Numerical control device, numerical control system, computer-readable medium, and numerical control method

Abstract

The present application provides a numerical control device, a numerical control system, a program, and a numerical control method capable of preventing the influence of noise in distance measurement. The numerical control device of the embodiment includes a distance control section, a filter section, a decision section, and a setting section. The distance control section controls so that the distance between a first object and a second object approaches a target distance. The filter section applies a signal representing the distance to a filter. The decision section decides a time constant that is calculated based on a relationship between an output signal of a distance sensor that measures the distance and the distance, based on the target distance. The setting section sets the time constant of the filter to the time constant decided by the decision section.

Description

TECHNICAL FIELD

[0001] The present application relates to a numerical control device, a numerical control system, a program, and a numerical control method. BACKGROUND

[0002] A numerical control device sometimes measures a distance to an object such as a surface of a workpiece using a gap sensor or the like. Since an output-distance characteristic of the gap sensor is nonlinear, a change amount (a slope) of a change in the output with respect to the distance differs depending on the distance. Therefore, in a distance region in which a slope of the characteristic is large, in a case where there is a variation in the output value of the gap sensor, a value of the distance converted from the output value also greatly varies. Therefore, the distance measurement in such a distance region is easily affected by an interfering component (noise) or the like. In addition, the numerical control device performs control of a machine using a measurement value affected by such noise, and thus it is possible that the machine generates vibration or the like.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 5-253804 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] An embodiment of the present application is to provide a numerical control device, a numerical control system, a program, and a numerical control method capable of preventing an influence of noise in distance measurement.

[0008] MEANS FOR SOLVING THE PROBLEMS

[0009] The numerical control device of the embodiment includes a distance control section, a filter section, a decision section, and a setting section. The distance control section controls so that a distance between a first object and a second object approaches a target distance. The filter section applies a signal representing the distance to a filter. The decision section decides a time constant that is calculated based on a relationship between an output signal of a distance sensor that measures the distance and the distance based on the target distance. The setting section sets the time constant of the filter to the time constant decided by the decision section.

[0010] EFFECTS OF THE INVENTION

[0011] According to one aspect, it is possible to prevent an influence of noise in distance measurement. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a block diagram showing a main part structure of a numerical control system according to an embodiment and constituent elements included in the numerical control system.

[0013] Figure 2 FIG. 1 is a graph showing an example of a sensor signal-displacement amount characteristic of a gap sensor.

[0014] Figure 3 FIG. 2 is a flowchart showing an example of processing of a control section in FIG. 1. Figure 1

[0015] Figure 4 FIG. 3 is a flowchart showing an example of processing of a control section in FIG. 2. Figure 1

[0016] Figure 5 FIG. 4 is a graph showing an example of a time change of a displacement amount. DETAILED DESCRIPTION

[0017] Hereinafter, a numerical control system according to several embodiments will be described using the drawings. Note that the scale of each part is sometimes changed appropriately in each drawing used in the description of the following embodiments. Also, in the description of the following embodiments, each drawing is sometimes omitted of a structure for the sake of description. Also, in each drawing and this specification, the same reference signs indicate the same elements.

[0018] [First Embodiment]

[0019] Figure 1 FIG. 1 is a block diagram showing an example of a main part structure of a numerical control system 1 according to the first embodiment and constituent elements included in the numerical control system 1. The numerical control system 1 is a system in which a numerical control device 100 performs computerized numerical control (CNC) on a machine tool 200 or the like. As an example, the numerical control system 1 includes the numerical control device 100, a gap sensor 203, and the machine tool 200.

[0020] The numerical control device 100 is a device that performs CNC on the machine tool 200 or the like. As an example, the numerical control device 100 includes a control section 110, a ROM (read-only memory) 120, a RAM (random access memory) 130, an auxiliary storage device 140, and a control interface 150. Also, these sections are connected by a bus 160 or the like.

