| Under the background of increasing exploration and development of ocean in order to human survive and develop,a novel aurelia bionic jellyfish robot actuated by the shape memory alloy(SMA)flexible actuator module was designed for the unstructured marine environment with unknown challenges.The robot adopts the jet propulsion,which has the characteristics of simple structure,easy maintenance,low noise and high propulsive efficiency,and avoids the problem that traditional underwater robots,which adopt propeller propulsion,are propeller driven by cables,kelp and abandoned fishing nets,and an artificial system that transforms the results of natural evolution into imitation of its structure,function and performance is realized.This paper focuses on the design of bionic jellyfish robot system as the following aspects:(1)Through research and analysis of the current state of the art in underwater robots and bionic jellyfish robots,the research background and significance of the project are expounded,and the existing works related to this topic are summarized,Besides,the development trends of underwater robots and bionic jellyfish robots are analyzed.(2)In order to realize the contraction-release motion of the bell of the jellyfish robot,a novel actuator module inspired by artificial muscle is designed based on shape memory alloy(SMA)wires.The length,width,and thickness of the module are 100mm,10mm,2.5mm,and the effective length is 87mm,respectively.The average resistance of the SMA wire in the actuator module is 6 ohms with an error less than 0.5 ohms.The maximum response frequency of the actuator is 2.48 Hz(driving voltage 20V),and its maximum bending angle is greater than 170 degrees(with a heating voltage of 24 V).In order to reduce the influence of SMA nonlinearity,the thermal dynamic Liang's cosine model of the SMA actuator module is built,and the model simulation is realized in MATLAB,and the bending response of the SMA actuator module is analyzed by compared with the result of the experiment.(3)Through the bio-mimetic analysis of the aurelia's structure,the prototype of the jellyfish robot is designed and manufactured.The diameter of the robot is 210 mm with a height of 80 mm.According to the motion control requirements of the jellyfish robot,the corresponding control circuit and communication module are built.The hydrodynamic modeling of the thrust of the robot is carried out,and the validity of the model is verified by comparing the experimental and simulation results.(4)Using Ijspeert's CPG model,a CPG network with six oscillators for control of the bio-mimetic jellyfish robot is proposed.In order to solve the influence of heat accumulation to the SMA actuator module and realize multiple motion modes of the jellyfish robot,a control strategy is proposed by mutual modulation of the CPG network output signal and an adaptive heating strategy(AR)feedback signal.(5)A series of underwater experiments of the bionic jellyfish robot were carried out.The linear patrolling and turning at different frequencies of the jellyfish robot were detail investigated,and the feasibility of the design and control strategy of the jellyfish robot is verified.The experiment results illustrated that the robot had a maximum swimming speed of 52.80 mm/s that is nearly 0.66 times the body length,and with a minimum turning radius of 31.95 cm.Finally,by observing the flow field,the movement mechanism of the jellyfish robot is analyzed and discussed. |
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