Calibration of a coordinate-measuring device

A coordinate-measuring system including:

• a positioning platform, an articulated probe head connected to said positioning platform, and a coordinate probe removably connected to the articulated probe head, whereby the articulated probe head can assume a plurality of configurations corresponding to diverse orientations of the coordinate probe, the coordinate-measuring system being configured to:
• retrieve a first set of model parameters defining a model of the articulated probe head based on a first calibration wherein the probe head is caused to assume all the configurations in a first set of configurations,
• measure an artifact whose geometry is known while the probe head is caused to assume all the configurations in a second set of configurations,
• based on the measure of the artifact, determine additional model parameters defining, with the first set of model parameters, a model of an assembly of the articulated probe head on the coordinate-measuring system with the coordinate probe
• defining a range or a minimum value or a maximum value for one or more of said additional model parameters, and
• measure a workpiece by selecting a desired configuration of the articulated probe head, bringing the coordinate probe in contact with or in proximity to the workpiece and determining coordinates of points on the workpiece's surface from a measure of a position of the positioning platform using the model of the assembly.

A method of calibration for a coordinate-measuring system, wherein the coordinate-measuring system includes an articulated probe head connected to a positioning platform of the coordinate-measuring system and a coordinate probe removably connected to the articulated probe head, whereby the articulated probe head can assume a plurality of configurations corresponding to diverse orientations of the coordinate probe, the method including:

• a first calibration, in which a first set of model parameters defining a model of the articulated probe head is determined while the probe head is caused to assume the configurations in a first set of configurations,
• a second calibration comprising measuring an artifact whose geometry is known with the coordinate-measuring system and the coordinate probe mounted on the articulated probe head while the probe head is caused to assume all the configurations in a second set of configurations,
• based on the measurement of the artifact, determination of additional model parameters defining, with the first set of model parameters, a model of an assembly of the articulated probe head with the coordinate probe,
• defining a third set of configurations based on a model of a workpiece,
• a selective accurate calibration of the third set of configurations,
• correcting or overriding the model of the assembly when the configuration of the articulated probe head is in the third set of configurations, and
• measuring coordinates of points on a surface of the workpiece using the model of the assembly of the articulated probe head with the coordinate probe.