Engine control unit

Abstract

The present invention provides a technology that can reduce vibration of a machine tool caused by a sharp change in acceleration at the time of switching between oscillation modes during oscillation machining.A motor control device 1 comprises: an oscillation command calculation unit 12, which calculates an oscillation command from a motion command and an oscillation condition; an oscillation mode switching determination unit 32, which determines a time for the termination of the oscillation or the switching of a machining path; a filter time constant / application time setting unit 31, which sets a time constant τ and an application time t0 of a filter; a filter coefficient calculation unit 33, which calculates a filter coefficient K based on the time constant τ set by the filter time constant / application time setting unit 31; and a filter application unit 34, which applies a filter with the filter coefficient K to a command to drive a motor 2 during the application time t0 when the oscillation mode switching determination unit 32 determines that the switching time has been reached.

Description

Technical area

[0001] The present invention relates to an engine control device. State of the art

[0002] It is conventionally known that when cutting a workpiece with a cutting tool, the continuously generated chips become trapped in the cutting tool, causing machining errors and machine tool failures. To address this problem, oscillation cutting has been proposed, in which the chips are crushed by cutting while the cutting tool and the workpiece oscillate relative to each other (see, for example, Patent Document 1). Citation listPatent document

[0003] Patent Document 1: Unexamined Japanese Patent Application Publication No. 2011-123616 Disclosure of the invention Problems to be solved by the invention

[0004] As a means of implementing oscillation cutting, a technique that superimposes an oscillation command on a motion command has been introduced. This technique generates a discontinuous command depending on the oscillation phase at the time of switching the oscillation mode, such as at the end of oscillation or when changing the machining path during oscillation cutting, so that the acceleration may change abruptly. There is also a concern that an abrupt change in acceleration will cause machine tool vibration. The conventional technology requires improvement.

[0005] The present disclosure has been made in consideration of the above problems and aims to provide a technology that can reduce the shock of a machine tool caused by a sharp change in acceleration at the time of oscillation mode switching in oscillation machining. Means to solve the problems

[0006] The present disclosure relates to a motor control device for a machine tool that controls a motor to perform oscillation machining, the motor control device comprising: an oscillation command calculation unit that calculates an oscillation command from a movement command and an oscillation condition; a switching determination unit that determines an oscillation end or a switching timing of a machining path; a setting unit that sets a time constant and an application time of a filter; a filter coefficient calculation unit that calculates a coefficient of a filter based on a time constant set by the setting unit; and a filter application unit that, in the case of being determined as a switching timing by the switching determination unit, applies a filter of the filter coefficient to a command to drive the motor during the application time. Effects of the invention

[0007] According to the present disclosure, it is possible to provide a technology that can reduce the shock of a machine tool caused by a sharp change in acceleration at the time of switching the oscillation mode in oscillation machining. Brief description of the drawings Fig. 1 is a functional block diagram of a motor control device for a machine tool according to a first embodiment; Fig. 2 is a diagram showing a movement command; Fig. 3 is a diagram showing a sine wave oscillation command; Fig. 4 is a diagram of a superposition command created by superimposing the movement command and the oscillation command of a conventional motor control device; Fig. 5 is a diagram showing a movement command; Fig. 6 is a diagram showing an offset cosine wave oscillation command; Fig. 7 is a diagram of a superposition command created by superimposing the movement command and the oscillation command of a conventional motor control device; Fig. 8 is a functional block diagram of a motor control device for a machine tool according to a second embodiment; Fig. 9 is a functional block diagram of a motor control device for a machine tool according to a third embodiment; and Fig. 10 is a functional block diagram of a motor control device for a machine tool according to a fourth embodiment. Preferred manner of carrying out the invention

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. It should be noted that in the descriptions of the second and later embodiments, the same reference symbols are attached to configurations common to the first embodiment, and descriptions thereof will be omitted where appropriate. (First embodiment)

[0009] Fig. 1 is a functional block diagram of a motor control device 1 for a machine tool according to a first embodiment. The motor control device 1 according to the first embodiment performs an oscillating cut on a workpiece using a tool by operating at least one rotary spindle that causes a cutting tool and a workpiece to rotate relative to each other, and at least one feed axis that causes the cutting tool to move relative to the workpiece.

