JP2018118362A - Machine tool and vibration suppression method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machine tool capable of highly accurately processing a work-piece, and a vibration suppression method.SOLUTION: A machine tool comprises: a driving mechanism moving a moving object including a work-piece and a table on which the work-piece can be placed; a servo part having a motor activating the driving mechanism and a servo control part controlling the motor; a weight calculation part calculating a weight of the moving object during processing of the work-piece; a natural frequency calculation part calculating a natural frequency of the moving object based on the weight of the moving object; a parameter setting part setting and storing a parameter for processing the work-piece; a program analysis part analyzing a processing program; and a main control part having a track generation part generating a track on which the driving mechanism moves. The servo part or the main control part further comprises a filter processing part attenuating vibration of a natural frequency band of the moving object.SELECTED DRAWING: Figure 2

Description

  Embodiments according to the present invention relate to a machine tool and a vibration suppression method.

  The machine tool processes the workpiece while moving the table on which the workpiece is mounted. When machining such as workpiece cutting, natural vibrations may occur in moving objects such as the workpiece and the table. The amplitude of the natural vibration of such a moving object increases as the workpiece weight increases, and increases as the acceleration of the moving object increases. Such natural vibration of the moving object causes the flatness of the cutting surface of the workpiece to deteriorate. Therefore, when the amplitude of the natural vibration of the moving object exceeds the allowable value, a problem of processing failure occurs. As means for solving this problem, a method of setting the acceleration of a moving object according to the workpiece weight measured before machining has been proposed.

JP-A-11-090769

  However, even if the acceleration can be set according to the workpiece weight and the machining time can be shortened, it cannot cope with the change in the natural vibration frequency of the moving object due to the weight of the moving object changing as the machining progresses. In some cases, the processing error may exceed the allowable range. In some cases, a filter is used to suppress the natural vibration of the moving object, but the timing for setting the filter cutoff frequency, measuring the workpiece weight, and setting the acceleration of the moving object is before starting the machining. Therefore, the cut-off frequency of the filter has been set low based on the relatively heavy workpiece weight before processing. If the cut-off frequency of the filter is set low, the filter cut-off frequency will remain low even if the workpiece weight changes from moment to moment as the workpiece is processed. End up.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a machine tool and a vibration suppression method capable of machining a workpiece with high accuracy.

  The machine tool according to the present embodiment includes a drive unit that moves a moving object including a workpiece and a table on which the workpiece can be placed, a motor that operates the drive mechanism, and a servo unit that controls the motor. And a weight calculation unit for calculating the weight of the moving object during processing of the workpiece, a natural frequency calculation unit for calculating the natural frequency of the moving object based on the weight of the moving object, and parameters for processing the workpiece. A parameter setting unit for setting and storing, a program analysis unit for analyzing a machining program, and a main control unit having a trajectory generation unit for generating a trajectory on which the drive mechanism moves, the servo unit or the main control unit moving A filter processing unit for attenuating vibrations in the natural frequency band of the object is further provided.

  The main control unit may calculate the weight of the moving object based on the acceleration of the moving object and the torque value of the motor.

  The main control unit receives the position information of the moving object and the torque value or the current value for controlling the motor from the servo unit, calculates the acceleration from the position information, and calculates the torque value from the current value when the current value is received. May be.

  The main control unit analyzes, in advance, an unexecuted portion of the workpiece machining program that has not yet been executed during machining of the workpiece, and the moving object of the unexecuted portion accelerates or decelerates a distance greater than a predetermined value. The weight of the moving object may be calculated based on the acceleration and torque values obtained by detecting one block and executing the first block.

  The main control unit may change the natural frequency setting of the filter processing unit based on the weight of the moving object before or during execution of any block after the first block among the non-executed parts.

  The main control unit calculates a ratio between the first natural frequency of the moving object before processing or at the beginning of processing and the second natural frequency of the moving object during processing, and uses the ratio to move the moving object at an arbitrary position. By correcting the third natural frequency, the fourth natural frequency of the moving object being processed at an arbitrary position is calculated, and the filter processing unit is set so as to attenuate the vibration of the fourth natural frequency. May be.

  The main control unit may calculate the fourth natural frequency at any position by multiplying the third natural frequency at any position by a ratio.

  The main control unit may calculate or measure the natural frequencies at a plurality of positions in advance, and may calculate the third natural frequency at an arbitrary position by interpolating the natural frequencies between the plurality of positions.

  The main control unit may calculate the third natural frequency at any position by linearly interpolating the natural frequencies between the plurality of positions.

  The main control unit may calculate the third natural frequency at an arbitrary position by performing linear interpolation or Lagrange interpolation on the natural frequency between the plurality of positions.

  The vibration control method according to the present embodiment includes a drive mechanism that moves a moving object including a work and a table on which the work can be placed, a motor that operates the drive mechanism, and a servo that includes a servo control unit that controls the motor. And a main control unit that outputs a position command to the servo unit, a method for suppressing vibration of a moving object in a machine tool, wherein the weight of the moving object is calculated during processing of the workpiece, A filter processing unit is provided that calculates the natural frequency of the moving object based on the frequency and attenuates the vibration in the natural frequency band of the moving object.

