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A pinboard by
Saurab Verma

Ph. D. candidate, National University of Singapore

PINBOARD SUMMARY

This work focuses on attaining precise position control of an autonomous robotic fish.

Robotic fish are proposed to be the next generation of Autonomous Underwater Vehicles (AUVs), by learning several desirable features (such as higher agility, lower noise to the surroundings and higher power efficiencies) from the biological fishes. Furthermore, such features are generally not attainable in rotary-propeller based AUVs. As a result, there have been several developments in the field of robotic fish system over the past two decades.

Although, precise control of robotic fish position has never been implemented due to the underlying problems such as drift in water environment, communication limitations, complex motion of robotic fish, etc. Yet, precision position control is essential in making the robot perform various tasks in complex underwater environments.

In order to attain the position control, in this work, many developments are performed, essentially summarized by the following:

  1. A robotic fish prototype and swimming environment is constructed to study and test the technologies in a controlled environment,
  2. the dynamics of the robotic fish is heavily examined to understand how the robot moves,
  3. on-board sensors such as on vision camera and Inertial Measurement Unit are developed for attaining immediate and reliable feedback of the surrounding environment,
  4. on-board processing electronic hardware is designed which supports mobility of the robotic fish without need for human guidance, and
  5. novel algorithms such as robust motion controls, sensor data fusion and artificial intelligence is developed in order to make the robotic fish autonomous i.e. the robotic fish can move, locate and perform tasks based on its own decisions and understanding of the surroundings.
8 ITEMS PINNED

Influence of robotic shoal size, configuration, and activity on zebrafish behavior in a free-swimming environment.

Abstract: In animal studies, robots have been recently used as a valid tool for testing a wide spectrum of hypotheses. These robots often exploit visual or auditory cues to modulate animal behavior. The propensity of zebrafish, a model organism in biological studies, toward fish with similar color patterns and shape has been leveraged to design biologically inspired robots that successfully attract zebrafish in preference tests. With an aim of extending the application of such robots to field studies, here, we investigate the response of zebrafish to multiple robotic fish swimming at different speeds and in varying arrangements. A soft real-time multi-target tracking and control system remotely steers the robots in circular trajectories during the experimental trials. Our findings indicate a complex behavioral response of zebrafish to biologically inspired robots. More robots produce a significant change in salient measures of stress, with a fast robot swimming alone causing more freezing and erratic activity than two robots swimming slowly together. In addition, fish spend more time in the proximity of a robot when they swim far apart than when the robots swim close to each other. Increase in the number of robots also significantly alters the degree of alignment of fish motion with a robot. Results from this study are expected to advance our understanding of robot perception by live animals and aid in hypothesis-driven studies in unconstrained free-swimming environments.

Pub.: 23 Sep '14, Pinned: 29 Aug '17

Hydrodynamics of a robotic fish tail: effects of the caudal peduncle, fin ray motions and the flow speed.

Abstract: Recent advances in understanding fish locomotion with robotic devices have included the use of biomimetic flapping based and fin undulatory locomotion based robots, treating two locomotions separately from each other. However, in most fish species, patterns of active movements of fins occur in concert with the body undulatory deformation during swimming. In this paper, we describe a biomimetic robotic caudal fin programmed with individually actuated fin rays to mimic the fin motion of the Bluegill Sunfish (Lepomis macrochirus) and coupled with heave and pitch oscillatory motions adding to the robot to mimic the peduncle motion which is derived from the undulatory fish body. Multiple-axis force and digital particle image velocimetry (DPIV) experiments from both the vertical and horizontal planes behind the robotic model were conducted under different motion programs and flow speeds. We found that both mean thrust and lift could be altered by changing the phase difference (φ) from 0° to 360° between the robotic caudal peduncle and the fin ray motion (spanning from 3 mN to 124 mN). Notably, DPIV results demonstrated that the caudal fin generated multiple wake flow patterns in both the vertical and horizontal planes by varying φ. Vortex jet angle and thrust impulse also varied significantly both in these two planes. In addition, the vortex shedding position along the spanwise tail direction could be shifted around the mid-sagittal position between the upper and lower lobes by changing the phase difference. We hypothesize that the fish caudal fin may serve as a flexible vectoring propeller during swimming and may be critical for the high maneuverability of fish.

