JP2018169666A - Numerical control device and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a numerical control device capable of effectively utilizing output torque of a servomotor, and a control method thereof.SOLUTION: A numerical control device performs specific acceleration deceleration control for a feeding shaft driven by a motor. The specific acceleration deceleration control includes an acceleration increase period T1, a first constant acceleration period T2, and an acceleration decrease period T6. A time constant t1 of the acceleration increase period T1 is smaller than a time constant t2 of the acceleration decrease period T6. Accordingly, the numerical control device can effectively utilize the maximum output torque of the motor at lower rotation speed side. The specific acceleration deceleration control includes a second constant acceleration period T2 during the acceleration decrease period T6 except the start and end of the acceleration decrease period T6. Accordingly, since the numerical control device can decrease the output torque in a step by step manner during the acceleration decrease period T6, the numerical control device can approximate the output torque so as not to exceed the maximum output torque in a higher rotation speed area where the decrease tendency of the acceleration is not constant. Consequently, the numerical control device can effectively utilize the output torque of the motor.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a numerical control device and a control method.

  The machine tool includes a motor and a feed shaft. The feed shaft is driven by a motor. The numerical control device performs acceleration / deceleration control of the feed shaft. The acceleration and the motor torque are in a proportional relationship. The motor has a maximum output torque characteristic based on the rating. The numerical control device desirably controls the output torque of the motor within the range of the maximum output torque characteristic. The numerical control device described in Patent Document 1 includes acceleration / deceleration control means. The acceleration / deceleration control means performs two-stage acceleration / deceleration control of the feed shaft by approximating the maximum output torque characteristic of the motor in order to make maximum use of the output torque of the motor. In the maximum output torque characteristic M1 of the motor shown in FIG. 7, the maximum output torque of the motor linearly decreases with a constant gradient from the rotational speed R1. The acceleration / deceleration control means performs two-stage acceleration / deceleration control of the feed shaft so that the output torque characteristic Q1 of the motor falls within the range of the maximum output torque characteristic M1.

  The output torque characteristic Q1 of the motor in the two-stage acceleration / deceleration control includes an acceleration increase period T1 at the beginning of acceleration, a first acceleration constant period T2 at which acceleration is constant, a first acceleration decrease period T3 at which acceleration decreases at the end of acceleration, and acceleration. A second acceleration decrease period T4 before the end is provided. The inclination of the acceleration change in the acceleration increase period T1 is set larger than the inclination of the acceleration change in the first and second acceleration decrease periods T3 and T4. The first acceleration decrease rate in the first acceleration decrease period T3 has a constant first slope. The second acceleration decrease rate in the second acceleration decrease period T4 has a constant second gradient larger than the first gradient. Therefore, the output torque characteristic Q1 can be in the region of the maximum output torque characteristic M1.

Japanese Patent No. 5233593

  The maximum output torque characteristic M2 of the motor shown in FIG. 8 becomes gentler in the region where the maximum output torque of the motor decreases in the region on the high rotation speed side from the rotation speed R1 as the rotation speed increases. In the output torque characteristic Q1 of the motor, a portion exceeding the maximum output occurs in the region on the high rotation speed side from the rotation speed R1. Therefore, since the acceleration / deceleration control means needs to reduce the output torque on the low rotational speed side (see the dotted line in FIG. 8), there is a problem that the output torque of the motor cannot be effectively used.

  An object of the present invention is to provide a numerical control device and a control method capable of effectively using an output torque of a servo motor.

  The numerical control apparatus according to claim 1 controls a machine including a servomotor and a drive shaft driven by the servomotor, an acceleration increase period in which acceleration is increased at the start of acceleration of the drive shaft, In a numerical control device comprising a control unit that executes acceleration / deceleration control having a first acceleration constant period for making acceleration constant at the end of acceleration, and an acceleration decrease period for reducing acceleration after the first acceleration constant period, The control unit reduces the time constant of the acceleration increase speed during the acceleration increase period to be smaller than the time constant of the acceleration decrease speed during the acceleration decrease period, and includes a portion of the acceleration decrease period excluding the start time and the end time of the acceleration decrease period. The second acceleration constant period is provided to keep the constant. The control unit makes the time constant of the acceleration increasing speed during the acceleration increasing period smaller than the time constant of the acceleration decreasing period. Therefore, the numerical controller can effectively use the maximum output torque on the low-speed rotation side of the servo motor. The control unit provides a second constant acceleration period in portions other than the start and end of the acceleration decrease period. Therefore, since the numerical control device can reduce the acceleration stepwise, the output torque can be approximated so as not to exceed the maximum output torque on the high speed rotation speed side. Therefore, the numerical control device can effectively use the output torque of the servo motor. The portions excluding the start and end of the acceleration decrease period are the period of the acceleration decrease rate with the constant inclination provided at the start of the acceleration decrease period and the acceleration decrease rate with the constant inclination provided at the end of the acceleration decrease period. It means the part sandwiched between periods. That is, the second constant acceleration period does not start from the start of the acceleration decrease period, and the second constant acceleration period does not end at the end of the acceleration decrease period. One or more second acceleration constant periods may be provided in portions other than the start and end of the acceleration decrease period.

