DE112020000649B4 - Industrial machine, device for determining eccentricity, method for determining eccentricity and program - Google Patents

Abstract

An industrial machine comprising:a tool (131);a rotating motor (123) configured to rotate the tool (131) about a central axis of the tool (131);a rotation angle sensor (136) configured to measure a rotation angle of the tool (131); anda control device (140) configured to control the rotating motor (123),wherein the control device (140) includes:a rotation command unit (416) configured to output a rotation command to the rotating motor (123);a rotation angle detection unit (410) configured to detect a measurement value of the rotation angle from the rotation angle sensor (136);characterized in thatthe industrial machine further comprises:an actuator (133) configured to move the tool (131) in a cutting direction; anda displacement sensor (134) designed to measure displacement of the tool (131) in the cutting direction; andthe control device (140) is further designed to control the actuator (133), and includes:a vibration detection unit (411) designed to detect a displacement measurement value from the displacement sensor (134) relating to vibration of the tool (131) in the cutting direction;wherein the control device (140) is designed to repeat the detection of the measurement values until time series of measurement values relating to a predetermined period of time or a predetermined number of rotations have been detected, andan eccentricity determination unit (418) designed to detect a vibration vector relating to a deviation between a center of gravity of the tool (131) and the central axis based on the time series of measurement values of the angle of rotation and the time series of measurement values of the displacement.

Description

Technical area

The present invention relates to an industrial machine, an eccentricity determining device, an eccentricity determining method and a program. The present application claims priority to Japanese Patent Application No. 1-800-244 filed in Japan on March 29, 2019. 2019-068529 , the contents of which are incorporated herein by reference.

Technical background

Patent Document 1 discloses a technology for a turning and broaching machine capable of calculating an amount of unbalance of a crankshaft made of raw material.

Patent Document 2 describes a grinding device capable of determining an appropriate timing to start a reverse grinding process in consideration of the deceleration of a grinding wheel in an overall process of grinding the surface of a workpiece, the entire process consisting of rough grinding, reverse grinding, and fine grinding.

Patent Document 3 describes a machine tool capable of monitoring manufacturing quality in real time during manufacturing and preventing products with poor manufacturing quality. To this end, error data of each part of a workpiece in the rotation direction with respect to a target shape and unevenness of the workpiece due to vibration are calculated based on state data collected during manufacturing. By using a simulation model, manufacturing quality that cannot be directly measured can be calculated based on the state data.

Patent Document 4 describes a grinding machine that enables precision machining by preventing dimensional errors in a workpiece after machining and deterioration of surface roughness due to thermal deformation of the workpiece.

State-of-the-art documents

Patent document

• Patent Document 1 Unexamined Japanese Patent Application, JP 2015- 44 249 A
• Patent Document 2 Unexamined Japanese Patent Application, JP H08- 294 864 A
• Patent Document 3 Unexamined Japanese Patent Application, JP 2018- 1 301 A
• Patent Document 4 Unexamined Japanese Patent Application, JP 2012- 115 987 A

Summary of the invention

Problems to be solved with the invention

In a grinding machine that processes a workpiece with a rotating grinding wheel, the center of gravity of the grinding wheel preferably coincides with the fulcrum of the grinding wheel. If the center of gravity of the grinding wheel and the fulcrum of the grinding wheel are shifted from each other, the grinding wheel vibrates with the rotation of the grinding wheel, and the accuracy of processing the workpiece decreases. Therefore, it is necessary to attach a correction weight to the grinding wheel so that the center of gravity of the grinding wheel and the fulcrum substantially coincide.

As a method for determining an attachment position of the correction weight, a method using a balance monitor is known. The balance monitor includes a rotation sensor that measures the rotation speed of a grinding wheel and an acceleration sensor that measures vibration of a grinding wheel carrier and detects a deviation of a center of gravity based on

measured values of the rotation sensor and the acceleration sensor. To determine the center of gravity of the grinding wheel, it is necessary to calculate an amplitude of vibration of the grinding wheel. When the amplitude is calculated based on the acceleration sensor, it is necessary to perform multiple integration of a measured value. Therefore, calculation of the deviation of the center of gravity using the acceleration sensor is likely to be affected by noise contained in the measured value of the acceleration sensor.

The object of the present invention is to provide an industrial machine, a device for determining eccentricity, a method for determining eccentricity and a program with which the above-described problem of the present invention is solved.

