CN113874798B - Numerical control device - Google Patents

Numerical control device Download PDF

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Publication number
CN113874798B
CN113874798B CN201980096558.5A CN201980096558A CN113874798B CN 113874798 B CN113874798 B CN 113874798B CN 201980096558 A CN201980096558 A CN 201980096558A CN 113874798 B CN113874798 B CN 113874798B
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identification
unit
vibration
tool
numerical control
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CN113874798A (en
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高币一树
铃木教和
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National University Corp Donghai National University
Mitsubishi Electric Corp
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National University Corp Donghai National University
Mitsubishi Electric Corp
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/404—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/37—Measurements
    • G05B2219/37435—Vibration of machine
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/41—Servomotor, servo controller till figures
    • G05B2219/41115—Compensation periodical disturbance, like chatter, non-circular workpiece

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  • Engineering & Computer Science (AREA)
  • Human Computer Interaction (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Automatic Control Of Machine Tools (AREA)
  • Numerical Control (AREA)

Abstract

A numerical control device (1) according to the present invention controls the operation of a machine tool (2) for machining a workpiece with a tool, and comprises: a simultaneous movement generation unit (14) that generates a simultaneous movement command that causes the spindle rotation speed and the feed speed to each independently and continuously vary; a data acquisition unit (16) that synchronizes a control signal for controlling the work machine, which is generated based on the same-purpose operation command, with an operation state signal indicating the operation state of the corresponding work machine (2) and outputs the synchronized control signal as same-purpose data; a vibration determination unit (12) that determines, based on the same-purpose data, whether the vibration state of the machine tool (2) is stable machining, chatter vibration, or forced vibration; and a determination unit (13) that selects, as a selection parameter, a processing characteristic parameter that can be determined among processing characteristic parameters that indicate characteristics of a processing phenomenon between the tool and the workpiece, based on the determination result of the vibration determination unit (12), and determines the selection parameter using the determination data.

Description

Numerical control device
Technical Field
The present invention relates to a numerical control device for controlling a machine tool.
Background
A machine tool is a machining device that applies force or energy to a workpiece using a tool to perform a machining process, i.e., a removal process, in which unnecessary parts are removed from the workpiece. In particular, in cutting, which is one of the removal processes, the cutting edge of the tool is brought into contact with the workpiece at a high speed, thereby causing shearing damage to the surface of the workpiece, and the process of scraping an unnecessary portion of the workpiece is performed.
Since the cutting process is a physical phenomenon in which the machining process and the mechanical dynamics affect each other, it is preferable to manage both the machining states simultaneously. Here, the machining process means a series of processes of forming a machined surface while cutting chips are generated by the penetration of the tool tip into the workpiece. The mechanical dynamics means the motion of a mechanical member when the member constituting the machine vibrates by a vibration source inside and outside the machine. In general, cutting is a phenomenon in which various physical phenomena including the above-described machining process and mechanical dynamics are complicated to affect each other, and thus it is difficult to perform comprehensive analysis. Therefore, the evaluation target is limited at the production site, and thus the processing management corresponding to the purpose is achieved.
As described above, in the cutting processing, the mechanical dynamics and the processing process affect each other, and therefore the state of the working machine before or after the processing and the state of the working machine during the processing are different. That is, the state of the work machine during machining cannot be accurately estimated before or after the machining. Thus, the information obtained during the machining is preferably used to identify the mechanical dynamics and the machining process. By using the results recognized by the mechanical dynamics and the machining process, the operator in the production site can effectively perform improvement work such as management of tool life, efficient setting of machining conditions, design change of the fixing jig, and the like. Thus, improvement in productivity is expected.
As a method for performing parameter identification based on information obtained by sequentially changing processing conditions in actual processing, the following method is proposed in patent document 1. In the method described in patent document 1, an adaptive spectrum is calculated from displacements and forces generated when machining is performed by a plurality of spindle speeds, and a natural frequency of a tool is calculated from peaks obtained when the adaptive spectrums of the spindle speeds are combined. In this method, the working machine is operated to perform machining so that the spindle rotational speed is changed stepwise in a single operation of each feed shaft or in a composite operation of the feed shafts, and an adaptive spectrum is calculated using the detection results of displacement and force during machining.
Patent document 1: japanese patent laid-open publication No. 2017-94463
Disclosure of Invention
However, in the method described in patent document 1, the spindle rotation speed is changed stepwise by setting the feed amount in which chatter does not occur, and thereby various adaptive spectrums are obtained, and the natural frequency is calculated. Accordingly, the method described in patent document 1 has a problem that only the natural frequency can be identified, and the machining characteristic parameters such as the relative cutting resistance cannot be identified. In the method described in patent document 1, when parameters other than the natural frequency are identified, it is necessary to perform other identification operations. In the method described in patent document 1, since the spindle rotation speed is changed only stepwise to a plurality of predetermined stages, it takes time to obtain parameters corresponding to various spindle rotation speeds.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a numerical control device capable of effectively recognizing a machining characteristic parameter in a short time.
In order to solve the above-described problems and achieve the object, the present invention provides a numerical control apparatus for controlling an operation of a machine tool having a main shaft and a feed shaft, for machining a workpiece with a tool, the numerical control apparatus including: and an identification operation generation unit that generates an identification operation command that causes the rotational speed and the feed speed of the spindle to be changed independently and continuously. The numerical control device further includes: a data acquisition unit that synchronizes a control signal for controlling the work machine, which is generated based on the identification operation command, with an operation state signal indicating an operation state of the work machine that operates based on the control signal, and outputs the synchronized operation state signal as identification data; and a vibration determination unit that determines, based on the identification data, whether the vibration state of the machine tool is stable machining, chatter vibration, or forced vibration. The numerical control device further includes an identification unit that selects, as a selection parameter, a processing characteristic parameter that can be identified among processing characteristic parameters indicating characteristics of a processing phenomenon between the tool and the workpiece, based on a result of the determination by the vibration determination unit, and identifies the selection parameter using identification data.
ADVANTAGEOUS EFFECTS OF INVENTION
The numerical control device according to the present invention has an effect that the machining characteristic parameters can be effectively identified in a short time.
Drawings
Fig. 1 is a block diagram showing a configuration example of a numerical control device according to embodiment 1.
Fig. 2 is a diagram showing an example of a pattern of the recognition operation instruction generated by the recognition operation generating unit according to embodiment 1.
Fig. 3 is a diagram showing an example of a pattern of the recognition operation instruction generated by the recognition operation generating unit according to embodiment 1.
Fig. 4 is a diagram showing an example of a pattern of the recognition operation instruction generated by the recognition operation generating unit according to embodiment 1.
Fig. 5 is a schematic diagram showing a case where disturbance force is transmitted to the table in the case where the workpiece fixed to the table vibrates due to the cutting force in embodiment 1.
Fig. 6 is a view showing an example of the rotation angle of the tool in which the tool tip contacts the workpiece in embodiment 1.
Fig. 7 is a view showing an example of the rotation angle of the tool in embodiment 1, in which the tool tip does not contact the workpiece.
Fig. 8 is a diagram showing cutting at the 1 st cutting edge when an offset amount is generated between the center of the tool and the center of rotation of the spindle in embodiment 1.
Fig. 9 is a diagram showing cutting at the 2 nd edge in the case where an offset amount is generated between the tool center and the spindle rotation center in embodiment 1.
Fig. 10 is a flowchart showing an example of the identification processing procedure in the identification unit of embodiment 1 in the case where the vibration determination unit determines that the vibration is generated.
Fig. 11 is a flowchart showing an example of the operation of the numerical control device according to embodiment 1.
Fig. 12 is a diagram showing a configuration example of the processing circuit of embodiment 1.
Fig. 13 is a block diagram showing a configuration example of the numerical control device according to embodiment 2.
Fig. 14 is a flowchart showing an example of the operation of the numerical control device according to embodiment 2.
