JP7670283B2 - Vibration suppression method, vibration suppression device, and machine tool - Google Patents

Description

The present invention relates to a vibration suppression method, a vibration suppression device, and a machine tool.

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

JP 2019-153085 A

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

The object of the present invention is to provide a vibration suppression method, a vibration suppression device, and a machine tool that can appropriately suppress vibrations that occur when a machine device drives in response to a feed axis command.

A vibration suppression method according to a first aspect of the present invention is a vibration suppression method for suppressing vibrations that occur when a mechanical device is driven based on a position command for controlling a rotational position of a motor based on a moving distance, a speed command for controlling a speed of the motor, and an acceleration command for controlling an acceleration of the motor, the acceleration command controlling an acceleration of the motor over a first period, a second period, a third period, and a fourth period, the acceleration of the motor increasing from zero to a first acceleration in the first period, the acceleration of the motor decreasing from the first acceleration to zero in the second period, and the acceleration of the motor decreasing from the first acceleration to zero in the third period. The method further comprises: optimizing the first time and the drive time so as to minimize the amplitude of the natural vibration from a relational expression showing the amplitude of the natural vibration, the drive time being Tsum, the natural vibration frequency of the mechanical device being ωn/2π, the first time being T1, and the moving distance being L, the drive time being Tsum, ωn, T1 _{, and} L, and a determination step of determining the acceleration command based on the first _time and the drive time optimized by the optimization step. By driving the motor of the mechanical device with the acceleration command determined by the vibration suppression method, the vibration of the mechanical device occurring when the motor is driven can be suppressed.

According to a first aspect, the optimization step _is <When the drive time and the first time are varied as variables so as to satisfy the condition of Tsum/2, the method may include a first calculation step of calculating the amplitude for each pair of the first time and the drive time based on the relational expression, a first judgment step of judging whether or not there is a pair in which the amplitude is zero for each calculation result calculated by the first calculation step, and a first optimization step of determining, when it is determined by the first judgment step that there is a pair in which the amplitude is zero, the first time and the drive time of the pair in which the amplitude is zero as the first time and the drive time. The determination step may include a search step of determining the acceleration command based on the first time and the drive time optimized by the first optimization step, and, when it is determined by the first judgment step that there is no pair in which the amplitude is zero, searching for a pair of the first time and the drive time corresponding to the smallest amplitude among the amplitudes calculated by the first calculation step, and a second optimization step of determining the first time and the drive time of the pair searched by the search step as the first time and the drive time. The determination step may include In this method, when there is a pair with zero amplitude, the vibration of the mechanical device can be suppressed by optimizing the first time and drive time of the pair. Also, even when there is no pair with zero amplitude, the vibration of the mechanical device can be suppressed by optimizing the first time and drive time with the smallest amplitude.

According to the first aspect, the method includes a second determination step of determining whether the calculation result of the amplitude corresponding to the pair in which the amplitude determined by the first determination step is zero or the amplitude corresponding to the pair searched by the search step is equal to or less than a predetermined threshold, and the determination step may optimize the first time and the drive time corresponding to the amplitude determined by the second determination step to be equal to or less than the predetermined threshold. With this method, the amplitude can be suppressed to equal to or less than the predetermined threshold.

A vibration suppression method according to a second aspect of the present invention is a vibration suppression method for suppressing vibrations that occur when a mechanical device is driven based on a position command for controlling a rotational position of a motor depending on a moving distance, a speed command for controlling the speed of the motor, and an acceleration command for controlling the acceleration of the motor, the acceleration command controlling the acceleration of the motor over a first period, a second period, a third period, and a fourth period, the acceleration of the motor increasing from zero to a first acceleration in the first period, the acceleration of the motor decreasing from the first acceleration to zero in the second period, the acceleration of the motor decreasing from zero to a second acceleration in the third period, and the acceleration of the motor decreasing from zero to a fourth acceleration in the fourth period. an acquisition step of acquiring a drive time in which the acceleration of the motor increases from the second acceleration to zero, the first time being the length of the first period, the second time being the length of the second period, the third time being the length of the third period, and the fourth time being the length of the fourth period, the first time and the fourth time being the same, the second time and the third time being the same, the drive time being a time corresponding to the moving distance, and the total time of the first time, the second time, the third time, and the fourth time being specified; the drive time acquired by the acquisition step is Tsum, the natural frequency of the mechanical device is ωn/2π, and the first time is T The vibration suppression method includes a first calculation step of calculating a solution for the first time from a relational expression including Tsum, ωn, _T1 , and L and indicating an amplitude of a natural vibration so as to minimize the amplitude of the natural vibration, _a first optimization step of optimizing the solution for the first time when the solution calculated by the first calculation step exists under the condition of 0< _T1 <Tsum/2, a second calculation step _of varying the first time as a variable and calculating the amplitude based on the relational expression for each of a plurality of the first times when the solution calculated by the first calculation step does not exist under the condition of 0<T1<Tsum/2, a second optimization step of optimizing the first time corresponding to the smallest amplitude among the amplitudes calculated by the second calculation step, and a determination step of determining the acceleration command based on the first time optimized by the first optimization step or the first time optimized by the second optimization step and the drive time. By driving a motor of a mechanical device with the acceleration command determined by the vibration suppression method, vibration of the mechanical device occurring when the motor is driven can be suppressed.

