JP2023149799A - Numerical control device, and control method of numerical control device - Google Patents

Abstract

To provide a numerical control device capable of properly restricting vibration generated when driving machinery, and to provide a control method of the numerical control device.SOLUTION: A CPU of a numerical control device acquires an allowable value and a feed rate. The CPU determines an acceleration time (S203) by referring to a vibration area map stored in a storage device, on the basis of the acquired allowable value and feed rate L. The CPU determines a first time (S205) by referring to a Tsum-T1 table stored in the storage device, on the basis of the acceleration time determined by the CPU. The CPU creates an acceleration command on the basis of the determined first time.SELECTED DRAWING: Figure 12

Description

The present invention relates to a numerical control device and a method of controlling the numerical control device.

Patent Document 1 discloses a vibration suppression device. The vibration suppression device adds a compensation torque command to the feed axis command in order to suppress vibrations that occur when the machine tool is driven in accordance with the feed axis command. The compensation torque command has a waveform having a phase opposite to that of the vibration. At this time, the amplitude of vibration is reduced by the compensation torque command, so that the machine tool can suppress vibration.

JP2019-153085A

The frequency of vibration that occurs when a machine tool is driven in response to a feed axis command may change depending on the conditions of the feed axis command. At this time, the method using a compensation torque command as in Patent Document 1 may not be able to suppress vibrations that occur during driving.

An object of the present invention is to provide a numerical control device and a control method for the numerical control device that can appropriately suppress vibrations generated when a mechanical device is driven.

A numerical control device according to a first aspect of the present invention is a numerical control device that drives a mechanical device by driving a motor based on an acceleration command, wherein the acceleration command is a continuous first period, a second period, and a second period. The acceleration of the motor is controlled over three periods and a fourth period, and in the first period, the acceleration of the motor increases from zero to the first acceleration, and in the second period, the acceleration of the motor increases to the first acceleration. In the third period, the acceleration of the motor decreases from zero to a second acceleration, and in the fourth period, the acceleration of the motor increases from the second acceleration to zero, and in the fourth period, the acceleration of the motor increases from the second acceleration to zero. A first time that is the length of one period, a second time that is the length of the second period, a third time that is the length of the third period, and a fourth time that is the length of the fourth period. The first time and the fourth time are the same, the second time and the third time are the same, and the permissible value of the vibration magnitude of the mechanical device and the mechanical device are the same. first information indicating the relationship between the feed amount and the total time of the first time, the second time, the third time, and the fourth time; and the relationship between the total time and the first time. a storage unit that stores second information indicating the second information; an acquisition unit that acquires the allowable value and the feed amount; a first determining means that determines the total time with reference to the first information; and with reference to the second information stored in the storage unit based on the total time specified by the first determining means; The apparatus is characterized by comprising a second determining means for determining the first time, and a creating means for creating the acceleration command based on the first time determined by the second determining means.

By driving the motor of the mechanical device using the determined acceleration command, the numerical control device can suppress vibrations of the mechanical device that occur when the motor is driven.

According to the first aspect, the first information is a measured value of the magnitude of the vibration that occurs for each combination of the total time and the feed amount when the total time and the feed amount are changed. The information may be defined based on the In the numerical control device, the first information is based on a measured value of vibration. Therefore, the numerical control device can create a more optimal acceleration command than when determined only by calculation.

According to the first aspect, the magnitude of the vibration of the mechanical device included in the first information is a vibration waveform representing the magnitude of the vibration generated in the mechanical device after completion of the acceleration command. It may be an integral value integrated over time. The numerical control device can create an optimal acceleration command by using the integral value of the vibration waveform.

According to the first aspect, the second information is information defined based on an equation that sets a specific frequency component of the acceleration command to 0 with respect to the total time, and the second determining means When there is a solution to the equation for the total time, the value that is the solution to the equation is determined as the first time, and when there is no solution to the equation, the value for the specific frequency component is determined as the first time. A value that minimizes the magnitude may be determined as the first time. Even when there is no solution to the equation, the numerical control device can create an optimal acceleration command by determining the value that minimizes the magnitude of a specific frequency component as the first time.

According to the first aspect, the second information is information defined based on an equation that sets a specific frequency component of the acceleration command to 0 with respect to the total time, and the second determining means If there are multiple solutions for the first time that minimize the magnitude of the specific frequency component with respect to the total time, the value closest to 1/2 of the total time is determined as the first time. You may. The numerical control device can create an optimal acceleration command by determining a value close to 1/2 of the total time for the first time.

According to the first aspect, the mechanical device has a plurality of natural frequencies, and the second information includes a weight defined by a weighting coefficient for the plurality of natural frequencies, and a weight specified by a weight coefficient for each of the acceleration commands. It may also be information applied to an equation in which the frequency component of is set to 0. Even when a mechanical device has multiple natural frequencies, the numerical control device can appropriately reduce vibration by applying weighting coefficients.

A control method for a numerical control device according to a second aspect of the present invention is a control method for a numerical control device that drives a mechanical device by driving a motor based on an acceleration command, wherein the acceleration command is a continuous first period. , the acceleration of the motor is controlled over a second period, a third period, and a fourth period, and in the first period, the acceleration of the motor increases from zero to the first acceleration, and in the second period, the acceleration of the motor increases from zero to the first acceleration. The acceleration of the motor decreases from the first acceleration to zero, in the third period, the acceleration of the motor decreases from zero to a second acceleration, and in the fourth period, the acceleration of the motor decreases from the second acceleration to zero. a first time that is the length of the first period; a second time that is the length of the second period; a third time that is the length of the third period; and a third time that is the length of the fourth period. of the fourth time, the first time and the fourth time are the same, and the second time and the third time are the same, and the numerical control device controls the mechanical device. first information indicating a relationship between a permissible value of vibration magnitude, a feed amount of the mechanical device, and a total time of the first time, the second time, the third time, and the fourth time; and an acquisition step that stores second information indicating a relationship between the total time and the first time; an acquisition step that acquires the tolerance value and the feed amount; and the tolerance value acquired in the acquisition step. a first determining step of determining the total time by referring to the first information stored in the storage unit based on the feed amount, and determining the total time based on the total time specified in the first determining step; a second determining step of determining the first time with reference to the second information stored in the unit; and a creating step of creating the acceleration command based on the first time determined in the second determining step. It is characterized by having the following.