Fig. 15 is a block diagram showing a configuration example of the numerical control device according to embodiment 3.
Fig. 16 is a block diagram showing a configuration example of the numerical control device according to embodiment 4.
Detailed Description
The numerical control device according to the embodiment of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to the present embodiment.
Embodiment 1.
Fig. 1 is a block diagram showing a configuration example of a numerical control device 1 according to embodiment 1 of the present invention. The numerical control device 1 according to embodiment 1 controls the operation of the work machine 2 by transmitting a control signal to the work machine 2, and receives an operation state signal indicating the operation state of the work machine 2 from a sensor not shown.
The machine tool 2 has a main shaft and a feed shaft, and processes a workpiece with a tool. Specifically, the machine tool 2 performs cutting processing on a workpiece by operating at least one of a tool and the workpiece. For example, the work machine 2 includes: a spindle that imparts rotational motion to a tool or a workpiece; and a feed shaft which is a servo shaft for imparting a position to the tool or the workpiece. The main shaft and the feed shaft each have a motor.
The work machine 2 includes a sensor that detects an operation state of the work machine 2 and outputs a detection result as an operation state signal. The sensors included in the machine tool 2 include a sensor capable of detecting vibration of at least one of the tool and the workpiece. The sensor capable of detecting vibration of at least one of the tool and the workpiece is, for example, a linear encoder and a current sensor provided in the machine tool 2 in advance 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 of the motor of each shaft. Other examples of the sensor include an acceleration sensor, a position sensor, a force sensor, and a microphone. Next, as an example, the sensors included in the machine tool 2 are a linear encoder, a current sensor, and a force sensor. The force sensor is provided on or in a member such as a table constituting the feed shaft. The installation position of the force sensor is not limited to this, and may be a position where the force between the tool and the workpiece can be detected.
As shown in fig. 1, the numerical control device 1 includes a correction unit 11, a vibration determination unit 12, an identification unit 13, an identification operation generation unit 14, a drive control unit 15, and a data acquisition unit 16. The operation of each part of the numerical control device 1 of embodiment 1 will be described.
The recognition operation generating unit 14 generates a recognition operation command for changing the spindle rotation speed and the feed speed of the machine tool 2 independently and continuously, and outputs the recognition operation command to the drive control unit 15. The spindle rotation speed is the rotation speed of the spindle, and represents the rotation of the spindle by several weeks per unit time. The recognition operation is an operation for generating a control signal and an operation state signal by the drive control unit 15 and the work machine 2, respectively, in order to acquire recognition data, which is data used when the recognition unit 13 executes recognition processing described later. The identification operation command is a command generated for performing an identification operation, and includes a command for the spindle rotation speed and a command for the feed speed.
Fig. 2 to 4 are diagrams showing examples of patterns of the recognition operation instructions generated by the recognition operation generating unit 14 according to embodiment 1. Hereinafter, a mode of recognizing an operation instruction is also referred to as an instruction mode. Fig. 2 to 4 show command patterns in which the spindle rotation speed and the feed speed continuously vary from the recognition operation start time t1 to the recognition operation end time t 2. In fig. 2 to 4, the horizontal axis represents time (time), the vertical axis represents spindle rotation speed in the upper layer, and the feeding speed in the lower layer. Hereinafter, the spindle rotation speed and the feed speed are sometimes referred to as S, F.
Here, S0 is the reference spindle rotation speed, which is the spindle rotation speed before the identification operation, and S1 is the maximum value of the spindle rotation speed during the identification operation. T1 is a time constant when accelerating from a state where the spindle rotation speed is S0 to a state where the spindle rotation speed is S1. T2 is a time constant when accelerating from a state where the feed speed is F0 to a state where the feed speed is F1. Fig. 2 is a command pattern for accelerating and decelerating the spindle rotation speed and the feed speed, respectively. In the example shown in fig. 2, after acceleration with a time constant T1, the spindle rotation speed is decelerated if the spindle rotation speed is referred to as S1. If the spindle rotation speed is reduced to S0 by deceleration, S0 is maintained. If the spindle rotation speed is reduced to S0, the feed speed is accelerated by a time constant T2 until it reaches F1. Then, if the feed speed becomes F1, the feed speed is decelerated.
Fig. 3 shows a command pattern of the deceleration of the spindle rotation speed after the acceleration of the spindle rotation speed, the acceleration of the feed speed and the subsequent deceleration. Fig. 4 shows a command pattern in which the spindle rotation speed is accelerated and then decelerated, and the feed speed is repeatedly accelerated and decelerated in a change in the spindle rotation speed.
In fig. 2 to 4, S1 is shown as the maximum value of the spindle rotation speed during the recognition operation, and the spindle rotation speed is changed between S0 and S1, but the recognition operation generating unit 14 may set the minimum value S2 of the spindle rotation speed during the recognition operation, and a command pattern that changes in the range of S0 to S2 is shown. Similarly, regarding the feeding speed, a minimum value F2 of the feeding speed in the recognition operation may be set, and a command pattern that changes between F0 and F2 may be shown.
Although the command pattern for acceleration and deceleration in a triangular waveform is illustrated in fig. 2 to 4, the recognition operation generating unit 14 can generate an arbitrary command pattern if the command pattern is a command pattern in which the spindle rotation speed and the feed speed are continuously accelerated and decelerated. For example, the recognition operation generating unit 14 may generate a command pattern that changes in a sine wave shape or an S-shaped curve shape instead of the triangular wave shape.
As described above, the recognition operation generating unit 14 can generate the recognition operation including various combinations of the spindle rotation speed and the feed speed by changing the spindle rotation speed and the feed speed independently of each other.
It is known that the magnitude of the cutting force, which is the force generated when the tool cuts a workpiece, is mainly dependent on the feed amount per 1 edge, and the vibration cycle of the cutting force is mainly dependent on the spindle rotation speed. Therefore, in general, when the spindle rotation speed and the feed speed are changed, they are changed at the same ratio. As a result, the load applied to the edge of the cutter becomes constant, and therefore the magnitude of the cutting force generated by the edge of the cutter 1 does not change. Since the recognition operation generating unit 14 changes the spindle rotation speed and the feed speed independently, the magnitude and the amplitude of the cutting force can be changed variously, and various vibration states described later can be generated in the machine tool 2 during the recognition operation.
The drive control unit 15 generates a control signal for controlling the work machine 2 such that the main shaft and the feed shaft of the work machine 2 are operated in an operation specified by the recognition operation command based on the recognition operation command generated by the recognition operation generating unit 14. Here, the control signal is a command for the main shaft and the feed shaft of the machine tool 2, and includes at least 1 of a position command, a speed command, and a current command for each motor of the main shaft and the feed shaft. Further, when the recognition operation command is not input from the recognition operation generating unit 14, that is, when the normal machining operation is performed, the drive control unit 15 generates a control signal for the machine tool 2 based on the machining path and the reference spindle rotation speed and the reference feed speed in the machining path. The drive control unit 15 acquires a correction signal from a correction unit 11 described later, corrects a control signal for the machine tool 2 based on the correction signal, and outputs the corrected control signal to the machine tool 2.
The drive control unit 15 sets a machining path and a reference spindle rotation speed and a reference feed speed in the machining path in advance. The machining path and the reference spindle rotational speed and the reference feed speed in the machining path may be provided by a numerical control program. Even when the recognition operation command is input from the recognition operation generating unit 14, the drive control unit 15 generates a control signal so that the set machining path is not changed, but only the spindle rotation speed and the feed speed are changed in accordance with the recognition operation command. The work machine 2 includes a motor and a motor control device for each shaft, and the motor control device controls the motor based on feedback signals such as a control signal, a position, a speed, and a motor current received from the drive control unit 15. The feedback signal of the position and the speed is calculated based on the position detected by the linear encoder, and the feedback signal of the motor current is calculated based on the detection result of the current sensor. The feedback signals of the position, the speed, and the motor current are hereinafter referred to as a position feedback signal, a speed feedback signal, and a current feedback signal, respectively.
