生物模倣ソフト魚ロボットの研究開発

In nature, the environment varies from day to day. Through natural selection and competition law of survival of the fittest, the winning creatures survive and their species are able to retain and persist in nature. Based on this fact, creatures existent in nature have their unique features and advantages adapt to the surrounding environment. In recent years, many researches focused on the features of the creatures in nature have been done actively to clarify their morphology and functions and apply the morphology and functions to various fields. Among these researches, the development of the biomimetic robots based on mimicking the creature’s structures and functions has become an active field in robotics recently. In the research, the development of biomimetic robotic fish is focused. So far, there are many researches on biomimetic robotic fish, but improvement on motion performances and efficiency is still an important issue for robot development. Specially, on the biomimetic soft robotic fish utilizing the flexibility of fishes, the developments have been done by the trial and error approach. That is, the design and control method of soft robotic fish has not been established currently. Therefore, it motives us to investigate the design and control of soft robotic fish by numerical simulation that takes into account the interaction between flexible structure and surrounding fluid to develop the biomimetic soft robotic fish with high performance. In order to develop the biomimetic soft robotic fish with high performance, the basic design method and corresponding numerical simulation system are firstly proposed and constructed in this dissertation. Then, based on finite element method (FEM), modelling of soft robotic fish by mimicking the soft structure and driving mechanism of fishes is carried out. The propulsion motion and propulsive force of the soft robotic fish are investigated through two kinds of numerical analyses. One is the modal and transient analysis considering the surrounding fluid as acoustic fluid. The propulsion mode and amplitude of the propulsion motion of soft robotic fish corresponding directly to the propulsion mechanism and motion performance of the robotic fish can be investigated. The other is the fluid-structure interaction (FSI) analysis. The interaction between soft robot structure and surrounding fluid including the dissipation due to fluid viscosity and influence of wake performance around the soft robotic fish are taken into account. From FSI analysis, the hydrodynamic performances of the soft robotic fish can be obtained for investigating its propulsion motion. It is possible to further improve the performance of the soft robotic fish through its design and control based on FSI analysis. Besides, based on coupling analysis by using acoustic fluid, the turning motion control of the soft robotic fish is investigated by its propulsion modes in the fluid. In order to investigate the feasibility of modelling method and numerical simulation analysis on design and control of the biomimetic soft robotic fish, the performance evaluation is carried out by comparison between the simulation and experiment on an actual prototype. Finally, the optimization and improvement are performed for developing the biomimetic soft robotic fish with higher performance based on verified coupling analysis considering the fluid as acoustic fluid, and corresponding performance evaluation on new robot prototype is presented. The performance improvement of the soft robotic fish is confirmed through the new robot prototype. The dissertation consists of six chapters and the main contents are shown as follows. Chapter 1 is an introduction. The background and relative previous work about biomimetic soft robotic fish are briefly reviewed. It summarizes the current research status and problems of biomimetic soft robotic fish, and describes the purposes of this research. Chapter 2 presents the design method, procedures and numerical simulation system in the present research for developing the biomimetic soft robotic fish with high performance. Different from previous development method, our purpose is how to design and control the soft robotic fish by utilizing interaction between the flexible structure and surrounding fluid effectively based on numerical simulations. Therefore, it is necessary to model a fish-like soft robot structure including soft