DE112019007355T5 - NUMERIC CONTROL DEVICE - Google Patents

Abstract

A numerical control device (1) according to the present invention controls the operation of a machine tool (2) which machines a workpiece with a tool, the numerical control device including: an identification operation generating unit (14) which issues an identification operation command for independently and continuously changing a spindle rotating speed and a feed rate; a data acquisition unit (16) which synchronizes a control signal for controlling the machine tool with an operation condition signal and outputs the synchronized signals as identification data, the control signal being generated based on the identification operation command, the operation condition signal indicating a corresponding operation condition of the machine tool (2); a vibration determination unit (12) that determines whether a vibration state of the machine tool (2) is stable machining, chatter vibration, or forced vibration based on the identification data; and an identification unit (13) that selects, based on a determination result of the vibration determination unit (12), 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 the identification of the selected parameter among using the identification data.

Description

area

The present invention relates to a numerical control device that controls a machine tool.

General state of the art

Machine tools are machining devices that carry out machining operations, i. H. Machining in which unneeded portions are removed from a workpiece by applying force or energy to the workpiece using a tool. In particular, cutting is a type of machining in which unnecessary portions of a workpiece are shaved off by bringing the cutting edge of a tool into contact with the workpiece at high speed to cause shear fracture on the workpiece surface.

Since cutting is a physical phenomenon in which a machining process and mechanical dynamics affect each other, it is desirable to control the machining process and mechanical dynamics at the same time in order to manage the machining state. The machining process is a series of steps in which the tool cutting edge is moved into the workpiece to form a machined surface and also to create chips in the process. Mechanical dynamics represent 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 above-described machining process and mechanical dynamics affect each other in a complicated manner, and thus an integrated analysis of cutting is considered difficult. For this reason, the production sites evaluate a limited number of objectives, achieving a machining management that serves its purpose.

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 machining is performed, it is not possible to accurately estimate the state of the machine tool during machining. It is therefore 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 at the production site to efficiently carry out improvement work, such as managing tool life, setting high-efficiency machining conditions, and changing the design of fixing devices. As a result, an improvement in productivity can be expected.

Patent Literature 1 discusses a method of performing parameter identification based on 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 the time of machining at a variety of spindle rotation speeds, and calculating the natural frequency of the tool from the peaks obtained by combining the compliance spectra of the different spindle rotation speeds be obtained. This method causes the machine tool to perform a machining operation to gradually change the spindle rotating 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 detection of displacement and force during machining.

citation list

patent literature

Patent Literature 1: Japanese Patent Application Laid-Open No. 2017-94463

abstract

Technical problem

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 changed stepwise so that various compliance spectra are obtained, to thereby calculate the natural frequency. Thus, 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. In addition, that requires in the patent lite The method described in structure 1 uses a different identification operation to identify parameters other than the natural frequency. In addition, since the spindle rotation speed is changed only in a plurality of predetermined stages in the method described in Patent Literature 1, it is time-consuming to acquire parameters corresponding to the various spindle rotation speeds.

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.

the solution of the problem

In order to solve the problems described above and achieve the object, the present invention provides 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 includes 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 speed. The numerical control device also includes: a data acquisition unit for synchronizing a control signal for controlling the machine tool with an operation condition signal and for outputting the synchronized signals as identification data, the control signal being generated based on the identification operation command, the operation condition signal indicating an operation condition of the machine tool which operates based on the control signal; and 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. The numerical control device further includes 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 performing identification of the selected parameter using the identification data.

Advantageous Effects of the Invention

The numerical control device according to the present invention can achieve the effect of identifying the characteristic machining parameters efficiently in a short time.

character list

• 1 14 is a block diagram illustrating an exemplary configuration of a numerical control device according to a first embodiment.
• 2 12 is a diagram illustrating an example pattern of an identification operation command generated by an identification operation generation unit according to the first embodiment.
• 3 12 is a diagram illustrating an example pattern of an identification operation command generated by the identification operation generation unit according to the first embodiment.
• 4 12 is a diagram illustrating an example pattern of an identification operation command generated by the identification operation generation unit according to the first embodiment.
• 5 Fig. 12 is a diagram showing 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.
• 6 14 is a diagram illustrating an example rotation angle of a tool at which the tool cutting edge is in contact with the workpiece according to the first embodiment.
• 7 14 is a diagram illustrating an example rotating angle of a tool where the tool cutting edge is not in contact with the workpiece according to the first embodiment.
• 8th 14 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.
• 9 14 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.
• 10 14 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.
• 11 14 is a flowchart illustrating an example of operation of the numerical controller according to the first embodiment.
• 12 12 is a diagram illustrating an example configuration of a processing circuit according to the first embodiment.
• 13 14 is a block diagram illustrating an example configuration of a numerical control device according to a second embodiment.
• 14 14 is a flowchart illustrating an example of operation of the numerical controller according to the second embodiment.
• 15 14 is a block diagram illustrating an example configuration of a numerical control device according to a third embodiment.
• 16 14 is a block diagram illustrating an example configuration of a numerical control device according to a fourth embodiment.

Description of the embodiments

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

1 14 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 controller 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 operation state signal indicating the operation state of the machine tool 2 from a sensor (not illustrated).

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. The machine tool 2 includes, for example, a spindle that imparts rotary motion to the tool or workpiece, and a feed shaft that is a servo shaft that imparts a position to the tool or workpiece. The spindle and the feed shaft each contain a motor.

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. The sensors provided in the machine tool 2 include a sensor capable of detecting vibrations of at least one of the tool and the workpiece. The sensor capable of detecting the vibration of at least one of the tool and the workpiece is, for example, a linear encoder and a current sensor built in 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 are an acceleration sensor, a position sensor, a force sensor, or a microphone. The sensors provided in the machine tool 2 are described below as a linear encoder, a current sensor, and a force sensor, for example. For example, the force sensor is installed 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 between the tool and the workpiece can be detected.

As in 1 As illustrated, 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.

