NUMERICAL CONTROL DEVICE

Abstract

A numerical control device for controlling the operation of a machine tool including a spindle and a feed shaft, the machine tool machining a workpiece with a tool, the numerical control device comprising: an identification operation generation unit for generating an identification operation command for independently and continuously changing a rotational speed of the spindle and a feed rate; a data acquisition unit for synchronizing a control signal for controlling the machine tool with an operation state signal and outputting the synchronized signals as identification data, the control signal being generated based on the identification operation command, the operation state signal indicating an operation state of the machine tool operated based on the control signal;a vibration determination unit for determining, based on the identification data, whether a vibration state of the machine tool is stable machining, chatter vibration, or forced vibration; and an identification unit for selecting, based on a determination result of the vibration determination unit, an identifiable characteristic machining parameter as a selected parameter from characteristic machining parameters representing features of a machining phenomenon between the tool and the workpiece, and for performing identification of the selected parameter using the identification data.

Description

Area

[0001] The present invention relates to a numerical control device that controls a machine tool. General state of the art

[0002] Machine tools are machining devices that perform subtractive machining, i.e., machining in which unnecessary portions of a workpiece are removed by applying force or energy to the workpiece using a tool. Specifically, cutting is a type of subtractive machining in which unnecessary portions of a workpiece are shaved away by bringing the cutting edge of a tool into contact with the workpiece at high speed to cause shear fracture on the workpiece surface.

[0003] Since cutting is a physical phenomenon in which a machining process and mechanical dynamics influence each other, it is desirable to control the machining process and mechanical dynamics simultaneously to manage the machining state. The machining process represents a series of steps in which the tool cutting edge is moved into the workpiece to form a machined surface and also generates chips in the process. Mechanical dynamics represents the behavior of mechanical structures when structures of the machine are vibrated by a vibration source inside or outside the machine. In general, cutting is a phenomenon in which various physical phenomena, including the machining process and mechanical dynamics described above, influence each other in a complicated way, and thus an integrated analysis of cutting is considered difficult.For this reason, production sites evaluate a limited number of targets, thus achieving processing management that meets its purpose.

[0004] As described above, since mechanical dynamics and a machining process influence each other during cutting, the state of the machine tool before or after machining and the state of the machine tool during machining are different from each other. That is, before or after performing machining, it is not possible to accurately estimate the state of the machine tool during machining. Therefore, it is desirable to identify the mechanical dynamics and machining process using information obtained during machining. Using the result of identifying the mechanical dynamics and machining process enables operators on the production site to efficiently carry out improvement work, such as managing tool life, establishing high-efficiency machining conditions, and modifying the design of fixing devices.As a result, an improvement in productivity is to be expected.

[0005] Patent Literature 1 discusses a method for performing parameter identification using information obtained by sequentially changing machining conditions during actual machining. The method described in Patent Literature 1 involves calculating compliance spectra from displacement and force generated at a variety of spindle rotation speeds during machining, and calculating the tool's natural frequency from the peaks obtained by combining the compliance spectra of the different spindle rotation speeds.This method causes the machine tool to perform a machining operation to gradually change the spindle rotation speed during the independent operation of each feed shaft or the cooperative operation of feed shafts, and the compliance spectra are calculated using the result of detecting the displacement and force during machining. Citation listPatent literature

[0006] Patent literature 1: JP 2017 - 94 463 A Brief descriptionTechnical problem

[0007] In the method described in Patent Literature 1, a cutting amount is set to such an extent that chatter vibration does not occur, and the spindle rotation speed is gradually changed to obtain various compliance spectra, thereby calculating the natural frequency. Therefore, a problem with the method described in Patent Literature 1 is that this method can only identify the natural frequency and cannot identify characteristic machining parameters, such as a specific cutting force. Furthermore, the method described in Patent Literature 1 requires a different identification operation to identify parameters other than the natural frequency.In addition, since the spindle rotation speed is only changed in a plurality of predetermined steps in the method described in Patent Literature 1, it is time-consuming to acquire parameters corresponding to different spindle rotation speeds.

[0008] The present invention has been made in view of the above, and an object thereof is to obtain a numerical control device capable of efficiently identifying the characteristic machining parameters in a short time. Solution to the problem

[0009] The problem is solved by a numerical control device having the features of patent claim 1. Advantageous effects of the invention

[0010] The numerical control device according to the present invention can achieve the effect of efficiently identifying the characteristic machining parameters in a short time. Brief description of the drawings Fig. 1 is a block diagram illustrating an exemplary configuration of a numerical control device according to a first embodiment. Fig. 2 is a diagram illustrating an exemplary pattern of an identification operation command generated by an identification operation generation unit according to the first embodiment. Fig. 3 is a diagram illustrating an exemplary pattern of an identification operation command generated by the identification operation generation unit according to the first embodiment. Fig. 4 is a diagram illustrating an exemplary pattern of an identification operation command generated by the identification operation generation unit according to the first embodiment. Fig. 5 is a schematic diagram illustrating the transmission of disturbance forces to a table in the case where the workpiece fixed to the table is vibrated by the cutting force in the first embodiment. Fig. 6 is a diagram illustrating an exemplary rotation angle of a tool at which the tool cutting edge is in contact with the workpiece according to the first embodiment. Fig. 7 is a diagram illustrating an exemplary rotation angle of a tool in which the tool cutting edge is not in contact with the workpiece according to the first embodiment. Fig. 8 is a diagram illustrating cutting with a first cutting edge when there is a deviation amount between the center of the tool center and the center of the spindle in the first embodiment. Fig. 9 is a diagram illustrating cutting with a second cutting edge when there is a deviation amount between the center of the tool center and the fulcrum of the spindle in the first embodiment. Fig. 10 is a flowchart illustrating an exemplary identification procedure in an identification unit according to the first embodiment when a vibration determination unit provides a vibration determination result of a chatter vibration. Fig. 11 is a flowchart illustrating an example of the operation of the numerical control device according to the first embodiment. Fig. 12 is a diagram illustrating an exemplary configuration of a processing circuit according to the first embodiment. Fig. 13 is a block diagram illustrating an exemplary configuration of a numerical control device according to a second embodiment. Fig. 14 is a flowchart illustrating an example of the operation of the numerical control device according to the second embodiment. Fig. 15 is a block diagram illustrating an exemplary configuration of a numerical control device according to a third embodiment. Fig. 16 is a block diagram illustrating an exemplary configuration of a numerical control device according to a fourth embodiment. Description of the embodiments

[0011] Hereinafter, a numerical control device according to embodiments of the present invention will be described in detail based on the drawings. The present invention is not limited to the embodiments. First embodiment

[0012] Fig. 1 is a block diagram illustrating an exemplary configuration of a numerical control device 1 according to the first embodiment of the present invention. The numerical control device 1 according to the first embodiment controls the operation of a machine tool 2 by transmitting a control signal to the machine tool 2 and receiving an operating state signal indicating the operating state of the machine tool 2 from a sensor (not illustrated).

[0013] The machine tool 2 includes a spindle and a feed shaft, and machines a workpiece with a tool. Specifically, the machine tool 2 cuts the workpiece by operating at least one of the tool and the workpiece. For example, the machine tool 2 includes a spindle that imparts rotational motion to the tool or the workpiece, and a feed shaft, which is a servo shaft that imparts position to the tool or the workpiece. The spindle and the feed shaft each include a motor.

[0014] The machine tool 2 includes a sensor that detects the operating state of the machine tool 2 and outputs the detection result as an operating state signal. Among the sensors provided in the machine tool 2 is a sensor capable of detecting vibrations of at least one of the tool and the workpiece. The sensor capable of detecting vibrations of at least one of the tool and the workpiece is, for example, a linear encoder and a current sensor built into the machine tool 2 for feedback control of each motor of the machine tool 2. The linear encoder detects the position of each shaft of the machine tool 2, and the current sensor detects the motor current through the motor of each shaft. Other examples of sensors include an acceleration sensor, a position sensor, a force sensor, or a microphone.The sensors provided in the machine tool 2 are described below as examples of a linear encoder, a current sensor, and a force sensor. The force sensor is installed, for example, on or in a structure such as a table that provides the feed shaft. The installation position of the force sensor is not limited to this, and the force sensor can be installed at any position where force can be detected between the tool and the workpiece.