  The control unit of the numerical control device according to claim 2, wherein a slope of a predetermined portion where the maximum output torque is reduced among the maximum output torque characteristics that are the maximum output torque corresponding to the rotation speed of the servo motor is the rotation speed. In the acceleration / deceleration control of the drive shaft, the second acceleration constant period is provided in a portion excluding the start and end of the acceleration decrease period corresponding to the predetermined portion. The output torque of the servomotor proportional to the acceleration with respect to time may be controlled so as not to exceed the maximum output torque in the acceleration increase period, the first acceleration constant period, and the acceleration decrease period. For servo motors with the maximum output torque characteristic that the slope of the predetermined part where the maximum output torque decreases becomes smaller as the number of revolutions increases, the time constant of the acceleration increase speed during the acceleration increase period is set as the acceleration decrease during the acceleration decrease period. If the speed is smaller than the time constant, the output torque of the servo motor may exceed the maximum output torque at a predetermined portion of the maximum output torque characteristic. The present invention can prevent the output torque from exceeding the maximum output torque on the high rotation speed side by providing the second acceleration constant period in the portion excluding the start and end of the acceleration reduction period corresponding to the predetermined portion. Therefore, the numerical controller can effectively use the output torque on the low rotation speed side of the servo motor.

  According to a third aspect of the present invention, there is provided a control method for controlling a machine including a servo motor and a drive shaft driven by the servo motor, an acceleration increasing period during which acceleration is increased at the start of acceleration of the drive shaft, and acceleration of the drive shaft. In a control method of a numerical control device that performs a control step of performing acceleration / deceleration control having a first acceleration constant period that makes acceleration constant at the end, and an acceleration decrease period that decreases acceleration after the first acceleration constant period, In the control step, the time constant of the acceleration increase speed in the acceleration increase period is made smaller than the time constant of the acceleration decrease speed in the acceleration decrease period, and at the part excluding the start time and end time of the acceleration decrease period, A second acceleration constant period for making the acceleration constant is provided. Therefore, the numerical control device can obtain the effect of the first aspect by performing the control step.

  The numerical control device of the present invention controls a machine including a servo motor and a drive shaft driven by the servo motor, and increases an acceleration period during which acceleration is increased at the start of acceleration of the drive shaft, and acceleration of the drive shaft. In the numerical control device comprising a control unit that executes acceleration / deceleration control having a first acceleration constant period in which acceleration is constant at the end and an acceleration decrease period in which acceleration is decreased after the first acceleration constant period, the control The unit may provide a second acceleration constant period in which the acceleration is constant in a portion other than the start time and the end time of the acceleration decrease period.

1 is a block diagram showing an electrical configuration of a numerical control device 20 and a machine tool 10. FIG. The chart which shows the maximum output torque characteristic M2 of a servomotor, and the output torque characteristic Q2 by specific acceleration / deceleration control. The chart which shows the acceleration pattern and speed pattern by specific acceleration / deceleration control of an X-axis motor. The flowchart of a speed calculation process. FIG. 5 is a flowchart showing a continuation of FIG. 4. The chart which shows the maximum output torque characteristic M3 and output torque characteristic Q3 (modification) of an X-axis motor. The chart which shows the maximum output torque characteristic M1 of a servomotor, and the output torque characteristic Q1 by the conventional two-stage acceleration / deceleration control. The chart which shows the maximum output torque characteristic M2 of a servomotor, and the output torque characteristic Q1 by the conventional two-stage acceleration / deceleration control.