  The weight of the moving object may be calculated based on the acceleration of the moving object and the torque value of the motor.

  The vibration control method further includes receiving the position information of the moving object and the torque value or the current value for controlling the motor from the servo unit before calculating the weight of the moving object, and the acceleration is calculated from the position information. When the current value is received, the torque value may be calculated from the current value.

  In the vibration control method, before receiving the position information and the torque value or the current value from the servo control unit, during the machining of the workpiece, an unexecuted portion of the workpiece machining program that has not yet been executed is analyzed in advance. It further comprises detecting a first block of the execution portion in which the moving object accelerates or decelerates a distance greater than or equal to a predetermined value, and the weight of the moving object is an acceleration and torque value obtained by executing the first block. May be calculated based on

  The vibration control method calculates a ratio between the first natural frequency of a moving object before processing or at the beginning of processing and the second natural frequency of a moving object during processing, and uses the ratio to move at an arbitrary position. The method further comprises calculating a fourth natural frequency of a moving object being processed at an arbitrary position by correcting the third natural frequency of the object, and the filter processing unit includes a vibration of the fourth natural frequency. May be set to attenuate.

The figure which shows an example of a structure of the motor 11, the drive mechanism 2, and the table 3 of the machine tool 100 by 1st Embodiment. The block diagram which shows an example of a structure of the machine tool 100 by 1st Embodiment. The graph which shows the speed of a moving object, the acceleration of a moving object, and the amplitude of the natural vibration of a moving object when a moving object is accelerated. The figure which shows an example of a process of the process program. The graph which shows the speed of the moving object according to the block B5 shown in FIG. 4, the acceleration / deceleration torque command of the motor 11, the friction torque by a Coulomb friction, the friction torque by a viscous friction, and a torque. The flowchart which shows a series of operation examples of the machine tool 100 by 1st Embodiment. The graph which shows an example of the natural frequency (omega) of the moving object by 2nd Embodiment.

  Embodiments according to the present invention will be described below with reference to the drawings. This embodiment does not limit the present invention.

(First embodiment)
FIG. 1 is a diagram illustrating an example of the configuration of the motor 11, the drive mechanism 2, and the table 3 of the machine tool 100 according to the first embodiment. The machine tool 100 performs processing such as cutting on the workpiece using a tool while moving the table 3 on which the workpiece is mounted. The moving object is a so-called linear system moving object, such as a workpiece that moves in the horizontal direction along the axis, and the table 3. The workpiece is, for example, a mold. The moving object may be a tool including a spindle head instead of the workpiece and the table 3.

  The motor 11 is connected to the drive mechanism 2 via the coupling 4.

  The drive mechanism 2 moves a moving object including a work and a table 3 on which the work can be placed. The drive mechanism 2 includes a bed 21, a ball screw 22, and a linear guide 23. The bed 21 is fixed to the main body of the machine tool 100 and mounts other components of the drive mechanism 2. The ball screw 22 is connected to the motor 11 by the coupling 4 and is configured to rotate according to the rotation of the shaft of the motor 11. The rotational force of the motor 11 is transmitted to the nut 24 via the ball screw 22 and can move linearly along the ball screw 22.

  The table 3 is supported by a linear guide 23. The table 3 moves in the axial direction of the ball screw 22 and the linear guide 23 (in the direction of the arrow Ar). The direction of the arrow Ar is, for example, a certain linear direction in the horizontal plane. The table 3 can be loaded with a workpiece. Further, in order to cut the workpiece with a tool, the table 3 moves the workpiece relative to the bed 21.

  FIG. 2 is a block diagram illustrating an example of the configuration of the machine tool 100 according to the first embodiment. The machine tool 100 includes a servo unit 1, a drive mechanism 2, and a main control unit 5. The servo unit 1 includes a motor 11, a filter processing unit 14, and a servo control unit 12.

  The motor 11 operates the drive mechanism 2 as described with reference to FIG. As a result, the table 3 moves along the linear guide 23. The motor 11 is operated by the servo control unit 12.

  The filter processing unit 14 functions to attenuate the vibration of the moving object in the natural frequency band.

  The servo control unit 12 includes a position control unit 12a that controls the motor 11, a speed control unit 12b, and a current control unit 12c. The servo control unit 12 filters the command position information from the main control unit 5 by the filter processing unit 14, and performs feedback control of the motor 11 according to the commanded position information that has been filtered. The motor 11 is provided with a rotary encoder 13. The rotary encoder 13 detects the rotation of the shaft of the motor 11 and measures the displacement of the position. The displacement of the position is fed back to the servo controller 12 (position controller 12a and speed controller 12b) and the main controller 5. The rotary encoder 13 may be a linear encoder or a resolver. Further, the current control unit 12 c outputs a torque value for controlling the motor 11 to the main control unit 5. The current control unit 12 c may output a current value for controlling the motor 11 to the main control unit 5. Here, the torque value is a measured torque value or a torque command value received from the current control unit 12c. It may be different from the torque calculation value described later. The torque value may be converted from a current (current value) that controls the motor 11. Hereinafter, the torque value is also simply referred to as “torque”.

