Motor control device

Abstract

Provided is a technique capable of detecting correct acceleration and deceleration in orientation control of an induction motor and capable of stopping a rotating shaft at a specific target position in a shorter time. A motor control device for controlling an induction motor for driving a rotating shaft and executing directional control for stopping the rotating shaft at a target position, the motor control device being provided with: a speed comparison unit for calculating the difference between the actual speed of the rotating shaft and a speed command; a speed command calculation unit that, when the absolute value of the difference is less than a predetermined threshold value, changes the speed command so that the absolute value of the difference is equal to or greater than the threshold value; an acceleration command calculation unit that calculates an acceleration command during directional control on the basis of acceleration / deceleration calculated from the actual speed of the rotating shaft when the speed command has been changed; and a trajectory calculation unit that calculates, on the basis of the acceleration command, at least one of a position command until the target position is reached and a speed command.

Description

Technical Field

[0001] The present disclosure relates to a motor control device. Background Art

[0002] In the past, the servo motor driving the rotating shaft of industrial machinery such as machine tools was controlled by a motor control device to control its rotation amount, speed, torque, etc. As a control method based on the motor control device, for example, directional control is known to stop the main shaft of the rotating industrial machinery at a specific position for the purpose of tool replacement, etc. (for example, refer to Patent Document 1).

[0003] In particular, the directional control that detects the maximum acceleration / deceleration when the servo motor rotating the spindle is accelerated / decelerated by the maximum current that can be given at the current time point, and stops the spindle at a specific position by using the acceleration command of the detected maximum acceleration / deceleration is called optimal directional control. According to the optimal directional control, the spindle can be stopped at a specific position in the shortest time.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-27684 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, in the optimal directional control, an directional speed different from the current speed is set in order to detect the maximum acceleration / deceleration, and speed control is performed to switch from the current speed to the directional speed. However, in the induction motor used as a servo motor, there is a characteristic that it takes time for the magnetic flux to fully rise during acceleration / deceleration. Therefore, when the difference between the directional speed and the current speed is small, the acceleration / deceleration detection time is insufficient, and therefore, the small acceleration / deceleration in the state where the magnetic flux does not fully rise, that is, the torque is not obtained, is mistaken for the maximum acceleration / deceleration, and the correct maximum acceleration / deceleration cannot be detected. Therefore, when executing directional control based on acceleration instructions of acceleration / deceleration that is smaller than the maximum acceleration / deceleration, there is a problem that the directional time becomes longer.

[0009] An object of the present disclosure is to provide a technology capable of detecting accurate acceleration and deceleration in directional control of an induction motor and stopping a rotating shaft at a specific target position in a shorter time.

[0010] Means for solving problems

[0011] The present disclosure relates to a motor control device that controls an induction motor that drives a rotating shaft and performs directional control to stop the rotating shaft at a target position. The motor control device includes: a speed comparison unit that calculates the difference between the actual speed of the rotating shaft and a speed command; a speed command calculation unit that changes the speed command when the absolute value of the difference is smaller than a specified threshold value so that the absolute value of the difference is greater than the threshold value; an acceleration command calculation unit that calculates the acceleration command during the directional control based on the acceleration / deceleration calculated according to the actual speed of the rotating shaft when the speed command is changed; and a trajectory calculation unit that calculates at least one of a position command and a speed command until reaching the target position based on the acceleration command.

[0012] Effects of the Invention

[0013] According to the present disclosure, it is possible to provide a technology that can detect accurate acceleration and deceleration in directional control of an induction motor and can stop a rotating shaft at a specific target position in a shorter time. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a block diagram showing the structure of a control device according to one embodiment of the present disclosure.

[0015] Figure 2 1 is a diagram showing a primary-side d-axis current, a secondary-side d-axis interlinkage magnetic flux, a primary-side q-axis current, and a torque T of an induction motor.

[0016] Figure 3 Yes means Figure 2 Graph of speed changes from time t0 to time t3 and from time t3 to time t1.

[0017] Figure 4 It means in Figure 2 A diagram showing the magnitudes of the maximum acceleration / deceleration values ​​detected from time t0 to time t3 and from time t0 to time t1.

[0018] Figure 5 This is a flowchart showing a process procedure of speed control in directional control according to one embodiment of the present disclosure.