According to a second aspect, the second optimization step may optimize the first time to the minimum feasible time for driving the mechanical device, and the determination step may determine the acceleration command based on the first time to the minimum feasible time optimized by the second optimization step and the drive time. In this method, the vibration of the mechanical device can be suppressed by optimizing the first time to the minimum feasible time for driving the mechanical device.

The vibration suppression device according to the third aspect of the present invention is characterized in that it includes a control unit that controls the motor of the mechanical device with the acceleration command determined by the vibration suppression method according to the first or second aspect. According to the third aspect, it is possible to achieve the same effects as the first or second aspect.

A machine tool according to a fourth aspect of the present invention is a machine tool that drives the motor based on a position command that controls a rotational position of the motor depending on a moving distance, a speed command that controls the speed of the motor, and an acceleration command that controls the acceleration of the motor, the acceleration command controlling the acceleration of the motor over a first period, a second period, a third period, and a fourth period, the acceleration of the motor increasing from zero to a first acceleration in the first period, decreasing from the first acceleration to zero in the second period, and decreasing from the first acceleration to zero in the third period. The acceleration of the motor is decreased from the second acceleration to a second acceleration in the fourth period, and the acceleration of the motor is increased from the second acceleration to zero in the fourth period, and among a first time which is a length of the first period, a second time which is a length of the second period, a third time which is a length of the third period, and a fourth time which is a length of the fourth period, the first time and the fourth time are the same, and the second time and the third time are the same, and when a drive time which specifies a total time of the first time, the second time, the third time, and the fourth time is Tsum, a natural frequency of the mechanical device is ωn/2π, the first time is _T1 , and the moving distance is L, the drive time includes Tsum, ωn, _T1 , and L, and is configured to optimize the first time and the drive time so as to minimize the amplitude of the natural vibration from a relational expression which shows the amplitude of the natural vibration, and a determination means which determines the acceleration command based on the first time and the drive time optimized by the optimization means. According to the fourth aspect, it is possible to achieve the same effect as the first or second aspect.

FIG. FIG. 2 is a block diagram showing the electrical configuration of the numerical control device 30 and the machine tool 1. 5 is a graph showing the position, velocity waveform, and acceleration waveform of the tool 4; 5 is a graph showing vibration characteristics of the machine tool 1. 1 is a graph showing an acceleration waveform. 1 is a flow chart of the main process. Flow diagram of the optimization process. FIG. 13 is a graph showing the relationship between the calculation result of the amplitude Amplitude and the first time _T1 . 11 is a flowchart of an optimization process according to a modified example.

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

The structure of the machine tool 1 will be described with reference to FIG. 1. 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 the like. The base 2 is a metal base in the shape of a substantially rectangular parallelepiped. The column 5 is fixed to the rear of the upper 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 inside. The spindle 9 has a mounting hole (not shown) at the bottom. The tool 4 is attached to the mounting hole of the spindle 9, and the spindle 9 is rotated by the drive of the spindle motor 52 (see FIG. 2). The spindle motor 52 is provided on the spindle head 7. The spindle head 7 moves in the Z-axis direction by a Z-axis movement mechanism (not shown) provided in front 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 movement mechanism (not shown), a Y-axis table 12, an X-axis movement mechanism (not shown), a table 13, etc. The Y-axis movement 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), etc. The Y-axis rail and the 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 in an approximately rectangular parallelepiped shape and includes a nut (not shown) on the bottom. The nut is screwed into 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 movement mechanism supports the Y-axis table 12 so that it can move in the Y-axis direction.

The X-axis movement 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), etc. The X-axis rails and the X-axis ball screw extend in the X-axis direction. The table 13 is formed in a rectangular plate shape in a 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 is screwed into 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 movement mechanism supports the table 13 so that it can move in the X-axis direction. Therefore, the table 13 moves in the X-axis and Y-axis directions on the base 2 by the Y-axis movement mechanism, the Y-axis table 12, and the X-axis movement mechanism.

The tool changer 20 is provided in front of the spindle head 7 and is equipped with a disk-shaped tool magazine 21. The tool magazine 21 holds multiple tools (not shown) radially on its outer periphery. The tool changer 20 drives the tool magazine 21 with a magazine motor 55 (see FIG. 2) and positions the tool specified by a tool change command at the tool change position. The tool change command is issued by an NC program. The tool change position is the lowest position of the tool magazine 21. The tool changer 20 swaps the tool 4 attached to the spindle 9 with the tool attached to the tool magazine 21 by a series of operations that include raising the spindle head 7, rotating the tool magazine 21, and lowering the spindle head 7.