The data acquisition unit 16 synchronizes the control signal output from the drive control unit 15 with an operation state signal indicating the operation state of the work machine 2 operated based on the control signal, and outputs the synchronized operation state signal as identification data. Specifically, the data acquisition unit 16 uses the control signal output from the drive control unit 15 and the operation state signal output from the sensor of the machine tool 2 to synchronize the data included in each signal with each other in time, and outputs the synchronized data as the identification data to the vibration determination unit 12 and the identification unit 13. As described above, the operation state signal is a signal indicating the operation state of the machine tool 2, and includes a signal capable of detecting vibration of at least one of the tool and the workpiece. Here, since the linear encoder, the current sensor, and the force sensor are provided as the sensors as described above, the data acquisition unit 16 can acquire feedback signals of the positions, speeds, and currents of the main shaft and the feed shaft, and forces, torques, and the like detected by the force sensor as operation state signals. Hereinafter, the actual measurement values such as force and torque detected by the force sensor will also be referred to as force information. Since the operation state signal is generated after the control signal is received by the work machine, the operation state signal is delayed in time with respect to the corresponding control signal due to the influence of the time required for communication or the like. Therefore, the data acquisition unit 16 compensates for the time difference between the two signals by shifting the data included in the operation state signal or the data included in the control signal by a time corresponding to the difference in communication time or the like. The data acquisition unit 16 sums the data whose temporal offset has been compensated, that is, the synchronized data, as the identification data, and outputs the data to the vibration determination unit 12 and the identification unit 13.
The vibration determination unit 12 determines whether or not vibration has occurred in the machine tool 2 using the identification data, determines the type of vibration when it is determined that vibration has occurred, and outputs the determination result to the identification unit 13. Next, the details of the vibration determination unit 12 will be described. The vibration determination unit 12 determines whether or not vibration has occurred, and indicates vibration having a larger amplitude than a vibration component due to cutting forces of the tool and the workpiece.
The determination of occurrence of vibration by the vibration determination unit 12 is performed by a known means. For example, when the force or torque indicated by the force information output from the force sensor exceeds a predetermined amplitude in the time zone, it is determined that vibration has occurred. The type of the signal used for vibration determination is not limited to the force information, and the vibration determination unit 12 may determine whether or not vibration has occurred using a current feedback signal included in the operation state signal, for example. The vibration determination unit 12 may convert a signal used for determining whether or not vibration has occurred into a signal in a frequency region, and determine that vibration has occurred when a vibration component having a maximum amplitude in the frequency region exceeds a predetermined amplitude.
In addition, there are forced vibration and self-excited vibration in the vibration phenomenon, and chatter vibration is one of the self-excited vibrations. The forced vibration is a vibration phenomenon in which a cutting force Shi Zhenyuan is excited by a member existing in the vicinity of a tool or a workpiece. By this property, it is known that the vibration frequency of the forced vibration becomes an integer multiple of the basic cutting frequency. On the other hand, self-excited vibration, i.e., chatter vibration, is a vibration phenomenon that occurs due to instability of a system composed of a cutting force and displacement of the member. From this property, the vibration frequency of the chatter is known to be a non-integer multiple of the basic cutting frequency. In the above description, the basic cutting frequency is a frequency obtained by multiplying the spindle rotation speed by the number of tool edges.
When it is determined that vibration has occurred, the vibration determination unit 12 determines the type of vibration. Specifically, the vibration determination unit 12 determines whether the generated vibration is forced vibration or chatter vibration as a determination of the type of vibration. The determination of the kind of vibration is performed based on whether or not the frequency of the determined vibration is an integer multiple of the basic cutting frequency. That is, if the frequency of the vibration is an integer multiple of the basic cutting frequency, the vibration determination unit 12 determines that the vibration is forced, and if the frequency is a non-integer multiple of the basic cutting frequency, the vibration is determined to be chatter.
When the vibration determination unit 12 determines that no vibration has occurred, it determines that the machining is stable. The stable machining is a machining state in which only a vibration component due to the cutting force of the tool and the workpiece is generated, and is a machining state in which vibration near the natural frequency of the member is not excited.
The vibration determination unit 12 always performs the above-described processing, thereby determining whether the data for identification at each time is any one of stable processing, forced vibration, and chatter vibration, and outputs the determination result to the identification unit 13 as the vibration determination result. That is, the vibration determination unit 12 determines which of the plurality of states of stable machining, forced vibration, and chatter vibration the vibration state of the machine tool 2 is based on the identification data.
The identification unit 13 selects a distinguishable machining characteristic parameter from among the machining characteristic parameters as a selection parameter based on the determination result of the vibration determination unit 12, and performs identification of the selection parameter using the identification data input from the data acquisition unit 16. The identification unit 13 further selects, as the selection parameter, a dynamic characteristic parameter which can be identified among the dynamic characteristic parameters, based on the determination result of the vibration determination unit 12. Hereinafter, the selection parameter is also referred to as a recognizable parameter. The identification unit 13 outputs the result of the identification process to the correction unit 11. The identification process is performed using the identification data and the processing condition information. The machining condition information is information indicating the machining condition in the recognition operation, and is information set in advance in the recognition unit 13. The machining condition information includes, for example, a tool diameter, a number of tool edges, a tool torsion angle, a tool axial feed amount, a tool radial feed amount, and a machining pattern of up-cutting or down-cutting.
In the following, an example in which the identification unit 13 identifies both the dynamic characteristic parameter and the machining characteristic parameter is described, but the identification unit 13 may identify only either the dynamic characteristic parameter or the machining characteristic parameter. For example, the identification unit 13 selects a distinguishable machining characteristic parameter from among the machining characteristic parameters as a selection parameter based on the determination result of the vibration determination unit 12, and performs identification of the selection parameter using identification data.
In general, the spindle rotation speed and the feed speed in processing are specified at constant values. In this case, the identification unit 13 can acquire only identification data in the case where processing is performed by a set of the spindle rotation speed and the feed speed. As described above, since the identification data includes the operation state signal detected by the sensor of the machine tool 2, the identification unit 13 can acquire only the operation state signal when the machining is performed by a set of the spindle rotation speed and the feed speed. However, in the present embodiment, since the command in which the spindle rotation speed and the feed speed are continuously changed is generated by the recognition operation generating unit 14, the recognition unit 13 can acquire the operation state signal in the case where the machining is performed by the spindle rotation speed and the feed speed which are different in combination at each time.
Here, the dynamic characteristic parameter and the processing characteristic parameter will be described. The dynamic characteristic parameter is a parameter indicating a characteristic of a dynamic model described later, and is a parameter indicating a characteristic of vibration of the work machine 2. The dynamic characteristic parameters are, for example, equivalent mass, damping coefficient, natural frequency. On the other hand, the machining characteristic parameter is a parameter indicating a characteristic of a machining process model described later, and is a parameter indicating a characteristic of a machining phenomenon between the tool and the workpiece. The machining parameters are, for example, the relative cutting resistance, the edge force, the tool eccentricity and the tool wear amplitude.
The dynamic model is a mathematical model describing dynamics of mechanical components, tools, and workpieces inside the machine tool 2. An example of the kinetic model is described below. Fig. 5 is a schematic diagram showing a case where disturbance force is transmitted to the table in the case where the workpiece fixed to the table vibrates due to the cutting force in embodiment 1. Fig. 5 shows an example in which the work machine 2 performs milling by rotation of the tool 33. In fig. 5, a configuration example is assumed in which a workpiece 32 is placed on a table 31 constituting a drive shaft, and a tool system 34 constituting a spindle holds a tool 33. In fig. 5, the relative displacement 35 shows the relative displacement of the workpiece tip with respect to the vibration direction of the table 31, the cutting force 36 shows the cutting force in the workpiece 32, and the disturbance force 37 shows the disturbance force transmitted to the table 31. The relationship between the cutting force 36, the disturbance force 37, and the relative displacement 35 at this time can be expressed by the following expression (1). The dynamic model shown in the formula (1) is a mathematical model for calculating the disturbance force 37 transmitted to the feed shafts by the mechanical structure including the tool 33 or the workpiece 32 when the cutting force 36 is generated, and calculating the positional deviation generated at each feed shaft by the mechanical structure when the cutting force 36 is generated.