[0019] Figure 6 : is a flowchart showing the procedure of acceleration calculation processing.

[0020] Figure 7 This is a flowchart showing a process procedure of positioning control in directional control according to one embodiment of the present disclosure.

[0021] Figure 8 This is a diagram for explaining a position instruction (orbit) calculation process according to one embodiment of the present disclosure.

[0022] Fig. 9 This is a diagram for explaining positioning control according to one embodiment of the present disclosure.

[0023] Fig.10 This is a flowchart showing the procedure of position instruction (orbit) calculation processing.

[0024] Fig.11 1 is a diagram showing conventional directional control, and is a diagram showing a change in speed when the vehicle stops at a target position by accelerating and then decelerating.

[0025] Fig.12 1 is a diagram showing directional control according to one embodiment of the present disclosure, and is a diagram showing a change in speed when the vehicle stops at a target position by accelerating and then decelerating.

[0026] Fig.13 1 is a diagram showing conventional directional control, and is a diagram showing speed changes when the vehicle stops at a target position only by deceleration.

[0027] Fig.14 1 is a diagram showing directional control according to one embodiment of the present disclosure, and is a diagram showing a speed change when the vehicle stops at a target position only by deceleration.

[0028] Fig.15 It is a block diagram showing a configuration of a control device according to a modified example of one embodiment of the present disclosure. DETAILED DESCRIPTION

[0029] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings.

[0030] Figure 1 1 is a block diagram showing the structure of a control device 1 according to an embodiment of the present disclosure. The control device 1 according to the present embodiment is a control device for driving a motor 3 for a rotating shaft of an industrial machine such as a machine tool or a robot. Figure 1 As shown, the control device 1 includes an acceleration command calculation unit 11 , a trajectory calculation unit 12 , an integrator 13 , a position control unit 14 , a speed comparison unit 15 , a speed command calculation unit 16 , a switching unit 17 , a speed control unit 18 , and a current control unit 19 .

[0031] The control device 1 performs directional control to stop the rotating axis at a specific target position through the above-mentioned functional units. In particular, when the current speed (initial speed) is close to the directional speed and the difference between the two is small during the directional control, the control device 1 can detect the correct acceleration and deceleration by changing the directional speed in order to ensure sufficient acceleration and deceleration detection time, and can stop the spindle of the machine tool at a specific target position in a shorter time.

[0032] The control device 1 is constituted by, for example, a computer having a memory such as a ROM (read only memory) and a RAM (random access memory) connected to each other via a bus, a CPU (control processing unit), and a communication control unit. The functions and actions of the above-mentioned functional units are achieved through the cooperation of the CPU, the memory, and the control program stored in the memory mounted on the above-mentioned computer.

[0033] The control device 1 is connected to a CNC (Computer Numerical Controller) (not shown), and signals such as a speed command, a position command, and an orientation command are input from the CNC to the control device 1 .

[0034] In addition, if Figure 1 As shown, the control device 1 is electrically connected to a current sensor 4, which detects a current value given to the motor 3 according to a voltage command applied to the motor 3 in order to drive and control the motor 3. In addition, the control device 1 is electrically connected to a position / speed sensor 5, which is used to detect the position and speed of the motor 3.

[0035] The motor 3 drives a rotating shaft of an industrial machine such as a machine tool or a robot. The motor 3 of this embodiment is a servo motor formed of an induction motor. The induction motor generates an induced current in the rotor due to a rotating magnetic field generated by a stator, and generates a rotation torque corresponding to slippage.

[0036] The current sensor 4 detects the current flowing through the motor 3 in accordance with the voltage command applied to the motor 3. The current value detected by the current sensor 4 is sent to the current control unit 19.

[0037] The position / speed sensor 5 is provided at the motor 3 to detect the position and speed of the motor 3. The position / speed values ​​of the motor 3 detected by the position / speed sensor 5 are respectively sent to the acceleration command calculation unit 11, the integrator 13, the speed comparison unit 15, and the speed control unit 18. In addition, as a specific position / speed sensor 5, for example, an encoder is used.

