Ball screw thermal displacement correction amount calculation device and correction amount calculation method

Abstract

Improve the accuracy of estimating thermal displacement. A correction amount calculation device calculates a correction amount for thermal displacement using a thermal displacement estimation formula that estimates thermal displacement of a ball screw of a machine tool, the correction amount calculation device comprising: a feed axis operation information acquisition unit that acquires feed axis operation information related to feed axis operation of a feed axis including a ball screw from the machine tool; a temperature information acquisition unit that acquires temperature information related to the ball screw from the machine tool; a first variable determination unit that determines a first variable that represents a thermal response characteristic of the ball screw that is not related to changes in ambient temperature of the ball screw, based on the feed axis operation information; a second variable determination unit that determines a second variable that represents a thermal response characteristic of the ball screw that is related to changes in ambient temperature of the ball screw, based on the feed axis operation information, and is included in the thermal displacement estimation formula; and a correction amount calculation unit that calculates a correction amount for thermal displacement from the thermal displacement estimation formula, based on the feed axis operation information, the temperature information, the first variable, and the second variable.

Description

[Technical Field]

[0001] The present disclosure relates to a correction amount calculation device and a correction amount calculation method for thermal displacement of a ball screw, and in particular to a correction amount calculation device and a correction amount calculation method for calculating a correction amount for thermal displacement of a ball screw using a thermal displacement estimation formula for estimating thermal displacement of a ball screw of a machine tool. [Background technology]

[0002] Techniques for determining thermal displacement in a machine tool based on temperature information are described in, for example, Patent Documents 1 and 2. Patent Document 1 describes a thermal displacement correction device that can perform high-precision correction of machining errors caused by thermal displacement. Specifically, Patent Document 1 describes that a thermal displacement correction device uses a temperature sensor to detect temperature changes in a machine body affected by a heat source, calculates a calculated temperature change using the detected temperature change based on a differential equation that calculates a calculated temperature change that behaves approximately the same as the thermal behavior of the thermal displacement of the machine tool from the detected temperature change, and corrects machining errors based on the thermal displacement that changes in response to this calculated temperature change.

[0003] Patent Document 2 describes a machine tool that can relatively easily estimate the thermal displacement of a support stand even when the temperature distribution of the support stand that supports a bearing is complex. Specifically, Patent Document 2 describes a grinding machine including a wheel head main body supporting a rotating shaft member connected to a grinding wheel, an X-axis threaded shaft, an X-axis nut member, and a connecting member connecting the wheel head main body 1 and the X-axis nut member, wherein a wheel head connection portion of the connecting member connected to the wheel head main body and a nut connection portion of the connecting member connected to the X-axis nut member are located at different positions along an axis L1 of the X-axis threaded shaft, the wheel head connection portion is arranged to overlap with the position of an axis L2 of the rotating shaft member on the axis L1 in a direction perpendicular to the axis L1, and the connecting member is configured to align thermal displacement along the axis L1. Patent Document 2 also describes a machine tool control device including a thermal displacement estimation portion that estimates thermal displacement of the connecting member in the axial direction of the threaded shaft based on detection results from a temperature sensor, and a movement correction portion that corrects the movement of the nut member based on the estimation result from the thermal displacement estimation portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-108992 [Patent Document 2] Japanese Patent Application Publication No. 2017-19022 Summary of the Invention [Problem to be solved by the invention]

[0005] In machine tools, when the thermal displacement of a ball screw is estimated from temperature information, the accuracy of the estimation may be reduced due to the influence of the thermal response characteristics of the ball screw in response to changes in the ambient temperature.

[0006] Therefore, there is a need for a device and method for calculating the amount of correction for the thermal displacement of a ball screw that can calculate the thermal displacement of the ball screw taking into account the thermal response characteristics of the ball screw in response to changes in ambient temperature. [Means for solving the problem]

[0007] A first representative aspect of the present disclosure is a correction amount calculation device that calculates a thermal displacement correction amount of a ball screw of a machine tool using a thermal displacement estimation formula that estimates the thermal displacement of the ball screw, a feed axis operation information acquisition unit that acquires feed axis operation information relating to the feed axis operation of the feed axis including the ball screw from the machine tool; a temperature information acquisition unit that acquires temperature information related to the ball screw from the machine tool; a first variable determination unit that determines a first variable that is included in the thermal displacement estimation formula and that represents a thermal response characteristic of the ball screw that is not related to a change in the ambient temperature of the ball screw, based on the feed axis operation information; a second variable determination unit that determines a second variable that is included in the thermal displacement estimation formula and that represents a thermal response characteristic of the ball screw related to a change in ambient temperature of the ball screw, based on the feed axis operation information; a correction amount calculation unit that calculates the thermal displacement correction amount of the ball screw from the thermal displacement estimation formula based on the feed axis operation information, the temperature information, the first variable, and the second variable; The correction amount calculation device includes:

[0008] A second exemplary aspect of the present disclosure is a computer-implemented method for implementing a method of processing a program, comprising: acquiring, from the machine tool, feed axis operation information relating to the operation of a feed axis including a ball screw of the machine tool; acquiring temperature information relating to the ball screw from the machine tool; determining a first variable representing a thermal response characteristic of the ball screw independent of a change in ambient temperature of the ball screw, the first variable being included in a thermal displacement estimation formula for estimating a thermal displacement of the ball screw based on the feed axis operation information; determining a second variable representing a thermal response characteristic of the ball screw related to a change in ambient temperature of the ball screw, the second variable being included in the thermal displacement estimation formula based on the feed axis operation information; calculating a thermal displacement compensation amount of the ball screw from the thermal displacement estimation formula based on the feed axis operation information, the temperature information, the first variable, and the second variable; This is a correction amount calculation method that executes the above. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram illustrating a ball screw thermal displacement correction amount calculation device according to a first embodiment of the present disclosure. FIG. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of a feed axis of a machine tool. [Figure 3] FIG. 10 is a block diagram showing a partial configuration of a modified example of a correction amount calculation device during machine learning. [Figure 4] FIG. 10 is a block diagram illustrating a partial configuration of a modified example of the correction amount calculation device after machine learning. [Figure 5] 4 is a flowchart illustrating an example of a correction amount calculation method according to the first embodiment. [Figure 6] FIG. 10 is a block diagram illustrating a ball screw thermal displacement correction amount calculation device according to a second embodiment of the present disclosure. [Figure 7] FIG. 2 is a diagram showing each section into which the moving range of the feed axis of the ball screw is divided. [Figure 8] 10 is a diagram showing the correction amount for each section calculated by the section-by-section correction amount calculation unit and the total correction amount calculated by the correction amount calculation unit. FIG. [Figure 9] FIG. 10 is a block diagram illustrating a ball screw thermal displacement correction amount calculation device according to a third embodiment of the present disclosure. [Figure 10] FIG. 10 is a diagram showing a table showing pairs of feed axis discrimination information, table positions, coefficients, and time delays. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] (First embodiment) FIG. 1 is a block diagram showing a ball screw thermal displacement correction amount calculation device according to a first embodiment of the present disclosure. The correction amount calculation device 10 is connected to a machine tool 20. The machine tool 20 includes a control object 21 including a feed axis including a ball screw, and a control device 22 that controls the operation of the feed axis. The control device 22 outputs feed axis operation information to the correction amount calculation device 10. The control device 22 may be provided separately from the machine tool 20 and connected to the machine tool 20. The machine tool 20 outputs temperature information related to the ball screw from a temperature sensor (not shown) or the like to the correction amount calculation device 10. The correction amount calculation device 10 outputs a correction amount for the ball screw thermal displacement to the control device 22. The control device 22 corrects the feed axis operation based on the correction amount for the ball screw thermal displacement. The correction amount calculation device 10 may be provided within the machine tool 20.

[0012] As shown in FIG. 1, the correction amount calculation device 10 includes a temperature information acquisition unit 101, a feed axis operation information acquisition unit 102, a first variable determination unit 103, a second variable determination unit 104, and a correction amount calculation unit 105. The temperature information acquisition unit 101 acquires temperature information relating to the ball screw of the machine tool 20 from the machine tool 20 . The feed axis operation information acquisition unit 102 acquires feed axis operation information relating to the feed axis operation of the machine tool 20 from the machine tool 20 .

[0013] Based on the feed axis operation information, the first variable determination unit 103 determines a coefficient and an index (which become a first variable) included in the thermal displacement estimation formula that represent the thermal response characteristics of the ball screw regardless of changes in the ambient temperature of the ball screw. The second variable determination unit 104 determines a coefficient and a delay (which becomes a second variable) that represent the thermal response characteristics of the ball screw related to changes in the ambient temperature of the ball screw and are included in the thermal displacement estimation formula based on the feed axis operation information. The delay is a time delay that takes into account the influence of changes in the ambient temperature.

[0014] The correction amount calculation unit 105 calculates the thermal displacement correction amount of the ball screw from the thermal displacement estimation formula based on the feed axis operation information, temperature information, the coefficient and index determined by the first variable determination unit 103, and the coefficient and delay determined by the second variable determination unit, and outputs the thermal displacement correction amount of the ball screw to the control device 22.

[0015] FIG. 2 is a block diagram showing an example of the configuration of a feed axis of a machine tool. 2, the feed axis included in the control object 21 controlled by the control device 22 includes a servo motor 201, a rotary encoder 202, a coupling 203, a ball screw 204, a nut 205, and a table 206. The coupling 203, the ball screw 204, and the nut 205 form a coupling mechanism that connects the servo motor 201 and the table 206. The control device 22 controls the machining of a workpiece (workpiece) placed on the table 206 by moving the table 206 via the coupling mechanism using the servo motor 201.

