“…Micro-milling vibration monitoring is a hot technology for enterprises to improve their equipment competitiveness and a frontier and difficult point in modern science and technology academic research [ 17 , 18 , 19 ]. Laser displacement sensors [ 9 , 13 , 14 , 20 ], microphones [ 21 ], capacitance sensors [ 22 ], acceleration sensors [ 23 ], and three-dimensional force sensors [ 24 , 25 , 26 , 27 ] are often used by researchers to obtain machining state signals or use multi-sensor information fusion based on the combining of some of these sensors to predict the tool vibration state [ 9 , 20 , 22 ]. However, there are some problems when the laser displacement sensor is used for the measurements of micro-milling vibration, such as when the spot is larger than the surface area of the tooltip and the sensor needs to be installed far away from the tool system [ 28 ].…”