actuators and an enclosed fluid. Besides, by the numerical analysis considering the interaction between flexible structure and fluid, the fish-like propulsion motion should be realized and established, and then the robot structure and control inputs are needed to be optimized for performance improvement. In order to meet these requirements of designing and developing the optimal soft robotic fish, the design method based on modelling, simulation analysis and improvement is presented and the numerical simulation system for soft robotic fish is built. In the simulation system, modelling of soft robotic fish, modal and transient analysis considering the enclosed fluid as acoustic fluid are firstly described based on FEM to realize the fish-like propulsion motion with large amplitude for the soft robotic fish. Then, the FSI analysis is performed to describe and establish the hydrodynamic performances of the soft robotic fish. Based on this numerical simulation system, it is possible to develop the biomimetic soft robotic fish with high performance effectively by optimization of design and control of the soft robotic fish. Chapter 3 describes the modelling and numerical analysis of biomimetic soft robotic fish by using the method presented in Chapter 2. The soft robotic fish uses the piezoelectric fiber composite (PFC) as soft actuator. Firstly, the relationships between the input voltage and generated stress of the PFC are derived. The generated stress can be applied on soft structure to investigate the motion performance of the soft robotic fish. To support the driving model of the PFC, the corresponding experiments on simple beam model are carried out. By comparing the simulation results with experimental results, the effectiveness of the driving model is verified. Then, the modal analysis in which the fluid is considered as acoustic fluid is performed. The structural mode frequencies and mode shapes of the soft robotic fish in the fluid are calculated. By comparing these modes’ motion with those of the real fishes, the fish-like propulsion mode is identified to realize the corresponding propulsion motion of the soft robotic fish. Furthermore, based on the verified driving model of soft actuator, the amplitude of the main propulsion motion of soft robotic fish is calculated. Through FSI analysis, the relationships of driving frequencies of input signal with propulsive force and displacement of propulsion motion, and vortex distribution in the wake around the soft robotic fish are investigated for the case of fixing robot head. Besides, the motion control of soft robot is investigated to realize turning motion in the fluid. Through controlling the input voltage amplitude on soft actuators of the robot, turning right and turning left motion are identified in the swimming when the input voltage amplitudes on two actuators are in asymmetric distribution. Chapter 4 is experiment evaluation. In order to validate the results of numerical simulation analysis described in Chapter 3, the mode shapes, amplitude of propulsion motion, propulsive force and vortex distribution around soft robotic fish for the case of fixing robot head, and turning motion are measured by using actual robot prototype. The present simulation results are congruent with experiments. By the results, the effectiveness of the modelling method and numerical analysis used in the research is verified and they are useful to predict the propulsion characteristics of the soft robotic fish in the fluid for performance improvement. Chapter 5 develops a new soft robotic fish with high performance based on above modelling method and numerical analysis by optimization. Firstly, the structural parameters of the robot are allowed to vary within a range and the amplitude of the propulsion motion for the soft robot is calculated for different parameters by the numerical analysis. Then the structural parameters of the robot capable of propulsion motion with largeramplitude are chosen for improvement. Based on this result, new soft robot is designed and evaluated by experiments. From the experimental results of the new soft robot, it is confirmed that the higher swimming speed, better fish-like swimming performance and larger turning velocity are realized. It can be said that the new soft robotic fish has been developed successfully for improvement. Chapter 6 summarizes the conclusions and future works of this research.電気通信大学201