The numerical control device obtains the same effects as the first aspect by controlling by the above control method.

A perspective view of the machine tool 1. 3 is a block diagram showing the electrical configuration of a numerical control device 30 and a machine tool 1. FIG. Graph showing the position, speed waveform, and acceleration waveform of the tool 4. The figure which shows the frequency characteristic of amplitude Amplitude. A diagram showing frequency characteristics of compliance. The figure which shows the relationship between the first time _T1 and amplitude Amplitude when an amplitude map and acceleration/deceleration time Tsum are 0.06 sec. A diagram showing a Tsum-T1 table. A diagram showing a vibration area map. FIG. 3 is a diagram showing a feed amount Tsum table and a Tsum-T1 table. Flowchart of pre-processing. Flowchart of main processing. Flowchart of optimization processing.

Embodiments of the present invention will be described. In the following explanation, left and right, front and back, and up and down directions indicated by arrows in the drawings will be used. The left-right direction, front-back direction, and up-down direction of the machine tool 1 are the X-axis direction, Y-axis direction, and Z-axis direction of the machine tool 1, respectively. The machine tool 1 shown in FIG. 1 is a machine that rotates a tool 4 attached to a main shaft 9 and performs cutting on a workpiece 3 held on the upper surface of a table 13. A numerical control device 30 (see FIG. 2) controls the operation of the machine tool 1.

The structure of the machine tool 1 will be explained with reference to FIG. The machine tool 1 includes a base 2, a column 5, a spindle head 7, a spindle 9, a table device 10, a tool changer 20, a control box 6, an operation panel 15 (see FIG. 2), and an acceleration sensor 18 (see FIG. 2). Equipped with etc. The base 2 is a substantially rectangular parallelepiped base made of metal. The column 5 is fixed to the upper rear part of the base 2. The spindle head 7 is provided so as to be movable in the Z-axis direction along the front surface of the column 5. The spindle head 7 rotatably supports the spindle 9 therein. The main shaft 9 has a mounting hole (not shown) at the bottom. The tool 4 is mounted in the mounting hole of the main shaft 9, and the main shaft 9 is rotated by the drive of a main shaft motor 52 (see FIG. 2). The spindle motor 52 is provided on the spindle head 7. The spindle head 7 is moved in the Z-axis direction by a Z-axis moving mechanism (not shown) provided on the front surface of the column 5. The numerical control device 30 controls the drive of the Z-axis motor 51 (see FIG. 2) to control the movement of the spindle head 7 in the Z-axis direction.

The table device 10 includes a Y-axis moving mechanism (not shown), a Y-axis table 12, an X-axis moving mechanism (not shown), a table 13, and the like. The Y-axis moving mechanism is provided on the front side of the upper surface of the base 2, and includes a pair of Y-axis rails, a Y-axis ball screw, a Y-axis motor 54 (see FIG. 2), and the like. The Y-axis rail and Y-axis ball screw extend in the Y-axis direction. The Y-axis rail guides the Y-axis table 12 in the Y-axis direction on the upper surface. The Y-axis table 12 is formed into a substantially rectangular parallelepiped shape and includes a nut (not shown) at the bottom. The nut threads onto the Y-axis ball screw. When the Y-axis motor 54 rotates the Y-axis ball screw, the Y-axis table 12 moves along the Y-axis rail together with the nut. Therefore, the Y-axis moving mechanism supports the Y-axis table 12 so as to be movable in the Y-axis direction.

The X-axis moving mechanism is provided on the upper surface of the Y-axis table 12, and includes a pair of X-axis rails (not shown), an X-axis ball screw (not shown), an X-axis motor 53 (see FIG. 2), and the like. The X-axis rail and the X-axis ball screw extend in the X-axis direction. The table 13 is formed into a rectangular plate shape in plan view, and is provided on the upper surface of the Y-axis table 12. The table 13 includes a nut (not shown) at the bottom. The nut threads onto the X-axis ball screw. When the X-axis motor 53 rotates the X-axis ball screw, the table 13 moves along the pair of X-axis rails together with the nut. Therefore, the X-axis moving mechanism supports the table 13 so as to be movable in the X-axis direction. Therefore, the table 13 moves on the base 2 in the X-axis direction and the Y-axis direction by the Y-axis moving mechanism, the Y-axis table 12, and the X-axis moving mechanism.

The tool changer 20 is provided on the front side of the spindle head 7, and includes a disk-shaped tool magazine 21. The tool magazine 21 holds a plurality of tools (not shown) radially around its outer periphery. The tool changer 20 drives the tool magazine 21 by the magazine motor 55 (see FIG. 2), and positions the tool specified by the tool change command at the tool change position. The tool change command is given by the NC program. The tool exchange position is the lowest position of the tool magazine 21. The tool changer 20 exchanges the tool 4 attached to the spindle 9 and the tool attached to the tool magazine 21 by a series of operations of raising the spindle head 7, rotating the tool magazine 21, and lowering the spindle head 7.

The control box 6 stores a numerical control device 30 (see FIG. 2). The numerical control device 30 controls the Z-axis motor 51, the spindle motor 52, the X-axis motor 53, and the Y-axis motor 54 (see FIG. 2) provided in the machine tool 1, respectively, and controls the workpiece 3 held on the table 13. The tool 4 mounted on the spindle 9 is moved relative to the main shaft 9 to perform various types of machining on the workpiece 3. Various types of processing include drilling using a drill, tap, etc., and side processing using an end mill, milling cutter, etc.

The operation panel 15 (see FIG. 2) is provided, for example, on the outer wall of a cover (not shown) that covers the machine tool 1. The operation panel 15 includes an input section 16 and a display section 17 (see FIG. 2). The input unit 16 receives inputs such as various information and operation instructions, and outputs them to the numerical control device 30. The display unit 17 displays various screens based on commands from the numerical control device 30. The acceleration sensor 18 (see FIG. 2) is provided on the main shaft 9 of the machine tool 1 and measures vibrations generated in the main shaft 9.