[0016] The servo motor 201 is a motor having a rotating shaft, and the rotation angle position is detected by a rotary encoder 202, and the detected position value is input to the control device 22 as position feedback.

[0017] The operation of the correction amount calculation device 10 will be further described in detail below.

[0018] The temperature information acquisition unit 101 acquires the ambient temperature of the ball screw, which becomes temperature information related to the ball screw, from a temperature sensor (not shown) of the machine tool 20. The temperature sensor is installed at one or more locations where it can detect changes in the ambient temperature of the ball screw, and the temperature information may be one or more. For example, the temperature sensor is arranged around the ball screw 204 shown in FIG. 2 and on a part of the structure of the machine tool, such as one or both of the nut 205 and the table 206. In this case, the temperature information related to the ball screw includes at least one of the ambient temperature of the ball screw 204 and the temperature of a part of the structure of the machine tool 20.

[0019] The feed axis operation information acquisition unit 102 acquires feed axis operation information relating to feed axis operation from the control device 22. The feed axis operation information includes at least one of discrimination information, position, speed, acceleration, and torque of the feed axis of the machine tool 20. The feed axis discrimination information is, for example, information for discriminating between the X-axis, Y-axis, and Z-axis.

[0020] The first variable determination unit 103 determines a coefficient and an index representing the thermal response characteristics of the ball screw that are not related to changes in ambient temperature, for example, based on the X-axis as feed axis discrimination information and the X-axis speed, which are feed axis operation information. Specifically, the first variable determination unit 103 determines the values ​​of coefficients A and B and indexes a and b (which become first variables) of a thermal displacement estimation formula for estimating thermal displacement, which is shown in Equation 1 (hereinafter, Equation 1), as variables representing the thermal response characteristics of the ball screw that are not related to changes in ambient temperature.

[0021] The second variable determination unit 104 determines a coefficient and delay representing the thermal response characteristics of the ball screw related to ambient temperature changes, for example, based on the X-axis as feed axis discrimination information and the X-axis speed, which are feed axis operation information. Specifically, the second variable determination unit 104 determines the values ​​of the coefficient C and delay D (which becomes the second variable) of the thermal displacement estimation formula for estimating thermal displacement, shown in Equation 1, as variables representing the thermal response characteristics of the ball screw related to ambient temperature changes.

[0022]

number

[0023] The variables included in Equation 1 will be explained below. In Equation 1, the variable δ(t) indicates the elongation (axial displacement) of the ball screw at time t, and the variable δ(t-1) indicates the elongation of the ball screw at time (t-1) before time t. The variable δ(t) indicates the amount of axial deformation mainly due to thermal expansion or mechanical load, and the variable δ(t-1) indicates that the current elongation amount depends on the past state. The variable V(t) indicates the ball screw feed speed at time t. The variable V(t) indicates that high-speed rotation or high-speed feed increases heat generation and affects elongation. The variable F(t) is a quantity that indicates the effect of ambient temperature change at time t. The variable F(t-1) is a quantity that indicates the effect of ambient temperature change at time (t-1) before time t. The variable T(t) is the ambient temperature at time t, and the variable T(tD) is the ambient temperature a time (delay) D before time t.

[0024] In Equation 1, coefficient A is a speed-dependent coefficient, a constant that determines the effect of the ball screw feed rate on elongation. Coefficient B is a damping coefficient for past elongation, a constant that scales the natural contraction and elastic restoring force of the ball screw. Index a represents the nonlinearity with respect to speed; for example, if a > 1, this means that the thermal expansion increases at an accelerated rate as the speed increases. Index b represents the nonlinearity of the damping characteristics; for example, if b > 1, this means that the damping effect increases as the past elongation increases.

[0025] In Equation 1, coefficient C is the sensitivity coefficient to ambient temperature changes, and lag D is a time lag that takes into account the impact of ambient temperature changes. Coefficient C and lag D are coefficients and time that indicate thermal response characteristics. Coefficient C and lag D can be determined from cumulative ambient temperature changes. Cumulative temperature changes are time-series information, so past temperatures must be referenced, and are determined by appropriately determining the number of reference points and cycles for past temperatures.

[0026] The thermal displacement estimation formula shown in Equation 1 includes the quantity F(t) that indicates the influence of ambient temperature changes, thereby achieving the following effects. (1) Consideration of temperature change history Since the ambient temperature T(tD) D seconds before is taken into consideration, it is possible to reflect the influence of sudden temperature changes or temperature fluctuation patterns. (2) Reflection of cumulative effects By using the ambient temperature D seconds ago, the current expansion can be calculated from the past expansion, accurately representing the cumulative effect of expansion over time. (3) Reflection of material properties By adjusting the coefficient C, it is possible to reflect the thermal expansion characteristics of different metal materials. (4) Consideration of delay effects By adjusting the delay D, it is possible to take into account the delay time until the temperature change affects the elongation of the metal rod, and to express the delay in heat conduction in large metal structures or parts with complex shapes.