[0021] ​​The control section 110 corresponds to a hub portion of a computer that performs processing such as calculation and control required for the operation of the numerical control device 100. The control section 110 is, for example, a CPU (central processing unit), an MPU (micro processing unit), a SoC (system on a chip), a DSP (digital signal processor), a GPU (graphic processing unit), an ASIC (application specific integrated circuit), a PLD (programmable logic device), or a FPGA (field-programmable gate array), or the like. Alternatively, the control section 110 is a combination of a plurality of these. The control section 110 controls each section based on a program such as firmware, system software, and application software stored in the ROM 120 or the auxiliary storage device 140, and the like, to realize various functions of the numerical control device 100. In addition, the control section 110 performs the processing described later based on the program. The control section 110 functions as, for example, the correlation table generation section 111, the displacement amount calculation section 112, the time constant calculation section 113, the time constant switching section 114, the filter section 115, and the gap control section 116 based on the program. These sections are described later. In addition, a part or all of the program can be incorporated in the circuit of the control section 110.

[0022] The ROM 120 corresponds to a main storage device of a computer with the control section 110 as a hub. The ROM 120 is a nonvolatile memory dedicated to reading data. The ROM 120 stores, for example, firmware among the programs. In addition, the ROM 120 stores data and the like used when the control section 110 performs various processing.

[0023] The RAM 130 corresponds to a main storage device of a computer with the control section 110 as a hub. The RAM 130 is a memory for reading and writing data. The RAM 130 is used as a work area or the like that stores data temporarily used when the control section 110 performs various processing. The RAM 130 is typically a volatile memory.

[0024] The auxiliary storage device 140 corresponds to an auxiliary storage device of a computer with the control section 110 as a center. The auxiliary storage device 140 is, for example, an EEPROM (electric erasable programmable read-only memory), an HDD (hard disk drive), a flash memory, or the like. The auxiliary storage device 140 stores, for example, system software and application software among the programs. In addition, the auxiliary storage device 140 stores data used when the control section 110 performs various processes, data generated by the processes in the control section 110, various setting values, and the like.

[0025] The control interface 150 is an interface for making the numerical control device 100 communicate with each device. The numerical control device 100 controls the machining device 300 via the control interface 150. In addition, the numerical control device 100 accepts input of a signal (hereinafter referred to as a "sensor signal") output from the gap sensor 203 via the control interface 150. In addition, the sensor signal is, for example, a voltage or a data signal indicating a value of the voltage, or the like. Alternatively, the sensor signal can be a current or a data signal indicating a value of the current, or the like.

[0026] The bus 160 includes a control bus, an address bus, a data bus, and the like, and transmits signals transmitted and received by each section of the numerical control device 100.

[0027] The machine tool 200 is, for example, a device that performs machining such as laser machining or cutting machining on a workpiece W based on control of the numerical control device 100. The machine tool 200 has, for example, a fixture 201, a machining head 202, and a gap sensor 203.

[0028] The fixture 201 is a device that fixes the workpiece W.

[0029] The machining head 202 has, for example, a tool or the like for machining the workpiece W. In addition, the machining head 202 is provided with the gap sensor 203.

[0030] The machine tool 200 has a function of changing a distance between the workpiece W and the machining head 202 based on control of the numerical control device 100. At this time, the machine tool 200 changes the distance between the workpiece W and the machining head 202 by moving at least either one of the fixture 201 and the machining head 202. In addition, the workpiece W is an example of a first object. The machining head 202 or the gap sensor 203 is an example of a second object.

[0031] The gap sensor 203 is a sensor for measuring the distance (gap amount) from the gap sensor 203 or the machining head 202 to the workpiece W. Alternatively, the gap sensor 203 is a sensor for measuring the distance (displacement amount) from the gap sensor 203 or the machining head 202 to a reference position. Here, the reference position refers to a position that is apart from the surface of the workpiece W by a predetermined distance h. Thus, the displacement amount has a relationship of displacement amount = (gap amount - h). Hereinafter, an example of performing various processes using the displacement amount will be described, but the numerical control system 1 can also be a manner of performing the same processes using the gap amount.

[0032] The magnitude of the sensor signal output from the gap sensor 203 varies depending on the displacement amount. For example, the larger the displacement amount, the larger the magnitude of the sensor signal. The sensor signal is input to the numerical control device 100 via the control interface 150. In addition, the object that the gap sensor 203 measures the distance to is, for example, the surface of the workpiece W. As the gap sensor 203, for example, a distance sensor of various types such as an eddy current type, an electrostatic capacitance type, an optical type using laser light or the like, or an ultrasonic wave type can be used.