The control box 6 houses 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 on the machine tool 1, and performs various processes on the workpiece 3 by moving the workpiece 3 held on the table 13 relative to the tool 4 attached to the spindle 9. The various processes include drilling using a drill or tap, side surface processing using an end mill or 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 unit 16 and a display unit 17 (see FIG. 2). The input unit 16 accepts input of various information, operation instructions, etc., 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 electrical configuration of the numerical control device 30 and the machine tool 1 will be described with reference to FIG. 2. 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 unit 35, and drive circuits 51A to 55A. The CPU 31 controls the numerical control device 30. The ROM 32 stores the main program and the like. The main program is a program for executing the main processing (see FIG. 7). 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 are axis movement of the machine tool 1, tool replacement, and the like. The axis movement includes a position command, which is a command to control the rotational position of the Z-axis motor 51, etc., based on the feed amount L. The CPU 31 creates a speed command and an acceleration command from the position command. The speed command is a command to control the speed of the Z-axis motor, etc. The acceleration command will be described later.

RAM 33 temporarily stores various information. Storage device 34 is non-volatile and stores NC programs and various information. CPU 31 can store in storage device 34 NC programs input by the operator via input unit 16 of operation panel 15, as well as NC programs read in via external input.

The drive circuit 51A is connected to the Z-axis motor 51 and the encoder 51B. The drive circuit 52A is connected to the spindle motor 52 and the encoder 52B. The drive circuit 53A is connected to the X-axis motor 53 and the encoder 53B. The drive circuit 54A is connected to the Y-axis motor 54 and the encoder 54B. The drive circuit 55A is connected to the magazine motor 55 and the encoder 55B. The Z-axis motor 51, the spindle motor 52, the X-axis motor 53, the Y-axis motor 54, and the magazine motor 55 are all servo motors (hereinafter, collectively referred to as motor 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. The drive circuits 51A to 55A receive feedback signals from the encoders 51B to 55B and perform feedback control of the position and speed. The input/output unit 35 is connected to the input unit 16 and the display unit 17 of the operation panel 15, respectively.

An example will be given of the case where the machine tool 1 is driven based on an NC program command (hereinafter referred to as a feed axis command) for moving the tool 4 in the X-axis, Y-axis, and Z-axis directions relative to the workpiece 3. Below, an example will be given of the case where the tool 4 is moved downward along the Z-axis direction relative to the workpiece 3. Although detailed explanations will be omitted, the same applies when the tool 4 is moved in the X-axis and Y-axis directions relative to the workpiece 3 for machining. The vertical axis of the graph shown in FIG. 3 indicates the position in the Z-axis direction (FIG. 3(A)), the speed (FIG. 3(B)(C)), and the acceleration (FIG. 3(D)). Hereinafter, for the sake of simplicity, the downward direction will be described as positive and the upward direction will be described as negative in FIG. 3(A) to (D). 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 indicated by a positive value. In FIG. 3(B) to (D), the speed and acceleration when the tool 4 moves downward are indicated by 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, which holds the spindle 9, in order to move the spindle head 7 to the position specified by the feed axis command. The CPU 31 outputs the target position data to the drive circuit 51A at a predetermined cycle. 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 the target position. Every time the CPU 31 inputs the 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 called 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 of the tool 4 remains constant when it moves in the Z-axis direction to the command position (see FIG. 3(B)). Next, the CPU 31 adjusts the acceleration/deceleration characteristics that correspond to the rising and falling characteristics of the waveform showing the time series change in speed (hereinafter referred to as the speed waveform) (see FIGS. 3(C) and (D)). Hereinafter, the process of adjusting the acceleration/deceleration characteristics of the speed waveform will be referred to as the acceleration/deceleration process. The slopes of the rising and falling edges of the speed waveform after the acceleration/deceleration process correspond to the acceleration of the tool 4.

The CPU 31 determines the target position for each predetermined period based on the speed waveform that has undergone acceleration and deceleration processing. The CPU 31 outputs the determined target position data to the drive circuit 51A at a predetermined period. At that time, as shown in FIG. 3(C), 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 is referred to as the acceleration time Ta, and the length of the deceleration period Pd is referred to as the 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 is referred to as an acceleration command. The acceleration command is a concept including an acceleration command for accelerating the tool 4 and a deceleration command for decelerating the tool 4. FIG. 3(D) shows a time series change in acceleration when the tool 4 moves in response to the acceleration command (hereinafter referred to as an acceleration waveform). 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 . In the acceleration period Pa, the period during which the acceleration of the tool 4 decreases 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 in 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 the second acceleration _A2 . The period during which the acceleration of the tool 4 increases in 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 succession of a first period _P1 to a fourth period _P4 . The length from the start of the first period _P1 to the end of the fourth period _P4 is referred to as the acceleration/deceleration time Tsum. The first time _T1 to the fourth time _T4 are collectively referred to as the acceleration/deceleration time constant Tα. Note that the acceleration command satisfies _T1 = _T4 and _T2 = _T3 (see FIG. 5), and it is assumed that the first time _T1 and the acceleration/deceleration time Tsum satisfy 0<T1<Tsum/2.

Note that the acceleration waveform corresponding to the acceleration command is not limited to the case shown in Fig. 3(D) and may, for example, include a period during which the acceleration remains at 0 between the second period _P2 and the third period _P3 . In the following, for ease of explanation, it is assumed that the acceleration waveform does not include a period during which the acceleration remains at 0 as shown in Fig. 3(D).