[0027] The correction amount calculation unit 105 stores the thermal displacement estimation formula shown in Equation 1, and calculates the thermal displacement correction amount of the ball screw from the thermal displacement estimation formula of Equation 1 based on the feed axis operation information, temperature information, variables (coefficients and exponents) determined by the first variable determination unit 103, and variables (coefficients and delays) determined by the second variable determination unit 104, and outputs the thermal displacement correction amount of the ball screw to the control device 22.

[0028] In this embodiment, when the correction amount calculation unit 105 calculates the thermal displacement, it estimates the effect on the thermal displacement of frictional heat and the like generated by the feed axis operation from the feed axis discrimination information and feed axis operation information such as speed, and also estimates the effect on the thermal displacement of ambient temperature changes obtained from temperature information.

[0029] (Methods for calculating coefficients, exponents and delays) The first variable determination unit 103 and the second variable determination unit 104 can determine the coefficient A, coefficient B, index a, index b, coefficient C, and delay D of the thermal displacement estimation formula shown in Equation 1 based on the feed axis operation information by any of the following methods (1) to (3). The first variable determination unit 103 stores a table indicating the correspondence between the feed axis operation information and the determined coefficient A, coefficient B, index a, and index b. The second variable determination unit 104 stores a table indicating the correspondence between the feed axis operation information and the determined coefficient C and delay D. (1) Collection and analysis of experimental data The values ​​of coefficient A, coefficient B, index a, index b, coefficient C, and delay D are estimated by statistically analyzing collected data on the amount of elongation of the ball screw and collected data on changes in ambient temperature when at least one of the position, speed, acceleration, and torque of the feed axis, which constitutes feed axis operation information, is changed.

[0030] (2) Utilizing machine learning Using the collected data, the optimal values ​​of coefficient A, coefficient B, index a, index b, coefficient C, and delay D in the thermal displacement estimation formula shown in Equation 1 are estimated. The method for determining each coefficient, index, and delay using machine learning will be described later.

[0031] (3) Numerical simulation Using software that simulates the heat conduction or deformation of the ball screw, the values ​​of coefficient A, coefficient B, index a, index b, coefficient C, and delay D are adjusted while comparing the simulation results with the actual measurement data.

[0032] The thermal response characteristics represented by coefficient A, coefficient B, index a, index b, coefficient C, and delay D in Equation 1 vary depending on the ball screw design (diameter or pitch) and material. Changes in the ball screw diameter or pitch affect the surface area and contact area with the surroundings, which in turn affects heat dissipation. A larger surface area improves heat dissipation efficiency and potentially reduces temperature rise. While chrome-molybdenum steel (SCM420, SCM415) is typically used for the screw shaft and nut, stainless steel (SUS440C) is used for special environmental applications, and these materials have different thermal response characteristics. When calculating coefficient A, coefficient B, index a, index b, coefficient C, and delay D using the three methods above, the ball screw design (diameter or pitch) and material are reflected. For example, if the surface area and contact area change depending on the ball screw design, coefficient C will change due to the influence of ambient temperature.

[0033] The three methods described above may be combined as appropriate to determine the coefficients, exponents, and lags of the first variable determination unit 103 and the second variable determination unit 104. For example, the coefficients, exponents, and lags of the first variable determination unit 103 and the second variable determination unit 104 may be determined by utilizing machine learning in method (2), or the coefficients and exponents of the first variable determination unit 103 may be determined by collecting and analyzing experimental data in method (1), and the coefficients and lags of the second variable determination unit 104 may be determined by utilizing machine learning in method (2).

[0034] (Evaluation method of calculated coefficients, indices and lags) The calculated coefficient, index, and delay may be inserted into the thermal displacement estimation formula (Equation 1), and the difference between the estimated thermal displacement calculated using the thermal displacement estimation formula and the actual thermal displacement of the collected data may be used as the coefficient evaluation value, and the coefficient, index, and delay may be evaluated based on the evaluation value. If the calculated evaluation value is greater than a threshold, the coefficient, index, and delay may be calculated again using one of the three methods for calculating the coefficient, index, and delay described above. If the calculated evaluation value is equal to or less than the threshold, a table showing the correspondence between the feed axis operation information and coefficient A, coefficient B, index a, and index b is stored in first variable determination unit 103, and a table showing the correspondence between the feed axis operation information and coefficient C and delay D is stored in second variable determination unit 104.

