Adam Wozniak

Factors influencing probing accuracy of a coordinate measuring machine

The analysis of probe operational parameters such as configuration of the probe, including triggering (measuring) force, stiffness, and length of the stylus, has been performed. A new method allowing three-dimensional (3-D) probe error characteristics with several times more accuracy than the procedure used on a coordinate measuring machine (CMM) has been applied. The analyses have been performed for devices of two types: a single-stage and a two-stage switching probe. The influence of the above-mentioned parameters has been analyzed theoretically and verified experimentally in two planes: perpendicular and parallel to the probe axis. Good agreement between the proposed theoretical model and experimental data has been obtained.

New Method for Testing the Dynamic Performance of CMM Scanning Probes

In this paper, a new method that applies a piezoelectric translator to test the dynamic accuracy of scanning probes for coordinate measuring machines (CMMs) is proposed. The principle of the method is presented, and this method is used for the evaluation of measurement uncertainty. The validity of the method is experimentally confirmed on a bridge Zeiss PRISMO CMM equipped with a VAST XT scanning probe.

Indirect force control development procedure

Addition of extra sensors, especially video cameras and force sensors, under control of appropriate software makes robotic manipulators working in factories suitable for a range of new applications. The article presents a method of manipulator indirect force control development, in which the force set values are specified in the operational space and the manipulator is equipped with a force sensor in its wrist. Standard control development methods need an estimation of parameters of the detailed model of a manipulator and position servos, what is a complicated and time consuming task. Hence in this work a time efficient hybrid procedure of controller development is proposed consisting of both an analytical and experimental stages: proposal of an approximate continuous model of a manipulator, experimental determination and verification of its parameter values using the resonance phenomenon, continuous regulator development, digitization of the regulator. keywords: manipulator control, indirect force control, controller development

A robust method for probe tip radius correction in coordinate metrology

A new algorithm for tip radius correction for the metrology of free-form and two-dimensional contours is proposed. The method is for use in a high-definition coordinate metrology context, as is now possible with scanning probes, where the density of points per scanned distance ensures that the successive probe ball positions overlap partially with each other. The proposed method for correcting measurements can be applied directly to the data collected during a coordinate measuring machine (CMM) measuring process. An additional advantage of the new algorithm is the possibility of detecting the incoherent corrected measured point, a form of validity check. The algorithm performance was verified experimentally on a Zeiss ACCURA CMM with an active VAST Gold scanning probe.

Application of fuzzy knowledge base for corrected measured point determination in coordinate metrology

This paper describes an application of fuzzy logic for corrected measured point determination in coordinate metrology. The correction method works on a series of indicated points obtained by contact scanning of the measured surface with a spherical tip probe. The outline of the probe ball defines an arc for each measured point, each such arc being delimited by the points of intersection with the preceeding and the following arcs. As a first approximation the corrected measured point is estimated as the mid-point of the arc. The refinement to the method consists in determining an angular compensation to be applied to the mid-point estimation and calculating the associated indicated measured point coordinate values. To determine an angular compensation a rule-based approach to decision making using fuzzy logic techniques is proposed. In this approach, we consider imprecise vague knowledge as a set of rules linking a finite number of conditions with a finite number of conclusions. The representation of such imprecise knowledge by means of fuzzy linguistic terms makes it possible to carry out quantitative processing in the course of inference based on the compositional rule of inference that is used for handling uncertain (imprecise) knowledge, often called approximate reasoning or fuzzy reasoning. Such knowledge can be collected and delivered by a human expert (e.g., decision maker, designer, process planner, machine operator, etc.). For our case, this knowledge is expressed by a finite number of heuristic fuzzy rules of the Multiple Input Single Output type (MISO). The paper will include a brief discussion of a new compensation procedure of probe radius tip and related test results of the same probe head carried out on a fixed bridge Mitutoyo Legex 910 CMM equipped with a MPP-300 scanning probe in the continuous scanning mode.

3D CMM strain-gauge triggering probe error characteristics modeling using fuzzy logic

The error values of CMMs depends on the probing direction; hence its spatial variation is a key part of the probe inaccuracy. This paper presents genetically-generated fuzzy knowledge bases (FKBs) to model the spatial error characteristics of a CMM module-changing probe. Two automatically generated FKBs based on two optimization paradigms are used for the reconstruction of the direction- dependent probe error w. The angles beta and gamma are used as input variables of the FKBs; they describe the spatial direction of probe triggering. The learning algorithm used to generate the FKBs is a real/ binary like coded genetic algorithm developed by the authors. The influence of the optimization criteria on the precision of the genetically-generated FKBs is presented.

Fuzzy Rule Base Influence on Genetic-Fuzzy Reconstruction of CMM 3D Triggering Probe Error characteristics

One of the most important sources of coordinate measuring machine (CMM) errors is the probe used to collect coordinate points on measured objects. The error value depends on the probing direction; hence its spatial variation is a key part of the probe inaccuracy. This paper presents genetically-generated fuzzy knowledge bases (FKBs) to model the spatial error characteristics of a CMM touch trigger probe. The automatically generated FKBs are used for the reconstruction of the direction-dependent probe error w. The angles beta and gamma are used as input variables of the FKBs; they describe the spatial direction of probe triggering. The learning algorithm used to generate the FKBs is a real/binary like coded genetic algorithm developed by the authors. The influence of the number of fuzzy rules (FR) on the precision of the genetically-generated FKBs is investigated by varying the number of fuzzy sets (FS) on the premises and on the conclusion. The results of the learning are examined. Once the adequate number of fuzzy rules is found, an optimal learning is performed and a near-optimal FKB of probe error characteristics is proposed

Micro-features measurement using meso-volume CMM

Paper will discuss an understanding for the compensation of the probe ball radius in a scanning process of micro-features. As will be shown, the indigenous CMM software does not always adequately compensate the stylus tip radius. As a result, the information about the real shape of the measured features can be distorted. In order to accurately measure precise geometric features, and in particular micro-features, a new algorithm for the compensation of the stylus tip radius in a CMM scanning process will be proposed. To demonstrate the performance of the indigenous CMM software as well as feasibilities of our new algorithm, we will show the results of measurements of the profiles of precise micro-feature such as silicon micro-grove. Tests will be carrying out on a fixed bridge, moving-table Mitutoyo LEGEX 910 CMM equipped with a MPP-300 scanning probe and also on a Zeiss ACCURA CMM equipped with a VAST GOLD scanning probe.