[0033] The characteristics of the gap sensor 203 will be described using the following. Figure 2 The characteristics of the gap sensor 203 will be described using the following. Figure 2 is a graph showing an example of the sensor signal-displacement amount characteristics of the gap sensor 203. In Figure 2 the graph, the vertical axis represents the displacement amount g [mm], and the horizontal axis represents the sensor signal V [V (volt)]. In addition, the Figure 2 workpiece W shown in Figure 2 is shown with a portion omitted. In addition, the shape of the workpiece W shown in

[0034] As an example, the gap sensor 203 exhibits a nonlinear characteristic as shown in the graph G. The ratio (slope) of the amount of change in the displacement amount of the gap sensor 203 to the amount of change in the sensor signal at the displacement amount P1 is the slope m1. Also, the slope at the displacement amount P2 of the gap sensor 203 is the slope m2. Here, P1 > P2, and m1 > m2. In this way, the larger the displacement amount, the larger the slope m of the graph G. That is, the larger the displacement amount of the gap sensor 203, the larger the ratio of the amount of change in the sensor signal to the amount of change in the displacement amount. In addition, in Figure 2 , the sensor signal V at the displacement amount P1 is denoted as V1, and the sensor signal V at the displacement amount P2 is denoted as V2.

[0035] The relevant table generating section 111, the displacement amount calculating section 112, the time constant calculating section 113, the time constant switching section 114, the filter section 115, and the gap control section 116, which are functions of the control section 110, will be described.

[0036] The correlation table generating section 111 generates a correlation table T indicating a relationship between a sensor signal and a displacement amount in advance. The correlation table T indicates the relationship, for example, in the form of a table. In addition, the correlation table generating section 111 stores the generated correlation table T in the auxiliary storage device 140 or the like. However, the control section 110 can not generate the correlation table T by the correlation table generating section 111, but store a correlation table generated outside the numerical control device 100 in the auxiliary storage device 140 or the like. Figure 2 The correlation table generating section 111 generates a correlation table T indicating a relationship between a sensor signal and a displacement amount in advance. The correlation table T indicates the relationship, for example, in the form of a table. In addition, the correlation table generating section 111 stores the generated correlation table T in the auxiliary storage device 140 or the like. However, the control section 110 can not generate the correlation table T by the correlation table generating section 111, but store a correlation table generated outside the numerical control device 100 in the auxiliary storage device 140 or the like.

[0037] In addition, the correlation table generating section 111 can generate a function indicating a relationship between a sensor signal and a displacement amount instead of the correlation table T. The auxiliary storage device 140 can store the function instead of the correlation table T.

[0038] The displacement amount calculating section 112 performs an operation for calculating a displacement amount using a sensor signal input from the gap sensor 203 to the displacement amount calculating section 112. That is, the displacement amount calculating section 112 converts the sensor signal input to the displacement amount calculating section 112 into a displacement amount using the correlation table generated by the correlation table generating section 111. In addition, the displacement amount calculating section 112 outputs the calculated displacement amount as a signal. Further, the sensor signal is input to the numerical control device 100, for example, sequentially at predetermined time intervals. The displacement amount calculating section 112 converts a part or all of them into a displacement amount and outputs it. Further, the displacement amount calculating section 112 is an example of a conversion section that converts a sensor signal into a signal indicating a displacement amount. In addition, the sensor signal is an example of a first signal that varies depending on a distance. The signal indicating a displacement amount is an example of a second signal indicating a distance.

[0039] The time constant calculating section 113 calculates a time constant of a first-order lag filter (low-pass filter) used by the filter section 115 based on a target displacement amount (target distance) or the like. In addition, the target displacement amount is a target value of a displacement amount in an approach. The numerical control device 100 performs control so that the displacement amount approaches the target displacement amount. The time constant calculating section 113 outputs a signal indicating the calculated time constant. In addition, the time constant calculating section 113 is an example of a decision section that decides a time constant of a first-order lag filter based on a target displacement amount.

[0040] The time constant switching section 114 sets (switches) a time constant of a first-order lag filter used by the filter section 115 to a value of the time constant calculated by the time constant calculating section 113. In addition, the time constant switching section 114 is an example of a setting section that sets a time constant of a first-order lag filter to a time constant decided by the time constant calculating section 113.

