic Fish with the Flexible Tail Fin

A magnetically controlled soft miniature robotic fish with a flexible skeleton inspired by zebrafish

The untethered miniature swimming robot actuation and control is difficult as the robot size becomes smaller, due to limitations of feasible miniaturized on-board components. Nature provides much inspiration for developing miniature robot. Here, a new artificial untethered miniature robotic fish with a flexible magnetic skeleton and soft body that achieve controlled locomotion under the water through an external magnetic field is presented. The soft body of the shuttle-shaped structure microrobot was manufactured from pure Ecoflex, while the skeleton for magnetic actuation was manufactured from Ecoflex and NdFeB composites in a certain ratio and was endowed with a special magnetization profile. Microrobots that experience external magnetic fields are able to swim underwater and have environmental adaptations that include the flexibility to traverse aquatic plants area and crushed stone terrain. The robot also exhibits friendly interactivity and camouflage ability to get close to the zebrafish without scaring them. Moreover, the soft miniature robotic fish could be used to study the impacts of the morphology and kinematics changing in zebrafish populations.

Behavioral Teleporting of Individual Ethograms onto Inanimate Robots: Experiments on Social Interactions in Live Zebrafish.

SummarySocial behavior is widespread in the animal kingdom, and it remarkably influences human personal and professional lives. However, a thorough understanding of the mechanisms underlying social behavior is elusive. Integrating the seemingly different fields of robotics and preclinical research could bring new insight on social behavior. Toward this aim, we established “behavioral teleporting” as an experimental solution to independently manipulate multiple factors underpinning social interactions. Behavioral teleporting consists of real-time transfer of the complete ethogram of a live zebrafish onto a remotely-located robotic replica. Through parallel and simultaneous behavioral teleporting, we studied the interaction between two live fish swimming in remotely-located tanks: each live fish interacted with an inanimate robot that mirrored the behavior of the other fish, and the morphology of each robot was independently tailored. Our results indicate that behavioral teleporting can preserve natural interaction between two live animals, while allowing fine control over morphological features that modulate social behavior.

Toward a Maneuverable Miniature Robotic Fish Equipped With a Novel Magnetic Actuator System

Most existing robotic fish have a large body size driven by servo motor system, while conventional small-sized actuators hardly generate a high swimming performance. This paper reports a miniature untethered robotic fish, whose body length is 69 mm. In particular, a newly designed magnetic actuator system (MAS) is equipped, which guarantees both small-sized dimension and flexibility of the robot. More specifically, the magnetic field generated by a permanent magnet is first investigated based on Biot–Savart law. Then, a novel tail-beating rhythm called magnetically actuated pulse width modulation (MAPWM) is modeled for the new actuator system. Further, an MAPWM-based control method is presented, in which the duty ratio of MAPWAM is innovatively utilized to realize the turning maneuvers for the first time. In addition, Lagrangian method is employed to establish the dynamic model to assess the MAPWM-based control method and the turning performance of the robotic fish. To further improve the maneuverability, the effect of a shape-variable caudal fin is analyzed based on computational fluid dynamics and the built dynamic model. Finally, combined with the MAS, the MAPWM-based control method, and the optimally selected caudal fin, extensive aquatic experiments are conducted on the robotic prototype. The results indicate that the developed miniature robotic fish achieves a considerably higher level of maneuverability in terms of turning radius when compared to swimming robots with equivalent dimensions.

A dual caudal-fin miniature robotic fish with an integrated oscillation and jet propulsive mechanism

This paper presents the development of a biomimetic robotic fish that uses an integrated oscillation and jet propulsive mechanism to enable good swimming performance for small robotic fish. The designed robotic fish is driven by two caudal fins that flap oppositely, which are equipped in parallel at the fish tail. The propulsive mechanism of dual caudal fins is characterized by using numerical analysis, in which the distance between the two caudal fins is a key factor to the integrated mechanism and plays an important role to swimming performance. This finding has been further verified by experiments performed on a miniature robotic fish prototype with 100 mm length and 30 mm diameter. Experimental results have demonstrated the influence of the distance between the two caudal fins to swimming performance. The designed miniature robotic fish can swim stably and efficiently while exhibiting good motion maneuverability such as turning and braking. The developed robotic fish, with advantages of excellent swimming performance and small size, can be potentially used for monitoring and exploration in the underwater environment.