The identification operation generation unit 14 generates an identification operation command for independently and continuously changing the spindle rotating speed and the feed speed of the machine tool 2 and outputs the identification operation command to the drive control unit 15 . The spindle rotation speed, which is the rotational speed of the spindle, indicates the number of times the spindle rotates per unit time turns. 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, to enable the identification unit 13 to acquire identification data, that is, data which the identification unit 13 performs identification processing (described later ) used. The identification operation command, which is a command generated for the identification operation, includes a spindle rotating speed command and a feed speed command.

the 2 until 4 12 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. the 2 until 4 12 represent command patterns in which the spindle rotating speed and the feed speed continuously change between the identification operation start time t1 and the identification operation end time t2. In the 2 until 4 the horizontal axis represents time (points in time), the upper vertical axis represents spindle rotation speed, and the lower vertical axis represents feedrate. Spindle rotation speed and feedrate are hereinafter referred to as S and F, respectively.

S0 is a reference spindle speed, ie, the spindle speed before the identification operation, and S1 is the maximum value of the spindle speed during the identification operation. T1 is a time constant in which the spindle rotation speed increases from S0 to S1. T2 is a time constant in which the feedrate increases from F0 to F1. 2 represents a command pattern in which the spindle rotation speed and the feedrate are accelerated and decelerated separately. in the in 2 In the example illustrated, the spindle rotation speed increases to S1 in the time constant T1, after which the spindle rotation speed decreases. After reducing to S0, the spindle rotation speed remains at S0. Once the spindle rotation speed has decreased to S0, the feedrate increases to F1 with the time constant T2. When F1 is reached, the feed rate then decreases.

3 Figure 12 illustrates a command pattern in which, after an increase in spindle rotation speed, the feedrate increases and then decreases, and then the spindle rotation speed decreases. 4 Fig. 12 illustrates a command pattern in which the spindle rotation speed increases and then decreases, with the feed rate repeatedly increasing and decreasing as the spindle rotation speed changes.

Although the 2 until 4 Showing examples where the spindle rotating speed changes between S0 and S1, where S1 is defined as the maximum value of the spindle rotating speed during the identification operation, the identification operation generating unit 14 can set the minimum value S2 of the spindle rotating speed during the identifying operation and generate a command pattern in which the spindle rotating speed changes varies within the range from S0 to S2. The same applies to the feedrate, and the minimum value F2 of the feedrate during the identification operation can be set, and a command pattern in which the feedrate changes between F0 and F2 can be generated.

Although the 2 until 4 Illustrating the triangular command patterns of increase and decrease, the identification operation generating unit 14 can generate an arbitrary command pattern in which the spindle rotating speed and the feed speed continuously increase and decrease. For example, the identification operation generating unit 14 may generate a sinusoidal or S-curve command pattern for the change instead of the triangular command pattern.

The identification operation generation unit 14 can generate an identification operation including various combinations of the spindle rotation speed and the feedrate by changing the spindle rotation speed and the feedrate independently of each other in the manner described above.

It is known that the magnitude of the cutting force generated when the tool cuts the workpiece mainly depends on the feed amount per edge, and the vibration period of the cutting force mainly depends on the spindle rotating speed. For this reason, the spindle rotating speed and the feed speed are generally changed at the same ratio. 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 generating unit 14 changes the spindle rotating speed and the feed speed independently, the magnitude and amplitude of the cutting force can be different Changes and various types of vibrations of the machine tool 2 can be generated during the identification operation, as will be described later.

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 the feed shaft of the machine tool 2 are operated as specified by the identification operation command. The control signal is a command for the spindle and the 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 the 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 rotational speed and a reference feedrate for the machining path when no identification operation command is input from the identification operation generation unit 14, that is, during the normal machining operation. In addition, 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 .

In the drive control unit 15, a machining path and the reference spindle rotating speed and a reference feed rate for the machining path are set in advance. A machining path and a reference spindle rotational speed and a reference feed rate for the machining path can be given by a numerical control program. Even if an identification operation command is inputted 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 rotating speed and the feed speed according to the identification operation command. Each shaft of the machine tool 2 includes a motor and a motor controller, and each motor controller controls the motor based on a control signal received from the drive control unit 15 and a feedback signal about, for example, 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 result of detection by the current sensor. Feedback signals about the position, the speed and the motor current are also referred to below as position feedback signals, speed feedback signals and current feedback signals, respectively.

The data acquisition unit 16 synchronizes a control signal output from the drive control unit 15 with an operational state signal indicating the operational state of the machine tool 2 operated based on the control signal, and outputs the thus synchronized signals as identification data. In particular, the data acquisition unit 16 synchronizes the data contained in these signals in time using the control signal output by the drive control unit 15 and the operating state signal output by the sensors of the machine tool 2 and outputs the data thus synchronized as synchronization data to the vibration determination unit 12 and the identification unit 13. As described above, the operational state signal is a signal indicative of the operational 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, as discussed above, the data acquisition unit 16 can use, as the operating condition signal, feedback signals about the position and speed of the spindle and feed shaft, a feedback signal about the current and force, or the Record torque as detected by the force sensor. The actual readings of force or torque as detected by the force sensor are also referred to hereinafter as force information. Since the operation status signal is generated after the machine tool receives the control signal, the operation status 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 time deviation between the operating status signal and the control signal by shifting the data contained in the operating status signal or the data contained in the control signal by the time that corresponds to the difference in, for example, the communication time. The data acquisition unit 16 collects the data with the accumulated time deviation, i. H. the synchronized data into identification data, and outputs the identification data to the vibration determination unit 12 and the identification unit 13 .

The vibration determination unit 12 determines whether vibration has occurred in the machine tool 2 using the identification data. When 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” means a vibration that has a larger amplitude than the vibration component derived from the cutting force due to the tool and the workpiece, and the vibration determination unit 12 determines whether the vibration of that importance has occurred.

