Research On Bionic Coordinated Control And Propulsion Performance Of The Robotic Fish

The study of fish locomotion provides a rich source of inspiration for the design and development of robotic fish.The performance of fish can provide a series of complex motion design,involving a variety of structures used to generate movement forces and a versatile movement pattern that interacts with the aquatic environment.In the complex and uncertain underwater environment,the underwater robotic fish could accomplish the task of lake and sea exploration.Due to the advantages of high flexibility,high intelligence,strong adaptability and good security,intelligent robotic fish has gradually become an important tool for underwater tasks.Neurobiology studies have revealed that fish swimming involves rhythmic activities dominantly produced by central pattern generators(CPGs)at the spinal cord level.In essence,the central pattern generators can be viewed as a network of nonlinear oscillating neurons been able to produce robust,flexible rhythmic patterns without automatically synchronized control inputs from high levels.In this paper,two novel robotic fish with double tail fins are designed,which can eliminate the disadvantages of the robotic fish with single tail fin moving left and right.The main task of the first generation of robotic fish with CPG control network is to achieve a smooth transition of the maneuver,and the key for the second generation of robotic fish is to establish a reliable and efficient water dynamics modeling.The main research contents and results are as follows:(1)System design of robotic fish with double tail fins.Combining the pectoral fins with vectored thruster and double tail fins,we have designed the first generation of robotic fish DualFish-I,while front pectoral fins responsible for forward/backward maneuver and other maneuverabilities,and tail fins responsible for fast cruise.Different from the first generation of robotic fish,the second generation of robotic fish DualFish-II uses a single high power Maxon motor to control the precise flapping of the two tail fins.The highest frequency in the experiments can reach 6Hz,which meets the design requirements.(2)Establishment of CPG neural network.From the beginning of original equations of the neuronal oscillations,we have finished detailed derivation of the CPG network model of the construction control.Combining the motion characteristics of the first generation of robotic fish DualFish-I,we established the matching neural network control.Finally,the distance value from the feedback quantity of the infrared sensors will be transmitted to the feedback part of the CPG control network.(3)Hydrodynamic modeling.Based on the rigid segment theory and the quasi-steady assumption about no viscosity and compressibility,we have done the theoretical modeling fully of the rigid and flexible tail fin.In addition,we have calculated initial propulsion forces in several swing period.(4)Experimental study on maneuvering performance and propulsion performance of robotic fish with double tail fins.Based on the robotic fish with double tail fins DualFish-I and DualFish-II as the experimental object,a variety of maneuverability(forward and backward,up and down dive,roll turn and back and forth,etc.)tests and rapid performance tests have been done.With small power motors,the first generation of robotic fish has excellent characteristics of high speed.When using the double caudal fins,DualFish-I can reach a maximum speed of 0.54m/s,about1.21BL/s.When using the pectoral fins,DualFish-I can reach a maximum speed of 0.35m/s,about 0.8BL/s.Acceletation performance of the second generation of robotic fish is good,and the maximum acceleration can reach about 0.7m/s2.DualFish-? also has a very good cruise speed,which can reach a maximum speed of 0.7m/s,about 1.59BL/s.