JP2016189668A - Motor control device, motor control method, sewing machine and program thereof - Google Patents

Abstract

An object of the present invention is to reduce an effective current of a motor by suppressing a useless current that does not contribute to correction of a speed change. A motor control device that drives and controls a servo motor (3) in which a speed change is caused by a periodic load fluctuation includes a speed detection unit (12) that detects a current speed of the servo motor, and a current speed of the servo motor. A speed deviation calculator (13) that generates a command current based on the command current, and a filter circuit (14) that removes a fluctuation component due to load fluctuations included in the command current. Drive control. [Selection] Figure 3

Description

  The present invention relates to a motor control device, a motor control method, a sewing machine, and a program thereof that drive and control a motor coupled to a main shaft of the sewing machine.

  In the load device, since various loads are connected to the output destination of the motor, a speed change occurs due to periodic load fluctuations during one rotation of the motor. Conventionally, a method of detecting a speed change of a motor of a load device and correcting the motor control to reduce the speed change is known (for example, see Patent Documents 1 and 2). In the motor control of Patent Document 1, a change in speed of the motor is suppressed by monitoring a change in speed due to a load and correcting a command value for the motor. In the motor control described in Patent Document 2, sound and vibration on the load device side are suppressed by controlling the rotational speed by correcting the output current to the motor in accordance with the periodic load state.

JP 2006-109544 A JP 2007-295673 A

  In the motor control described in Patent Documents 1 and 2, if a high-performance motor is used, speed change due to load fluctuation can be suppressed, but there is a problem that the cost is high. On the other hand, an inexpensive motor with low performance has a limit in response, and even if the voltage or current is increased, the speed change cannot be suppressed. In this case, although the required output cannot be obtained, the voltage and current are increased for motor control, and excess current is passed to the motor. Therefore, the effective current increases and the power factor of the motor decreases, and the excess current has a problem of affecting the heat generation of the motor.

  The present invention has been made in view of the above points, and provides a motor control device, a motor control method, a sewing machine, and a program for the same that can suppress a useless current that does not contribute to correction of a speed change and reduce an effective current of the motor. The purpose is to provide.

  The motor control device of the present invention is a motor control device that drives and controls a motor in which a speed change is caused by a periodic load fluctuation, and is based on a speed detection unit that detects a current speed of the motor, and a current speed of the motor. A command current generator that generates a command current and a filter circuit that removes a fluctuation component due to load fluctuations included in the command current, and driving the motor with the command current from which the fluctuation component has been removed. Features.

  The motor control method of the present invention is a motor control method for driving and controlling a motor in which a speed change is caused by a periodic load variation, and includes a step of detecting a current speed of the motor and a command based on the current speed of the motor. A step of generating a current; and a step of removing a fluctuation component due to load fluctuations included in the command current, wherein the motor is driven and controlled by the command current from which the fluctuation component has been removed.

  According to these configurations, the fluctuation component due to the load fluctuation is removed from the command current according to the current speed of the motor. If these configurations are applied when an inexpensive motor with a limited response is used, the effective current of the motor is reduced while suppressing unnecessary current that does not contribute to correction of speed change due to load fluctuation. Therefore, it is possible to reduce the energy wasted in the motor and improve the power factor of the motor.

  In the motor control device described above, when a load fluctuation occurs at a cycle of n times during one rotation of the motor, the filter circuit reduces the filter frequency to n times the speed frequency indicating the number of rotations per unit time of the motor. A center frequency is set to remove a fluctuation component due to the load fluctuation from the command current. According to this configuration, the fluctuation component can be easily obtained from the number of load fluctuations that occur during one rotation of the motor, and the center frequency of the filter can be set so as to remove the fluctuation component from the command current.

  In the motor control device, the speed frequency is obtained from a set speed based on a position command for the motor. According to this configuration, the fluctuation component due to load fluctuation can be obtained from the speed frequency according to the position command for the motor. Since the center frequency of the filter is varied according to the position command for the motor, the fluctuation component of the load variation that varies according to the set speed can be appropriately removed.

  In the motor control apparatus, the speed frequency is obtained from the current speed of the motor detected by the speed detector. According to this configuration, the fluctuation component due to the load fluctuation can be obtained from the speed frequency corresponding to the current speed of the motor. Since the center frequency of the filter is varied according to the current speed of the motor, the fluctuation component of the load variation that varies according to the current speed can be appropriately removed.

