A GIM-Based Biomimetic Learning Approach for Motion Generation of a Multi-Joint Robotic Fish

In this paper, we propose a biomimetic learning approach for motion generation of a multi-joint robotic fish. Based on a multi-joint robotic fish model, two basic Carangiform swimming patterns, namely ＂cruise＂ and ＂C sharp turning＂, are extracted as training samples from the observations of real fish swimming. A General Internal Model （GIM）, which is an imitation of Central Pattern Generator （CPG） in nerve systems, is adopted to learn and to regenerate coordinated fish behaviors. By virtue of the universal function approximation ability and the temporal/spatial scalabilities of GIM, the proposed learning approach is able to generate the same or similar fish swimming patterns by tuning two parameters. The learned swimming patterns are implemented on a multi-joint robotic fish in experiments. The experiment results verify the effectiveness of the biomimetic learning approach in generating and modifying locomotion patterns for the robotic fish.

Design and Experiments of a Robotic Fish Imitating Cow-Nosed Ray

The cow-nosed ray is studied as natural sample of a flapping-foil robotic fish.Body structure, motion discipline, and dynamicfoil deformation of cow-nosed ray are analyzed.Based on the analysis results, a robotic fish imitating cow-nosed ray,named Robo-ray Ⅱ, mainly composed of soft body, flexible ribs and pneumatic artificial muscles, is developed.Structure andswimming morphology of the robotic prototype are as that of a normal cow-nosed ray in nature.Key propulsion parameters ofRobo-ray Ⅱ at normal conditions, including the St Number at linear swimming, thrust coefficient at towing are studied throughexperiments.The suitable driving parameters are confirmed considering the efficiency and swimming velocity.Swimmingvelocity of 0.16 m·s’and thrust coefficient of 0.56 in maximum are achieved in experiments.

Kinematics Modeling and Experiments of Pectoral Oscillation Propulsion Robotic Fish

A robotic fish driven by oscillating fins, 'Cownose Ray-I', is developed, which is in dorsoventrally flattened shape without a tail. The robotic fish is composed of a body and two lateral fins. A three-factor kinematic model is established and used in the design of a mechanism. By controlling the three kinematic parameters, the robotic fish can accelerate and maneuver. Forward velocity is dependent on the largest amplitude and the number of waves in the fins, while the relative contribution of fin beat frequency to the forward velocity of the robotic fish is different from the usual result. On the other hand, experimental results on maneuvering show that phase difference has a stronger effect on swerving than the largest amplitude to some extent. In addition, as propulsion waves pass from the trailing edge to the leading edge, the robotic fish attains a backward velocity of 0. 15 m·s^(-1).

Parametric Research of Experiments on a Carangiform Robotic Fish

In this paper, a carangiform robotic fish with 4-DoF （degree of freedom） tail has been developed. The robotic fish has capability of swimming under two modes that are radio control and autonomous swimming. Experiments were conducted to investigate the influences of characteristic parameters including the frequency, the amplitude, the wave length, the phase difference and the coefficient on forward velocity. The experimental results shown that the swimming performance of the robotic fish is affected mostly by the characteristic parameters observed.

Learning from Fish: Kinematics and Experimental Hydrodynamics for Roboticists

Over the past 20 years, experimental analyses of the biomechanics of locomotion in fishes have generated a number of key findings that are relevant to the construction of biomimetic fish robots. In this paper, we present 16 results from recent experimental research on the mechanics, kinematics, fluid dynamics, and control of fish locomotion that summarize recent work on fish biomechanics. The findings and principles that have emerged from biomechanical studies of fish locomotion provide important insights into the functional design of fishes and suggest specific design features relevant to construction of robotic fish-inspired vehicles that underlie the high locomotor performance exhibited by fishes.

A 3D Simulator for Autonomous Robotic Fish

This paper presents a 3D simulator used for studying the motion control and autonomous navigation of robotic fish. The simulator’s system structure and computation flow are presented. Simplified kinematics and hydrodynamics models for a virtual robotic fish are proposed. Many other object models are created for water, obstacles, sonar sensors and a swimming pool. Experimental results show that the simulator provides a realistic and convenient way to develop autonomous navigation algorithms for robotic fish.

Fault-Tolerant Control of a CPG-Governed Robotic Fish

Fault tolerance is essential for the maneuverability of self-propelled biomimetic robotic fish in real-world aquatic applications.This paper explores the fault-tolerance control problem of a free-swimming robotic fish with multiple moving joints and a stuck tail joint.The created control system is composed of two main components:a feedback controller and a feedforward compensator.Specifically,the bio-inspired central pattern generator-based feedback controller is designed to make the robotic fish robust to external disturbances,while the feedforward compensator speeds up the convergence of the overall control system.Simulations are performed for control system analysis and performance validation of the faulty robotic fish.The experimental results demonstrate that the proposed fault-tolerant control method is able to effectively regulate the faulty robotic fish,allowing it to complete the desired motion in the presence of damage and thereby improving both the stability and the lifetime of the real robotic system.

