Motion Analysis And Control Of A12-Tetrahedral Robot

This paper focuses on a12-Tetrahedral robot which is to extend current space exploration intoregions currently inaccessible by universal mobile robots, the robot with higher mobility, invisibilityand superior obstacle ability to adapt to the irregular and unknown environments. The robot is consistsof eight external nodes and one internal node connected by26extension struts. The robot’s shape willshift by changing the strut length coordinately to change its center of mass, and the robot will move todesired direction. Although the12-Tetrahedral robot has a number of advantages, its variablegeometry truss mechanism with multi-strut, multi-closed chain and multi-node leads to difficulties ofits motion control. Based on this background, this paper studies the robot kinematics, dynamic, gaitplanning, control and its realization.The kinematics position of the12-Tetrahedral robot was analyzed by a geometric method, andthe direct kinematics and inverse kinematics of the robot was formulated. For each tetrahedron, theforth node’s position could be solved according to the position of the other three nodes in the basecoordinate system, and then selecting new tetrahedrons in order, the position direct solution of therobot was finally obtained. The effectiveness of the method has been testified through two examples.The Jacobian matrix of the robot was deduced in detail, and it is the foundation of the dynamicmodel. The robot dynamic model was derived by Lagrange method, the dynamic model of the robotnode contacting with the ground was taken into account. Finally, the Cartesian space robot dynamicwas deduced.A robotic gait was proposed and detailed planning aimed at12-Tetrahedral robot characteristics.The trajectories displacement of each strut was planned by inverse kinematics. The robot systemmodel was established in ADAMS, importing the trajectories and simulation. The results show thetrajectory planning is feasible and effective.The independent strut controller was designed using decentralized control strategy for the mutualcoupling among each strut. The control system model was established in Matlab, and the robot systemwas created in ADAMS, the simulation results show the independent strut controller is effective, andthe struts can accurately track the desired trajectories.The robot control system hardware and software were developed for the robot prototype,including the motor and drive module and wireless communication module. These modules werepreliminary tested.