  Embodiments of the present invention will be described below. The numerical control device 20 shown in FIG. 1 performs cutting of a work material (not shown) held on the upper surface of a table (not shown) by controlling the axial movement of the machine tool 10. The left-right direction, the front-rear direction, and the up-down direction of the machine tool 10 are an X-axis direction, a Y-axis direction, and a Z-axis direction, respectively.

  The configuration of the machine tool 10 will be described with reference to FIG. For example, the machine tool 10 moves a tool mounted on a spindle extending in the Z-axis direction in the X-axis direction, the Y-axis direction, and the Z-axis direction with respect to the work material held on the table upper surface (for example, drilling, tapping) It is a vertical machine tool that performs machining, side machining, turning, etc.). The machine tool 10 includes a spindle mechanism, a spindle moving mechanism, a tool changer, and the like (not shown). The spindle mechanism includes a spindle motor 12 and rotates a spindle on which a tool is mounted. The spindle moving mechanism further includes a Z-axis motor 11, an X-axis motor 13, and a Y-axis motor 14, and moves the spindle relative to the work material supported on the upper surface of a table (not shown) in each XYZ axis direction. To do. The tool changer includes a magazine motor 15, drives a tool magazine (not shown) that stores a plurality of tools, and exchanges the tool mounted on the main shaft with another tool. The Z-axis motor 11, the main shaft motor 12, the X-axis motor 13, the Y-axis motor 14, and the magazine motor 15 are servo motors. In the present embodiment, the Z-axis motor 11, the main shaft motor 12, the X-axis motor 13, the Y-axis motor 14, and the magazine motor 15 are collectively referred to as motors 11 to 15.

  The machine tool 10 further includes an operation panel 16. The operation panel 16 includes an input unit 17 and a display unit 18. The input unit 17 is a device for performing various inputs, instructions, settings, and the like. The display unit 18 is a device that displays various screens. The operation panel 16 is connected to the input / output unit 25 of the numerical controller 20. The Z-axis motor 11 includes an encoder 11A. The spindle motor 12 includes an encoder 12A. The X-axis motor 13 includes an encoder 13A. The Y-axis motor 14 includes an encoder 14A. The magazine motor 15 includes an encoder 15A. The encoders 11A to 15A are respectively connected to drive circuits 26 to 30 described later of the numerical controller 20.

  The electrical configuration of the numerical controller 20 will be described. The numerical control device 20 includes a CPU 21, a ROM 22, a RAM 23, a storage device 24, an input / output unit 25, drive circuits 26 to 30, and the like. The CPU 21 performs overall control of the numerical control device 20. The ROM 22 stores various programs such as a speed calculation program. The speed calculation program is a program for executing a speed calculation process (see FIGS. 4 and 5) described later. The RAM 23 stores various data during execution of various processes. The storage device 24 is a nonvolatile memory, and stores various data in addition to an NC program for processing, for example. The input / output unit 25 is connected to the operation panel 16. The drive circuits 26 to 30 are servo amplifiers. The drive circuit 26 is connected to the Z-axis motor 11 and the encoder 11B. The drive circuit 27 is connected to the spindle motor 12 and the encoder 12A. The drive circuit 28 is connected to the X-axis motor 13 and the encoder 13A. The drive circuit 29 is connected to the Y-axis motor 14 and the encoder 14A. The drive circuit 30 is connected to the magazine motor 15 and the encoder 15A.

  The CPU 21 reads an NC program for machining the work material, and drives a control command for moving each drive axis such as a feed axis (X axis, Y axis, Z axis), main axis, and magazine axis to a target position. Transmit to circuits 26-30. The drive circuits 26 to 30 output drive currents (pulses) to the respective motors 11 to 15 corresponding to the control commands (drive signals) received from the CPU 21. The drive circuits 26-30 receive feedback signals (position and speed signals) from the encoders 11A-15A, and control the positions and speeds of the motors 11-15. The drive circuits 26 to 30 are servo amplifiers that drive the servo amplifier, and may be constituted by, for example, FPGA circuits.

  The specific acceleration / deceleration control of the servo motor will be described with reference to FIG. The specific acceleration / deceleration control is, for example, acceleration / deceleration control performed for a specific servo motor having the maximum output torque characteristic M2. The maximum output torque characteristic M2 has a characteristic that, in the region on the high rotation speed side from the rotation speed R1, the slope of decrease of the maximum output torque of the servo motor is not constant but becomes gentle as the rotation speed increases. For example, if the servo motor is used for a long time in a state where the output torque exceeds the maximum output torque, the temperature of the servo motor rises and there is a high possibility that overheating will occur. Torque and acceleration are in a proportional relationship. Therefore, the CPU 21 performs acceleration / deceleration control (specific acceleration / deceleration control) for the operation of the drive shaft driven by the servomotor so that the output torque of the servomotor does not exceed the maximum output torque.