  The servo unit 1 includes a filter processing unit 14 that attenuates vibrations in the natural frequency band of the moving object. When the servo unit 1 receives the natural frequency from the main control unit 5, the natural frequency is set in the filter processing unit 14. The filter is, for example, a notch filter that can attenuate the vibration in the natural frequency band of the moving object.

  The main control unit 5 includes a parameter setting unit 51, a program analysis unit 52, a trajectory generation unit 53, a weight calculation unit 54, and a natural frequency calculation unit 55.

  The parameter setting unit 51 stores parameters of the machine tool 100. The parameters are, for example, information on the axis on which the workpiece is placed (lead information), rigidity of the feed drive mechanism, and the like. These parameters are stored in the parameter setting unit 51.

  The program analysis unit 52 analyzes the workpiece machining program 6, generates analysis information, and outputs the analysis information to the trajectory generation unit 53. The analysis information is information such as the coordinates of the target position of the moving object for each block of the machining program 6 and the target moving speed of the moving object, which are obtained by analysis of the machining program 6. A block is a basic unit of the machining program 6 and indicates, for example, a command for one line. The command for one line (one block) is a command for basic operations such as linear movement, circular movement, and rotation start / stop of the spindle. The program analysis unit 52 analyzes an unprocessed block in advance before the trajectory generation unit 53 generates the command position information. This is a “preanalysis” described later with reference to FIG.

  The trajectory generation unit 53 generates command position information such as target position data for each control cycle based on analysis information such as a movement position and a movement speed for each block of the machining program 6. Thereby, for example, as shown in FIG. 5A, the trajectory generation unit 53 accelerates to the target speed with the set acceleration, moves at a constant target speed, and then decelerates from the target speed with the acceleration. Command position information is generated so that the target position can be reached. The machine tool 100 processes the workpiece while moving the moving object according to each block of the machining program 6 in this way.

  The control cycle is a control cycle of the position control unit 12a, and is a unit of time shorter than the time from execution of one block to completion.

  For example, it is assumed that the control cycle is 1 msec. In this case, the trajectory generation unit 53 calculates how much it should move every 1 msec from t1 to t4 (for example, 1 min) in FIG. 5A, and uses the distance the moving object moves every 1 msec as the command position information. Generate. The total moving distance that the moving object moves can be obtained by integrating the command position information every 1 msec in the velocity graph in FIG. In this way, the machine tool 100 executes the movement of the moving object according to the block.

  Further, the trajectory generation unit 53 sends a weight calculation command to the weight calculation unit 54. The weight calculation command is a command for determining whether or not to calculate the weight M of the moving object based on the result of the analysis information of a certain block. For example, in the analysis information, when the block can calculate the weight M of the moving object, the trajectory generation unit 53 sets the weight calculation command to logic high. In this case, the weight calculation unit 54 calculates the weight M of the moving object when moving the moving object according to the block. On the other hand, when the block does not calculate the weight M of the moving object, the trajectory generation unit 53 sets the weight calculation command to logic low. In this case, the weight calculation unit 54 does not calculate the weight M of the moving object when moving the moving object according to the block. As described above, the trajectory generation unit 53 can cause the weight calculation unit 54 to calculate the weight M of the moving object based on the analysis information.

  When calculating the weight M of the moving object during machining of the workpiece according to the weight calculation command, the weight calculation unit 54 uses the expression 3 described later, based on the torque calculation value T of the motor 11 and the acceleration A of the moving object. Ask. The torque calculation value T is a torque calculation value used for weight calculation, and is a value calculated from a measured torque value or a torque command value. Therefore, the torque calculation value T may be different from the torque value, that is, the actually measured torque value or the torque command value. The weight calculation unit 54 outputs the calculated weight M of the moving object to the natural frequency calculation unit 55.

  On the other hand, the torque for moving the moving object is not only used for driving the motor 11 or the moving object, such as the friction torque, as well as the torque (acceleration / deceleration torque) used for the acceleration / deceleration of the motor 11 and the moving object. Including ingredients.

  In the present embodiment, the weight calculation uses the average torque during acceleration / deceleration. Further, when the difference between the average torque during acceleration and the average torque during deceleration is obtained, the friction torque is canceled and can be ignored. Therefore, a value obtained by dividing the difference between the average torque during acceleration and the average torque during deceleration by 2 is used as the torque calculation value T used in the weight calculation.

  The natural frequency calculation unit 55 receives the weight M of the moving object from the weight calculation unit 54. The natural frequency calculation unit 55 calculates the natural frequency ω of the moving object by using the weight M of the moving object and Equation 2 described later. Further, by operating the filter at the calculated natural frequency ω of the moving object, the vibration at the natural frequency ω can be suppressed.

  The parameter setting unit 51, the program analysis unit 52, the trajectory generation unit 53, the weight calculation unit 54, and the natural frequency calculation unit 55 constituting the main control unit 5 are a single CPU (Central Processing Unit). Or may be realized by individual CPUs. The servo unit 1 may be a part of the main control unit 5. The servo unit 1 may not include the filter processing unit 14, and the main control unit 5 may include the filter processing unit 14.

