Bionic Robotic Fish Research Articles

Asymmetrical Oscillating Morphology Hydrodynamic Performance of a Novel Bionic Pectoral Fin

This research proposes a novel bionic pectoral fin and experimentally studied the effects of the oscillation parameters on the hydrodynamic performance of a bionic experimental prototype. Inspired by manta rays, the bionic pectoral fin was simplified and modeled based on the natural pectoral fin skeleton structure and oscillation morphology of this underwater creature. A dual-degree-of-freedom bionic pectoral fin was designed. The active spatial motion was realized by the space six-link mechanism driven by two motors, and the passive deformation was achieved by carbon fiber. The motion analysis of the bionic pectoral fin proves that the pectoral fin can realize an “8”-shaped spatial trajectory. An experimental prototype was developed accordingly. The experimental prototype could flap between 0.1 Hz and 0.6 Hz and produce a maximum thrust of 20 N. The hydrodynamic performance under different oscillation parameters was studied experimentally in a water pool. The experimental results indicate that the hydrodynamic performance of the pectoral fin oscillation is closely related to the motion equation parameters including the amplitude, frequency, phase difference, and initial bias. In addition to considering the impact of parameters on thrust and lift, the influences of asymmetrical oscillation on the position of the equivalent point were also studied. The results show that the pectoral fin proposed in this research exhibited the expected spatial deformation and outstanding hydrodynamic performance. The obtained results shed light on the updated design and control of a bionic robot fish.

Three-dimensional path following control system for net cage inspection using bionic robotic fish

With the increasing impacts of overfishing and environmental pollution, the deep-sea cage culture of marine fishes has become an important direction of mariculture. In this paper, a tuna-like robotic fish with a three-dimensional helix path-following control system is designed for deep-sea net cage inspection. To mimic the flexibility of the fish’s movement, the kinematic model of the robotic fish adopts a tuna-like double-joint design with an additional thruster device at the tail. Since the descending interval control plays a critical role in deep-sea net cage inspection, the control system utilizes the proportion integration differentiation (PID) based fuzzy logic control method to control the descending interval and yaw angle during the helix path movement. A polar coordinate path definition method is also proposed to simplify the reference path definition during net cage inspection. The experimental results demonstrates that the proposed three-dimensional path-following model can conduct net inspection task in an interferential environment and move along predefined reference path.

High-Efficiency Closed-Loop Control of a Robotic Fish via Virtual Musculoskeletal Methodology

Improving propulsion efficiency holds the promise of enabling the robotic fish to work for a long time with a limited battery in its small body. In this paper, for the swimming of a bionic robotic fish, we present a virtual musculoskeletal control method from the bionic model of the joint driven by agonist muscle and antagonist muscle. A closed-loop method composed of two loops is proposed as a rule of thumb for the speed control of the robotic fish. The outer loop adjusts the swimming speed using the speed deviation; the inner loop regulates the stiffness according to the virtual muscle spindle feedback to fit the water environment. Compared with the proportion control, the evaluation results show that the virtual musculoskeletal methodology increases the efficiency by 3.4% in the steady flow and 7% in the Karman-vortex flow. This algorithm provides a new idea for the joint-space control of the bionic robots that need to reduce the energy consumption of movements.

A Liquid Metal Artificial Muscle.

Artificial muscles possess a vast potential in accelerating the development of robotics, exoskeletons, and prosthetics. Although a variety of emerging actuator technologies are reported, they suffer from several issues, such as high driving voltages, large hysteresis, and water intolerance. Here, a liquid metal artificial muscle (LMAM) is demonstrated, based on the electrochemically tunable interfacial tension of liquid metal to mimic the contraction and extension of muscles. The LMAM can work in different solutions with a wide range of pH (0-14), generating actuation strains of up to 87% at a maximum extension speed of 15 mm s-1 . More importantly, the LMAM only needs a very low driving voltage of 0.5 V. The actuating components of the LMAM are completely built from liquids, which avoids mechanical fatigue and provides actuator linkages without mechanical constraints to movement. The LMAM is used for developing several proof-of-concept applications, including controlled displays, cargo deliveries, and reconfigurable optical reflectors. The simplicity, versatility, and efficiency of the LMAM are further demonstrated by using it to actuate the caudal fin of an untethered bionic robotic fish. The presented LMAM has the potential to extend the performance space of soft actuators for applications from engineering fields to biomedical applications.

