Position control device of a feed axis in a machine tool

Abstract

A position control device of a feed axis for a machine tool, wherein the machine tool rotates a tool (41) attached to a main spindle to machine a workpiece (43), the machine tool includes a feed axis mechanism (10, 90) with a servo motor for driving a load in a predetermined linear axis direction, and the position control device comprises: a position detector configured to detect a position of a movable part of the feed axis mechanism (10, 90) so as to detect the position of the movable part in accordance with a position instruction value (P c ) to control a feed axis from a higher-level device; a speed instruction operator (2) configured to detect a deviation (Pdif) between the position instruction value (P c ) and a position detection value from the position detector; a first addition element (4) configured to add a feed-forward speed (Vff) and an output from the speed instruction operator (2) to obtain a speed instruction value (V c ), whereby the feed-forward speed (Vff) is determined by a differentiation of the position command value (P c ) is obtained; a torque command operator (6, 86) configured to detect a deviation between the speed command value (V c ) and a speed detection value (V d ) to output a feedback torque (Tfb), wherein the speed detection value (V d ) is obtained by detecting the speed of the moving part with a speed detector or by differentiating the position detection value; a second adder (9) configured to add a feed-forward torque (Tff) and the feedback torque (Tfb) to obtain a torque command value (T c ), wherein the feed-forward torque (Tff) is obtained by differentiating the feed-forward speed (Vff) and multiplying the differentiated value by an inertia (8, 88) of the movable part converted into a motor shaft; a drive unit configured to drive the servo motor via the torque command value (T c ) to be controlled; a runout amount correction device (31, 51, 61, 71) configured to correct the deviation (Pdif) between the position instruction value (P c) and the position detection value from the position detector as a reference signal, wherein the runout amount correction device (31, 51, 61, 71) is configured to calculate a position correction amount (Padd) from rotation angle information (θ) of the main spindle and the reference signal, the rotation angle information (θ) being obtained from the higher-level device; and a third addition element (36) configured to calculate the position instruction value (P c ) with the position correction amount (Padd) to obtain the position instruction value (P c ) to correct, whereby the runout amount correction device (31, 51, 61, 71) is configured to estimate a runout amount of a cutting edge (42) of the tool (41) from the reference signal, wherein the runout amount correction device (31, 51, 61, 71) is configured to calculate the position correction amount (Padd) so as to compensate for influences of the respective cutting edges (42) appearing in the reference signal.

Description

[0001] The present invention relates to a position control device for a feed axis. The position control device controls the position of the feed axis by taking into account the degree of runout of the cutting edges of a tool during machining with a machine tool, particularly during high-performance cutting of a difficult-to-cut material such as a titanium alloy. This limits chatter vibration and tool breakage.

[0002] When milling a difficult-to-cut material, a tool to which removable so-called "one-way" or "insert" cutting edges are attached is used to reduce machining costs. The heights of the attached cutting edges are not uniform in this tool because the surface to which the cutting edge of the tool is attached varies, and machining accuracy differs depending on the cutting edge itself. Therefore, runout amounts (relative mounting errors between respective cutting edges) are generated. In the case of a cutting edge with a large runout amount, tool chipping occurs and tool life is reduced. Accordingly, the present inventors have provided an invention in Japanese Patent Application Disclosure No. 2013-240837 (JP 2013-240837 A).In JP 2013 - 240 837 A, an amplitude and a phase are adjusted based on respective positions of cutting edges and pre-measured runout amounts, and feed axes are slightly shifted in an opposite direction of a machining feed direction synchronously with a main spindle to cancel the runout amounts, so that a single-cutting-edge feed amount of each cutting edge close to the originally set value is generated to reduce chipping of a tool.

[0003] The following describes the present invention with an example of the number of cutting edges Z of the tool as 3. To simplify the explanation, the respective cutting edges are numbered as #1, #2, and #3.

[0004] It is assumed that the pre-measured runout amounts C1 (i = 1 to Z) of the respective cutting edges are: C1 = 0 [µm], C2 = 20 [µm], and C3 = 25 [µm]. When a workpiece is machined with the respective cutting edges in the order #1, #2, #3, #1, #2, #3, etc., an increase / decrease D i (i = 1 to Z) of a current machining allowance D1 = C1 - C3 = -25 [µm], D2 = C2 - C1 = 20 [µm], and D3 = C3 - C2 = 5 [µm]. It is assumed that the commanded machining allowance (a feed rate of one cutting edge) is fz = 80 [µm]. Current machining allowances fz i (i = 1 to Z) of the respective cutting edges are fz1 = fz + D1 = 55 [µm], fz2 = fz + D2 = 100 [µm], and fz3 = fz + D3 = 85 [µm]. Accordingly, chipping is likely to occur at cutting edge #2, whose value is noticeably large.

[0005] Meanwhile, a cutting edge that cuts the workpiece is identified from the rotation angle of the main spindle. When cutting edge #1, whose runout amount is small, cuts the workpiece, the machining allowance is increased. When cutting edges #2 and #3, whose runout amounts are large, cut the workpiece, the machining allowance is decreased. Thus, superimposing the compensation amount and the position command value of the feed axis is considered. That is, it is assumed that a compensation amount R i (i = 1 to Z) to the respective cutting edges R1 = 15 [µm], R2 = -5 [µm] and R3 = -10 [µm]. Occurring dimensions C i + R i between the respective cutting edges become uniform, and the current machining allowances also become uniform. This results in a reduction in tool chipping.

[0006] The machining method in JP 2013-240837 A requires pre-measuring the runout amounts of the respective cutting edges using an external fixture or similar device. This causes problems by requiring labor and requiring an external fixture independent of the control device in the machine tool.

[0007] Therefore, it is an object of the present invention to provide a position control device of a feed axis for a machine tool, which does not require an external device and no preliminary measurement in a process of detecting runout amounts of respective cutting edges, while ensuring restriction of chipping of a tool similar to the conventional position control devices.

[0008] The object is achieved by an article according to one of claims 1 to 3. Further developments of the invention are the subject of the dependent claims.

[0009] To achieve the object, the invention of a first aspect is configured as follows. A feed axis position control device for a machine tool rotates a tool mounted on a main spindle to machine a workpiece. The machine tool includes a feed axis mechanism with a servo motor for driving a load in a predetermined linear axis direction. The position control device includes a position detector, a speed command operator, a first adder, a torque command operator, a second adder, a drive unit, a runout amount corrector, and a third adder. The position detector is configured to detect a position of a movable part of the feed axis mechanism, thereby controlling the movable part in accordance with a feed axis position command value from a higher-level device.The speed command operator is configured to amplify a deviation between the position command value and a position detection value from the position detector. The first adder is configured to add a feedforward speed and an output from the speed command operator to output a speed command value. The feedforward speed is obtained by differentiating the position command value. The torque command operator is configured to amplify a deviation between the speed command value and a speed detection value to output a feedback torque. The speed detection value is obtained by detecting the speed of the moving part by a speed detector or differentiating the position detection value.The second adder is configured to add a feedforward torque and the feedback torque to output a torque command value. The feedforward torque is obtained by differentiating the feedrate advance and multiplying the differentiated value by an inertia of the moving part converted to a motor shaft. The drive unit is configured to drive the servo motor via the torque command value. The runout amount correction device is configured to use the deviation between the position command value and the position detection value from the position detector as a reference signal and is configured to calculate a position correction amount from rotation angle information of the main spindle and the reference signal. The rotation angle information is obtained from the higher-level device.The third adder is configured to superimpose the position correction amount on the position command value to correct the position command value. The runout amount correction device is configured to estimate a runout amount of a cutting edge of the tool from the reference signal and is configured to calculate the position correction amount so as to compensate for influences of the respective cutting edges that appear in the reference signal.