  A sewing machine according to the present invention includes the motor control device described above and a motor that is driven and controlled by the motor control device. According to this configuration, it is possible to reduce the effective current of the motor used in the sewing machine and improve the power factor of the motor.

  The program of this invention makes a motor control apparatus perform each step of said motor control method. According to this configuration, by installing a program in the motor control device, it is possible to add a function of removing a fluctuation component due to load fluctuation from the command current to the motor control device.

  According to the present invention, by removing the fluctuation component due to load fluctuation from the command current according to the current speed of the motor, it is possible to suppress the useless current that does not contribute to the correction of the speed change and to reduce the effective current of the motor. it can. Therefore, the power factor of the motor can be improved.

It is a block diagram of a motor drive device. It is explanatory drawing of general motor control. It is a control loop figure of a motor control device. It is explanatory drawing of motor control without a filter and with a filter. It is a figure which shows the effective current waveform and speed fluctuation waveform without a filter. It is a figure which shows the effective current waveform and speed fluctuation waveform with a filter.

  Hereinafter, a motor drive device according to the present embodiment will be described with reference to the accompanying drawings. FIG. 1 is a block diagram of a motor drive device. The motor drive device according to the present embodiment is not limited to the configuration shown in FIG. 1 and can be changed as appropriate. Hereinafter, the motor control device of the sewing machine will be described, but the description of the detailed configuration of the sewing machine will be omitted.

  As shown in FIG. 1, the motor drive device includes a rectifier 2 that converts alternating current from a three-phase alternating current or single-phase alternating current main power source 1 into direct current, and direct current from the rectifier 2 into alternating current to convert a servo motor (motor ) 3 and an inverter bridge circuit 4 that outputs to 3 and a motor control device 5 that performs PWM control on the inverter bridge circuit 4. A smoothing capacitor 6 that smoothes the output (DC voltage) of the rectifier 2 is connected to the rectifier 2 in parallel. The rectifier 2 and the smoothing capacitor 6 constitute a main power supply circuit unit 7. The inverter bridge circuit 4 includes half-phase circuits 8u-8w for three phases connected in parallel to the output terminal of the rectifier 2.

  In the U-phase half-bridge circuit 8u, a pair of switching elements T1 and T4 are connected in series, and free-wheeling diodes D1 and D4 are connected in parallel to the switching elements T1 and T4, respectively. Similarly, in the V-phase half-bridge circuit 8v, a pair of switching elements T2 and T5 are connected in series, and free-wheeling diodes D2 and D5 are connected in parallel to the switching elements T2 and T5, respectively. In the W-phase half-bridge circuit 8w, a pair of switching elements T3 and T6 are connected in series, and free-wheeling diodes D3 and D6 are connected in parallel to the switching elements T3 and T6, respectively.

  The connection points of the U-phase switching elements T1 and T4, the connection points of the V-phase switching elements T2 and T5, and the connection points of the W-phase switching elements T3 and T6 are respectively three-phases (not shown) of the servo motor 3. They are connected to each other via exciting coils and resistors. A PWM signal is input from the motor control device 5 to the three-phase half-bridge circuits 8u-8w. An input line from the motor control device 5 is connected to the gates of the switching elements T1 to T6, and a PWM signal is applied from the motor control device 5 to the switching elements T1 to T6, so that the ON state and the OFF state are switched. .

  By turning on and off the switching elements T1 to T6, the direct current is converted into the alternating current, and the power supply necessary for the servo motor 3 is controlled. Between the connection point of the U-phase switching elements T1, T4 and the connection point of the W-phase switching elements T3, T6 and each terminal of the motor 4A, a current sensor 9u that feeds back each phase current to the motor control device 5, 9w is provided. The servo motor 3 is provided with an encoder 10 that detects the position and speed of the servo motor 3. The position and speed detected by the encoder 10 are output to the motor control device 5, and the servo motor 3 is servo-controlled by the motor control device 5.