FIGS. 3A to 3C are graphs showing the speed of the moving object, the acceleration of the moving object, and the amplitude of the natural vibration of the moving object, respectively, when the moving object is accelerated. In this graph, the filter processing unit 14 of the servo unit 1 is not set appropriately. Therefore, referring to FIG. 3B and FIG. 3C, it can be seen that the natural vibration is generated in the moving object at times t10 and t20 when the acceleration of the moving object increases and decreases. The relationship between the natural frequency ω (rad / sec) and the frequency f (Hz) is expressed by Equation 1.

尚、ｋは送り駆動機構の剛性であり、その単位は、（ｋｇｆ／ｍ）である。Ｍは移動物の質量であり、その単位は（ｋｇ）である。以降、移動物の重量（ｋｇｆ）と質量（ｋｇ）とは同じとして、これらを移動物の重量Ｍと表す。 Further, the natural frequency ω of the moving object is also expressed by Equation 2.

Note that k is the rigidity of the feed drive mechanism, and its unit is (kgf / m). M is the mass of the moving object, and its unit is (kg). Hereinafter, the weight (kgf) and mass (kg) of the moving object are the same, and these are represented as the weight M of the moving object.

  In the case of workpiece cutting, the weight M of the moving object changes from moment to moment as workpiece machining proceeds. Referring to Equation 2, it can be seen that the natural frequency ω of the moving object changes with time.

  On the other hand, the machine tool 100 according to the present embodiment appropriately sets the filter processing unit 14 in accordance with the natural frequency ω of the moving object that changes as the workpiece is processed. For this purpose, the machine tool 100 calculates the weight M of the moving object while machining the workpiece, and calculates the natural frequency ω of the moving object based on the weight M.

  In order to calculate the weight M of the moving object during processing of the workpiece, the moving object needs to accelerate or decelerate a sufficient distance. Therefore, in order to detect the acceleration distance or the deceleration distance of the moving object in advance, the following analysis of the machining program 6 as described below is required.

  FIG. 4 is a diagram illustrating an example of processing of the machining program 6. The prior analysis will be described with reference to FIG. The pre-analysis is to analyze in advance the target position and target speed indicated in the block before the trajectory generating unit 53 generates the command position information of the non-executed block of the machining program 6. . The unexecuted block is a block that is executed after the block being executed. The program analysis unit 52 first analyzes a block of an unexecuted portion that has not been executed in the workpiece machining program 6 during machining of the workpiece.

  For example, in FIG. 4, the block B3 is a block that is being executed, and the blocks after the block B4 are blocks that have not been executed. For example, the program analysis unit 52 analyzes the blocks B4, B5, B6. In the previous analysis, the program analysis unit 52 analyzes the target position and target speed of the block B5 that is not executed. The analysis information (target position and target speed) obtained by the previous analysis is sent to the trajectory generation unit 53 before execution of the block B5. The trajectory generation unit 53 obtains a target position for each control period based on the analysis information, generates command position information, and the servo unit 1 operates the drive mechanism 2 according to the command position information. As described above, the program analysis unit 52 analyzes the machining program 6 for each block in order to move the moving object.

  On the other hand, the trajectory generation unit 53 outputs not only the command position information but also a weight calculation command based on the analysis information. That is, in this embodiment, the analysis information obtained by the previous analysis is used not only for the movement of the moving object but also for determining whether the weight M can be calculated.

  For example, the program analysis unit 52 first analyzes the block B5 as the first block, generates analysis information of the block B5, and calculates the acceleration or deceleration distance. Next, the program analysis unit 52 determines whether or not the acceleration or deceleration distance of the moving object in the block B5 is a predetermined value or more. This predetermined value indicates a threshold of distance at which the weight M of the moving object can be calculated. For example, when the target distance is shorter than a predetermined value, the moving object accelerates and decelerates without reaching the target speed. In this case, the torque becomes a transitional state, and it is difficult to obtain the correct torque of the motor 11 at the target speed. For this reason, the trajectory generation unit 53 determines not to calculate the weight M of the moving object. On the other hand, when the acceleration or deceleration distance is equal to or greater than the predetermined value, the trajectory generation unit 53 determines to calculate the weight M of the moving object by executing the block B5. The program analysis unit 52 outputs the result of the previous analysis to the trajectory generation unit 53 as analysis information. The program analysis unit 52 may determine whether the weight M can be calculated.

  Next, the trajectory generation unit 53 outputs a weight calculation command corresponding to the analysis information to the weight calculation unit 54 shown in FIG. At the same time, after execution of the block B4, the trajectory generation unit 53 outputs the command position information of the block B5 to the servo unit 1 based on the analysis information. Thereby, the weight calculating part 54 can measure and calculate the acceleration A and the torque calculation value T of the moving object at the timing when the moving object is moved according to the block B5.

  The calculation of the weight M of the moving object will be described later in detail.

  The weight calculation unit 54 sends the weight M of the moving object to the natural frequency calculation unit 55. The natural frequency calculator 55 receives the weight M of the moving object from the weight calculator 54 and calculates the natural frequency ω of the moving object by applying the weight M of the moving object to Equation 2.