[0038] The acceleration command calculation unit 11 calculates the acceleration command during the directional control based on the acceleration / deceleration calculated from the actual speed of the rotating shaft when the speed command is changed by the speed command calculation unit 16 described later. That is, when the current speed (initial speed) is close to the directional speed during the directional control, the acceleration command calculation unit 11 calculates the acceleration / deceleration based on the actual speed when the directional speed is changed to ensure sufficient acceleration / deceleration detection time, and calculates the acceleration command based on the calculated acceleration / deceleration. The actual speed of the rotating shaft is obtained based on the position / speed detection value sent from the position / speed sensor 5.

[0039] In addition, it is preferred that the acceleration command calculation unit 11 calculates the acceleration and deceleration speed when the maximum current that can be given to the motor 3 at that time point is applied to the speed control from the current speed (initial speed) to the actual speed to the directional speed changed in the above case at a predetermined period. Thereby, the acceleration command calculation based on the correct maximum acceleration and deceleration speed can be performed.

[0040] Specifically, it is preferred that the acceleration instruction calculation unit 11 uses the maximum acceleration / deceleration value of the calculated acceleration / deceleration as the absolute value of the acceleration instruction. However, when it is applied to a wider range of directional control in addition to the optimal directional control, the acceleration instruction is not limited to the maximum value of the calculated acceleration / deceleration, and the acceleration instruction can also be calculated based on the average value or instantaneous value.

[0041] The acceleration command calculation unit 11 calculates acceleration and deceleration for each directional control. The directional control is performed, for example, when a tool of a machine tool is replaced. Since the inertia of the spindle changes when the tool is replaced, the detection of acceleration and deceleration is particularly important.

[0042] The trajectory calculation unit 12 calculates a position command for reaching a specific target stop position based on the acceleration command of the directional control. The acceleration command is obtained from the acceleration command calculation unit 11 described above.

[0043] Preferably, the trajectory calculation unit 12 calculates the position command for acceleration and deceleration at the maximum acceleration and deceleration so that the time to reach the target stop position is the shortest. Specifically, preferably, the position command for stopping at the target position is calculated by accelerating at the maximum acceleration and then decelerating at the maximum deceleration.

[0044] The integrator 13 integrates the actual speed of the rotating shaft to obtain the actual position. The obtained actual position is sent to the position control unit 14. The actual speed is obtained based on the position / speed detection value sent from the position / speed sensor 5.

[0045] The position control unit 14 calculates a speed command based on the position deviation between the actual position from the integrator 13 and the position command. The calculated speed command is sent to the switching unit 17.

[0046] The speed comparison unit 15 calculates the difference between the actual speed of the rotating shaft and the speed command. The difference obtained by calculation is sent to the speed command calculation unit 16. The actual speed is obtained based on the position / speed detection value sent from the position / speed sensor 5. The speed command is input from the CNC.

[0047] When the absolute value of the difference is smaller than a predetermined threshold value, the speed command calculation unit 16 changes the speed command so that the absolute value of the difference becomes equal to or greater than the threshold value. The changed speed command is sent to the switching unit 17 .

[0048] Preferably, the threshold value is set for each motor 3. Specifically, preferably, the threshold value is set based on the magnetic flux rise time corresponding to the resistance and inductance of the induction motor. Alternatively, the threshold value may be calculated and set based on the current speed.

[0049] Specifically, it is preferable that the speed command calculation unit 16 sets the actual speed (current speed) to v st , set the speed command to v1 and the threshold to v th When the actual speed v st The absolute value of the difference between the speed command v1 and the threshold value v th If the speed command v1 is smaller than the speed command v2, the speed command v1 is changed to the speed command v represented by the following formula (1): 21 Or the speed command v expressed by the following formula (2) 22 .

[0050] [Mathematical formula 1]

[0051] v 21 =v st -v th Formula (1)

[0052] v 22 =v st +v th Formula (2)

[0053] The switching unit 17 switches the speed command from the position control unit 14 and the speed command from the speed command calculation unit 16. That is, the switching unit 17 switches between the speed control (sequence 1) and the positioning control (sequence 2) in the orientation control of the present embodiment.

[0054] The speed control unit 18 calculates a current command based on the speed command from the switching unit 17. The calculated and acquired current command is sent to the current control unit 19.