1 (1)
In this context,
f c : cutting force, f d : interference force, m t : the equivalent mass of the product is that,
x: relative displacement of the front end of the workpiece with respect to the direction of vibration of the table
ζ: attenuation coefficient omega n : natural frequency of vibration
The dynamic model shown in the formula (1) is described as a 1-degree-of-freedom vibration system for the workpiece 32 on the table 31, but the dynamic model is not limited to the above example. For example, the vibration system may be described as a multiple degree of freedom vibration system including a fixing portion for fixing the workpiece 32 and the table 31. A dynamic model relating to the tool side member constituted by the tool 33, the tool system 34, and the spindle motor can be set. Further, a dynamic model may be set as a vibration system in which a workpiece side member and a tool side member including a fixing portion for fixing the workpiece 32 and the table 31 are combined.
The machining process model is a mathematical model describing a cutting process between a tool and a workpiece. An example of the processing model is shown in the following formula (2).
2, 2
f c : cutting force, K c : relative cutting resistance, K ce : the force of the edge is applied to the surface of the substrate,
a: axial feed amount of the cutter, h: the workpiece is cut to a thickness, Cutter rotation angle, t: time of
Angle of engagement of the tool>Unengaged angle of tool
The above equation (2) is an equation for calculating the cutting force applied to the workpiece 32 by the tool 33 based on the cutting thickness corresponding to the rotation angle of the tool 33 at each time. Here, the cut thickness refers to a thickness at which the workpiece 32 is cut when the blade tip of the cutter 33, that is, the cutter blade tip passes through the workpiece 32. As shown in fig. 6 and 7, the cutting force is calculated as a value equal to or greater than zero when the tool tip is at an angle that is in contact with the workpiece 32, but is calculated as zero when the tool tip is not in contact with the workpiece 32. Fig. 6 is a view showing an example of the rotation angle of the tool 33 in which the tool tip contacts the workpiece 32 in embodiment 1, and fig. 7 is a view showing an example of the rotation angle of the tool 33 in which the tool tip does not contact the workpiece 32. That is, at each rotation angle or timing of the cutter 33, whether or not to contact the workpiece is determined based on the positional deviation, the cut thickness is calculated when the cutter tip contacts the workpiece 32, and the cut thickness is calculated as zero when the cutter tip does not contact the workpiece 32.
The calculation shown in the formula (2) is performed in 3 directions, i.e., the tangential direction, the radial direction, and the axial direction of the tool, whereby the cutting force in 3 directions can be calculated. In the machining process model, the cutting force in the tool reference coordinate system is calculated by multiplying the cutting force having the above 3-directional component by a rotation matrix corresponding to the rotation angle of the tool 33, that is, the tool rotation angle, and performing coordinate transformation. An example of the coordinate transformation is shown in equation (3).
3
f cx : cutting force in X-axis direction, f cy : cutting force in Y-axis direction, f cz : the cutting force in the direction of the Z axis,
f ct : cutting force in tangential direction of tool, f cr : cutting force in the radial direction of the tool, f ca : axial cutting force of tool
The calculation shown in the above-described formulas (2) and (3) is performed in the number of blade edges of the tool, and the calculation results are accumulated, whereby the cutting force generated by the entire tool can be finally calculated. The machining process model represented by the formula (2) is a mathematical model for calculating a cutting thickness based on a relative position between the tool tip and the workpiece 32, which is a machining object of the tool 33, and a tool rotation angle, and calculating a cutting force generated between the tool and the workpiece based on the cutting thickness. The cut thickness in the formula (2) can be calculated by the formula (4) using the feed amount per 1 blade and the tool rotation angle.
4. The method is to
c: feed per 1 blade
As another example, the ablation thickness can be calculated using formula (5).
5. The method is to
v: tool center displacement in the tool radial direction, w: the displacement of the front machining surface in the radial direction of the cutter,
Δr: correction amounts corresponding to the respective tool tips, N tooth : cutter tip numbering
Equation (5) is a calculation equation for adding the fluctuation amount calculated from the current tool displacement and the difference between the front machining surface and the machining surface generated by the tool edge before the 1-edge, and adding the correction amount corresponding to each tool edge to the equation (4). In the calculation shown in the formula (5), the cutting thickness is corrected by the difference between the displacement amount affecting the shape of the machined surface and the displacement amount generated at the current tool edge, within the displacement amount generated at the current tool edge and the displacement amount generated at the tool edge before 1 or more edges. That is, the cutting thickness is calculated based on the difference between the locus generated by the current tool edge related to cutting and the locus of the tool edge that affects the shape of the machined surface in the tool edge that is 1 or more edge-ahead with the current tool edge as a reference.
Here, the tool center displacement v is a displacement corresponding to a component in a direction from the tool center to the tool edge among the relative displacements x in the expression (1). The pre-machined surface displacement w is a displacement generated in the machined surface by a relative displacement x at the time of cutting by the tool edge before 1 edge or more. The tool edge before 1 edge or more is the tool edge related to cutting at the previous timing than the timing based on the tool edge related to cutting. For example, in a tool having 2 blades, when the tool tip in the current cutting is the 2 nd blade, the tool tip before the 1 st blade is the 1 st blade before 180 degrees of rotation, the 2 nd blade before 360 degrees of rotation, and the tool tip before the 3 rd blade is the 1 st blade before 540 degrees of rotation. When the tool is displaced and the tip is temporarily separated from the workpiece 32 during cutting, the current tool tip cuts not only the front machined surface generated by the tool tip before 1 edge but also the front machined surface generated by the tool tip before 2 edges or more.
In the calculation shown in the formula (5), the cutting thickness is corrected by a correction amount corresponding to the number indicating the tool edge, that is, the tool edge number and the tool rotation angle. Here, the correction amount is introduced to correct a change in the cutting thickness caused by cutting with a rotation radius different for each tool edge. As an example of the correction amount to be introduced, the following is given. For example, when a specific edge is worn, curled, or the like, the rotation radius of the edge becomes shorter than that of other edges, and thus correction amounts corresponding to the wear width, the curled width, or the like are added. As another example, in the case where there is an installation error of the blade edge in the blade edge replacement type tool, a correction amount corresponding to the installation error is added. As another example, when the spindle rotation center does not coincide with the tool center, that is, when there is tool eccentricity, a correction amount corresponding to the tool eccentricity amount is added. Further, the tool center is the center of the circumscribed circle of the tool.
The tool eccentricity is an amount by which the cutting thickness is corrected by an amount by which the rotation radius of the tool tip increases or decreases for each tool tip when an offset occurs between the tool center and the spindle rotation center as shown in fig. 8 and 9. Fig. 8 is a diagram showing the case of cutting at the 1 st edge when an offset is generated between the tool center and the spindle rotation center in embodiment 1, and fig. 9 is a diagram showing the case of cutting at the 2 nd edge when an offset is generated between the tool center and the spindle rotation center. The 1 st cutting edge 43 and the 2 nd cutting edge 44 are cutting edges of the cutter. In the examples shown in fig. 8 and 9, there is a deviation between the tool center 41 and the spindle rotation center 42. In the case described above, it is necessary to correct the cut thickness with respect to the cut thickness in the case where there is no deviation, and the tool eccentricity amount indicates the correction amount at this time. That is, the cutter eccentricity corresponding to the rotation angle of the cutter 33 is added or subtracted to or from the cut thickness. The case where the cutting thickness is corrected by the correction amount is not limited to the above case, and the correction amount may be appropriately changed in accordance with the phenomenon occurring at the edge of the cutter.
