Design And Motion Analysis Of A Bionic Amphibious Crocodile Robot

With the development of human society,people’s activities are gradually extending from land to swamps,mudflats,lakes and oceans.Alone,land-based mobile robots or underwater mobile robots are no longer able to adapt to complex environments and unstructured terrain.Amphibious robots have therefore attracted a great deal of interest from researchers.Amphibious robots can provide working platforms for environmental inspection,resource exploration,and marine data collection.The crocodile as a spinal reptile can not only adapt to complex environments on land but can also swim fast in water.In this thesis,the crocodile is used as a bionic object for the research and experimental analysis of a bionic amphibious crocodile robot.The topological structure of the biomimetic crocodile was designed by studying the function and cooperation of different parts of the body during different movements and the skeletal limb structure of the crocodile.The model of the biomimetic crocodile was designed by three-dimensional drawing software.Biomimetic crocodiles are designed to adapt to both terrestrial and aquatic environments,and parts of their body exhibit a variety of capabilities depending on the situation.The improved D-H method is used to establish the D-H coordinate system to perform kinematic analysis on the limbs,spine and tail of a biomimetic crocodile,which simplifies the complexity of kinematic modeling and solving of a multi-joint robot,and obtains the control angle information.The kinematics model is built using MATLAB and the correctness of kinematics analysis is verified by simulation,and the reachable space of each part is solved.The Lagrange equation was used to analyze the leg dynamics of a biomimetic crocodile.Then to allow the body parts of the bionic crocodile to exhibit a wide range of capabilities depending on the situation.In this thesis,the trajectory of the foot end of the bionic crocodile is planned using the composite pendulum method and the control angle is derived by inverse solution to achieve closed-loop control of the limbs.The correlation between the phase of the crocodile’s limbs and the spine and tail angles during movement is extracted from the images of the crocodile’s movement in one cycle to achieve coordinated planning and control of the bionic crocodile as a whole.Experiments are conducted to verify the locomotor capabilities of the bionic crocodile such as stability of movement,robustness to the failure of its own components and adaptability to the environment.According to the state of the bionic crocodile’s foot touching the ground when jumping,the bionic crocodile’s running and jumping is divided into four stages and controlled in different ways to achieve the simulation of the bionic crocodile’s running and jumping gait.Analyze the swimming mechanism of the crocodile,establish a twodimensional model of the bionic crocodile,simulate the autonomous swimming state of the bionic crocodile under different swing periods through numerical simulation,and verify the swimming performance of the bionic crocodile.The thesis concludes with a summary of the main work and an outlook on future research directions.