Pub.: 09 Feb '16, Pinned: 29 Aug '17

Implementations of the Route Planning Scenarios for the Autonomous Robotic Fish with the Optimized Propulsion Mechanism

Abstract: Various human problems are tried to resolve with biomimetic design which imitate biological forms. A biomimetic Carangiform robotic fish provides great benefits with flexible maneuverability, high propulsion efficiency and less noisy considering classical rotary underwater vehicles. This paper presents a dynamic simulation model of the Carangiform robotic fish with flexible multi-joint propulsion mechanism considered as an artificial spine system for two swimming cases. In order to swim like a real fish, multi-joint propulsion mechanism assumed a series planar hinge joints which represent vertebras is adjusted by optimizing with a new searching method which provides precise values as direct search methods. The flapping frequency and the speed are proportional with the tail link lengths and angles of the joints. Thus, the optimization parameters are selected as end point coordinates of the joints and lengths of the each link to imitate the real travelling body wave. Two possible route planning scenarios for the robotic fish model inspired from the Carangiform motion are performed. These scenarios are summarized by two cases. Case 1 is the free swimming mode permits to go straight forward until it faces an obstacle. The fish decides to the turning direction by using decision-making process when it encounters an obstacle and finds the way to turn. In the Case 2, the fish proposes to reach the destination area along the shortest path. When faced with obstacles, it overcomes obstacles and tries to reach the target in the shortest way again.

Pub.: 06 Jul '16, Pinned: 29 Aug '17

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

Abstract: Abstract 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.AbstractRobotic 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.Danio Rerio

Pub.: 25 Jul '16, Pinned: 29 Aug '17

Precise planar motion measurement of a swimming multi-joint robotic fish

Abstract: This paper presents a method for planar motion measurement of a swimming multi-joint robotic fish. The motion of the robotic fish is captured via image sequences and a proposed tracking scheme is employed to continuously detect and track the robotic fish. The tracking scheme initially acquires a rough scope of the robotic fish and thereafter precisely locates it. Historical motion information is utilized to determine the rough scope, which can speed up the tracking process and avoid possible ambient interference. A combination of adaptive bilateral filtering and k-means clustering is then applied to segment out color markers accurately. The pose of the robotic fish is calculated in accordance with the centers of these markers. Further, we address the problem of time synchronization between the on-board motion control system of the robotic fish and the motion measurement system. To the best of our knowledge, this problem has not been tackled in previous research on robotic fish. With information about both the multi-link structure and motion law of the robotic fish, we convert the problem to a nonlinear optimization problem, which we then solve using the particle swarm optimization (PSO) algorithm. Further, smoothing splines are adopted to fit curves of poses versus time, in order to obtain a continuous motion state and alleviate the impact of noise. Velocity is acquired via a temporal derivative operation. The results of experiments conducted verify the efficacy of the proposed method. This paper presents a method for planar motion measurement of a swimming multi-joint robotic fish. The motion of the robotic fish is captured via image sequences and a proposed tracking scheme is employed to continuously detect and track the robotic fish. The tracking scheme initially acquires a rough scope of the robotic fish and thereafter precisely locates it. Historical motion information is utilized to determine the rough scope, which can speed up the tracking process and avoid possible ambient interference. A combination of adaptive bilateral filtering and k-means clustering is then applied to segment out color markers accurately. The pose of the robotic fish is calculated in accordance with the centers of these markers. Further, we address the problem of time synchronization between the on-board motion control system of the robotic fish and the motion measurement system. To the best of our knowledge, this problem has not been tackled in previous research on robotic fish. With information about both the multi-link structure and motion law of the robotic fish, we convert the problem to a nonlinear optimization problem, which we then solve using the particle swarm optimization (PSO) algorithm. Further, smoothing splines are adopted to fit curves of poses versus time, in order to obtain a continuous motion state and alleviate the impact of noise. Velocity is acquired via a temporal derivative operation. The results of experiments conducted verify the efficacy of the proposed method.

Pub.: 23 Aug '16, Pinned: 29 Aug '17

BCF swimming locomotion for autonomous underwater robots: a review and a novel solution to improve control and efficiency

Abstract: Publication date: 15 January 2017 Source:Ocean Engineering, Volume 130 Author(s): David Scaradozzi, Giacomo Palmieri, Daniele Costa, Antonio Pinelli The development of autonomous, energy efficient, underwater robots for large areas exploration has been attracting many researchers, since their use can be effective in several applications. In order to improve the propulsion efficiency, movement capability and situation awareness, last studies have been directed on biomimetic robots. Over millions of years in a vast and often hostile realm, fish have evolved swimming capabilities far superior in many ways to what has been achieved by nautical technology. Instinctively, they use their superbly streamlined bodies to exploit fluid-mechanical principles, achieving extraordinary propulsion efficiencies, acceleration and manoeuvrability. Their solutions achieved the best performances based on aspects like preys hunting and living conditions. Looking at nature for inspiration as to how design an Autonomous Underwater Vehicle can significantly improve its flexibility and efficiency. This paper presents an examination of the state of the art on biomimetic robotic fishes, underlining the reasons why bio-inspiration can be a winning move and discussing how fish swimming can be the line of sight of the future locomotion technology. The paper concludes with a novel mechanism proposal, designed to produce optimal oscillatory motion between the flexible parts constituting the hull of the robotic fish.

Pub.: 26 Dec '16, Pinned: 29 Aug '17