There is a method for suppressing vibrations of the machine tool 1 caused by the tool 4 moving in response to an acceleration command, by using a compensation torque command separate from the acceleration command. The compensation torque command is a command for generating vibrations in the opposite phase to the vibrations of the machine tool 1. For example, when the tool 4 moves in the Z-axis direction in response to an acceleration command, the spindle head 7 of the machine tool 1 may vibrate in the Z-axis direction at 90 Hz. At that time, the vibrations of the spindle head 7 in the Z-axis direction are suppressed using a compensation torque command that has a vibration peak at 90 Hz and is in the opposite phase to the vibration.

The vibration frequency component of the machine tool 1 that occurs when the tool 4 moves in the Z-axis direction due to an acceleration command may be, depending on the movement distance, not a frequency of 90 Hz when the spindle head 7 vibrates in the Z-axis direction, but a frequency of 30 Hz when the entire machine tool 1 vibrates (see Figure 4). At such times, the vibration of the entire machine tool 1 may not be suppressed by the compensation torque command.

In order to suppress vibrations that cannot be suppressed by the correction torque command, the CPU 31 of the numerical control device 30 determines an acceleration waveform of an acceleration command to be output to the drive circuit 51A in response to the feed axis command. More specifically, the CPU 31 determines an acceleration waveform that is less likely to generate vibrations, using the equations of relational expressions (1-1) to (1-3). Relational expression (1-1) indicates the amplitude Amplitude of the natural vibration component of the machine tool 1 contained in the acceleration command. The magnitude of the natural vibration generated in the machine tool 1 is determined by the amplitude Amplitude. Here, ωn/2π is the natural frequency of the machine tool 1. Furthermore, a indicates the ratio between the first time _T1 and the second time _T2 .

Relational expression (1-3) is derived by substituting relational expression (1-2) into relational expression (1-1). The condition for minimizing vibration of machine tool 1 is the condition for amplitude Amplitude to be zero. Here, ωn/2π is the natural frequency specific to machine tool 1, so angular velocity ωn is a constant. Therefore, when feed amount L is specified, according to relational expression (1-3), amplitude Amplitude can be expressed by two variables, first time _T1 and acceleration/deceleration time Tsum. Therefore, CPU 31 can suppress vibration by determining an acceleration command based on first time _T1 and acceleration/deceleration time Tsum that satisfy the equation of relational expression (1-3).

The CPU 31 calculates the first time _T1 and the acceleration/deceleration time Tsum that satisfy the equation of the relational expression (1-3). The calculation method will be described in detail later. The CPU 31 optimizes the calculated first time _{T1 and} the acceleration/deceleration time Tsum. The CPU 31 substitutes the optimized first time T1 and the acceleration/deceleration time Tsum into the equation (1-2) to calculate the second time _T2 . Since _T1 = _T4 and _T2 = _T3 , the CPU 31 calculates the fourth time _{T4 from the first time T1 and} the third time T3 from the second time _T2 , respectively. The CPU ₃₁ determines an acceleration command based on the optimized first time _T1 and the acceleration/deceleration time Tsum, the second time _T2 , the third time _T3 , and the fourth time _T4 . The CPU 31 drives the machine tool 1 with the generated acceleration command.

On the other hand, there may be a case where the first time _T1 and the acceleration/deceleration time Tsum that satisfy the equation of the relational expression (1-3) do not exist, that is, there is a case where a pair of the first time _T1 and the acceleration/deceleration time Tsum that makes the amplitude Amplitude zero does not exist. In this case, the CPU 31 uses the relational expression (1-3) to calculate the amplitude Amplitude for each pair of the first time _T1 and the acceleration/deceleration time Tsum with the first time _T1 and the acceleration/deceleration time Tsum as variables. The calculation method will be described in detail later. The CPU 31 optimizes the first time T1 and the acceleration/deceleration time Tsum that correspond to the smallest amplitude Amplitude among the amplitude Amplitudes calculated for each pair. The CPU 31 determines an acceleration command based on the optimized first time _T1 and the acceleration/deceleration time Tsum. The CPU 31 drives the machine tool 1 with the generated acceleration command.

The main processing executed by the CPU 31 of the numerical control device 30 will be described with reference to FIG. 6. The CPU 31 executes the main processing by reading and executing the main program stored in the storage device 34. When the main processing is executed, the CPU 31 judges whether or not an NC program has been accepted (S1). If it is determined that an NC program has not been accepted (S1: NO), the CPU 31 returns to the processing and waits. If it is determined that an NC program has been accepted (S1: YES), the CPU 31 reads one line of the NC program (S3).

The CPU 31 determines whether the line read from the NC program is a feed axis command (S5). If it is determined that it is not a feed axis command (S5: NO), the CPU 31 executes the read command other than a feed axis command (S13). If it is not a feed axis command, it may be, for example, a tool change command. The CPU 31 advances the process to S15. On the other hand, if it is determined that it is a feed axis command (S5: YES), the CPU 31 executes optimization processing (S7).

