JP5351550B2 - Machine tool and processing method - Google Patents

Abstract

A machine tool is equipped with an automatic speed feedback gain setter which calculates the speed feedback gain based on the moment of inertia of a work, a sensor which measures the sensor value relating to the rotation of a table supporting the work, and a controller performing feedback control of a motor based on the sensor value, the motor rotating the table based on the speed feedback gain so that the angle of the table coincides with a target angle. The moment of inertia of the table changes according to the moment of inertia of the work. A proper value is substituted in the speed feedback gain based on the moment of inertia of the work, and the machine tool ensures dynamic rigidity in the rotational direction of the table against an external force acting on the work and can prevent oscillation phenomenon.

Description

  The present invention relates to a machine tool and a machining method, and more particularly to a machine tool and a machining method used when machining a workpiece while rotating the workpiece.

  A machine tool that processes a workpiece while rotating the workpiece is known. Examples of such a machine tool include a 5-axis machine and a gear machine. Such a machine tool causes the rotation angle of the table to follow the target value by feedback control of a motor that rotates the table that supports the workpiece.

  FIG. 1 shows a known machine tool. The machine tool 101 includes a machine tool main body 102 and a machine tool control device 103. The machine tool main body 102 includes a table 105, a motor 107, a worm gear 108, and an encoder 109.

  The table 105 is supported by the base so as to be rotatable about a rotation axis parallel to the vertical direction. The table 105 has a support surface that is perpendicular to the rotation axis thereof, and supports the workpiece 110 that contacts the support surface. The motor 107 includes a shaft that is rotatably supported, and rotates the shaft based on an operation amount output from the machine tool control device 103. The worm gear 108 transmits the rotational power of the shaft of the motor 107 to the table 105 to rotate the table 105. The encoder 109 measures the rotational speed of the shaft of the motor 107 and outputs the rotational speed to the machine tool control device 103.

  The machine tool 101 further includes a tool (not shown). Examples of the tool include an end mill and a hob. The tool is controlled by an NC device (not shown) to process (for example, cut) the workpiece 110 to form a predetermined shape.

  The machine tool control device 103 includes a target value calculation unit 114, an integrator 115, and a control device 117. The target value calculation unit 114 collects NC data for machining the workpiece 110 and the operation of the tool, and calculates a target angle based on the NC data and the operation. The integrator 115 calculates the angle of the table 105 by integrating the rotational speed of the shaft of the motor 107 measured by the encoder 109.

  The control device 117 includes an angle difference calculation unit 121, an angle feedback gain multiplication unit 122, a rotation speed difference calculation unit 123, a speed feedback gain multiplication unit 124, a proportional control unit 125, an integration control unit 126, and an addition unit 127. .

  The angle difference calculation unit 121 calculates the angle difference by subtracting the angle of the table 105 calculated by the integrator 115 from the target angle calculated by the target value calculation unit 114. The angle feedback gain multiplication unit 122 multiplies the angle difference calculated by the angle difference calculation unit 121 by a constant angle feedback gain to calculate the rotation speed amount. The rotation speed difference calculation unit 123 calculates the rotation speed difference by subtracting the rotation speed of the shaft of the motor 107 measured by the encoder 109 from the rotation speed amount calculated by the angle feedback gain multiplication unit 122. The speed feedback gain multiplication unit 124 calculates a speed operation amount by multiplying the rotation speed difference calculated by the rotation speed difference calculation unit 123 by a constant speed feedback gain. The proportional control unit 125 calculates a proportional operation amount by multiplying the speed operation amount calculated by the speed feedback gain multiplication unit 124 by a constant proportional feedback gain. The integral control unit 126 calculates an integral control amount by integrating the speed operation amount calculated by the speed feedback gain multiplication unit 124, and multiplies the integral control amount by an integral feedback gain that is a constant, thereby integrating the integral operation amount. Is calculated. The adding unit 127 calculates an operation amount by multiplying the proportional operation amount calculated by the proportional control unit 125 by the integral operation amount calculated by the integration control unit 126.

  First, the operator places the workpiece 110 on the table 105 and inputs NC data for machining the workpiece 110 into an NC device (not shown). The NC device outputs the NC data to the machine tool control device 103, and drives the tool based on the NC data. The target value calculation unit 114 of the machine tool control device 103 calculates a target angle based on the NC data. The integrator 115 of the machine tool control device 103 calculates the angle of the table 105 based on the rotational speed of the shaft of the motor 107 measured by the encoder 109.

  The angle difference calculation unit 121 of the control device 117 calculates the angle difference by subtracting the angle of the table 105 calculated by the integrator 115 from the target angle calculated by the target value calculation unit 114. The angle feedback gain multiplication unit 122 multiplies the angle difference calculated by the angle difference calculation unit 121 by a constant angle feedback gain to calculate the rotation speed amount. The rotation speed difference calculation unit 123 calculates the rotation speed difference by subtracting the rotation speed of the shaft of the motor 107 measured by the encoder 109 from the rotation speed amount calculated by the angle feedback gain multiplication unit 122. The speed feedback gain multiplication unit 124 calculates a speed operation amount by multiplying the rotation speed difference calculated by the rotation speed difference calculation unit 123 by a constant speed feedback gain. The proportional control unit 125 calculates a proportional operation amount by multiplying the speed operation amount calculated by the speed feedback gain multiplication unit 124 by a constant proportional feedback gain. The integral control unit 126 calculates an integral control amount by integrating the speed operation amount calculated by the speed feedback gain multiplication unit 124, and multiplies the integral control amount by an integral feedback gain that is a constant, thereby integrating the integral operation amount. Is calculated. The adding unit 127 calculates an operation amount by multiplying the proportional operation amount calculated by the proportional control unit 125 by the integral operation amount calculated by the integration control unit 126.