The determination of the occurrence of vibrations 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 range. The type of signal used for the vibration determination is not limited to the force information, and for example, the vibration determination unit 12 may determine whether vibration has occurred using a current feedback signal included in the operating condition 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 .

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

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 vibration occurring is forced vibration or 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 fundamental cutting frequency. That is, the vibration determination unit 12 determines that the vibration is forced vibration when the vibration frequency is an integral multiple of the fundamental cutting frequency, and determines that the vibration is chatter vibration when the frequency is a non-integer multiple of the fundamental cutting frequency.

Note that the vibration determination unit 12 determines that the state is stable machining after determining that vibration has not occurred. The stable machining is a machining state in which only the vibration component derived from the cutting force of the tool and the workpiece occurs without vibration excitation around the natural frequency of the structure.

The vibration determination unit 12 constantly performs the above processing to determine whether the identification data associated with each point in time 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 whether the vibration state of the machine tool 2 is stable machining, forced vibration, or chatter vibration based on the identification data.

Based on the result of determination by the vibration determination unit 12 , the identification unit 13 selects an identifiable characteristic machining parameter as a selected one of characteristic machining parameters and identifies the selected parameter using the identification data inputted from the data acquisition unit 16 . Furthermore, based on the determination result of the vibration determination unit 12, the identification unit 13 selects an identifiable characteristic dynamics parameter as a selected one of characteristic dynamics parameters. Selected parameters are listed below gend also referred to as identifiable parameters. The identification unit 13 outputs the result of the identification processing to the correction unit 11 . The identification processing is performed using identification data and information about the processing conditions. Machining condition information, which is information indicating machining conditions in the identification operation, is preset in the identification unit 13 . The information about the machining conditions includes, for example, a tool diameter, the number of tool cutting edges, a tool helix angle, an axial cutting amount of the tool, a radial cutting amount of the tool, and a machining mode representing up-cutting or down-cutting.

It should be noted that in the following description, an example is given in which the identification unit 13 identifies both characteristic dynamics parameters and characteristic machining parameters, but the identification unit 13 can identify either characteristic dynamics parameters or characteristic machining parameters. For example, based on the result of the determination by the vibration determination unit 12, the identification unit 13 selects an identifiable characteristic machining parameter as a selected one of the characteristic machining parameters and identifies the selected parameter using the identification data.

In general, the spindle rotation speed and feedrate are specified as constant values during machining. In this case, the identification unit 13 can acquire only identification data for machining with a single set of spindle rotation speed and feedrate. Since the identification data includes a movement state signal detected by the sensors of the machine tool 2 as described above, the identification unit 13 can only acquire a movement state signal for machining with a single set of spindle rotation speed and feed speed. According to the present embodiment, the identification operation generation unit 14 generates commands that allow each of the spindle rotation speed and the feed speed to be continuously changed, so that the identification unit 13 can obtain moving state signals for machining with different combinations of spindle rotation speed and feed speed at different timings.

Characteristic dynamics parameters and characteristic processing parameters will now be described. Characteristic dynamics parameters, which are parameters representing the characteristics of a dynamics model (described later), represent the vibration characteristics of the machine tool 2. Characteristic dynamics parameters are, 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 are, for example, a specific cutting resistance, an edge force, a tool eccentricity and a tool removal width.

wobei
f_c: Schneidkraft, f_d: Störkraft, m_t: äquivalente Masse, x: relative Verschiebung des Werkstückendes in Vibrationsrichtung in Bezug auf den Tisch $${\text{c}}_{\text{t}}=2{\text{m}}_{\text{t}}\mathrm{\zeta }{\mathrm{\omega }}_{\text{n}},{\text{k}}_{\text{t}}={\text{m}}_{\text{t}}{\mathrm{\omega }}_{\text{n}}^2,$$

ζ: Dämpfungskoeffizient t, ω_n: EigenfrequenzA dynamic model is a mathematical model that describes the dynamics of the mechanical structures within the machine tool 2, the tool and the workpiece. An example of a dynamics model is described below. 5 Fig. 12 is a diagram showing 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. 5 12 illustrates an example in which the machine tool 2 performs milling by rotating a tool 33 . This in 5 The illustrated example is based on the assumption that a workpiece 32 is placed on a table 31, a drive shaft and a tooling system 34 are provided, which provide a spindle that holds the tool 33. In 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 among the cutting force 36, the disturbing force 37 and the relative displacement 35 can be expressed by the formula (1) below. The dynamics model represented by the formula (1) is a mathematical model for calculating: the disturbance force 37 transmitted to the feed shaft through the mechanical structure including the tool 33 or the workpiece 32 when the cutting force 36 is generated; and the positional deviation occurring at each feed shaft by the mechanical structure when the cutting force 36 is generated.
[Formula 1] $$\begin{array}{l}{\text{f}}_{\text{c}}={\text{m}}_{\text{t}}\ddot{\text{x}}+{\text{c}}_{\text{t}}\dot{\text{x}}+{\text{k}}_{\text{t}}\text{x}\\ {\text{f}}_{\text{i.e}}={\text{c}}_{\text{t}}\dot{\text{x}}+{\text{k}}_{\text{t}}\text{x}\end{array}\}$$

whereby
f _c : cutting force, f _d : disturbing force, m _t : equivalent mass, x: relative displacement of the workpiece end in the vibration direction with respect to the table $${\text{c}}_{\text{t}}=2{\text{m}}_{\text{t}}\mathrm{\zeta }{\mathrm{\omega }}_{\text{n}},{\text{k}}_{\text{t}}={\text{m}}_{\text{t}}{\mathrm{\omega }}_{\text{n}}^2,$$

ζ: damping coefficient t, ω _n : natural frequency

The dynamics model represented by formula (1), which is a model with the workpiece 32 on the table 31 and is described as a single degree of freedom vibration system, is a non-limiting example of a dynamics model. For example, the dynamics model may provide a multi-degree-of-freedom vibration system described as including the table 31 and a fixture that fixes the workpiece 32 . In addition, a dynamic model can be defined with regard to a tool-side structure that contains the tool 33, the tool system 34 and the spindle motor. Furthermore, a dynamics model can be set as a vibration system provided by a combination of a tool-side structure and a work-side structure including a fixation that fixes the work 32 and the table 31 .