  After moving the moving object according to the block B5, before moving the moving object according to the next block B6, the natural frequency calculation unit 55 causes the servo unit 1 to attenuate the vibration at the natural frequency ω of the moving object. The filter processing unit 14 included in FIG. Or the natural frequency calculating part 55 may make the filter process part 14 work before execution of the arbitrary blocks after block B6. In this case, for example, the filter processing unit 14 changes the setting of the natural frequency at the timing set by the machining program 6 or the timing notified from the outside of the machine tool 100 by a PLC (Programmable Logic Controller) or the like. May be. Further, the natural frequency calculation unit 55 may cause the filter processing unit 14 to work during execution of an arbitrary block after the block B6.

  In this way, in order to accurately calculate the weight M of the moving object, the program analysis unit 52 detects in advance the block of the machining program 6 in which the moving object accelerates or decelerates by a distance equal to or greater than a predetermined value. Yes.

(Calculation of weight M)
The calculation of the weight M of the moving object will be described.

  5A to 5E respectively show the speed of the moving object, the acceleration / deceleration torque of the motor 11, the friction torque due to Coulomb friction, the friction torque due to viscous friction, and the torque according to the block B5 shown in FIG. It is a graph to show. FIG. 5A shows the speed calculated from the actual measurement value of the position displacement in the block B5 or the speed command of the block B5 generated by the trajectory generation unit 53. FIG. 5B shows the acceleration / deceleration torque of the motor 11. FIG. 5C shows Coulomb friction during execution of block B5. FIG. 5D shows the viscous friction during execution of block B5. FIG. 5E shows the torque of the block B5. This torque may be converted from an actual measurement value of a current for controlling the motor 11.

  The friction torque includes Coulomb friction shown in FIG. 5C and viscous friction shown in FIG. Coulomb friction shown in FIG. 5C is friction that works when an object having mass moves. Therefore, the Coulomb friction in FIG. 5C indicates that constant friction works in a region where the speed of the moving object is not zero. Viscous friction is friction proportional to the speed of a moving object. Therefore, the viscous friction in FIG. 5D is a graph similar to the speed of the moving object. The torque is the sum of the acceleration / deceleration torque, the friction torque of Coulomb friction, and the friction torque of viscous friction, and has a graph as shown in FIG.

  First, the weight calculator 54 samples the speed and torque during acceleration or deceleration. This sampling is to select an arbitrary data point from the speed and torque obtained for each control cycle. The number of times of sampling is not particularly limited. For example, the sampling is performed 100 times at the time of acceleration from t1 to t2 or at the time of deceleration from t3 to t4. Next, the weight calculator 54 cuts the high frequency component of the sampled data with a low pass filter. Next, the weight calculator 54 obtains the slope of the sampled speed by the least square method. The gradient of this speed is acceleration A. The average value of the absolute values of acceleration at t1 to t2 and t3 to t4 may be set as the acceleration A. Note that the acceleration command value may be used as the acceleration regardless of the actually measured displacement value.

  Furthermore, the weight calculator 54 obtains an average value of torque during acceleration / deceleration of the block B5. The weight calculator 54 divides by 2 the difference between the average value of the sampled torque during the acceleration period from t1 to t2 and the average value of the sampled torque during the deceleration period from t3 to t4 in FIG. Thereby, the weight calculation part 54 can calculate the average value of the torque at the time of acceleration / deceleration from which the friction torque is removed as the torque calculation value T. The torque calculation value T is substantially equal to the average value of the acceleration / deceleration torque from t1 to t2 and the absolute value of the acceleration / deceleration torque from t3 to t4 in FIG.

ここで、トルク演算値Ｔの単位は、（ｋｇｆ・ｍ）、Ａの単位は（ｍ／ｓｅｃ^２）、Ｊｍは回転駆動系のイナーシャ（ｋｇｆ・ｍ・ｓｅｃ^２）、Ｌはモータ１回転あたりの軸移動量（ｍ）である。尚、回転駆動系のイナーシャＪｍおよびモータ１回転あたりの軸移動量Ｌは、パラメータ設定部５１により設定される定数である。 Thereafter, the weight calculator 54 calculates the weight M of the moving object by using the torque calculation value T and the acceleration A in Equation 3. The weight M of the moving object is expressed by Equation 3.

Here, the unit of the torque calculation value T is (kgf · m), the unit of A is (m / sec ² ), Jm is the inertia of the rotary drive system (kgf · m · sec ² ), and L is per motor rotation. The amount of movement (m). The inertia Jm of the rotational drive system and the shaft movement amount L per one rotation of the motor are constants set by the parameter setting unit 51.

  Thus, the machine tool 100 according to the present embodiment can automatically calculate the weight M of the moving object during the machining of the workpiece.

  Note that the weight calculation unit 54 replaces either the acceleration A during acceleration or deceleration and / or the torque calculation value T with the average value of either torque during acceleration or deceleration as expressed in Equation 3. It may be used to determine the weight M of the moving object. In this case, the weight calculator 54 needs to take measures such as measuring the friction torque.