  The motor 107 rotates the shaft based on the operation amount calculated by the adding unit 127. The worm gear 108 transmits the rotational power of the shaft of the motor 107 to the table 105 to rotate the table 105. With this operation, the machine tool 101 cuts the workpiece 110 by the tool as shown in the NC data, and forms the workpiece 110 into a predetermined shape.

  FIG. 2 shows another known machine tool. The machine tool 131 includes a machine tool main body 132 and a machine tool control device 133. The machine tool main body 132 includes a table 135, a direct drive motor (hereinafter referred to as “DD motor”) 137, and a rotary encoder 138.

  The table 135 is supported by the base so as to be rotatable about a rotation axis parallel to the vertical direction. The table 135 has a support surface that is perpendicular to the rotation axis thereof, and supports the work 139 that contacts the support surface. The work 139 is formed in a generally disc shape. The DD motor 137 includes a DD motor rotor 141 and a DD motor stator 142. The DD motor rotor 141 is fixed to the table 135. The DD motor stator 142 is fixed to the base. The DD motor 137 rotates the table 135 based on the operation amount output from the machine tool control device 133. The rotary encoder 138 measures the angle of the table 135 and outputs the angle to the machine tool control device 133.

  The machine tool 131 further includes a tool (not shown). Examples of the tool include an end mill and a hob. The tool is controlled by an NC device (not shown) to process (for example, cut) the workpiece 110 to form a predetermined shape.

  The machine tool control device 133 includes a target value calculation unit 114, a differentiator 145, and a control device 117. The target value calculation unit 114 collects NC data for machining the workpiece 139 and the operation of the tool, and calculates a target angle based on the NC data and the operation. The differentiator 145 calculates the rotational speed of the table 135 by differentiating the angle of the table 135 measured by the rotary encoder 138.

  The control device 117 includes an angle difference calculation unit 121, an angle feedback gain multiplication unit 122, a rotation speed difference calculation unit 123, a speed feedback gain multiplication unit 124, a proportional control unit 125, an integration control unit 126, and an addition unit 127. .

  The angle difference calculation unit 121 calculates the angle difference by subtracting the angle of the table 135 measured by the rotary encoder 138 from the target angle calculated by the target value calculation unit 114. The angle feedback gain multiplication unit 122 multiplies the angle difference calculated by the angle difference calculation unit 121 by a constant angle feedback gain to calculate the rotation speed amount. The rotation speed difference calculation unit 123 calculates the rotation speed difference by subtracting the rotation speed of the table 135 calculated by the differentiator 145 from the rotation speed amount calculated by the angle feedback gain multiplication unit 122. The speed feedback gain multiplication unit 124 calculates a speed operation amount by multiplying the rotation speed difference calculated by the rotation speed difference calculation unit 123 by a constant speed feedback gain. The proportional control unit 125 calculates a proportional operation amount by multiplying the speed operation amount calculated by the speed feedback gain multiplication unit 124 by a constant proportional feedback gain. The integral control unit 126 calculates an integral control amount by integrating the speed operation amount calculated by the speed feedback gain multiplication unit 124, and multiplies the integral control amount by an integral feedback gain that is a constant, thereby integrating the integral operation amount. Is calculated. The adding unit 127 calculates an operation amount by multiplying the proportional operation amount calculated by the proportional control unit 125 by the integral operation amount calculated by the integration control unit 126.

  The embodiment of the machining method according to the present invention is executed using a machine tool 131. First, the worker places the workpiece 139 on the table 135 and inputs NC data for machining the workpiece 139 into an NC device (not shown). The NC device outputs the NC data to the machine tool control device 133, and rotates the tool based on the NC data. The target value calculation unit 114 of the machine tool control device 133 calculates a target angle based on the NC data. The differentiator 145 of the machine tool control device 133 calculates the rotation speed of the table 135 based on the rotation angle of the table 135 measured by the rotary encoder 138.

  The angle difference calculation unit 121 of the control device 117 calculates the angle difference by subtracting the angle of the table 135 calculated by the differentiator 145 from the target angle calculated by the target value calculation unit 114. The angle feedback gain multiplication unit 122 multiplies the angle difference calculated by the angle difference calculation unit 121 by a constant angle feedback gain to calculate the rotation speed amount. The rotation speed difference calculation unit 123 calculates the rotation speed difference by subtracting the rotation speed of the table 135 calculated by the differentiator 145 from the rotation speed amount calculated by the angle feedback gain multiplication unit 122. The speed feedback gain multiplication unit 124 calculates a speed operation amount by multiplying the rotation speed difference calculated by the rotation speed difference calculation unit 123 by a constant speed feedback gain. The proportional control unit 125 calculates a proportional operation amount by multiplying the speed operation amount calculated by the speed feedback gain multiplication unit 124 by a constant proportional feedback gain. The integral control unit 126 calculates an integral control amount by integrating the speed operation amount calculated by the speed feedback gain multiplication unit 124, and multiplies the integral control amount by an integral feedback gain that is a constant, thereby integrating the integral operation amount. Is calculated. The adding unit 127 calculates an operation amount by multiplying the proportional operation amount calculated by the proportional control unit 125 by the integral operation amount calculated by the integration control unit 126.

  The DD motor 137 rotates the table 135 based on the operation amount calculated by the adding unit 127. With this operation, the machine tool 131 causes the tool to cut the edge of the workpiece 139 as shown in the NC data, thereby forming the workpiece 139 into a predetermined shape.