[0035] (Modification of the correction amount calculation device when coefficients, exponents, and delays are calculated using machine learning) Fig. 3 is a block diagram showing a partial configuration of a modified correction amount calculation device during machine learning. Fig. 4 is a block diagram showing a partial configuration of a modified correction amount calculation device after machine learning. The correction amount calculation device shown in Figs. 3 and 4 has a machine learning unit 106 added to the correction amount calculation device 10 shown in Fig. 1. The temperature information acquisition unit 101 is omitted in Figs. 3 and 4.

[0036] During machine learning, the machine learning unit 106 acquires temperature information from the temperature information acquisition unit 101, acquires feed axis operation information from the feed axis operation information acquisition unit 102, and acquires the calculated thermal displacement compensation amount of the ball screw from the compensation amount calculation unit 105. The temperature information, feed axis operation information, and thermal displacement compensation amount become input data. The machine learning unit 106 stores, as labels, the actual measurement data of the elongation amount of the ball screw when at least one of the position, speed, acceleration, and torque of the feed axis, which becomes the feed axis operation information, is changed.

[0037] The machine learning unit 106 learns the coefficient A, the coefficient B, the index a, the index b, the coefficient C, and the delay D so that the difference between the actual measurement data of the elongation amount of the ball screw in response to the temperature information and the feed axis operation information and the thermal displacement correction amount calculated by the correction amount calculation unit 105 is equal to or less than a predetermined threshold. The machine learning unit 106 outputs the coefficient A, the coefficient B, the index a, the index b, the coefficient C, and the delay D obtained by learning to the first variable determination unit 103 and the second variable determination unit 104, and then ends the learning operation.

[0038] The machine learning unit 106 does not calculate the thermal displacement correction amount after the machine learning. In Fig. 4, the paths connected to the machine learning unit 106 are indicated by dashed lines, which means that the machine learning unit 106 does not function after learning.

[0039] The machine learning unit 106 may determine the coefficients, exponents, and lags of the first variable determination unit 103 and the second variable determination unit 104, or when the method for determining the coefficients, exponents, and lags is a combination of method (2) using the machine learning unit 106 and method (1) or method (3), the machine learning unit 106 may determine the coefficients and exponents of the first variable determination unit 103 or the coefficients and lags of the second variable determination unit 104.

[0040] Next, an example of a correction amount calculation method according to the first embodiment of the present disclosure will be described. 5 is a flowchart showing an example of the correction amount calculation method according to the first embodiment. In the following description, an example will be described in which the correction amount calculation method according to the present disclosure is executed by the correction amount calculation device 10, but the correction amount calculation method according to the present disclosure can also be executed by a configuration other than the correction amount calculation device 10.

[0041] In step S11, the temperature information acquisition unit 101 acquires temperature information relating to the ball screw of the machine tool 20 from the machine tool 20.

[0042] In step S12, the feed axis operation information acquisition unit 102 acquires feed axis operation information relating to the feed axis operation of the machine tool 20 from the machine tool 20.

[0043] In step S13, the first variable determination unit 103 determines the coefficients A and B and the exponents a and b that represent the thermal response characteristics of the ball screw independent of changes in ambient temperature, based on the feed axis operation information.

[0044] In step S14, the second variable determination unit 104 determines a coefficient C and a delay D that represent the thermal response characteristics of the ball screw related to changes in ambient temperature, based on the feed axis operation information.

[0045] In step S15, the correction amount calculation unit 105 calculates the thermal displacement correction amount of the ball screw from the thermal displacement estimation formula (Equation 1) based on the feed axis operation information, temperature information, coefficients A and B and exponents a and b determined by the first variable determination unit, and coefficient C and delay D determined by the second variable determination unit, and then ends the processing.

[0046] According to the correction amount calculation device and correction amount calculation method of the present embodiment described above, the thermal response characteristics of the ball screw in response to changes in ambient temperature, which are determined by the design or material of the ball screw, are taken into consideration when calculating the thermal displacement, thereby improving the accuracy of estimating the thermal displacement.

[0047] (Second embodiment) Fig. 6 is a block diagram showing a ball screw thermal displacement correction amount calculation device according to a second embodiment of the present disclosure. In the correction amount calculation device 11 of this embodiment shown in Fig. 6, the correction amount calculation unit 105 of the correction amount calculation device 10 shown in Fig. 1 is provided with a section-by-section correction amount calculation unit 107, a section detection unit 108, and a correction amount total calculation unit 109. In Fig. 6, the machine tool 20 is not shown.

[0048] In this embodiment, the first variable determination unit 103 determines the values ​​of the coefficients A and B and the exponents a and b in Equation 2 described below, as well as the value of the coefficient E that represents the thermal response characteristics of the ball screw, regardless of changes in ambient temperature.