Biologically Inspired Behaviour Design for Autonomous Robotic Fish

Behaviour-based approach plays a key role for mobile robots to operate safely in unknown or dynamically changing environments. We have developed a hybrid control architecture for our autonomous robotic fish that consists of three layers： cognitive, behaviour and swim pattern. In this paper, we describe some main design issues of the behaviour layer, which is the centre of the layered control architecture of our robotic fish. Fuzzy logic control （FLC） is adopted here to design individual behaviours. Simulation and real experiments are presented to show the feasibility and the performance of the designed behaviour layer.

Electromagnetic drive system of robotic fish

With the aim to apply the electric fish into practice to assist coal mine water disaster life detection and rescue work, based on the analysis on swing propulsion movements of tail fin, this paper integrates the electromagnet technology with tail fin drive system by analyzing how the fish swims with tail fin under the law of progression. The principle, structure, and drive signals of tail fin electromagnetic drive are researched, the enforced situation of fish under eIectromagnetic driving modes are analyzed, and the experimental plat-form of tail fin electromagnetic drive is established. The best distance between electro- magnet and armature, which can realize the swing of tail fin, was researched in the experiment under water. The robotic fish structure parameters of tail fin electromagnetic drive was finalized by theoretical analysis and experimental measurement.

Effect of an Artificial Caudal Fin on the Performance of a Biomimetic Fish Robot Propelled by Piezoelectric Actuators

This paper addresses the design of a biomimetic fish robot actuated by piezoeeramic actuators and the effect of artificial caudal fins on the fish robot＇s performance. The limited bending displacement produced by a lightweight piezocomposite actuator was amplified and transformed into a large tail beat motion by means of a linkage system. Caudal fins that mimic the shape of a mackerel fin were fabricated for the purpose of examining the effect of caudal fm characteristics on thrust production at an operating frequency range. The thickness distribution of a real mackerel＇s fin was measured and used to design artificial caudal fins. The thrust performance of the biomimetic fish robot propelled by fins of various thicknesses was examined in terms of the Strouhal number, the Froude number, the Reynolds number, and the power consumption. For the same fm area and aspect ratio, an artificial caudal fin with a distributed thickness shows the best forward speed and the least power consumption.

Design and Implementation of Paired Pectoral Fins Locomotion of Labriform Fish Applied to a Fish Robot

In present,there are increasing interests in the research on mechanical and control system of underwater vehicles.These ongoing research efforts are motivated by more pervasive applications of such vehicles including seabed oil and gas explorations, scientific deep ocean surveys,military purposes,ecological and water environmental studies,and also entertainments. However,the performance of underwater vehicles with screw type propellers is not prospective in terms of its efficiency and maneuverability.The main weaknesses of this kind of propellers are the production of vortices and sudden generation of thrust forces which make the control of the position and motion difficult. On the other hand,fishes and other aquatic animals are efficient swimmers,posses high maneuverability,are able to follow trajectories,can efficiently stabilize themselves in currents and surges,create less wakes than currently used underwater vehicle, and also have a noiseless propulsion.The fish's locomotion mechanism is mainly controlled by its caudal fin and paired pectoral fins.They are classified into Body and/or Caudal Fin(BCF)and Median and/or paired Pectoral Fins(MPF).The study of highly efficient swimming mechanisms of fish can inspire a better underwater vehicles thruster design and its mechanism. There are few studies on underwater vehicles or fish robots using paired pectoral fins as thruster.The work presented in this paper represents a contribution in this area covering study,design and implementation of locomotion mechanisms of paired pectoral fins in a fish robot.The performance and viability of the biomimetic method for underwater vehicles are highlighted through in-water experiment of a robotic fish.

Propulsive Velocity Optimization of 3-Joint Fish Robot Using Genetic-Hill Climbing Algorithm

Underwater robot is a new research field which is emerging quickly in recent years.Previous researches in this field focus on Remotely Operated Vehicles(ROVs),Autonomous Underwater Vehicles(AUVs),underwater manipulators,etc.Fish robot, which is a new type of underwater biomimetic robot,has attracted great attention because of its silence in moving and energy efficiency compared to conventional propeller-oriented propulsive mechanism. However,most of researches on fish robots have been carried out via empirical or experimental approaches,not based on dynamic optimality.In this paper,we proposed an analytical optimization approach which can guarantee the maximum propulsive velocity of fish robot in the given parametric conditions.First,a dynamic model of 3-joint(4 links)carangiform fish robot is derived,using which the influences of parameters of input torque functions,such as amplitude,frequency and phase difference,on its velocity are investigated by simulation.Second,the maximum velocity of the fish robot is optimized by combining Genetic Algorithm(GA)and Hill Climbing Algorithm(HCA).GA is used to generate the initial optimal parameters of the input functions of the system.Then,the parameters are optimized again by HCA to ensure that the final set of parameters is the'near'global optimization.Finally,both simulations and primitive experiments are carried out to prove the feasibility of the proposed method.