[0041] The filter unit 115 includes a first-order hysteresis filter. The filter unit 115 inputs the displacement value output from the displacement calculation unit 112 to the first-order hysteresis filter. As a result, the filter unit 115 removes noise and other frequency components higher than the cutoff frequency of the first-order hysteresis filter from the displacement value. The filter unit 115 outputs the displacement signal from the first-order hysteresis filter. Furthermore, the filter output is generally: Filter output = (Previous filter output + (Target value - Previous filter output) × Control period ÷ Time constant).

[0042] The gap control unit 116 controls the machine tool 200 and the machining head 202, etc., by controlling the displacement amount output by the filter unit 115 to make the displacement amount close to the target displacement amount. Furthermore, the gap control unit 116 is an example of a distance control unit.

[0043] The following is based on Figure 3 The operation of the numerical control system 1 according to the first embodiment will be explained. Furthermore, the processing described below is just one example; various processing methods that can achieve the same result can be appropriately utilized. Figure 3 This is a flowchart illustrating an example of the processing of the control unit 110 of the numerical control device 100. The control unit 110 executes, for example, a program stored in the ROM 120 or auxiliary storage device 140. Figure 3 The processing.

[0044] exist Figure 3 In step S11, the control unit 110 determines whether approach has begun. If the control unit 110 does not determine that approach has begun, it determines "no" in step S11 and repeats step S11. Approach refers to changing the distance between the machining head 202 and the workpiece W to bring the displacement amount closer to the target displacement amount. For example, the control unit 110 determines that approach has begun when there is input indicating the start of approach. This input may be from other processes executed by the control unit 110. Alternatively, the indication information may be input to the numerical control device 100 from other devices. The indication information may include, for example, the target displacement amount P. If the control unit 110 determines that approach has begun, it determines "yes" in step S11 and proceeds to step S12.

[0045] In step S12, the control unit 110 resets the time constant of the first-order lag filter. That is, the time constant switching unit 114 sets the time constant of the first-order lag filter of the filter unit 115 to the reference time constant τB.

[0046] In step S13, the control unit 110 determines the time constant τ based on the target displacement P contained in the instruction information. That is, the time constant calculation unit 113 calculates the time constant τ that is suitable for the slope m corresponding to the target displacement P. For example, when the target displacement is...Figure 2 The time constant τ1 appropriate to the slope ml corresponding to the target displacement amount P1 is found. Also, the time constant operation section 113 finds the time constant τ2 appropriate to the slope m2 corresponding to the target displacement amount P2 when the target displacement amount is P2. Also, when the slope m is expressed by a formula, m = dg / dV.

[0047] Also, the reference displacement amount PB and the reference time constant τB decided in advance are stored in the auxiliary storage device 140 or the like of the numerical control device 100. The reference displacement amount PB and the reference time constant τB are a displacement amount and a time constant that become a reference for finding the time constant τ1. The reference displacement amount PB can be an arbitrary value, but is preferably set to a value that is the target displacement amount. The reference time constant τB is a time constant appropriate to a reference slope mB corresponding to a reference displacement amount. Also, in the following description, the sensor signal V at the reference displacement amount PB is expressed as VB. Figure 2

[0048] The time constant operation section 113 finds the time constant τ appropriate to the slope m corresponding to the target displacement amount P, for example, by the following formula.

[0049] τ = (m / mB) x τB (1)

[0050] For example, the time constant τ1 when the approach start point is the displacement amount Ps and the target displacement amount is the displacement amount P1 is τ1 = (ml / mB) x τB. For example, the time constant τ2 when the approach start point is the displacement amount Ps and the target displacement amount is the displacement amount P2 is τ2 = (m2 / mB) x τB. For example, the time constant τ2 when the approach start point is the displacement amount P1 and the target displacement amount is the displacement amount P2 is τ2 = (m2 / mB) x τB. In this way, the time constant τ changes according to the target displacement amount, and becomes the same value even if the approach start point is different. Also, for example, τB is set to 16 msec, mB is set to 2n, ml is set to n, and m2 is set to 4n. Here, n is a positive number. In this case, τ1 = (n / 2n) x 16 (msec) = 8 (msec), and τ2 = (4n / 2n) x 16 (msec) = 32 (msec). In this way, if the slope m becomes x times, the time constant τ also becomes x times, and the slope m is proportional to the time constant τ.