With reference to FIG. 2, the electrical configuration of the numerical control device 30 and the machine tool 1 will be explained. The numerical control device 30 and the machine tool 1 include a CPU 31, a ROM 32, a RAM 33, a storage device 34, an input/output section 35, drive circuits 51A to 55A, an acceleration sensor 18, and the like. The CPU 31 centrally controls the numerical control device 30. The ROM 32 stores a pre-processing program, a main program, and the like. The preprocessing program is a program for executing preprocessing (see FIG. 10). The main program is a program for executing main processing (see FIG. 11). Preprocessing is executed before main processing. The main processing reads the NC program line by line and executes various operations. The NC program is composed of multiple lines including various control commands, and the control commands include axis movement of the machine tool 1, tool exchange, etc. Note that the axis movement is a command for controlling the rotational position of the Z-axis motor 51 and the like using the feed amount L. The CPU 31 creates an acceleration command, which will be described later, from the feed amount L.

The RAM 33 temporarily stores various information. The storage device 34 is non-volatile and stores NC programs and various information. The CPU 31 can store in the storage device 34, in addition to the NC program inputted by the operator through the input section 16 of the operation panel 15, the NC program read through external input.

The drive circuit 51A is connected to the Z-axis motor 51 and encoder 51B. Drive circuit 52A is connected to main shaft motor 52 and encoder 52B. Drive circuit 53A is connected to X-axis motor 53 and encoder 53B. Drive circuit 54A is connected to Y-axis motor 54 and encoder 54B. Drive circuit 55A is connected to magazine motor 55 and encoder 55B. The Z-axis motor 51, the main shaft motor 52, the X-axis motor 53, the Y-axis motor 54, and the magazine motor 55 are all servo motors (hereinafter, when collectively referred to, they will simply be referred to as the motors 50). The drive circuits 51A to 55A receive commands from the CPU 31 and output drive currents to the corresponding motors 51 to 55, respectively. Drive circuits 51A to 55A receive feedback signals from encoders 51B to 55B and perform feedback control of position and velocity. The input/output section 35 is connected to the input section 16 and display section 17 of the operation panel 15, and the acceleration sensor 18, respectively.

The case where the machine tool 1 is driven based on the commands of the NC program (hereinafter referred to as feed axis commands) to move the tool 4 relative to the workpiece 3 in the X-axis direction, Y-axis direction, and Z-axis direction, respectively. Illustrate. Hereinafter, a case in which the tool 4 is moved downward along the Z-axis direction with respect to the workpiece 3 will be described as an example. Although detailed explanation will be omitted, the same applies when processing the workpiece 3 by moving the tool 4 in the X-axis direction and the Y-axis direction. The vertical axis of the graph shown in FIG. 3 indicates the position in the Z-axis direction (FIG. 3(A)), velocity (FIGS. 3(B) and (C)), and acceleration (FIG. 3(D)). Hereinafter, in order to simplify the explanation, the downward direction in FIGS. 3A to 3D will be described as positive and the upward direction as negative. In FIG. 3(A), the Z-axis coordinate indicating the position of the tool 4 at a predetermined reference position is indicated by zero. The Z-axis coordinate indicating the position of the tool 4 below the reference position is shown as a positive value. In FIGS. 3(B) to 3(D), the speed and acceleration when the tool 4 moves downward are shown as positive values.

When the CPU 31 reads the feed axis command of the NC program, it generates time series data of the target position of the spindle head 7 in order to move the spindle head 7 holding the spindle 9 to the position designated by the feed axis command. The CPU 31 outputs target position data to the drive circuit 51A at predetermined intervals. The drive circuit 51A drives the Z-axis motor 51 based on the target position data output by the CPU 31. The Z-axis motor 51 moves the tool 4 in the Z-axis direction via the spindle head 7 to a target position. Each time the CPU 31 inputs target position data to the drive circuit 51A, the drive circuit 51A drives the Z-axis motor 51. As a result, the tool 4 finally reaches the position specified by the feed axis command (hereinafter referred to as the command position) (see FIG. 3(A)). The above control executed by the CPU 31 based on the feed axis command is referred to as feed axis control.

When generating the time-series data of the target positions in the above, the CPU 31 determines each target position so that the speed when the tool 4 moves in the Z-axis direction to the command position remains constant (see FIG. 3(B) reference). Next, the CPU 31 adjusts the acceleration/deceleration characteristics corresponding to the rising and falling characteristics of the waveform (hereinafter referred to as speed waveform) indicating a time-series change in speed. FIGS. 3C and 3D show velocity waveforms and acceleration waveforms when the target position is short and does not have a constant speed section. This patent deals with the calculation of acceleration commands in the case where there is no constant speed section (=section where acceleration is 0). Hereinafter, the process of adjusting the acceleration/deceleration characteristics of the speed waveform will be referred to as acceleration/deceleration processing. The rising and falling slopes of the velocity waveform obtained by performing the acceleration/deceleration processing correspond to the acceleration of the tool 4.

The CPU 31 determines a target position for each predetermined period based on the speed waveform after performing acceleration/deceleration processing. The CPU 31 outputs data on the determined target position to the drive circuit 51A at predetermined intervals. At this time, as shown in FIG. 3C, the tool 4 moved by the Z-axis motor 51 driven by the drive circuit 51A accelerates during an acceleration period Pa at the start of movement, and decelerates during a deceleration period Pd at the end of movement. Hereinafter, the length of the acceleration period Pa will be referred to as acceleration time Ta, and the length of deceleration period Pd will be referred to as deceleration time Td.

Hereinafter, the control command that the CPU 31 outputs to the drive circuit 50A based on the feed axis command of the NC program will be referred to as an acceleration command. The acceleration command is a concept that includes an acceleration command to accelerate the tool 4 and a deceleration command to decelerate the tool 4. FIG. 3(D) shows a time-series change in acceleration (hereinafter referred to as an acceleration waveform) when the tool 4 moves in response to an acceleration command. The period during which the acceleration of the tool 4 increases in the acceleration period Pa is referred to as a first period _P1 , and the length of the first period _P1 is referred to as a first time _T1 . In the first period _P1 , the acceleration of the motor 50 increases from zero to a first acceleration _A1 . A period in which the acceleration of the tool 4 decreases in the acceleration period Pa is referred to as a second period _P2 , and the length of the second period _P2 is referred to as a second time _T2 . In the second period _P2 , the acceleration of the motor 50 decreases from the first acceleration _A1 to zero. The period during which the acceleration of the tool 4 decreases during the deceleration period Pd is referred to as a third period _P3 , and the length of the third period _P3 is referred to as a third time _T3 . In the third period _P3 , the acceleration of the motor 50 decreases from zero to a second acceleration _A2 . The period during which the acceleration of the tool 4 increases during the deceleration period Pd is referred to as a fourth period _P4 , and the length of the fourth period _P4 is referred to as a fourth time _T4 . In the fourth period _P4 , the acceleration of the motor 50 increases from the second acceleration _A2 to zero.