[0015] As in Fig. 1, the numerical control device 1 includes a correction unit 11, a vibration determination unit 12, an identification unit 13, an identification operation generation unit 14, a drive control unit 15, and a data acquisition unit 16. The operation of each unit of the numerical control device 1 according to the present first embodiment will be described.

[0016] The identification operation generation unit 14 generates an identification operation command for independently and continuously changing the spindle rotation speed and the feed rate of the machine tool 2 and outputs the identification operation command to the drive control unit 15. The spindle rotation speed, which is the rotation speed of the spindle, indicates the number of times the spindle rotates per unit time. The identification operation is the operation in which the drive control unit 15 and the machine tool 2 are caused to generate a control signal and an operation status signal, respectively, so that the identification unit 13 can acquire identification data, that is, data that the identification unit 13 uses when executing the identification processing (described later).The identification operation command, which is a command generated for the identification operation, includes a spindle rotation speed command and a feed rate command.

[0017] The Fig. 2 to 4 are diagrams illustrating exemplary patterns of identification operation commands generated by the identification operation generation unit 14 according to the first embodiment. A pattern of an identification operation command is hereinafter also referred to as a command pattern. Fig. 2 to 4 represent command patterns in which the spindle rotation speed and the feed rate change continuously between the identification operation start time t1 and the identification operation end time t2. Fig. 2 to 4, the horizontal axis represents time (points in time), the upper vertical axis represents the spindle rotation speed, and the lower vertical axis represents the feed rate. The spindle rotation speed and the feed rate are hereinafter referred to as S and F, respectively.

[0018] S0 is the reference spindle speed, i.e., the spindle speed before the identification operation, and S1 is the maximum spindle speed during the identification operation. T1 is a time constant in which the spindle speed increases from S0 to S1. T2 is a time constant in which the feed rate increases from F0 to F1. Fig. 2 shows a command pattern in which the spindle speed and the feed rate are accelerated and decelerated separately. Fig. In the example illustrated in Figure 2, the spindle speed increases to S1 with time constant T1, then decreases. After decreasing to S0, the spindle speed remains at S0. Once the spindle speed has decreased to S0, the feed rate increases to F1 with time constant T2. Once F1 is reached, the feed rate then decreases.

[0019] Fig. 3 represents a command pattern in which, after increasing the spindle rotation speed, the feed rate increases and then decreases, and then the spindle rotation speed decreases. Fig. 4 shows a command pattern in which the spindle rotation speed increases and then decreases, and during the change of the spindle rotation speed, the feed rate repeatedly increases and decreases.

[0020] Although the Fig. 2 to 4 show examples in which the spindle rotation speed changes between S0 and S1, where S1 is defined as the maximum value of the spindle rotation speed during the identification operation. The identification operation generation unit 14 may set the minimum value S2 of the spindle rotation speed during the identification operation and generate a command pattern in which the spindle rotation speed changes within the range of S0 to S2. The same applies to the feed rate, and the minimum value F2 of the feed rate during the identification operation may be set, and a command pattern may be generated in which the feed rate changes between F0 and F2.

[0021] Although the Fig. While FIGS. 2 to 4 illustrate the triangular command patterns of increase and decrease, the identification operation generation unit 14 may generate any command pattern in which the spindle rotation speed and feed rate continuously increase and decrease. For example, the identification operation generation unit 14 may generate a sinusoidal or S-curve change command pattern instead of the triangular command patterns.

[0022] The identification operation generating unit 14 can generate an identification operation including various combinations of the spindle rotation speed and the feed rate by changing the spindle rotation speed and the feed rate independently of each other in the manner described above.

[0023] It is known that the magnitude of the cutting force generated when the tool cuts the workpiece mainly depends on the feed rate per edge, and the vibration period of the cutting force mainly depends on the spindle rotation speed. For this reason, the spindle rotation speed and the feed rate are generally changed in the same proportion. Consequently, the load applied to the tool cutting edge remains constant, and thus the magnitude of the cutting force generated per tool edge does not change. Since the identification operation generation unit 14 changes the spindle rotation speed and the feed rate independently of each other, the magnitude and amplitude of the cutting force can undergo various changes, and various types of vibrations of the machine tool 2 can be generated during the identification operation, as described later.

[0024] Based on the identification operation command generated by the identification operation generation unit 14, the drive control unit 15 generates a control signal for controlling the machine tool 2 so that the spindle and feed shaft of the machine tool 2 operate as specified by the identification operation command. The control signal is a command for the spindle and feed shaft of the machine tool 2 and includes at least one of a position command, a speed command, and a current command for each motor of the spindle and feed shaft.It should be noted that the drive control unit 15 generates a control signal for the machine tool 2 based on a machining path and a reference spindle rotation speed and a reference feed rate for the machining path when no identification operation command is input from the identification operation generation unit 14, that is, during normal machining operation. Furthermore, the drive control unit 15 acquires a correction signal from the correction unit 11, as described later, corrects the control signal for the machine tool 2 based on the correction signal, and outputs the corrected control signal to the machine tool 2.

[0025] In the drive control unit 15, a machining path, as well as the reference spindle rotation speed and a reference feed rate for the machining path, are set in advance. A machining path, as well as a reference spindle rotation speed and a reference feed rate for the machining path, can be specified by a numerical control program. Even if an identification operation command is input from the identification operation generation unit 14, the drive control unit 15 does not change the set machining path, but generates a control signal to change only the spindle rotation speed and the feed rate according to the identification operation command.Each shaft of the machine tool 2 includes a motor and a motor controller. Each motor controller controls the motor based on a control signal received from the drive control unit 15 and a feedback signal, for example, regarding the position, speed, or motor current. Position and speed feedback signals are calculated based on the position detected by the linear encoder, and motor current feedback signals are calculated based on the detection result of the current sensor. Position, speed, and motor current feedback signals are hereinafter also referred to as position feedback signals, speed feedback signals, and current feedback signals, respectively.

[0026] The data acquisition unit 16 synchronizes a control signal output from the drive control unit 15 with an operating state signal indicating the operating state of the machine tool 2 operated based on the control signal, and outputs the thus synchronized signals as identification data. Specifically, the data acquisition unit 16, using the control signal output from the drive control unit 15 and the operating state signal output from the sensors of the machine tool 2, temporally synchronizes the data contained in these signals and outputs the thus synchronized data as identification data to the vibration determination unit 12 and the identification unit 13. The operating state signal, as described above, is a signal indicating the operating state of the machine tool 2 and includes a signal from which the vibration of at least one of the tool and the workpiece can be detected.Since the machine tool includes the linear encoder, the current sensor, and the force sensor as the sensors discussed above, the data acquisition unit 16 can acquire, as the operating state signal, feedback signals about the position and speed of the spindle and the feed shaft, a feedback signal about the current, and the force or torque detected by the force sensor. The actual measured values of the force or torque as detected by the force sensor are hereinafter also referred to as force information. Since the operating state signal is generated after the machine tool receives the control signal, the operating state signal is delayed in time from the corresponding control signal due to the influence of, for example, the time required for communication.The data acquisition unit 16 compensates for the timing difference between the operating state signal and the control signal by shifting the data contained in the operating state signal or the data contained in the control signal by a time corresponding to the difference, for example, from the communication time. The data acquisition unit 16 collects the data with the collected timing difference, i.e., the synchronized data, into identification data and outputs the identification data to the vibration determination unit 12 and the identification unit 13.

[0027] The vibration determination unit 12 determines whether vibration has occurred in the machine tool 2 using the identification data. If it is determined that vibration has occurred, the vibration determination unit 12 determines the type of vibration and outputs the determination result to the identification unit 13. Details about the vibration determination unit 12 will be described below. Note that the term "vibration" refers to vibration that has a larger amplitude than the vibration component resulting from the cutting force due to the tool and the workpiece, and the vibration determination unit 12 determines whether the vibration has occurred with this meaning.

