Model discrepancy in robotic calibration: Its influence on the experimental parameter identification of a parallel space telescope

The model of a robot may not be able to consider all the physical phenomena influencing the manipulator performances since they are too numerous and/or difficult to measure: this is model discrepancy. For a highly-accurate active space telescope, an important source of inaccuracy was measured using photogrammetry: the deformation of its mobile platform. This deformation cannot be directly measured in space and needs to be properly modeled in order to enable the telescope calibration with the available measurements. Two incremental models are proposed and the parameter observability is discussed. After experimental calibration, a micrometer accuracy can be reached. The influence of model discrepancy on the experimental parameter identification is finally discussed.