[0055] The current control unit 19 calculates a voltage command to be applied to the motor 3 based on the current command, and applies a current corresponding to the calculated voltage command to the motor 3. In addition, the current control unit 19 obtains a current value detected by the current sensor 4, and performs current feedback control so that the difference between the obtained current value and the command value becomes zero.

[0056] Next, refer to Figure 2 to Figure 4 The characteristics of the induction motor constituting the motor 3 will be described in detail.

[0057] First, slip frequency type vector control is applied to the motor 3 composed of an induction motor. The slip frequency type vector control controls the sum of the slip frequency, which is the frequency of the current flowing through the rotor winding of the induction motor, and the motor rotation frequency to be the output frequency of the inverter. At this time, the torque T of the motor 3 is expressed by the following formula (3).

[0058] [Mathematical formula 2]

[0059]

[0060] [In formula (3), P n is the number of pole pairs, M is the mutual inductance, L2 is the secondary side inductance, is the secondary side d-axis cross-linkage flux, i 1q is the primary side q-axis current. ]

[0061] In addition, the secondary side d-axis cross-linkage flux According to the relationship of the following equation (4), the time constant τ2 represented by the following equation (5) increases.

[0062] [Mathematical formula 3]

[0063]

[0064] [In formula (4), R2 is the secondary side resistance, i 1d is the primary side d-axis current. ]

[0065] [Formula 4]

[0066]

[0067] Here, Figure 2 is the primary-side d-axis current i of the motor 3 formed by an induction motor. 1d , secondary side d-axis cross-linkage flux Primary side q-axis current i 1q And the diagram of torque T. Specifically, Figure 2 is a graph showing the time variation of each parameter when it rises. Figure 2 As shown, the primary side d-axis current i 1dis a controllable current that contributes to the magnetic flux, which rises from time t0 and reaches a maximum value i* at time t3 1d Similarly, as shown in the above equation (3), the primary side q-axis current i 1q is a controllable current that contributes to the torque T, which rises from time t0 and reaches a maximum value i* at time t3 1q .

[0068] On the other hand, the secondary side d-axis cross-linkage flux It rises from time t0 and does not reach its maximum value Mi* at time t3 1d , we can see that its time constant τ2 is long. Specifically, the primary side d-axis current i 1d , primary side q axis current i 1q The time constant of the current control is less than 1ms. In contrast, the secondary side d-axis cross-linkage flux The time constant τ2 is 1 ms to 500 ms. In addition, as shown in the above equation (5), the secondary side d-axis interlinkage flux The time constant τ2 is a value inherent to the motor represented by the secondary-side inductance L2 and the secondary-side resistance R2, and its rise time cannot be controlled.

[0069] Therefore, if Figure 2 As shown, the d-axis flux linkage with the secondary side Similarly, as shown in the above formula (3), it is expressed as the secondary side d-axis cross-linkage flux The primary side q-axis current i 1q The time constant of the torque T of the motor 3 obtained by multiplying the product of the above is long and the increase is slow. That is, the motor 3 formed by the induction motor has a characteristic that it takes time for the magnetic flux to fully increase during acceleration and deceleration, and thus the increase of the torque is also slow.

[0070] Figure 3 Yes means Figure 2 The speed change diagram from time t0 to time t3 and from time t3 to time t1 is shown. At time t0 to time t3, the magnetic flux and torque of the motor 3 are not fully increased as described above. Therefore, it can be seen that the speed slope, that is, from the initial speed v st In contrast, the period from time t3 to time t1 includes a state where the magnetic flux and torque of the motor 3 are sufficiently increased, and therefore, it can be seen that the deceleration is greater than that from time t0 to time t3.

[0071] in addition, Figure 4 It means in Figure 2 The maximum acceleration / deceleration values ​​detected at time t0 to time t3 and time t0 to time t1 are shown in FIG. Figure 4It can be seen that the maximum value of the acceleration / deceleration detected between time t0 and time t1 is greater than the maximum value of the acceleration / deceleration detected between time t0 and time t3.