[0049] The section detection unit 108 detects the section of the feed axis of the ball screw from the feed axis operation information. For example, the section detection unit 108 detects sections into which the movement range of the X axis from the reference position is divided from the feed axis operation information output from the control device 22, and outputs each detected section to the correction amount calculation unit 105. FIG. 7 is a diagram showing each section into which the movement range of the feed axis of the ball screw is divided. In FIG. 7, X1, X2, X3, ... indicate each divided section.

[0050] The section-by-section correction amount calculation unit 107 detects sections into which the movement range of the X-axis from the reference position is divided, from the feed axis operation information output from the control device 22, and calculates the correction amount for each detected section from the feed axis operation information such as speed and temperature information. The section-by-section correction amount calculation unit 107 may calculate the correction amount for each section from the feed axis operation information and temperature information, using each section output from the section detection unit 108. The correction amount for each divided section is found by Equation 2 (Equation 2 below).

number

[0051] The correction amount total calculation unit 109 calculates the thermal displacement correction amount by summing the correction amounts for each section from the reference position to the movement range of the feed axis from the correction amount for each section and the section of the feed axis. Fig. 8 is a diagram showing the correction amount for each section calculated by the section correction amount calculation unit 107 and the sum of the correction amounts calculated by the correction amount total calculation unit 109.

[0052] According to the ball screw thermal displacement correction amount calculation device and correction document calculation method of this embodiment, it is possible to improve estimation accuracy when the heat distribution is non-uniform (which occurs when the table is moved locally, for example).

[0053] (Third embodiment) Fig. 9 is a block diagram showing a ball screw thermal displacement correction amount calculation device according to a third embodiment of the present disclosure. The correction amount calculation device 12 of this embodiment shown in Fig. 9 has a memory unit 110 added to the configuration of the correction amount calculation device 10 shown in Fig. 1. In Fig. 6, the machine tool 20 is omitted.

[0054] The storage unit 110 stores a table describing a plurality of feed axis operation information items under different conditions and a plurality of different coefficients C and delays D associated with the thermal displacement estimation formula of Equation 1, each corresponding to the plurality of feed axis operation information items. For example, the storage unit 110 stores a table shown in FIG. 10 that shows a plurality of different sets of feed axis discrimination information items and table positions (feed axis positions) and a plurality of different coefficients C and delays D corresponding to the plurality of feed axis discrimination information items and table positions. The feed axis discrimination information and table positions constitute the feed axis operation information. As shown in FIG. 10, the coefficients C and delays D are set to different values ​​corresponding to the feed axis discrimination information and table positions (feed axis positions).

[0055] Based on the feed axis operation information, the second variable determination unit 104 refers to the storage unit 110 and determines a coefficient C and a delay D that represent the thermal response characteristics of the ball screw. For example, if the feed axis discrimination information is the X axis and the table position is 500 mm (center), the second variable determination unit 104 refers to the storage unit 110 and determines a coefficient C2 and a delay D2.

[0056] (How to calculate coefficient C and delay D) The coefficient C and delay D can be calculated using the following method. (1) Collection of experimental data The thermal displacement of the ball screw and the change in ambient temperature are measured at different table positions, and the time delay between the thermal displacement and the change in ambient temperature at each position is observed to estimate the value of the delay D. (2) Utilizing machine learning Using the collected data, the relationship between the table position and the coefficient C and delay D is modeled, and the values ​​of coefficient C and delay D at any position are predicted through a machine learning model. (3) Heat conduction simulation The thermal conduction characteristics of the ball screw are modeled, the temperature distribution at each position is simulated, and the values ​​of the coefficient C and delay D for each position are estimated.

[0057] According to the ball screw thermal displacement correction amount calculation device and correction document calculation method of this embodiment, the estimation accuracy is improved by taking into account the influence of ambient temperature changes for each table position.

[0058] Each component included in the correction amount calculation device of each of the above-described embodiments and modifications can be realized by hardware, software, or a combination thereof. Furthermore, the correction amount calculation method performed by the cooperation of each component included in the correction amount calculation device of each of the above-described embodiments and modifications can also be realized by hardware, software, or a combination thereof. Here, "realized by software" means that the method is realized by a computer reading and executing a program.

[0059] To realize the components included in the correction amount calculation device using hardware, software, or a combination of these, the correction amount calculation device includes a processing unit such as a CPU (Central Processing Unit). The processing unit functions as an execution unit. The correction amount calculation device also includes a secondary storage device such as an HDD (Hard Disk Drive) that stores various control programs such as application software or an OS (Operating System), and a main storage device such as a RAM (Random Access Memory) that stores data temporarily required for the processing unit to execute the programs.