[0051] Also, the time constant operation section 113 can find the time constant τ according to the target displacement amount P using a table or the like that expresses the relationship between the target displacement amount P and the time constant τ, instead of using the formula (1). The table can be generated by finding the time constant τ for each of a plurality of target displacement amounts P in advance. The table is stored in the auxiliary storage device 140 or the like, for example.

[0052] ​In step S14, the time constant switching section 114 of the control section 110 sets the time constant of the first-order lag filter to the time constant τ calculated in step S13.

[0053] In step S15, the control section 110 controls the machine tool 200 to start the approach. That is, the displacement amount calculation section 112 calculates the displacement amount from the sensor signal. Then, the filter section 115 inputs the displacement amount to the first-order lag filter to remove the noise. Also, the gap control section 116 compares the displacement amount after the noise removal with the target displacement amount, and controls the machining device 300 in such a manner that the distance between the machining head 202 and the workpiece W is shortened in the case where the displacement amount is larger than the target displacement amount. Based on this control, the machining device 300 shortens the distance between the machining head 202 and the workpiece W. In contrast, the gap control section 116 controls the machining device 300 so that the distance between the machining head 202 and the workpiece W is lengthened in the case where the displacement amount is smaller than the target displacement amount. Based on this control, the machining device 300 lengthens the distance between the machining head 202 and the workpiece W. The displacement amount calculation section 112, the filter section 115, and the gap control section 116 continue the above processing until the displacement amount becomes equal to the target displacement amount. Here, the displacement amount becoming equal to the target displacement amount means that the displacement amount becomes within a predetermined error range from the target displacement amount.

[0054] In step S16, the control section 110 waits for the completion of the approach. If the displacement amount becomes equal to the target displacement amount, the control section 110 determines that the approach is completed. If the control section 110 determines that the approach is completed, the control section 110 determines "Yes" in step S16 and returns to step S11.

[0055] According to the numerical control system 1 of the first embodiment, the numerical control device 100 uses the time constant corresponding to the target displacement amount at each approach. Therefore, the numerical control device 100 of the first embodiment can reduce the influence of the noise in the measurement of the displacement amount even in the displacement amount region where the slope m is large.

[0056] In addition, according to the numerical control system 1 of the first embodiment, the numerical control device 100 uses the time constant proportional to the slope m. Therefore, the numerical control device 100 of the first embodiment can set the influence of the noise to the same degree regardless of the slope m in the target displacement amount.

[0057] [Second Embodiment]

[0058] The structure of the numerical control system 1 of the second embodiment is the same as that of the first embodiment, and thus the description is omitted.

[0059] Hereinafter, the operation of the numerical control system 1 of the second embodiment will be described based on Figure 4 the above. The control section 110 of the numerical control device 100 of the second embodiment replaces the time constant switching section 114 of the numerical control device 100 of the first embodiment.Figure 3 And execution Figure 4 The processing. Figure 4 This is a flowchart illustrating an example of the processing of the control unit 110 of the numerical control device 100. The control unit 110 executes, for example, a program stored in the ROM 120 or auxiliary storage device 140. Figure 4 The processing.

[0060] In the second embodiment, the control unit 110 in Figure 4 After the processing in step S13, the process proceeds to step S15. Thus, since the processing in step S14 is not performed, the time constant of the first-order lag filter of the filter section 115 near the start time point becomes the reference time constant τB set in step S12.

[0061] In the second embodiment, after the processing in step S15, the control unit 110 proceeds to step S21.

[0062] In step S21, the control unit 110 waits for the displacement to become near the target displacement. For example, the control unit 110 uses any of the following methods (A) to (C) to determine that the displacement is near the target displacement.