Means to solve the problem

This problem is solved with the features of the independent patent claims.

Effects of the invention

According to the invention, the industrial machine determines the center of gravity of a tool based on the measured value of displacement from the displacement sensor. By using the measured value of displacement, it is not necessary to perform gravity integration of the measured value, and thus, unlike a case where an acceleration sensor is used, it is possible to determine a value related to the eccentricity of the tool without being influenced by noise.

Short description of the drawings

• 1 is a plan view showing a structure of a grinding machine according to a first embodiment.
• 2 is a schematic block diagram showing a configuration of a control device according to the first embodiment.
• 3 is a flowchart illustrating a process for balancing a grindstone according to the first embodiment.
• 4 is a flowchart illustrating a method of determining a vibration vector by the control device according to the first embodiment.
• 5A is a diagram showing an example of amplitudes of chatter vibration of a grinding wheel before and after balancing the grinding wheel using the control device according to the first embodiment.
• 5B is a diagram showing an example of amounts of chatter vibration of a grinding wheel before and after balancing the grinding wheel using the control device according to the first embodiment.

Implementation of the invention

First embodiment

An embodiment will be described in detail below with reference to the drawings.

1 is a plan view showing a structure of a grinding machine according to the first embodiment. The grinding machine is an example of an industrial machine.

Structure of the grinding machine

A grinding machine 100 includes a base 110, a receiving device 120, a grinding wheel carrier 130, a control device 140, and a display device 150. The base 110 is installed on a floor surface of a factory. The receiving device 120 and the grinding wheel carrier 130 are provided on an upper surface of the base 110. The receiving device 120 receives both ends of a workpiece W and rotates the workpiece W around a spindle. The grinding wheel carrier 130 carries a grinding wheel 131 for machining the workpiece W received by the receiving device 120. The grinding wheel 131 is an example of a tool.

Hereinafter, a direction perpendicular to the spindle on the top of the base 110 is referred to as an X direction, a direction in which the spindle extends is referred to as a Y direction, and a direction perpendicular to the top of the base 110 is referred to as a Z direction. That is, in the following description, the positional relationship of the grinding machine 100 is described with reference to a three-dimensional rectangular coordinate system including an X axis, a Y axis, and a Z axis.

The base 110 includes a Y-axis guide portion 111 that supports the grinding wheel carrier 130 so that it can be moved in the Y-axis direction, and a Y-axis actuator 112 that moves the grinding wheel carrier 130 along the Y-axis guide portion 111 in the Y-axis direction. The Y-axis actuator 112 may be implemented as a linear motor or may be implemented as a combination of a ball screw and a rotary motor.

The cradle 120 includes a headstock 121 supporting one end of the workpiece W having a substantially cylindrical shape and a tailstock 122 supporting the other end of the workpiece W. The headstock 121 includes a rotary motor 123 that rotates the workpiece W about an axis thereof.

The grinding wheel carrier 130 includes a grinding wheel 131, an X-axis guide section 132, an X-axis actuator 133, a displacement sensor 134, a rotating motor 135, and a rotation angle sensor 136.

The grinding wheel 131 is formed in a disk shape and is rotated around its central axis by the rotating motor 135. The central axis of the grinding wheel 131 is parallel to the Y-axis. Abrasive grains for machining the workpiece W are provided on the outer peripheral surface of the grinding wheel 131. On a side surface of the grinding wheel 131, a plurality of mounting holes for attaching a correction weight are provided at equal intervals on the same circumference.

The X-axis guide section 132 supports the grinding wheel carrier 130 so that it can be moved in the X-axis direction with respect to the base 110.

The X-axis actuator 133 moves the grinding wheel 131 in the X-axis direction along the X-axis guide portion 132. The X-axis direction is a cutting direction of the grinding wheel 131. The X-axis actuator 133 may be configured as a linear motor, or may be configured as a combination of a ball screw and a rotary motor. The cutting direction is perpendicular to a direction of the fulcrum.

The displacement sensor 134 measures displacement of the grinding wheel carrier 130 in the X-axis direction with respect to the base 110. The displacement sensor 134 is formed, for example, by a code ruler.

The rotating motor 135 rotates the grinding wheel 131 around the central axis. The rotation angle sensor 136 measures a rotation angle of the grinding wheel 131. The rotation angle sensor 136 is formed, for example, by a rotary encoder.