Design of Bionic Robot Fish Propelled by Two Joint Caudal Fin

The research of biomimetic robot fish has always been the focus of related fields of underwater robots. And the idea of underwater fish propulsion can be widely applied in scientific research, industrial and military fields. In this paper, a bionic tail fin propelled bionic robot fish is designed, and the corresponding program is designed and programmed through hardware circuit to realize the pipeline cruise inspection, Bluetooth communication control and the realization of image return by camera. The designed robotic fish can complete pipeline cruise and other tasks underwater.

Bionic fish design with coordinated propulsion of pectoral and caudal fins

The continuous development of the aquaculture industry is accompanied by a large amount of aquaculture wastewater discharge, which brings a series of environmental protection problems. With the call for the construction of high-quality modern marine pastures, it is imperative to enhance the research and development capabilities of marine observation/monitoring equipment and pollution reduction/monitoring equipment. At present, underwater submersibles have the characteristics of complex structure and high concealment requirements. As a typical combination of robotics and bionics, the bionic robotic fish has the characteristics of high swimming efficiency, strong mobility, and strong concealment. This project will apply the bionic robotic fish to the field of pasture construction and monitoring in oceans and other waters. A bionic fish with coordinated pectoral and caudal fins.

Development of Subcarangiform Bionic Robotic Fish Propelled by Shape Memory Alloy Actuators

In this paper, a shape memory alloy (SMA) actuated subcarangiform robotic fish has been demonstrated using a spring based propulsion mechanism. The bionic robotic fish developed using SMA spring actuators and light weight 3D printed components can be employed for under water applications. The proposed SMA spring-based design without conventional motor and other rotary actuators was able to achieve two-way shape memory effect and has reproduced the subcarangiform locomotion pattern. The positional kinematic model has been developed and the dynamics of the proposed mechanism were analysed and simulated using Automated Dynamic Analysis of Mechanical Systems (ADAMS). An open loop Arduino-relay based switching control has been adopted to control the periodic actuation of the SMA spring mechanism. The undulation of caudal fin in air and water medium has been analysed. The caudal fin and posterior body of the developed fish prototype have taken part in undulation resembling subcarangiform locomotion pattern and steady swimming was achieved in water with a forward velocity of 24.5 mm/s. The proposed design is scalable, light weight and cost effective which may be suitable for underwater surveillance application.

An untethered soft robotic fish using SMA wires and its performance analysis

The authors have developed a bionic robotic fish having a soft tail by employing intelligent materials as actuators. Two sets of shape memory alloy (SMA) wires are stitched to the two sides of the soft tail, allowing the tail to bend on either side. The designed structure is expected to have the ability to mimic the straight swimming posture of a real fish in the water, and also to turn left and right using the soft body and caudal fins (BCF propulsion). The body and the head part are designed by a 3D CAD software, whose streamline ability is verified through the fluid simulation, and are printed by a high-precision 3D printer. A micro Arduino computer is set inside the fish body for the total swimming control. The infrared (IR) communication is also installed for the detailed analysis of the swimming motion and the speed. By studying the relationship between the control signals and the swimming behaviour of the robotic fish, the performance of the swimming motion was examined for determining the parameter values to realise real-fish swimming.

Micro thrust measurement experiment and pressure field evolution of bionic robotic fish with harmonic actuation of macro fiber composites