  Machine tools such as these can ensure dynamic rigidity in the table rotation direction by adjusting the constants of the feedback control system, for example, by increasing the gain of speed feedback. However, when the gain is set high, a vibration phenomenon caused by the control system occurs. For this reason, machine tools such as these set constants so that vibration phenomena caused by the control system do not occur when machining all target workpieces, and all control constants are fixed at the time of shipment. Yes. It is desired that a machine tool secures dynamic rigidity in the rotation direction of the table and prevents an oscillation phenomenon.

  Japanese Patent Laid-Open No. 2006-166591 discloses that even when a constant disturbance such as a gravitational disturbance is applied to the motor, an excessive change in torque is suppressed, thereby suppressing an overshoot of inertia ratio and suppressing oscillation of a servo control system Disclosed is a motor control device that can increase the convergence speed of identification and that does not degrade the identification result even if the sampling time used for inertia identification cannot be equal to the sampling time for speed control. Has been. The motor control device includes a command generation unit for generating a speed command Vref, a speed control unit for determining a torque command Tref based on the speed command Vref and the actual motor speed Vfb, and controlling the motor speed, and the speed control using a model. An estimation unit that simulates a unit and outputs an estimated torque command Tref ′, and identifies a total inertia value from a ratio between a time integral value of the torque command and a time integral value of the estimated torque command, and the speed control The unit is composed of proportional integral control, and the speed proportional gain is adjusted using the total inertia value in the motor control device, and means for dividing the total inertia value in one step past by the current total inertia value; Means for multiplying the result of the division by the integrator output value in the previous step of the proportional integral control, the multiplication result, and the speed Is characterized in that a means for adding the result of dividing by the integration time multiplied by the proportional integral control speed deviation obtained by subtracting the motor speed at the sampling time from the command.

JP 2006-166591 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a machine tool and a machining method for ensuring dynamic rigidity in the rotational direction of a table against an external force acting on a workpiece and preventing an oscillation phenomenon.

  In the following, means for solving the problems will be described using the reference numerals used in the modes and examples for carrying out the invention in parentheses. This symbol is added to clarify the correspondence between the description of the claims and the description of the modes and embodiments for carrying out the invention. Do not use to interpret the technical scope.

  The machine tool (1) (51) according to the present invention includes a speed feedback gain automatic setting device (16) (66) for calculating a speed feedback gain based on the moment of inertia of the work (10) (60), and the work (10). The speeds of the sensors (8) and (58) for measuring sensor values relating to the rotation of the tables (5) and (55) supporting (60) and the angles of the tables (5) and (55) so as to coincide with the target angle. And a control device (17) that feedback-controls the motor that rotates the tables (5) and (55) based on the sensor value based on the feedback gain. The moments of inertia of the tables (5) and (55) that support the workpieces (10) and (60) vary depending on the moment of inertia of the workpieces (10) and (60). In such a machine tool (1) (51), an appropriate value is substituted for the speed feedback gain based on the moment of inertia of the workpiece (10) (60), and the external force acting on the workpiece (10) (60) is applied. On the other hand, the dynamic rigidity in the rotational direction of the tables (5) and (55) can be secured, and the oscillation phenomenon can be prevented.

  The machine tool (1) (51) according to the present invention includes a load sensor (6) (56-1 to 56-5) for measuring a load applied from the workpiece (10) (60) to the table (5) (55). Is further provided. A speed feedback gain automatic setting device (16) (66) calculates a work inertia moment conversion unit (28) (67) for converting the inertia moment based on the load, and calculates the speed feedback gain based on the inertia moment. And a speed feedback gain calculation unit (29). Such a load sensor (6) (56-1 to 56-5) is preferable because the speed feedback gain can be automatically calculated.

  The load sensors (6) (56-1 to 56-5) are respectively arranged at a plurality of different positions on the support surface that supports the workpieces (10) and (60) of the tables (5) and (55). It is formed from a plurality of sensors (6) (56-1 to 56-5). According to such a plurality of sensors (6) (56-1 to 56-5), the table (based on the plurality of loads respectively measured by the plurality of sensors (6) (56-1 to 56-5) ( 5) The area in contact with the work (10) (60) in the support surface of (55) can be calculated, and the shape of the work (10) (60) can be estimated.

  The support surface is formed of a plurality of regions divided by a plurality of concentric circles around the rotation axis of the table (55). Each of the plurality of sensors (56-1 to 56-5) preferably measures a plurality of loads applied to the plurality of regions.

  The workpiece inertia moment conversion units (28) and (67) are configured to calculate workpieces (10) and (60) calculated based on a plurality of loads respectively measured by the plurality of sensors (6) (56-1 to 56-5). The moment of inertia is converted based on the shape and the mass of the workpiece (10) (60).

  The speed feedback gain automatic setting devices (16) (66) automatically update the speed feedback gain based on the moment of inertia while the tables (5) (55) are rotating.

  The velocity feedback gain is preferably simply increased with respect to the moment of inertia.

  The speed feedback gain automatic setting device includes a workpiece inertia moment conversion unit that calculates the inertia moment based on the workpiece shape and the workpiece density, and a speed feedback gain calculation unit that calculates the velocity feedback gain based on the inertia moment. And.

  The workpiece inertia moment conversion unit extracts the shape and the density from data for machining the workpiece.