  The output torque characteristic Q2 is an output torque characteristic of the servo motor when the specific acceleration / deceleration control is applied. The output torque characteristic Q2 is within the range of the maximum output torque characteristic M2. In the specific acceleration / deceleration control, for example, the operation at the start of movement of the feed axis such as the X-axis is performed with an acceleration increase period T1 at the beginning of acceleration, a first acceleration constant period T2 at which acceleration is constant, and an acceleration that decreases acceleration in accordance with the end of acceleration. The period is divided into three periods of a decrease period T6. Further, the acceleration decrease period T6 is divided into three periods: a first acceleration decrease period T3 in which acceleration is decreased in accordance with the end of the period T2, a second acceleration constant period T5 in which acceleration is constant, and a second acceleration decrease period T4 in which acceleration is terminated. To do. The periods T1, T2, T3, and T4 are the same as the periods T1 to T4 of the two-stage acceleration / deceleration control shown in FIG. In the specific acceleration / deceleration control, a period T5 where the acceleration is constant is provided between the periods T3 and T4. Therefore, the output torque characteristic Q2 can reduce the output torque step by step in accordance with the characteristic that the maximum output torque gradually decreases in the region on the high rotation speed side from the rotation speed R1. Therefore, the output torque characteristic Q2 can be approximated so that the output torque does not exceed the maximum output torque in the region on the high rotation speed side from the rotation speed R1.

  The acceleration pattern in the specific acceleration / deceleration control will be described with reference to FIG. A solid line in FIG. 3 shows an acceleration pattern from the start of movement to the end of movement in the specific acceleration / deceleration control of the X-axis motor 13. A dotted line indicates a speed pattern corresponding to the acceleration pattern of the X-axis motor 13. The time constant t1 of the acceleration increase speed a1 in the acceleration increase period T1 may be set smaller than the time constant t2 of the acceleration decrease speed a2 in the acceleration decrease period T6. The specific acceleration / deceleration control can approximate the output torque on the low rotation speed side of the servo motor to the maximum output torque (see FIG. 2). The X-axis motor 13 is a specific servo motor having a characteristic that the slope at which the maximum output torque decreases in the region on the high rotation speed side from the rotation speed R1 becomes gentler as the rotation speed increases. For example, the operation of the X-axis motor 13 at the start of X-axis movement is divided into five periods in the order of periods T1, T2, T3, T5, and T4 as described above. The operator inputs and sets the speed V1 after the period T4 and the speed V2 after the period T2 through the input unit 17 of the operation panel 16 in advance. The speeds V1 and V2 may be stored in the RAM 23, for example.

An acceleration calculation method in each of the periods T1 to T5 will be described. In the acceleration increase period T1, the target acceleration is set to the first acceleration A1. The first acceleration A1 is calculated based on the speed V2 input and set by the operator. The relationship between the speed V2 and the first acceleration A1 is Expression (1).
・ V2 = A1 × T1 / 2 + A1 × T2 (1)
Therefore, the first acceleration A1 can be calculated by the following formula (2) obtained by modifying the formula (1).
A1 = 2 × V2 / (T1 + 2 × T2) (2)
The inclination of the acceleration change during the acceleration increase period T1 is the acceleration increase speed a1. The acceleration increasing speed a1 is constant at A1 / T1. The acceleration A in the acceleration increase period T1 can be calculated by the following equation (3). t is the elapsed time from the start of acceleration (start of movement).
A = A1 × t / T1 (3)

  In the first constant acceleration period T2, the first acceleration A1 is maintained, and after the period T2, the X-axis speed V is controlled to be the speed V2 input and set by the operator. In the first acceleration constant period T2, in order to maintain the first acceleration A1 corresponding to the maximum output torque of the X-axis motor 13 or the torque in the vicinity thereof, the effective use of the maximum output torque of the X-axis motor 13 and the shortening of the movement time are achieved. I can plan.