[0028] The determination of vibration occurrence in the vibration determination unit 12 is carried out using a known means. For example, it is determined that vibration has occurred when a force or torque, as indicated by the force information output from the force sensor, exceeds a predetermined amplitude in a time domain. The type of signal used for vibration determination is not limited to force information; for example, the vibration determination unit 12 can determine whether vibration has occurred using a current feedback signal included in the operating state signal.Alternatively, the vibration determination unit 12 may convert a signal to be used for determining whether vibration has occurred into a signal in the frequency domain and determine that vibration has occurred when the vibration component having a maximum amplitude in the frequency domain exceeds a predetermined amplitude.

[0029] Meanwhile, vibration phenomena include forced vibrations and self-excited vibrations, and chatter vibrations are a type of self-excited vibration. Forced vibrations are vibration phenomena in which the cutting force serves as a source of excitation to excite a structure located near the tool or workpiece. It is known that due to this property, the vibration frequency of forced vibrations is an integer multiple of the fundamental cutting frequency. On the other hand, chatter vibrations, which are self-excited vibrations, are a vibration phenomenon that occurs when a system defined by the displacement of the structure and the cutting force becomes unstable. It is known that due to this property, the vibration frequency of chatter vibrations is a non-integer multiple of the fundamental cutting frequency.The basic cutting frequency as used above is a frequency resulting from multiplying the spindle rotation speed by the number of tool blades.

[0030] After determining that vibration has occurred, the vibration determination unit 12 determines the type of vibration. Specifically, the vibration determination unit 12 determines whether the occurring vibration is a forced vibration or a chatter vibration, thereby determining the type of vibration. The type of vibration is determined based on whether the determined vibration frequency is an integer multiple of the basic cutting frequency. That is, the vibration determination unit 12 determines that the vibration is a forced vibration when the vibration frequency is an integer multiple of the basic cutting frequency, and determines that the vibration is a chatter vibration when the frequency is a non-integer multiple of the basic cutting frequency.

[0031] It should be noted that after determining that no vibration has occurred, the vibration determination unit 12 determines that the state is stable machining. Stable machining is a machining state in which only the vibration component resulting from the cutting force of the tool and workpiece occurs without vibration excitation, approximately at the natural frequency of the structure.

[0032] The vibration determination unit 12 constantly performs the above processing to determine whether the identification data associated with each time point indicates stable machining, forced vibration, or chatter vibration, and outputs the determination result to the identification unit 13 as a vibration determination result. That is, the vibration determination unit 12 determines, based on the identification data, whether the vibration state of the machine tool 2 is stable machining, forced vibration, or chatter vibration.

[0033] Based on the determination result of the vibration determination unit 12, the identification unit 13 selects an identifiable characteristic machining parameter as a selected parameter from the characteristic machining parameters and identifies the selected parameter using the identification data input from the data acquisition unit 16. Based on the determination result of the vibration determination unit 12, the identification unit 13 further selects an identifiable characteristic dynamic parameter as a selected parameter from the characteristic dynamic parameters. Selected parameters are hereinafter also referred to as identifiable parameters. The identification unit 13 outputs the result of the identification processing to the correction unit 11.Identification processing is performed using identification data and machining condition information. Machining condition information, which is information indicating machining conditions in the identification operation, is preset in the identification unit 13. The machining condition information includes, for example, a tool diameter, the number of tool cutting edges, a tool helix angle, the axial cutting amount of the tool, the radial cutting amount of the tool, and a machining mode representing upcut or downcut.

[0034] Note that in the following description, an example is given in which the identification unit 13 identifies both dynamic characteristic parameters and machining characteristic parameters, but the identification unit 13 may identify either dynamic characteristic parameters or machining characteristic parameters. For example, based on the determination result by the vibration determination unit 12, the identification unit 13 selects an identifiable machining characteristic parameter as a selected parameter from the machining characteristic parameters and identifies the selected parameter using the identification data.

[0035] Generally, the spindle speed and feed rate are specified as constant values during machining. In this case, the identification unit 13 can only acquire identification data for machining with a single set of spindle speed and feed rate. Since the identification data includes an operating status signal detected by the sensors of the machine tool 2, as described above, the identification unit 13 can only acquire an operating status signal for machining with a single set of spindle speed and feed rate.According to the present embodiment, the identification operation generation unit 14 generates commands that enable continuous change of each of the spindle rotation speed and the feed rate, so that the identification unit 13 can obtain operation status signals for machining with different combinations of spindle rotation speed and feed rate at different times.

[0036] Now, characteristic dynamic parameters and characteristic machining parameters are described. Characteristic dynamic parameters, which are parameters representing the characteristics of a dynamic model (described later), represent the vibration characteristics of machine tool 2. Characteristic dynamic parameters include, for example, an equivalent mass, a damping coefficient, and a natural frequency. Characteristic machining parameters, which are parameters representing the characteristics of a machining process model (described later), represent the characteristics of a machining phenomenon between the tool and the workpiece. Characteristic machining parameters include, for example, a specific cutting resistance, an edge force, a tool eccentricity, and a tool removal width.

[0037] A dynamics model is a mathematical model that describes the dynamics of the mechanical structures within the machine tool, the tool, and the workpiece. An example of a dynamics model is described below. Fig. 5 is a schematic diagram illustrating the transmission of disturbance forces to a table in the case where the workpiece fixed to the table is vibrated by the cutting force in the first embodiment. Fig. Figure 5 illustrates an example in which the machine tool 2 performs milling by rotating a tool 33. The Fig. The example illustrated in Figure 5 is based on the assumption that a workpiece 32 is placed on a table 31, with a drive shaft and a tool system 34 being provided, which provides a spindle that holds the tool 33. In Fig. 5, a relative displacement 35 indicates a relative displacement of the workpiece end in the vibration direction relative to the table 31, a cutting force 36 indicates the cutting force on the workpiece 32, and a disturbance force 37 indicates the disturbance force transmitted to the table 31. In this case, the relationship between the cutting force 36, the disturbance force 37, and the relative displacement 35 can be expressed by the following formula (1). The dynamic model represented by formula (1) is a mathematical model for calculating: the disturbance force 37 transmitted to the feed shaft by the mechanical structure including the tool 33 or the workpiece 32 when the cutting force 36 is generated; and the positional deviation occurring on each feed shaft due to the mechanical structure when the cutting force 36 is generated. [Formula 1] fc=mtx¨+ctx˙+kt+ktxfd=ctx˙+ktx} where f c : cutting force, fd : disturbance force, mt: equivalent mass, x: relative displacement of the workpiece end in the direction of vibration with respect to the table ct=2mtςωn, kt=mtωn2, ζ: damping coefficient t, ω n : Natural frequency

[0038] The dynamic model represented by formula (1), which is a model with the workpiece 32 on the table 31 and described as a vibration system with a single degree of freedom, is a non-limiting example of a dynamic model. For example, the dynamic model may provide a vibration system with multiple degrees of freedom described as including the table 31 and a fixture that fixes the workpiece 32. Furthermore, a dynamic model may be specified with respect to a tool-side structure including the tool 33, the tool system 34, and the spindle motor. Furthermore, a dynamic model may be specified as a vibration system provided by a combination of a tool-side structure and a workpiece-side structure, including a fixture that fixes the workpiece 32 and the table 31.