The processing model is not limited to the formula (2). For example, the relative cutting resistance value may be changed using the formula (2) in the case of a high cutting speed equal to or higher than the threshold value and in the case of a low cutting speed lower than the threshold value. The right side of the expression (2) may be a model to which a process damping force is added. Here, the process damping force is a force generated by the contact of the relief surface of the tool tip with the workpiece. The process damping can be expressed, for example, as a value obtained by multiplying the relief surface contact area by a process damping coefficient. In this case, the process damping coefficient becomes one of the processing characteristic parameters.
As another example, a machining process model for a tool having a torsion angle may be used. Specifically, the cutting force in each of the divided tools having a small thickness may be calculated by dividing the tool into the tools having a small thickness in the axial direction, and the cutting force may be calculated by integrating the cutting forces in the axial direction of the tool. As another example, a model may be used in which the cutting thickness and the cutting force are calculated by finite element analysis.
Next, when the dynamic model is represented by the formula (1) and the machining process model is represented by the formula (2), the distinguishable parameters are discriminated based on the vibration determination result, and the process of discriminating the parameters will be described. The candidates for parameters that can be identified below are dynamic characteristic parameters, namely equivalent mass, damping coefficient, natural frequency, machining characteristic parameters, namely relative cutting resistance, edge force, and tool eccentricity.
If a vibration determination result indicating that the vibration determination unit 12 is one of stable machining, forced vibration, and chatter vibration is input as a vibration determination result, the identification unit 13 performs the following processing in accordance with the vibration determination result. In addition, the case where the forced vibration and the chatter vibration occur simultaneously is rare, and in the case described above, the chatter vibration is determined and identified.
[ case where the result of determination is stable processing ]
The identification unit 13 selects machining characteristic parameters, that is, the relative cutting resistance and the edge force, as distinguishable parameters. The identification unit 13 identifies the relative cutting resistance and the edge force by the following processing. The identification unit 13 calculates the relative 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 advance in the identification unit 13. That is, the relative cutting resistance and the edge force in the formula (2) are calculated so that the calculated value of the force in each axial direction calculated when the formulas (2) and (4) are substituted into the formula (3) substantially coincides with the measured value of the force detected by the force sensor. The calculation method of the relative cutting resistance and the edge force may be a known optimization method or numerical simulation. For example, a least 2 multiplication or a gradient method can be used.
[ case of forced vibration as a result of determination ]
The identification unit 13 selects a dynamic characteristic parameter, that is, an attenuation coefficient, and a natural frequency, and a machining characteristic parameter, that is, a relative cutting resistance and an edge force, as distinguishable parameters. The identification unit 13 identifies the damping coefficient, natural frequency, relative cutting resistance, and edge force by the following processing.
The identification unit 13 uses the force information output from the force sensor and the machining conditions recorded in advance in the identification unit 13 to identify the damping coefficient, natural frequency, relative cutting resistance, and edge force according to equations (1) to (4). Specifically, f in the following formula (6) obtained by deforming the formula (1) d Substituting the measured value of the force detected by the force sensor.
6. The method is to
Then, the calculated value of the force in each axial direction calculated when substituting the formula (2) and the formula (4) into the formula (3) is substituted into f in the formula (6) c . At this time, since there is a combination of the damping coefficient and the natural frequency and the relative cutting resistance and the edge force that satisfy the expression (6), the identification unit 13 calculates a combination of the damping coefficient and the natural frequency and the relative cutting resistance and the edge force that satisfy the expression (6). Specifically, the identification unit 13 searches for the damping coefficient, natural frequency, and relative cutting resistance and edge force using a gradient method so that errors on both sides of the equation (6) are minimized. As another method, the damping coefficient and the natural frequency and the relative cutting resistance and the edge force can be calculated by the least 2 multiplication.
[ case of vibration as the judgment result ]
The identification unit 13 selects, as parameters that can be identified, dynamic characteristics parameters, namely equivalent mass, damping coefficient, natural frequency, and machining characteristics parameters, namely relative cutting resistance, edge force, and tool eccentricity. The identification unit 13 identifies the equivalent mass, the damping coefficient, the natural frequency, the relative cutting resistance, the edge force, and the tool eccentricity by the following processing.
The identification unit 13 uses the force information output from the force sensor and the machining conditions recorded in advance in the identification unit 13 to identify the equivalent mass, the damping coefficient, the natural frequency, the relative cutting resistance, the edge force, and the tool eccentricity according to the equations (1), (2), (3), and (5). Specifically, the equivalent mass, the damping coefficient, the natural frequency, the relative cutting resistance, the edge force, and the tool eccentricity can be identified in the order shown in fig. 10.
Fig. 10 is a flowchart showing an example of the identification processing procedure in the identification unit 13 according to embodiment 1 when the vibration determination unit 12 determines that vibration is generated. First, the identification unit 13 sets initial values for the parameter sets in step S1. The set of parameters at this time is a combination of parameters of dynamic characteristic parameters, namely equivalent mass, damping coefficient, and natural frequency, and machining characteristic parameters, namely relative cutting resistance, edge force, and tool eccentricity.
In step S2, the identification unit 13 calculates the displacement amounts satisfying both the dynamic model and the machining process model. For example, the displacement amounts satisfying both the kinetic model, that is, the formula (1), and the processing model, that is, the formulas (2) and (5), are calculated. Here, the displacement amounts are the relative displacement x in the formula (1) and v, w in the formula (5).
In step S3, the identification unit 13 calculates the disturbance force when the displacement amount is given to the dynamics model. For example, the identification unit 13 applies the displacement amount calculated in step S2 to the dynamic model, that is, expression (1), to the disturbance force f d And (5) performing calculation.
In step S4, the identification unit 13 determines whether or not the error between the measured value of the force detected by the force sensor and the calculated value of the force calculated in step S3 is less than or equal to the allowable value. If the error is less than or equal to the allowable value (Yes in step S4), the identification unit 13 ends the identification process with the value of the set of parameters at that time as the identification result. When the error exceeds the allowable value (step S4 No), the identification unit 13 updates the values of the parameter group in step S5, and returns to the process in step S2.
As the method for updating the parameters in step S5, for example, a method of increasing or decreasing each parameter by a predetermined amount can be used. The identification process in the identification unit 13 when the vibration determination unit 12 determines that the vibration is generated is not limited to the processes of steps S1 to S5. For example, the expression (1), the expression (2), the expression (3), and the expression (5) may be combined, and each parameter may be calculated by using a least 2-multiplication.
Returning to the description of fig. 1, the correction unit 11 receives the dynamic characteristic parameter and the machining characteristic parameter, which are the identification results, from the identification unit 13, and outputs a correction signal for correcting the operation of the machine tool 2 to the drive control unit 15 based on the identification results. Specifically, simulation relating to mechanical dynamics and machining processes is performed in the correction unit 11, and a combination of a spindle rotation speed and a feed speed, in which the vibration amplitude of the tool edge is less than or equal to a predetermined value, is calculated. The correction unit 11 generates a correction signal for correcting the spindle rotation speed and the feed speed based on the calculated spindle rotation speed and feed speed, and outputs the correction signal to the drive control unit 15. Here, the predetermined value is a value preset in the correction unit 11, and is a value set to satisfy a dimensional tolerance that determines a machining result. The object to be corrected may include a feed amount in the axial direction of the tool or in the radial direction of the tool, in addition to the spindle rotation speed and the feed speed.