  The weight calculation unit 54 may measure the weight M of the moving object using an external sensor such as a weight sensor. Further, the natural frequency calculation unit 55 may measure the natural frequency ω of the moving object using an external sensor such as a vibration sensor.

  FIG. 6 is a flowchart showing a series of operation examples of the machine tool 100 according to the first embodiment.

  First, the user sets parameters of the machine tool 100 in the parameter setting unit 51 (S10). The parameter setting unit 51 includes identification information indicating the axis on which the workpiece is placed, the rigidity k of the feed driving mechanism, the acceleration of the moving object at the time of machining, the inertia Jm (motor information) of the rotary drive system, and per motor rotation The axis movement amount L (lead information) is stored. These parameters are set during machine adjustment.

  Next, the machine tool 100 executes the machining program 6 (S20). Until the machining program 6 ends, the program analysis unit 52 performs a prior analysis of the machining program 6 (NO in S30, S40). The program analysis unit 52 first analyzes a block (for example, B5) of the machining program 6 and detects whether or not the distance for accelerating or decelerating the moving object is a predetermined value or more. When the acceleration or deceleration distance is equal to or greater than the predetermined value (YES in S50), the weight calculation unit 54 calculates the weight M of the moving object using Equation 3 as described above (S60).

  The natural frequency calculating unit 55 calculates the natural frequency ω of the moving object based on the calculated weight M of the moving object (S70). The natural frequency calculation unit 55 changes the natural frequency setting of the filter processing unit 14 of the servo unit 1 so as to suppress the vibration of the natural frequency ω of the moving object (S80). The setting change of the natural frequency of the filter processing unit 14 is performed before the execution of the block next to the previously analyzed block (for example, B6). The setting change of the natural frequency of the filter processing unit 14 may be performed before execution of an arbitrary block after the previously analyzed block (for example, B5). In addition, the natural frequency calculation unit 55 may change the natural frequency setting of the filter processing unit 14 during execution of an arbitrary block after the block B6.

  On the other hand, when the distance to accelerate or decelerate is less than the predetermined value (NO in S50), steps S60 to S80 are not executed in that block. In this case, although the setting change of the natural frequency of the filter processing unit 14 is not executed, the machining of the workpiece is continued.

  The machine tool 100 repeats steps S40 to S80 until the machining program 6 ends, and ends the operation when the machining program 6 ends (YES in S30).

  As described above, the machine tool 100 according to the present embodiment calculates the weight M of the moving object during the processing of the workpiece, calculates the natural frequency ω of the moving object corresponding to the weight M of the moving object that changes from time to time, The natural frequency of the filter processing unit 14 can be set so as to suppress the vibration of the natural frequency ω. In this way, by suppressing the natural vibration of the moving object that changes from moment to moment, machining defects due to the natural vibration can be suppressed, and high-accuracy machining can be performed. Furthermore, since the machine tool 100 can suppress the natural vibration of the moving object without reducing the acceleration of the moving object, the machine tool 100 can process at a high acceleration. Therefore, the machine tool 100 according to the present embodiment can process a workpiece at high speed, in a short time, and with high accuracy.

  Further, since the machine tool 100 according to the present embodiment automatically calculates the weight of the moving object and sets the filter while the machining program 6 is being executed, it is not time-consuming for the user.

(Second Embodiment)
The natural frequency ω of the moving object may depend on the position of the moving object in the drive mechanism 2. However, in the first embodiment, although the natural frequency ω of the moving object being processed depends on the weight M of the moving object, the position of the moving object is not considered. Therefore, the machine tool 100 according to the second embodiment calculates the natural frequency ω of the moving object in consideration of not only the weight M of the moving object but also the position of the moving object.

  The machine tool 100 according to the second embodiment obtains the natural frequency based on the weight M of the moving object and the natural frequency based on the position of the moving object separately, and corrects each natural frequency to correct the natural frequency of the moving object. Calculate the frequency ω.

  The natural frequency due to the weight M of the moving object may be the same as the natural frequency ω of the moving object calculated by the machine tool 100 according to the first embodiment. The configuration of the machine tool 100 according to the second embodiment is basically the same as the configuration of the machine tool 100 according to the first embodiment, and thus detailed description thereof is omitted.

  FIG. 7 is a graph showing an example of the natural frequency ω of the moving object according to the second embodiment. The vertical axis of this graph indicates the natural frequency of the moving object, and the horizontal axis indicates the distance of the moving object from a certain reference point. That is, the X axis indicates the position of the moving object.

  Prior to machining or at the beginning of machining, the workpiece is hardly cut, so the weight M of the moving object is relatively heavy. On the other hand, when the workpiece is processed during the processing, the weight M of the moving object gradually decreases. Therefore, the natural frequency of the moving object becomes higher than the natural frequency before processing as the processing proceeds.

  Further, as can be seen from FIG. 7, the natural frequency of the moving object also changes depending on the position of the moving object. The machine tool 100 according to the second embodiment sets the natural frequency of the filter processing unit 14 in consideration of such a change in the natural frequency of the moving object due to the position of the moving object.