[0063] (A) When the sign of the representation of the target displacement and the difference d between the target displacement and the target displacement is reversed, the control unit 110 determines that the displacement has become close to the target displacement. When close, the displacement, for example, is... Figure 5 The change shown is close to the target displacement. Figure 5 This is a graph showing an example of the time-varying displacement. Additionally, in Figure 5 As an example, the time variation of displacement g is shown when the starting point is set to displacement Ps and the target displacement is set to P1. The control unit 110 accelerates the machining head to bring displacement g closer to the target displacement P1. Then, when displacement g approaches the target displacement P1, the control unit 110 decelerates the machining head. At this time, displacement g exceeds the target displacement P1. That is, the sign of the difference d is reversed. The difference d can be represented, for example, as d = g - P1. The time when the sign of the difference d is reversed is set to t1. The reversal of the sign of the difference d indicates that the machining head 202 has passed the target displacement. Therefore, the control unit 110 can consider the displacement to be near the target displacement based on the reversal of the sign of the difference d. Furthermore, as... Figure 5 As shown, before the subsequent displacement g becomes equal to the target displacement P1, the control unit 110 reverses the sign of the difference d several times, that is, reverses the forward direction of the processing head several times, while making the displacement g approach the target displacement P1.

[0064] (B) The control section 110 determines that the displacement amount is in the vicinity of the target displacement amount when the rate of change of the displacement amount becomes equal to or less than a predetermined threshold value TH1. When the displacement amount is close to the target displacement amount, the control section 110 performs control to decelerate the rate of change of the displacement amount so that the machining head 202 does not exceed the target displacement amount. Thus, the control section 110 can consider that the displacement amount is in the vicinity of the target displacement amount when the rate of change of the displacement amount becomes equal to or less than the predetermined threshold value. Note that the threshold value TH1 is predetermined by a designer or a manager of the numerical control device 100, for example.

[0065] (C) The control section 110 determines that the displacement amount is in the vicinity of the target displacement amount when the absolute value of the difference between the displacement amount and the target displacement amount becomes equal to or less than a predetermined threshold value TH2. Note that the threshold value TH2 is predetermined by a designer or a manager of the numerical control device 100, for example.

[0066] If the control section 110 determines that the displacement amount is in the vicinity of the target displacement amount, the control section 110 determines "Yes" in step S21 and proceeds to step S22.

[0067] In step S22, the control section 110 changes the time constant of the first-order lag filter to the time constant τ calculated in step S13. That is, the time constant switching section 114 sets the time constant of the first-order lag filter of the filter section 115 to the time constant τ calculated in step S13. After the process in step S22, the control section 110 proceeds to step S16.

[0068] In the second embodiment, if the control section 110 determines "Yes" in step S16, the control section 110 returns to step S11.

[0069] The change in the time constant through the above process will be described with reference to the case where the method of (A) is used in step S21. Here, the start point is set to the displacement amount Ps and the target displacement amount is set to P1. The control section 110 sets the value of the time constant τ as the time constant τB until the sign of the difference d is reversed, that is, from time 0 to time tl. Then, if the sign of the difference d is reversed, that is, at time tl, the control section 110 switches the value of the time constant τ to the time constant τ1. Then, the control section 110 sets the value of the time constant τ as the time constant τ1 until the completion is approached.

[0070] The numerical control system 1 of the second embodiment can achieve the same effects as the first embodiment.

[0071] Further, according to the numerical control system 1 of the second embodiment, the numerical control device 100 changes the time constant of the first-order lag filter to the time constant decided in step S13 in a case where it is determined that the displacement amount becomes in the vicinity of the target displacement amount. Thus, the numerical control device 100 of the second embodiment can prevent the decrease in responsiveness due to the increase in the time constant and the overshoot caused thereby, in addition to the vicinity of the target displacement amount.

[0072] The first and second embodiments described above can also be modified as follows.

[0073] The filter used by the filter section 115 is not limited to the first-order lag filter. The filter section 115 uses, for example, a high-pass filter, a band-pass filter, or a band-stop filter.

[0074] In the embodiments described above, the control section 110 converts the sensor signal to the displacement amount. However, the gap sensor 203 can also convert the sensor signal to a signal indicating the distance of the displacement amount or the like, and output the signal. In this case, the gap sensor 203 functions as an example of a conversion section.

[0075] In the second embodiment described above, the numerical control device 100 changes the time constant once after the approach start and before the approach completion. However, the numerical control device 100 can change the time constant more than once.

[0076] The control section 110 can also realize a part or all of the processing realized by the program in the embodiments by a hardware structure of a circuit.