[0010] To achieve the object, the invention of a second aspect is configured as follows. A feed axis position control device for a machine tool rotates a tool mounted on a main spindle to machine a workpiece. The machine tool includes a feed axis mechanism with a servo motor for driving a load in a predetermined linear axis direction. The position control device includes a position detector, a speed command operator, a first adder, a torque command operator, a second adder, a drive unit, a runout amount corrector, and a third adder. The position detector is configured to detect a position of a movable part of the feed axis mechanism, thereby controlling the position of the movable part in accordance with a feed axis position command value from a higher-level device.The speed command operator is configured to amplify a deviation between the position command value and a position detection value from the position detector. The first adder is configured to add a feedforward speed and an output from the speed command operator to output a speed command value. The feedforward speed is obtained by differentiating the position command value. The torque command operator is configured to amplify a deviation between the speed command value and a speed detection value to output a feedback torque. The speed deviation value is obtained by detecting the speed of the moving part by a speed detector or by differentiating the position detection value.The second adder is configured to add a feedforward torque and the feedback torque to output a torque command value. The feedforward torque is obtained by differentiating the feedforward speed and multiplying the differentiated value by an inertia of the moving part converted to a motor shaft. The drive unit is configured to drive the servo motor using the torque command value. The runout amount corrector is configured to apply the feedback torque as a reference signal and is configured to calculate a position correction amount from rotation angle information of the main spindle and the reference signal. The rotation angle information is obtained from the higher-level device. The third adder is configured to superimpose the position command value with the position correction amount to correct the position command value.The runout amount correction device is configured to estimate a runout amount of a cutting edge of the tool from the reference signal, and is configured to calculate the position correction amount so as to compensate for influences of the respective cutting edges occurring in the reference signal.

[0011] To achieve the object, the invention of a third aspect is configured as follows. A feed axis position control device for a machine tool rotates a tool mounted on a main spindle to machine a workpiece. The machine tool includes a feed axis mechanism with a servo motor for driving a load in a predetermined linear axis direction. The position control device includes a position detector, a speed command operator, a first adder, a torque command operator, a second adder, a drive unit, a disturbance observer, a runout amount correction device, and a third adder.The position detector is configured to detect a position of a movable part of the feed-axis mechanism so as to control the position of the movable part in accordance with a position command value of a feed-axis from a higher-level device. The speed command operator is configured to amplify a deviation between the position command value and a position detection value from the position detector. The first adder is configured to add a feedforward speed and an output from the speed command operator to output a speed command value. The feedforward speed is obtained by differentiating the position command value. The torque command operator is configured to amplify a deviation between the speed command value and a speed detection value to output a feedback torque.The speed detection value is obtained by detecting the speed of the moving part with a speed detector or by differentiating the position detection value. The second adder is configured to add a feedforward torque and the feedback torque to output a torque command value. The feedforward torque is obtained by differentiating the feedforward speed and multiplying the differentiated value by the inertia of the moving part converted to a motor shaft. The drive unit is configured to drive the servo motor using the torque command value.The disturbance observer is configured to input a difference between a value obtained by multiplying the speed detection value by an inverse characteristic of a nominal value of the feed-axis mechanism and the torque command value into a low-pass filter to obtain an estimated disturbance value. The feed-axis mechanism is formed by the servo motor and the load. The runout amount corrector is configured to use the estimated disturbance value as a reference signal and is configured to calculate a position correction amount from rotation angle information of the main spindle and the reference signal. The rotation angle information is obtained from the higher-level device. The third adder is configured to superimpose the position command value with the position correction amount to correct the position command value.The runout amount correction device is configured to estimate a runout amount of a cutting edge of the tool from the reference signal, and is configured to calculate the position correction amount so as to compensate for influences of the respective cutting edges occurring in the reference signal.

[0012] The invention of a fourth aspect in any one of the first to third aspects is configured as follows. The runout amount correction device includes a peak detection unit, an increase and decrease estimation unit, a runout amount estimation unit, and a correction amount determination unit. The peak detection unit is configured to detect a peak in a waveform and make the peak coincide with each of the cutting edges. The peak appears in the reference signal due to an influence from each of the cutting edges. The increase and decrease estimation unit is configured to estimate an increase or decrease in a machining allowance of each of the cutting edges for each of the cutting edges from a peak value in the reference signal. The peak value is detected by the peak detection unit.The runout amount estimation unit is configured to estimate a runout amount of each of the cutting edges from the increase or decrease in the machining allowance of each of the cutting edges. The increase or decrease is estimated by the increase and decrease estimation unit. The correction amount determination unit is configured to determine the position correction amount. The position correction amount is determined such that, at a time when the respective cutting edge is machining the workpiece, a correction amount based on the runout amount of each of the cutting edges is applied. The runout amount is estimated by the runout amount estimation unit.

[0013] The invention of a fifth aspect in any one of the first to third aspects is configured as follows. The machine tool includes at least two of the feed-axis mechanisms. The feed-axis mechanisms are associated with a first axis and a second axis. The second axis is installed independently of the first axis. The runout amount correction device includes a peak detection unit, an increase-and-decrease estimation unit, a runout amount estimation unit, and a correction amount determination unit. The peak detection unit is configured to detect a peak in a waveform and make the peak coincide with each of the cutting edges. The peak appears in the reference signal associated with the first axis due to an influence of each of the cutting edges.The increase and decrease estimation unit is configured to estimate an increase or decrease in a machining allowance of each of the cutting edges for each of the cutting edges from a peak value in the reference signal. The peak value is detected by the peak value detection unit. The runout amount estimation unit is configured to estimate a runout amount of each of the cutting edges from the increase or decrease in the machining allowance of each of the cutting edges. The increase or decrease is estimated by the increase and decrease estimation unit. The correction amount determination unit is configured to determine the position correction amount associated with the second axis. The position correction amount is determined such that, at a time when the respective cutting edges machine the workpiece, a correction amount based on the runout amount of each of the cutting edges is applied.The out-of-roundness degree is estimated by the out-of-roundness degree estimation unit.

[0014] The invention of a sixth aspect in any one of the first to third aspects is configured as follows. The machine tool includes the feed-axis mechanisms associated with a plurality of respective feed axes. The runout amount correction device includes a peak detection unit, an increase-and-decrease estimation unit, a runout amount estimation unit, and a correction amount determination unit. The peak detection unit is configured to detect a peak in a waveform and make the peak coincide with each of the cutting edges. The peak appears in the reference signal due to an influence from each of the cutting edges. The increase-and-decrease estimation unit is configured to estimate an increase or decrease in a machining allowance of each of the cutting edges for each of the cutting edges from a peak value in the reference signal.The peak value is detected by the peak value detection unit. The runout amount estimation unit is configured to estimate a runout amount of each of the cutting edges from the increase or decrease in the machining allowance of each of the cutting edges. The increase or decrease is estimated by the increase-and-decrease estimation unit. The correction amount determination unit is configured to determine the position correction amount for each of the feed axes. The position correction amount is determined so that, at a time when the respective cutting edges machine the workpiece, a correction amount based on the runout amount is applied to each of the cutting edges. The runout amount is estimated by the runout amount estimation unit.

[0015] The invention of a seventh aspect in any one of the first to third aspects is configured as follows. The machine tool includes at least two of the feed-axis mechanisms. The feed-axis mechanisms are associated with a first axis and a second axis. The second axis is installed independently of the first axis. The runout amount correction device includes a peak detection unit, an increase-and-decrease estimation unit, a runout amount estimation unit, and a correction amount determination unit. The peak detection unit is configured to detect a peak in a waveform and make the peak coincide with each of the cutting edges. The peak appears in a synthesized signal due to an influence from each of the cutting edges. The synthesized signal is obtained by synthesizing the reference signal associated with the first axis and the reference signal associated with the second axis.The increase and decrease estimation unit is configured to estimate an increase or decrease in a machining allowance of each of the cutting edges from a peak value in the synthesized signal for each of the cutting edges. The peak value is detected by the peak value detection unit. The runout amount estimation unit is configured to estimate a runout amount of each of the cutting edges from the increase or decrease in the machining allowance of each of the cutting edges. The increase or decrease is estimated by the increase and decrease estimation unit. The correction amount determination unit is configured to determine the position correction amount of each of the axes. The position correction amount is determined such that, at a time when the respective cutting edge machines the workpiece, a correction amount based on the runout amount of each of the cutting edges is applied.The out-of-roundness degree is estimated by the out-of-roundness degree estimation unit.