[0010] The motor control device 1 for a machine tool is configured using a computer that includes a memory such as ROM (Read Only Memory) and RAM (Random Access Memory), a CPU (Control Processing Unit), a communication control unit, and the like, which are connected to each other via a bus, for example. The functions and operations of the functional units described below are achieved through the cooperation of the CPU and memory built into the computer and the control programs stored in the memory. The motor control device 1 for a machine tool can be configured by a CNC (Computer Numerical Controller) and connected to a higher-level computer (not shown) such as a CNC or a PLC (Programmable Logic Controller). In addition to the machining programs, the machining conditions such as the machining speed and the machining direction are configured.the rotational speed, is input from the higher-level computer into the motor control device 1 for a machine tool.

[0011] For the sake of simplicity, it should be noted that in Fig. 1, only one motor 2 is shown, which drives one feed axis. Furthermore, the shape of the workpiece is not limited in the cutting machining according to the present embodiment. In other words, it is also applicable to a case where a plurality of feed axes (Z-axis and X-axis) are required because the workpiece has a conical or arc-shaped part on the machined surface, or a case where the workpiece is columnar or cylindrical and a specific axis (Z-axis) is sufficient as the feed axis.

[0012] As in Fig. 1, the motor control device 1 for a machine tool according to the first embodiment includes, as functional units, a position deviation processing unit 3, an integration unit 11, an oscillation command calculation unit 12, a command synthesis unit 4, a learning controller 13, a learning compensation value addition unit 5, a position control unit 14, a filter processing unit 30, a speed deviation processing unit 6, a speed control unit 15, a current deviation processing unit 7, a current control unit 16, and an amplifier 17.

[0013] The position deviation processing unit 3 calculates a deviation between the position of the feed-axis motor 2 specified by the current motion command and an actual position feedback value returned from the feed-axis motor 2. The motion command is, for example, a command specifying machining conditions, such as information about a feed amount of the cutting tool. The motion command is acquired, for example, from a machining program stored in a storage unit (not shown), a setting parameter of the machine tool, an external computer, or a combination of these.

[0014] The integration unit 11 integrates the position deviation calculated by the position deviation processing unit 3 and outputs the movement command subjected to the position deviation processing.

[0015] The oscillation command calculation unit 12 calculates an oscillation command based on the input motion command and the input oscillation condition. The oscillation command is a command to cause the feed axis to undergo reciprocal motion based on the oscillation phase. The oscillation command calculation unit 12 can set the oscillation command to a value obtained by multiplying the sine (sin θ) or cosine (cos θ) of the oscillation phase by a constant (oscillation amplitude) [mm]. The oscillation condition is acquired, for example, from a machining program stored in a storage unit (not shown), a setting parameter of the machine tool, an external computer, or a combination thereof.

[0016] The command synthesis unit 4 calculates a superposition command, which is a command for driving the motor 2, by superimposing the movement command subjected to the position deviation processing by the integration unit 11 and the oscillation command output from the oscillation command calculation unit 12.

[0017] The learning controller 13 calculates a compensation amount based on the superposition command output from the command synthesis unit 4. The learning controller 13 includes, for example, a memory and stores the oscillation phase and the compensation amount in one or more cycles of oscillation in the memory to correlate them. It reads the superposition command stored in the memory at a timing that can compensate for the phase delay of the oscillation according to the responsiveness of the motor 2, and outputs it as the compensation amount. If an oscillation phase for which the compensation amount is output is not present among the oscillation phases stored in the memory, the compensation amount to be output can be calculated from the compensation amounts with close oscillation phases.

[0018] The learning compensation value addition unit 5 adds the compensation value calculated by the learning controller 13 to the overlay command synthesized by the command synthesis unit 4. Since the position deviation with respect to the oscillation command generally increases as the oscillation frequency increases, it is possible to improve the trackability with respect to the periodic oscillation command by adding the compensation amount calculated by the learning controller 13 to the overlay command.

[0019] The position control unit 14 outputs a speed command based on the superposition command to which the compensation value has been added.

[0020] In the first embodiment, the filter processing unit 30 performs filter processing on the speed command output from the position control unit 14. Note that the details of the filter processing unit 30 will be described later.

[0021] The speed deviation processing unit 6 determines a difference between the speed command value output from the position control unit 14 and filtered by the filter processing unit 30 and an actual speed feedback value fed back from the motor 2 of the feed axis, and outputs this difference as a speed deviation.

[0022] The speed control unit 15 generates and outputs an electric current command value based on the speed deviation output by the speed deviation processing unit 6. The electric current command value is also referred to as a torque command value because it determines the torque of the motor 2.

[0023] The current deviation processing unit 7 determines a difference between the current command value output from the speed control unit 15 and the current feedback value from the amplifier 17 and outputs this difference as a current deviation to the current control unit 16.