In the optimization process, the acceleration/deceleration time Tsum and the first time _T1 are optimized. When the optimization process is started, when the processing cycle of the NC device that executes the feed axis command is 0.001 sec, the CPU 31 sets the acceleration/deceleration time Tsum to 0.004 sec and the first time _T1 to 0.001 sec (S101). In the initial setting, the acceleration/deceleration time Tsum is four times the first time _T1 . The CPU 31 substitutes the set first time _T1 and acceleration/deceleration time Tsum, the angular velocity ωn obtained from the natural frequency, and the feed amount L into the relational expression (1-3) to calculate the amplitude Amplitude (S104). The CPU 31 associates the calculated amplitude Amplitude with the set of the first time _T1 and acceleration/deceleration time Tsum used in the calculation, and stores them in the storage device 34 (S105).

Next, the CPU 31 adds 0.001 sec to the first time _T1 used in calculating the amplitude Amplitude (S107). The CPU 31 determines whether the first time _T1 to which 0.001 sec has been added satisfies the condition T1<Tsum/2 (S109).

When it is determined that the condition T1<Tsum/2 is satisfied (S109: YES), the CPU 31 calculates the amplitude Amplitude by substituting the first time _T1 to which 0.001 sec has been added and the set acceleration/deceleration time Tsum into the relational expression (1-3) (S111). The CPU 31 determines whether the sign of the amplitude Amplitude stored in the process of S105 and the sign of the amplitude Amplitude calculated in the process of S111 are inverted (S113).

The reason for executing the process of S113 will be described below with reference to FIG. 8. The horizontal axis of FIG. 8 is the first time _T1 , and the vertical axis is the calculation result of the amplitude Amplitude calculated for each first time _T1 . The acceleration/deceleration time Tsum is an arbitrary constant. The amplitude Amplitude changes according to the value of the first time T1. At a position P within a range from 0 to Tsum/2, the amplitude Amplitude becomes zero. Around the first time _T1 at which the amplitude Amplitude becomes zero, the sign of the calculation result of the amplitude Amplitude is inverted from negative to positive. That is, the CPU 31 determines whether the amplitude Amplitude becomes zero by checking whether the sign of the amplitude Amplitude is inverted.

When it is determined that the sign is not inverted (S113: NO), the CPU 31 returns the process to S105 and executes the processes of S105 to S113. In this manner, the CPU 31 stores in the storage device 34 the calculation result of the amplitude Amplitude and a set of the first time _T1 and the acceleration/deceleration time Tsum corresponding to the calculation result.

On the other hand, when it is determined that the sign is inverted (S113: YES), the CPU 31 identifies a pair of the first time _T1 and the acceleration/deceleration time Tsum corresponding to the amplitude Amplitude calculated in the process of S105 or the amplitude Amplitude calculated in the process of S111, the amplitude Amplitude having a smaller absolute value (S115). In this case, it can be estimated that the calculation result of the amplitude Amplitude is a value close to zero.

When it is determined in S109 that the condition T1<Tsum/2 is not satisfied (S109: NO), the CPU 31 searches for the smallest amplitude Amplitude stored in the storage device 34 (S117). The CPU 31 specifies the first time _T1 and the acceleration/deceleration time Tsum corresponding to the smallest amplitude Amplitude found (S119).

The CPU 31 determines whether the amplitude Amplitude corresponding to the first time _T1 and the acceleration/deceleration time Tsum specified in the process of S115 or S119 is equal to or less than a predetermined threshold Th (S121). Here, the predetermined threshold Th is the maximum magnitude of the allowable vibration, and is stored in advance in the storage device 34. If it is determined that the amplitude Amplitude is greater than the predetermined threshold Th (S121: NO), the CPU 31 adds 0.001 sec to the acceleration/deceleration time Tsum, initializes the first time _T1 to 0.001 sec (S125), and returns to the process of S104. The CPU 31 executes the processes of S105 to S121 using the first time _T1 as a variable based on the acceleration/deceleration time Tsum newly set in the process of S125. In this manner, the CPU 31 varies the first time _T1 and the acceleration/deceleration time Tsum, and repeats the calculation of the amplitude Amplitude.

When it is determined in S121 that the amplitude Amplitude is equal to or less than the predetermined threshold value Th (S121: YES), the CPU 31 determines that the first time _T1 and the acceleration/deceleration time Tsum determined in the process of S115 or the process of S119 are optimal values. This process is called optimization (S123). The CPU 31 returns the process to the main process.

The CPU 31 creates an acceleration command based on the optimized first time _T1 and the acceleration/deceleration time Tsum (S9). The CPU 31 executes a feed axis command based on the created acceleration command (S11). The CPU 31 determines whether the NC program is the last line (S15). If it is determined that the NC program is not the last line (S15: NO), the CPU 31 returns the process to S3. If it is determined that the NC program is the last line (S15: YES), the CPU 31 ends the process.

As described above, the CPU 31 of the numerical control device 30 optimizes the first time _T1 and the acceleration/deceleration time Tsum from the relational expression (1-3) so as to minimize the amplitude Amplitude of the natural vibration. The CPU 31 determines the acceleration command based on the optimized first time _T1 and acceleration/deceleration time Tsum.

Numerical control device 30 drives motor 50 of machine tool 1 with the determined acceleration command, thereby suppressing vibration of machine tool 1 that occurs when motor 50 is driven. Therefore, numerical control device 30 can optimize first time _T1 and acceleration/deceleration time Tsum in a shorter time.