3D locomotion biomimetic robot fish with haptic feedback

This thesis developed a biomimetic robot fish and built a novel haptic robot fish system based on the kinematic modelling and three-dimentional computational fluid dynamic (CFD) hydrodynamic analysis. The most important contribution is the successful CFD simulation of the robot fish, supporting users in understanding the hydrodynamic properties around it

Underwater Vehicles

For the latest twenty to thirty years, a significant number of AUVs has been created for the solving of wide spectrum of scientific and applied tasks of ocean development and research. For the short time period the AUVs have shown the efficiency at performance of complex search and inspection works and opened a number of new important applications. Initially the information about AUVs had mainly review-advertising character but now more attention is paid to practical achievements, problems and systems technologies. AUVs are losing their prototype status and have become a fully operational, reliable and effective tool and modern multi-purpose AUVs represent the new class of underwater robotic objects with inherent tasks and practical applications, particular features of technology, systems structure and functional properties

Development of Modular Bio-Inspired Autonomous Underwater Vehicle for Close Subsea Asset Inspection

To reduce human risk and maintenance costs, Autonomous Underwater Vehicles (AUVs) are involved in subsea inspections and measurements for a wide range of marine industries such as offshore wind farms and other underwater infrastructure. Most of these inspections may require levels of manoeuvrability similar to what can be achieved by tethered vehicles, called Remotely Operated Vehicles (ROVs). To extend AUV intervention time and perform closer inspection in constrained spaces, AUVs need to be more efficient and flexible by being able to undulate around physical constraints. A biomimetic fish-like AUV known as RoboFish has been designed to mimic propulsion techniques observed in nature to provide high thrust efficiency and agility to navigate its way autonomously around complex underwater structures. Building upon advances in acoustic communications, computer vision, electronics and autonomy technologies, RoboFish aims to provide a solution to such critical inspections. This paper introduces the first RoboFish prototype that comprises cost-effective 3D printed modules joined together with innovative magnetic coupling joints and a modular software framework. Initial testing shows that the preliminary working prototype is functional in terms of water-tightness, propulsion, body control and communication using acoustics, with visual localisation and mapping capability

Autonomous Grasping Using Novel Distance Estimator

This paper introduces a novel distance estimator using monocular vision for autonomous underwater grasping. The presented method is also applicable to topside grasping operations. The estimator is developed for robot manipulators with a monocular camera placed near the gripper. The fact that the camera is attached near the gripper makes it possible to design a method for capturing images from different positions, as the relative position change can be measured. The presented system can estimate relative distance to an object of unknown size with good precision. The manipulator applied in the presented work is the SeaArm-2, a fully electric underwater small modular manipulator. The manipulator is unique in its integrated monocular camera in the end-effector module, and its design facilitates the use of different end-effector tools. The camera is used for supervision, object detection, and tracking. The distance estimator was validated in a laboratory setting through autonomous grasping experiments. The manipulator was able to search for and find, estimate the relative distance of, grasp, and retrieve the relevant object in 12 out of 12 trials.publishedVersio

Energy Based Control System Designs for Underactuated Robot Fish Propulsion

In nature through millions of years of evolution fish and cetaceans have developed fast efficient and highly manoeuvrable methods of marine propulsion. A recent explosion in demand for sub sea robotics, for conducting tasks such as sub sea exploration and survey has left developers desiring to capture some of the novel mechanisms evolved by fish and cetaceans to increase the efficiency of speed and manoeuvrability of sub sea robots. Research has revealed that interactions with vortices and other unsteady fluid effects play a significant role in the efficiency of fish and cetaceans. However attempts to duplicate this with robotic fish have been limited by the difficulty of predicting or sensing such uncertain fluid effects. This study aims to develop a gait generation method for a robotic fish with a degree of passivity which could allow the body to dynamically interact with and potentially synchronise with vortices within the flow without the need to actually sense them. In this study this is achieved through the development of a novel energy based gait generation tactic, where the gait of the robotic fish is determined through regulation of the state energy rather than absolute state position. Rather than treating fluid interactions as undesirable disturbances and `fighting' them to maintain a rigid geometric defined gait, energy based control allows the disturbances to the system generated by vortices in the surrounding flow to contribute to the energy of the system and hence the dynamic motion. Three different energy controllers are presented within this thesis, a deadbeat energy controller equivalent to an analytically optimised model predictive controller, a $H_\infty$ disturbance rejecting controller with a novel gradient decent optimisation and finally a error feedback controller with a novel alternative error metric. The controllers were tested on a robotic fish simulation platform developed within this project. The simulation platform consisted of the solution of a series of ordinary differential equations for solid body dynamics coupled with a finite element incompressible fluid dynamic simulation of the surrounding flow. results demonstrated the effectiveness of the energy based control approach and illustrate the importance of choice of controller in performance

Animal-Robot Interactions: Electrocommunication, Sensory Ecology, and Group Dynamics in a Mormyrid Weakly Electric Fish