  For example, a plurality of positions of the moving object are changed in advance, and the natural frequency of the moving object is measured by a hammering test or the like. The measured natural frequency is stored in the parameter setting unit 51. The natural frequency at the measured position and the natural frequency at other positions are interpolated by an interpolation method such as linear interpolation, linear interpolation, Lagrangian interpolation or the like. In the example of FIG. 7, the natural frequencies (natural frequencies ωA to ωE) are measured at five locations XA to XE, and each natural frequency is interpolated by linear interpolation to obtain the third natural frequency at an arbitrary position. . The natural frequency calculation unit 55 may calculate the natural frequency of the moving object by changing a plurality of positions of the moving object in advance.

  The case of an arbitrary position Xa in FIG. 7 will be described as an example.

となり、また、加工前または加工開始当初の加速度Ａおよびトルク演算値Ｔを式３に適用して固有振動数演算部５５で演算した第１固有振動数をω１、加工途中（Ｘａの位置）の移動物の加速度Ａおよびトルク演算値Ｔを式３に適用して固有振動数演算部５５で演算した加工途中の第２固有振動数をω２とすると、フィルタ処理部１４で減衰させる第４固有振動数ω４は、ω４＝ω３×ω２／ω１となる。 The third natural frequency ω3 at an arbitrary position Xa is linearly interpolated between ωC to ωD.

Further, the first natural frequency calculated by the natural frequency calculation unit 55 by applying the acceleration A and the torque calculation value T before processing or at the beginning of processing to Equation 3 is ω1, and is in the middle of processing (position Xa). The fourth natural vibration to be attenuated by the filter processing unit 14 when the second natural frequency in the middle of processing, which is calculated by the natural frequency calculation unit 55 by applying the acceleration A and the torque calculation value T of the moving object to Equation 3, is ω2. The number ω4 is ω4 = ω3 × ω2 / ω1.

  In this way, the third natural frequency at an arbitrary position is obtained in advance, and the first natural frequency ω1 of the moving object before processing or at the start of processing and the second natural frequency ω2 of the moving object during processing are processed. By correcting using the ratio (ω2 / ω1), the fourth natural frequency ω4 of the moving object being processed at the position can be calculated.

  The machine tool 100 according to the second embodiment considers a change in the natural frequency due to the weight M of the moving object and a change in the natural frequency due to the position of the moving object. Can be calculated. Therefore, the machine tool 100 according to the second embodiment can calculate a more accurate natural frequency of the moving object.

(Modification)
The machine tool 100 according to the second embodiment has a drive mechanism 2 that moves a moving object in the X-axis direction. On the other hand, the machine tool 100 according to this modification includes a drive mechanism that moves the moving object in the X-axis direction and a drive mechanism that moves the moving object in the Y-axis direction. The X axis and the Y axis are orthogonal to each other in the horizontal plane. That is, the drive mechanism 2 according to this modification can move the moving object in the horizontal plane.

  Even if the natural frequency ω of the moving object according to the position in the X-axis direction is determined without considering the Y-axis direction and the natural frequency of the filter processing unit 14 is set, the natural vibration may not be suppressed. In some cases, the natural vibration in the Y-axis direction may affect the natural vibration in the X-axis direction. Therefore, the machine tool 100 according to the present modification calculates the natural frequency ω of the moving object in consideration of the positions in both the X-axis direction and the Y-axis direction.

  For example, in this modification, the natural frequency is measured at a plurality of positions while moving the moving object in both the X-axis direction and the Y-axis direction before processing or at the beginning of processing. Thereafter, the natural frequencies between the plurality of positions are interpolated using the natural frequencies at the plurality of positions. Thereby, the natural frequency calculating unit 55 can calculate the third natural frequency ω3 at an arbitrary position in the horizontal plane. The interpolation may be either linear interpolation or Lagrange interpolation.

  Further, as in the second embodiment, the natural frequency calculator 55 is a ratio of the first natural frequency ω1 of the moving object before processing or at the beginning of processing to the second natural frequency ω2 of the moving object in the middle of processing. By calculating (ω2 / ω1) and correcting the third natural frequency ω3, the fourth natural frequency ω4 of the moving object in the middle of processing at an arbitrary position in the horizontal plane can be calculated.

  As described above, even when the moving object is moved in the horizontal plane, the machine tool 100 according to the present modification takes into consideration the change in the natural frequency due to the weight M of the moving object and the change in the natural frequency due to the position of the moving object. Thus, the natural frequency of the moving object in the middle of processing at an arbitrary position can be calculated. In addition, this modification can also be extended to three dimensions including the Z axis which is the vertical direction.