  The machining method according to the present invention includes a step of calculating a speed feedback gain based on the moment of inertia of the workpieces (10) and (60), and a sensor relating to the rotation of the tables (5) and (55) that support the workpieces (10) and (60). Based on the sensor value, the step of measuring the value and the motor that rotates the table (5) (55) based on the speed feedback gain so that the angle of the table (5) (55) matches the target angle. Feedback control. The moments of inertia of the tables (5) and (55) that support the workpieces (10) and (60) vary depending on the moment of inertia of the workpieces (10) and (60). According to such a machining method, an appropriate value is substituted into the speed feedback gain based on the moment of inertia of the workpieces (10) and (60), and the table (for the external force acting on the workpieces (10) and (60)) 5) The dynamic rigidity in the rotational direction of (55) can be secured and the oscillation phenomenon can be prevented.

  The machining method according to the present invention further includes a step of measuring a load applied to the tables (5) and (55) from the workpieces (10) and (60), and a step of converting the moment of inertia based on the load. Yes.

  The machining method according to the present invention includes a step of measuring a plurality of loads respectively applied to a plurality of different positions on a support surface that supports the workpieces (10) and (60) of the tables (5) and (55), Calculating the shape of the workpiece (10) (60) and the mass of the workpiece (10) (60) based on a plurality of loads, and converting the moment of inertia based on the shape and the mass. It has more.

  The speed feedback gain is updated when the amount of change in the moment of inertia exceeds the threshold value before starting the processing in the tables (5) and (55).

  The velocity feedback gain simply increases with respect to the moment of inertia.

  The machining method according to the present invention further includes the step of calculating the moment of inertia based on the shape of the workpiece and the density of the workpiece, and the step of calculating the speed feedback gain based on the moment of inertia.

  The machining method according to the present invention further includes a step of extracting the shape and the density thereof from data for machining a workpiece.

  The machine tool and the machining method according to the present invention can set a speed feedback gain that is appropriate for the moment of inertia of the workpiece, and as a result, ensure the dynamic rigidity in the rotational direction of the table against the external force acting on the workpiece. In addition, the oscillation phenomenon can be prevented.

FIG. 1 is a block diagram showing a known machine tool. FIG. 2 is a block diagram showing another known machine tool. FIG. 3 is a block diagram showing an embodiment of a machine tool according to the present invention. FIG. 4 is a plan view showing a plurality of load cells. FIG. 5 is a diagram showing a data table. FIG. 6 is a graph showing changes in dynamic stiffness (compliance) when the table rotates when feedback control of the motor is performed using various speed feedback gains. FIG. 7 is a block diagram showing another embodiment of the machine tool according to the present invention. FIG. 8 is a plan view showing another plurality of load cells.

  An embodiment of a machine tool according to the present invention will be described with reference to the drawings. The machine tool 1 includes a machine tool body 2 and a machine tool control device 3 as shown in FIG. The machine tool body 2 includes a table 5, a plurality of load cells 6, a DD motor 7, and a rotary encoder 8.

  The table 5 is supported by a base so as to be rotatable about a rotation axis parallel to the vertical direction. The table 5 has a support surface that is perpendicular to the rotation axis thereof, and supports the workpiece 10 that contacts the support surface. The plurality of load cells 6 are respectively arranged at a plurality of different positions on the support surface and fixed to the table 5. In other words, the table 5 supports the workpiece 10 via the plurality of load cells 6. Each of the plurality of load cells 6 measures a load applied to the support surface from the workpiece 10 and outputs the load to the machine tool control device 3.

  The DD motor 7 includes a DD motor rotor 11 and a DD motor stator 12. The DD motor rotor 11 is fixed to the table 5. The DD motor stator 12 is fixed to the base. The DD motor 7 rotates the table 5 based on the operation amount output from the machine tool control device 3. The rotary encoder 8 measures the angle of the table 5 and outputs the angle to the machine tool control device 3.

  The machine tool 1 further includes a tool (not shown). Examples of the tool include an end mill and a hob. The tool is driven by an NC device (not shown) to process (cut) the workpiece 10 to form the workpiece 10 in a predetermined shape.

  The machine tool control device 3 includes a target value calculation unit 14, a differentiator 15, a speed feedback gain automatic setting device 16, and a control device 17. The target value calculation unit 14 calculates a target angle based on NC data for machining the workpiece 10. The differentiator 15 calculates the rotational speed of the table 5 by differentiating the angle of the table 5 measured by the rotary encoder 8.

  The speed feedback gain automatic setting device 16 updates the speed feedback gain based on a plurality of loads respectively measured by the plurality of load cells 6. That is, the speed feedback gain automatic setting device 16 includes a workpiece inertia moment conversion unit 28 and a speed feedback gain calculation unit 29. The workpiece inertia moment conversion unit 28 calculates the moment of inertia of the workpiece 10 based on a plurality of loads respectively measured by the plurality of load cells 6. The speed feedback gain calculation unit 29 includes a storage device that records a data table that associates the moment of inertia with the speed feedback gain. The speed feedback gain calculation unit 29 refers to the data table and calculates a speed feedback gain based on the inertia moment calculated by the workpiece inertia moment conversion unit 28.

  The control device 17 uses the target angle calculated by the target value calculation unit 14, the rotational speed of the table 5 calculated by the differentiator 15, the angle of the table 5 measured by the rotary encoder 8, and the speed feedback gain automatic setting device 16. Based on the set speed feedback gain, the DD motor 7 is feedback-controlled so that the angle of the table 5 matches the target angle calculated by the target value calculator 14. That is, the control device 17 includes an angle difference calculation unit 21, an angle feedback gain multiplication unit 22, a rotation speed difference calculation unit 23, a speed feedback gain multiplication unit 24, a proportional control unit 25, an integration control unit 26, and an addition unit 27. ing.