An example of the operation of the numerical control apparatus 1 according to embodiment 1 described above will be described with reference to fig. 11. Fig. 11 is a flowchart showing an example of the operation of the numerical control apparatus 1 according to embodiment 1. In step S11, the numerical control apparatus 1 starts the recognition operation. Specifically, the recognition operation generating unit 14 generates a recognition operation command, and the drive control unit 15 outputs a control signal to the work machine 2 so that the work machine 2 executes an operation specified by the recognition operation command, with respect to the work machine 2.
In step S12, the vibration determination unit 12 obtains identification data. Specifically, the data acquisition unit 16 acquires a control signal from the drive control unit 15, acquires an operation state signal from a sensor of the machine tool 2, generates identification data in which a time difference between the two 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 state of vibration based on the identification data. Specifically, the vibration determination unit 12 determines whether or not vibration has occurred based on the operation state signal of the identification data, and determines that the vibration state is stable processing when it is determined that vibration has not occurred. When it is determined that vibration has occurred, the vibration determination unit 12 determines which of forced vibration and chatter vibration is based on the frequency of the vibration. The vibration determination unit 12 outputs the determination result of the vibration state to the identification unit 13 as the vibration determination result.
In step S14, the identification unit 13 selects parameters that can be identified based on the identification data and the vibration determination result. Specifically, the identification unit 13 selects parameters that can be identified from the dynamic characteristic parameters and the machining characteristic parameters in accordance with the vibration determination result.
In step S15, the identification unit 13 uses the identification data to identify the parameters that can be identified selected in step S14. In step S16, after the identification operation up to step S15 is completed, that is, in the normal machining operation, the numerical control device 1 corrects the operation of the machine tool 2 based on the identification result. Specifically, the correction unit 11 generates a correction signal for correcting the operation of the work machine 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 and the reference spindle rotational speed and the reference feed speed in 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 a series of processes from step S11 to step S15 at any time during processing. After the recognition operation, the processing state can be improved by using the recognition result through the processing of step S16.
Next, the hardware configuration of the digital control apparatus 1 will be described. Each part of the numerical control apparatus 1 shown in fig. 1 is realized by a processing circuit. The processing circuitry may be circuitry having a processor or may be dedicated hardware.
In the case where the processing circuit is a circuit having a processor, the processing circuit is, for example, a processing circuit having a configuration shown in fig. 12. Fig. 12 is a diagram showing a configuration example of the processing circuit of embodiment 1. The processing circuit 200 has a processor 201 and a memory 202. When the respective units of the numerical control apparatus 1 are realized by the processing circuit 200 shown in fig. 12, the processor 201 reads out and executes the programs stored in the memory 202, thereby realizing them. That is, when each part of the numerical control apparatus 1 is realized by the processing circuit 200 shown in fig. 12, the functions thereof are realized by using software, that is, a program. The memory 202 is also used as a work area of the processor 201. The processor 201 is CPU (Central Processing Unit) or the like. The memory 202 is, for example, a nonvolatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, or the like, a magnetic disk, or the like.
In the case where the processing circuits implemented in the respective units of the numerical control device 1 are dedicated hardware, the processing circuits are FPGA (Field Programmable Gate Array) and ASIC (Application Specific Integrated Circuit), for example. Each part of the numerical control apparatus 1 may be implemented by combining a processing circuit having a processor and dedicated hardware. Each part of the numerical control device 1 may be realized by a plurality of processing circuits.
As described above, the numerical control device 1 according to embodiment 1 generates a command for continuously changing the speed with respect to the main shaft and the feed shaft, and gives the command to the main shaft and the feed shaft independently, thereby causing the machine tool to execute the recognition operation. The numerical control device 1 according to embodiment 1 determines the vibration state of the machine tool 2 based on the identification data collected by the identification operation, and identifies the identifiable machining characteristic parameters according to the determination result. As described above, the numerical control device 1 according to embodiment 1 can efficiently recognize the machining characteristic parameters in a short time. The numerical control device 1 according to embodiment 1 can also recognize a dynamic characteristic parameter that can recognize the state of vibration according to the determination result. Further, since the numerical control device 1 according to embodiment 1 can reproduce the vibration states of a plurality of types in one recognition operation for the machine tool 2, the operator can efficiently recognize the vibration states in a short time without changing the machining conditions each time. Further, by reproducing the chatter vibration state, the dynamic characteristic parameter and the machining characteristic parameter can be estimated at the same time. As a result, since the numerical control device 1 according to embodiment 1 can correct the control signal for the machine tool based on the identification result, machining can be continued without causing machining failure. In addition, if the spindle rotation speed is stepwise changed and identified, only peaks that are candidates for the natural frequency can be discretely searched for. In contrast, in the present embodiment, since the command for continuously changing the speed is generated for the spindle and the feed shaft as described above, the dynamic characteristic parameter and the machining characteristic parameter can be recognized with higher accuracy than in the case where the spindle rotation speed is changed stepwise.
The kinetic model and the processing model are not limited to the above-described formulas (1) and (2), and may be appropriately changed according to the machine structure and the processing method. Therefore, the dynamic characteristic parameter is not limited to the equivalent mass, the damping coefficient, and the natural frequency, and similarly, the machining characteristic parameter is not limited to the relative cutting resistance, the edge force, and the tool eccentricity. The dynamic characteristic parameter and the processing characteristic parameter can be appropriately changed in accordance with the dynamic model and the processing process model, and have the same effects as those of embodiment 1.
In embodiment 1, the configuration in which 1 work machine 2 is controlled by 1 numerical control device 1 has been described, but 2 or more work machines may be connected to numerical control device 1. For example, by generating a command for changing the spindle rotation speed for the 1 st working machine and generating a command for changing the feed speed for the 2 nd working machine and simultaneously giving an operation command to each working machine, the recognition can be completed in a shorter time than when the 1 st working machine is operated. In addition, although the working machine 2 that performs milling by rotation of the tool has been described in embodiment 1, the present invention can be applied to a working machine that performs turning by rotation of a workpiece.
In embodiment 1, the force sensor is configured to directly detect the force, but the indirect estimation of the force using another sensor can also have the same effect as embodiment 1. For example, using the motor current command, that is, the reference motor current and the position detected by the linear encoder, the data acquisition unit 16 or the identification unit 13 can calculate the force by the following equation (7).
7. The method of the invention
f est ＝K T I ref -Mü…(7)
f est : interference force of servo shaft, K T : the torque constant is set to be equal to the torque constant,
I ref : referring to motor current, M: equivalent mass of feed shaft, u: linear encoder detection position
As another example, the force can be calculated similarly using an acceleration sensor. In this case, using the acceleration detected by the acceleration sensor, the data acquisition unit 16 or the identification unit 13 can calculate the force by the following expression (8).
8. The method is used for preparing the product
f est ＝K T I ref -Mα…(8)
Alpha: acceleration sensing measurement
The formulas (7) and (8) are calculated formulas of force when the feed shaft is regarded as 1 inertial body, but a calculated formula which is regarded as a plurality of inertial bodies may be appropriately used in accordance with the structure of the feed shaft. Further, a term for compensating the friction force may be added.
Embodiment 2.
Fig. 13 is a block diagram showing a configuration example of a numerical control device according to embodiment 2 of the present invention. In embodiment 1, an example in which the identification process is performed based on the control signal and the operation state signal during the period in which the identification operation is performed once is described. In embodiment 1, when chatter is not generated in one identification operation, there is a parameter that cannot be identified from among the dynamic characteristic parameter and the machining characteristic parameter. In embodiment 2, an example of correcting the recognition operation when chatter is not generated during the execution of the recognition operation will be described. Hereinafter, the same reference numerals are used for the constituent elements having the same functions as those of embodiment 1, and overlapping description is omitted. The following description focuses on differences from embodiment 1.
As shown in fig. 13, the numerical control device 1a is the same as in embodiment 1 except that it includes an identification unit 13a and an identification operation generation unit 14a instead of the identification unit 13 and the identification operation generation unit 14 in embodiment 1. The identification unit 13a and the identification operation generation unit 14a are realized by a processing circuit in the same manner as the identification unit 13 and the identification operation generation unit 14 of embodiment 1.
