Experimental thermal regulation of an ultra-high precision metrology system by combining Modal Identification Method and Model Predictive Control

Thermal drifts caused by the power dissipated by the mechanical guiding systems constitute the principal limit to enhance the measurement uncertainty of an ultra-high precision cylindricity machine. For this reason, an ultra-high precision compact prototype has been designed to simulate the behaviour of the instrument. It ensures in-situ calibration of four capacitive displacement probes by comparison with four laser interferometers. The test bench includes three heating wires for simulating the power dissipated by the mechanical guiding systems, four additional heating wires located between each laser interferometer head and its respective holder to control thermal drifts, 19 Platinum resistance thermometers (Pt100) to observe the temperature evolution inside the test bench and four Pt100 sensors to monitor the ambient temperature. A Reduced Model (RM) identified from measured data using the Modal Identification Method (MIM) was combined with a Model Predictive Controller (MPC). The control was applied to minimize the effects of thermal drifts on the principal organ of the cylindricity measurement machine. A parametric study of the MPC was initially conducted to evaluate the robustness of the controller. The association of both RM and MPC allowed significant reduction of thermal drifts generated by the three heating wires, which simulate powers dissipated by the mechanical guiding system. The obtained results can be considered as promising with regard to applications in dimensional metrology. (C) 2016 Elsevier Ltd. All rights reserved.