  The angle difference calculation unit 21 calculates the angle difference by subtracting the angle of the table 5 measured by the rotary encoder 8 from the target angle calculated by the target value calculation unit 14. The angle feedback gain multiplication unit 22 calculates the rotation speed amount by multiplying the angle difference calculated by the angle difference calculation unit 21 by an angle feedback gain that is a constant. The rotation speed difference calculation unit 23 calculates the rotation speed difference by subtracting the rotation speed of the table 5 calculated by the differentiator 15 from the rotation speed amount calculated by the angle feedback gain multiplication unit 22. The speed feedback gain multiplication unit 24 calculates the speed operation amount by multiplying the rotation speed difference calculated by the rotation speed difference calculation unit 23 by the speed feedback gain calculated by the speed feedback gain calculation unit 29. The proportional control unit 25 calculates a proportional operation amount by multiplying the speed operation amount calculated by the speed feedback gain multiplication unit 24 by a constant proportional feedback gain. The integration control unit 26 calculates an integral control amount by integrating the speed operation amount calculated by the speed feedback gain multiplication unit 24, and multiplies the integral control amount by an integral feedback gain that is a constant, thereby integrating the operation amount. Is calculated. The adding unit 27 calculates the operation amount by multiplying the proportional operation amount calculated by the proportional control unit 25 by the integral operation amount calculated by the integration control unit 26.

  FIG. 4 shows a plurality of load cells 6. The plurality of load cells 6 are arranged in a grid of a plurality of rows and a plurality of columns on the support surface of the table 5, and are fixed to the table 5. The plurality of columns are formed from a first column to a seventh column. The plurality of rows are formed from the first row to the seventh row. Each of the plurality of load cells 6 belongs to one column of the plurality of columns and belongs to one row of the plurality of rows. Two or more load cells belonging to one of the plurality of columns and belonging to one of the plurality of rows are not included in the plurality of load cells 6.

At this time, the workpiece inertia moment conversion unit 28 calculates the mass M of the workpiece 10 by calculating the sum of a plurality of loads respectively measured by the plurality of load cells 6. The work moment of inertia conversion unit 28 records the threshold value in the storage device, and the work 10 comes into contact with the support surface of the table 5 based on the position of the load cell that has measured a load larger than the threshold value among the plurality of load cells 6. Estimate the shape of the area. The workpiece moment of inertia conversion unit 28 calculates the moment of inertia I of the workpiece 10 as follows when a rectangle is estimated as its shape:
^{I = M × (a 2/} 12 + b 2/12)
Calculated by Here, a indicates the horizontal length of the rectangle. b indicates the vertical length of the rectangle.

  FIG. 5 shows a data table recorded by the speed feedback gain calculation unit 29. The data table 31 associates the work inertia moment set 32 with the speed feedback set 33. That is, an arbitrary element of the work moment of inertia set 32 corresponds to one element of the speed feedback set 33. Each element of the work inertia moment set 32 indicates a moment of inertia that can be calculated by the work inertia moment conversion unit 28. Each element of the speed feedback set 33 indicates a value of a speed feedback gain that can be used by the control device 17. The data table 31 indicates that the speed feedback gain value that is optimal when the table 5 supports the workpiece 10 having a certain moment of inertia corresponds to the moment of inertia, and the speed feedback gain simply increases with respect to the moment of inertia. To be formed.

  At this time, the speed feedback gain calculation unit 29 refers to the data table 31 and calculates a speed feedback gain corresponding to the inertia moment calculated by the workpiece inertia moment conversion unit 28 from the speed feedback gain set.

  The embodiment of the machining method according to the present invention is executed using the machine tool 1. First, the operator places the workpiece 10 on the table 5 and inputs NC data for machining the workpiece 10 into an NC device (not shown). The NC device outputs the NC data to the machine tool control device 3, and drives the tool based on the NC data. The target value calculation unit 14 of the machine tool control device 3 collects the NC data and the operation of the tool, and calculates a target angle based on the NC data and the operation. The differentiator 15 of the machine tool control device 3 calculates the rotation speed of the table 5 based on the rotation angle of the table 5 measured by the rotary encoder 8.

  The workpiece inertia moment conversion unit 28 of the speed feedback gain automatic setting device 16 calculates the inertia moment of the workpiece 10 based on a plurality of loads respectively measured by the plurality of load cells 6. The speed feedback gain calculation unit 29 refers to the data table 31 and calculates a speed feedback gain corresponding to the inertia moment calculated by the workpiece inertia moment conversion unit 28 from the speed feedback gain set. Such calculation of the speed feedback gain is periodically and intermittently executed.

  The angle difference calculation unit 21 of the control device 17 calculates the angle difference by subtracting the angle of the table 5 calculated by the differentiator 15 from the target angle calculated by the target value calculation unit 14. The angle feedback gain multiplication unit 22 calculates the rotation speed amount by multiplying the angle difference calculated by the angle difference calculation unit 21 by an angle feedback gain that is a constant. The rotation speed difference calculation unit 23 calculates the rotation speed difference by subtracting the rotation speed of the table 5 calculated by the differentiator 15 from the rotation speed amount calculated by the angle feedback gain multiplication unit 22. The speed feedback gain multiplication unit 24 calculates the speed operation amount by multiplying the rotation speed difference calculated by the rotation speed difference calculation unit 23 by the speed feedback gain set by the speed feedback gain automatic setting device 16. The proportional control unit 25 calculates a proportional operation amount by multiplying the speed operation amount calculated by the speed feedback gain multiplication unit 24 by a constant proportional feedback gain. The integration control unit 26 calculates an integral control amount by integrating the speed operation amount calculated by the speed feedback gain multiplication unit 24, and multiplies the integral control amount by an integral feedback gain that is a constant, thereby integrating the operation amount. Is calculated. The adding unit 27 calculates the operation amount by multiplying the proportional operation amount calculated by the proportional control unit 25 by the integral operation amount calculated by the integration control unit 26.

