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A new algorithm for the use of an anthropomorphic robot manipulator arm in remote and laboratory NDT application
Author(s)
Date Issued
1995
Publisher
Informa UK Limited
ISSN
1058-9759
1477-2671
Citation
Nondestructive Testing and Evaluation, 1995, vol. 12(3), pp. 181-196.
Type
Peer Reviewed Journal Article
Abstract
Published studies of serial link arm usage for the manipulation of sensors in NDT are rare, perhaps because there is a perception that the cumulative errors in spatial location along such arms are too great for satisfactory imaging. These errors, with good programming. are not as serious as they might seem at first sight and the flexibility of serial arms is most attractive. This paper shows that a serial link robot manipulator ann can be used to perform raster scans (as used in ultrasonic c-scanning) with precision in spatial resolution as good as is required in the NDT industry and normally achieved by means of conventional x-y cartesian scanners. It also presents an iterative method to compute the inverse kinematics (ie the programme of sequence of joint angles) needed to constrain a serial link robot manipulator to perform an NDT scanning operation (eg to perform a plan or raster scan whilst maintaining a constant angle between the probe and the surface under inspection). The iterative method presented for solving inverse kinematics requires very little computation and gives more accurate results as compared to conventional methods which require cumbersome calculations on more complex expressions. This robot arm can then be used to obtain c-scans in the laboratory, by scanning over a fixed object. in or outside an immersion tank. Alternatively it can be mounted on a mobile robot for remote field applications. In principle, weight considerations apart, the scanning algorithm described is independent of the type of sensor (ultrasonic, eddy current etc). The human-like manipulator ann offers advantages of access to nooks and comers over the x-y cartesian manipulators usually used in the Non-destructive Testing (NDT) industty. In addition the greater degrees of freedom provided by a serial link manipulator ann can make possible the NDT scanning of contoured surfaces such as pipes and spheres.
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