The acceleration command controls the acceleration of the motor 50 over a continuous first period P ₁ to a fourth period P ₄ . The length from the start of the first period _P1 to the end of the fourth period _P4 is referred to as acceleration/deceleration time Tsum. The first time T ₁ to the fourth time T ₄ are collectively referred to as acceleration/deceleration time constant Tα. It is assumed that the acceleration command satisfies T ₁ =T ₄ and T ₂ =T ₃ , and that the first time T ₁ and acceleration/deceleration time Tsum satisfy 0<T1<Tsum/2.

As already stated, this patent assumes that the acceleration waveform does not include a period in which the acceleration is zero, as shown in FIG. 3(D).

With reference to FIG. 4, the natural frequency ωn/2π of the machine tool 1 will be explained. The natural frequency ωn/2π is a unique resonance frequency that the machine tool 1 has. n is a natural number. In order to specify the natural frequency ωn/2π of the machine tool 1, the operator impulse-vibrates the main shaft 9 of the machine tool 1, for example, in the Z-axis direction using an impulse hammer. At this time, the acceleration sensor 18 detects the vibration waveform of amplitude Amplitude in the Z-axis direction generated in the main shaft 9. The CPU 31 subjects the vibration waveform detected by the acceleration sensor 18 to Fourier transformation. As a result, the frequency characteristic of the amplitude Amplitude shown in FIG. 4 is obtained. In the frequency characteristic of the amplitude Amplitude shown in FIG. 4, peaks of the amplitude Amplitude occur at positions of 30 Hz and 50 Hz. In this case, the natural frequencies ω ₁ /2π and ω ₂ /2π of the machine tool 1 can be specified as 30 Hz and 50 Hz.

FIG. 5 is a compliance value obtained by dividing the frequency characteristic of the amplitude Amplitude shown in FIG. 4 by the excitation force measured with an impulse hammer, and represents the ease with which the machine vibrates at each frequency. With reference to FIG. 5, a method for obtaining weighting coefficients Q and R when there are two natural frequencies ωn/2π will be described. The weighting coefficients Q and R are used in equation (1-1) described later. As shown in FIG. 5, the compliance when the natural frequency ω ₁ /2π is 30 Hz is 0.1142 mm/N. The compliance when the natural frequency ω ₂ /2π is 50 Hz is 0.6263 mm/N. The ratio of the natural frequencies ω ₁ /2π and ω ₂ /2π to the compliance is 30 Hz compliance: 50 Hz compliance = 0.1142:0.6263. When adjusted so that the sum of the respective ratios is 1, the ratio becomes 30 Hz compliance: 50 Hz compliance=0.15:0.85. Therefore, the weighting coefficient Q in the case of 30 Hz is determined to be 0.15. The weighting coefficient R in the case of 50 Hz is determined to be 0.85.

A method for creating an amplitude map when there are a plurality of natural frequencies will be described with reference to FIG. 6. The amplitude map shows the magnitude of the amplitude Amplitude when the horizontal axis is the first time T ₁ and the vertical axis is Tsum. The following equation (1-1) is used to create the amplitude map. Equation (1-1) below indicates the amplitude Amplitude of the natural vibration component of the machine tool 1 included in the acceleration command. The magnitude of the natural vibration generated in the machine tool 1 is determined by the amplitude Amplitude. Further, a indicates the ratio between the first time _T1 and the second time _T2 . Here, it is assumed that the natural frequency ω ₁ /2π is 30 Hz, the natural frequency ω ₂ /2π is 50 Hz, the weighting coefficient Q is 0.15, and the weighting coefficient R is 0.85.

The first term in equation (1-1) corresponds to the case where the natural frequency ω ₁ /2π is 30 Hz. The angular frequency ω ₁ is 2·π·30. The feed amount L is a constant. Here, the first time T ₁ and acceleration/deceleration time Tsum are used as variables, and are substituted into the first term of equation (1-1) for each pair of first time T ₁ and acceleration/deceleration time Tsum. As a result, the amplitude Amplitude is obtained for each group. Thereby, the CPU 31 obtains the amplitude map (30 Hz) shown in FIG. 6(A).

The second term in equation (1-1) corresponds to the case where the natural frequency ω ₂ /2π is 50 Hz. The angular frequency ω ₂ is 2·π·50. The feed amount L is a constant. Here, the CPU 31 uses the first time T ₁ and the acceleration/deceleration time Tsum as variables, and substitutes them into the second term of equation (1-1) for each set of the first time T ₁ and the acceleration/deceleration time Tsum. Thereby, the CPU 31 obtains the amplitude Amplitude for each group. Thereby, the CPU 31 obtains the amplitude map (50 Hz) shown in FIG. 6(B).

In creating the amplitude map (30Hz+50Hz), the CPU 31 uses the first time _T1 and the acceleration/deceleration time Tsum as variables, and for each pair of the first time _T1 and the acceleration/deceleration time Tsum, the first and the second term. The CPU 31 multiplies the calculated amplitude Amplitude for each set by the weighting coefficients Q and R. The weighting coefficient Q is 0.15, and the weighting coefficient R is 0.85. As a result, the amplitude Amplitude is obtained for each group. Thereby, the CPU 31 obtains the amplitude map (30Hz+50Hz) shown in FIG. 6(C). Note that the amplitude map (30Hz+50Hz) corresponds to the sum of the amplitude map (50Hz) and the amplitude map (30Hz).

The graph shown in FIG. 6(D) is a graph obtained by extracting the amplitude Amplitude when the acceleration/deceleration time Tsum is 0.06 sec from the amplitude map (30 Hz). The vertical axis is the amplitude Amplitude, and the horizontal axis is the first time _T1 . The graph shown in FIG. 6(E) is a graph obtained by extracting the amplitude Amplitude when the acceleration/deceleration time Tsum is 0.06 sec from the amplitude map (50 Hz). The graph shown in FIG. 6(F) is a graph obtained by extracting the amplitude Amplitude when the acceleration/deceleration time Tsum is 0.06 sec from the amplitude map (30Hz+50Hz). In addition. The graph shown in FIG. 6(F) corresponds to the result of adding the graph in FIG. 6(D) and the graph in FIG. 6(E).