[0039] A machining process model is a mathematical model that describes a cutting process between the tool and the workpiece. An example of a machining process model is expressed by the following formula (2). [Formula 2] fc=(Kcah(φ(t))+Kce)g(φ(t)) f c : Cutting force, K c : specific cutting force, K ce : edge force, a: axial cutting amount of the tool h: workpiece cutting thickness Φ: angle of rotation of the tool, t: time g(φ(t))={1(φs≤φ(t)≤φf)0(φ(t)<φs,φf<φ(t)) Φ s : Tool pressure angle, Φ f : Tool release angle

[0040] Formula (2) is a mathematical expression for calculating the cutting force exerted by the tool 33 on the workpiece 32, based on a cutting thickness corresponding to the rotation angle of the tool 33 at any given time. The cutting thickness refers to the thickness by which a tool cutting edge, which is a cutting edge of the tool 33, cuts the workpiece 32 when passing through the workpiece 32. A cutting force is calculated as a value greater than or equal to zero when the tool cutting edge is at such an angle that the tool cutting edge is in contact with the workpiece 32, as shown in the Fig. 6 and Fig. 7. However, the cutting force is calculated as zero when the tool cutting edge is at an angle such that the tool cutting edge has no contact with the workpiece 32. Fig. 6 is a diagram illustrating an exemplary rotation angle of the tool 33 at which the tool cutting edge is in contact with the workpiece 32 according to the first embodiment. Fig. 7 is a diagram illustrating an example rotation angle of the tool 33 at which the tool cutting edge is not in contact with the workpiece 32. That is, based on the positional deviation, it is determined whether the tool cutting edge is in contact with the workpiece at each rotation angle of the tool 33 or at each time. When the tool cutting edge is in contact with the workpiece 32, the cutting thickness is calculated. When the tool cutting edge is not in contact with the workpiece 32, the cutting thickness is calculated as zero.

[0041] The calculation represented by formula (2) is performed for the three directions—the tangential direction, the radial direction, and the axial direction of the tool—to provide the cutting force in the three directions. In the machining process model, the cutting force in the tool reference coordinate system is calculated through a coordinate transformation in which the cutting force having components in the above three directions is multiplied by a rotation matrix corresponding to the tool rotation angle, that is, the rotation angle of the tool 33. An example of a coordinate transformation is expressed by formula (3). [Formula 3] [fcxfcyfcz]=[cos φ(t)sin φ(t)0−sin φ(t)cos φ(t)0001][fctfcrfca] f cx : X-axis cutting force, f cy : Y-axis cutting force, f cz : Z-axis cutting force, f ct : Tool tangential cutting force, f cr : tool radial cutting force, f ca: Tool axial cutting force

[0042] The calculations represented by formulas (2) and (3) are performed according to the number of tool cutting edges, and the calculation results are added together to obtain the resulting value, which represents the cutting force generated by the entire tool. The machining process model represented by formula (2) is a mathematical model for calculating a cutting thickness based on the tool rotation angle and the relative position between the tool cutting edge and the workpiece 32 to be machined by the tool 33, and calculating the cutting force generated between the tool and the workpiece based on the cutting thickness. The cutting thickness in formula (2) can be calculated using formula (4) using the tool rotation angle and the feed amount per edge. [Formula 4] h(φ(t))=c sin φ(t) C: Feed rate per edge

[0043] As another example, a cutting thickness can also be calculated using the formula (5). [Formula 5] h(φ(t))=c sin φ(t)+{v(φ,t)−w(φ,t)}+Δr(φ,t,Ntooth) v: displacement amount of the tool center in the tool radial direction, w: displacement amount of the previously machined surface in the tool radial direction, Δr: Correction amount corresponding to each tool cutting edge, N tooth : Number of the tool cutting edge

[0044] Formula (5) is a formula for calculating cutting thickness. Formula (5) is formula (4) to which a variation amount and a correction amount are added. The variation amount is calculated based on the difference between the current tool displacement and the previously machined surface, that is, the machined surface provided by the previous tool cutting edge, that is, one edge before. The correction amount corresponds to each tool cutting edge. Among the displacement amount of the current tool cutting edge and the displacement amount of the one or more tool cutting edges that are one or more cutting edges before, there is a displacement amount that affects the shape of the machined surfaces.The calculation represented by formula (5) modifies the cutting thickness with the difference between the displacement amount of the current tool cutting edge and the displacement amount that affects the shape of the machined surface. That is, among the one or more tool cutting edges that are one or more edges forward of the current tool cutting edge, there is a tool cutting edge that affects the shape of the machined surface. The cutting thickness is calculated based on the difference between the trajectory of the current tool cutting edge involved in the cutting operation and the trajectory of the tool cutting edge that affects the shape of the machined surface.

[0045] The relative displacement x of formula (1) includes a component in the direction from the tool center to the tool cutting edge, and the displacement amount v of the tool center is a displacement amount corresponding to this component. In addition, the displacement amount w of the previously machined surface is a displacement amount generated in the machined surface by the relative displacement x at the time of cutting with the one or more tool cutting edges that are one or more edges ahead. Note that "the one or more tool cutting edges that are one or more edges ahead" refers to the tool cutting edges that participate in cutting operations at times before the reference tool cutting edge participates in cutting.For example, assume the tool has two edges, and the tool cutting edge currently performing a cutting operation is a second cutting edge. A "tool cutting edge one edge ahead" is a first edge that is 180 degrees behind the second edge. A "tool cutting edge two edges ahead" is a second edge that is 360 degrees behind the second edge. A "tool cutting edge three edges ahead" is a first edge that is 540 degrees behind the second edge.The cutting edge temporarily moves away from the workpiece 32 due to the translation of the tool during a cutting operation, in which case the current tool cutting edge intersects not only the previously machined surface created by the tool cutting edge one edge before, but also the previously machined surface created by the tool cutting edge two or more edges before.

[0046] The calculation represented by formula (5) further modifies the cutting thickness with a correction amount corresponding to the tool rotation angle and a tool cutting edge number, i.e., a number indicating the tool cutting edge. In formula (5), the correction amount is introduced to modify a variation in cutting thickness, the variation occurring due to cutting operations with different turning radii for different tool cutting edges. The correction amounts must be introduced in formula (5) in the situations discussed below. For example, if abrasion or flaking or the like occurs at a specific cutting edge, the turning radius of this tool cutting edge is shorter than that of another tool cutting edge. In such a case, a correction amount corresponding to the abrasion width, flaking width, or the like should be added.Alternatively, a tool with replaceable cutting edges may contain an error in the attachment of a tool cutting edge, in which case a correction amount corresponding to this attachment error should be added. Alternatively, the spindle pivot point may not align with the tool center, meaning that tool eccentricity exists. In this case, a correction amount corresponding to the tool eccentricity amount should be added. It should be noted that the tool center is the center of the tool's circumference.

[0047] The tool eccentricity amount is an amount by which the turning radius of each tool cutting edge increases or decreases to thereby modify the cutting thickness when there is a deviation amount between the center of the tool center and the pivot point of the spindle, as shown in the Fig. 8 and Fig. 9 illustrates. Fig. 8 is a diagram illustrating cutting with a first cutting edge when there is a deviation amount between the center of the tool center and the fulcrum of spindle rotation in the first embodiment. Fig. Figure 9 is a diagram illustrating cutting with a second cutting edge when there is a deviation amount between the center of the tool and the spindle pivot point. The first cutting edge 43 and the second cutting edge 44 are the cutting edges of the tool. In the examples shown in the Fig. 8 and Fig. 9, a deviation exists between a center 41 of the tool and a pivot point 42 of the spindle. In such a case, if there is no deviation, it is necessary to modify the cutting thickness, and the tool eccentricity amount indicates a modification amount by which this cutting thickness is to be modified. That is, the tool eccentricity amount, which depends on the rotation angle of the tool 33, is added to or subtracted from the cutting thickness. The above cases in which the cutting thickness is modified by a modification amount are non-limiting examples, and the modification amount can be appropriately changed according to a phenomenon occurring at the tool cutting edge.

[0048] It should be noted that the machining process model of formula (2) is a non-limiting example. For example, formula (2) can be used to provide different values of a specific cutting force in different cases, where: the cutting speed is greater than or equal to a threshold value; and the cutting speed is less than the threshold value. In addition, a process damping force can be added to the right side of formula (2). The process damping force is the force generated by the contact of the flank surface of the tool cutting edge with the workpiece. The process damping can be expressed, for example, as a value obtained by multiplying the flank contact area by a process damping coefficient. In this case, the process damping coefficient serves as one of the characteristic machining parameters.