Mormyrid weakly electric fish possess a specialized electrosensory system. During the process of active electrolocation, these animals perceive self-generated electric organ dis-charges (EOD) and are thereby able to detect objects in their nearby environment. The EOD is a short, biphasic pulse, which is simultaneously used to communicate with conspe-cifics. There are two principles according to which information exchange occurs during electrocommunication. The waveform of the EOD constitutes a relatively stable identity marker that signals species, gender, and status of an individual. In contrast, the temporal sequence of inter-discharge intervals (IDI) is highly variable and encodes context-specific information. Modifications of IDI-duration not only alter the instantaneous discharge fre-quency but also enable the generation of specific signaling patterns and interactive dis-charge sequences. One such interactive discharge behavior is the so-called echo response, during which a fish responds with a constant latency of only a few milliseconds to the EOD of a conspecific. Animals can synchronize their signaling sequences by mutually generating echoes to each other's signals over a coherent period. Although active electrolocation and electrocommunication are mediated by different types of electroreceptor organs and neural pathways, an unambiguous assignment of electromotor behavior to only one of the two functions is often problematic. In this thesis, the significance of IDI-based signaling sequences during motor and electro-motor interactions of the mormyrid fish Mormyrus rume proboscirostris were investigated. To this end, different electrical playback sequences of species-specific EODs were generated via mobile fish dummies, and the motor and electromotor responses of live fish were analyzed. In Part One of this thesis, electrocommunication strategies of the fish were analyzed, and particularly the functions of double pulses, discharge regularizations, and echo responses were examined in an adaptive context. Double pulses were classified as an aggressive mo-tivation signal, whereas regularizations may have a communicative function during the early stages of the sequential assessment of a potential opponent. In this context, discharge synchronization by means of echo responses may enable a mutual assessment for the net benefit of both contestants. Because echo responses occur in various behavioral contexts, and artificial echoes of the dummy evoked increased echoing by the fish, it was hypothesized that the echo response serves a more general purpose by enabling mutual allocation of social attention between two fish. In Part Two of this thesis, a biomimetic robotic fish was designed to investigate the senso-ry basis on which fish followed the dummy. It was shown that electrical playback signals induced following-behavior in live fish, whereas biomimetic motility patterns had no ef-fect. By subsequently reducing the mobile dummy to only the electric signaling sequence from the perspective of the fish, it could be shown that passive perception of electrical communication signals is also involved in mediating the spatial coordination of social in-teractions. This passive perception is likely mediated by the same electroreceptor organs that are used during electrocommunication. The EOD can therefore be considered to be an essential social stimulus that makes it possible to integrate a dummy into a group of weak-ly electric fish as an artificial conspecific. The influence of an interactively signaling mobile dummy fish on small groups of up to four individuals was investigated in Part Three of this thesis. Typical schooling behavior was a rare occurrence in this context. However, EOD-synchronizations through mutual echo responses between two fish, or between a fish and the interactive dummy, were fre-quently observed during social interactions in small groups. Motor interactions during synchronization episodes supported the hypothesis that mormyrids may use discharge synchronizations between individuals to allocate social attention, and the echo response may thus adopt a particularly useful function during communication in groups.Schwach elektrische Fisch aus der Familie der Mormyriden verfügen über ein spezialisier-tes elektrosensorisches Sinnessystem. In einem Prozess, der als aktive Elektroortung be-zeichnet wird, sind diese Tiere in der Lage, selbstgenerierte elektrische Organentladungen (EOD) wahrzunehmen, und dadurch Objekte in ihrer