In this case, the first time _T1 at which the amplitude Amplitude is minimum is 0.011 sec (see FIG. 6(F)). For example, when the acceleration/deceleration time Tsum of the acceleration command is 0.06 sec, the CPU 31 determines the first time _T1 to be 0.011 sec. As a result, the amplitude Amplitude generated in the machine tool 1 is minimized. Note that the first time T ₁ at which the amplitude Amplitude is the minimum can be calculated by solving the equation for the first time T ₁ in which the amplitude Amplitude of equation (1-1) is set to 0.

The Tsum-T1 table will be explained with reference to FIG. The Tsum-T1 table shows the relationship between the acceleration/deceleration time Tsum and the first time _T1 . For example, when the acceleration _/ deceleration time Tsum is varied from 0 to 0.1 based on the relationship of the amplitude map (30Hz+50Hz) in FIG. Obtain data indicating the relationship between Amplitude and Amplitude. The graph in FIG. 6(F) is a graph of data showing the relationship between the first time _T1 and the amplitude Amplitude when the acceleration/deceleration time Tsum is 0.06 seconds.

The CPU 31 determines the first time T ₁ at which the amplitude Amplitude becomes the minimum based on the relationship between the first time T ₁ and the amplitude Amplitude acquired for each variable acceleration/deceleration time Tsum. In addition, in the graph of FIG. 6(F), when the acceleration/deceleration time Tsum is 0.06 sec, the first time _T1 at which the amplitude Amplitude is the minimum is 0.011 sec.

Here, the minimum value of the amplitude Amplitude corresponds to the solution at the first time T ₁ of the equation with the amplitude Amplitude set to 0 for equation (1-1). That is, the CPU 31 can calculate the first time T ₁ at which the amplitude Amplitude is the minimum by solving the equation (1-1) with the amplitude Amplitude set to 0 for the first time T ₁ . Therefore, the CPU 31 can create the Tsum-T1 table by solving the equation (formula (1-1)=0) for the first time _T1 for each variable acceleration/deceleration time Tsum. In other words, the Tsum-T1 table is based on the equation (formula (1-1) =0).

Here, when a solution to the equation (formula (1-1)=0) exists for the acceleration/deceleration time Tsum, the CPU 31 selects the value that is the solution to the equation (formula (1-1)=0). One hour _T1 is determined. If there are multiple solutions to the first time T ₁ of the equation (formula (1-1)=0), the CPU 31 determines the value closest to 1/2 of the acceleration/deceleration time Tsum as the first time T ₁ . This is because when comparing the vibrations for a plurality of solutions, the maximum value of the acceleration command is the smallest at the first time _T1 , and the excitation force is also small. On the other hand, when there is no solution to the equation (formula (1-1) = 0), the value that minimizes the magnitude of the amplitude Amplitude is determined as the first time T ₁ based on the vibration map and the acceleration/deceleration time Tsum. . The CPU 31 stores the Tsum-T1 table in the storage device 34.

Note that when there is one natural frequency ωn/2π, for example, when there is one natural frequency ω ₁ /2π of 30 Hz, the CPU 31 substitutes Q=1 and Q=0 in equation (1-1), Execute the above calculation. Thereby, the CPU 31 can create an amplitude map and a Tsum-T1 table. Further, when the natural frequency ω ₂ /2π is one of 50 Hz, the CPU 31 substitutes Q=0 and R=1 into equation (1-1) and executes the above calculation. Thereby, the CPU 31 can create an amplitude map and a Tsum-T1 table. Further, the CPU 31 stores the Tsum-T1 table in the storage device 34 even when the natural frequency ωn/2π is one.

The vibration area map will be explained with reference to FIG. The vibration area map is information defined based on the measured value of the magnitude of vibration that occurs for each combination of acceleration/deceleration time Tsum and feed amount L when the acceleration/deceleration time Tsum and feed amount L are changed. . Note that the first time _T1 is determined based on the Tsum-T1 table.

In order to create a vibration area map, the operator executes a feed axis command for each pair of feed amount L and acceleration/deceleration time Tsum. As an example, the feed amount L is changed in 1 mm increments from 0 mm to 6 mm. The acceleration/deceleration time Tsum is changed from 0.05 sec to 0.1 sec in 0.01 sec increments. Shown below.

When the feed axis command is executed, the acceleration sensor 18 measures vibrations generated in the machine tool 1. The vibration measurement results are shown in Fig. 8(A) and the measured vibration waveform, for example, when the feed amount L is 4 mm, the acceleration/deceleration time Tsum is 0.07, and the first time _T1 is 0.0167. is shown in FIG. 8(B). The vibration waveform indicates the magnitude of vibration generated in the machine tool 1. After completing the acceleration command, the CPU 31 integrates the absolute value of the position displacement of the measured vibration waveform over a predetermined time t1. The predetermined time t1 is, for example, 0.3 seconds. Hereinafter, the integral value of the vibration waveform will be referred to as the vibration area. In other words, the magnitude of vibration of the machine tool 1 included in the vibration area map is an integral value obtained by integrating a vibration waveform indicating the magnitude of vibration generated in the machine tool 1 after completion of the acceleration command over a predetermined time t1. It is.

The operator executes a feed axis command for each pair of feed amount L and acceleration/deceleration time Tsum. The CPU 31 calculates the vibration area for each feed axis command. The CPU 31 plots the calculated vibration area in association with the combination of acceleration/deceleration time Tsum and feed amount L. Thereby, the CPU 31 obtains vibration area maps shown in FIGS. 8(C) and 8(D).

The CPU 31 performs two-dimensional linear interpolation on the vibration area maps shown in FIGS. 8(C) and 8(D). As a result, the interpolated vibration area maps shown in FIGS. 8(E) and 8(F) are obtained. The CPU 31 can acquire information on the vibration area regarding the pair of the feed amount L and the acceleration/deceleration time Tsum that have not been measured. The CPU 31 stores the interpolated vibration area map in the storage device 34.