[0016] The invention of an eighth aspect in the sixth aspect is configured as follows. The machine tool includes a main spindle control device. The main spindle control device is configured to control a rotational speed of the main spindle in accordance with a speed command value from a higher-level device. The main spindle control device includes a torque command operator and a drive unit. The torque command operator is configured to amplify a deviation between the speed command value and a speed detection value to output a torque command value.

[0017] The speed detection value is obtained by detecting it with a main spindle speed detector mounted on the main spindle. Alternatively, the speed detection value is obtained by differentiating a position detection value detected by a main spindle position detector mounted on the main spindle. The drive unit is configured to drive a main spindle motor using the torque command value. The runout amount correction device is configured to use the torque command value obtained from the main spindle control device as the reference signal.

[0018] The invention of a ninth aspect in the sixth aspect is configured as follows. The machine tool includes a main spindle control device. The main spindle control device is configured to control a rotational speed of the main spindle in accordance with a speed command value from a higher-level device. The main spindle control device includes a torque command operator, an adder, and a drive unit. The torque command operator is configured to amplify a deviation between the speed command value and a speed detection value to output a feedback torque. The speed detection value is obtained by detection by a main spindle speed detector mounted on the main spindle.Alternatively, the speed detection value is obtained by differentiating a position detection value detected by a main spindle position detector mounted on the main spindle. The adder is configured to add a feedforward torque and the feedback torque to output a torque command value. The feedforward torque is obtained by differentiating the speed command value and multiplying the differentiated value by an inertia of the movable part of the main spindle converted to a motor shaft. The drive unit is configured to drive a main spindle motor via the torque command value. The runout amount correction device is configured to use the feedback torque obtained from the main spindle control device as the reference signal.

[0019] The invention of a tenth aspect in the sixth aspect is configured as follows. The machine tool includes a main spindle control device. The main spindle control device is configured to control a rotational speed of the main spindle in accordance with a speed command value from a higher-level device. The main spindle control device includes a torque command operator, an adder, a drive unit, and a disturbance observer. The torque command operator is configured to amplify a deviation between the speed command value and a speed detection value to output a feedback torque. The speed detection value is obtained by detection by a main spindle speed detector mounted on the main spindle.Alternatively, the speed detection value is obtained by differentiating a position detection value detected by a main spindle position detector mounted on the main spindle. The adder is configured to add a feedforward torque and the feedback torque to output a torque command value. The feedforward torque is obtained by differentiating the speed command value and multiplying the differentiated value by an inertia of the movable part of the main spindle converted to a motor shaft. The drive unit is configured to drive a main spindle motor using the torque command value.The disturbance observer is configured to input a difference between a value obtained by multiplying the speed detection value by an inverse characteristic of a nominal value of the main spindle motor and the torque command value into a low-pass filter to obtain an estimated disturbance value. The runout amount correction device is configured to use the estimated disturbance value obtained from the main spindle controller as the reference signal.

[0020] The invention of an eleventh aspect in any one of the first to tenth aspects is configured as follows. The position control device includes a display unit or a screen output unit. The display unit is configured to display an excess of a level of the position correction amount over a preset alarm detection level of the cutting edge runout amount. The screen output unit is configured to display the position correction amount to attract the operator's attention.

[0021] According to the present invention, the out-of-roundness of the cutting edges of the tool can be corrected without the need for external devices and prior measurements. This allows for simple and low-cost reduction of tool chipping. Fig. 1 is a block diagram of a position control device of an embodiment 1. Fig. 2 is a block diagram of a position control device of an embodiment 2. Fig. 3 is a block diagram of a position control device of an embodiment 3. Fig. 4 is a block diagram of an out-of-roundness amount correcting device. Fig. 5 shows examples of waveforms of reference signals before correction of runout of a cutting edge of a tool. Fig. Figure 6 shows examples of waveforms of the reference signals after correction of the runout of the cutting edge of the tool. Fig. 7 is an explanatory view showing a force acting on the tool during machining. Fig. 8 is a block diagram of a first modification of a runout amount correcting device supporting multi-axis control. Fig. 9 is a block diagram of a second modification of a runout amount correcting device supporting multi-axis control. Fig. 10 is a block diagram of a third modification of a runout amount correcting device supporting multi-axis control. Fig. 11 is a block diagram of a first aspect receiving a reference signal from a main spindle controller. Fig. 12 is a block diagram of a second aspect receiving a reference signal from a main spindle controller. Fig. 13 is a block diagram of a third aspect receiving a reference signal from a main spindle controller. Fig. 14 is a configuration diagram to issue an alarm when an estimated out-of-roundness amount is large. Fig. Figure 15 is a configuration diagram to indicate to an operator the estimated degree of runout.

[0022] The following describes embodiments of the present invention with reference to the drawings.

[0023] Fig. 1 to Fig. 3 are block diagrams illustrating position control devices of feed axes for a machine tool of each of Embodiments 1 to 3 of the present invention. For example, the following well-known machine tool is considered to be the same for each of the embodiments. The machine tool includes a main spindle head on a front surface of a column uprightly disposed on a bed. The main spindle head has a main spindle to which a tool is attached. The main spindle head is movably controlled in the X-axis direction and the Z-axis direction by an X-axis control unit and a Z-axis control unit. A table is arranged on the bed so as to be movably controlled in the Y-axis direction by a Y-axis control unit, so that a workpiece can be mounted on the table.The tool used here contains a plurality of cutting edges arranged at equal intervals on a concentric circle on the circumference.

[0024] In Fig. 1 to Fig. 3, a subtraction element 1 calculates a position deviation Pdif from a difference between a position instruction value P c and a position detection value P d a position detector. A numerical control unit, which is a higher-level device for controlling respective control units, assigns the position instruction value P c The position detector is mounted on a servo motor in a target device (here, a Y-axis control unit) 10, which is a feed axis mechanism or a table. A speed command operator 2 amplifies the calculated position deviation Pdif. Then, an adder 4 (a first adder) adds the position command value P cwith a feed-forward speed Vff obtained by differentiation by a differentiator 3, and thus a speed command value V c receive.

[0025] Next, a subtraction element 5 calculates a difference between the speed command value V c and a speed detection value V d . The speed detection value V d is determined by differentiating the position detection value P d or is obtained directly from a speed detector mounted in the target system 10. Then, a torque command operator 6 amplifies the difference, and thus a feedback torque Tfb is obtained. Furthermore, an adder 9 (a second adder) adds the feedback torque Tfb to a feedforward torque Tff, and thus a torque command value T cThe feedforward torque Tff is calculated by differentiating the feedforward speed Vff by a differentiator 7 and multiplying the differentiated value by an inertia 8 of a moving part in the target system 10 converted to a motor shaft. The target system 10 causes the servo motor in the target system 10, through control from a current control unit (not shown) as a drive unit, to generate a torque in accordance with the torque command value T. c For example, the target system 10 drives the table as a driven body in the target system 10 via a ball screw.

[0026] Here is in Fig. 1 the position deviation Pdif is configured as a reference signal ref. In Fig. 2, the feedback torque Tfb is configured as the reference signal ref. In Fig. 3, a subtraction element 22 calculates a difference between a speed detection value V d with an inverse characteristic P n -1 a nominal value P n the target system 10 and the torque command value T c . An estimated disturbance value T d , which is obtained by passing the output from the subtractor 22 through a low-pass filter 23, is configured as the reference signal ref.