unmittelbaren Nähe zu detektieren. Das EOD ist ein kurzer bipolarer Puls, der gleichzeitig auch zur Kommunikation mit Artge-nossen dient. Informationsaustausch während der Elektrokommunikation basiert auf zwei verschiedenen Prinzipien: Die Wellenform des EOD stellt einen relativ konstanten Identi-tätsmarker dar, der beispielsweise Art, Geschlecht und Status eines Individuums signali-siert. Die zeitliche Abfolge der Intervalle zwischen den EODs ist hingegen höchst variabel und kodiert kontextspezifische Information. Durch Modifikation der Intervalldauer ändert sich nicht nur die Entladungsfrequenz, sondern es können auch spezifische Signalmuster und interaktive Entladungssequenzen generiert werden. Ein interaktives Entladungsver-halten stellt beispielsweise die Echoantwort dar, bei der ein Fisch mit einer konstanten Latenz von wenigen Millisekunden auf das EOD eines Artgenossen reagiert. Zwei Tiere können ihre Entladungssequenzen synchronisieren, indem sie ihre Signale über einen kohärenten Zeitraum gegenseitig mit Echos beantworten. Obwohl aktive Elektroortung und Elektrokommunikation über unterschiedliche Rezeptororgansysteme und neuronale Pfade vermittelt werden, ist eine eindeutige Zuordnung der elektromotorischen Verhal-tensäußerungen der Fische zu nur einer der beiden Funktionen oft problematisch. In der vorliegenden Arbeit wurde die Bedeutung intervallbasierter EOD-Sequenzen für motorische und elektromotorische Interaktionen des Mormyriden Mormyrus rume proboscirostris erforscht. Hierzu wurden verschiedene elektrische Playbacksequenzen artspezifischer EODs generiert und durch mobile Fischattrappen wiedergegeben. Die mo-torischen und elektromotorischen Verhaltensreaktionen der Fische wurden analysiert. Im ersten Teil der Arbeit wurden Elektrokommunikationsstrategien der Fische analysiert und die adaptive Funktion insbesondere von Doppelpulsen, Entladungsregularisierungen und Echoantworten untersucht. Doppelpulse wurden als aggressives Motivationssignal kategorisiert, wohingegen die Kommunikationsfunktion von Regularisierungen im gegen-seitigen Einschätzen zu Beginn einer kompetitiven Begegnung zu liegen scheint. Entla-dungssynchronisation durch gegenseitige Echoantworten kann dabei eine Einschätzung des Gegenübers zum Vorteil beider Parteien erleichtern. Da Echoantworten in verschiede-nen Verhaltenssituationen auftreten und artifizielle Echoantworten der Attrappe vermehrt zu Echos vonseiten der Fische führten, wurde postuliert, dass die Echoantwort eine generellere Funktion bei der Fokussierung gegenseitiger sozialer Aufmerksamkeit über-nehmen kann. Im zweiten Teil der Arbeit wurde ein biomimetischer Fischroboter konstruiert, um zu untersuchen, auf welcher sensorischen Grundlage die Fische der Attrappe folgen. Es konnte gezeigt werden, dass elektrische Playbacksignale, nicht aber biomimetische Bewe-gungsmuster, Folgeverhalten der Fische induzieren. In einem weiteren Schritt konnte durch die Reduktion der Attrappe auf die elektrischen Signalsequenzen aus der Perspektive der Versuchsfische gezeigt werden, dass passive Wahrnehmung elektrischer Kommu-nikationssignale auch bei der räumlichen Koordination sozialer Interaktionen von Bedeu-tung ist. Dies wird mutmaßlich über die gleichen Rezeptororgane vermittelt, die auch für die Elektrokommunikation verantwortlich sind. Das EOD kann daher als ein soziales Signal betrachtet werden, das es ermöglicht, eine Attrappe als künstlichen Artgenossen in eine Gruppe schwach elektrischer Fische zu integrieren. Der Einfluss einer elektrisch interaktiven mobilen Fischattrappe auf kleine Gruppen von bis zu vier Individuen wurde im dritten Teil der Arbeit getestet. Typisches Schwarmver-halten konnte in diesem Zusammenhang nur selten beobachtet werden. In kleinen Gruppen kam es während sozialer Interaktionen jedoch häufig zu EOD-Synchronisationen durch Echoantworten zwischen zwei Fischen, oder zwischen einem Fisch und der interaktiven Attrappe. Motorische Verhaltensinteraktionen im Zeitraum dieser Synchronisationen stützen die Hypothese, dass Mormyriden durch elektrische Entladungssynchronisation soziale Aufmerksamkeit zwischen Individuen herstellen können, und die Echoantwort somit besonders in Gruppen eine nützliche Kommunikationsfunktion übernehmen kann

Underwater Robots Part I: Current Systems and Problem Pose

International audienceThis paper constitutes the first part of a general overview of underwater robotics. The second part is titled: Underwater Robots Part II: existing solutions and open issues