Referring to FIG. 9, a case will be described in which the machine tool 1 is driven to machine the workpiece 3. When processing the workpiece 3, for example, the operator set the feed amount L of the feed axis command to 4 mm, and set the permissible vibration tolerance to 0.0003 mm. In this case, the CPU 31 refers to the interpolated vibration area map (see FIG. 8(F)) stored in the storage device 34 and creates a feed amount Tsum table (see FIG. 9(A)). The feed amount Tsum table is obtained by plotting a dashed-dotted line indicating the permissible value of vibration from the interpolated vibration area map (see FIG. 8(F)) stored in the storage device 34. In FIG. 9(A), the dashed-dotted line indicates the position where the tolerance is 0.0003 mm. Therefore, the feed amount Tsum table shown in FIG. 9(A) shows the relationship between the allowable value, the feed amount L, and the acceleration/deceleration time Tsum.

Here, when the feed amount L is 4 mm, the CPU 31 determines the shortest acceleration/deceleration time Tsum that satisfies the allowable value to be 0.065 sec based on the feed amount Tsum table (see FIG. 9(A)). The CPU 31 refers to the Tsum-T1 table and determines that the optimal first time _T1 when the acceleration/deceleration time Tsum is 0.065 sec is 0.0138 sec (see FIG. 9(B)).

In this case, the acceleration commands include acceleration/deceleration time Tsum of 0.065 sec, first time T ₁ of 0.0138 sec, second time T ₂ of 0.0187 sec, third time T ₃ of 0.0187 sec, and fourth time T ₄ is determined to be 0.0138 sec. By driving the machine tool 1 with the optimized acceleration command, the CPU 31 is able to drive at the fastest speed while suppressing vibrations below an allowable value.

Note that the Tsum-T1 table shown in FIG. 9(B) is for the case where the natural frequencies of the machine tool 1 are 30 Hz and 50 Hz. For example, when the natural frequency of the machine tool 1 is 30 Hz or 50 Hz, the first time _T1 for the optimal acceleration/deceleration time Tsum is determined by referring to the corresponding Tsum-T1 table.

The preprocessing will be explained with reference to FIG. 10. The preprocessing is executed before executing the main processing described below. The CPU 31 executes the preprocessing by reading and executing the preprocessing program stored in the storage device 34 . When the preprocessing is executed, the CPU 31 determines whether the natural frequency ωn/2π of the machine tool 1 has been obtained (S1). If it is determined that the natural frequency ωn/2π has not been acquired (S1: NO), the CPU 31 returns to the process and waits.

The operator applies impulse vibration to the main shaft 9 of the machine tool 1 using an impulse hammer. After performing the impulse vibration, the CPU 31 calculates the frequency characteristic (see FIG. 4) of the amplitude Amplitude and obtains the natural frequency ωn/2π. For example, the natural frequencies ω ₁ /2π and ω ₂ /2π are 30 Hz and 50 Hz, respectively (see FIG. 4).

If it is determined that the natural frequency ωn/2π has been obtained (S1: YES), the CPU 31 determines whether a plurality of natural frequencies ωn/2π exist (S3). If it is determined that a plurality of natural frequencies ωn/2π do not exist (S3: NO), the CPU 31 creates an amplitude map based on one natural frequency ωn/2π (S9). For example, when the natural frequency ωn/2π is 30 Hz, the CPU 31 creates a 30 Hz amplitude map. The CPU 31 advances the process to S11.

If it is determined that a plurality of natural frequencies ωn/2π exist (S3: YES), the CPU 31 determines weighting coefficients Q and R for each natural frequency ωn/2π (S5). For example, when the natural frequencies ω ₁ /2π and ω ₂ /2π are 30 Hz and 50 Hz, respectively (see FIG. 4), the CPU 31, for example, refers to the frequency characteristics of compliance (see FIG. 5) and calculates the weighting coefficient. Determine Q and R. The weighting coefficients Q and R are 0.15 and 0.85, respectively.

The CPU 31 creates an amplitude map using the determined weighting coefficients Q and R (S7). In this case, the CPU 31 creates, for example, an amplitude map (30Hz+50Hz) shown in FIG. 6(C). The CPU 31 advances the process to S11.

The CPU 31 creates a Tsum-T1 table based on the amplitude map created in the process of S7 or the process of S9 (S11). In this case, the CPU 31 creates, for example, the Tsum-T1 table shown in FIG. The CPU 31 stores the created Tsum-T1 table in the storage device 34.

Next, the operator determines whether the calculation of the vibration area corresponding to the combination of the feed amount L and the acceleration/deceleration time Tsum has been completed (S13). If it is determined that the calculation of the vibration area has not been completed (S13: NO), the CPU 31 returns the process and waits. The operator measures the vibration of the machine tool 1 by changing the feed axis command for each pair of feed amount L and acceleration/deceleration time Tsum. The CPU 31 calculates the vibration area based on the vibration waveform measured for each pair of feed amount L and acceleration/deceleration time Tsum.

If it is determined that the vibration area calculation has been completed (S13: YES), the CPU 31 creates a vibration area map based on the vibration area calculation result (S15). The CPU 31 creates vibration area maps shown in FIGS. 8(C) and 8(D), for example. Here, creating a vibration area map means obtaining the relationship between the integral value of the vibration waveform with respect to two variables, the feed amount L and the acceleration/deceleration time Tsum. The CPU 31 interpolates the vibration area map (S17). In this case, the CPU 31 creates vibration area maps shown in FIGS. 8(E) and 8(F), for example. The CPU 31 stores the interpolated vibration area map in the storage device 34. The CPU 31 ends the process.

The main processing will be explained with reference to FIG. The CPU 31 executes main processing by reading and executing the main program stored in the storage device 34 . When the main process is executed, the CPU 31 obtains a permissible vibration value from the setting parameters inputted in advance from the input unit 16 and stored in the storage device 34 (S101).

If it is determined that the permissible value of vibration has been obtained (S101: YES), the CPU 31 calculates the feed amount Tsum based on the vibration area map stored in the storage device 34 in advance processing and the permissible value of vibration obtained in the process of S101. A table is created (S103). The permissible value of vibration is, for example, 0.0003 mm. In this case, the CPU 31 creates, for example, a feed amount Tsum table shown in FIG. 9(A).