f_c: Schneidkraft, K^c: spezifische Schneidkraft,
K^ce: Kantenkraft, a: Axialschneidbetrag des Werkzeugs
h: Werkstückschneiddicke
φ: Drehwinkel des Werkzeugs, t: Zeit $$\text{g}\left(\mathrm{\phi }\left(\text{t}\right)\right)=\{\begin{array}{l}1\left({\mathrm{\phi }}_{\text{s}}\le \mathrm{\phi }\left(\text{t}\right)\le {\mathrm{\phi }}_{\text{f}}\right)\hfill \\ 0\left(\mathrm{\phi }\left(\text{t}\right)\le {\mathrm{\phi }}_{\text{s}},{\mathrm{\phi }}_{\text{f}}\le \mathrm{\phi }\left(\text{t}\right)\right)\hfill \end{array}$$

φ_s: Werkzeugeingriffswinkel, φ_f: WerkzeugfreigabewinkelA 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 Formula (2) below.
[Formula 2] $${\text{f}}_{\text{c}}=\left({\text{K}}^{\text{c}}\text{Ah}\left(\mathrm{\phi }\left(\text{t}\right)\right)+{\text{K}}^{\text{c.e}}\right)\text{G}\left(\mathrm{\phi }\left(\text{t}\right)\right)$$

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 $$\text{G}\left(\mathrm{\phi }\left(\text{t}\right)\right)=\{\begin{array}{l}1\left({\mathrm{\phi }}_{\text{s}}\le \mathrm{\phi }\left(\text{t}\right)\le {\mathrm{\phi }}_{\text{f}}\right)\hfill \\ 0\left(\mathrm{\phi }\left(\text{t}\right)\le {\mathrm{\phi }}_{\text{s}},{\mathrm{\phi }}_{\text{f}}\le \mathrm{\phi }\left(\text{t}\right)\right)\hfill \end{array}$$

φ _s : tool pressure angle, φ _f : tool release angle

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 angle of rotation of the tool 33 at each time. Cutting thickness refers to the thickness by which a tool cutting edge, which is a cutting edge of tool 33 , cuts workpiece 32 as it passes through workpiece 32 . A cutting force is calculated as a value greater than or equal to zero when the tool cutting edge is at an angle such that the tool cutting edge is in contact with the workpiece 32, as in FIGS 6 and 7 illustrated. However, the cutting force is calculated as zero when the tool cutting edge is at an angle such that the tool cutting edge is not in contact with the workpiece 32 . 6 14 is a diagram illustrating an example rotation angle of the tool 33 at which the tool cutting edge is in contact with the workpiece 32 according to the first embodiment. 7 12 is a diagram illustrating an example rotation angle of the tool 33 where the tool cutting edge is not in contact with the workpiece 32. FIG. 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 point. When the tool cutting edge touches the workpiece 32, the cutting thickness is calculated. If the tool cutting edge does not touch the workpiece 32, the cutting thickness is calculated as zero.

f_cx: X-Achsenschneidkraft, f_cy: Y-Achsenschneidkraft, f_cz:
Z-Achsenschneidkraft, fct: Werkzeugtangentialschneidkraft,
f_cr: Werkzeugradialschneidkraft, fca: WerkzeugaxialschneidkraftThe calculation represented by formula (2) is performed for the three directions, the tangential direction, the radial direction and the axial direction of the tool, thereby providing the cutting force in the three directions. In the machining process model, by 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, the cutting force is calculated in the tool reference coordinate system. An example of a coordinate transformation is expressed by formula (3).
[Formula 3] $$\left[\begin{array}{c}{\text{f}}_{\text{cx}}\\ {\text{f}}_{\text{cy}}\\ {\text{f}}_{\text{cz}}\end{array}\right]=\left[\begin{array}{ccc}\text{cos}\mathrm{\phi }\left(\text{t}\right)& \text{sin}\mathrm{\phi }\left(\text{t}\right)& 0\\ -\text{sin}\mathrm{\phi }\left(\text{t}\right)& \text{cos}\mathrm{\phi }\left(\text{t}\right)& 0\\ 0& 0& 1\end{array}\right]\left[\begin{array}{c}{\text{f}}_{\text{ct}}\\ {\text{f}}_{\text{cr}}\\ {\text{f}}_{\text{approx}}\end{array}\right]$$

f _cx : X-axis cutting force, f _cy : Y-axis cutting force, f _cz :
Z axis cutting force, fct: tool tangential cutting force,
f _cr : tool radial cutting force, fca: tool axial cutting force

C: Vorschubbetrag pro KanteThe calculations represented by the formulas (2) and (3) are performed according to the number of tool cutting edges, the calculation results are added and yield so the resulting value representing 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 for 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 from Formula (4) using the tool rotation angle and the feed amount per edge.
[Formula 4] $$\text{H}\left(\mathrm{\phi }\left(\text{t}\right)\right)=\text{c sin}\mathrm{\phi }\left(\text{t}\right)$$

C: Feed amount per edge

v: Verschiebungsbetrag der Werkzeugmitte in der Werkzeugradialrichtung,
w: Verschiebungsbetrag der vorher bearbeiteten Oberfläche in der Werkzeugradialrichtung,
Δr: Korrekturbetrag, der jeder Werkzeugschneidkante entspricht,
N_tooth: Nummer der WerkzeugschneidkanteAs another example, a cutting thickness can also be calculated using formula (5).
[Formula 5] $$\text{H}\left(\mathrm{\phi }\left(\text{t}\right)\right)=\text{c sin}\mathrm{\phi }\left(\text{t}\right)+\left\{\text{v}\left(\mathrm{\phi },\text{t}\right)-\text{w}\left(\mathrm{\phi },\text{t}\right)\right\}+\mathrm{\Delta }\text{right}\left(\mathrm{\phi },\text{t},{\text{N}}_{\text{tooth}}\right)$$

v: shift amount of the tool center in the tool radial direction,
w: shift amount of the previously machined surface in the tool radial direction,
Δr: correction amount corresponding to each tool cutting edge,
N _tooth : Tool cutting edge number