When the first time _T1 is varied as a variable together with the acceleration/deceleration time Tsum under the condition of 0< _T1 <Tsum/2, the CPU 31 calculates the amplitude Amplitude for each pair of the first time _T1 and the acceleration/deceleration time Tsum based on the relational expression (1-3). For each calculated result, the CPU 31 determines whether or not there is a pair for which the amplitude Amplitude is zero. When the CPU 31 determines that there is a pair for which the amplitude Amplitude is zero, it optimizes the first time _T1 and the acceleration/deceleration time Tsum of the pair for which the amplitude Amplitude is zero. The CPU 31 determines an acceleration command based on the optimized first time _T1 and acceleration/deceleration time Tsum. When there is a pair for which the amplitude Amplitude is zero, the numerical control device 30 optimizes the first time _T1 and the acceleration/deceleration time Tsum of the pair, thereby suppressing vibration of the machine tool 1. Furthermore, when the CPU 31 determines that there is no pair in which the amplitude Amplitude is zero, it searches for the smallest amplitude among the calculated amplitudes. The CPU 31 optimizes the first time _T1 and the acceleration/deceleration time Tsum of the pair corresponding to the searched amplitude. The CPU 31 determines the acceleration command based on the optimized first time _T1 and acceleration/deceleration time Tsum. Even if there is no pair in which the amplitude Amplitude is zero, the numerical control device 30 can suppress vibration of the machine tool 1 by optimizing the first time _T1 and the acceleration/deceleration time Tsum with the smallest amplitude Amplitude.

Furthermore, the CPU 31 judges whether the calculated amplitude Amplitude is equal to or less than a predetermined threshold value Th. When the CPU 31 judges that the amplitude Amplitude is equal to or less than the predetermined threshold value Th, the CPU 31 optimizes the first time _T1 and the acceleration/deceleration time Tsum for the pair in which the amplitude Amplitude is equal to or less than the predetermined threshold value Th. The numerical control device 30 can suppress the vibration of the machine tool 1 to equal to or less than the predetermined threshold value Th.

The present invention is not limited to the above embodiment, and various modifications are possible. The optimization process in the modified example will be described with reference to FIG. 9. The same processes as those in the above embodiment are given the same step numbers, and different processes are indicated with different symbols. The following description will explain the different processes in detail.

The optimization process of the modified example differs in that the acceleration/deceleration time Tsum is determined in advance according to the feed amount L included in the movement command. The storage device 34 stores a table showing the relationship between the feed amount L included in the position command and the acceleration/deceleration time Tsum associated with the feed amount L.

Also, in the above embodiment, the acceleration/deceleration time Tsum and the first time _T1 are variables, but in the modified example, only the first time _T1 is a variable. Also, in the above embodiment, the first time _T1 is optimized so that the vibration generated in the machine tool 1 is equal to or less than a predetermined threshold value Th, but the optimization process in the modified example is also different in that no comparison with the predetermined threshold value Th is performed.

When the optimization process is executed in S7 of the main process (S7), the CPU 31 acquires the feed amount L included in the movement command (S100). The CPU 31 refers to the table stored in the storage device 34 and reads the acceleration/deceleration time Tsum associated with the acquired feed amount L (S102). The CPU 31 sets the first time _T1 to 0.001 sec (S103). The CPU 31 substitutes the read acceleration/deceleration time Tsum and the set first time _T1 into the formula (1-3) to calculate the amplitude Amplitude (S104). The CPU 31 associates the calculated value of the amplitude Amplitude with the corresponding set of the acceleration/deceleration time Tsum and the first time _T1 and stores them in the storage device 34 (S105).

The processes from S107 to S119 are the same as those in the above embodiment, and therefore detailed description thereof will be omitted. In the process of S113, a value substantially equal to the solution of the first time T1 in relational equation (1-3) is calculated. That is, the CPU 31 can obtain the solution of the first time T1 in relational equation ( _1-3 ) by detecting the sign reversal in S113. Note that although the amplitude Amplitude does not become zero in the first time _T1 optimized in the processes of S117 and S119, it is optimized to the minimum first time T1 that can be realized to suppress vibration and drive the machine tool ₁ .

The CPU 31 optimizes the combination of the first time _T1 and the acceleration/deceleration time Tsum specified in the process of S115 or S119 (S123). The CPU 31 returns the process to the main process, generates an acceleration command (S9), and executes the feed axis command (S11).

As described above, the CPU 31 calculates a solution for the first time _T1 from the relational expression (1-3). When there is a calculated solution under the condition of 0< _T1 <Tsum/2, the CPU 31 optimizes the solution to the first time _T1 . When there is no calculated solution under the condition of 0< _T1 <Tsum/2, the CPU 31 varies the first time _T1 as a variable and calculates the amplitude Amplitude for each of the plurality of first times _T1 based on the relational expression (1-3). The CPU 31 optimizes the first time _T1 corresponding to the smallest amplitude Amplitude among the calculated amplitudes. The CPU 31 determines an acceleration command based on the optimized first time _T1 and the acceleration/deceleration time Tsum. The numerical control device 30 drives the motor 50 of the machine tool 1 with the determined acceleration command, thereby suppressing vibration of the machine tool 1 that occurs when the motor 50 is driven.