  At least a part of the vibration suppressing method in the machine tool according to the present embodiment may be configured by hardware or software. When configured by software, a program for realizing at least a part of the functions of the method may be stored in a recording medium such as a flexible disk or a CD-ROM, and read and executed by a computer. The recording medium is not limited to a removable medium such as a magnetic disk or an optical disk, but may be a fixed recording medium such as a hard disk device or a memory. A program that realizes at least a part of the function of the vibration suppression method may be distributed via a communication line (including wireless communication) such as the Internet. Further, the program may be distributed in a state where the program is encrypted, modulated or compressed, and stored in a recording medium via a wired line such as the Internet or a wireless line.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

100 machine tools, 11 motors, 12 servo control units, 14 filter processing units, 1 servo units, 2 drive mechanisms, 3 tables, 5 main control units, 51 parameter setting units, 52 program analysis units, 53 trajectory generation units, 54 weights Calculation unit, 55 natural frequency calculation unit, 6 machining program, M moving object weight, ω moving object natural frequency, A moving object acceleration, T motor torque, ω1 first natural frequency, ω2 second natural frequency Frequency, ω3 3rd natural frequency, ω4 4th natural frequency

Claims (15)

A drive mechanism for moving a moving object including a work and a table on which the work can be placed;
A servo unit having a motor for operating the drive mechanism and a servo control unit for controlling the motor;
A weight calculating unit for calculating the weight of the moving object during processing of the workpiece, a natural frequency calculating unit for calculating a natural frequency of the moving object based on the weight of the moving object, and for processing the workpiece A parameter setting unit that sets and stores the parameters, a program analysis unit that analyzes a machining program, and a main control unit that includes a trajectory generation unit that generates a trajectory in which the drive mechanism moves,
The servo unit or the main control unit is a machine tool further including a filter processing unit that attenuates vibrations in a natural frequency band of the moving object.   The machine tool according to claim 1, wherein the main control unit calculates a weight of the moving object based on an acceleration of the moving object and a torque value of the motor.   The main control unit receives the position information of the moving object and the torque value or the current value for controlling the motor from the servo unit, calculates the acceleration from the position information, and receives the current value The machine tool according to claim 2, wherein the torque value is calculated from the current value.   The main control unit analyzes in advance an unexecuted portion of the workpiece machining program that has not yet been executed during machining of the workpiece, and accelerates the distance of the moving object within a predetermined value of the unexecuted portion. The machine tool according to claim 2 or 3, wherein a first block that decelerates is detected, and a weight of the moving object is calculated based on the acceleration and the torque value obtained by executing the first block. machine.   The main control unit changes the setting of the natural frequency of the filter processing unit based on the weight of the moving object before or during execution of any block after the first block in the unexecuted portion. The machine tool according to claim 4.   The main control unit calculates a ratio between the first natural frequency of the moving object before processing or at the start of processing and the second natural frequency of the moving object during processing, and uses the ratio to set an arbitrary position. By correcting the third natural frequency of the moving object in step S4, the fourth natural frequency of the moving object in the middle of processing at the arbitrary position is calculated, and the vibration of the fourth natural frequency is attenuated. The machine tool according to claim 1, wherein the machine tool is set in the filter processing unit.   The machine tool according to claim 6, wherein the main control unit calculates the fourth natural frequency at the arbitrary position by multiplying the third natural frequency at the arbitrary position by the ratio.   The main control unit calculates or measures the natural frequency at a plurality of positions in advance and calculates the third natural frequency at the arbitrary position by interpolating the natural frequency between the plurality of positions. A machine tool according to claim 6 or claim 7.   The machine tool according to claim 8, wherein the main control unit calculates the third natural frequency at the arbitrary position by linearly interpolating natural frequencies between the plurality of positions.   The machine tool according to claim 8, wherein the main control unit calculates the third natural frequency at the arbitrary position by performing linear interpolation or Lagrange interpolation on the natural frequency between the plurality of positions. A servo unit having a drive mechanism for moving a moving object including a workpiece and a table on which the workpiece can be placed; a motor for operating the drive mechanism; and a servo control unit for controlling the motor; A main control unit that outputs a position command, and a vibration suppression method for the moving object in a machine tool comprising:
Calculate the weight of the moving object during machining of the workpiece,
Calculate the natural frequency of the moving object based on the weight of the moving object,
A vibration suppression method including a filter processing unit so as to attenuate vibrations in the natural frequency band of the moving object.   The vibration suppression method according to claim 11, wherein the weight of the moving object is calculated based on an acceleration of the moving object and a torque value of the motor. Before calculating the weight of the moving object,
Receiving the position information of the moving object and the torque value or the current value for controlling the motor from the servo unit;
The vibration suppression method according to claim 12, wherein the acceleration is calculated from the position information, and the torque value is calculated from the current value when the current value is received. Before receiving the position information and the torque value or the current value from the servo control unit,
During machining of the workpiece, analyze in advance an unexecuted portion of the machining program for the workpiece that has not yet been executed,
Detecting a first block in which the moving object accelerates or decelerates a distance equal to or greater than a predetermined value in the unexecuted portion;
The vibration suppressing method according to claim 13, wherein the weight of the moving object is calculated based on the acceleration and the torque value obtained by executing the first block. Calculating the ratio between the first natural frequency of the moving object before processing or at the start of processing and the second natural frequency of the moving object during processing;
Calculating the fourth natural frequency of the moving object during processing at the arbitrary position by correcting the third natural frequency of the moving object at the arbitrary position using the ratio;
The vibration suppression method according to claim 11, wherein the filter processing unit is set to attenuate the vibration of the fourth natural frequency.

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