Formula (5) is a formula for calculating the cutting thickness. Formula (5) is Formula (4) to which a variation amount and a correction amount are added. The amount of variation is calculated using the difference between the current tool offset and the previously machined surface, i.e. H. the machined surface provided by the previous tool cutting edge, i.e. one edge before. The correction amount corresponds to the respective tool cutting edge. Among the shift amount of the current tool cutting edge and the shift amount of the one or more tool cutting edges that are one or more cutting edges before is a shift amount that affects the shape of the machined surfaces. The calculation represented by Formula (5) modifies the cutting thickness with the difference between the shift amount of the current tool cutting edge and the shift amount affecting the shape of the machined surface. That is, under the one or more tool cutting edges that are one or more edges before 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 actual tool cutting edge involved in the cutting operation and the trajectory of the tool cutting edge affecting the shape of the machined surface.

The relative displacement x of the 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. Moreover, 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 before. It should be noted that “the one or more tool cutting edges that are one or more edges before” are the tool cutting edges that are involved in cutting operations at times before the time when the reference tool cutting edge is involved in cutting. For example, assume that the tool has two edges and the tool cutting edge that is performing a cutting operation is a second cutting edge. A "tool cutting edge that is one edge ahead" is a first edge that is 180 degrees behind the second edge. A "tool cutting edge that is second edges before" is a second edge that is 360 degrees behind the second edge. A "tool cutting edge that is 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 displacement 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, which is one edge before, but also the previously machined Surface created by the tool cutting edge that is two or more edges before.

The calculation represented by Formula (5) further modifies the cutting thickness with a correction amount corresponding to the tool rotation angle and a tool edge number, ie, a number indicating the tool edge. In formula (5), the correction amount for modifying a variation in cutting thickness, the variation occurring due to cutting operations with different turning radii for different tool cutting edges, is introduced. The correction amounts must be introduced in formula (5) in the situations discussed below. When For example, when chipping or peeling or the like occurs at a specific cutting edge, the radius of rotation of that tool cutting edge is shorter than that of another tool cutting edge. In such a case, a correction amount corresponding to the cut width, the exfoliation width, or the like should be added. Alternatively, a tool with replaceable cutting edges involves an error in attachment of a tool cutting edge, in which case an amount of correction corresponding to this attachment error should be added. Alternatively, the fulcrum of the spindle does not coincide with the center of the tool, that is, there is tool eccentricity, in which case the correction amount corresponding to a tool eccentricity amount should be added. Note that the tool center is the center of the tool's perimeter.

The tool eccentricity amount is an amount by which the radius of rotation 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 fulcrum of the spindle, as in FIGS 8th and 9 illustrated. 8th 14 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. 9 14 is a diagram illustrating cutting with a second cutting edge when there is an amount of deviation between the center of the tool center and the fulcrum of the spindle. The first cutting edge 43 and the second cutting edge 44 are the cutting edges of the tool. In the examples given in the 8th and 9 4, there is a deviation between a center 41 of the tool and a pivot point 42 of the spindle. In such a case, it is necessary to modify the cutting thickness if there is no deviation, and the tool eccentricity amount indicates a modification amount by which to modify this cutting thickness. That is, the amount of tool eccentricity, which depends on the rotation angle of the tool 33, is added to or subtracted from the cutting thickness. The above cases where the cutting thickness is modified with a modification amount are non-limiting examples, and the modification amount can be changed appropriately according to a phenomenon occurring at the tool cutting edge.

Note 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 specific cutting force in different cases where: the cutting speed is greater than or equal to a threshold; and the cutting speed is less than the threshold. In addition, a process damping force can be added to the right side of formula (2). The process damping force is the force created by the contact of the flank of the tool cutting edge with the workpiece. For example, the process loss can be expressed as a value obtained by multiplying the flank contact area by a process loss coefficient. In this case, the process damping coefficient serves as one of the characteristic machining parameters.

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

A processing that uses Formula (1) and Formula (2) as a dynamics model and a machining process model, respectively, determines identifiable parameters from a vibration determination result, and identifies these parameters will be described below. 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 amount of tool eccentricity are characteristic machining parameters.

Upon 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 occurs and identification is performed.

[Case where the determination result is stable machining]

The identification unit 13 selects a specific cutting force and an edge force as identifiable parameters, the forces being characteristic machining parameters. In addition, 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 the formulas (2) to (4) using the force information output from the force sensor and the machining conditions recorded in the identification unit 13 in advance. That is, the specific cutting force and the edge force are calculated in Formula (2) so that the value of the force in each axial direction calculated from Formula (3) with Formulas (2) and (4) inserted therein is im Essentially corresponds to the actual measured value of the force detected by the force sensor. Any known optimization method or numerical simulation can be used for the calculation of the specific cutting force and the edge force. For example, a least squares method or a gradient method can be used.

[Case where the determination result is forced vibration]

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. In addition, the identification unit 13 identifies the damping coefficient, the natural frequency, the specific cutting force, and the edge force through the following processing.

