New Robotic Architecture for NDT Applications

Abstract

Abstract The paper deals with the new architecture of the 4 degrees of freedom manipulator for Non-Destructive Testing (NDT) of the pipe welds of complex geometries. The main contribution is to overcome the known disadvantages resulting from using standard robotic architectures (universal industrial or single purposes special manipulators) regarding e.g. space requirements or limited applicability. The direct and inverse kinematic is solved. The singularity configuration analysis of the manipulator is derived in the sense of finding implicit description of the varieties in the task space. It makes possible to easily deal with singular configurations during the end-effector trajectory planning. In order to use the proposed manipulator for NDT of pipe welds the trajectory generators are introduced. The circumferential, elbow, longitudinal and branch weld are taken into account. It is shown that the trajectory parametrization of the first three types of welds can be found easily. But for the branch weld there are some drawbacks regarding unnatural parametrization of the branch weld primitives (ellipses, Steinmetz solid). Therefore the new numerical algorithm is developed and used to ensure the requirements of the correct arc lengths are met. The algorithm is compared with its simplified version where equidistant spacing of the parametrization parameter is considered.