Design and Implementation of a Magnetically Actuated Miniature Robotic Fish

At present, most of bio-inspired robotic fish are designed with large sizes and actuated by electric motors. In this paper, an 89-mm-long robotic fish is designed and built, which is capable of swimming fast and turning flexibly. This miniature robotic fish is intended to be used as a tool for animal behavioral research and special underwater missions. Compared with traditional design, the propulsion system is characterized by no motor, which is a magnetic actuator. Bluetooth low energy is utilized for remote control, allowing convenient operation via smart devices. By means of law of electromagnetic induction, the relationship between current and magnetic induction intensity is explored. Further, a novel tail-beat rhythm for magnetic actuator is proposed. Meanwhile, a dynamic modeling of fishlike swimming is constructed based on a Lagrange approach to analyze its propulsive performance. Finally, aquatic experiments verify the effectiveness of the formulated magnetically actuated design scheme along with the conducted theoretical analyses.

Design and characterization of a miniature free-swimming robotic fish based on multi-material 3D printing

Research in animal behavior is increasingly benefiting from the field of robotics, whereby robots are being continuously integrated in a number of hypothesis-driven studies. A variety of robotic fish have been designed after the morphophysiology of live fish to study social behavior. Of the current design factors limiting the mimicry of live fish, size is a critical drawback, with available robotic fish generally exceeding the size of popular fish species for laboratory experiments. Here, we present the design and testing of a novel free-swimming miniature robotic fish for animal-robot studies. The robotic fish capitalizes on recent advances in multi-material three-dimensional printing that afford the integration of a range of material properties in a single print task. This capability has been leveraged in a novel design of a robotic fish, where waterproofing and kinematic functionalities are incorporated in the robotic fish. Particle image velocimetry is leveraged to systematically examine thrust production, and independent experiments are conducted in a water tunnel to evaluate drag. This information is utilized to aid the study of the forward locomotion of the robotic fish, through reduced-order modeling and experiments. Swimming efficiency and turning maneuverability is demonstrated through target experiments. This robotic fish prototype is envisaged as a tool for animal-robot interaction studies, overcoming size limitations of current design.

Infiltrating the zebrafish swarm: design, implementation and experimental tests of a miniature robotic fish lure for fish–robot interaction studies

Robotic fish are nowadays developed for various types of research, such as bio-inspiredrobotics, biomimetics and animal behavior studies. In the context of our research on the social interactions of the zebrafish Danio Rerio, we developed a miniature robotic fish lure for direct underwater interaction with the living fish. This remotely controlled and waterproof device has a total length of 7.5 cm with the same size ratio as zebrafish and is able to beat its tail with different frequencies and amplitudes, while following the group of living animals using a mobile robot moving outside water that is coupled with the robotic lure using magnets. The robotic lure is also equipped with a rechargeable battery and can be used autonomously underwater for experiments of up to 1 h. We performed experiments with the robot moving inside an aquarium with living fish to analyze its impact on the zebrafish behavior. We found that the beating rate of the tail increased the attractiveness of the lure among the zebrafish shoal. We also demonstrated that the lure could influence a collective decision of the zebrafish shoal, the swimming direction, when moving with a constant linear speed inside a circular corridor. This new robotic fish design and the experimental results are promising for the field of fish---robot interaction.

