Modeling, optimizing and simulating robot calibration with accuracy improvement

This work describes techniques for modeling, optimizing and simulating calibration processes ofrobots using off-line programming. The identification of geometric parameters of the nominalkinematic model is optimized using techniques of numerical optimization of the mathematicalmodel. The simulation of the actual robot and the measurement system is achieved by introducingrandom errors representing their physical behavior and its statistical repeatability. An evaluationof the corrected nominal kinematic model brings about a clear perception of the influence ofdistinct variables involved in the process for a suitable planning, and indicates a considerableaccuracy improvement when the optimized model is compared to the non-optimized one

AN OFF-LINE ROBOT PROGRAMMING SYSTEM INCLUDING WORKCELL AND ROBOT CALIBRATION

Abstract. Off-line programming provides an essential link for CAD/CAM. The implementation of off-line programming encounters problems in: a) generalized programming systems that are independent of both robots and robot applications, b) incompatibility between robots and programming systems, c) accounting for errors and inaccuracies that exist in the real world. Errors can be reduced substantially by using proper robot calibration. Robot Calibration is a term applied to the procedures used in determining actual values that describe the geometric dimensions and mechanical characteristics of a robot or multi-body structure. A robot calibration system must consist of appropriate robot modeling techniques, accurate measurement equipment, and reliable model parameter determination methods. For practical improvement of a robot’s absolute accuracy, error compensation methods are required that use calibration results. The objective of this article is to discuss a method to construct kinematic models for robot calibration assuring model continuity and to present a computer program to carry out this task automatically before the identification step as part of an off-line programming system. It is also discussed the inclusion of robot calibration results in the off-programming system aiming at improving the robot global accuracy through re-calculation of spatial world coordinates

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved