MODEL ERROR COMPENSATION FOR BEARING TEMPERATURE AND PRELOAD ESTIMATION

A simple to apply, two-step observer design methodology is developed f or a general class of systems with model uncertainty. This appr oach i s applied to estimate bearing internal temperatures and the bearing pr eload of a machine tool spindle. The first step is the design of a mod el error compensator (MEC) to account for the model error associated w ith the bearingfriction heat generation. The second step includes a co nventional observer based oiz the nominal model that results from the implementation of the MEC. The sufficient condition for constructing a n effective MEC loop for the target spindle system is derived. The eff ectiveness ofthe MEC loop is demonstrated experimentally by comparing several different conventionalobserver designs, with and without the M EC. A comparison of the measurements to the estimation results indicat e in all cases tested the MEC improves the performance of the conventi onal observers. In addition, the results clearly show the distinctly d ifferent hearing outer ring/housing, rolling elements, and inner ring temperature behaviors. From the temperature estimation results, it is shown that previously published data on initial transient error associ ated with preload estimation is mainly due to the estimation error in the rolling element temperature. The proposed two-step observer method ology appears to be well suited for bearing temperature and preload mo nitoring problems.