The identification unit 13 identifies the damping coefficient, natural frequency, specific cutting resistance, and edge force according to the formulas (1) to (4) using the force information output from the force sensor and the machining conditions recorded in the identification unit 13 in advance. Specifically, the actual measured value of the force detected by the force sensor in f _{d is} substituted into Formula (6) below, where Formula (6) is a modified Formula (1).
[Formula 6] $${\ddot{\text{f}}}_{\text{i.e}}=2\mathrm{\zeta }{\mathrm{\omega }}_{\text{n}}\left({\dot{\text{f}}}_{\text{c}}-{\dot{\text{f}}}_{\text{i.e}}\right)+{\mathrm{\omega }}_{\text{n}}^2\left({\text{f}}_{\text{c}}-{\text{f}}_{\text{i.e}}\right)$$

In addition, the value of the force in each axial direction calculated from Formula (3) with Formulas (2) and (4) substituted therein is substituted into f _c of Formula (6). At this time, there is 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 the 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 the 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 the formula (6) is minimized. Alternatively, the damping coefficient, natural frequency, specific cutting force, and edge force can be calculated using a least squares method.

[Case where the determination result is chatter vibration]

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 amount of tool eccentricity are characteristic machining parameters. In addition, the identification unit 13 identifies the equivalent mass, damping coefficient, natural frequency, specific cutting resistance, edge force, and tool eccentricity amount through the following processing.

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

10 14 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 a chatter vibration. First, in step S1, the identification unit 13 defines initial values for a set of parameters. This set of parameters is made up of a combination of characteristic dynamic parameters and a combination of characteristic processing parameters. The dynamics characteristic parameters are an equivalent mass, a damping coefficient, and a natural frequency, and the machining characteristic parameters are a specific cutting force, an edge force, and a tool eccentricity amount.

In step S2, the identification unit 13 calculates shift amounts that satisfy the dynamics model and the machining process model at the same time. For example, the identification unit 13 calculates a shift amount that satisfies the formula (1) that is the dynamic model and the formulas (2) and (5) that are the machining process models at the same time. The shift amounts are the relative shift x of formula (1) and v and w of formula (5).

In step S3, the identification unit 13 calculates the disturbance force with the dynamic model considering the displacement amount. For example, the identification unit 13 calculates the disturbance force f _d by substituting the shift amount calculated in step S2 into the formula (1) which is the dynamic model.

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 value of the force 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 regards the values of the set of parameters at that time as an identification result and ends the identification processing. If the error exceeds the allowable value (No in step S4), the identification unit 13 updates the values of the set of parameters in step S5 and returns to step S2.

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

Referring again to 1 the correction unit 11 receives the dynamics characteristic parameters and the machining characteristic 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 is performed on the mechanical dynamics and the machining process, and a combination of a spindle rotating speed and a feed speed 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 the feedrate based on the calculated spindle rotation speed and feedrate, 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 satisfies a given dimensional intersection. Note that the targets to be corrected may include the cutting amount in the tool axial direction or the tool radial direction in addition to the spindle rotating speed and the feed speed.

An example of the operation of the numerical control device 1 according to the first embodiment described above is explained with reference to FIG 11 described. 11 14 is a flowchart illustrating an example of operation of the numerical controller 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 performs the operation specified by the identification operation.

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 a operating condition signal from the sensors of the machine tool 2, generates identification data in which the time deviation between the two signals is compensated, and outputs the identification data to the vibration determination unit 12 and the identification unit 13.

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 movement state signal of the identification data, and when determining that vibration has not occurred, determines that the vibration state is stable machining. When 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 on the vibration state to the identification unit 13 as a vibration determination result.

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 dynamics characteristic parameters and the machining characteristic parameter according to the vibration determination result.

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 controller 1 corrects the operation of the machine tool 2 based on the identification result in step S16. 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 rotational speed and the reference feedrate for the machining path, and the correction signal, and outputs the control signal to the machine tool 2 .

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. In addition, after the identification operation, step S16 is performed so that the processing state can be improved using the identification result.

Next, a hardware configuration of the numerical control device 1 will be described. Each unit of the 1 The illustrated numerical controller 1 is implemented by a processing circuit. The processing circuitry may be circuitry that includes a processor or dedicated hardware.

In a case where the processing circuit is a circuit including a processor, the processing circuit is, for example, a processing circuit of FIG 12 illustrated configuration. 12 12 is a diagram illustrating an example 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 represented by the FIG 12 Illustrated processing circuit 200 is implemented, the processor 201 reads and executes a program stored in the memory 202, thereby converting them. That is, in a case where each unit of the numerical control device 1 is represented by the in 12 Illustrated processing circuit 200 is implemented, these functions are implemented using a program that is software. The memory 202 is also used as a work area of the processor 201 . The processor 201 is a central processing unit (CPU) or the like. The memory 202 is, for example, non-volatile or volatile semiconductor memory such as random access memory (AM), read-only memory (ROM), or flash memory, magnetic disk, or the like.

In a case where the processing circuit that implements each unit of the numerical controller 1 is dedicated hardware, the processing circuit is, for example, a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). It is noted that each unit of the numerical controller 1 may be implemented by a combination of a processing circuit including a processor and dedicated hardware. Each unit of the numerical controller 1 can be implemented by a variety of processing circuits.

As described above, the numerical controller 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, 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 identification data collected through the identification operation, and identifies identifiable machining characteristic 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. In addition, the numerical control device 1 according to the first embodiment can also identify identifiable dynamic characteristic parameters according to the determination result on the vibration state. Moreover, 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. In addition, 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, so that machining can be continued without causing machining defects. If the identification is performed by changing the spindle rotation speed step by step, peak values that are candidates for the natural frequency can be searched only discretely. On the other hand, the present embodiment generates a command for continuously changing the rotational speeds of the spindle and the feed shaft as described above, thereby making it possible to identify characteristic dynamic parameters and machining characteristic parameters with higher accuracy than when the spindle rotational speed is changed stepwise.

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

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 rotating 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 simultaneously issued to these machine tools. In this case, the effect of completing the identification can be obtained in a shorter time than when a single machine tool is operated. 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.