[0072] Therefore, in order to detect the correct acceleration and deceleration and the maximum acceleration and deceleration, and to ensure sufficient acceleration and deceleration detection time during directional control, it is particularly important to set the directional speed in a manner that fully ensures the difference between the initial speed and the directional speed. Therefore, in this embodiment, when the current speed (initial speed) is close to the directional speed when switching from the current speed (initial speed) to the speed control of the directional speed, the directional speed is changed so that the difference between the initial speed and the directional speed is greater than the above threshold. Thus, sufficient acceleration and deceleration detection time is ensured, and the correct acceleration and deceleration and the maximum acceleration and deceleration can be detected.

[0073] Next, the procedure of the directional control processing according to the present embodiment will be described in detail with reference to the drawings.

[0074] Figure 5 1 is a flowchart showing the process of processing speed control in directional control of the present embodiment. The directional control of the present embodiment is executed by the control device 1, for example, when replacing a tool of a machine tool. In addition, in the present embodiment, the speed control based on the speed command is set as sequence 1, and the positioning control based on the position command is set as sequence 2.

[0075] In step S1, speed control is performed (sequence 1) to make the speed of the motor 3 reach the initial speed v st Then, the process proceeds to step S2. Here, the induction motor has the characteristic that even if the magnetic flux rises sufficiently, it cannot generate sufficient torque at high speed. On the other hand, although sufficient torque is generated at low speed, it takes time to align the phases to reach the target position. Therefore, it is preferable to use the initial velocity v st , set to a moderate speed so that the torque can be obtained moderately and the phase alignment time used to reach the target position can be shortened.

[0076] In step S2, a positioning command (orientation command) is input to the control device 1. The positioning command (orientation command) is sent from the above-mentioned CNC. Thereafter, the process proceeds to step S3.

[0077] In step S3, the directional speed command v1 and the initial speed v st The difference is the speed deviation. Then, enter step S4.

[0078] In step S4, the absolute value of the speed deviation |v1-v st |Is it greater than the set value (threshold) v thIf the judgment is yes, the process proceeds to step S6. If the judgment is no, the process proceeds to step S5, and after changing the orientation speed command v1 to the orientation speed command v2, the process proceeds to step S6. As the orientation speed command v2, for example, as shown in the above formula (1), it is set from the initial speed v st Subtract the set value (threshold) v th The speed command obtained.

[0079] In step S6, the acceleration calculation (acceleration detection) process is performed. Then, the process proceeds to step S7. Figure 6 The details of the acceleration calculation (acceleration detection) process will be described. Figure 6 : is a flowchart showing the procedure of acceleration calculation processing.

[0080] In step S61, the acceleration a is calculated. Specifically, the acceleration a is calculated by the following equation (6). Then, the process proceeds to step S62.

[0081] [Formula 5]

[0082]

[0083] [In formula (6), Δt is the sampling period, v i is the actual speed at time t = iΔt, v i-n is the actual speed at time t = (in)Δt, n is a natural number, and i is a variable.]

[0084] In step S62, it is determined whether the absolute value |a| of the acceleration a calculated in step S61 is greater than the maximum acceleration a max If the judgment is yes, the process proceeds to step S63. If the judgment is no, the process proceeds to step S64. max The initial value of is set to 0.

[0085] In step S63, the maximum acceleration a max The absolute value |a| of the acceleration a calculated in step S61 is updated. Then, the process proceeds to step S64.

[0086] In step S64, 1 is added to the variable i to set i=i+1, and the present process ends.

[0087] The acceleration calculation (acceleration detection) process described above is to convert the maximum acceleration a max As an example of calculating (detecting) acceleration, this acceleration calculation (acceleration detection) process is repeatedly executed until the current speed matches the orientation command speed, as described in step S7 below.

[0088] Return to Figure 5In step S7, it is determined whether the current speed is consistent with the directional command speed. If the determination is yes, the process proceeds to step S8. If the determination is no, the process returns to step S6 and the acceleration calculation (acceleration detection) process is repeatedly performed.

[0089] In step S8, the process switches to positioning control (sequence 2) and performs positioning control (sequence 2). Figure 7 Step S9. Figure 7 This is a flowchart showing the processing procedure of positioning control in directional control according to the present embodiment.

[0090] In step S9, the absolute value of the acceleration command a* is set as the calculated (detected) acceleration. Thereafter, the process proceeds to step S10.