[0027] Meanwhile, a runout amount correction device 31 calculates a position correction amount Padd from the reference signal ref and rotation angle information θ of the main spindle received from the higher-level device. An adder 36 (a third adder) superimposes the position command value P c with the calculated position correction amount Padd to obtain the position instruction value P c to correct.

[0028] As in Fig. 4, the runout amount correcting device 31 includes a peak detection unit 32, an increase and decrease estimation unit 33, a runout amount estimation unit 34, and a correction amount determination unit 35.

[0029] The peak detection unit 32 uses the rotation angle information θ of the main spindle to identify which cutting edge of the tool is performing the machining. At the same time, the peak detection unit 32 monitors the reference signal ref to detect a peak value in a waveform that occurs due to an influence of cutting the workpiece with these cutting edges. The peak value in the waveform detected here is a value that corresponds to the current machining allowance fz. i (i = 1 to Z). If the current machining allowance fz ilarge, the peak value is also recorded as a large value. If the current machining allowance fz i is small, the peak value is also detected as a small value. The peak value in the waveform, which occurs due to the influence of cutting the workpiece with these cutting edges, is detected by the number of cutting edges Z of the tool in one revolution of the main spindle at approximately the pitches at which the cutting edges are mounted.

[0030] Next, the increase and decrease estimator 33 estimates the increase / decrease D i (i = 1 to Z) of the machining allowance of the respective cutting edges from the peak value of the reference signal ref detected by the peak detection unit 32 for the respective cutting edges.

[0031] Furthermore, the out-of-roundness estimation unit 34 calculates the out-of-roundness degree C i from each cutting edge from the increase / decrease Di the estimated machining allowance of each cutting edge.

[0032] Then, the correction amount determining unit 35 determines the position correction amount Padd so that the correction amount corresponding to the out-of-roundness amounts C i the cutting edges calculated by the runout amount estimation unit 34 can be applied when the workpiece is cut with these cutting edges at the next time.

[0033] These operations from the peak detection unit 32 to the correction amount determination unit 35 are repeatedly performed until the peak values appearing in the reference signals ref are balanced. This allows for an improvement in the estimation accuracy of the out-of-roundness amounts C. i the cutting edges.

[0034] The following is described with concrete examples. Similar to the prior art, the following is described using an example of the number of cutting edges Z of the tool, which is 3 [cutting edges]. Furthermore, the runout amounts C i (i = 1 to Z) of the respective cutting edges: C1 = 0 [µm], C2 = 20 [µm] and C3 = 25 [µm].

[0035] As described above, when the workpiece is machined with the respective cutting edges in the order of #1, #2, #3, #1, #2, #3, etc. with the instructed machining allowance (the feed amount of one cutting edge) fz, which is 80 [µm], the actual machining allowances fz i (i = 1 to Z) of the respective cutting edges fz1 = 55 [µm], fz2 = 100 [µm] and fz3 = 85 [µm].

[0036] At this point in time, a cutting load acts proportional to the current machining allowance fz ias a torque disturbance. Accordingly, the position deviation Pdif and the feedback torque Tfb (the estimated disturbance value T d ), as in Fig. 5. In the case where the configuration of the position control device of the Fig. 1, Pdif in the upper graph is Fig. 5 is considered as the reference signal ref. In the case where the configuration of the position control device of the Fig. 2 or Fig. 3 is the aspect shown, Tfb (T d ) in the lower graph in Fig. 5 is considered as the reference signal ref.

[0037] Then, the peak detection unit 32 monitors the reference signal ref to obtain a peak value Pref i in the waveform as a value that corresponds to the current processing allowance fz iAt this time, the rotation angle information θ of the main spindle determines which cutting edge produces the detected peak value.

[0038] Next, the increase and decrease estimation unit 33 estimates the increase / decrease D using, for example, the following formula (1) i the machining allowance of each cutting edge from the peak value Pref detected by the peak detection unit 32 i away. Di={Prefi−∑(Prefi) / Z}×KD

[0039] Here is {Pref i - Σ (Prefi) / Z} an operation to calculate the offset component of Pref i to eliminate, and also, the total sum of increases or decreases D i the machining allowances to 0. K D represents an estimated gain to measure the increase / decrease D iof the machining allowance. Setting a large estimated gain K D allows a reduction of the time required until the peak values Pref i However, setting an excessively large value may not be able to compensate for the out-of-roundness C in the process of repeatedly estimating the out-of-roundness C i the cutting edge. Therefore, setting a suitable value is necessary.

[0040] Thereafter, the out-of-roundness estimation unit 34 calculates the out-of-roundness degree C i from each cutting edge from the increase / decrease D i the machining allowance of each cutting edge, which is estimated by the increase and decrease estimation unit 33 via, for example, the following formula (2). Ci=(Di−Di+1) / 3 (note that Dz+1=D1)

[0041] Provisionally assumed that the increase / decrease D iThe machining allowance of each cutting edge estimated by the increase and decrease estimation unit 33 is D1 = -25 [µm], D2 = 20 [µm], and D3 = 5 [µm]. C1 = (D1 - D2) / 3 = -15 [µm], C2 = (D2 - D3) / 3 = 5 [µm], and C3 = (D3 - D1) / 3 = 10 [µm]. From the runout amount of each cutting edge calculated using formula (2), the offset component is eliminated, so the total becomes 0. Accordingly, the runout amount values become values that differ from the original values based on the cutting edge #1 (C1 = 0 [µm], C2 = 20 [µm] and C3 = 25 [µm]) by the offset amount.

[0042] Next, the correction amount determination unit 35 calculates based on the out-of-roundness amounts C i the out-of-roundness extent C calculated by the out-of-roundness extent estimation unit 34 i the cutting edges the correction amount R i(i = 1 to Z) for each cutting edge using, for example, the following formula (3). Ri=−Ci+Ri⋅z−1 (note that Ri⋅z−1 represents the previous value of Ri)

[0043] Further, the correction amount determination unit 35 outputs the position correction amount Padd so that R i when the cutting edge of #i cuts the workpiece at the next time. Consequently, just as in the prior art in which the correction amounts R i (i = 1 to Z) to the respective cutting edges as: R1 = 15 [µm], R2 = -5 [µm] and R3 = -10 [µm], the current machining allowances are uniform, thus ensuring that tool breakage is limited.

[0044] As in Fig. 6, even after appropriate correction amounts R iare calculated and the peak values that occur in the reference signal ref are balanced, the formula (3) determines the appropriate correction amounts R i This allows maintaining the state in which the current machining allowances are uniform.

[0045] The embodiment calculates the increase or decrease D i the machining allowance of each cutting edge by the formula (1), the degree of runout C i of each cutting edge by the formula (2) and the correction amount R i for each cutting edge by formula (3). However, the operation methods for the respective values are not limited to these formulas. Specifically, the optimal operating formula for formula (2) differs depending on the number of cutting edges Z of the tool. For example, in the case of Z = 4 [cutting edges] C i calculated using the following formula (4). Ci=(Di−2Di+1−Di+2) / 4 (note that it is assumed that Dz+1=D1 and Dz+2=D2)

[0046] Formula (2) and formula (4) are formulas that are valid for any given number of cutting edges Z in the following formula (5) under the conditions of ΣC i = 0 and ΣD i = 0. Formula (5) is a relational formula obtained by adding 0 = C1 + C2 + ... + C z (since Σ C i = 0) to the lowest formula of the following formula (6) : D z = -C z-1 + C z , which is a matrix representation of D i = C i - C i-1 is, is obtained. [Expression 1] [C1C2C3⋮CZ−1CZ]=[100⋯0−1−110⋯000−11⋯00⋮⋮⋱⋮⋮00010111⋯02]−1⋅[D1D2D3⋮DZ−1DZ] [D1D2D3⋮DZ−1DZ]=[100⋯0−1−110⋯000−11⋯00⋮⋮⋱⋮⋮00010000⋯−12]⋅[C1C2C3⋮CZ−1CZ]

[0047] Here, in the cases of Z = 3 and Z = 4, the respective formulas are expressed as follows. The formulas correspond to the respective formulas (2) and (4). Z=3[C1C2C3]=[10−1−110102]−1⋅[D1D2D3]=13⋅[201231−101]⋅[D1D2D3] =13⋅[1−1001−1−101]⋅[D1D2D3](∵∑Di=0) Z=4 [C1C2C3C4]=[100−1−11000−1101102]−1⋅[D1D2D3D4]=14⋅[2−10123012341−2−101]⋅[D1D2D3D4] =14⋅[1−2−1001−2−1−101−2−2−101]⋅[D1D2D3D4](∵∑Di=0)

[0048] In Fig. 3, a disturbance observer is used to estimate the disturbance value T d However, a configuration that reduces the estimated disturbance value T d to the torque command value T c added to cancel a disturbance component. In addition, the configuration of the disturbance observer is not limited to the configuration in Fig. 3 as long as the influence of the cutting load can be detected.