That is, in the grinding machine 100 according to the first embodiment, the workpiece W is accommodated between the headstock 121 and the tailstock 122 of the locating device 120, and the outer peripheral surface of the workpiece W is ground with the grinding wheel 131.

Configuration of the control device

2 is a schematic block diagram showing a configuration of the control device according to the first embodiment.

The controller 140 controls the Y-axis actuator 112, the rotary motor 123, the X-axis actuator 133, and the rotary motor 135. The controller 140 includes a processor 141, a main memory 143, a memory 145, and an interface 147. The processor 141 reads a program from the memory 145, loads the program into the main memory 143, and executes processing according to the program. The processor 141 saves a storage area in the main memory 143 according to the program.

The program may implement some of the functions that the controller 140 has. For example, the program may implement functions by combining with another program already stored in the memory 145 or by combining with another program installed in another device. Moreover, in another embodiment, the controller 140 may include a customized large scale integrated circuit (LSI), such as a programmable logic device (PLD). Examples of the PLD include a programmable array logic (PAL), a generic array logic (GAL), a complex programmable logic device (CPLD), or a field programmable gate array (FPGA). In this case, some or all of the functions implemented by the processor 141 may be implemented by the integrated circuit.

Examples of the memory 145 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a CD-ROM (compact disc read only memory), a DVD-ROM (digital versatile disc read only memory), a semiconductor memory, or the like. The memory 145 may be an internal medium directly connected to a bus of the controller 140, or an external medium connected to the controller 140 via the interface 147 or a data transmission line. Furthermore, when the program is distributed to the controller 140 via a data transmission line, the controller 140 that received the distribution may load the program into the main memory 143 and execute the processing described above. In at least one embodiment, the memory 145 is a non-volatile physical storage medium.

The processor 141 functions by executing a program as a unit 410 for detecting a rotation angle, a unit 411 for detecting vibration, a unit 412 for calculating a target position, a unit 413 for calculating a target state variable, a unit 414 for calculating a command value, a unit 415 for issuing a command, a unit 416 for a rotation command, a feedback unit 417, a unit 418 for determining eccentricity, a unit 419 for setting a correction weight, a unit 420 for determining a amount of vibration and a unit 421 for display control.

The rotation angle detection unit 410 detects a measurement value from the rotation angle sensor 136. That is, the rotation angle detection unit 410 detects a measurement value of a rotation angle of the grinding wheel 131.

The vibration detection unit 411 detects a measurement value from the displacement sensor 134. That is, the vibration detection unit 411 detects a measurement value of displacement of the grinding wheel 131 in the X-axis direction. Moreover, the measurement value of displacement in the X-axis direction is a value related to vibration of the grinding wheel 131 in the cutting direction.

The target position calculation unit 412 calculates a predetermined specific position as a target position of the grinding wheel 131 when balancing the grinding wheel 131.

The target state quantity calculation unit 413 calculates a target value of a state quantity related to displacement of the grinding wheel 131 based on the target position calculated by the target position calculation unit 412. That is, the target state quantity calculation unit 413 calculates values of a target speed, a target acceleration, and a target jerk of the grinding wheel 131 in the X-axis direction.

The command value calculation unit 414 calculates a current command value for the X-axis actuator 133 based on the target value of the state quantity of the grinding wheel 131 and a feedback signal from the feedback unit 417. That is, the command value calculation unit 414 converts the target value of the state quantity of the grinding wheel 131 into a current value for achieving the target value and adds the value of the feedback signal to the current value to calculate the current command value.

The command output unit 415 outputs the current command value calculated by the command value calculation unit 414 to the X-axis actuator 133. The rotation command unit 416 outputs a rotation command for rotating the grinding wheel 131 by a predetermined number of revolutions to the rotary motor 135.

The feedback unit 417 outputs a feedback signal related to driving the X-axis actuator 133 based on a difference between the measured value of displacement of the grinding wheel 131 in the X-axis direction detected by the vibration detection unit 411 and the target position of the grinding wheel 131 determined by the target position calculation unit 412.

