Abstract: High speed magnetic bearing spindle is used as detection device to solve the difficulty of inline measuring of the normal grinding force. Magnetic bearing spindle rotor dynamics is analyzed to obtain the relationship of the normal grinding force with derivatives of rotor displacements and magnetic force of the magnetic bearing. The displacement data can be obtained from displacement sensor. In order to accurately solve the magnetic force, air gap flux density is obtained using the graphic method to eliminate the systematic errors introduced by the linearization; Air gap width is calibrated using multi-point method to eliminate the impact of the system assembly error on the measurement of electromagnetic force; A correction factor calculated by the three-layer neural network is introduced to deal with the measurement error caused by the magnetic flux leakage, hysteresis and edge effects; Finally, static and dynamic experiments are done to verify the measuring of magnetic force and dynamic grinding force. Experiment results show the validity and accuracy of the detection of the grinding force based on magnetic bearing spindles.

Key words: Air gap calibration, Graphical method, Magnetic bearing spindle, Magnetic force, Modification factor, Normal grinding force