The design and realization of underwater bionic robots actuated by smart materials have attracted growing attention in recent years. The experimental acquisition of the dynamic thrust force is crucial for the development of underwater robots. A simple micro thrust measurement system based on a decoupled lever mechanism is designed for a macro fiber composite (MFC)-actuated bionic robotic fish. The pressure field distribution and evolution associated with the thrust variation induced by the oscillating caudal fin of the robotic fish are visualized using computational fluid dynamics (CFD) technologies. A miniature MFC-actuated robotic fish that mimics the koi fish is designed. A simple decoupled lever mechanism with excellent linearity, high precision and resolution, and the ability to minimize the interference from the lateral force is proposed. Calibration results indicate that the output sensitivity of the designed measurement apparatus is 5.48 mN/V. The dynamic variations in the micro thrust generated by the robotic fish at different actuation levels are effectively captured using the proposed measurement system. Experimental results show that the MFC-actuated robotic fish obtains a maximum mean thrust of −2.95 mN in the case of the greatest tip oscillating velocity, which is consistent with Lighthill’s elongated-body theory. Moreover, for the robotic fish, the maximum instant thrust grows with an increase in the oscillating frequency. The maximum instant drag first decreases, and then increases as the actuation frequency increases. It reaches its minimum value of 0.37 mN in the case of the maximum oscillating velocity. In contrast, the variation behavior of the thrust pattern/oscillating period is the reverse to that of the maximum instant drag, and it obtains a maximum of 85.7%. The propulsion performance indexes of the robotic fish in the CFD simulations match those of experimental results for different oscillating cases. Furthermore, the distribution and evolution mechanisms of the steady pressure fields around the oscillating robotic fish are revealed. The CFD simulations demonstrate that the variations in the instant thrust could be fully determined by the distributions and intensities of the concentrated pressure regions induced by the oscillating caudal fin. The cycle-averaged velocity fields around the caudal fin are closely related to the mean thrust generated by the MFC-actuated robotic fish. Accordingly, these results may be helpful in the development of underwater bionic robots actuated by smart actuators.

Nonlinear model predictive position control for a tail-actuated robotic fish

Position control is a significant technique for the underwater application of robotic fish; however, it is also very challenging due to the underactuated property and input coupling of system dynamics. In this article, a two-stage orientation–velocity nonlinear model predictive controller is proposed to solve this problem. A scaled averaging model of tail-actuated robotic fish is constructed at first. Then, the novel strategy based on orientation and velocity control is developed as well as proved to be equivalent with position control in the sense of Lyapunov. Furthermore, a nonlinear model predictive controller with a two-stage switching strategy is designed to regulate the orientation and velocity error. Finally, the simulation results demonstrate the superiority of the proposed control algorithm compared with other methods. Particularly, there exists an interesting twist-braking behavior in simulation, which indicates that the proposed method makes better use of the system dynamics. The proposed method is efficient for not only bionic robotic fish but also other aquatic underactuated robots, which offers new insight into the position control of underwater robots.

A Novel Visual Sensor Stabilization Platform for Robotic Sharks Based on Improved LADRC and Digital Image Algorithm.

Autonomous underwater missions require the construction of a stable visual sensing system. However, acquiring continuous steady image sequences is a very challenging task for bionic robotic fish due to their tight internal space and the inherent periodic disturbance caused by the tail beating. To solve this problem, this paper proposes a modified stabilization strategy that combines mechanical devices and digital image techniques to enhance the visual sensor stability and resist periodic disturbance. More specifically, an improved window function-based linear active disturbance rejection control (LADRC) was utilized for mechanical stabilization. Furthermore, a rapid algorithm with inertial measurement units (IMUs) was implemented for digital stabilization. The experiments regarding mechanical stabilization, digital stabilization, and target recognition on the experimental platform for simulating fishlike oscillations demonstrated the effectiveness of the proposed methods. The success of these experiments provides valuable insight into the construction of underwater visual sensing systems and also establishes a solid foundation for the visual applications for robotic fish in dynamic aquatic environments.

DESIGN AND SIMULATION OF TWO-JOINT PRESSURE-DRIVEN SOFT BIONIC FISH

In order to study and design a new type of bionic robotic fish with high softness and strong environmental adaptability, imitating the shape of shark and the swimming posture of tuna fish, a bionic robotic fish with hydraulic flexible driving structure is designed. In view of the problem that the single-joint hydraulically driven flexible robotic fish has a C-shaped swing posture that does not conform to the swing rule of tuna fish, a two-joint hydraulic flexible drive is used to simulate the S-shaped swing of the fish, and the internal structure of the bionic fish is designed according to the principle of the hydraulic flexible actuator. According to the theoretical wave equation, the swing amplitude of the robotic fish is determined, the magnitude of the pressure load applied inside the flexible actuator is calculated by numerical simulation, and the driving efficiency of the hydraulic flexible actuator is analyzed and calculated. The software of finite element analysis is used to simulate the autonomous swimming process of the robotic fish in the fluid. And the autonomous cruise process of the two-joint robotic fish and the one-joint roboic fish are simulated and compared to obtain the movement postures, swimming velocity and flow field of the two robotic fishes when they autonomously cruised in the fluid. The results show that at the same frequency and tail-fin swing, the average velocity of the two-joint soft roboic fish cruising is 0.29 BL/s, which is higher than the average velocity of the the one-joint roboic fish 0.15 BL/s. And frome the velocity vector diagram, it can be concluded that the S-type swing of the two-joint roboic fish is closer to the real fish swing attitude, and a series of discrete reverse Karman Vortex Streets will be generated during the movement, so the two-joint bionic fish has a higher propulsion efficiency.