[0049] Furthermore, the embodiment describes the example in which the change of the cutting load in the reference signal ref as shown in Fig. 5, occurs in the same way with each rotation of the main spindle. However, in the current machining, a case in which the level of the cutting load changes gradually is also assumed. However, in the process of detecting the peak value Pref i of the reference signal ref by the peak detection unit 32 itself in this case to the previous value Pref i z -1 and the penultimate peak value Pref i z -2 of the peak value Pref i of the identical cutting edge. This allows identifying the extent to which the cutting load is in an upward (or downward) trend. Accordingly, the components of the upward (or downward) trend of the values in the peak value Pref iThe cutting load involved must be considered separately. Consequently, even in the case where the cutting load changes with each rotation of the main spindle, the estimation and correction of the degree of runout of a cutting edge is possible.

[0050] As described above, the position control device according to each embodiment includes the speed command operator 2, the adder 4, the torque command operator 6, the adder 9, the drive unit, the runout amount corrector 31, and the adder 36. The speed command operator 2 is configured to calculate the position deviation Pdif between the position command value P c and the position detection value P d The adder 4 is configured to add the feed-forward speed Vff and the output from the speed command operator 2 to obtain the speed command value V cThe feed-forward speed Vff is determined by differentiating the position command value P c The torque command operator 6 is configured to detect a deviation between the speed command value V c and the speed detection value V d of the movable part to output the feedback torque Tfb. The adder 9 is configured to add the feedforward torque Tff and the feedback torque Tfb to obtain the torque command value T c The feedforward torque Tff is obtained by differentiating the feedforward speed Vff and multiplying the differentiated value by the inertia converted to a motor shaft. The drive unit is configured to drive the servo motor via the torque command value T cThe runout amount correction device 31 is configured to calculate the position correction amount Padd from the reference signal ref and the rotation angle information θ of the main spindle, so that influences of the respective cutting edges are compensated. The adder 36 is configured to calculate the position instruction value P c with the position correction amount Padd to set the position instruction value P c The out-of-roundness of the tool's cutting edges can be corrected without the need for an external fixture or prior measurement. This allows for easy and low-cost tool chipping control.

[0051] In the case of a machine tool that controls the positions of a tool and a workpiece with a plurality of feed axes, changing the configuration of a runout amount correction device is preferable. This allows for easy detection of changes in the cutting load or calculation of more appropriate correction amounts. The following describes modifications of the runout amount correction device. Like reference numerals denote corresponding or identical components throughout the above-described embodiments and the following modifications, and therefore, such elements will not be further described here.

[0052] For example, as in Fig. 7, a configuration is provided that controls a position of a main spindle head including a tool 41 with a first axis (here, an X-axis control unit) and controls a position of a table securing a workpiece 43 with a second axis (here, a Y-axis control unit). When machining is performed in the second-axis moving direction, a main force and a thrust force act as the cutting load applied to the cutting edges 42 (here, three cutting edges). When the cutting edge 42 faces the machining direction, the main force acts in the first-axis moving direction, while the thrust force acts in the second-axis moving direction. The magnitude of the main force is basically larger than the thrust force.This means that the influence of a change in cutting load is more likely to occur in the first axis, which is perpendicular to the machining direction, than in the second axis, which is in the machining direction. The influence of cutting edge runout, which appears in the reference signal ref, is therefore more noticeable.

[0053] Therefore, if an out-of-roundness correction device 51 such as one shown in Fig. 8 shown first modification is configured, the influence of the runout of the cutting edge is more likely to be removed.

[0054] This runout amount correction device 51 includes a peak detection unit 52, the increase and decrease estimation unit 33, the runout amount estimation unit 34, and a correction amount determination unit 55. The runout amount correction device 51 differs from the runout amount correction device 31 in Fig. 4 in the following points. The reference signal ref is input to the peak detection unit 32 of the runout amount correcting device 31. The correction amount determining unit 35 outputs the position correction amount Padd of the control axis equal to the reference signal ref. Meanwhile, a reference signal ref_1 of the first axis is input to the peak detection unit 52. The correction amount determining unit 55 outputs a position correction amount Padd_2 of the second axis, which is a different axis, from the reference signal ref_1. An operation is performed in the same manner as the operation that performs correction while determining which cutting edge of the tool performs machining in this axis direction from the rotation angle information θ of the main spindle.

[0055] The influence of the cutting edge runout occurs not only in the machining direction but also in the direction perpendicular to the machining direction, which, in addition to the change of the cutting load, leads to the unevenness of cutting allowances at each cutting edge.

[0056] Accordingly, if an out-of-roundness correction device 61 such as that shown in Fig. 9 is configured so that the cutting loads are balanced in the respective machining direction and vertical direction.

[0057] This runout amount correcting device 61 includes the peak detecting unit 32, the increase and decrease estimating unit 33, the runout amount estimating unit 34, and a correction amount determining unit 65.

[0058] The runout amount correction device 61 differs from the runout amount correction device 31 in Fig. 4 in the following points. The correction amount determination unit 35 of the runout amount correction device 31 outputs the position correction amount Padd in one axis direction. Meanwhile, the correction amount determination unit 65 outputs both a first-axis position correction amount Padd_1 and a second-axis position correction amount Padd_2. An operation is performed in the same manner as the operation that performs correction while determining which cutting edge of the tool performs machining in this axis direction from the rotation angle information θ of the main spindle.

[0059] Here, the axes intended for correction are not necessarily limited to two. It is also possible to add an axis if necessary according to the mechanical configuration. It is also possible to appropriately allocate the position correction amount according to the machining direction and axis configuration.

[0060] Next, focusing on the machining direction and the control axis direction, as shown in Fig. 7, both are not always true. This may cause a deviation in the detection of a change in cutting load from the correction.

[0061] Accordingly, if an out-of-roundness correction device 71 such as that shown in Fig. 10, the cutting loads are appropriately balanced even if the machining direction differs from the control axis direction.

[0062] This runout amount correction device 71 includes a peak detection unit 72, the increase and decrease estimation unit 33, the runout amount estimation unit 34, and the correction amount determination unit 65. The runout amount correction device 71 differs from the runout amount correction device 61 in Fig. 9 in the following points. The reference signal ref from one axis is input to the peak detection unit 32 of the runout amount correcting device 61. Meanwhile, a plurality of reference signals, which are the first-axis reference signal ref_1 and the second-axis reference signal ref_2, are input to the peak detection unit 72. Based on the configuration of the control axes, both signals are internally synthesized, and a synthesized signal corresponding to the machining direction component or the perpendicular direction component is calculated. In addition, the peaks in the waveform of this synthesized signal, which appear due to the influences of the respective cutting edges, are matched with the respective cutting edges and detected.

[0063] Here, it is not necessary for the reference signals to be input to be limited to two axes. It is also possible to add an axis if necessary according to the mechanical configuration.