[0091] In step S10, the position command (orbit) for stopping at the target position with the acceleration command a* is calculated. Then, the process proceeds to step S11. For details of the position command (orbit) calculation process, refer to Figure 8 to Figure 10 Provide explanation.

[0092] Figure 8 : is a diagram for explaining the position instruction (orbit) calculation process of this embodiment. Specifically, Figure 8 is a diagram showing the speed change in the directional control of this embodiment. Figure 8 As shown, when a positioning instruction (orientation instruction) is input to the control device 1 at time t0, the acceleration a0 (the maximum detected acceleration in the example of this embodiment) is detected by performing acceleration calculation (detection) processing during the period from time t0 to time t1 when the current speed (initial speed) reaches the orientation speed v0.

[0093] In addition, at this time, the acceleration command is calculated in such a way that the absolute value of the acceleration command |a*| becomes the calculated (detected) acceleration a0. Based on the calculated acceleration command and the position (phase angle) of the rotating axis at the start time t1 of the positioning control relative to the target stop position, the distance S1 moved from the start of the positioning control to the maximum acceleration and then the maximum deceleration to return to the directional speed v0 and the remaining distance S0 for the maximum deceleration to the target stop position are determined. After the positioning control starts, the acceleration command of the maximum acceleration and then the maximum deceleration is set to stop the rotating axis at the target position in the shortest time. However, depending on the position (phase angle) of the rotating axis at the start time t1 of the positioning control relative to the target stop position, sometimes it can also be an acceleration command of only maximum deceleration.

[0094] Fig. 9 is a diagram for explaining the positioning control of this embodiment. Specifically, Fig. 9Indicates the moving distance S in the rotation direction during the positioning control of the rotary axis. x .like Fig. 9 As shown, the moving distance S x It is the sum of the distance S1 moved from the start of positioning control until the maximum acceleration is followed by the maximum deceleration and the return to the oriented speed v0, and the remaining distance S0 after the maximum deceleration until the target stop position.

[0095] according to Figure 8 It can be seen that when the time t4-t1 from the start of positioning control to the maximum acceleration and then the maximum deceleration to return to the directional speed v0 is set to Δt, the distance S1 is expressed by the following equation (7). In addition, the remaining time t2-t4 from the maximum deceleration to the target stop position is expressed by |v0| / a0, so the distance S0 is expressed by the following equation (8).

[0096] [Mathematical formula 6]

[0097]

[0098] [Formula 7]

[0099]

[0100] Therefore, using the above equations (7) and (8), the moving distance S is expressed by the following equation (9): x .

[0101] [Mathematical formula 8]

[0102]

[0103] Furthermore, according to the above-mentioned formula (9), the time Δt from the start of positioning control until the maximum acceleration and then the maximum deceleration to return to the orientation speed v0 is expressed as the following formula (10).

[0104] [Mathematical formula 9]

[0105]

[0106] Based on the above, the process of position instruction (orbit) calculation processing is explained. Fig.10 This is a flowchart showing the procedure of position instruction (orbit) calculation processing.

[0107] In step S101, the current position ( Figure 8 The distance from the positioning control start position at time t1 in the figure to the target stop position is set to S x . Then, proceed to step S102.

[0108] In step S102, the distance S is determined. xIs it greater than the remaining distance S0 for maximum deceleration to the target stop position? As described above, the distance S0 is expressed by the above equation (8). If the determination is yes, the process proceeds to step S104. If the determination is no, the process proceeds to step S103.

[0109] In step S103, the Figure 8 The distance S from the positioning control start position at time t1 to the target stop position x Add 360 (deg). This is because the judgment in step S102 is no, that is, the distance S x The remaining distance S0 for maximum deceleration to the target stop position is smaller than that, and it is impossible to stop at the target position with maximum deceleration. Therefore, an additional movement distance of 1 revolution is added to ensure the movement distance S1 from the start of positioning control to the maximum deceleration after maximum acceleration and return to the directional speed v0. Then, the process returns to step S102 and the distance S is confirmed again. x Whether it is greater than the distance S0, proceed to step S104.

[0110] In step S104, the time Δt from the start of positioning control to the maximum acceleration and then the maximum deceleration and return to the orientation speed v0 is calculated. Specifically, the calculation is performed according to the above formula (10). Then, the process proceeds to step S105.