The eccentricity determination unit 418 determines a vibration vector based on the measured value of displacement of the grinding wheel 131 in the X-axis direction detected by the vibration detection unit 411 and the measured value of rotation angle of the grinding wheel 131 detected by the rotation angle detection unit 410. The vibration vector indicates a direction and an amount with respect to a phase reference value (e.g., 0°) that occurs when the grinding wheel 131 is displaced caused by rotation of the grinding wheel 131 whose central axis and center of gravity do not coincide with each other. That is, the vibration vector is a value related to a difference between the position of the center of gravity of the grinding wheel 131 and the central axis.

The correction weight determining unit 419 determines the position of the attachment hole to which the correction weight is to be attached and the weight of the correction weight based on the position of the center of gravity determined by the eccentricity determining unit 418 and the position of the attachment hole of the grinding wheel 131 so as to substantially coincide the fulcrum and the center of gravity of the grinding wheel 131.

The vibration amount determination unit 420 determines the amplitude of the chatter vibration caused by the eccentricity of the grinding wheel 131 based on the measured value of displacement in the X-axis direction of the grinding wheel 131 detected by the vibration detection unit 411 and the measured value of the rotation angle of the grinding wheel 131 detected by the rotation angle detection unit 410. Hereinafter, the amplitude of the chatter vibration is also referred to as an amount of vibration. That is, the vibration amount determination unit 420 determines the amplitude of a frequency band corresponding to the frequency of rotation of the grinding wheel by performing an appropriate filtering process (e.g., a bandpass filtering process) from time series of the measured values of displacement in the X-axis direction, thereby determining the amount of vibration to which the chatter vibration relates. In addition, the frequency of rotation of the grinding wheel is determined based on the measured value of the rotation angle sensor 136.

The display control unit 421 outputs to the display device 150 display signals of a screen displaying the position of the attachment hole and the weight of the correction weight set by the correction weight setting unit 419 and a screen displaying the amount of vibration determined by the vibration amount determining unit 420 when the grinding wheel 131 is balanced.

Process for balancing the grinding wheel

The following describes a procedure for balancing the grinding wheel 131 of the grinding machine 100.

3 is a flowchart illustrating a process for balancing the grinding wheel according to the first embodiment.

The operator operates the controller 140 to start a balancing mode (step S1). Then, the controller 140 rotates the grinding wheel 131 in a state where no test weight is added to the grinding wheel 131, and determines a vibration vector in a manner described later (step S2). The test weight is a weight added to measure unbalance of the grinding wheel 131. Then, the operator adds a test weight in a predetermined mounting hole related to a reference phase of the grinding wheel 131 (step S3). Then, the controller 140 rotates the grinding wheel 131 in a state where the test weight is added to the grinding wheel 131, and determines a vibration vector in a manner described later (step S4).

Then, the correction weight setting unit 419 of the controller 140 calculates a weight W ₁ of an ideal correction weight based on expression (1) (step S5). The ideal correction weight is a virtual correction weight that can be attached to an arbitrary position of the grinding wheel 131 regardless of the position of the attachment hole of the grinding wheel 131. The actual attachment position of the correction weight is limited by the position of the attachment hole.
[Equation 1] $$\begin{array}{l}{\mathrm{<figure-callout\; id="1"\; label="W"\; filenames="DE112020000649B4\_0004.png,DE112020000649B4\_0006.png"\; state="\{\{state\}\}">W</figure-callout>}}_1=\frac{A_1}{A_2}{W}_0\\ {\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="DE112020000649B4\_0006.png"\; state="\{\{state\}\}">A</figure-callout>}}_2=\sqrt{A_1^2+A_0^2-2A_1{A}_0\text{cos}\left({\mathrm{<figure-callout\; id="1"\; label="\theta "\; filenames="DE112020000649B4\_0004.png,DE112020000649B4\_0006.png"\; state="\{\{state\}\}">\theta </figure-callout>}}_1-{\theta }_0\right)}\end{array}$$

In equation (1), W ₀ is the weight of the test weight. A ₀ is an amplitude component of the vibration vector in a state where the test weight determined in step S2 is not added. A ₁ is an amplitude component of the vibration vector in a state where the test weight determined in step S4 is added. A ₂ is an amplitude component of the vibration vector that cancels the eccentricity. θ ₀ is a phase component of the vibration vector in a state where the test weight determined in step S2 is not added. θ ₁ is a phase component of the vibration vector in a state where the test weight determined in step S4 is added.