[0060] In the correction amount calculation device, the arithmetic processing unit reads application software or an OS from the auxiliary storage device, and while loading the read application software or OS into the main storage device, performs arithmetic processing based on the application software or the OS. Furthermore, based on the results of this calculation, various pieces of hardware included in the correction amount calculation device are controlled. In this way, the functional blocks of each embodiment and modification are realized. Furthermore, the correction amount calculation method can also be realized by a configuration similar to that of the correction amount calculation device.

[0061] The components included in the correction amount calculation device can be realized by hardware including electronic circuits, etc. When the correction amount calculation device is configured by hardware, some or all of the functions of the components included in the correction amount calculation device can be configured by an integrated circuit (IC), such as an ASIC (Application Specific Integrated Circuit), a gate array, an FPGA (Field Programmable Gate Array), or a CPLD (Complex Programmable Logic Device).

[0062] The program can be stored and supplied to a computer using various types of non-transitory computer readable media. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer readable media include magnetic recording media (e.g., hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (Random Access Memory)). The program may also be supplied to a computer by various types of transitory computer readable media.

[0063] According to the correction amount calculation device and correction amount calculation method disclosed herein, including the embodiments and modified examples described above, the thermal response characteristics of the ball screw in response to changes in ambient temperature, which are determined by the design or material of the ball screw, are taken into consideration, thereby improving the accuracy of estimating the thermal displacement.

[0064] The above-described embodiments and variations are preferred embodiments of the present invention, but the scope of the present invention is not limited to the above-described embodiments alone, and the present invention can be implemented in various modified forms within the scope that does not deviate from the gist of the present invention.

[0065] The following additional notes are further disclosed regarding the above embodiment. (Appendix 1) A correction amount calculation device (10, 11, 12) for calculating a thermal displacement correction amount of a ball screw (204) using a thermal displacement estimation formula for estimating a thermal displacement of the ball screw of a machine tool (20), a feed axis operation information acquisition unit (102) that acquires feed axis operation information relating to the feed axis operation of the feed axis including the ball screw from the machine tool; a temperature information acquisition unit (101) that acquires temperature information relating to the ball screw from the machine tool; a first variable determination unit (103) that determines a first variable that is included in the thermal displacement estimation formula and that represents a thermal response characteristic of the ball screw that is not related to a change in the ambient temperature of the ball screw, based on the feed axis operation information; a second variable determination unit (104) that determines a second variable that is included in the thermal displacement estimation formula and that represents a thermal response characteristic of the ball screw related to a change in ambient temperature of the ball screw, based on the feed axis operation information; a correction amount calculation unit (105) that calculates the thermal displacement correction amount of the ball screw from the thermal displacement estimation formula based on the feed axis operation information, the temperature information, the first variable, and the second variable; A correction amount calculation device comprising:

[0066] (Appendix 2) The correction amount calculation device according to claim 1, wherein the second variable determination unit (104) determines, as the second variable, a coefficient related to changes in ambient temperature of the ball screw (204) and a delay due to the influence of changes in ambient temperature of the ball screw.

[0067] (Appendix 3) 3. The correction amount calculation device according to claim 1, wherein the feed axis operation information includes discrimination information of the feed axis of the machine tool (20) and at least one of position, speed, acceleration, and torque.

[0068] (Appendix 4) 4. The correction amount calculation device according to any one of appendices 1 to 3, wherein the temperature information relating to the ball screw (204) includes at least one of an ambient temperature of the ball screw and a temperature of a part of a structure of the machine tool (20).

[0069] (Appendix 5) A correction amount calculation device according to any one of appendices 1 to 4, comprising a machine learning unit (106) that calculates, by machine learning, at least one of the first and second variables related to the thermal displacement estimation equation, which are determined by the first variable determination unit (103) and the second variable determination unit (104).

[0070] (Appendix 6) The correction amount calculation unit (105) a section-by-section correction amount calculation unit (107) that calculates a correction amount for each section obtained by dividing the movement range of the feed shaft of the ball screw from the feed shaft operation information and the temperature information; a section detection unit (108) that detects a section of the feed shaft of the ball screw from the feed shaft operation information; a correction amount total calculation unit (109) that calculates, from the correction amount for each section and the section of the feed shaft, a sum of the correction amounts for each section from the reference position of the ball screw to the movement range of the feed shaft as the thermal displacement correction amount; 6. The correction amount calculation device according to any one of Supplementary notes 1 to 5, comprising:

[0071] (Appendix 7) a storage unit (110) that stores a plurality of the feed axis operation information items under different conditions and a plurality of different second variables that respectively correspond to the plurality of the feed axis operation information items; 7. The correction amount calculation device according to claim 1, wherein the second variable determination unit (104) determines the second variable corresponding to the feed axis operation information acquired by the feed axis operation information acquisition unit (102) by referring to the storage unit.