Trajectory tracking control of a bionic robotic fish based on iterative learning

A bionic robotic fish has great potential application prospect. High maneuverability swimming control of a bionic robotic fish has been one of the research hotspots in the robotic fish field. In this paper, an iterative learning method has been proposed to solve the trajectory tracking control problem of robotic fish swimming. First, a dynamic model of the multi-joint bionic robotic fish is established. By considering a three-joint robotic fish as an example, the unified expression of the dynamic equation of the three-joint bionic robotic fish is obtained by Lagrange method. Second, the iterative learning controller for controlling the bionic robotic fish is designed. Then the convergence of the iterative learning controller is proved. Finally, the trajectory tracking control simulation experiment based on iterative learning is conducted. The simulation results show that the trajectory tracking control method based on iterative learning for a bionic robotic fish is effective.

Modeling and Simulation Research on Soft Pectoral Fin of a Bionic Robot Fish Inspired by Manta Ray

Modeling and Simulation Research on Soft Pectoral Fin of a Bionic Robot Fish Inspired by Manta Ray

Energy Saving Control of Bionic Robotic Fish based on Model-free Adaptive Control

Abstract In this paper, an energy-saving model-free adaptive control (MFAC) is proposed for the control of the bionic robotic fish. First, the original MFAC controllers for the speed based on the full form dynamic linearization data model are presented as an example of the controlled variable of the controlled object. Then by modifying the criterion function for control input optimization, an energy-saving MFAC controller is designed to reduce the energy consumption. The proposed method is a data-driven control method, which means that the control system designing process merely needs input and output (I/O) measurement data of the controlled plant, and does not need any model information. Simulation results demonstrate the effectiveness of the improved MFAC in speed and attitude control of the bionic robotic fish.

Modeling and Analysis of Soft Pneumatic Actuator with Symmetrical Chambers Used for Bionic Robotic Fish.

A theoretical model is built in this study for analyzing and predicting the deformation of a bending-type soft pneumatic actuator used for bionic robotic fish. The actuator is composed of two symmetrically distributed silicone rubber blocks (Ecoflex0030 from Smooth-on Co., Ltd.). Between the two rubber blocks, an ABS plate is fixed to work as a neutral layer. When one side of the actuator is inflated, it consequently bends toward the uninflated side. The deformation of the actuator on the inflated side and the uninflated side, respectively, is analyzed based on principles of elasticity mechanics. The deformation on the inflated side is simplified to planar type and is decomposed into two mutually perpendicular directions to analyze the stress state. A two-step deforming process is proposed to study the stress state on the uninflated side. The two components are combined to determine the relationship between the bending angle of the actuator and the actuating pressure. The proposed model is compared with a finite element analysis model in which the same constraint, load, and materials are used. An experiment under the same conditions was implemented to validate the model. The experiment demonstrates that the accuracy of the theoretical model is adequate to indicate the response of the soft pneumatic actuator to the actuating pressure. A bionic fishtail system based on the soft pneumatic actuator was also established to verify the applicability of the actuator to bionic robotic fish.