Then, the correction weight setting unit 419 sets an attachment angle φ1 of the ideal correction weight based on expression (2) (step S6).
[Expression 2] $${\mathrm{<figure-callout\; id="1"\; label="\phi "\; filenames="DE112020000649B4\_0004.png,DE112020000649B4\_0006.png"\; state="\{\{state\}\}">\varphi </figure-callout>}}_1=180-{\text{cos}}^{-1}\left(A_1^2-A_0^2-\frac{A_2^2}{2A_0{A}_2}\right)$$

Then, the correction weight setting unit 419 determines the weight W ₁ and an attachment angle φ ₁ of the correction weight, as well as the positions φ ₂ and φ ₃ of the two attachment holes closest to the attachment angle φ ₁ , and sets the weight W ₂ and W ₃ of the correction weights to be attached to each attachment hole based on expression (3) (step S7).
[Expression 3] $$\begin{array}{l}{\mathrm{<figure-callout\; id="2"\; label="W"\; filenames="DE112020000649B4\_0006.png"\; state="\{\{state\}\}">W</figure-callout>}}_2=\frac{\text{sin}\left({\mathrm{<figure-callout\; id="3"\; label="\phi "\; filenames="DE112020000649B4\_0006.png"\; state="\{\{state\}\}">\varphi </figure-callout>}}_3-{\varphi }_1\right)}{\text{sin}\left({\mathrm{<figure-callout\; id="3"\; label="\phi "\; filenames="DE112020000649B4\_0006.png"\; state="\{\{state\}\}">\varphi </figure-callout>}}_3-{\varphi }_2\right)}{W}_1\\ {\mathrm{<figure-callout\; id="3"\; label="W"\; filenames="DE112020000649B4\_0006.png"\; state="\{\{state\}\}">W</figure-callout>}}_3=\frac{\text{sin}\left({\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE112020000649B4\_0006.png"\; state="\{\{state\}\}">\varphi </figure-callout>}}_2-{\varphi }_1\right)}{\text{sin}\left({\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE112020000649B4\_0006.png"\; state="\{\{state\}\}">\varphi </figure-callout>}}_2-{\varphi }_3\right)}{\mathrm{<figure-callout\; id="1"\; label="W"\; filenames="DE112020000649B4\_0004.png,DE112020000649B4\_0006.png"\; state="\{\{state\}\}">W</figure-callout>}}_1\end{array}$$

Then, the display control unit 421 outputs to the display device 150 a display signal of a screen showing the positions φ ₂ and φ ₃ of the mounting holes and the weight W ₂ and W ₃ of the correction weights set in step S7 (step S8).

Then, the operator removes the test weight from the grinding wheel 131 (step S9) and adds the correction weight with the weight that has been indicated to the attachment hole at the indicated position (step S10). Then, the operator rotates the grinding wheel 131 in a state where the correction weight is added to the grinding wheel 131 and determines a vibration vector in a manner described later (step S11). Then, the vibration amount determination unit 420 determines an amplitude of a frequency band corresponding to a frequency of rotation of the grinding wheel. by means of an appropriate filtering process (e.g., a band-pass filtering process) from time series of measured values of displacement in the X-axis direction, thereby determining an amount of vibration (step S12). The display control unit 421 outputs a display signal of a screen representing the determined amount of vibration of the grinding wheel 131 to the display device 150 (step S13).

The operator determines whether the displayed amount of vibration is equal to or greater than a reference value (step S14). If the amount of vibration is equal to or greater than the reference value (step S14: YES), the process returns to step S3 and balancing is further performed. If the amount of vibration is less than the reference value (step S14: NO), the operator stops balancing.

Method for determining a vibration vector

4 is a flowchart illustrating a method of determining a vibration vector by the controller according to the first embodiment. When the controller 140 starts a process of determining a vibration vector in steps S2, S4 or S11, the target position calculation unit 412 calculates a predetermined specific position as a target position of the grinding wheel 131 (step S31). The target state quantity calculation unit 413 calculates target values of a state quantity (speed, acceleration and jerk) related to displacement of the grinding wheel 131 based on the target position calculated in step S31 (step S32).

The command value calculation unit 414 converts the target values of the state quantity of the grinding wheel 131 into a current value (torque value) for achieving the target values (step S33). The command value calculation unit 414 calculates a current command value V by adding a value of the feedback signal output from the feedback unit 417 to the current value converted in step S33 (step S34). The command output unit 415 outputs the current command value calculated in step S34 to the X-axis actuator 133 (step S35). Further, the rotation command unit 416 outputs a rotation command for rotating the grinding wheel 131 at a predetermined rotation speed to the rotary motor 135 (step S36).