  The DD motor 7 rotates the table 5 based on the operation amount calculated by the adding unit 27. With this operation, the machine tool 1 forms the workpiece 10 by the tool cutting the edge of the workpiece 10 and forming teeth on the edge of the workpiece 10 as shown in the NC data.

  FIG. 6 shows a change in dynamic rigidity (compliance) when the table 5 rotates when feedback control of the DD motor 7 is performed using a plurality of speed feedback gains. The change 41 indicates the dynamic rigidity related to the rotation of the table 5 when the DD motor 7 is feedback-controlled using a speed feedback gain indicating a certain value. The change 42 indicates the dynamic rigidity related to the rotation of the table 5 when the DD motor 7 is feedback-controlled using a speed feedback gain larger than the speed feedback gain when the dynamic rigidity of the change 41 is indicated. The change 43 indicates the dynamic rigidity related to the rotation of the table 5 when the DD motor 7 is feedback-controlled using a speed feedback gain larger than the speed feedback gain when the dynamic rigidity of the change 42 is indicated. The change 44 indicates the dynamic rigidity related to the rotation of the table 5 when the DD motor 7 is feedback-controlled using a speed feedback gain larger than the speed feedback gain when the dynamic rigidity of the change 43 is indicated. The change 45 indicates the dynamic rigidity related to the rotation of the table 5 when the DD motor 7 is feedback-controlled using a speed feedback gain larger than the speed feedback gain when the dynamic rigidity of the change 44 is indicated.

  The changes 41 to 45 indicate that the velocity feedback gain used for the feedback control changes with respect to the disturbance frequency when the value is a certain value. Changes 41 to 45 further indicate that the dynamic rigidity when the table 5 rotates when the speed feedback gain is increased, and that the rotation of the table 5 is less affected by disturbance. Yes.

  The mass of the workpiece 10 is reduced by machining, and the moment of inertia of the workpiece 10 is changed by the reduction of the mass. The machine tool 1 updates the speed feedback gain based on the moment of inertia of the workpiece 10 during machining of the workpiece 10, thereby reducing problems caused by changes in the moment of inertia of the workpiece 10 during machining. . An example of the insufficiency is a vibration phenomenon caused by the control system, which occurs because the speed feedback gain is set high with respect to the moment of inertia of the workpiece 10. For this reason, the machine tool 1 can ensure the dynamic rigidity in the rotation direction of the table 5 with respect to the external force acting on the workpiece 10, and can prevent the oscillation phenomenon caused by the control system.

  FIG. 7 shows another embodiment of the machine tool according to the present invention. The machine tool 51 includes a machine tool main body 52 and a machine tool control device 53. The machine tool main body 52 includes a table 55, a DD motor 57, and a rotary encoder 58.

  The table 55 is supported by the base so as to be rotatable about a rotation axis parallel to the vertical direction. The table 55 has a support surface that is perpendicular to the rotation axis thereof, and supports the workpiece 60 that contacts the support surface. The workpiece 60 is formed in a three-dimensional shape that is generally rotationally symmetric. The solid axis is arranged on the table 55 so that the rotation axis of the table 55 coincides. The plurality of load cells 56-1 to 56-5 are respectively arranged at a plurality of different positions on the support surface and fixed to the table 55. That is, the table 55 supports the workpiece 60 via the plurality of load cells 56-1 to 56-5. Each of the plurality of load cells 56-1 to 56-5 measures a load applied to the support surface from the workpiece 60 and outputs the load to the machine tool control device 53.

  The DD motor 57 includes a DD motor rotor 61 and a DD motor stator 62. The DD motor rotor 61 is fixed to the table 55. The DD motor stator 62 is fixed to the base. The DD motor 57 rotates the table 55 based on the operation amount output from the machine tool control device 53. The rotary encoder 58 measures the angle of the table 55 and outputs the angle to the machine tool control device 53.

  The machine tool 51 further includes a tool (not shown). Examples of the tool include an end mill and a hob. The tool is driven by an NC device (not shown) to process (cut) the workpiece 60 to form the workpiece 60 in a predetermined shape.

  The machine tool control device 53 includes a target value calculation unit 14, a differentiator 65, a speed feedback gain automatic setting device 66, and a control device 17. The target value calculation unit 14 calculates a target angle based on NC data for machining the workpiece 60. The differentiator 65 calculates the rotational speed of the table 55 by differentiating the angle of the table 55 measured by the rotary encoder 58.

  The speed feedback gain automatic setting device 66 updates the speed feedback gain based on a plurality of loads respectively measured by the plurality of load cells 56-1 to 56-5. That is, the speed feedback gain automatic setting device 66 includes a workpiece inertia moment conversion unit 67 and a speed feedback gain calculation unit 29. The workpiece inertia moment conversion unit 67 calculates the inertia moment of the workpiece 60 based on a plurality of loads respectively measured by the plurality of load cells 56-1 to 56-5. The speed feedback gain calculation unit 29 records the data table 31 in the above-described embodiment in a storage device, and refers to the data table 31 to speed feedback based on the inertia moment calculated by the work inertia moment conversion unit 67. Calculate the gain.