[0024] The current control unit 16 generates a current value based on the current deviation and outputs it to the amplifier 17.

[0025] The amplifier 17 calculates a desired electric power based on the electric current value of the current control unit 16 and transmits it to the motor 2.

[0026] Next, the filter processing unit 30 will be described. The filter processing unit 30 includes a filter time constant / application time setting unit 31, an oscillation mode switching determination unit 32, a filter coefficient calculation unit 33, and a filter application unit 34.

[0027] The filter time constant / application time setting unit 31 sets a filter time constant and an application time. The filter time constant and the application time are set in advance as fixed values ​​to take into account, for example, the shock generated in the machine tool, the machining conditions, and the vibration conditions. Furthermore, the filter time constant and the application time can be configured to be automatically set based on a parameter set in the machine tool, a machining program, or the like. Note that the details of a method for setting the filter time constant and the application time will be described later.

[0028] The oscillation mode switching determination unit 32 determines whether or not it is a switching timing at which the oscillation mode should be switched. The determination as to whether or not it is the switching timing is made based on information acquired from the machining program, for example. The information acquired from the machining program is an oscillation-off command indicating that oscillation machining is finished, a command indicating a change in a movement command point, or the like. Alternatively, the determination as to whether or not it is the switching timing may detect the oscillation command and / or the overlay command and make the determination based on a change in the value(s) of the command(s). As described above, various methods can be selected to determine whether or not to switch the oscillation mode.

[0029] The filter coefficient calculation unit 33 calculates a filter coefficient for setting a filter to be applied. Note that the method for setting the filter coefficients will also be described later.

[0030] When the switching timing is determined, the filter application unit 34 performs filter processing on the command for driving the motor 2. In the first embodiment, the filter application unit 34 performs filter processing on the speed command output from the position control unit 14.

[0031] Next, the setting of the filter time constant and the application time of the filter applied by the filter application unit 34 will be described. The filter time constant and the application time are set taking into account the effect of reducing shock at the time of switching the oscillation mode and the influence of the filter on each control system. For example, the filter time constant τ is set to approximately 1 to 16 [ms], and the application time t0 is set to approximately τ to 4τ (1 to 64 [ms]). Assuming that the first-order low-pass filter is applied as a filter in the control sampling period T = 1 [ms], the cutoff frequency f is 10 to 159 [Hz], and the coefficient K is 0.37 to 0.94. It should be noted that the sampling period T = 1 [ms] is only an example and the numerical value of the sampling period can be in a range satisfying T ≤ τ.

[0032] The first-order low-pass filter can be obtained by the following equation. In the following equation, y(n) represents an output at time n, x(n) represents an input at time n, and K represents a filter coefficient. y(n)=(1−K)×x(n)+K×y(n−1)

[0033] The filter coefficient K can be determined using the following equation. In the following equation, f [Hz] represents a cutoff frequency and T [s] represents a sampling period. The filter coefficient calculation unit 33 calculates a filter coefficient using the following equation. K=exp(−2πfT)

[0034] The cutoff frequency f [Hz] can be determined using the following equation. In the following equation, τ [s] represents a time constant. f=1 / 2πτ

[0035] Here, the relationship between the filter application time and convergence is described. The filter application time is the time during which filtering actually occurs, and the application time has no effect on the filter coefficient K. However, if the application time is set too short with respect to the time constant, the convergence (an index indicating how close it is to reaching the steady state) will deteriorate, the commands at the time the filter is turned off are likely to become discontinuous, and there is a concern that shock will occur. The application time preferably considers the degree of convergence.

[0036] The degree of convergence can be determined by the following equation. In the following equation, r represents the convergence rate, t0 [s] represents the application time, and τ [s] represents the time constant. In this equation, r can be considered to converge as it approaches 1. For example, in a case where the application time is t0 = τ, r = 0.63 and converges to 63 [%]. In the case of t0 = 2τ, r = 0.86 and converges to 86 [%]. In the case of t0 = 3τ, r = 0.95 and converges to 95 [%]. In the case of t0 = 4τ, r = 0.98 and reaches 98 [%]. The degree of convergence is adjusted taking into account the vibration occurring in the machine tool. For example, if the convergence is to be 90%, the application time t0 [s] and the time constant τ [s] can be set so that t0 = 3τ. r=1−exp(−t0 / τ)

[0037] Next, the vibration at the time of a change of the oscillation mode, which occurred in the conventional technology, is described using the graphs in Figs. 2 to 6. Note that in the following graphs, the vertical axis indicates the tool position and the horizontal axis indicates the oscillation phase, e.g., the spindle angle.