[0064] Thus, changing the configuration of the runout correction device makes it much easier to eliminate the influence of cutting edge runout when the tool and workpiece positions are controlled with multiple feed axes. Furthermore, this allows for balancing the cutting loads in the respective axis directions. Furthermore, even when the machining direction and the control axis direction differ, the cutting loads can be appropriately balanced, ensuring that tool chipping is limited.

[0065] When the configuration of the runout amount correction device 61 in Fig. 9, it is not always necessary for the reference signal ref to be the control signal calculated within the position control device of the feed axis. It is also possible to configure the control signal calculated within the main spindle control device that controls the main spindle to which the tool is attached as the reference signal ref. The following describes how to obtain the reference signal ref from this main spindle control device. The main spindle control device is described below as one that controls the rotation speed of the main spindle. However, the main spindle control device may have a configuration that controls the rotation angle (position) of the main spindle. In this case, it is also possible to balance the cutting loads of the position control devices of the feed axes in the same way.

[0066] Fig. 11 to Fig. 13 are block diagrams illustrating the main spindle control devices of the first to third aspects. In each drawing, reference numeral 85 denotes a subtractor. The subtractor 85 handles a difference between a speed command value V c and the speed detection value V d . A numerical control unit, such as the higher-level control device, to control the respective control units assigns the speed instruction value V c The speed detection value V d is obtained by differentiating the position detection value from a main spindle position detector, or is obtained directly from a main spindle speed detector. The main spindle speed detector or the main spindle position detector is mounted on the main spindle motor in the target device 90.

[0067] In Fig. 11, the difference is amplified by a torque command operator 86, and thus the torque command value T c received. In Fig. 12 and Fig. 13, this difference is amplified by the torque command operator 86, thus obtaining a feedback torque Tfb.

[0068] An adder 89 adds this feedback torque Tfb with a feed-forward torque Tff, and thus a torque command value T c The feed-forward spindle torque Tff is obtained by differentiating the speed command value V cby a differentiator 87 and multiplying the differentiated value by an inertia 88 converted into a motor shaft of a movable part of the main spindle in the target system 90. The target system 90 causes the main spindle motor in the target system 90 to generate a torque in accordance with the torque command value T by controlling it via a power control unit (not shown) as a drive unit. c and thus rotate the tool attached to the main spindle.

[0069] Here, in the first aspect, according to Fig. 11 the torque command value T c as the reference signal ref. In the second aspect according to Fig. 12, the feedback torque Tfb is configured as the reference signal ref. In the third aspect according to Fig. 13, a subtraction element 92 creates a difference between a value obtained by multiplying the speed detection value V d with an inverse characteristic P n -1 of the nominal value P n the target system 90 is obtained, and the torque command value T c . An estimated disturbance value T d , which is obtained by passing the output from the subtractor 92 through a low-pass filter 93, is configured as the reference signal ref.

[0070] The main spindle control device in Fig. 11 to 13 can set the speed detection value V das an integral of the position detection value obtained directly from the main spindle position detector as the rotation angle information θ of the main spindle. Inputting the rotation angle information θ and the reference signal ref from this main spindle to the runout amount correction device 61 calculates the position correction amounts Padd_1 and Padd_2 of the respective axes of the feed axes.

[0071] In Fig. 11 to 13, each of the torque command value T c , the feedback torque Tfb and the estimated disturbance value T d configured as the reference signal ref input to the runout amount correction device 61. This uses a system in which the main force acting on the tool in Fig. 7 acts as a disturbance torque in the main spindle control device. A feedback control is active to cancel this disturbance. This means that increased cutting edge runout and increased main force also increase the disturbance torque, resulting in an increase in the estimated disturbance value T d This also increases the torque command value T d and the feedback torque Tfb, which attempts to compensate for the magnitude of the disturbance torque. In contrast, a reduced cutting edge runout and a reduced main force also reduce the disturbance torque, resulting in a reduction in the estimated disturbance value T d This reduces the torque command value T c and the feedback torque Tfb, which attempts to compensate for the magnitude of the disturbance torque, as well.

[0072] Thus, the influence of the cutting edge runout on the torque command value T c , the feedback torque Tfb and the estimated disturbance value T d transferred, and these values can be used as the reference signals ref input to the runout amount correction device 61. Correcting the calculated position correction amounts Padd_1 and Padd_2 of the respective axes of the feed axes by the respective axes of the feed axes enables appropriate balancing of the cutting loads. This allows for limiting tool chipping.

[0073] It is also possible to notify the operator of the large runout amount based on the estimated runout amounts of the cutting edges to attract his / her attention. Fig. 14 shows a configuration diagram to issue an alarm when the estimated out-of-roundness amount is large. Fig. Figure 15 shows a configuration diagram for alerting the operator of the estimated runout level for confirmation and attention. This alarm allows the operator to check the cutting edge runout to ideally perform machining with low cutting edge runout.

[0074] In Fig. In FIG. 14, reference numeral 37 denotes an absolute value operator arranged within the position control device. This absolute value operator 37 calculates the magnitude of the position correction amount Padd (or Padd_1 or Padd_2) from the position correction amount Padd (or Padd_1 or Padd_2) calculated by the correction amount determination unit 35 (or 55 or 65). A comparator 38 compares the magnitude and a preset alarm detection level AL-Level of the runout amount. As the comparison result, when the magnitude of the position correction amount Padd (or Padd_1 or Padd_2) exceeds the alarm detection level AL-Level, an alarm ALARM is output as a notification unit to attract the operator's attention. As a notification unit, various methods, including the following, are also considered.This condition is indicated by a rotating indicator light, such as a "revolving light" (registered trademark), a warning message is displayed on an operator screen, or a buzzer is generated. Several of these methods can also be combined.

[0075] Meanwhile, in Fig. 15, a screen output unit 11 disposed on the machine tool directly displays the position correction amount Padd (Padd_1 or Padd_2) calculated by the correction amount determination unit 35 (or 55 or 65). The operator can confirm whether or not the runout amounts of the cutting edges are within a suitable range. The screen output unit 11 may be disposed on an operation screen for inputting / outputting an operation with a higher-level device. Alternatively, methods of separately installing a display screen as the screen output unit 11 or configuring a monitor screen of a personal computer coupled to the higher-level device and the position control device as the screen output unit 11 are also possible.

[0076] In Fig. 14 and Fig.15, the position correction amounts Padd (or Padd_1 or Padd_2) to be entered can be replaced by the correction amount R i (i = 1 to Z) for each cutting edge calculated within the correction amount determination unit 35 (or 55 or 65).

[0077] Furthermore, the number of cutting edges of the tool is not limited to these aspects, and the number of cutting edges can be appropriately increased or decreased. In addition, the model and axis configuration, such as a multi-tasking machine or a machining center, are not limiting as long as the machine tool for feed axis control performs machining by rotating a tool formed by mounting a plurality of cutting edges arranged on the concentric circle. Not limited to the case where the first axis is perpendicular to the second axis, the present invention is applicable to cases where the second axis is arranged obliquely with respect to the first axis, and both axes are arranged in parallel for synchronous operation.

[0078] It is explicitly stated that all features disclosed in the description and / or the claims are intended to be disclosed separately and independently of one another for the purpose of original disclosure as well as for the purpose of limiting the claimed invention, regardless of the combination of features in the embodiments and / or the claims. It is explicitly stated that all value ranges or indications of groups of units disclose every possible intermediate value or intermediate unit for the purpose of original disclosure as well as for the purpose of limiting the claimed invention, in particular as limits of value ranges.

