This paper presents a generic error model, which is based on the product of exponentials (POEs) formula, for serial-robot calibration. The identifiability of parameters in this error model was analyzed. The analysis shows the following: 1) Errors in all joint twists are identifiable. 2) The joint zero-position errors and the initial transformation errors cannot be identified when they are involved in the same error model. With either or neither of them, three practicable error models were obtained. The joint zero-position errors are identifiable when the following condition is satisfied: Coordinates of joint twists are linearly independent. 3) The maximum number of identifiable parameters is 6n + 6 for an n-degree-of-freedom (DOF) generic serial robot. Simulation results show the following: 1) The maximum number of identifiable parameters is 6r + 3t + 6, where r is the number of revolute joints, and t is the number of prismatic joints. 2) All the kinematic parameters of the selective compliant assembly robot arm (SCARA) robot and programmable universal machine for assembly (PUMA) 560 robots were identified by using the three error models, respectively. The error model based on the POE formula can be a complete, minimal, and continuous kinematic model for serial-robot calibration.

Kinematic-Parameter Identification for Serial-Robot Calibration Based on POE Formula

A calibration method for enhancing robot accuracy through integration of an extended Kalman filter algorithm and an artificial neural network

One of the problems that slows the development of off-line programming is the low static and dynamic positioning accuracy of robots. Robot calibration improves the positioning accuracy and can also be used as a diagnostic tool in robot production and maintenance. This work presents techniques for modeling and performing robot calibration processes with off-line programming using a 3D vision-based measurement system. The measurement system is portable, accurate and low cost, consisting of a single CCD camera mounted on the robot tool flange to measure the robot end-effector pose relative to a world coordinate system. Radial lens distortion is included in the photogrammetric model. Scale factors and image centers are obtained with innovative techniques, making use of a multiview approach. Results show that the achieved average accuracy using a common off-the-shelf CCD camera varies from 0.2 to 0.4 mm, at distances from 600 to 1000 mm from the target, respectively, with different camera orientations. Experimentation is performed on two industrial robots to test their position accuracy improvement using the calibration system proposed: an ABB IRB-2400 and a PUMA-500. The robots were calibrated at different regions and volumes within their workspace achieving accuracy from three to six times better when comparing errors before and after calibration, if measured locally. The proposed off-line robot calibration system is fast, accurate and easy to set up.

Robot calibration using a 3D vision-based measurement system with a single camera

The paper deals with geometric calibration of industrial robots and focuses on reduction of the measurement noise impact by means of proper selection of the manipulator configurations in calibration experiments. Particular attention is paid to the enhancement of measurement and optimization techniques employed in geometric parameter identification. The developed method implements a complete and irreducible geometric model for serial manipulator, which takes into account different sources of errors (link lengths, joint offsets, etc). In contrast to other works, a new industry-oriented performance measure is proposed for optimal measurement configuration selection that improves the existing techniques via using the direct measurement data only. This new approach is aimed at finding the calibration configurations that ensure the best robot positioning accuracy after geometric error compensation. Experimental study of heavy industrial robot KUKA KR-270 illustrates the benefits of the developed pose strategy technique and the corresponding accuracy improvement. Geometric calibration of industrial robotsReduction of the measurement noise impact by means of proper selection of the manipulator configurations in calibration experimentsA new industry-oriented performance measure for optimal measurement configuration selectionExperimental study of heavy industrial robot KUKA KR-270

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Geometric calibration of industrial robots using enhanced partial pose measurements and design of experiments

Robot kinematics calibration is of great significance for improving robot absolute pose accuracy, which can be divided into modelbased and non-parametric kinematics calibration. For model-based kinematics calibration, kinematics calibration modeling, pose measurement of end-effector, kinematics parameters calibration and error compensation are systematically analyzed. And with the increasing demand for autonomy, the autonomous kinematics calibration is introduced. On the other hand, research status of nonparametric kinematics calibration is elaborated, the advantages and disadvantage of which are discussed respectively. On the basis, comprehensive and organized description and summarization of the three kinds of calibrations are given. Overall, aiming at robot kinematics calibration, existing achievements are summarized, a typical calibration process is carried out and calibration precautions are detailed, then calibration results of various methods are compared and analyzed. Finally, existing problems in kinematics calibration are analyzed and development prospects are presented.

Review on Kinematics Calibration Technology of Serial Robots

New general kinematic models for robot calibration are presented in this paper These models have the distinct advantage of satisfying the model-parameter identification requirements of completeness, minimality and model continuity for all combinations and configurations of revolute and prismatic joints A set of 17 model parametrizations are developed, including simple criteria for deciding which parametrizations are to be used in modelling a robot The parametrizations presented also result in an accurate representation of the physical robot and thus allow realistic integration of elastic deformation models Model continuity within each parametrization's application range is shown by means of differential geometry Also shown is how these models are be extracted from a non-complex “vector-chain” description of a robot

Complete, minimal and model-continuous kinematic models for robot calibration

A technique includes in a machine, processing data indicative of a document to be printed by a printer and which may contain magnetic ink character recognition (MICR) characters to determine whether the data indicates any MICR characters. The technique includes comparing a result of the determination to an intent indicated by a job ticket associated with the document; and controlling the printing of the document by the printer, including selectively performing corrective action in response to the comparison.

Controlling printing of a document that may contain MICR characters

A method for applying a bonding agent for supplemental ink includes, with a control system of a printing apparatus, determining regions of an image corresponding to regions where a supplemental ink is to be printed, and with the control system, adding an amount of pixels of a standard color channel to portions of a bitmap representing the image, the portions corresponding to the regions where the supplemental ink is to be printed. The amount of pixels is sufficient to trigger application of a bonding agent at the regions.

Stephen L Albright

Papers

Complete, minimal and model-continuous kinematic models for robot calibration

Controlling printing of a document that may contain MICR characters

Applying bonding agent for supplemental ink