The rotation angle detection unit 410 detects a measured value of a rotation angle of the grinding wheel 131 from the rotation angle sensor 136, and the vibration detection unit 411 detects a measured value of displacement of the grinding wheel 131 in the X-axis direction from the displacement sensor 134 (step S37). The detected measured value is stored in the main memory 143 or the like in association with time. The feedback unit 417 outputs a feedback signal related to driving the X-axis actuator 133 based on the measured value of displacement detected in step S37 and the target position calculated in step S31 (step S38). The feedback signal can be determined by proportional control, sliding state control, and other methods.

The eccentricity determination unit 418 determines whether a required number of measurement values for calculating the vibration vector have been collected (step S39). For example, the eccentricity determination unit 418 may determine whether measurement values relating to a predetermined period of time have been collected, or it may determine whether measurement values relating to a predetermined number of rotations have been collected. If a required number of measurement values for calculating a vibration vector have not been collected (step S39: NO), the process returns to step S31 and collection of measurement values is continued. On the other hand, if a required number of measurement values for calculating a vibration vector have been collected (step S39: YES), the eccentricity determination unit 418 determines a vibration vector based on time series of the collected measurement values of displacement (step S40). Specifically, the eccentricity determination unit 418 determines a rotation angle of the grinding wheel 131 at a timing of a peak of a waveform of the time series of the collected measured values of displacement as a phase component of the vibration vector. Further, the eccentricity determination unit 418 determines an amplitude of the waveform of the time series of the collected measured values of displacement as an amplitude component of the vibration vector.

Function of the control device when machining the workpiece

When the workpiece W is machined after the balancing of the grinding wheel 131 is completed, the operator attaches the workpiece W to the holding device 120, operates the control device 140 and activates the machining mode. Accordingly, the control device 140 determines the position of a contour of the workpiece W facing the grinding wheel 131 based on the angle of rotation of the rotating motor 123 and the target shape of the workpiece W. piece W as the target position of the grinding wheel 131 and machines the workpiece W. When machining the workpiece W, the rotation angle detection unit 410 and the vibration detection unit 411 collect measured values from the displacement sensor 134 and the rotation angle sensor 136 of the grinding wheel 131. The controller 140 performs processing from step S12 to step S13 based on the collected measured values and displays the amount of vibration of the grinding wheel 131 on the display device 150. Thus, the operator can check the unbalance of the grinding wheel 131 every time the workpiece W is machined. Furthermore, the vibration amount determination unit 420 determines the amount of vibration corresponding to the frequency of rotation of the grinding wheel 131 in the step S12 and is thereby able to extract the amount of vibration due to the chatter vibration of the grinding wheel 131 from time series of the measured values of displacement including vibration caused by machining of the workpiece W. That is, the vibration amount determination unit 420 is able to correctly determine the amount of vibration due to chatter vibration even when machining the workpiece W.

Function and effects

As described above, the control device 140 according to the first embodiment determines the vibration vector of the grinding wheel 131 based on the measured values detected by the rotation angle sensor 136 and the displacement sensor 134 of the grinding wheel 131. Since the control device 140 does not need to perform multiple integration of the measured values using the measured values of displacement, it is possible to determine the center of gravity without being influenced by noise, unlike a case where an acceleration sensor is used.

5A and 5B are diagrams showing examples of chatter vibration of a grinding wheel before and after balancing the grinding wheel using the control device according to the first embodiment. When balancing is performed according to the first embodiment, as shown in 5A and 5B shown, possible, chatter vibration of the grinding wheel 131, which occurred before balancing, by means of the 3 to the same level as other disturbances. That is, in the case of the 5A In the example shown, it is possible to reduce the amplitude of chatter vibration to essentially 1/20. In the 5B In the example shown, it is possible to reduce the force of chatter vibration to essentially 1/10.

Moreover, the controller 140 according to the first embodiment determines a vibration vector as a value related to a deviation of the center of gravity from the central axis, but another embodiment of the present invention is not limited to this. For example, the controller 140 according to another embodiment may determine the position of the center of gravity with respect to the central axis as a value related to a deviation of the center of gravity and the central axis from each other.