Claims

[1] A position control device of a feed axis for a machine tool, wherein the machine tool rotates a tool (41) attached to a main spindle to machine a workpiece (43), the machine tool includes a feed axis mechanism (10, 90) with a servo motor for driving a load in a predetermined linear axis direction, and the position control device comprises: a position detector configured to detect a position of a movable part of the feed axis mechanism (10, 90) so as to detect the position of the movable part in accordance with a position instruction value (P c ) to control a feed axis from a higher-level device; a speed instruction operator (2) configured to detect a deviation (Pdif) between the position instruction value (P c ) and a position detection value from the position detector; a first addition element (4) configured to add a feed-forward speed (Vff) and an output from the speed instruction operator (2) to obtain a speed instruction value (V c ), whereby the feed-forward speed (Vff) is determined by a differentiation of the position command value (P c ) is obtained; a torque command operator (6, 86) configured to detect a deviation between the speed command value (V c ) and a speed detection value (V d ) to output a feedback torque (Tfb), wherein the speed detection value (V d ) is obtained by detecting the speed of the moving part with a speed detector or by differentiating the position detection value; a second adder (9) configured to add a feed-forward torque (Tff) and the feedback torque (Tfb) to obtain a torque command value (T c ), wherein the feed-forward torque (Tff) is obtained by differentiating the feed-forward speed (Vff) and multiplying the differentiated value by an inertia (8, 88) of the movable part converted into a motor shaft; a drive unit configured to drive the servo motor via the torque command value (T c ) to be controlled; a runout amount correction device (31, 51, 61, 71) configured to correct the deviation (Pdif) between the position instruction value (P c) and the position detection value from the position detector as a reference signal, wherein the runout amount correction device (31, 51, 61, 71) is configured to calculate a position correction amount (Padd) from rotation angle information (θ) of the main spindle and the reference signal, the rotation angle information (θ) being obtained from the higher-level device; and a third addition element (36) configured to calculate the position instruction value (P c ) with the position correction amount (Padd) to obtain the position instruction value (P c ) to correct, whereby the runout amount correction device (31, 51, 61, 71) is configured to estimate a runout amount of a cutting edge (42) of the tool (41) from the reference signal, wherein the runout amount correction device (31, 51, 61, 71) is configured to calculate the position correction amount (Padd) so as to compensate for influences of the respective cutting edges (42) appearing in the reference signal. [2] A position control device of a feed axis for a machine tool, wherein the machine tool rotates a tool (41) attached to a main spindle to machine a workpiece (43), the machine tool includes a feed axis mechanism (10, 90) with a servo motor for driving a load in a predetermined linear axis direction, and the position control device comprises: a position detector configured to detect a position of a movable part of the feed axis mechanism (10, 90) so as to detect the position of the movable part in accordance with a position instruction value (P c ) to control a feed axis from a higher-level device; a speed instruction operator (2) configured to detect a deviation (Pdif) between the position instruction value (P c ) and a position detection value from the position detector; a first addition element (4) configured to add a feed-forward speed (Vff) and an output from the speed instruction operator (2) to obtain a speed instruction value (V c ), whereby the feed-forward speed (Vff) is determined by a differentiation of the position command value (P c ) is obtained; a torque command operator (6, 86) configured to detect a deviation between the speed command value (V c ) and a speed detection value (V d ) to output a feedback torque (Tfb), wherein the speed detection value (V d ) is obtained by detecting the speed of the moving part with a speed detector or by differentiating the position detection value; a second addition element (9) configured to add a feed-forward torque (Tff) and the feedback torque (Tfb) to obtain a torque command value (T c ), wherein the feed-forward torque (Tff) is obtained by differentiating the feed-forward speed (Vff) and multiplying the differentiated value by an inertia (8, 88) of the movable part converted into a motor shaft; a drive unit configured to drive the servo motor via the torque command value (T c ) to be controlled; a runout amount correction device (31, 51, 61, 71) configured to use the feedback torque (Tfb) as a reference signal, wherein the runout amount correction device (31, 51, 61, 71) is configured to calculate a position correction amount (Padd) from rotation angle information (θ) of the main spindle and the reference signal, and the rotation angle information (θ) is obtained from the higher-level device; and a third addition element (36) configured to calculate the position instruction value (P c ) with the position correction amount (Padd) to obtain the position instruction value (P c ) to correct, whereby the runout amount correction device (31, 51, 61, 71) is configured to estimate a runout amount of a cutting edge (42) of the tool (41) from the reference signal, the runout amount correction device (31, 51, 61, 71) is configured to calculate the position correction amount (Padd) so as to compensate for influences from the respective cutting edges (42) appearing in the reference signal. [3] A position control device of a feed axis for a machine tool, wherein the machine tool rotates a tool (41) attached to a main spindle to machine a workpiece (43), the machine tool includes a feed axis mechanism (10, 90) with a servo motor for driving a load in a predetermined linear axis direction, and the position control device comprises: a position detector configured to detect a position of a movable part of the feed axis mechanism (10, 90) so as to detect the position of the movable part in accordance with a position instruction value (P c ) to control a feed axis from a higher-level device; a speed instruction operator (2) configured to detect a deviation (Pdif) between the position instruction value (P c ) and a position detection value from the position detector; a first addition element (4) configured to add a feed-forward speed (Vff) and an output from the speed instruction operator (2) to obtain a speed instruction value (V c ), whereby the feed-forward speed (Vff) is determined by a differentiation of the position command value (P c ) is obtained; a torque command operator (6, 86) configured to detect a deviation between the speed command value (V c ) and a speed detection value (V d ) to output a feedback torque (Tfb), wherein the speed detection value (V d ) is obtained by detecting the speed of the moving part with a speed detector or by differentiating the position detection value; a second addition element (9) configured to add a feed-forward torque (Tff) and the feedback torque (Tfb) to obtain a torque command value (T c ), wherein the feed-forward torque (Tff) is obtained by differentiating the feed-forward speed (Vff) and multiplying the differentiated value by an inertia (8, 88) of the movable part converted into a motor shaft; a drive unit configured to drive the servo motor via the torque command value (T c ) to be controlled; a disturbance observer configured to detect a difference between a speed detection value (V d ) having an inverse characteristic of a nominal value of the feed axis mechanism (10, 90) and the torque command value (T c ) into a low-pass filter (23, 93) to obtain an estimated disturbance value, wherein the feed axis mechanism (10, 90) is formed from the servo motor and the load; a runout amount correction device (31, 51, 61, 71) configured to use the estimated disturbance value as a reference signal, wherein the runout amount correction device (31, 51, 61, 71) is configured to calculate a position correction amount (Padd) from rotation angle information (θ) of the main spindle and the reference signal, the rotation angle information (θ) being obtained from the higher-level device; and a third addition element (36) configured to calculate the position instruction value (P c ) with the position correction amount (Padd) to obtain the position instruction value (P c ) to correct, whereby the runout amount correction device (31, 51, 61, 71) is configured to estimate a runout amount of a cutting edge (42) of the tool (41) from the reference signal, wherein the runout amount correction device (31, 51, 61, 71) is configured to calculate the position correction amount (Padd) so as to compensate for influences from the respective cutting edges (42) appearing in the reference signal. [4] A feed axis position control device in the machine tool according to any one of claims 1 to 3, wherein the runout amount correcting device (31, 51, 61, 71) includes: a peak detection unit (32, 52, 72) configured to detect a peak in a waveform and to make the peak coincide with each of the cutting edges (42), the peak appearing in the reference signal due to an influence of each of the cutting edges (42); an increase and decrease estimation unit (33) configured to estimate an increase or decrease in a machining allowance of each of the cutting edges (42) from a peak value in the reference signal for each of the cutting edges (42), the peak value being detected by the peak detection unit (32, 52, 72); a runout amount estimation unit (34) configured to estimate a runout amount of each of the cutting edges (42) from the increase or decrease in the machining allowance of each of the cutting edges (42), the increase or decrease being estimated by the increase-and-decrease estimation unit (33); and a correction amount determination unit (35, 55, 65) configured to determine the position correction amount (Padd), wherein the position correction amount (Padd) is determined such that a correction amount is applied based on the runout