[0049] Alternatively, a machining process model for a tool with a helix angle can also be used. Specifically, such a model can divide the tool into tools, each with a minute thickness in the axial direction, calculate the cutting force in each divided tool with the minute thickness, and add the thus calculated cutting forces in the axial direction of the tool to provide the final cutting force. Another example of a model can calculate the cutting thickness and cutting force through finite element analysis.

[0050] The following describes processing that uses formulas (1) and (2) as a dynamic model and a machining process model, respectively, determines identifiable parameters from a vibration determination result, and identifies these parameters. Note that candidates for the identifiable parameters described below are an equivalent mass, a damping coefficient, and a natural frequency, as well as a specific cutting force, an edge force, and a tool eccentricity value. The equivalent mass, the damping coefficient, and the natural frequency are characteristic dynamic parameters. The specific cutting force, the edge force, and the tool eccentricity value are characteristic machining parameters.

[0051] After receiving an input of a vibration determination result indicating stable machining, forced vibration, or chatter vibration from the vibration determination unit 12, the identification unit 13 performs the following processing according to the vibration determination result. Note that in a rare case where forced vibration and chatter vibration occur simultaneously, it is determined that chatter vibration is occurring and identification is performed. [Case where the determination result is a stable processing]

[0052] The identification unit 13 selects a specific cutting force and an edge force as identifiable parameters, where the forces are characteristic machining parameters. Furthermore, the identification unit 13 identifies the specific cutting force and the edge force through the following processing. The identification unit 13 calculates the specific cutting resistance and the edge force according to formulas (2) to (4) using the force information output from the force sensor and the machining conditions recorded in advance in the identification unit 13. That is, the specific cutting force and the edge force in formula (2) are calculated so that the value of the force in each axial direction, calculated from formula (3) with formulas (2) and (4) substituted therein, substantially corresponds to the actual measured value of the force detected by the force sensor.Any known optimization method or numerical simulation can be used to calculate the specific cutting force and edge force. For example, a least-squares method or a gradient method can be used. [Case where the determination result is forced vibration]

[0053] The identification unit 13 selects a damping coefficient, a natural frequency, a specific cutting force, and an edge force as identifiable parameters. The damping coefficient and the natural frequency are characteristic dynamic parameters. The specific cutting force and the edge force are characteristic machining parameters. Furthermore, the identification unit 13 identifies the damping coefficient, the natural frequency, the specific cutting force, and the edge force through the following processing.

[0054] The identification unit 13 identifies the damping coefficient, the natural frequency, the specific cutting resistance, and the edge force according to formulas (1) to (4) using the force information output by the force sensor and the machining conditions recorded in advance in the identification unit 13. Specifically, the actual measured value of the force detected by the force sensor is expressed as f d in the following formula (6), where formula (6) is a modified formula (1). [Formula 6] f¨d=2ςωn(f˙c−f˙d)+ωn2(fc−fd)

[0055] In addition, the value of the force in each axial direction, calculated using formula (3) with formulas (2) and (4) replaced therein, is expressed in f cof formula (6). At this time, there are a combination of a damping coefficient and a natural frequency, and a combination of a specific cutting force and an edge force, and these combinations apply to formula (6). The identification unit 13 calculates a combination of a damping coefficient and a natural frequency, and a combination of a specific cutting force and an edge force, so that the calculated combinations satisfy formula (6). Specifically, the identification unit 13 searches for the damping coefficient, the natural frequency, the specific cutting force, and the edge force using a gradient method so that the error between the two sides of formula (6) is minimized. Alternatively, the damping coefficient, the natural frequency, the specific cutting force, and the edge force may be calculated using a least squares method. [Case where the determination result is a chatter vibration]

[0056] The identification unit 13 selects an equivalent mass, a damping coefficient, a natural frequency, a specific cutting force, an edge force, and a tool eccentricity amount as identifiable parameters. The equivalent mass, the damping coefficient, and the natural frequency are characteristic dynamic parameters. The specific cutting force, the edge force, and the tool eccentricity amount are characteristic machining parameters. Furthermore, the identification unit 13 identifies the equivalent mass, the damping coefficient, the natural frequency, the specific cutting resistance, the edge force, and the tool eccentricity amount through the following processing.

[0057] The identification unit 13 identifies the equivalent mass, damping coefficient, natural frequency, specific cutting force, edge force, and tool eccentricity amount according to formulas (1), (2), (3), and (5) using the force information output from the force sensor and the machining conditions recorded in advance in the identification unit 13. Specifically, the equivalent mass, damping coefficient, natural frequency, specific cutting force, edge force, and tool eccentricity amount can be identified according to the formulas (1), (2), (3), and (5) Fig. 10 illustrated procedure.

[0058] Fig. 10 is a flowchart illustrating an exemplary identification procedure in the identification unit 13 according to the first embodiment when the vibration determination unit 12 provides a vibration determination result of chatter vibration. First, in step S1, the identification unit 13 sets initial values for a set of parameters. This set of parameters is composed of a combination of characteristic dynamic parameters and a combination of characteristic machining parameters. The characteristic dynamic parameters are an equivalent mass, a damping coefficient, and a natural frequency, and the characteristic machining parameters are a specific cutting force, an edge force, and a tool eccentricity amount.

[0059] In step S2, the identification unit 13 calculates displacement amounts that simultaneously satisfy the dynamic model and the machining process model. For example, the identification unit 13 calculates a displacement amount that simultaneously satisfies formula (1), which is the dynamic model, and formulas (2) and (5), which are the machining process models. The displacement amounts are the relative displacement x of formula (1) and v and w of formula (5).

[0060] In step S3, the identification unit 13 calculates the disturbance force using the dynamic model, taking the displacement amount into account. For example, the identification unit 13 calculates the disturbance force f d by substituting the displacement amount calculated in step S2 into formula (1), which is the dynamic model.

[0061] In step S4, the identification unit 13 determines whether the error between the actual measured value of the force detected by the force sensor and the force value calculated in step S3 is less than or equal to an allowable value. If the error is less than or equal to the allowable value (Yes in step S4), the identification unit 13 considers the values of the parameter set at this time as an identification result and terminates the identification processing. If the error exceeds the allowable value (No in step S4), the identification unit 13 updates the values of the parameter set in step S5 and returns to step S2.

[0062] The method for updating the parameters in step S5 may, for example, include increasing or decreasing each parameter by a predetermined amount. Note that when the vibration determination unit 12 provides a vibration determination result of a chatter vibration, the identification processing in the identification unit 13 is not limited to the above-described procedure of steps S1 to S5. For example, formulas (1), (2), (3), and (5) may be treated as a set of simultaneous equations, and each parameter may be calculated using a least squares method.

[0063] With further reference to Fig. 1, the correction unit 11 receives the characteristic dynamic parameters and the characteristic machining parameters, which are an identification result from the identification unit 13. Based on the identification result, the correction unit 11 outputs a correction signal for correcting the operation of the machine tool 2 to the drive control unit 15. Specifically, in the correction unit 11, a simulation regarding the mechanical dynamics and the machining process is performed, and a combination of a spindle rotation speed and a feed rate at which the vibration amplitude of the tool cutting edge is less than or equal to a specified value is calculated.The correction unit 11 generates a correction signal for correcting the spindle rotation speed and feed rate based on the calculated spindle rotation speed and feed rate, and outputs the correction signal to the drive control unit 15. The specified value is a predetermined value in the correction unit 11 so that the machining result meets a given dimensional tolerance. Note that, in addition to the spindle rotation speed and feed rate, the targets to be corrected may also include the cutting amount in the axial direction of the tool or the radial direction of the tool.

[0064] An example of the operation of the numerical control device 1 according to the first embodiment described above will be explained with reference to Fig. 11 described. Fig. 11 is a flowchart illustrating an example of the operation of the numerical control device 1 according to the first embodiment. In step S11, the numerical control device 1 starts an identification operation. Specifically, the identification operation generation unit 14 generates an identification operation command, and the drive control unit 15 outputs a control signal to the machine tool 2 so that the machine tool 2 executes the operation specified by the identification operation command.