[0111] In step S105, when time t is between time t1 and time t1+Δt / 2, an acceleration command is calculated to accelerate the rotating axis at the maximum acceleration. In addition, when time t is after time t1+Δt / 2, an acceleration command is calculated to decelerate the rotating axis at the maximum deceleration. Thus, it is possible to achieve maximum acceleration in the first half of the time Δt from the start of positioning control to the maximum deceleration after the maximum acceleration and return to the orientation speed v0, and maximum deceleration in the second half. After that, this process ends.

[0112] Return to Figure 7 In step S11, the rotation axis is brought to the target position and stopped by position control, thereby completing the orientation control process of the present embodiment.

[0113] Next, refer to Figure 11 to Figure 14 , a specific example of the directional control of this embodiment is described by comparing it with the conventional directional control.

[0114] Fig.11 1 is a diagram showing conventional directional control, and is a diagram showing speed changes when the target position is stopped by maximum acceleration followed by maximum deceleration. Fig.12 is a diagram showing the directional control of this embodiment, and is a diagram showing the speed change when stopping at the target position by maximum acceleration followed by maximum deceleration. Fig.131 is a diagram showing conventional directional control, and is a diagram showing speed changes when the vehicle can stop at the target position only by maximum deceleration. Fig.14 is a diagram showing the directional control of this embodiment, and is a diagram showing the speed change when the vehicle can stop at the target position only by the maximum deceleration. Figure 11 to Figure 14 In both cases, speed control is performed from time t0 to time t1 (sequence 1), and positioning control is performed from time t1 to time t2 (sequence 2).

[0115] like Fig.11 and Fig.13 As shown, in the previous directional control, the directional speed v1 and the current speed (initial speed v st ) is small, the acceleration / deceleration detection time t1-t0 is short, so the small acceleration / deceleration a1 in the state where the magnetic flux of the motor 3 is not sufficiently increased, that is, the small acceleration / deceleration a1 in the state where the sufficient torque is not obtained is mistaken as the maximum acceleration / deceleration, and the correct maximum acceleration / deceleration cannot be detected. Therefore, it can be known that the positioning control based on the acceleration instruction of the acceleration / deceleration a1 smaller than the maximum acceleration / deceleration is executed, and the time t2 when reaching the target stop position is slowed down.

[0116] In contrast, Fig.12 and Fig.14 As shown, in the directional control of this embodiment, the directional speed v1 and the current speed (initial speed v st ) is greater than the specified threshold value v th If the initial speed is smaller, change it to the current speed (initial speed v st ) is the specified threshold value v th The above directional speed v2. Thus, the acceleration / deceleration detection time t1-t0 is ensured to be longer than before, and the correct maximum acceleration / deceleration a2 is detected when the magnetic flux of the motor 3 rises sufficiently and a sufficient torque is obtained. Therefore, it can be seen that the positioning control based on the acceleration instruction of the correct maximum acceleration / deceleration a2 is executed, and the time t2 when reaching the target stop position is advanced.

[0117] According to this embodiment, the following effects are achieved.

[0118] In this embodiment, a speed comparison unit 15 is provided, which calculates the difference between the actual speed of the rotating shaft and the speed command; and a speed command calculation unit 16 is provided, which changes the speed command so that the absolute value of the difference becomes greater than the threshold value when the absolute value of the difference is smaller than a predetermined threshold value. In addition, an acceleration command calculation unit 11 is provided, which calculates the acceleration command during the directional control based on the acceleration and deceleration calculated from the actual speed of the rotating shaft when the speed command is changed; and a trajectory calculation unit 12 is provided, which calculates the position command until reaching the target position based on the acceleration command.

[0119] Therefore, when the current speed (initial speed) is close to the directional speed and the difference between the two is small during directional control, the correct acceleration and deceleration can be detected by changing the directional speed in order to ensure sufficient acceleration and deceleration detection time. Therefore, the spindle of the machine tool can be stopped at a specific target position in a shorter time.

[0120] In addition, in the present embodiment, the acceleration / deceleration when accelerating / decelerating with the maximum current that can be given to the motor 3 is calculated, the value of the maximum acceleration / deceleration with the largest magnitude among the calculated acceleration / deceleration is set as the absolute value of the acceleration instruction, and the position instruction for acceleration / deceleration at the maximum acceleration / deceleration is calculated so that the time to reach the target position is the shortest.

