Suitability of integrated sensors for the determination of chatter characteristics in a cylindrical grinding machine

Wheel-sided chatter vibration is a limiting factor in terms of productivity and surface finish regarding the application of conventional grinding wheels. Due to the formation of waviness on the grinding wheel during the process, many expensive trueing cycles are necessary. Therefore, a system for chatter detection and elimination for external cylindrical grinding machines was presented in previous work. It was demonstrated that an electromagnetic actuator reduces the generation of the grinding wheel waviness. The control of this actuator requires precise knowledge about frequency, amplitude, and phase of the chatter vibration. This information is extracted from two eddy-current sensors, which measure the workpiece displacement. However, a direct measurement of the workpiece displacement restricts the working area and is inflexible. Hence, this paper explores the qualification of sensors integrated into the grinding machine for extracting the aforementioned information with high accuracy of phase. For this purpose, two acceleration sensors mounted on the workpiece spindle and the tailstock, an acoustic emission (AE) sensor applied to the grinding wheel, and the motor current of the directly driven headstock spindle are considered. To determine the suitability of these sensors, the frequency response function (FRF) for each sensor is calculated under three conditions: no contact between the workpiece and the grinding wheel, the grinding wheel tensed to the workpiece without a grinding process, and during the process. The method for the in-process measurement of the sensor FRFs and the influence of the contact conditions on these FRFs is shown in this paper.