[0065] In step S12, the vibration determination unit 12 acquires identification data. Specifically, the data acquisition unit 16 acquires the control signal from the drive control unit 15, acquires an operating state signal from the sensors of the machine tool 2, generates identification data that compensates for the time difference between the two signals, and outputs the identification data to the vibration determination unit 12 and the identification unit 13.

[0066] In step S13, the vibration determination unit 12 determines the vibration state based on the identification data. Specifically, the vibration determination unit 12 determines whether vibration has occurred based on the operating state signal of the identification data, and if it is determined that no vibration has occurred, it determines that the vibration state is stable machining. If it is determined that vibration has occurred, the vibration determination unit 12 determines whether the vibration is forced vibration or chatter vibration based on the frequency of the vibration. The vibration determination unit 12 outputs the determination result about the vibration state to the identification unit 13 as a vibration determination result.

[0067] In step S14, the identification unit 13 selects identifiable parameters based on the identification data and the vibration determination result. Specifically, the identification unit 13 selects identifiable parameters from the characteristic dynamic parameters and the characteristic machining parameters according to the vibration determination result.

[0068] In step S15, the identification unit 13 identifies the identifiable parameters selected in step S14 using the identification data. After the end of the identification operation in step S15, that is, in the normal machining operation, the numerical control device 1 corrects the operation of the machine tool 2 in step S16 based on the identification result. Specifically, the correction unit 11 generates a correction signal for correcting the operation of the machine tool 2 based on the identification result calculated by the identification unit 13 and outputs the correction signal to the drive control unit 15. The drive control unit 15 generates a control signal based on the machining path, the reference spindle rotation speed, and the reference feed rate for the machining path, as well as the correction signal, and outputs the control signal to the machine tool 2.

[0069] The numerical control device 1 can perform parameter identification by executing the series of processes from step S11 to step S15 in real time during machining. Furthermore, step S16 is performed after the identification operation, so that the machining state can be improved using the identification result.

[0070] Next, a hardware configuration of the numerical control device 1 will be described. Each unit of the Fig. The numerical control device 1 illustrated in FIG. 1 is implemented by a processing circuit. The processing circuit may be a circuit including a processor or dedicated hardware.

[0071] In a case where the processing circuit is a circuit that includes a processor, the processing circuit is, for example, a processing circuit having the Fig. 12 illustrated configuration. Fig. Fig. 12 is a diagram illustrating an exemplary configuration of a processing circuit according to the first embodiment. The processing circuit 200 includes a processor 201 and a memory 202. In a case where each unit of the numerical control device 1 is controlled by the Fig. 12, the processor 201 reads and executes a program stored in the memory 202, thereby implementing them. That is, in a case where each unit of the numerical control device 1 is controlled by the processing circuit 200 shown in Fig. 12, these functions are implemented using a program, which is software. The memory 202 is also used as a working area of the processor 201. The processor 201 is a central processing unit (CPU) or the like. The memory 202 is, for example, a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read-only memory (ROM), a flash memory, a magnetic disk, or the like.

[0072] In a case where the processing circuit implementing each unit of the numerical control device 1 is dedicated hardware, the processing circuit is, for example, a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC). Note that each unit of the numerical control device 1 may be implemented by a combination of a processing circuit including a processor and dedicated hardware. Each unit of the numerical control device 1 may be implemented by a plurality of processing circuits.

[0073] As described above, the numerical control device 1 according to the first embodiment generates a command to continuously change the speeds of the spindle and the feed shaft and outputs the command to the spindle and the feed shaft separately, thereby causing the machine tool to perform an identification operation. Then, the numerical control device 1 according to the first embodiment determines the vibration state of the machine tool 2 based on the identification data collected by the identification operation and identifies identifiable characteristic machining parameters according to the determination result. The numerical control device 1 according to the first embodiment can thus identify characteristic machining parameters efficiently and in a short time.Furthermore, the numerical control device 1 according to the first embodiment can also identify identifiable characteristic dynamic parameters according to the determination result regarding the vibration state. Furthermore, since the numerical control device 1 according to the first embodiment can reproduce multiple types of vibration states of the machine tool 2 during a single identification operation, it is possible to efficiently perform the identification in a short time without requiring the operator to sequentially change the machining conditions. Furthermore, the reproduction of a chatter vibration state enables the simultaneous estimation of characteristic dynamic parameters and characteristic machining parameters.As a result, the numerical control device 1 according to the first embodiment can correct the control signal for the machine tool based on the identification result, allowing machining to continue without causing machining defects. When the identification is performed by changing the spindle rotation speed stepwise, peak values that are candidates for the natural frequency can only be discretely searched. On the other hand, the present embodiment generates a command to continuously change the rotation speeds of the spindle and feed shaft as described above, making it possible to identify characteristic dynamic parameters and characteristic machining parameters with higher accuracy than when the spindle rotation speed is changed stepwise.

[0074] It should be noted that the dynamic model and the machining process model in formulas (1) and (2) are non-limiting examples and can be changed accordingly depending on the machine structure and machining method. Therefore, the characteristic dynamic parameters are not limited to the equivalent mass, damping coefficient, and natural frequency. Likewise, the characteristic machining parameters are not limited to the cutting force resistance, edge force, and tool eccentricity amount. The characteristic dynamic parameters and the characteristic machining parameters can be changed accordingly depending on the dynamic model and the machining process model, and in this case, effects similar to those of the present first embodiment can also be achieved.

[0075] Although the first embodiment describes the configuration in which one machine tool 2 is controlled by one numerical control device 1, two or more machine tools may be connected to the numerical control device 1. For example, a spindle rotation speed change command is generated for the first machine tool, a feed rate change command is generated for the second machine tool, and the operation commands are output to these machine tools simultaneously. In this case, the effect of completing the identification in a shorter time than when a single machine tool is operated can be achieved. Although the first embodiment describes the machine tool 2 that performs milling by rotating the tool, the present invention is also applicable to a machine tool that performs turning by rotating the workpiece.

[0076] Although the present first embodiment describes the configuration in which the force is directly detected by the force sensor, the force may be estimated indirectly using another sensor, and similar effects to those of the first embodiment can be achieved in this case as well. For example, the data acquisition unit 16 or the identification unit 13 can calculate the force using the following formula (7) using a reference motor current, that is, a motor current command, and a position detected by the linear encoder. [Formula 7] fixed=KTIRef−Mu¨ F est : Disturbance force of the servo axis, K T : torque coefficient, I ref : reference motor current, M: equivalent mass of the feed axis, u: Detection position of the linear encoder

[0077] Alternatively, an acceleration sensor can be used to calculate the force in a similar manner. In this case, the data acquisition unit 16 or the identification unit 13 can calculate the force using the acceleration detected by the acceleration sensor, using the following formula (8). [Formula 8] fixed=KTIref−Mα α: Detection amount of the acceleration sensor

[0078] Formulas (7) and (8) are force calculation formulas in which the feed shaft is considered as a single-inertia mass. However, a calculation formula in which the feed shaft is considered as a multi-inertia mass can be used appropriately according to the structure of the feed shaft. In addition, a term can be added to compensate for the friction force. Second embodiment

[0079] Fig. 13 is a block diagram illustrating an exemplary configuration of a numerical control device according to the second embodiment of the present invention. In the first embodiment, an example was described in which the identification processing is performed based on the control signal and the operation state signal obtained during a single execution of the identification operation. In the first embodiment, some of the dynamic characteristic parameters and the machining characteristic parameters cannot be identified if chatter vibration does not occur during a single identification operation. The present second embodiment describes an example in which the identification operation is modified if chatter vibration does not occur during the execution of the identification operation.Components having the same functions as those of the first embodiment are denoted by the same reference numerals below, and redundant descriptions are omitted. The following description mainly focuses on how the second embodiment differs from the first embodiment.