The CPU 31 optimizes the first time _T1 to the shortest possible value for driving the machine tool 1. The CPU 31 determines an acceleration command based on the optimized shortest possible value for the first time _T1 and the acceleration/deceleration time Tsum. By optimizing the first time _T1 to the shortest possible value for driving the machine tool 1, the numerical control device 30 can suppress vibrations of the machine tool 1.

The present invention is not limited to the above-described embodiment, and various modifications are possible. The present invention reduces vibrations in the machine tool 1, but the technology of the above-described embodiment may be applied to other mechanical devices. The main processing is not limited to being performed by the CPU 31 of the numerical control device 30, and may be performed by, for example, a PC or the like. At that time, information indicating an acceleration waveform determined by executing the main processing by the 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 by an acceleration command indicating the input acceleration waveform.

In the optimization process of the above embodiment and modified example, in the process of S107 and S125, 0.001 is added to the first time _T1 , but the added value is not limited to this and may be set appropriately. Also, in the process of S125, 0.001 is added to the acceleration/deceleration time Tsum, but the added value is not limited to this and may be set appropriately. The predetermined threshold value Th may be set appropriately.

In the process of S113, a solution of the first time _T1 that satisfies the relational expression (1-3) is calculated by determining whether or not the sign of the calculation result of the amplitude Amplitude is inverted, but this is not limited thereto. For example, a solution for the first time _T1 may be directly calculated for the relational expression (1-3). In this case, the first time _T1 may be optimized to the directly calculated solution. In the above embodiment, a case has been described in which there is one solution for the first time _T1 under the condition of 0< _T1 <Tsum/2 (see FIG. 8), but there may be multiple solutions depending on the conditions. In this case, the CPU 31 may perform optimization based on any one of the solutions.

In S121, the calculated amplitude Amplitude is compared with a predetermined threshold value Th, but the first time T1 and the acceleration/deceleration time Tsum determined in the processes of S115 and S119 may be optimized without performing the comparison process.

If there is no calculation result equal to or less than the predetermined threshold value Th in the process of S121, the CPU 31 can reduce a certain amount of vibration by optimizing the first time _T1 to a value close to zero. The value close to zero is, for example, 0.001 sec. Even in this case, the numerical control device 30 can suppress the vibration.

When the right hand side of the relational equation (1-3) is divided into the first half A and the second half B, except for T ₁ =0 and T ₁ =Tsum where the first half A is infinity, by finding T ₁ where the second half B is 0, it is possible to find T ₁ where the amplitude is 0.

＜Other＞
The numerical control device 30 is an example of a "vibration suppression device" of the present invention. The machine tool 1 is an example of a "machine device" of the present invention. The acceleration/deceleration time Tsum is an example of a "driving time" of the present invention. The feed amount L is an example of a "movement distance" of the present invention. The processing of S7 is an example of an "optimization step" of the present invention. The processing of S9 is an example of a "determination step" of the present invention. The processing of S104 and S111 is an example of a "first calculation step" of the present invention. The processing of S113 is an example of a "first judgment step" of the present invention. The processing of S115 and S123 is an example of a "first optimization step" of the present invention. The processing of S121 is an example of a "second judgment step" of the present invention. The processing of S119 and S123 is an example of a "second optimization step" of the present invention.

The process of S102 is an example of an "acquisition process" of the present invention. The processes of S104 and S111 are an example of a "first calculation process" of the present invention. The processes of S115 and S123 are an example of a "first optimization process" of the present invention. The processes of S113, S107, and S111 are an example of a "second calculation process" of the present invention. The processes of S119 and S123 are an example of a "second optimization process" of the present invention. The process of S7 is an example of an "optimization means" of the present invention. The process of S9 is an example of a "determination means" of the present invention.

1: Machine tool 4: Tool 30: Numerical control device 31: CPU
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: Natural frequency

Claims (7)