[0038] Fig. Figure 2 is a diagram showing a movement command. Fig. Figure 3 is a diagram showing a sine wave oscillation command. Fig. 4 is a diagram of an overlay command obtained by superimposing a movement command (diagram of Fig. 2) and an oscillation command (diagram of Fig. 3) a conventional engine control device. As shown in the diagram of Fig. As shown in Figure 4, when the timing of the oscillation ending or the timing of the oscillation changing trajectory is not at a multiple of the oscillation phase such as 0 degrees, 180 degrees, or the like, the superposition of the oscillation command changes rapidly, and a sharp change in acceleration occurs due to the change in the superposition command. A sharp change in acceleration is a cause of excessive physical stress on the machine tool.

[0039] Fig. 5 is a diagram showing a movement command, and Fig. Figure 6 is a diagram showing an offset cosine wave oscillation command. Fig. 7 is a diagram of an overlay command obtained by overlaying the movement command (diagram of Fig. 5) and the oscillation command (diagram of Fig. 6) of a conventional engine control device. Also in the diagram of Fig. 7, there is a similar relationship between the switching timing and the oscillation phase, and there is a concern that a physical stress on the machine tool will be generated depending on the oscillation phase when the switching timing occurs.

[0040] In this regard, according to the motor control device 1 for the machine tool that controls the motor 2 to perform the oscillation machining according to the first embodiment, the following effects are exerted.

[0041] The motor control device 1 for a machine tool according to the present embodiment includes: the oscillation command calculation unit 12 that calculates an oscillation command based on a motion command and an oscillation condition; an oscillation mode switching determination unit 32 (switching determination unit) that determines an oscillation end or a switching time of a machining path; a filter time constant / application time setting unit 31 (setting unit) that sets a time constant τ and an application time t0 of a filter; a filter coefficient calculation unit 33 that calculates a filter coefficient K based on the time constant τ set by the filter time constant / application time setting unit 31;and a filter application unit 34 that applies a filter of the filter coefficient K to a command to drive the motor 2 for the application time t0 when determined by the oscillation mode switching determination unit 32 as the switching time. As a result, the filter application unit 34 performs the application-time filtering processing on the command value with respect to the command to drive the motor 2, even if the oscillation ends at a time when a sharp change in acceleration is likely to occur or the machining trajectory changes. Therefore, it is possible to avoid a sharp change in acceleration at the switching time when the oscillation phase is not 0 degrees, 180 degrees, or the like, and thus it is possible to effectively reduce the shock occurring in the machine tool.

[0042] Furthermore, in the present embodiment, the motor drive command to which the filter is applied is a speed command for performing speed control. Therefore, even when the oscillation mode is switched at a time when the oscillation phase is not 0 degrees, 180 degrees, or the like, the filter is applied to the speed command for performing speed control, and the occurrence of a sharp change in acceleration can be avoided.

[0043] Furthermore, the present embodiment provides a learning controller 13 that performs learning control based on the position deviation. Since the position deviation with respect to the oscillation command becomes larger as the oscillation frequency increases, the tracking ability with respect to the periodic oscillation command can be improved by performing learning control compensation by the learning controller. (Second embodiment)

[0044] Fig. 8 is a functional block diagram of a motor control device 1a for a machine tool according to a second embodiment. As shown in Fig. 8, the motor control device 1a for a machine tool according to the second embodiment differs from the motor control device 1 of the machine tool according to the first embodiment in the command for a filter processing unit 30a to apply a filter, and the other configurations thereof are common to those of the first embodiment.

[0045] In the second embodiment, the filter processing unit 30a is arranged between the speed control unit 15 and the current deviation processing unit 7. The electric current command value output from the speed control unit 15 is output to the motor 2 via the amplifier 17 and serves as a command for determining the torque of the motor 2. The filter application unit 34 of the filter processing unit 30a performs filter processing on the electric current command (torque command) output from the speed control unit 15 when it is determined by the oscillation mode switching determination unit 32 as the oscillation mode switching timing, similarly to the first embodiment.