[0080] As in Fig. As illustrated in Fig. 13, the numerical control device 1a is the same as that according to the first embodiment, except that an identification unit 13a and an identification operation generation unit 14a are provided instead of the identification unit 13 and the identification operation generation unit 14 according to the first embodiment. The identification unit 13a and the identification operation generation unit 14a are implemented by processing circuits similar to the identification unit 13 and the identification operation generation unit 14 according to the first embodiment.

[0081] As with the identification unit 13 according to the first embodiment, the identification unit 13a selects identifiable parameters from the dynamic characteristic parameters and the machining characteristic parameters using the vibration determination result input from the vibration determination unit 12. Furthermore, like the identification unit 13 according to the first embodiment, the identification unit 13a performs identification processing to identify the selected identifiable parameters based on the identification data input from the data acquisition unit 16 and outputs the result of the identification processing to the correction unit 11.The identification processing is performed using the identification data and the information on the machining conditions in the same manner as that performed by the identification unit 13 according to the first embodiment.

[0082] At least one of the characteristic dynamic parameters and the characteristic machining parameters is preset as an identification target parameter in the identification unit 13a. If one or more of the identification target parameters remain unidentified after performing the identification processing one or more times, the identification unit 13a outputs an identification operation modification signal to the identification operation generation unit 14a (described later). The identification operation modification signal is a signal indicating that an unidentified characteristic dynamic parameter or a characteristic machining parameter exists.

[0083] Like the identification operation generation unit 14 according to the first embodiment, the identification operation generation unit 14a generates an identification operation command for changing the spindle rotation speed and the feed rate of the machine tool and outputs the identification operation command to the drive control unit 15.

[0084] Furthermore, the identification operation generation unit 14a modifies the command pattern for the identification operation based on the identification operation modification signal output from the identification unit 13a. Like the identification unit 13, the identification unit 13a can identify the largest number of parameter types when chatter vibrations occur in the machine tool. Therefore, the identification operation generation unit 14a changes the change range of the spindle rotation speed or the feed rate to modify the identification operation so that chatter vibration occurs during the identification operation.Specifically, the identification operation generation unit 14a generates an identification operation command pattern in which at least one of the maximum value S1 and the minimum value S2 of the spindle rotation speed and the maximum value F1 and the minimum value F2 of the feed rate described above is changed in a predetermined relationship. For example, specifically, at least one of the maximum value S1 and the minimum value S2 of the spindle rotation speed and the maximum value F1 and the minimum value F2 of the feed rate is changed so that at least one of the spindle rotation speed and the feed rate is changed within a range different from the range specified in the previous identification operation.

[0085] An example of the operation of the numerical control device 1a according to the second embodiment described above will be explained with reference to Fig. 14 described. Fig. 14 is a flowchart illustrating an example of the operation of the numerical control device 1a according to the second embodiment. In step S21, the numerical control device 1a starts an identification operation. Upon initial execution of step S21, the identification operation generation unit 14a generates an initial identification operation command, and the drive control unit 15 outputs a control signal to the machine tool so that the machine tool executes the operation specified by the identification operation command.

[0086] In steps S22 to S25, similar processes as in steps S12 to S15 are carried out in Fig. 11 described in the first embodiment. In step S26, the identification unit 13a determines whether the predetermined identification target parameters have been identified, and if the identification is completed (Yes in step S26), the operation of the numerical control device 1a proceeds to step S28. If one or more of the predetermined identification target parameters have not been identified (No in step S26), the numerical control device 1a modifies the identification operation command in step S27 and repeats the series of processes from step S21.Specifically, in step S27, the identification operation generation unit 14a outputs an identification operation modification signal to the identification operation generation unit 14a, and the identification unit 13a modifies the identification operation command to change the change range of at least one of the spindle rotation speed and the feed rate, and outputs the modified identification operation command to the drive control unit 15. In the second and subsequent executions of step S21, the drive control unit 15 generates a control signal for the machine tool 2 based on the modified identification operation command and outputs the control signal to the machine tool 2.

[0087] In step S28, the numerical control device 1a corrects the operation of the machine tool 2 based on the identification result. Specifically, like the correction unit 11 according to the first embodiment, the correction unit 11 generates a correction signal based on the identification result calculated by the identification unit 13a after the end of the identification operation and outputs the correction signal to the drive control unit 15. The drive control unit 15 generates a control signal based on the machining path, the reference spindle rotation speed, and the reference feed rate for the machining path, as well as the correction signal, and outputs the control signal to the machine tool 2.

[0088] The numerical control device 1a repeatedly executes the series of processes from step S21 to step S27 during processing. That is, if one or more of the identification target parameters, namely, the parameters set as targets to be identified, remain unidentified after the identification is performed using the identification data for the period of time corresponding to the identification operation command, the identification unit 13a generates an identification operation modification signal indicating an instruction to change the identification operation and outputs the identification operation modification signal to the identification operation generation unit 14a. Then, the identification operation generation unit 14a changes the identification command after receiving the identification operation modification signal.The data acquisition unit 16 synchronizes the control signal generated based on the modified identification operation command with the operating state signal indicating the operating state of the machine tool 2 operating based on the control signal. The data acquisition unit 16 then outputs the thus synchronized signals as identification data to the vibration determination unit 12 and the identification unit 13a. These operations are thereafter repeated until the identification of all parameters set as targets to be identified is completed. As a result, all the dynamic characteristic parameters and machining characteristic parameters set as targets to be identified can be identified. Furthermore, the processing of step S28 can improve the machining state using the identification result.Note that the procedure described above applies to modifying the identification operation command after completion of an identification operation. Alternatively, a procedure can be used to modify the identification operation in the middle of the identification operation.

[0089] As described above, the numerical control device 1a according to the second embodiment modifies the identification operation when one or more of the predetermined identification target parameters remain unidentified and performs the identification operation again. Therefore, the numerical control device 1a according to the second embodiment can achieve the effect that, even if there is a parameter that cannot be identified in the initial command pattern for the identification operation, the identification operation can be modified to cause chatter vibration, so that all the prespecified identification target parameters can be identified. Third embodiment

[0090] Fig. 15 is a block diagram illustrating an exemplary configuration of a numerical control device according to the third embodiment of the present invention. In the second embodiment, an identification operation is repeated until the identification of all identification target parameters defined internally in advance is completed. The present third embodiment describes an example in which an identification target parameter may be set externally. Components having the same functions as those of the second embodiment are denoted by the same reference numerals below, and redundant descriptions are omitted. The following description mainly focuses on how the third embodiment differs from the second embodiment.

[0091] As in Fig. As illustrated in FIG. 15, the numerical control device 1b according to the third embodiment includes, in addition to the components of the numerical control device 1a according to the second embodiment, an input unit 17. The input unit 17 is capable of receiving the input of an identification target parameter from the outside. For example, the input unit 17 is capable of receiving an input of at least one of the dynamic characteristic parameters and the machining characteristic parameters as an identification target parameter from an external device, an operator, or the like. The input unit 17 may be a communication circuit that communicates with an external device, an interface circuit of an external medium that reads data from the external medium, or an input means such as a keyboard or a mouse.In a case where the input unit 17 receives input from an operator, a display means such as a display or a monitor is also used as the input unit 17. An identification target parameter may be input to the input unit 17 as a numerical control program, or it may be interactively input to the input unit 17 by an operator. Furthermore, the input unit 17 may receive input of an identification target parameter in the form of interactive programming. The input unit 17 outputs the received identification target parameter to the identification unit 13a. An identification target parameter is specified by an operator or externally, for example, in the following two possible cases. The first case is "someone wants to exclude from identification a parameter that has already been identified by another means or the like."The second case is when "someone wants to reduce the time required for identification by identifying only high-priority identification targets." Regarding the first case, for example, the identified parameters have values obtained from a past identification, and these values are entered in advance and displayed in a menu list so that the unidentified parameters can be easily distinguished from the identified parameters. Regarding the second case, for example, an identification target parameter can be selected using a checkbox, and a display window shows the expected identification time, which changes each time a checkbox is selected.By providing the checkbox and display window, the operator can select the largest possible number of parameters, provided that the identification time for these selected parameters is within the allowable identification time. The form of interactive programming is not limited to these examples, and any method can be used. Displaying the information the operator considered when selecting parameters, as discussed above, allows the operator to easily select the target identification parameters.