[0077] The program realizing the processing of the embodiments is, for example, distributed in a state of being stored in a device. However, the device can also be distributed in a state of not storing the program. Also, the program can be distributed separately and written into the device. The distribution of the program at this time is, for example, able to be recorded in a removable storage medium, or realized by download via a network such as the Internet or a LAN.

[0078] The embodiments of the present application described above are shown as examples and do not limit the scope of the present application. The embodiments of the present application can be implemented in various ways without departing from the spirit of the present application.

[0079] Explanation of Reference Numerals

[0080] 1 numerical control system,

[0081] 100 numerical control device,

[0082] 110 control section,

[0083] 111 correlation table generating section,

[0084] 112 displacement amount operating section,

[0085] 113 time constant operating section,

[0086] 114 time constant switching section,

[0087] 115 filter section,

[0088] 116 gap control section,

[0089] 120 ROM,

[0090] 130 RAM,

[0091] 140 auxiliary storage device,

[0092] 150 control interface,

[0093] 160 bus,

[0094] 200 machine tool,

[0095] 201 fixed member,

[0096] 202 processing head,

[0097] 203 gap sensor.

Claims

1. A numerical control device characterized by comprising: a distance control section that controls so that a distance between a first object and a second object approaches a target distance; a filter section that applies a second signal that represents the distance and is converted from a first signal to a filter, the first signal being output by a distance sensor that measures the distance and varying according to the distance; a decision section that decides a time constant that is calculated according to a relationship between the first signal and the distance, based on the target distance; and a setting section that sets the time constant of the filter to the time constant decided by the decision section, the setting section sets the time constant of the filter to the time constant decided by the decision section, in a case where a sign of a difference between the distance and the target distance is reversed, in a case where the difference becomes smaller than a predetermined value, or in a case where a speed at which the distance is shortened becomes smaller than a predetermined value.

2. The numerical control device according to claim 1, characterized by further comprising: a correlation table generation section that generates a correlation table that represents the relationship; and a displacement amount calculation section that calculates the distance based on the first signal and the correlation table, the decision section calculates the time constant based on the relationship and the target distance, thereby deciding the time constant.

3. A numerical control system characterized by comprising: a distance sensor and a numerical control device, the distance sensor outputs a first signal that varies according to a distance between a first object and a second object, the distance sensor comprises a conversion section that converts the first signal to a second signal that represents the distance, the numerical control device comprises: a distance control section that controls so that the distance approaches a target distance; a filter section that applies the second signal to a filter; a decision section that decides a time constant that is calculated according to a relationship between the first signal and the distance, based on the target distance; and a setting section that sets the time constant of the filter to the time constant decided by the decision section, the setting section sets the time constant of the filter to the time constant decided by the decision section, in a case where a sign of a difference between the distance and the target distance is reversed, in a case where the difference becomes smaller than a predetermined value, or in a case where a speed at which the distance is shortened becomes smaller than a predetermined value.

4. A computer readable medium storing a program characterized by causing a processor included in a numerical control device to function as: a control section that controls so that a distance between a first object and a second object approaches a target distance; a filter section that applies a second signal that represents the distance and is converted from a first signal to a filter, the first signal being output by a distance sensor that measures the distance and varying according to the distance; a decision section that decides a time constant that is calculated according to a relationship between the first signal and the distance, based on the target distance; and ​ ​ ​ ​ ​ ​ a setting section that sets a time constant of the filter to the time constant decided by the deciding section, the setting section sets the time constant of the filter to the time constant decided by the deciding section, in a case where a sign of a difference between the distance and the target distance is reversed, in a case where the difference becomes smaller than a predetermined value, or in a case where a speed at which the distance is shortened becomes smaller than a predetermined value.

5. A numerical control method characterized by, controlling so that a distance between a first object and a second object approaches a target distance, in a case where a sign of a difference between the distance and the target distance is reversed, in a case where the difference becomes smaller than a predetermined value, or in a case where a speed at which the distance is shortened becomes smaller than a predetermined value, setting a time constant of a filter to a time constant decided based on a relationship between a first signal that varies depending on the distance and the distance output from a distance sensor that measures the distance, and the target distance, applying filtering to a second signal that represents the distance and is converted from the first signal.

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