A vibration suppression method for suppressing vibrations that occur when a mechanical device is driven based on a position command for controlling a rotational position of a motor based on a moving distance, a speed command for controlling a speed of the motor, and an acceleration command for controlling an acceleration of the motor, comprising:
The acceleration command is
controlling the acceleration of the motor over successive first, second, third and fourth time periods;
During the first period, the acceleration of the motor increases from zero to a first acceleration;
During the second time period, the acceleration of the motor is decreased from the first acceleration to zero;
During the third period, the acceleration of the motor decreases from zero to a second acceleration;
during the fourth period, the acceleration of the motor increases from the second acceleration to zero;
Among a first time which is the length of the first period, a second time which is the length of the second period, a third time which is the length of the third period, and a fourth time which is the length of the fourth period, the first time and the fourth time are the same, and the second time and the third time are the same,
an optimization process for optimizing the first time and the drive time so as to minimize the amplitude of the natural vibration based on a relational expression including Tsum, ωn, T ₁ , and L, where Tsum is a drive time that defines the total time of the first time, the second time, the third time, and the fourth time, ωn/2π is a natural frequency of the mechanical device, T ₁ is a natural frequency of the mechanical device, and L is a moving distance;
a determination step of determining the acceleration command based on the first time and the drive time optimized by the optimization step. The optimization step comprises:
a first calculation step of calculating the amplitude for each pair of the first time and the drive time based on the relational expression when the drive time and the first time are changed as variables so as to satisfy a condition of 0 < _T1 <Tsum/2;
a first determination step of determining whether or not there is a pair in which the amplitude is zero for each calculation result calculated in the first calculation step;
Equipped with
When it is determined in the first determination step that there is a pair in which the amplitude is zero ,
a first optimization step of determining the first time and the drive time of the set in which the amplitude becomes zero as the optimized first time and drive time;
The determination step determines the acceleration command based on the first time and the drive time optimized in the first optimization step;
When it is determined that there is no pair in which the amplitude is zero in the first determination step ,
a search step of searching for a pair of the first time and the drive time corresponding to the smallest amplitude among the amplitudes calculated in the first calculation step;
a second optimization step of optimizing the first time and the drive time of the set searched for by the search step to determine the optimized first time and drive time ;
2. The vibration suppression method according to claim 1, wherein the determination step determines the acceleration command based on the first time and the drive time optimized in the second optimization step. a second determination step of determining whether or not the calculation result of the amplitude corresponding to the pair in which the amplitude determined in the first determination step is zero is equal to or less than a predetermined threshold value ;
Equipped with
The first optimization step optimizes the first time and the drive time corresponding to the amplitude determined in the second determination step to be equal to or less than a predetermined threshold value ,
a third determination step of determining whether the calculation result of the amplitude corresponding to the pair searched for in the search step is equal to or smaller than a predetermined threshold value;
Equipped with
The vibration suppression method according to claim 2, characterized in that the second optimization process optimizes the first time and the drive time corresponding to the amplitude for which the calculation result is determined to be below a predetermined threshold value by the third judgment process . A vibration suppression method for suppressing vibrations that occur when a mechanical device is driven based on a position command for controlling a rotational position of a motor based on a moving distance, a speed command for controlling a speed of the motor, and an acceleration command for controlling an acceleration of the motor, comprising:
The acceleration command is
controlling the acceleration of the motor over successive first, second, third and fourth time periods;
During the first period, the acceleration of the motor increases from zero to a first acceleration;
During the second time period, the acceleration of the motor is decreased from the first acceleration to zero;
During the third period, the acceleration of the motor decreases from zero to a second acceleration;
during the fourth period, the acceleration of the motor increases from the second acceleration to zero;
Among a first time which is the length of the first period, a second time which is the length of the second period, a third time which is the length of the third period, and a fourth time which is the length of the fourth period, the first time and the fourth time are the same, and the second time and the third time are the same,
acquiring a drive time that corresponds to the moving distance and defines a total time of the first time, the second time, the third time, and the fourth time;
a first calculation step of calculating a solution of the first time from a relational expression including Tsum, ωn, _T1 , and L, which indicates an amplitude of the natural vibration, so as to minimize the amplitude of the natural vibration, where Tsum is the drive time acquired by the acquisition step, ωn/2π is the natural frequency of the mechanical device, T1 is _T , and L is the moving distance;
a first optimization step of optimizing the solution at the first time when the solution calculated by the first calculation step exists under the condition of 0<T ₁ <Tsum/2;
a second calculation step of calculating the amplitude for each of a plurality of first times based on the relational expression by varying the first time as a variable when the solution calculated by the first calculation step does not exist under the condition of 0<T ₁ <Tsum/2;
a second optimization step of optimizing the amplitudes calculated in the second calculation step to the first time corresponding to the smallest amplitude;
and a determination step of determining the acceleration command based on the first time optimized by the first optimization step or the first time optimized by the second optimization step, and the drive time. the second optimization step optimizes the first time to a minimum feasible time for driving the mechanical device;
5. The vibration suppression method according to claim 4, wherein the determination step determines the acceleration command based on the first time, which is a minimum feasible value optimized by the second optimization step, and the drive time. A vibration suppression device comprising a control unit that controls the motor of the mechanical device with the acceleration command determined by the vibration suppression method according to any one of claims 1 to 5. A machine tool that drives a motor based on a position command that controls a rotational position of the motor based on a moving distance, a speed command that controls a speed of the motor, and an acceleration command that controls an acceleration of the motor,
The acceleration command is
controlling the acceleration of the motor over successive first, second, third and fourth time periods;
During the first period, the acceleration of the motor increases from zero to a first acceleration;
During the second time period, the acceleration of the motor is decreased from the first acceleration to zero;
During the third period, the acceleration of the motor decreases from zero to a second acceleration;
during the fourth period, the acceleration of the motor increases from the second acceleration to zero;
Among a first time which is the length of the first period, a second time which is the length of the second period, a third time which is the length of the third period, and a fourth time which is the length of the fourth period, the first time and the fourth time are the same, and the second time and the third time are the same,
an optimization means for optimizing the first time and the drive time so as to minimize the amplitude of the natural vibration based on a relational expression including Tsum, ωn, _T1 , and L and indicating the amplitude of the natural vibration, where Tsum is a drive time that specifies the total time of the first time, the second time, the third time, and the fourth time, ωn/ _2π is a natural frequency of the machine tool, T1 is a natural frequency of the machine tool, and L is a moving distance;
a determination means for determining the acceleration command based on the first time and the drive time optimized by the optimization means.

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