Design and Control of a Single-Motor-Actuated Robotic Fish Capable of Fast Swimming and Maneuverability

This paper deals with a novel fast swimming robotic fish capable of high maneuverability and yet with less joints. On the basis of prior work on a single-motor-actuated miniature robotic fish, we mainly stress three aspects: mechanical design, motion analysis, and posture control to strike a tradeoff between speediness and maneuverability. Specifically, an improved mechanical structure endows the robot with large thrust and increased range of movements. Motion analysis offers useful guidance to parameter settings of steady swimming. Besides, sine-based functions responsible for generating traveling waves in conjunction with an analysis of parameter variation of oscillation amplitude of the fish tail serve the purpose to determine the posture of the robotic fish. Underwater tests on straight swimming and different turns demonstrate the effectiveness of the proposed methods and mechatronic designs. Remarkably, the robot attained a maximum swimming speed of 1.14 m/s (corresponding to 3.07 body lengths per second) in forward swimming, a turning rate of approximately 90 °/s in normal turns, and a turning rate of approximately 63.8 °/s in hybrid turns.

An Adaptive and Online Underwater Image Processing Algorithm Implemented on Miniature Biomimetic Robotic Fish

This paper proposes a novel underwater image processing approach for different targets detection and preliminary positioning of a miniature robotic fish with low computational resources. A key aspect of our approach is that the image processing algorithm is performed online, i.e., while swimming, rather than as an offline process. Another key aspect is that the algorithm distinguishes the targets adaptively within large distance range. Specifically, considering the poor quality of underwater image as well as the low computational resources of the robot, a real-time image preprocessing algorithm, named accelerated automatic color equalization (AACE) model, is first adopted to improve color contrasts and sharpness of borders of the image. Further, HSV-based adaptive threshold segmentation, lump detection, reflection elimination and landmark matching are executed successively in a robust way for locating the target and calculating the distance between the robot and target. A series of relevant experiments with the robotic fish are conducted systematically to demonstrate that the proposed image processing approach is adaptive, efficient and real-time for online applications of the vision-based miniature swimming robots.

Controlling a robotic fish with a smart phone

Recently, mobile devices such as Apple’s iDevices have acquired the ability to host a variety of functions beyond merely initiating and receiving telephone calls. These devices have great potential for educational applications, especially when integrated with disparate technologies, such as environmental sensors, microscopes, and robotics. In this work, we present the development of an iDevice application and communication hardware for interacting with a miniature robotic fish. The application includes a user interface for controlling the robot’s motion, a detailed tutorial featuring an animated fish, and a link to information about scientific research using the robot. This platform has been field-tested with children in a broad age range and refined based on their feedback. The application has been found to be significantly easier to use than a traditional joystick controller by a survey of middle school children.

Design, Modeling, and Characterization of a Miniature Robotic Fish for Research and Education in Biomimetics and Bioinspiration

In this paper, we present the design of a biomimetic robotic fish with a modular caudal fin and analyze its performance. The robot's propulsion system is experimentally characterized for different caudal fin geometries by using an ad hoc thrust-measurement system. The static thrust produced by the vibrating tail is expressed in terms of the oscillatory Reynolds number and compared with similar findings in the literature. Nonlinear vibrations of the propulsive tail are modeled using modal analysis and classical results from the study of large vibrations of slender cylinders in fluids. This analysis allows for computing the oscillatory Reynolds number in terms of the input parameters to the tail vibration. Free-swimming experiments are performed to investigate the performance and maneuverability of the robot and correlate static thrust with terminal speed. This robotic platform is currently being used in ethorobotics research for investigating collective behavior of gregarious fish species and in educational fun-science activities for K-12 students.

A marsupial robotic fish team: Design, motion and cooperation

A bio-inspired marsupial robotic fish system composed of heterogeneous robotic fish is proposed in this paper. A miniature robotic fish, as the daughter robotic fish, can adapt to some narrow space, while the mother robotic fish, with a cabin to transport the daughter, possesses a powerful movement ability to improve the mobility and endurance of the team. The structures for mimicking bio-motion and the method for fishlike-motion are presented. A typical task of daughter-mother following is given to show the cooperation of the team. A motion model of free swimming is built based on the Lagrangian function, and the coupled dynamic and kinematic functions are calculated based on the relation between the generalized force and fluid force. Then, a neural network is trained through the data generated from this model to get a predictive yaw controller, which can control the orientation by a different offset of each link. The daughter robotic fish adopts a dynamic light source tracking approach to follow the mother, and a heterogeneous communication-based finite state machine is presented for task modeling. Experiments are carried out to verify the system.