[0072] (Appendix 8) The computer a step of acquiring feed axis operation information relating to the operation of a feed axis including a ball screw (204) of a machine tool (20) from the machine tool; acquiring temperature information relating to the ball screw from the machine tool; determining a first variable representing a thermal response characteristic of the ball screw independent of a change in ambient temperature of the ball screw, the first variable being included in a thermal displacement estimation formula for estimating a thermal displacement of the ball screw based on the feed axis operation information; determining a second variable representing a thermal response characteristic of the ball screw related to a change in ambient temperature of the ball screw, the second variable being included in the thermal displacement estimation formula based on the feed axis operation information; calculating a thermal displacement compensation amount of the ball screw from the thermal displacement estimation formula based on the feed axis operation information, the temperature information, the first variable, and the second variable; A correction amount calculation method that performs the above. [Explanation of symbols]

[0073] 10, 11, 12 Correction amount calculation device 20 Machine tools 21 Control Object 22 Control device 101 Temperature information acquisition section 102 Feed axis operation information acquisition unit 103 First variable determination unit 104 Second variable determination unit 105 Correction amount calculation unit 106 Machine Learning Department 107 Section-by-section correction amount calculation unit 108 Section detection unit 109 Correction amount sum calculation unit 110 Storage section

Claims

1. A correction amount calculation device that calculates a thermal displacement correction amount of a ball screw of a machine tool using a thermal displacement estimation formula that estimates thermal displacement of the ball screw, a feed axis operation information acquisition unit that acquires feed axis operation information relating to the feed axis operation of the feed axis including the ball screw from the machine tool; a temperature information acquisition unit that acquires temperature information related to the ball screw from the machine tool; a first variable determination unit that determines a first variable that is included in the thermal displacement estimation formula and that represents a thermal response characteristic of the ball screw that is not related to a change in the ambient temperature of the ball screw, based on the feed axis operation information; a second variable determination unit that determines a second variable that is included in the thermal displacement estimation formula and that represents a thermal response characteristic of the ball screw related to a change in ambient temperature of the ball screw, based on the feed axis operation information; a correction amount calculation unit that calculates the thermal displacement correction amount of the ball screw from the thermal displacement estimation formula based on the feed axis operation information, the temperature information, the first variable, and the second variable; Equipped with the feed axis operation information includes identification information of a feed axis of the machine tool and at least one of a position, a speed, an acceleration, and a torque of the feed axis; The temperature information relating to the ball screw includes at least one of an ambient temperature of the ball screw and a temperature of a part of the structure of the machine tool.

2. 2. The correction amount calculation device according to claim 1, wherein the second variable determination unit determines, as the second variables, a coefficient related to a change in ambient temperature of the ball screw and a time delay due to an influence of the change in ambient temperature of the ball screw.

3. 3. The correction amount calculation device according to claim 1, further comprising a machine learning unit that calculates, by machine learning, at least one of the first and second variables related to the thermal displacement estimation formula, which are determined by the first variable determination unit and the second variable determination unit.

4. The correction amount calculation unit a section-by-section correction amount calculation unit that calculates a correction amount for each section obtained by dividing a movement range of the feed shaft of the ball screw from the feed shaft operation information and the temperature information; a section detection unit that detects a section of the feed shaft of the ball screw from the feed shaft operation information; a correction amount total calculation unit that calculates, as the thermal displacement correction amount, a sum of the correction amounts for each section from a reference position of the ball screw to a movement range of the feed shaft, based on the correction amount for each section and the section of the feed shaft; The correction amount calculation device according to claim 1 or 2, comprising:

5. A memory unit is provided which stores a plurality of different feed axis operation information and a plurality of different second variables which respectively correspond to the plurality of feed axis operation information, 3. The correction amount calculation device according to claim 1, wherein the second variable determination unit determines the second variable corresponding to the feed axis operation information acquired by the feed axis operation information acquisition unit by referring to the storage unit.

6. The computer acquiring, from the machine tool, feed axis operation information relating to the operation of a feed axis including a ball screw of the machine tool; acquiring temperature information relating to the ball screw from the machine tool; determining a first variable representing a thermal response characteristic of the ball screw independent of a change in ambient temperature of the ball screw, the first variable being included in a thermal displacement estimation formula for estimating a thermal displacement of the ball screw based on the feed axis operation information; determining a second variable representing a thermal response characteristic of the ball screw related to a change in ambient temperature of the ball screw, the second variable being included in the thermal displacement estimation formula based on the feed axis operation information; calculating a thermal displacement compensation amount of the ball screw from the thermal displacement estimation formula based on the feed axis operation information, the temperature information, the first variable, and the second variable; Run the feed axis operation information includes identification information of a feed axis of the machine tool and at least one of a position, a speed, an acceleration, and a torque of the feed axis; The temperature information relating to the ball screw includes at least one of an ambient temperature of the ball screw and a temperature of a part of the structure of the machine tool.

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