amount of each of the cutting edges (42) at a time when the respective cutting edges (42) machine the workpiece (43), the runout amount being estimated by the runout amount estimation unit (34). [5] Position control device of the feed axis in the machine tool according to one of claims 1 to 3, wherein: the machine tool includes at least two of the feed axis mechanisms (10, 90), the feed axis mechanisms (10, 90) are associated with a first axis and a second axis, and the second axis is installed separately from the first axis, and the out-of-roundness correction device (31, 51, 61, 71) contains: a peak detection unit (32, 52, 72) configured to detect a peak in a waveform and to make the peak coincide with each of the cutting edges (42), the peak appearing in the reference signal associated with the first axis due to an influence of each of the cutting edges (42); an increase and decrease estimation unit (33) configured to estimate an increase or decrease in a machining allowance of each of the cutting edges (42) from a peak value in the reference signal for each of the cutting edges (42), the peak value being detected by the peak detection unit (32, 52, 72); a runout amount estimation unit (34) configured to estimate a runout amount of each of the cutting edges (42) from an increase or decrease in the machining allowance of each of the cutting edges (42), the increase or decrease being estimated by the increase-and-decrease estimation unit (33); and a correction amount determination unit (35, 55, 65) configured to determine the position correction amount (Padd) associated with the second axis, wherein the position correction amount (Padd) is determined such that a correction amount based on the runout amount of each of the cutting edges (42) is applied at a time when the respective cutting edges (42) machine the workpiece (43), and the runout amount is estimated by the runout amount estimation unit (34). [6] Position control device of the feed axis in the machine tool according to one of claims 1 to 3, wherein: the machine tool includes the feed axis mechanism (10, 90) associated with a plurality of respective feed axes, and the out-of-roundness correction device (31, 51, 61, 71) contains: a peak detection unit (32, 52, 72) configured to detect a peak in a waveform and to make the peak coincide with each of the cutting edges (42), the peak appearing in the reference signal due to an influence of each of the cutting edges (42); an increase and decrease estimation unit (33) configured to estimate an increase or decrease in a machining allowance of each of the cutting edges (42) from a peak value in the reference signal for each of the cutting edges (42), the peak value being detected by the peak detection unit (32, 52, 72); a runout amount estimation unit (34) configured to estimate a runout amount of each of the cutting edges (42) from the increase or decrease in the machining allowance of each of the cutting edges (42), the increase or decrease being estimated by the increase-and-decrease estimation unit (33); and a correction amount determination unit (35, 55, 65) configured to determine the position correction amount (Padd) for each of the feed axes, wherein the position correction amount (Padd) is determined such that a correction amount based on the runout amount of each of the cutting edges (42) is applied at a time when the respective cutting edges (42) machine the workpiece (43), and the runout amount is estimated by the runout amount estimation unit (34). [7] Position control device of the feed axis in the machine tool according to one of claims 1 to 3, wherein: the machine tool includes at least two of the feed axis mechanisms (10, 90), wherein the feed axis mechanisms (10, 90) are associated with a first axis and a second axis, wherein the second axis is installed separately from the first axis, and the out-of-roundness correction device (31, 51, 61, 71) contains: a peak detection unit (32, 52, 72) configured to detect a peak in a waveform and to make the peak coincide with each of the cutting edges (42), wherein the peak appears in a synthesized signal due to an influence of each of the cutting edges (42), and the synthesized signal is obtained by synthesizing the reference signal associated with the first axis and the reference signal associated with the second axis; an increase and decrease estimation unit (33) configured to estimate an increase or decrease in a machining allowance of each of the cutting edges (42) from a peak value in the synthesized signal for each of the cutting edges (42), the peak value being detected by the peak value detection unit (32, 52, 72); a runout amount estimation unit (34) configured to estimate a runout amount of each of the cutting edges (42) from the increase or decrease in the machining allowance of each of the cutting edges (42), the increase or decrease being estimated by the increase-and-decrease estimation unit (33); and a correction amount determination unit (35, 55, 65) configured to determine the position correction amount (Padd) of each of the axes, wherein the position correction amount (Padd) is determined such that a correction amount based on the runout amount of each of the cutting edges (42) is applied at a time when the respective cutting edges (42) machine the workpiece (43), and the runout amount is estimated by the runout amount estimation unit (34). [8] Position control device of the feed axis in the machine tool according to claim 6, wherein: the machine tool includes a main spindle control device, the main spindle control device being configured to control a rotational speed of the main spindle in accordance with a speed command value (V c ) from a higher-level device, and the main spindle control device includes: a torque command operator (6, 86) configured to detect a deviation between the speed command value (V c ) and a speed detection value (V d ) to obtain a torque command value (T c ), where the speed detection value (V d ) is detected by a main spindle speed detector mounted on the main spindle, or alternatively, the speed detection value (V d ) is obtained by differentiating a position detection value detected by a main spindle position detector mounted on the main spindle; and a drive unit configured to drive a main spindle motor via the torque command value (T c ) and the runout amount correction device (31, 51, 61, 71) is configured to correct the torque command value (Tc ) as the reference signal. [9] Position control device of the feed axis in the machine tool according to claim 6, wherein: the machine tool includes a main spindle control device, the main spindle control device being configured to control a rotational speed of the main spindle in accordance with a speed command value (V c ) from a higher-level device, and the main spindle control device includes: a torque command operator (6, 86) configured to detect a deviation between the speed command value (V c ) and a speed detection value (V d ) to output a feedback torque (Tfb), wherein the speed detection value (V d) is obtained by detecting with a main spindle speed detector mounted on the main spindle, or alternatively, the speed detection value (V d ) is obtained by differentiating a position detection value detected by a main spindle position detector mounted on the main spindle; an adder (89) configured to add a feed-forward torque (Tff) and the feedback torque (Tfb) to obtain a torque command value (T c ), whereby the feed-forward torque (Tff) is determined by differentiating the speed command value (V c ) and multiplying the differentiated value by an inertia (8, 88) of the moving part of the main spindle converted into a motor shaft; and a drive unit configured to drive a main spindle motor via the torque command value (T c ) and the runout amount correcting device (31, 51, 61, 71) is configured to use the feedback torque (Tfb) obtained from the main spindle control device as the reference signal. [10] Position control device of the feed axis in the machine tool according to claim 6, wherein: the machine tool includes a main spindle control device, the main spindle control device being configured to control a rotational speed of the main spindle in accordance with a speed command value (V c ) from a higher-level device, and the main spindle control device includes: a torque command operator (6, 86) configured to detect a deviation between the speed command value (V c ) and a speed detection value (V d ) to output a feedback torque (Tfb), wherein the speed detection value (Vd ) is obtained by detecting with a main spindle speed detector mounted on the main spindle, or alternatively, the speed detection value (V d ) is obtained by differentiating a position detection value detected by a main spindle position detector mounted on the main spindle; an adder (89) configured to add a feed-forward torque (Tff) and the feedback torque (Tfb) to obtain a torque command value (T c ), whereby the feed-forward torque (Tff) is determined by differentiating the speed command value (V c ) and multiplying the differentiated value by an inertia (8, 88) of the moving part of the main spindle converted into a motor shaft; a drive unit configured to drive a main spindle motor via the torque command value (T c ) and a disturbance observer configured to detect a difference between a value obtained by multiplying the speed detection value (V d ) with an inverse characteristic of a nominal value of the main spindle motor and the torque command value (T c ) into a low-pass filter (23, 93) to obtain an estimated disturbance value, and the runout amount correcting device (31, 51, 61, 71) is configured to use the estimated disturbance value obtained from the main spindle control device as the reference signal. [11] The position control device of the feed axis in the machine tool according to any one of claims 1 to 10, wherein the position control device includes a notification unit or a screen output unit (11), the notification unit is configured to notify an excess of a level of the position correction amount (Padd) over a predetermined alarm detection level of the runout amount of the cutting edge (42), the screen output unit (11) being configured to display the position correction amount (Padd) to attract the attention of the operator.

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