[0092] The identification unit 13a uses the identification target parameters input from the input unit 17 instead of preset identification target parameters to perform the same operation as that performed by the identification unit 13a according to the second embodiment. Note that the identification unit 13a may be capable of performing both the operation using preset identification target parameters and the operation using the identification target parameters input from the input unit 17. The identification unit 13a outputs the result of the identification processing to the correction unit 11. The operation of the correction unit 11 is similar to that according to the first embodiment. Note that in the case where an identification target parameter is specified by a numerical control program, the operation of the correction unit 11 is as follows.Numerical control programs generally describe information such as machining paths, spindle rotation speeds, feed rates, and tool numbers. In a case where the operator specifies an identification target parameter from a numerical control program, a machining path for the identification operation and an identification target parameter are specified in the numerical control program. For example, after the identification unit 13a completes the identification, the correction unit 11 continues to generate correction signals to make the vibration amplitude of the tool cutting edge less than or equal to a specified value until the tool number is changed or until a machining path with a different specified identification operation is machined.Except for the differences described above, the operation of the numerical control device 1b according to the third embodiment is the same as that of the numerical control device 1a according to the second embodiment.

[0093] As described above, the numerical control device 1b according to the third embodiment modifies the identification operation in a case where one or more of the identification target parameters set by an external input remain unidentified and performs the identification operation again. Therefore, similar effects to those of the second embodiment can be achieved, and the identification target parameters can be changed according to the operator's request or the like. Fourth embodiment

[0094] Fig. 16 is a block diagram illustrating an exemplary configuration of a numerical control device according to the fourth embodiment of the present invention. In the third embodiment, the configuration in which an identification target parameter can be set externally was described. The present fourth embodiment describes a configuration in which a command pattern for the identification operation can also be set by an external input. Components having the same functions as those of the third embodiment are denoted by the same reference numerals hereinafter, and redundant descriptions are omitted. The following description mainly focuses on how the fourth embodiment differs from the third embodiment.

[0095] As in Fig. 16, the numerical control device 1c is the same as the numerical control device 1b according to the third embodiment, except that an identification operation generation unit 14b and an input unit 17a are provided instead of the identification operation generation unit 14a and the input unit 17.

[0096] Like the input unit 17 according to the third embodiment, the input unit 17a is capable of receiving an identification target parameter from the outside and outputting the received identification target parameter to the identification unit 13a. Furthermore, the input unit 17a is capable of receiving an input of command pattern information for determining a command pattern for the identification operation from the outside. The input unit 17a outputs the received command pattern information to the identification operation generation unit 14b. The command pattern information is, for example, information specifying the spindle rotation speeds S0 and S1, the feed rates F0 and F1, and the time constants T1 and T2 in the Fig. 2 to 4. That is, the command pattern information is information indicating the waveforms of the spindle rotation speed and the feed rate relative to the time when the spindle rotation speed and the feed rate are changed by the identification operation command. The command pattern information is input into the input unit 17a, for example, as a numerical control program or interactively. Alternatively, the command pattern information may also be input in the form of interactive programming. The command pattern information may additionally include the Fig. 2 to 4 or information indicating waveforms, so that the waveforms can also be set externally.

[0097] Similar to the input unit 17, the input unit 17a may be a communication circuit that communicates with an external device, an interface circuit of an external medium that reads data from the external medium, or an input means such as a keyboard or a mouse. In a case where the input unit 17a receives input from an operator, a display means such as a display or a monitor is also used as the input unit 17a. An identification target parameter and command pattern information may be input to the input unit 17a from an external device in the form of a numerical control program, or they may be interactively input to the input unit 17a by an operator.Furthermore, the input unit 17a can create a program in the form of interactive programming, and an identification target parameter and command pattern information can be specified by the program. The input unit 17a outputs the received identification target parameters to the identification unit 13a and outputs the received command pattern information to the identification operation generation unit 14b. The operations of the identification unit 13a and the correction unit 11 are similar to those in the third embodiment.

[0098] The input unit 17a receives command pattern information for identification, and the identification operation generation unit 14b generates a command pattern for the identification operation based on the received command pattern information for the identification operation and outputs the identification operation command to the drive control unit 15. Furthermore, the identification operation generation unit 14b modifies the command pattern for the identification operation based on the identification operation modification signal output from the identification unit 13a, like the identification operation generation unit 14a according to the second embodiment. Except for the differences described above, the operation of the numerical control device 1c according to the present embodiment is the same as that of the numerical control device 1b according to the third embodiment.

[0099] As described above, the numerical control device 1c according to the fourth embodiment allows specifying a command pattern for the identification operation through an external input, in addition to an identification target parameter as described in the third embodiment. Therefore, the numerical control device 1c according to the fourth embodiment can achieve the effect of calculating an identification result preferentially for a combination of parameters specified through an external input.

[0100] The configurations described in the above-mentioned embodiments provide examples of the content of the present invention. These configurations may be combined with other well-known techniques, and some of the configurations may be omitted or modified within a scope that does not deviate from the gist of the present invention. List of reference symbols

[0101] 1, 1a, 1b, 1c numerical control device; 2 machine tool; 11 correction unit; 12 vibration determination unit; 13 identification unit; 14 identification operation generation unit; 15 drive control unit; 16 data acquisition unit; 17, 17a input unit.

Claims

[1] A numerical control device for controlling the operation of a machine tool including a spindle and a feed shaft, the machine tool machining a workpiece with a tool, the numerical control device comprising: an identification operation generation unit for generating an identification operation command for independently and continuously changing a rotation speed of the spindle and a feed rate; a data acquisition unit for synchronizing a control signal for controlling the machine tool with an operating state signal and outputting the synchronized signals as identification data, the control signal being generated based on the identification operation command, the operating state signal indicating an operating state of the machine tool operated based on the control signal; a vibration determination unit for determining, based on the identification data, whether a vibration state of the machine tool is stable machining, chatter vibration, or forced vibration; and an identification unit for selecting, based on a determination result of the vibration determination unit, an identifiable characteristic machining parameter as a selected parameter from characteristic machining parameters representing features of a machining phenomenon between the tool and the workpiece, and for performing identification of the selected parameter using the identification data. [2] The numerical control device according to claim 1, wherein the identification unit further selects, based on the determination result of the vibration determination unit, an identifiable characteristic dynamic parameter as the selected parameter from characteristic dynamic parameters representing features of the vibration of the machine tool. [3] Numerical control device according to claim 1 or 2, wherein if one or more of the identification target parameters, which are parameters set as targets to be identified, remain unidentified after the identification has been performed using the identification data for a period of time corresponding to the identification operation command, the identification unit generates a command change signal indicating an instruction to change the identification operation and outputs the command change signal to the identification operation generation unit, the identification operation generation unit changes the identification operation command after receiving the command change signal, and the data acquisition unit synchronizes the control signal generated based on the changed identification operation command with an operation state signal indicating an operation state of the machine tool operated based on the control signal, and outputs the synchronized signals as the identification data to the vibration determination unit and the identification unit. [4] A numerical control device according to claim 3, comprising an input unit for receiving an input of the identification target parameters from the outside. [5] Numerical control device according to claim 4, wherein the input unit further receives an input of command pattern information from the outside, the command pattern information being information indicating waveforms of the rotation speed and the feed rate with respect to time when the rotation speed and the feed rate are changed by the identification operation command, and the identification operation generation unit generates the identification operation command based on the command pattern information. [6] A numerical control device according to claim 4 or 5, wherein the input unit receives an input from the outside as a numerical control program. [7] A numerical control device according to claim 4 or 5, wherein the input unit receives an input from the outside in a form of interactive programming. [8] A numerical control device according to any one of claims 1 to 7, comprising a correction unit for generating a correction signal for correcting the operation of the machine tool based on an identification result.

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