The identification unit 13a selects parameters that can be identified from among the dynamic characteristic parameters and the machining characteristic parameters, using the vibration determination result input from the vibration determination unit 12, similarly to the identification unit 13 of embodiment 1. The identification unit 13a performs an identification process for identifying the selected identifiable parameter based on the identification data inputted from the data acquisition unit 16, and outputs the result of the identification process to the correction unit 11, similarly to the identification unit 13 of embodiment 1. The identification processing is performed by the same method as the identification unit 13 of embodiment 1 using the identification data and the processing condition information.
At least 1 of the dynamic characteristic parameter and the machining characteristic parameter is set in advance as a parameter to be identified in the identification unit 13 a. After performing the recognition processing of one or more times, the recognition unit 13a outputs a recognition operation correction signal to the later-described recognition operation generation unit 14a when there is an unrecognized parameter among the parameters to be recognized. The identification operation correction signal is a signal indicating the presence of an unrecognized dynamic characteristic parameter or processing characteristic parameter.
The recognition operation generating unit 14a generates a recognition operation command for changing the spindle rotation speed and the feed speed of the machine tool, and outputs the recognition operation command to the drive control unit 15, similarly to the recognition operation generating unit 14 of embodiment 1.
The recognition operation generating unit 14a corrects the command pattern of the recognition operation based on the recognition operation correction signal outputted from the recognizing unit 13 a. The identification unit 13a can identify the most various parameters when the machine tool is vibrated, as in the identification unit 13. Therefore, the recognition operation generating unit 14a changes the range in which the spindle rotational speed or the feed speed is changed, and thereby corrects the recognition operation so that chatter vibration occurs during the recognition operation. Specifically, the recognition operation generating unit 14a generates a recognition operation command pattern in which at least 1 of the maximum value S1, the minimum value S2, and the maximum value F1 and the minimum value F2 of the spindle rotation speed is changed in a predetermined ratio. Specifically, for example, at least 1 of the maximum value S1, the minimum value S2, and the maximum value F1 and the minimum value F2 of the spindle rotation speed are changed so that the range of the change set by the previous recognition operation becomes a different range with respect to at least 1 of the spindle rotation speed and the feed speed.
An example of the operation of the numerical control apparatus 1a according to embodiment 2 described above will be described with reference to fig. 14. Fig. 14 is a flowchart showing an example of the operation of the numerical control device 1a according to embodiment 2. In step S21, the numerical control device 1a starts the recognition operation. In the first step S21, the recognition operation generating unit 14a generates a first recognition operation command, and the drive control unit 15 outputs a control signal to the machine tool so that the machine tool executes an operation specified by the recognition operation command.
In steps S22 to S25, the same processing as in steps S12 to S15 of fig. 11 described in embodiment 1 is performed. In step S26, the identification unit 13a determines whether or not a parameter of a predetermined identification target is identified, and if the identification is completed (Yes in step S26), the process proceeds to step S28. If there is a parameter that is not recognized among the parameters of the predetermined recognition target (step S26 No), the numerical control device 1a corrects the recognition operation instruction in step S27, and repeats the processing from step S21. Specifically, in step S27, the identification unit 13a outputs an identification operation correction signal to the identification operation generation unit 14a, corrects the identification operation command so that the identification operation generation unit 14a changes at least 1 of the ranges of change in the spindle rotation speed and the feed speed, and outputs the corrected identification operation command to the drive control unit 15. In step S21 after the 2 nd time, a control signal is generated for the work machine 2 based on the recognition operation command corrected by the drive control unit 15, and output to the work machine 2.
In step S28, the numerical control device 1a corrects the operation of the work machine 2 based on the identification result. Specifically, the correction unit 11 generates a correction signal based on the identification result calculated by the identification unit 13a and outputs the correction signal to the drive control unit 15, similarly to the correction unit 11 of embodiment 1, after the identification operation is completed. The drive control unit 15 generates a control signal based on the machining path, the reference spindle rotational speed and the reference feed speed in the machining path, and the correction signal, and outputs the control signal to the machine tool 2.
The numerical control device 1a repeatedly executes a series of processes from step S21 to step S27 during processing. That is, after the identification is performed using the identification data for the period corresponding to the identification operation command, if there is an incomplete identification parameter among the identification target parameters, which are parameters set as the identification target, the identification unit 13a generates an identification operation correction signal indicating the change of the identification operation, and outputs the identification operation correction signal to the identification operation generation unit 14a. When the recognition operation generating unit 14a receives the recognition operation correction signal, it changes the recognition operation command, and the data acquiring unit 16 synchronizes a control signal generated based on the changed recognition operation command with an operation state signal indicating an operation state of the work machine 2 operated based on the control signal, and outputs the synchronized result as recognition data to the vibration determining unit 12 and the recognizing unit 13 a. These operations are repeated until the identification of all the parameters set as the identification targets is completed. This enables identification of all the dynamic characteristic parameters and the machining characteristic parameters set as the identification targets. Further, the processing in step S28 can improve the processing state by using the identification result. In the above description, the processing flow is described in the case where the recognition operation command is corrected after the completion of one recognition operation, but the processing flow may be the processing flow in which the recognition operation is corrected in the middle of the recognition operation.
As described above, the numerical control device 1a according to embodiment 2 corrects the recognition operation and performs the recognition operation again when there is a parameter that is not recognized completely among the parameters to be recognized that are determined in advance. Therefore, when there are parameters that cannot be recognized in the command pattern of the first recognition operation, the numerical control device 1a according to embodiment 2 corrects the recognition operation to generate chatter, and thus has an effect of recognizing all of the parameters to be recognized that are specified in advance.
Embodiment 3.
Fig. 15 is a block diagram showing a configuration example of a numerical control device according to embodiment 3 of the present invention. In embodiment 2, the identification operation is repeated until all the identification of the parameters of the identification target set in advance is completed. In embodiment 3, an example will be described in which parameters to be identified can be set from the outside. Hereinafter, the same reference numerals are used for the constituent elements having the same functions as those of embodiment 2, and overlapping description is omitted. The following description focuses on differences from embodiment 2.
As shown in fig. 15, the numerical control device 1b of embodiment 3 adds an input unit 17 to the numerical control device 1a of embodiment 2. The input unit 17 can receive input of parameters of the identification object from the outside. The input unit 17 receives at least 1 input of a dynamic characteristic parameter and a machining characteristic parameter as parameters to be identified, for example, from an external device, an operator, or the like. The input unit 17 may be a communication circuit for communicating with an external device, an interface circuit for reading data from an external medium, or an input unit such as a keyboard or a mouse. When receiving an input from an operator, the input unit 17 also uses a display unit such as a display or a monitor as the input unit 17. The parameters to be identified may be input to the input unit 17 as a numerical control program, or may be input to the input unit 17 by the operator in a dialogue. The input unit 17 may receive input of the parameter of the identification object in the form of dialogue programming. The input unit 17 outputs the received parameter of the identification object to the identification unit 13 a. As the parameters of the recognition object, for example, "case 1 where it is desired to remove the parameters that have been recognized by other means from the recognition object" (case 2) and "case 2 where it is desired to reduce the time taken for recognition by recognizing only the recognition object with a high priority" are considered as cases where the parameters of the recognition object are specified by the operator or from the outside. Therefore, if the 1 st situation is assumed, for example, in the menu list, the identification completion parameters are displayed so that the identification completion parameters can be distinguished by inputting values obtained by past identification in advance, and the identification of the unrecognized parameters is facilitated. In the case 2, it is assumed that the parameter to be identified can be selected by a selection frame or the like, and a display window for identifying the expected time change is provided each time a hook is input to the selection frame, so that the operator can select the largest parameter within the range in which the identification time is within the identification allowable time. The form of the dialogue programming is not limited to these examples, and any form may be used, but as described above, information to be considered by the operator for selection is displayed, whereby the operator can easily select the parameters of the recognition object.