Thrust Analysis of a Fish Robot Actuated by Piezoceramic Composite Actuators

In this work, a three-dimensional （3D） Computational Fluid Dynamics （CFD） model was built to simulate the tail fin motion of a fish robot actuated by a piezoceramic composite actuator, and to determine the maximum thrust tail-beat frequency. A simulation of the tail fin at a tail-beat frequency was performed to confirm measured thrust data from a previous study. The computed and measured thrusts were in good agreement. A series of thrust simulations were conducted for various tail-beat frequencies to confirm the maximum thrust frequency that was obtained from thrust measurements in the previous study. The largest thrust was calculated at a tail-beat frequency of 3.7 Hz and vortices around the tail were fully separated. The calculated maximum thrust tail-beat frequency was in good agreement with the measured frequency. Flow characteristics during tail fin motion were examined to explain why the largest thrust occurred at this particular tail-beat frequency.

Research on the Swing of the Body of Two-Joint Robot Fish

The disadvantages caused by the swing of a fish body were analyzed. The coordinate system of a two-joint robot fish was built. The hydrodynamic analysis of robot fish was developed. The dynamic simulation of a two-joint robot fish was carried out with the ADAMS software. The relationship between the swing of fish body and the mass distribution of robot fish, the relationship between the swing of fish body and the swing frequency of tail, were gained. The impact of the swing of fish body on the kinematic parameters of tail fin was analyzed. Three methods to restrain the swing of fish body were presented and discussed.

Simplified propulsive model for biomimetic robot fish and its experimental validation

As a combination of bio-mechanism and engineering technology, robot fish has become a multidisci- plinary research that mainly involves both hydrodynamics-based control and actuation technology. This paper presents a simplified propulsive model for carangiform propulsion, which is a swimming mode suitable for high speed and high efficiency. The carangiform motion is modeled as an N-joint nscillating mechanism that is composed of two basic components： the streamlined fish body represented by a planar spline curve and its hmate caudal tail by an oscillating foil. The speed of fish＇s straight swimming is adjusted by modulating the joint＇s oscillating frequency, and its orientation is tuned by different joint＇s deflection. The results from actual experiment showed that the proposed simplified propulsive model could be a viable eandidate for application in aquatic： swimming vehicles.

3-D Locomotion control for a biomimetic robot fish

This paper concerns with 3-D locomotion control methods for a biomimetic robot fish. The system architecture of the fish is firstly presented based on a physical model of carangiform fish. The robot fish has a flexible body, a rigid caudal fin and a pair of pectoral fins, driven by several servomotors. The motion control of the robot fish are then divided into speed control, orientation control, submerge control and transient motion control, corresponding algorithms are detailed respectively. Finally, experiments and analyses on a 4-link, radio-controlled robot fish prototype with 3-D locomotion show its good performance.

Mechanical design and implementation of a new biomimetic robot fish

A mechanical design method of mbet fish is introduced in this paper. Based on this method, an autonomous 3-Dimension （3D） locomotion mbet fish with two pectoral fins and a caudal fin is developed. The pectoral fin mechanism has 3 degrees of freedom （3-DOFs）, which enables the mbet fish to realize yawing and pitching motions by controlling two pectoral fins. And the eandal fin mechanism is designed based on fish body wave curve fitting. The forward velocity can be adjusted by changing the eandal mechanism＇ s oscillating frequency. Finally a physical implementation of the robot fish and experimental results are given.

Motion Control Algorithms for a Free-swimming Biomimetic Robot Fish

A practical motion control strategy for a radio-controlled, 4-link and free-swimmingbiomimetic robot fish is presented. Based on control performance of the fish the fish s motion controltask is decomposed into on-line speed control and orientation control. The speed control algorithm isimplemented by using piecewise control, and orientation control is realized by fuzzy logic. Combiningwith step control and fuzzy control, a point-to-point (PTP) control algorithm is proposed and appliedto the closed-loop experimental system that uses a vision-based position sensing subsystem to providefeedback. Experiments confirm the reliability and e?ectiveness of the presented algorithms.

A Bionic Neural Network for Fish-Robot Locomotion

A bionic neural network for fish-robot locomotion is presented. The bionic neural network inspired from fish neural net- work consists of one high level controller and one chain of central pattern generators （CPGs）. Each CPG contains a nonlinear neural Zhang oscillator which shows properties similar to sine-cosine model. Simulation re, suits show that the bionic neural network presents a good performance in controlling the fish-robot to execute various motions such as startup, stop, forward swimming, backward swimming, turn right and turn left.