| For adapting to the water environment and missions under water, bionicpropulsion technology is paid close attention to in recent years. Analyses ondifferent underwater propulsion technologies are of great importance and practicalvalue for improvement of underwater propulsion and development of underwaterrobots.Frog is a famous amphibious creature which can jump and swim excellently bythe same propulsion mechanism of hind legs and the webbed feet, so it has amazinglocomotion ability in unstructured fields. Frog has flat body and subacute head,which aid in drag reduction and powerful propulsion during swimming. The lengthof hind legs accounts for a large proportion of the whole body length. Meanwhilehind legs are stronger than forelegs which can be neglected during propulsion. Thewebbed feet increase the propulsion areas for feet to swim fast. To use theadvantages of frog in the process of robot design, the bionic method is needed in theprocess of research on the swimming mechanism of frog and mechanical design ofbionic frog swimming robot.In order to obtain the kinematics of the frog body and trajectories of joints, anaquatic frog, Xenopus laevis, was chosen for analysis of swimming motions whichwere recorded by a high speed camera, and kinematic data were processed in aswimming data extraction platform. For the data processing, a pinhole cameramodel was built to transform the pixel coordinate system to world coordinatesystem, and the errors caused by the water refraction were analyzed and corrected.Finally, the kinematic data for the analysis of swimming mechanism and design ofbionic frog swimming robot could be obtained.Research on the swimming mechanism was carried out by the analysis of theobtained experimental data through preliminary observation experiment. And on thebasis of frog biological structure analysis, the prototype of robot was designed andpneumatic muscle was selected as drive element to reproduce the frog’s swimmingability so as to achieve the underwater rapid movement of bionic frog swimmingrobot. Finally, the joint trajectory obtained through preliminary observationexperiment was used to drive the joint of robot when the dynamics simulation wascarried out. Accordingly, the feasibility of the designed bionic frog swimming robotcould be verified.Through simplification of the developed bionic frog swimming robot, thekinematics model of robot system could be established. And the forward and inversekinematics of robot were analyzed through D-H method, accordingly the kinematic parameters of each rod could be obtained. On the basis of kinematics analysis, theLagrange method would be used to establish the dynamics equation of robot system.And the joint trajectory obtained through preliminary observation experiment couldbe transformed to the joint driving torque by the inverse dynamics analysis.Finally, the underwater swimming experiment of the bionic frog swimmingrobot was developed, not only to validate the reasonableness of bionic researchbased on the motion observation of frog, but also to validate the feasibility of bionicfrog swimming robot powered by pneumatic muscle. |