[0121] Thus, positioning control to a target stop position can be performed by an acceleration command based on the correct maximum acceleration / deceleration, and thus a spindle of a machine tool or the like can be stopped at a specific target position in a shorter time.

[0122] In addition, in the present embodiment, a configuration is provided to calculate a position command in which the vehicle is accelerated at the maximum acceleration, decelerated at the maximum deceleration, and stopped at the target position.

[0123] Thus, positioning control can be performed to accelerate to a target stop position at the correct maximum acceleration according to an acceleration command based on the correct maximum acceleration / deceleration, so that a spindle of a machine tool or the like can be stopped at a specific target position in the shortest time.

[0124] Next, refer to Fig.15 Modifications of the above-described embodiment will be described.

[0125] Fig.15 1 is a block diagram showing the structure of a control device 2 of a modified example of an embodiment of the present disclosure. In this modified example, the trajectory calculation unit 22 is different from the trajectory calculation unit 12 of the above-mentioned embodiment in that a speed command is calculated instead of a position command until reaching a specific target stop position. That is, the trajectory calculation unit 22 calculates a speed command until reaching a specific target stop position based on an acceleration command of directional control. Therefore, in this modified example, unlike the above-mentioned embodiment, there is no integrator 13 and a position control unit 14.

[0126] According to this modification, the same directional control processing as that of the above-mentioned embodiment is executed, and the same effects as those of the above-mentioned embodiment are achieved.

[0127] In addition, the present disclosure is not limited to the above-mentioned embodiments, and modifications and improvements within the scope that can achieve the purpose of the present disclosure are included in the present disclosure.

[0128] Explanation of symbols

[0129] 1.2 Control device (motor control device)

[0130] 3 Electric motor (induction motor)

[0131] 4 Current Sensor

[0132] 5. Position / speed sensor

[0133] 11, 21 Acceleration command calculation unit

[0134] 12, 22 Orbital Calculation Department

[0135] 13 Integrator

[0136] 14 Position control unit

[0137] 15, 25 Speed ​​comparison unit

[0138] 16, 26 Speed ​​command calculation unit

[0139] 17, 27 Switching section

[0140] 18, 28 Speed ​​control unit

[0141] 19, 29 current control unit.

Claims

1. A motor control device for controlling an induction motor driving a rotating shaft and executing directional control for stopping the rotating shaft at a target position, characterized in that: The motor control device comprises: a speed comparison unit that calculates a difference between an actual speed of the rotating shaft and a speed command; a speed command calculation unit that, when the absolute value of the difference is smaller than a predetermined threshold value, changes the speed command so that the absolute value of the difference becomes greater than or equal to the threshold value; an acceleration command calculation unit that calculates an acceleration command during the directional control based on an acceleration / deceleration calculated from an actual speed of the rotating shaft when the speed command is changed; as well as The trajectory calculation unit calculates at least one of a position command and a speed command until reaching the target position based on the acceleration command.

2. The motor control device according to claim 1, characterized in that: When the actual speed is set to v st , set the speed command to v1, and the threshold to v th When the actual speed v st The absolute value of the difference between the speed command v1 and the threshold value v th When the speed command calculation unit changes the speed command v1 to the speed command v represented by the following formula (1): 21 Or the speed command v expressed by the following formula (2) 22 , [Mathematical formula 1] v 21 = v st -v th Equation (1) v 22 = v st + v th Equation (2).

3. The motor control device according to claim 1 or 2, characterized in that: The acceleration command calculation unit calculates the acceleration / deceleration when the maximum current that can be applied to the induction motor is accelerated / decelerated, and uses the value of the maximum acceleration / deceleration with the largest magnitude among the calculated acceleration / deceleration as the absolute value of the acceleration command. The trajectory calculation unit calculates a position command for performing acceleration and deceleration at the maximum acceleration and deceleration so that a time until reaching the target position is minimized.

4. The motor control device according to claim 3, characterized in that: The trajectory calculation unit calculates a position command for stopping at the target position by accelerating at the maximum acceleration and then decelerating at the maximum deceleration.

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