CMM error compensation and uncertainty evaluation using artefacts and local kinematic error models

摘要

The geometric errors associated with a CMM are usually described by the 21 parameter kinematic error model. Estimates of these kinematic errors can be determined by measuring a calibrated artefact such as a hole or ball plate in a number of positions in the CMM working volume and then matching the kinematic errors to the measured changes in artefact geometry. This paper describes a similar approach but using a local, simplified kinematic error model specific to the measurement task in hand. The kinematic model is local in the sense that it only applies to the particular region of the CMM working volume used for the measurement task and the contact probes being used and also in the sense that the model only applies during the limited time period it takes to perform the measurement task. The benefits of this approach are that medium term systematic effects associated with the CMM due to thermal effects, for instance, can be compensated for without the need to perform a full parametric error compensation exercise. The paper will also describe how uncertainties associated with the artefact being measured and the local kinematic errors can be evaluated.