[0046] As described above, in the second embodiment, the command for driving the motor 2 to which the filter is applied is an electric current command value serving as a torque control command. By applying the filter to the torque control command (electric current command), the command for driving the motor 2 is a command given in consideration of the switching timing, and the occurrence of a sharp change in acceleration can be avoided. Note that the present invention is not limited to the configuration of the second embodiment, and the torque control command may be a command issued from the current control unit 16 or a command issued from an amplifier. (Third embodiment)

[0047] Fig. 9 is a functional block diagram of a motor control device 1b for a machine tool according to a third embodiment. As shown in Fig. 9, the motor control device 1b for the machine tool according to the third embodiment differs from the motor control device 1 of the machine tool according to the first embodiment in the command for the filter processing unit 30b to apply the filter, and the other configurations thereof are common to those of the first embodiment.

[0048] In the third embodiment, the filter processing unit 30b is arranged between the oscillation command calculation unit 12 and the command synthesis unit 4. The filter application unit 34 of the filter processing unit 30b performs filter processing on the oscillation command value output from the oscillation command calculation unit 12 when it is determined by the oscillation mode switching determination unit 32 as the oscillation mode switching time, similarly to the first embodiment. The oscillation command filtered by the filter application unit 34 is output to the command synthesis unit 4 and superimposed on the movement command by the command synthesis unit 4.

[0049] Thus, in the third embodiment, the command for driving motor 2 to which the filter is applied is the oscillation command before being superimposed on the motion command. By applying the filter to the oscillation command before being superimposed on the motion command, the command for driving motor 2 is a command given with the switching timing in mind, and the occurrence of a sharp acceleration change can be avoided. (Fourth embodiment)

[0050] Fig. 10 is a functional block diagram of a motor control device 1c for a machine tool according to a fourth embodiment. As shown in Fig.10, the motor control device 1c for the machine tool according to the fourth embodiment differs from the motor control device 1 for the machine tool according to the first embodiment in a command for driving the motor 2 to which the filter processing unit 30c applies the filter, and the other configurations thereof are common to those of the first embodiment.

[0051] In the fourth embodiment, the filter processing unit 30c is arranged between the command synthesis unit 4 and the learning compensation value addition unit 5. The filter application unit 34 of the filter processing unit 30c performs filter processing on the superimposed command value output from the command synthesis unit 4 when it is determined by the oscillation mode switching determination unit 32 as the oscillation mode switching time, similarly to the first embodiment. The filtered superimposed command is output to the learning compensation value addition unit 5.

[0052] Thus, in the fourth embodiment, the command to drive the motor 2 to which the filter is applied is a superposition command obtained by superimposing the oscillation command on the movement command. By applying the filter to the superposition command obtained by superimposing the oscillation command on the movement command, the command to drive the motor 2 is a command issued taking the switching timing into account, and the occurrence of a sharp acceleration change can be avoided.

[0053] It should be noted that the present disclosure is not limited to the embodiments described above, and changes and improvements within a range that can achieve the object of the present disclosure are included in the present disclosure.

[0054] Although the above embodiment described an example in which the filter applied by the filter application unit 34 is a first-order low-pass filter, the present invention is not limited to this. For example, another filter, such as a second-order or higher-order low-pass filter or a band-pass filter, may be applied. Explanation of reference symbols 1, 1a, 1b, 1c Motor control device for machine tools 12 Oscillation command calculation unit 31 Filter time constant / application time setting unit 32 Oscillation mode switching determination unit 33 Filter coefficient calculation unit 34 Filter application unit QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2011-123616

[0003]

Claims

[1] A motor control device for a machine tool that controls a motor to perform oscillation machining, the motor control device comprising: an oscillation command calculation unit that calculates an oscillation command from a movement command and an oscillation condition; a switching determining unit that determines an oscillation end or a switching time of a machining path; a setting unit that sets a time constant and an application time of a filter; a filter coefficient calculation unit that calculates a coefficient of a filter based on a time constant set by the setting unit; and a filter application unit which, in a case where it is Switching determination unit applies a filter of the filter coefficient to a command to drive the motor during the application time when the switching time is determined. [2] The motor control device according to claim 1, wherein the command for driving the motor to which a filter is applied is a speed command for performing speed control. [3] The motor control device according to claim 1, wherein the command for driving the motor to which a filter is applied is a torque control command. [4] The motor control device according to claim 1, wherein the command for driving the motor to which a filter is applied before superimposing a movement command is an oscillation command. [5] The motor control device according to claim 1, wherein the command for driving the motor to which a filter is applied is a superposition command obtained by superimposing an oscillation command with a movement command. [6] The motor control device according to any one of claims 1 to 5, further comprising a learning controller that performs learning control based on a position deviation.

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