The present invention provides a cross-axis and cross-point modal testing and parameter identification method for predicting the cutting stability, which is used to improve the accuracy of existing prediction methods of cutting stability. The method firstly installs a miniature tri-axial acceleration sensor at the tool tip, and conducts the cross-axis and cross-point experimental modal tests respectively. The measured transfer functions are grouped according to different measuring axes, and the dynamic parameters are separately identified from each group of transfer functions. Then, the contact region between the cutter and workpiece is divided into several cutting layer differentiators. After that, together with other dynamic parameters, all the parameters are assembled into system dynamic parameter matrices matching with the dynamic model. Finally, dynamic parameter matrices including the effects of cross-axis and cross-point model couplings are obtained. Moreover, the acceleration sensor in the method only needs to be installed once.

The present invention provides a cross-axis and cross-point modal testing and parameter identification method for predicting the cutting stability, which is used to improve the accuracy of existing prediction methods of cutting stability. The method firstly installs a miniature tri-axial acceleration sensor at the tool tip, and conducts the cross-axis and cross-point experimental modal tests respectively. The measured transfer functions are grouped according to different measuring axes, and the dynamic parameters are separately identified from each group of transfer functions. Then, the contact region between the cutter and workpiece is divided into several cutting layer differentiators. After that, together with other dynamic parameters, all the parameters are assembled into system dynamic parameter matrices matching with the dynamic model. Finally, dynamic parameter matrices including the effects of cross-axis and cross-point model couplings are obtained. Moreover, the acceleration sensor in the method only needs to be installed once.

A numerical control device is for machining a machining object by moving a tool and the machining object relative to each other along a movement path while applying vibration, by use of a drive axis provided for the tool or the machining object. The device includes a storage unit that holds an invalid frequency region, and a vibration condition determining unit to determine a frequency for the vibration, based on a rotational speed of a main shaft for rotating the machining object, a number of vibrations of the vibration in each one rotation of the main shaft, and the invalid frequency region.

A vibration sensor includes a mass block supported with the aid of at least one spring in a manner allowing movement relative to a frame in a measuring direction, a displacement of the mass block in the measuring direction relative to the frame being detectable by a position-measuring device. The position-measuring device includes a measuring standard and a scanning head aligned with the measuring standard. One of these two components is secured on the mass block, and the other is secured on the frame.

A vibration sensor includes a mass block supported with the aid of at least one spring in a manner allowing movement relative to a frame in a measuring direction, a displacement of the mass block in the measuring direction relative to the frame being detectable by a position-measuring device. The position-measuring device includes a measuring standard and a scanning head aligned with the measuring standard. One of these two components is secured on the mass block, and the other is secured on the frame.

Provided a vibration measurement device for a rotary tool held by a tool holder that is coupled with a spindle and axially rotates in cooperation with the spindle. The vibration measurement device includes: a pair of acceleration sensors attached to a horizontal plane with respect to a rotary axis of a rotary tool in a manner symmetric to the rotary axis; an amplifier circuit that matches impedance of acceleration information from the acceleration sensors and amplifies voltage; a low-pass filter that removes predetermined high frequencies from an output signal of the amplifier circuit; and a subtraction circuit and an addition circuit that output a parallel vibration signal in an XY direction and a vibration signal in a rotational direction, respectively, from the output signal of the low pass filter.

Provided a vibration measurement device for a rotary tool held by a tool holder that is coupled with a spindle and axially rotates in cooperation with the spindle. The vibration measurement device includes: a pair of acceleration sensors attached to a horizontal plane with respect to a rotary axis of a rotary tool in a manner symmetric to the rotary axis; an amplifier circuit that matches impedance of acceleration information from the acceleration sensors and amplifies voltage; a low-pass filter that removes predetermined high frequencies from an output signal of the amplifier circuit; and a subtraction circuit and an addition circuit that output a parallel vibration signal in an XY direction and a vibration signal in a rotational direction, respectively, from the output signal of the low pass filter.

A monitoring method and a monitoring system for a machine tool to machine a workpiece are provided. The monitoring method includes the following steps. First, a vibration signal of a spindle of the machine tool is detected. Next, a vibration feature value of the vibration signal is obtained. Whether the vibration feature value exceeds a threshold condition is determined, wherein the threshold condition is determined by a training model based on a predetermined surface quality of the workpiece. When the vibration feature value exceeds the threshold condition, a machining parameter of the machine tool is adjusted.

A monitoring method and a monitoring system for a machine tool to machine a workpiece are provided. The monitoring method includes the following steps. First, a vibration signal of a spindle of the machine tool is detected. Next, a vibration feature value of the vibration signal is obtained. Whether the vibration feature value exceeds a threshold condition is determined, wherein the threshold condition is determined by a training model based on a predetermined surface quality of the workpiece. When the vibration feature value exceeds the threshold condition, a machining parameter of the machine tool is adjusted.

A method for inspecting normality of a spindle of a machine tool is provided. Spectral analysis, time domain analysis and principal components analysis are performed on a vibration signal that results from the vibration of the spindle, so as to build a Gaussian mixture model. Then, based on a difference between the Gaussian mixture model and a predetermined reference model, whether the machine tool is operating normally can be determined in real time.