In the first acceleration decrease period T3, the target acceleration is set to the second acceleration A2. The second acceleration A2 is calculated by the following formula (4) based on the speeds V1 and V2 input by the operator.
A2 = (2 × (V1−V2) −A1 × T3) / (T3 + T4 + 2 × T5) (4)
The slope of the first acceleration decrease period T3 is the first acceleration decrease speed a3. The first acceleration decrease speed a3 = (A2-A1) / T3 is constant. The acceleration A in the first acceleration decrease period T3 can be calculated by the following equation (5).
A = A1- (A1-A2) * {t- (T1 + T2)} / T3 (5)

  In the second acceleration constant period T5, the second acceleration A2 calculated by the equation (4) is maintained. When the period T5 = 0 is set, the specific acceleration / deceleration control can be changed to the two-stage acceleration / deceleration control.

In the second acceleration decrease period T4, the target acceleration is set to zero. The inclination of the second acceleration decrease period T4 is the second acceleration decrease speed a4. The second acceleration decrease speed a4 is constant at −A2 / T4. The second acceleration decrease speed a4 may be set larger than the first acceleration decrease speed a3. The acceleration A in the second acceleration decrease period T4 can be calculated by the following equation (6).
A = A2-A2 * {t- (T1 + T2 + T3 + T5)} / T4 (6)

  The acceleration pattern of the X-axis motor 13 at the end of the X-axis movement is reverse to the order of the acceleration pattern at the start of the X-axis movement, and is divided into five periods T4, T5, T3, T2, and T1. Since the acceleration in each period at the start of movement of the X axis is positive, the acceleration in each period at the end of movement is negative. The calculation method may be calculated by reversing the sign of acceleration using the same formula as the above calculation method. That is, the first acceleration A1 and the second acceleration A2 at the end of movement are negative values (-A1 and -A2).

  The speed calculation process will be described with reference to FIGS. When the control command generated by interpreting the NC program is, for example, an X-axis movement command, the CPU 21 determines the acceleration pattern of the X-axis motor 13 up to the target arrival position and reads the speed calculation program from the ROM 22. This process is executed.

  As shown in FIG. 4, the CPU 21 calculates a first acceleration A1 and a second acceleration A2 (S1). The first acceleration A1 is calculated by the above equation (2), and the second acceleration A2 is calculated by the above equation (4). The CPU 21 determines whether or not the acceleration of the X axis has started (S2). Until the acceleration is started (S2: NO), the CPU 21 returns to S2 and stands by. When the acceleration is started (S2: YES), the CPU 21 determines which of the periods T1 to T5 the current acceleration period is based on the acceleration pattern in FIG. 3 and the time t from the time when the acceleration is started (S3 to S3). S7). When the current acceleration period is the acceleration increase period T1 (S3: YES), the CPU 21 calculates the acceleration A by the above equation (3) (S8). The CPU 21 calculates the speed V from the acceleration A (S14). The CPU 21 generates a position command from the calculated speed V and transmits the position command and the speed command to the drive circuit 29 of the X-axis motor 13. The drive circuit 29 drives and controls the X-axis motor 13 based on the received position command and speed command. The X axis moves at a speed V. The CPU 21 returns to S3.

  When the current acceleration period is the first acceleration constant period T2 (S3: NO, S4: YES), the CPU 21 sets the acceleration to the first acceleration A1 (S9). The CPU 21 calculates the speed V from the first acceleration A1 (S14). The CPU 21 generates a position command from the calculated speed V and transmits the position command and the speed command to the drive circuit 29 of the X-axis motor 13. The CPU 21 returns to S3.

  When the current acceleration period is the first acceleration decrease period T3 (S3: NO, S4: NO, S5: YES), the CPU 21 calculates the acceleration A based on the above equation (5) (S10). The CPU 21 calculates the speed V from the acceleration A (S14). The CPU 21 generates a position command from the calculated speed V and transmits the position command and the speed command to the drive circuit 29 of the X-axis motor 13. The CPU 21 returns to S3.

  When the current acceleration period is the second acceleration constant period T5 (S3: NO, S4: NO, S5: NO, S6: YES), the CPU 21 sets the acceleration to the second acceleration A2 (S11). The CPU 21 calculates the speed V from the second acceleration A2 (S14). The CPU 21 generates a position command from the calculated speed V and transmits the position command and the speed command to the drive circuit 29 of the X-axis motor 13. The CPU 21 returns to S3.

  When the current acceleration period is the second acceleration decrease period T4 (S3: NO, S4: NO, S5: NO, S6: NO, S7: YES), the CPU 21 calculates the acceleration A based on the above equation (6). (S12). The CPU 21 calculates the speed V from the acceleration A (S14). The CPU 21 generates a position command from the calculated speed V and transmits the position command and the speed command to the drive circuit 29 of the X-axis motor 13. The CPU 21 returns to S3.