  The control device 17 uses the target angle calculated by the target value calculation unit 14, the rotational speed of the table 55 calculated by the differentiator 65, the angle of the table 55 measured by the rotary encoder 58, and the speed feedback gain automatic setting device 66. Based on the set speed feedback gain, the motor 57 is feedback-controlled so that the angle of the table 55 matches the target angle calculated by the target value calculation unit 14. That is, the control device 17 includes an angle difference calculation unit 21, an angle feedback gain multiplication unit 22, a rotation speed difference calculation unit 23, a speed feedback gain multiplication unit 24, a proportional control unit 25, an integration control unit 26, and an addition unit 27. ing.

  The angle difference calculation unit 21 calculates the angle difference by subtracting the angle of the table 55 measured by the rotary encoder 58 from the target angle calculated by the target value calculation unit 14. The angle feedback gain multiplication unit 22 calculates the rotation speed amount by multiplying the angle difference calculated by the angle difference calculation unit 21 by an angle feedback gain that is a constant. The rotation speed difference calculation unit 23 calculates the rotation speed difference by subtracting the rotation speed of the table 55 calculated by the differentiator 65 from the rotation speed amount calculated by the angle feedback gain multiplication unit 22. The speed feedback gain multiplication unit 24 calculates the speed operation amount by multiplying the rotation speed difference calculated by the rotation speed difference calculation unit 23 by the speed feedback gain calculated by the speed feedback gain calculation unit 29. The proportional control unit 25 calculates a proportional operation amount by multiplying the speed operation amount calculated by the speed feedback gain multiplication unit 24 by a constant proportional feedback gain. The integration control unit 26 calculates an integral control amount by integrating the speed operation amount calculated by the speed feedback gain multiplication unit 24, and multiplies the integral control amount by an integral feedback gain that is a constant, thereby integrating the operation amount. Is calculated. The adding unit 27 calculates the operation amount by multiplying the proportional operation amount calculated by the proportional control unit 25 by the integral operation amount calculated by the integration control unit 26.

  FIG. 8 shows a plurality of load cells 56-1 to 56-5. The plurality of load cells 56-1 to 56-5 are each formed in a ring shape. The support surface of the table 55 is divided into a plurality of regions by a plurality of concentric circles around the rotation axis of the table 55. The plurality of load cells 56-1 to 56-5 are arranged so as to measure a plurality of loads respectively applied to the plurality of regions. That is, the load cell 56-1 is disposed on the support surface of the table 55 so as to surround the rotation axis of the table 55. The load cell 56-2 is disposed on the support surface of the table 55 so as to surround the load cell 56-1. The load cell 56-3 is disposed on the support surface of the table 55 so as to surround the load cell 56-2. The load cell 56-4 is disposed on the support surface of the table 55 so as to surround the load cell 56-3. The load cell 56-5 is disposed on the support surface of the table 55 so as to surround the load cell 56-4.

At this time, the workpiece inertia moment conversion unit 67 calculates the mass M of the workpiece 60 by calculating the sum of a plurality of loads respectively measured by the plurality of load cells 56-1 to 56-5. The workpiece inertia moment conversion unit 67 further records a threshold value in a storage device, and based on the diameter of the ring of the load cell that has measured a load larger than the threshold value among the plurality of load cells 56-1 to 56-5. The radius r is estimated. The workpiece inertia moment conversion unit 67 further calculates the inertia moment I of the workpiece 60 by the following formula:
I = M × r ²
Calculated by

  The embodiment of the machining method according to the present invention is executed using a machine tool 51. First, the operator places the workpiece 60 on the table 55 and inputs NC data for machining the workpiece 60 into an NC device (not shown). The NC device outputs the NC data to the machine tool control device 53, and drives the tool based on the NC data. The target value calculation unit 14 of the machine tool control device 53 calculates a target angle based on the NC data. The differentiator 65 of the machine tool control device 53 calculates the rotation speed of the table 55 based on the rotation angle of the table 55 measured by the rotary encoder 58.

  The workpiece inertia moment conversion unit 67 of the speed feedback gain automatic setting device 66 calculates the inertia moment of the workpiece 60 based on a plurality of loads respectively measured by the plurality of load cells 56-1 to 56-5. The speed feedback gain calculation unit 29 refers to the data table 31 and calculates a speed feedback gain corresponding to the inertia moment calculated by the workpiece inertia moment conversion unit 67 from the speed feedback gain set. Such calculation of the speed feedback gain is periodically and intermittently executed.

  The angle difference calculation unit 21 of the control device 17 calculates the angle difference by subtracting the angle of the table 55 calculated by the differentiator 65 from the target angle calculated by the target value calculation unit 14. The angle feedback gain multiplication unit 22 calculates the rotation speed amount by multiplying the angle difference calculated by the angle difference calculation unit 21 by an angle feedback gain that is a constant. The rotation speed difference calculation unit 23 calculates the rotation speed difference by subtracting the rotation speed of the table 55 calculated by the differentiator 65 from the rotation speed amount calculated by the angle feedback gain multiplication unit 22. The speed feedback gain multiplication unit 24 calculates the speed operation amount by multiplying the rotation speed difference calculated by the rotation speed difference calculation unit 23 by the speed feedback gain set by the speed feedback gain automatic setting device 66. The proportional control unit 25 calculates a proportional operation amount by multiplying the speed operation amount calculated by the speed feedback gain multiplication unit 24 by a constant proportional feedback gain. The integration control unit 26 calculates an integral control amount by integrating the speed operation amount calculated by the speed feedback gain multiplication unit 24, and multiplies the integral control amount by an integral feedback gain that is a constant, thereby integrating the operation amount. Is calculated. The adding unit 27 calculates the operation amount by multiplying the proportional operation amount calculated by the proportional control unit 25 by the integral operation amount calculated by the integration control unit 26.