Fest: Störkraft der Servoachse, K_T: Drehmomentkoeffizient, Iref: Referenzmotorstrom, M: äquivalente Masse der Vorschubachse,
u: Detektionsposition des LinearcodierersAlthough the present first embodiment describes the configuration in which the force is directly detected by the force sensor, the force can be indirectly estimated using another sensor, and also in this case, effects similar to those of the first embodiment can be obtained. For example, using a reference motor current, that is, a motor current command, and a position detected by the linear encoder, the data acquisition unit 16 or the identification unit 13 can calculate the force from the formula (7) below.
[Formula 7] $${\text{f}}_{\text{est}}={\text{K}}_{\text{T}}{\text{I}}_{\text{ref}}-\text{M}\ddot{\text{and}}$$

Fixed: servo axis disturbance force, K _T : torque coefficient, Iref: reference motor current, M: feed axis equivalent mass,
u: detection position of the linear encoder

α: Detektionsbetrag des Beschleunigungssensors
Die Formeln (7) und (8) sind
Kraftberechnungsformeln, in denen die Vorschubwelle als eine Masse mit einzelner Trägheit betrachtet wird, aber eine Berechnungsformel, in der die Vorschubwelle als eine Masse mit mehreren Trägheiten betrachtet wird, kann gemäß der Struktur der Vorschubwelle entsprechend verwendet werden. Außerdem kann ein Term zur Kompensation der Reibungskraft hinzugefügt werden.Alternatively, an accelerometer can be used to calculate the force in a similar manner. In this case the datar detection unit 16 or the identification unit 13, using an acceleration detected by the acceleration sensor, calculate the force using the following formula (8).
[Formula 8] $${\text{f}}_{\text{est}}={\text{K}}_{\text{T}}{\text{I}}_{\text{ref}}-\text{M}\mathrm{a}$$

α: Amount of detection of the acceleration sensor
The formulas (7) and (8) are
Force calculation formulas in which the feed shaft is regarded as a single-inertia mass, but a calculation formula in which the feed shaft is regarded as a multi-inertia mass can be used appropriately according to the structure of the feed shaft. A term to compensate for the frictional force can also be added.

Second embodiment

13 14 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 has been described in which the identification processing is performed based on the control signal and the operation status signal obtained during a single execution of the identification operation. In the first embodiment, if chatter vibration does not occur during a single identifying operation, some of the dynamics characteristic parameters and the machining characteristic parameters cannot be identified. The present second embodiment describes an example in which the identification operation is modified when chattering vibration does not occur during execution of the identification operation. Components that have the same functions as those of the first embodiment are hereinafter denoted by the same reference numerals, and redundant descriptions are omitted. The following description mainly focuses on how the second embodiment differs from the first embodiment.

As in 13 1, 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.

As with the identification unit 13 according to the first embodiment, the identification unit 13a selects identifiable parameters from the dynamics characteristic parameters and the machining characteristic parameters using the vibration determination result inputted from the vibration determination unit 12 . Furthermore, like the identification unit 13 according to the first embodiment, the identification unit 13a performs identification processing for identifying the selected identifiable parameters based on the identification data inputted from the data acquisition unit 16 and outputs the result of the identification processing to the correcting unit 11. The identification processing is performed using the identification data and the information on the processing conditions in the same manner as performed by the identification unit 13 according to the first embodiment.

At least one of the dynamics characteristic parameter and the machining characteristic parameter is preset as an identification target parameter in the identification unit 13a. When 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 dynamics parameter or a characteristic machining parameter is present.

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 rotating speed and the feed speed of the machine tool and outputs the identification operation command to the drive control unit 15 .

Moreover, the identification operation generating unit 14a modifies the identification operation command pattern 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 types of parameters when chatter vibration occurs in the machine tool. Therefore, the identification operation generation unit 14a changes the change range of the spindle rotation speed or the feed speed to modify the identification operation so that during the identification chattering vibration occurs during operation. Specifically, the identification operation generating unit 14a generates an identification operation command pattern in which at least one of the maximum value S1 and minimum value S2 of the spindle rotating speed and the maximum value F1 and the minimum value F2 of the feed speed described above is changed at a predetermined ratio. For example, in particular, at least one of the maximum value S1 and the minimum value S2 of the spindle rotating speed and the maximum value F1 and the minimum value F2 of the feed speed is changed so that at least one of the spindle rotating speed and the feed speed is changed in a range different from that in the range specified in the previous identification mode.

An example of the operation of the numerical control device 1a according to the second embodiment described above is explained with reference to FIG 14 described. 14 14 is a flowchart illustrating an example of operation of the numerical controller 1a according to the second embodiment. In step S21, the numerical control device 1a starts an identification operation. In the initial execution of step S21, the identification operation generation unit 14a generates an identification operation initial 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.

In steps S22 to S25, similar processes to steps S12 to S15 in Fig 11 , which are described in the first embodiment, are performed. In step S26, the identification unit 13a determines whether the predetermined identification target parameters have been identified, and when the identification is completed (Yes in step S26), the operation of the numerical controller 1a proceeds to step S28. When one or more of the predetermined identification target parameters has not been identified (No in step S26), the numerical controller 1a modifies the identification operation command in step S27 and repeats the series of processes from step S21. Specifically, in step S27, the identification unit 13a 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 shaft rotating speed and the feed speed, and outputs the modified identification operation command to the drive control unit 15. In the second and subsequent executions of step S<b>21 , 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 .

In step S28, the numerical controller 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 rotational speed and the reference feedrate for the machining path, and the correction signal, and outputs the control signal to the machine tool 2 .

The numerical controller 1a repeatedly executes the series of processes from step S21 to step S27 during machining. That is, when one or more of the identification target parameters, namely, the parameters set as targets to be identified, remain unidentified after identification has been performed using the identification data for the period corresponding to the identification operation command, the identification unit 13a generates an identification operation modification signal , which indicates an instruction for changing the identification mode, and outputs the identification mode modification signal to the identification mode generation unit 14a. Then, the identification operation generating 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 changed identification operation command with the operation state signal indicating the operation state of the machine tool 2 operated based on the control signal. The data acquisition unit 16 then outputs the signals thus synchronized as identification data to the vibration determination unit 12 and the identification unit 13a. These operations are repeated thereafter until identification of all parameters set as targets to be identified is completed. As a result, all the characteristic dynamics parameters and characteristic machining parameters set as the targets to be identified can be identified. In addition, the processing of step S28 using the identification result can improve the processing state. It should be noted that the above described The same procedure applies to modifying the identification operation command after completion of an identification operation. Alternatively, a procedure for modifying the identification operation can be used in the middle of the identification operation.