  When the second acceleration decrease period T4 at the start of the X-axis movement ends and the current acceleration period is not any of the periods T1 to T5 (S3: NO, S4: NO, S5: NO, S6: NO, S7: NO As shown in FIG. 5, the CPU 21 determines whether or not the movement of the X axis is stopped (S15). Since the X axis is moving (S15: NO), the acceleration is set to 0 (S16) and the speed V1 is set (S17). Therefore, the X axis continues to move at the speed V1. The CPU 21 returns to S3.

  The X axis starts decelerating at time p1. Deceleration is acceleration in the negative direction. The CPU 21 determines the current acceleration period again based on the time q from the time p1 when the deceleration starts, similarly to the start of the movement of the X axis (S3 to S7). As described above, the acceleration pattern at the end of the movement of the X-axis is in the order of the periods T4, T5, T3, T2, and T1, contrary to the start of movement. The CPU 21 calculates acceleration and speed according to the current acceleration period (S8 to S12, S14).

  When the acceleration increase period T1 ends (S3: NO, S4: NO, S5: NO, S6: NO, S7: NO), as shown in FIG. 5, the X-axis stops moving at a speed V = 0. (S15: YES), CPU21 complete | finishes this process. The movement to the X axis target position is completed.

  As described above, the numerical controller 20 of the present embodiment controls the operation of the machine tool 10. The machine tool 10 includes feed axes (drive axes) such as an X axis, a Y axis, and a Z axis that are driven by motors 11 to 15 that are servo motors. The CPU 21 of the numerical controller 20 performs specific acceleration / deceleration control at the start and end of movement of the feed axis. Similar to the two-stage acceleration / deceleration control, the specific acceleration / deceleration control has an acceleration increase period T1, a first acceleration constant period T2, and an acceleration decrease period T6. The time constant t1 in the acceleration increase period T1 is made smaller than the time constant t2 in the acceleration decrease period T6. Therefore, the numerical controller 20 can effectively use the maximum output torque on the low-speed rotation side of the servo motor.

  The maximum output torque characteristic M2 of the specific servo motor has a characteristic that the maximum output torque gradually decreases in a region from a certain rotation speed R1 to a high rotation speed. In the conventional two-stage acceleration / deceleration control, the output torque may exceed the maximum output torque in the region on the high rotation speed side of the servo motor. In the specific acceleration / deceleration control, a second acceleration constant period T5 is provided in a portion excluding the start time and end time of the acceleration decrease period T6 corresponding to the high speed side region. Therefore, the numerical control device 20 can reduce the output torque stepwise in the acceleration reduction period T6, and therefore can be approximated so that the output torque does not exceed the maximum output torque even in the region on the high speed side. Therefore, the numerical control device 20 can effectively use the output torque in both the low rotation speed side and the high rotation speed side of the servo motor.

  In the above description, the machine tool 10 is an example of the machine of the present invention. The CPU 21 is an example of a control unit of the present invention. Each processing step of the speed calculation processing shown in FIGS. 4 and 5 is an example of the control process of the present invention.

  Needless to say, the present invention is not limited to the above-described embodiment, and various modifications are possible. The output torque characteristic Q2 of the specific acceleration / deceleration control shown in FIG. 2 is provided with one constant second acceleration constant period T5 except for the start and end of the acceleration decrease period T6. A plurality of periods may be provided. For example, the output torque characteristic Q3 of the motor shown in FIG. 6 is a modification of the output torque characteristic Q2 of the motor in the specific acceleration / deceleration control. The output torque characteristic Q3 is within the range of the maximum output torque characteristic M3 of the motor. In the output torque characteristic Q3, two acceleration constant periods T51 and T52 are provided at portions other than the start and end of the acceleration decrease period T6, and a period T7 in which the acceleration is reduced is provided between the periods T51 and T52. Therefore, the output torque characteristic Q3 can further reduce the output torque in a stepwise manner in the region on the high rotation speed side from the rotation speed R2, so that the output torque is further approximated to the maximum output torque compared to the output torque characteristic Q2 of the above embodiment. it can.