  The DD motor 57 rotates the table 55 based on the operation amount calculated by the adding unit 27. With this operation, the machine tool 51 forms the workpiece 60 by cutting the edge of the workpiece 60 and forming teeth on the edge of the workpiece 60 as shown in the NC data.

  The machine tool 51 can reduce problems caused by a change in the moment of inertia of the workpiece 60 during machining, in the same manner as the machine tool 1 in the above-described embodiment. As a result, the machine tool 51 acts on the workpiece 60. Thus, the dynamic rigidity in the rotation direction of the table 55 with respect to the external force can be ensured, and the oscillation phenomenon caused by the control system can be prevented. Further, the machine tool 51 has a lower machining accuracy than the machine tool 1 with respect to a workpiece having a shape that is not rotationally symmetric with respect to the rotation axis of the table 55, but the number of load cells is small and the machine tool 51 is manufactured at a lower cost. Can do. That is, the machine tool 51 is suitable for machining a workpiece that is rotationally symmetric.

  The workpiece moment of inertia conversion unit 28 can be replaced with another workpiece inertia moment conversion unit that calculates the moment of inertia of the workpiece 10 based on information different from the load measured by the load cell 6. For example, the workpiece inertia moment conversion unit collects the shape and density of the workpiece inputted from the input device provided in the speed feedback gain automatic setting device from the input device. The moment of inertia of the workpiece is calculated based on the shape and density of the workpiece.

  A machine tool having such a workpiece moment of inertia conversion unit employs a speed feedback gain that is appropriate for the workpiece moment of inertia, so that the dynamic rigidity in the rotational direction of the table 5 against an external force acting on the workpiece is adopted. Can be ensured, and an oscillation phenomenon caused by the control system can be prevented. Such a machine tool does not need to have a load cell and can be manufactured at a lower cost.

  Further, the workpiece moment of inertia conversion unit 28 collects CAD data created when the workpiece is designed and analyzes the CAD data to calculate the moment of inertia of the workpiece. It can also be replaced. According to such a workpiece moment of inertia conversion unit, the user can save time and effort to update the speed feedback gain more easily.

  It should be noted that the DD motor applied to the machine tool in the above-described embodiment can be replaced with another motor that rotates the table via a gear. In the same way as in the above-described embodiment, such a machine tool can reduce problems caused by a change in the moment of inertia of the workpiece during machining, and the rotation direction of the table with respect to an external force acting on the workpiece. Can be ensured, and an oscillation phenomenon caused by the control system can be prevented.

1: Machine tool 2: Machine tool body 3: Machine tool control device 5: Table 6: Load cell 7: DD motor 8: Rotary encoder 10: Workpiece 11: DD motor rotor 12: DD motor stator 14: Target value calculation unit 15: Differential Device 16: Speed feedback gain automatic setting device 17: Control device 21: Angle difference calculation unit 22: Angle feedback gain multiplication unit 23: Rotational speed difference calculation unit 24: Speed feedback gain multiplication unit 25: Proportional control unit 26: Integration control unit 27: Addition unit 28: Work inertia moment conversion unit 29: Speed feedback gain calculation unit 31: Data table 32: Work inertia moment set 33: Speed feedback set 41: Change 42: Change 43: Change 44: Change 45: Change 51: Machine tool 52: Machine tool Body 53: Machine tool controller 55: Tables 56-1 to 56-5: Multiple load cells 57: Motor 58: Rotary encoder 60: Workpiece 61: DD motor rotor 62: DD motor stator 65: Differentiator 66: Automatic speed feedback gain Setting device 67: Work inertia moment conversion section

Claims (7)

A speed feedback gain automatic setting device that calculates a speed feedback gain based on the moment of inertia of the workpiece;
A sensor for measuring a sensor value related to rotation of a table supporting the workpiece;
A control device that feedback-controls a motor that rotates the table based on the sensor value based on the speed feedback gain so that the angle of the table matches a target angle ;
A load sensor for measuring a load applied from the workpiece to the table ;
The load sensor is formed of a plurality of sensors respectively arranged at a plurality of different positions on a support surface that supports the workpiece of the table,
The speed feedback gain automatic setting device converts the moment of inertia based on the shape of the workpiece and the mass of the workpiece calculated based on a plurality of loads respectively measured by the plurality of sensors. <br/> machine tool comprising a part. In claim 1 ,
The support surface is formed from a plurality of regions divided by a plurality of concentric circles around the rotation axis of the table,
The plurality of sensors respectively measure a plurality of loads applied to the plurality of regions. In either claim 1 or claim 2 ,
The speed feedback gain automatic setting device automatically updates the speed feedback gain based on the moment of inertia while the table is rotating. In any one of Claims 1-3 ,
The speed feedback gain simply increases with respect to the moment of inertia machine tool. Calculating a speed feedback gain based on the moment of inertia of the workpiece;
Measuring a sensor value relating to rotation of a table supporting the workpiece;
Feedback control of a motor for rotating the table based on the sensor value based on the speed feedback gain so that the angle of the table matches a target angle.
Measuring a plurality of loads applied respectively to a plurality of different positions on a support surface supporting the workpiece of the table;
Calculating the shape of the workpiece and the mass of the workpiece based on the plurality of loads;
A processing method comprising: converting the moment of inertia based on the shape and the mass . In claim 5 ,
The speed feedback gain is updated while the table is rotating. In either claim 5 or claim 6 ,
The speed feedback gain is simply increased with respect to the moment of inertia.

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