The CPU 31 determines whether or not the NC program name has been received from the input unit (S105). If it is determined that the NC program name has not been accepted (S105: NO), the CPU 31 returns to the process and waits. If it is determined that the NC program name has been accepted (S105: YES), the CPU 31 reads one line of the NC program from the NC program corresponding to the NC program name from the storage device 34 (S107). Although not shown here, it is assumed that the NC program is input in advance from the input unit 16 and stored in the storage device 34.

The CPU 31 determines whether the read one line of the NC program is a feed axis command (S109). If it is determined that the command is not a feed axis command (S109: NO), the CPU 31 executes the read command other than the feed axis command (S117). If it is not a feed axis command, it is, for example, a tool exchange command. The CPU 31 advances the process to S119.

On the other hand, if it is determined that it is a feed axis command (S109: YES), the CPU 31 executes the optimization process shown in FIG. 12 (S111). In the optimization process, acceleration/deceleration time Tsum and first time _T1 are optimized. When the optimization process is executed, the CPU 31 obtains the feed amount L included in the feed axis command (S201). Note that acquiring the feed amount L may mean acquiring a value input through the input unit 16 or a value set and stored in the storage device 34 in advance. The feed amount L is, for example, 4 mm.

The CPU 31 determines the acceleration/deceleration time Tsum (S203). In this case, the CPU 31 determines the acceleration/deceleration time Tsum corresponding to the feed amount L with reference to the feed amount Tsum table (see FIG. 9(A)) created in the process of S103. As shown in FIG. 9A, when the feed amount L is 4 mm, the optimal acceleration/deceleration time Tsum is 0.065 sec.

The CPU 31 determines the first time _T1 based on the acceleration/deceleration time Tsum determined in the process of S203 and the Tsum-T1 table (S205). Based on the determined acceleration/deceleration time Tsum, the CPU 31 refers to the Tsum-T1 table (FIG. 9(B)) stored in the storage device 34 and determines the first time _T1 . When the acceleration/deceleration time Tsum is 0.065 sec, the optimal first time _T1 is 0.0138 sec (see FIG. 9(B)). The CPU 31 returns the processing to the main processing.

The CPU 31 creates an acceleration command based on the first time _T1 and the acceleration/deceleration time Tsum determined in the optimization process (S113). In this case, the CPU 31 sets the acceleration/deceleration time Tsum to 0.065 sec, the first time T ₁ to 0.0138 sec, the second time T ₂ to 0.0187 sec, the third time T ₃ to 0.0187 sec, and the fourth time T 3 to 0.0187 sec. Create an acceleration command with _T4 set to 0.0138 sec.

The CPU 31 executes a feed axis command based on the created acceleration command. That is, based on the acceleration command, the target position is outputted at every predetermined period to the drive circuit 50A, and movement is performed by the feed amount L (S115). The CPU 31 determines whether the NC program is on the last line (S119). If it is determined that the NC program is not at the final line (S119: NO), the CPU 31 returns the process to S107. If it is determined that the NC program is at the last line (S119: YES), the CPU 31 ends the process.

As described above, the CPU 31 obtains the allowable value and the feed amount L. Based on the acquired allowable value and the feed amount L, the CPU 31 refers to the feed amount Tsum table and determines the acceleration/deceleration time Tsum. Based on the determined acceleration/deceleration time Tsum, the CPU 31 refers to the Tsum-T1 table and determines the first time _T1 . The CPU 31 creates an acceleration command based on the determined first time _T1 .

By driving the motor 50 of the machine tool 1 with the determined acceleration command, the numerical control device 30 can suppress vibrations of the machine tool 1 that occur when the motor 50 is driven.

The vibration area map is information defined based on the measured value of the magnitude of vibration that occurs for each combination of acceleration/deceleration time Tsum and feed amount L when the acceleration/deceleration time Tsum and feed amount L are changed. . In the numerical control device 30, the vibration area map is based on measured values of vibration. Therefore, the numerical control device 30 can create a more optimal acceleration command than when determined only by calculation.

The magnitude of vibration of the machine tool 1 included in the vibration area map is an integral value obtained by integrating a vibration waveform indicating the magnitude of vibration generated in the machine tool 1 after completion of the acceleration command over a predetermined time t1. . The numerical control device 30 can create an optimal acceleration command by using the integral value of the vibration waveform.

In the equation, when a solution to the equation exists for the acceleration/deceleration time Tsum, the CPU 31 determines the value that is the solution to the equation as the first time _T1 . When there is no solution to the equation, the CPU 31 determines the value that minimizes the magnitude of the specific frequency component as the first time _T1 . Even when there is no solution to the equation, the numerical control device 30 can create an optimal acceleration command by determining, for the first time _T1 , a value that minimizes the magnitude of a specific frequency component.

In the equation, if there are multiple solutions for the first time T1 that minimize the magnitude of a specific frequency component with respect to the acceleration/deceleration time Tsum, the CPU 31 selects the value closest to 1/2 of the acceleration/deceleration time Tsum as the first time. One hour _T1 is determined. The numerical control device 30 can create an optimal acceleration command by determining a value close to 1/2 of the acceleration/deceleration time Tsum as the first time _T1 .

The machine tool 1 has a plurality of natural frequencies ωn/2π. The Tsum-T1 table is information in which weights defined by weighting coefficients Q and R for a plurality of natural frequencies ωn/2π are applied to an equation in which a specific frequency component of each acceleration command is set to 0. Even when the machine tool 1 has a plurality of natural frequencies ωn/2π, the numerical control device 30 can appropriately reduce vibration by applying the weighting coefficients Q and R.

The present invention is not limited to the above embodiments, and various modifications are possible. Although the present invention reduces the vibration of the machine tool 1, the present invention is not limited to this, and the technique of the above embodiment may be applied to other mechanical devices. The preprocessing and main processing are not limited to being executed by the CPU 31 of the numerical control device 30, but may be executed by a PC or the like, for example. At this time, information indicating the acceleration waveform determined by executing preliminary processing and main processing using a PC or the like may be input to the numerical control device 30. The numerical control device 30 may control the motor 50 of the machine tool 1 using an acceleration command indicating the input acceleration waveform.

In the above embodiment, the case where the machine tool 1 has one or two natural frequencies has been described, but the invention is not limited to this. For example, the machine tool 1 may have three or more natural frequencies. In that case, a term corresponding to the natural frequency may be added to equation (1-1). Even in this case, the weighting coefficients can be obtained using the same method as in the above embodiment.