  In the above embodiment, the specific acceleration / deceleration control has been described by taking the X-axis feed operation driven by the X-axis motor 13 as an example. However, other drive axes such as the Y-axis, Z-axis, main axis, and magazine axis are drive axes. Also, specific acceleration / deceleration control may be used.

  In the above-described embodiment, for example, the one-stage acceleration / deceleration control, the two-stage acceleration / deceleration control, and the specific acceleration / deceleration control may be switched in accordance with the maximum output torque characteristic of the servo motor that drives the target axis of the movement command. The one-stage acceleration / deceleration control is a control for setting the time constant of the acceleration increasing speed during the acceleration increasing period and the time constant of the acceleration decreasing speed during the acceleration decreasing period.

  In the specific acceleration / deceleration control of the above embodiment, the time constant t1 of the acceleration increase speed during the acceleration increase period T1 is set smaller than the time constant t2 of the acceleration decrease speed during the acceleration decrease period T6, but the time constants t1 and t2 are the same. The time constant t2 may be smaller than the time constant t1.

  The drive circuits 26 to 30 of the above embodiment are provided in the numerical controller 20, but may be provided in the machine tool 10.

  The machine tool 10 of the above embodiment is a vertical machine tool whose main shaft extends in the Z-axis direction, but the present invention can also be applied to a horizontal machine tool whose main shaft extends in the horizontal direction.

  In the present embodiment, a microcomputer, ASIC (Application Specific Integrated Circuits), FPGA (Field Programmable Gate Array), or the like may be used as a processor instead of the CPU 21. The movement control process may be distributed by a plurality of processors. The ROM 22 and the storage device 24 for storing the program may be configured by other non-transitory storage media such as an HDD and / or a storage device. The non-transitory storage medium may be any storage medium that can retain information regardless of the period in which the information is stored. The non-transitory storage medium may not include a temporary storage medium (for example, a signal to be transmitted). The tap acceleration / deceleration control program may be downloaded from a server connected to a network (not shown) (that is, transmitted as a transmission signal) and stored in a storage device such as a flash memory. In this case, the program may be stored in a non-temporary storage medium such as an HDD provided in the server.

10 Machine Tool 20 Numerical Control Device 21 CPU
11-15 Motor M2 Maximum output torque characteristic Q2 Output torque characteristic T1 Acceleration increase period T2 First acceleration constant period T3 First acceleration decrease period T4 Second acceleration decrease period T5 Second acceleration constant period T6 Acceleration decrease period a1 Acceleration increase speed a2 Acceleration decreasing speed t1 time constant t2 time constant

Claims (3)

A machine having a servo motor and a drive shaft driven by the servo motor is controlled, an acceleration increase period during which acceleration is increased at the start of acceleration of the drive shaft, and a constant acceleration at the end of acceleration of the drive shaft. In a numerical control device including a control unit that performs acceleration / deceleration control having one acceleration constant period and an acceleration decrease period in which the acceleration decreases after the first acceleration constant period,
The control unit makes the time constant of the acceleration increase speed in the acceleration increase period smaller than the time constant of the acceleration decrease speed in the acceleration decrease period, and excludes the start time and end time of the acceleration decrease period, A numerical control apparatus characterized in that a second acceleration constant period is provided to make acceleration constant. The controller is
Among the maximum output torque characteristics that are the maximum output torque corresponding to the rotation speed of the servo motor, the inclination of the predetermined portion where the maximum output torque is reduced becomes smaller as the rotation speed becomes higher. The second acceleration constant period is provided in a portion excluding the start and end of the acceleration decrease period corresponding to a predetermined portion, and the output torque of the servo motor proportional to the acceleration with respect to time in the acceleration / deceleration control of the drive shaft is The numerical control apparatus according to claim 1, wherein control is performed so that the maximum output torque is not exceeded during the acceleration increase period, the first acceleration constant period, and the acceleration decrease period. A machine having a servo motor and a drive shaft driven by the servo motor is controlled, an acceleration increase period during which acceleration is increased at the start of acceleration of the drive shaft, and a constant acceleration at the end of acceleration of the drive shaft. In a control method of a numerical controller that performs a control step of performing acceleration / deceleration control having one acceleration constant period and an acceleration decrease period in which the acceleration decreases after the first acceleration constant period,
In the control step, the time constant of the acceleration increase speed in the acceleration increase period is made smaller than the time constant of the acceleration decrease speed in the acceleration decrease period, and at the part excluding the start time and end time of the acceleration decrease period, A control method comprising a second acceleration constant period for making the acceleration constant.

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