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. The numerical control device 1a according to the second embodiment can therefore 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 identification target parameters specified in advance can be identified.

Third embodiment

15 14 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 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 can be set from the outside. Components that have the same functions as those of the second embodiment are hereinafter denoted by the same reference numerals, and redundant descriptions are omitted. The following description mainly focuses on how the third embodiment differs from the second embodiment.

As in 15 1, the numerical control device 1b according to the third embodiment includes an input unit 17 in addition to the components of the numerical control device 1a according to the second embodiment. 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 dynamics characteristic parameter and the machining characteristic parameter 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 an 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 input to the input unit 17 interactively by an operator. In addition, the input unit 17 can receive an 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 from the outside, for example, in the following possible two cases. The first case is that "someone wishes to exclude from identification a parameter that has already been identified by some other means or the like". The second case is that "someone wants to reduce the time required for identification by identifying only high priority identification targets". Regarding the first case, the identified parameters have, for example, values obtained through 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, an identification target parameter can be selected with a check box, for example, and a display window displays the expected identification time, which changes each time a check box is activated. The provision of the check box and display window allows the operator to select as many parameters as possible to the extent that the identification time for those selected parameters is within the allowable identification time. The form of the interactive programming is not limited to these examples, and any method can be used. Displaying the information that the operator considers when selecting the parameters, as discussed above, allows the operator to easily select the identification target parameters.

The identification unit 13a uses the identification target parameters inputted 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. It should be noted that the identification unit 13a may be able to operate using both preset identification target parameters as well as 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 correcting unit 11 is as follows. Numerical control programs generally describe information such as machining paths, spindle speeds, feedrates, 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, when 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 time the tool number is changed or until the time , on which a machining path is being machined with another specified identification mode. 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.

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 remains unidentified, and performs the identification operation again. Therefore, effects similar to those of the second embodiment can be obtained, and the identification target parameters can be changed according to the operator's desire or the like.

Fourth embodiment

16 14 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 from the outside has been described. The present fourth embodiment describes a configuration in which a command pattern for the identification operation can also be set by an input from the outside. Components that have the same functions as those of the third embodiment are hereinafter denoted by the same reference numerals, and redundant descriptions are omitted. The following description mainly focuses on how the fourth embodiment differs from the third embodiment.

As in 16 1, 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.

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 outputs the received identification target parameter to the identification unit 13a. In addition, the input unit 17a is capable of receiving an input of command pattern information for designating 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 showing the spindle rotation speeds S0 and S1, the feed speeds F0 and F1, and the time constants T1 and T2 in the 2 until 4 represent. That is, the command pattern information is information indicating the waveforms of the spindle rotation speed and the feedrate relative to the time when the spindle rotation speed and the feedrate are changed by the identification operation command. The command pattern information is entered into the input unit 17a, for example, as a numerical control program or interactively. Alternatively, the command pattern information can be entered in the form of interactive programming. The command pattern information can additionally in the 2 until 4 illustrated waveforms or information specifying waveforms, so that the waveforms can also be specified from the outside.

Similar to the input unit 17, the input unit 17a may be a communication circuit connected to 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. communicates. In a case where the input unit 17a receives an input from an operator also uses a display means such as a display or a monitor as the input unit 17a. An identification target parameter and command pattern information can be input to the input unit 17a from an external device in the form of a numerical control program, or they can be input to the input unit 17a interactively by an operator. In addition, 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 set 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.

The input unit 17 a receives command pattern information for identification, and the identification operation generation unit 14 b generates an identification operation command pattern based on the received identification operation command pattern information and outputs the identification operation command to the drive control unit 15 . Moreover, 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.

As described above, the numerical control device 1c according to the fourth embodiment enables a command pattern for the identification operation to be set by an input from the outside, in addition to an identification target parameter as described in the third embodiment. Therefore, the numerical controller 1c according to the fourth embodiment can obtain the effect of calculating an identification result preferentially for a combination of parameters specified by an input from the outside.

The configurations described in the above-mentioned embodiments give examples of the content of the present invention. The configurations can be combined with another well-known technique, and some of the configurations can be omitted or changed within a range that does not depart from the gist of the present invention.

Reference List

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.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• JP 2017094463 [0006]

Claims (8)

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 rotating speed of the spindle and a feed speed; a data acquisition unit for synchronizing a control signal for controlling the machine tool with an operation condition signal and for outputting the synchronized signals as identification data, the control signal being generated based on the identification operation command, the operation condition signal indicating an operation condition of the machine tool operated on the basis of 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 characteristics of a machining phenomenon between the tool and the workpiece, and performing identification of the selected parameter using the identification data. Numerical control device according to claim 1 wherein, based on the determination result of the vibration determination unit, the identification unit further selects an identifiable characteristic dynamics parameter as the selected parameter from characteristic dynamics parameters representing characteristics of the vibration of the machine tool. 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 instructing to indicating changing 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 operated based on the control signal Indicates machine tool, and the synchronized signals as the identification data outputs to the vibration determination unit and the identification unit. Numerical control device according to claim 3 comprising an input unit for receiving an input of the identification target parameters from the outside. 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 rotating speed and the feed speed with respect to time when the rotating speed and the feed speed are changed by the identification operation command, and the identification operation generation unit generates the identification operation command based on the command pattern information. Numerical control device according to claim 4 or 5 , wherein the input unit receives an input from the outside as a numerical control program. Numerical control device according to claim 4 or 5 wherein the input unit receives input from the outside in a form of interactive programming. Numerical control device according to one of Claims 1 until 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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