Study On Biomimetic Jellyfish Robot Actuated By Shape Memory Alloy

The 21st century is the century of ocean. Underwater robots play an important role in the seabed resource exploration, marine environmental monitoring, underwater pipeline laying and defense fields. It has becomes an important tool for people to develop and use ocean. In this paper, the jellyfish is chosen as the bionic object. Through comparing the performance characteristics of several smart materials, a kind of biomimetic jellyfish-like underwater robot actuated by shape memory alloy (SMA) spring has been developed. The virtual prototype and each component of the biomimetic jellyfish robot are simulated and analyzed to lay the foundation for the model of underwater experiments and subsequent optimization.At first, an investigation was performed on the state of the underwater robots actuated by smart materials in the world, proposed study content. Through the performance test of SMA spring, the spring wire diameter and inner diameter are researched as the two internal factors influencing the size of the output force, and the driving voltage affects the response time of the spring deformation.Considering the one-way memory of SMA material, two differential straight push rod actuators are designed based on different specifications of the SMA spring, which can realize the reciprocating motion. By changing the driving voltage and the applied load size, it can get the factors that influence the driving performance.Three-dimensional graph of biomimetic jellyfish is drawn based on analysis of jellyfish morphological character and swimming mechanism. And then the prototype is manufactured by a laser engraving machine. The design of crank-slider mechanism transforms the linear motion into the swing of skeleton of the jellyfish. In addition, water is used to cool the SMA actuator in order to enhance the driving efficiency of the swimming.The software of ADAMS is used to analyze the dynamic performance of the jellyfish virtual prototype, including speed, acceleration, etc. and the swing angle of the skeleton rocker is calculated. On this basis, the maximum swing angle and dead center position are analyzed and MATLAB software is used to optimize each component of crank-slider mechanism in order to achieve the maximum swing angle in the condition of the given stroke of the push rod, which can improve swimming efficiency.Then, CFD method is used to analyze the hydrodynamic performance of the jellyfish with the different swing angles and different velocities, which obtains the resistance force and analyzes the causes of different pressures and velocities on the surface of the jellyfish.Finally, the driving circuit is designed using the single chip, which uses the PWM control to adjust the on-off time of the two sections of the SMA spring in order to achieve sustained swimming.In summary, the biomimetic jellyfish robot and its key technology are researched in this paper. The prototype and present research provide a useful reference for the further research of jellyfish robot.