The identification unit 13a performs the same operation as in embodiment 2 by using the parameter of the identification object input from the input unit 17 instead of the parameter of the identification object set in advance, similarly to the identification unit 13a in embodiment 2. The identification unit 13a may be capable of executing both an operation using the parameter of the identification object set in advance and an operation using the parameter of the identification object input from the input unit 17. The identification unit 13a outputs the result of the identification process to the correction unit 11. The operation of the correction unit 11 is the same as that of embodiment 1. The operation of the correction unit 11 when specifying the parameter to be identified according to the numerical control program is as follows. In the numerical control program, information such as a machining path, a spindle rotation speed, a feed speed, and a tool number is generally described. When an operator designates a parameter to be identified from a numerical control program, the numerical control program designates a machining path for performing an identification operation and the parameter to be identified. When the identification by the identification unit 13a is completed, for example, the correction unit 11 continuously generates a correction signal such that the vibration amplitude of the tool edge is equal to or smaller than a predetermined value from the timing when the tool number is changed to the timing when the machining path in which another identification operation is set is machined. The operation of the numerical control device 1b according to embodiment 3 other than the above is the same as that of the numerical control device 1a according to embodiment 2.
As described above, the numerical control device 1b according to embodiment 3 corrects the recognition operation and performs the recognition operation again when there is a parameter that is not recognized completely among the parameters of the recognition target set by the input from the outside. Therefore, the same effects as those of embodiment 2 are obtained, and the parameters of the identification object can be changed in accordance with the wishes of the operator or the like.
Embodiment 4.
Fig. 16 is a block diagram showing a configuration example of a numerical control device according to embodiment 4 of the present invention. In embodiment 3, a configuration is described in which parameters of an object to be identified can be set from the outside. In embodiment 4, a configuration in which a command pattern for identifying an operation can be set by an input from the outside will be described further. Hereinafter, the same reference numerals are used for the constituent elements having the same functions as those of embodiment 3, and overlapping description is omitted. The following description focuses on differences from embodiment 3.
As shown in fig. 16, the numerical control device 1c is the same as the numerical control device 1b of embodiment 3 except that it has an identification operation generating unit 14b and an input unit 17a instead of the identification operation generating unit 14a and the input unit 17.
The input unit 17a can receive the parameter of the identification object from the outside and output the received parameter of the identification object to the identification unit 13a, similarly to the input unit 17 of embodiment 3. The input unit 17a can receive input of command pattern information for determining a command pattern for recognizing an operation from the outside. The input unit 17a outputs the received command pattern information to the recognition operation generating unit 14 b. The command pattern information is information indicating, for example, spindle speeds S0 and S1, feed speeds F0 and F1, and time constants T1 and T2 in fig. 2 to 4. That is, the command pattern information is information indicating waveforms corresponding to the times of the spindle rotation speed and the feed speed when the spindle rotation speed and the feed speed are changed by recognizing the operation command. The command pattern information is input to the input unit 17a as a numerical control program or through a dialogue, for example. In addition, instruction pattern information may be input in the form of conversational programming. The command pattern information may be configured such that the waveform shown in fig. 2 to 4 or information indicating the waveform can be set from the outside.
The input unit 17a may be a communication circuit for communicating with an external device, an interface circuit for reading data from an external medium, or an input unit such as a keyboard or a mouse, as in the input unit 17. When receiving an input from an operator, the input unit 17a also uses a display unit such as a display or a monitor as the input unit 17a. The parameter and command pattern information of the identification object may be input to the input unit 17a from an external device in the form of a numerical control program, or may be input to the input unit 17a by an operator in the form of a dialogue. The input unit 17a may create a program in the form of a dialogue program, and specify parameters and command pattern information of the identification object by the program. The input unit 17a outputs the received parameter of the object to be identified to the identification unit 13a, and outputs the received instruction pattern information to the identification operation generation unit 14 b. The operation of the identification unit 13a and the correction unit 11 is the same as that of embodiment 3.
The recognition operation generating unit 14b generates a recognition operation command pattern based on the recognition operation command pattern information received by the input unit 17a, and outputs a recognition operation command to the drive control unit 15. The recognition operation generating unit 14b corrects the command pattern of the recognition operation based on the recognition operation correction signal output from the recognizing unit 13a, similarly to the recognition operation generating unit 14a of embodiment 2. The operation of the numerical control device 1c of the present embodiment other than the above is the same as that of the numerical control device 1b of embodiment 3.
As described above, the numerical control device 1c according to embodiment 4 can set the command pattern for the recognition operation by an input from the outside in addition to the parameters of the recognition target described in embodiment 3. Therefore, the numerical control device 1c according to embodiment 4 has an effect that the recognition result can be calculated preferentially over the combination of parameters specified by the input from the outside.
The configuration shown in the above embodiment shows an example of the content of the present invention, and other known techniques may be combined, and a part of the configuration may be omitted or changed without departing from the scope of the present invention.
Description of the reference numerals
1. 1a, 1b, 1c numerical control device, 2 working machine, 11 correction unit, 12 vibration determination unit, 13 identification unit, 14 identification action generation unit, 15 drive control unit, 16 data acquisition unit, 17a input unit.

Claims (8)

1. A numerical control device for controlling the operation of a machine tool having a main shaft and a feed shaft and processing a workpiece by a tool,
the numerical control device is characterized by comprising:
an identification operation generation unit that generates an identification operation command that causes the rotational speed and the feed speed of the spindle to be changed independently and continuously;
a data acquisition unit that synchronizes a control signal for controlling the work machine, which is generated based on the identification operation command, with an operation state signal indicating an operation state of the work machine, which is operated based on the control signal, and outputs the synchronized signal as identification data;
a vibration determination unit that determines, based on the identification data, whether the vibration state of the machine tool is stable machining, chatter vibration, or forced vibration; and
and an identification unit that selects, as a selection parameter, a distinguishable processing characteristic parameter among processing characteristic parameters representing characteristics of a processing phenomenon between the tool and the workpiece, based on a result of the determination by the vibration determination unit, and performs identification of the selection parameter using the identification data.
2. The numerical control device according to claim 1, wherein,
the identification unit selects, as the selection parameter, a dynamic characteristic parameter that can be identified among dynamic characteristic parameters representing characteristics of vibration of the machine tool, based on a result of the determination by the vibration determination unit.
3. The numerical control device according to claim 1 or 2, characterized in that,
the identification unit generates an instruction change signal for instructing a change of the identification operation when there is an incomplete identification parameter among identification target parameters, which are parameters set as identification targets, after the identification is performed using the identification data in a period corresponding to the identification operation instruction, and outputs the instruction change signal to the identification operation generation unit,
the recognition operation generating unit changes the recognition operation command if receiving the command change signal,
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 work machine operated based on the control signal, and outputs the control signal to the vibration determination unit and the identification unit as the identification data.
4. The numerical control device according to claim 3, wherein,
an input unit for receiving an input of the identification target parameter from the outside.
5. The numerical control device according to claim 4, wherein,
the input unit receives, from the outside, command pattern information indicating waveforms corresponding to time of the rotational speed and the feeding speed when the rotational speed and the feeding speed are changed by the recognition operation command,
the recognition operation generating unit generates the recognition operation instruction based on the instruction pattern information.
6. The numerical control device according to claim 4 or 5, characterized in that,
the input unit receives an input from the outside as a numerical control program.
7. The numerical control device according to claim 4 or 5, characterized in that,
the input unit receives an input from the outside in the form of dialogue programming.
8. The numerical control device according to claim 1 or 2, characterized in that,
the machine tool comprises a correction unit that generates a correction signal for correcting the operation of the machine tool based on the identification result.
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