In the above embodiment, when the acceleration/deceleration time Tsum and the feed amount L are changed, a vibration area map representing the magnitude of vibration generated for each combination of the acceleration/deceleration time Tsum and the feed amount L is created by actual measurement. , which is an example of a vibration area map creation means. For example, the vibration area map may be created using a numerical simulation representing the vibration characteristics of the machine tool 1. Further, a function that inputs the acceleration/deceleration time Tsum and the feed amount L and outputs the magnitude of vibration may be used instead of the vibration area map.

In the above embodiment, the vibration area map is obtained by two-dimensional linear interpolation, but this is only one example of an interpolation method. For example, a vibration area map may be obtained by performing curved surface interpolation using NURBS (non-uniform rational B-spline) interpolation or the like.

In the above embodiment, when there are multiple solutions for the first time T1 in the equation, the value closest to 1/2 of the acceleration/deceleration time Tsum is determined as the first time _T1 , but the present invention is not limited thereto. For example, it may be set to 1/4 of the acceleration/deceleration time Tsum, or other values may be set.

In the embodiment described above, an equation is used to find the relationship between _T1 and the acceleration/deceleration time Tsum, but this is an example of a method for finding _T1 . For example, _T1 for the acceleration/deceleration time Tsum may be determined by using a function that approximates the Tsum-T1 table shown in FIG.

The machine tool 1 is an example of the "mechanical device" of the present invention. The acceleration/deceleration time Tsum is an example of the "total time" of the present invention. The feed amount Tsum table is an example of "first information" of the present invention. The Tsum-T1 table is an example of "second information" of the present invention. The storage device 34 is an example of the "storage unit" of the present invention. The processing in S101 and S201 is an example of the "acquisition means" of the present invention. The process of S203 is an example of the "first determining means" of the present invention. The process of S205 is an example of the "second determining means" of the present invention. The process of S113 is an example of the "creation means" of the present invention.

1: Machine tool 4: Tool 30: Numerical control device 31: CPU
34: Storage device 50: Motor 50A: Drive circuit _T1 : First time _T2 : Second time _T3 : Third time _T4 : Fourth time Tsum: Acceleration/deceleration time L: Feed amount ωn/2π, _ω1 /2π, ω ₂ /2π: Natural frequency Q, R: Weighting coefficient

Claims (7)

A numerical control device that drives a mechanical device by driving a motor based on an acceleration command,
The acceleration command is
Controlling the acceleration of the motor over successive first, second, third, and fourth periods;
In the first period, the acceleration of the motor increases from zero to a first acceleration,
in the second period, the acceleration of the motor decreases from the first acceleration to zero;
In the third period, the acceleration of the motor decreases from zero to a second acceleration,
In the fourth period, the acceleration of the motor increases from the second acceleration to zero,
A first time that is the length of the first period, a second time that is the length of the second period, a third time that is the length of the third period, and a fourth time that is the length of the fourth period. Among the times, the first time and the fourth time are the same, and the second time and the third time are the same,
a third time indicating the relationship between the permissible value of the vibration magnitude of the mechanical device, the feed amount of the mechanical device, and the total time of the first time, the second time, the third time, and the fourth time; a storage unit that stores one information and second information indicating a relationship between the total time and the first time;
acquisition means for acquiring the tolerance value and the feed amount;
a first determining means for determining the total time based on the allowable value and the feed amount acquired by the acquiring means, with reference to the first information stored in the storage unit;
a second determining unit that determines the first time based on the total time specified by the first determining unit and with reference to the second information stored in the storage unit;
and creating means for creating the acceleration command based on the first time determined by the second determining means. The first information is information defined based on a measured value of the magnitude of the vibration that occurs for each combination of the total time and the feed amount when the total time and the feed amount are changed. The numerical control device according to claim 1, characterized in that: The magnitude of the vibration of the mechanical device included in the first information is an integral obtained by integrating over a predetermined time a vibration waveform indicating the magnitude of the vibration generated in the mechanical device after the completion of the acceleration command. The numerical control device according to claim 2, wherein the numerical control device is a value. The second information is information defined based on an equation that sets a specific frequency component of the acceleration command to 0 for the total time,
In the equation, when a solution to the equation exists for the total time, the second determining means determines a value that is a solution to the equation as the first time, and if there is no solution to the equation. 4. The numerical control device according to claim 1, wherein the first time is determined to be a value that minimizes the magnitude of the specific frequency component. The second information is information defined based on an equation that sets a specific frequency component of the acceleration command to 0 for the total time,
In the equation, when there is a plurality of solutions for the first time that minimize the magnitude of the specific frequency component with respect to the total time, the second determining means determines the solution that is the best at 1/2 of the total time. The numerical control device according to any one of claims 1 to 4, characterized in that a value close to the first time is determined as the first time. The mechanical device has a plurality of natural frequencies,
The second information is characterized in that a weight defined by a weighting coefficient for the plurality of natural frequencies is applied to an equation in which a specific frequency component of each acceleration command is set to 0. A numerical control device according to any one of claims 1 to 5. A method for controlling a numerical control device that drives a mechanical device by driving a motor based on an acceleration command, the method comprising:
The acceleration command is
Controlling the acceleration of the motor over successive first, second, third, and fourth periods;
In the first period, the acceleration of the motor increases from zero to a first acceleration,
in the second period, the acceleration of the motor decreases from the first acceleration to zero;
In the third period, the acceleration of the motor decreases from zero to a second acceleration,
In the fourth period, the acceleration of the motor increases from the second acceleration to zero,
A first time that is the length of the first period, a second time that is the length of the second period, a third time that is the length of the third period, and a fourth time that is the length of the fourth period. Among the times, the first time and the fourth time are the same, and the second time and the third time are the same,
The numerical control device includes:
a third time indicating the relationship between the permissible value of the vibration magnitude of the mechanical device, the feed amount of the mechanical device, and the total time of the first time, the second time, the third time, and the fourth time; and second information indicating a relationship between the total time and the first time,
an acquisition step of acquiring the tolerance value and the feed amount;
a first determining step of determining the total time by referring to the first information stored in the storage unit based on the allowable value and the feed amount acquired in the acquiring step;
a second determining step of determining the first time based on the total time specified in the first determining step, with reference to the second information stored in the storage unit;
A method for controlling a numerical control device, comprising: a creation step of creating the acceleration command based on the first time determined in the second determination step.

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