The controller 140 according to the first embodiment performs feedback control such that the grinding wheel 131 is brought to a certain position by the feedback unit 417 at the time of balancing the grinding wheel, but is not limited thereto. For example, the controller 140 according to another embodiment does not need to output an actual command to the X-axis actuator 133 when balancing the grinding wheel.

Second embodiment

The control device 140 according to the first embodiment determines a vibration vector using a measured value of the displacement sensor 134. The control device 140 according to a second embodiment, on the other hand, determines a vibration vector based on a thrust force of the X-axis actuator 13.

The vibration detection unit 411 of the control device 140 according to the second embodiment further detects a current value from the X-axis actuator 133 in addition to the measurement values according to the first embodiment. The current value of the X-axis actuator 133 is proportional to the amount of thrust of the X-axis actuator 133. The eccentricity determination unit 418 calculates displacement of the X-axis actuator 133 from the current value of the X-axis actuator 133 and determines the vibration vector.

The following describes the reason why the vibration vector can be calculated based on the thrust of the X-axis actuator 133. When balancing the grinding wheel 131, the command output unit 415 of the controller 140 outputs an actual command so that the grinding wheel 131 is brought to a certain position. However, the grinding wheel 131 is displaced in the X-axis direction due to chatter vibration. When displacement occurs in the X-axis direction, the feedback unit 417 of the controller 140 generates a feedback signal to cancel the displacement. displacement and outputs the feedback signal to the command value calculation unit 414. Thereby, the X-axis actuator 133 applies the thrust force corresponding to the displacement in the X-axis direction due to chatter vibration through feedback control.

Function and effects

Thus, the control device 140 according to the second embodiment determines the vibration vector of the grinding wheel 131 based on the thrust of the X-axis actuator 133. The thrust of the X-axis actuator 133 is synchronized with the displacement in the X-axis direction due to the chatter vibration by feedback control as described above. Therefore, with the control device 140 according to the second embodiment, it is possible to determine the vibration vector of the grinding wheel 131 in the same manner as in the first embodiment.

Moreover, although the controller 140 according to the second embodiment determines the vibration vector of the grinding wheel 131 without using the measurement value of the displacement sensor 134, the present invention is not limited thereto. The controller 140 according to another embodiment may determine the vibration vector using the measurement value of the displacement sensor 134 and the thrust force of the X-axis actuator 133. For example, the controller 140 according to another embodiment may determine the vibration vector using an average value of the measurement value of the displacement sensor 134 and the displacement determined from the thrust force of the X-axis actuator 133.

Although an embodiment has been described above in detail with reference to the drawings, specific configurations are not limited to those described above, and various design changes and the like may be made.

For example, the control device 140 according to the embodiment described above controls the grinding machine 100, but the present invention is not limited thereto. For example, the control device 140 according to another embodiment may control an industrial machine in which a tool other than the grinding wheel 131 is used. Moreover, the shape of the grinding wheel 131 is not limited to the shape of a disk and may be a circular saw blade or a grindstone with a cylindrical shape. In another embodiment, an external measuring device may determine the eccentricity of the tool instead of the control device 140.

Industrial applications

According to the above-described disclosure of the present invention, the industrial machine determines the center of gravity of the tool based on the measured values of displacement from the displacement sensor. When the measured values of displacement are used, it is not necessary to perform multiple integration of the measured values, and thus it is possible to determine a value related to the eccentricity of the tool and not influenced by noise, unlike a case where an acceleration sensor is used.

Short description of reference symbols

100

Grinding machine

110

base

111

Y-axis guide section

112

Y-axis actuator

121

Headstock

122

Tailstock

123

rotating motor

120

Recording device

130

Grinding wheel carrier

131

Grinding wheel

132

X-axis guide section

133

X-axis actuator

134

Displacement sensor

135

rotating motor

136

Angle of rotation sensor

140

Control device

141

processor

143

Main memory

145

Storage

147

interface

150

Display device

410

Unit for detecting a rotation angle

411

Vibration detection unit

412

Unit for calculating a target position

413

Unit for calculating a target state variable

414

Unit for calculating a command value

415

Unit for issuing a command

416

Unit for a rotation command

417

Return unit

418

Unit for determining eccentricity

419

Unit for determining a correction weight

420

Unit for determining an amount of vibration

421

Display control unit

W

workpiece

Claims (6)