Simulation Analysis of Bionic Robot Fish Based on MFC Materials

With the development of marine resources, research on underwater robots has received unprecedented attention. The discovery and application of new smart materials provide new ideas for the research of underwater robots, which can overcome the issues of traditional underwater robots and optimize their design. A macro fiber composite (MFC) is a new type of piezoelectric fiber composite that combines actuators and sensors. The material has excellent deflection, good flexibility, and a high electromechanical coupling coefficient. Bionic mechatronics design is an effective way to innovate mechatronics in the future and can significantly improve mechatronics system performance. As an important issue for the design of bionic mechatronics, it is necessary to make robots as soft as natural organisms to achieve similar biological movement with both higher efficiency and performance. Compared with traditional rigid robots, the design and control of a soft robotic fish are difficult because the coupling between the flexible structure and the surrounding environment should be considered, which is difficult to solve due to the large deformation and coupling dynamics. In this paper, an MFC smart material is applied as an actuator in the design of bionic robotic fish. Combined with the piezoelectric constitutive and elastic constitutive equations of the MFC material, the voltage-drive signal is converted to a mechanical load applied to the MFC actuator, which makes the MFC material deform and drives the movement of the robotic fish. The characteristics of caudal fin motion during the swimming process of the bionic robotic fish were analyzed by an acoustic-solid coupling analysis method. The motion control analysis of the bionic robotic fish was carried out by changing the applied driving signal. Through numerical analysis, a new type of soft robotic fish was designed, and the feasibility of using an MFC smart material for underwater bionic robotic fish actuators was verified. The new soft robotic fish was successfully developed to achieve high performance.

Enhanced Fireworks Algorithm-Auto Disturbance Rejection Control Algorithm for Robot Fish Path Tracking

The robot fish is affected by many unknown internal and external interference factors when it performs path tracking in unknown waters. It was proposed that a path tracking method based on the EFWA-ADRC (enhanced fireworks algorithmauto disturbance rejection control) to obtain high-quality tracking effect. ADRC has strong adaptability and robustness. It is an effective method to solve the control problems of nonlinearity, uncertainty, strong interference, strong coupling and large time lag. For the optimization of parameters in ADRC, the enhanced fireworks algorithm (EFWA) is used for online adjustment. It is to improve the anti-interference of the robot fish in the path tracking process. The multi-joint bionic robot fish was taken as the research object in the paper. It was established a path tracking error model in the Serret-Frenet coordinate system combining the mathematical model of robotic fish. It was focused on the forward speed and steering speed control rate. It was constructed that the EFWA-ADRC based path tracking system. Finally, the simulation and experimental results show that the control method based on EFWAADRC and conventional ADRC makes the robotic fish track the given path at 2:8s and 3:3s respectively, and the tracking error is kept within plus or minus 0:09m and 0:1m respectively. The new control method tracking steady-state error was reduces by 10% compared with the conventional ADRC. It was proved that the proposed EFWA-ADRC controller has better control effect on the controlled system, which is subject to strong interference.

Control and Optimization of a Bionic Robotic Fish Through a Combination of CPG model and PSO

Swimming speed and propulsive efficiency are critical indicators of a self-propelled bionic robotic fish in terms of swimming performance. This paper is devoted to achieving a maximum swimming speed and a higher propulsive efficiency for a four-joint robotic fish. A Newton–Euler method based dynamic model in conjunction with a central pattern generator (CPG) network serves to theoretically estimate fish-like swimming performance. In particular, each CPG unit based on limit cycles serves to drive one joint of the robotic fish. The overall CPG model is able to generate rhythmic signals for multimode swimming. To obtain the maximum average speed, a particle swarm optimization (PSO) algorithm is further utilized to optimize the feature parameters of the CPG model. Furthermore, the higher propulsive efficiency is sought within the same control framework. Simulations and experiments on the actual robotic fish demonstrate the improved propulsive performance and the effectiveness of the proposed control framework.

Mechanism Design of a Bionic Robotic Fish

In recent years, bionic robot fish have received more and more attention and have been applied in many fields, such as underwater detection, underwater archaeology, and military field. The main reason is that the propulsion and propulsion efficiency of the bionic fish are high, and the swimming performance is excellent, which is suitable for underwater operation. This paper studies the mechanism design of bionic fish which is suitable for underwater operation. The presented robotic fish consists of the power transmission mechanism of tail and the rising-falling mechanism of chest. The swing mechanism of tail uses DC motors as driver, and the transformation mechanism is added at the tail to turn the rotary motion of motor into swing movement. The pectoral fins wobble mechanism is used as the rising and falling mechanism, which is conducive to raising the swing frequency.