An industrial machine comprising: a tool (131); a rotating motor (123) configured to rotate the tool (131) about a central axis of the tool (131); a rotation angle sensor (136) configured to measure a rotation angle of the tool (131); and a control device (140) configured to control the rotating motor (123), the control device (140) including: a rotation command unit (416) configured to output a rotation command to the rotating motor (123); a rotation angle detection unit (410) configured to detect a measurement value of the rotation angle from the rotation angle sensor (136); characterized in that the industrial machine further comprises: an actuator (133) configured to move the tool (131) in a cutting direction; and a displacement sensor (134) designed to measure displacement of the tool (131) in the cutting direction; and the control device (140) is further designed to control the actuator (133), and includes: a vibration detection unit (411) designed to detect a measured value of the displacement from the displacement sensor (134) relating to a vibration of the tool (131) in the cutting direction; wherein the control device (140) is designed to repeat the detection of the measured values until time series of measured values relating to a predetermined period of time or a predetermined number of rotations have been detected, and an eccentricity determination unit (418) designed to detect a vibration vector relating to a deviation between a center of gravity of the tool (131) and the central axis based on the time series of measured values of the angle of rotation and the time series of measured values of the displacement. Industrial machine according to Claim 1 , wherein the control device (140) further includes: a command output unit (415) configured to output to the actuator (133) an actual command for positioning the tool (131) at a specific position based on a measured value of the displacement from the displacement sensor (134), and wherein the vibration detecting unit (411) is configured to detect a value relating to a thrust force of the actuator (133). Industrial machine according to Claim 1 or 2 , wherein the control device (140) further includes a correction weight setting unit (419) configured to set a position and a weight of a correction weight to be attached to the tool (131). An eccentricity determining device configured to determine a value related to the eccentricity of a tool (131) used to machine a workpiece (W) by moving the tool (131) in a cutting direction while rotating the tool (131) about a central axis by a rotary motor (123), the eccentricity determining device comprising: a rotation command output unit (416) configured to output a rotation command to the rotary motor (123); a rotation angle detecting unit (410) configured to detect a measured value of a rotation angle of the rotary motor (123); a vibration detecting unit (411) configured to detect a measured value of displacement from a displacement sensor (134) related to vibration of the tool (131) in the cutting direction; wherein the device for determining eccentricity is designed to repeat the acquisition of the measured values until time series of measured values relating to a predetermined period of time or a predetermined number of rotations have been acquired, and an eccentricity determination unit (418) designed to determine a vibration vector relating to a deviation between a center of gravity of the tool (131) and the center axis on the basis of the time series of measured values of the angle of rotation and the time series of measured values of the displacement. A method for determining eccentricity for determining a value relating to eccentricity of a tool (131) used to machine a workpiece (W) by moving the tool (131) in a cutting direction while rotating the tool (131) about a central axis by a rotary motor (123), the method for determining eccentricity comprising the steps of: issuing (S36) a rotation command to the rotary motor (123); detecting (S37) a measured value of a rotation angle of the rotary motor (123); detecting (S37) a measured value of displacement of the tool (131) in the cutting direction relating to a vibration of the tool (131) in the cutting direction; Repeating (S38, S39) the acquisition (S37) of the measured values until time series of measured values relating to a predetermined period of time or a predetermined number of rotations have been acquired, and determining (S40) a vibration vector relating to a deviation between a center of gravity of the tool (131) and the central axis based on the time series of measured values of the angle of rotation and the time series of measured values of the displacement. A program executed by a computer (140) and comprising the steps of: issuing (S36) a rotation command to a rotary motor (123) of an industrial machine (100) including a tool (131), the rotary motor (123) configured to rotate the tool (131) about a central axis of the tool (131) and including an actuator (133) configured to move the tool (131) in a cutting direction; acquiring (S37) a measured value of a rotation angle of the rotary motor (123); acquiring (S37) a measured value of displacement of the tool (131) in the cutting direction related to a vibration of the tool (131) in the cutting direction; Repeating (S38, S39) the acquisition (S37) of the measured values until time series of measured values relating to a predetermined period of time or a predetermined number of rotations have been acquired, and determining (S40) a vibration vector relating to a deviation between a center of gravity of the tool (131) and the central axis based on the time series of measured values of the angle of rotation and the time series of measured values of the displacement.

Images