  The switching elements T1 to T6 are not limited to power transistors, but may be IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), and bipolar transistors. The free-wheeling diodes D1 to D6 may be elements that constitute a path for the regenerative current, and a parasitic diode built in the power transistor can also be used. Further, here, the configuration in which the current sensor 9 detects currents of two phases Iu and Iw is illustrated, but the current sensor 9 may detect currents of three phases Iu, Iv, and Iw.

  In the sewing machine according to the present embodiment, description of the detailed configuration of each part of the sewing machine is omitted. For example, as a transmission mechanism, a main shaft, a needle bar crank rod, a balance, a balance crank, a large pendulum shaft crank rod, It has a normal sewing machine configuration such as a pendulum shaft and a lower shaft.

  The motor driving device configured as described above is used for controlling a servo motor 3 connected to a main shaft of a sewing machine (not shown) as a load device. In this case, a transmission mechanism that converts the rotation of the servo motor 3 into various motions and transmits it is connected to the main shaft of the sewing machine, and this transmission mechanism is a load on the servo motor 3. When the main shaft of the sewing machine is moved by the servo motor 3, the inertia of the load connected to the main shaft changes when viewed from the servo motor 3. For this reason, the rotational speed changes due to a periodic load fluctuation during one rotation of the servo motor 3.

  Originally, it is preferable to control the current flowing through the servomotor 3 so as to cancel the speed change due to the load fluctuation. However, the servo motor 3 with low performance has a limit in the responsiveness of current control, and even if the current is controlled by increasing / decreasing the gain (position gain, speed gain), the speed change cannot be sufficiently suppressed. When some speed change due to load fluctuation does not become a problem, a current for canceling the speed change flows through the servo motor 3 even though the function as a sewing machine is not affected. For this reason, useless current that does not contribute to the correction of the speed change flows to the servo motor 3 and the effective current increases.

  Here, with reference to FIG. 2, gain adjustment and speed change of the current speed when using a servo motor with low performance will be briefly described. FIG. 2 is an explanatory diagram of general motor control. In FIG. 2, the current speed is indicated by a solid line, the command speed is indicated by a broken line, and the command current is indicated by a one-dot chain line.

  As shown in FIG. 2A, in the servo motor 3 (see FIG. 1) having low performance, it is possible to suppress overshoot during acceleration by increasing the gain and increase power (penetration force of the sewing machine). However, no matter how much the gain is increased, the responsiveness of the servo motor 3 is limited, and the speed change of the current speed due to load fluctuation cannot be suppressed. Although the speed change of the servo motor 3 is not corrected, the amplitude of the command current is large, and an excess current flows through the servo motor 3 to reduce the power factor, which affects the heat generation of the motor. For this reason, when the speed change due to the load fluctuation does not become a problem, it is conceivable that the responsiveness is lowered so that the servo motor 3 does not follow the speed change.

  In this case, as shown in FIG. 2B, the follow-up of the servo motor 3 with respect to the load fluctuation can be suppressed by lowering the gain and reducing the responsiveness. As a result, the amplitude of the command current is reduced, the current flowing through the servo motor 3 is reduced, and the power factor can be improved. However, when the gain is lowered, there is a problem that overshoot at the time of acceleration cannot be suppressed, and further, target power (penetrating force of the sewing machine) cannot be obtained. Thus, if the gain is increased, the power factor decreases, and if the gain is decreased, problems such as overshoot occur. Therefore, the servo motor 3 cannot be appropriately controlled only by gain adjustment.

  Therefore, in the present embodiment, the fluctuation component due to load fluctuations included in the command current is removed by a filter to reduce the amplitude of the command current. As a result, the servo motor 3 can be prevented from following the load fluctuation without lowering the gain. Therefore, it is possible to improve the power factor of the servo motor 3 by eliminating a wasteful current that does not contribute to the correction of the speed change due to the load fluctuation and reducing the effective current. Furthermore, since the amplitude of the command current is small even when the gain is increased, it is possible to suppress overshoot during acceleration and to obtain target power.

  Hereinafter, the control loop of the motor control device will be described with reference to FIG. FIG. 3 is a control loop diagram of the motor control device. The control loop of the motor control device is not limited to the configuration shown in FIG. 3 as long as it has a configuration in which the fluctuation component due to load fluctuation is removed from the command current by the filter circuit.

  As shown in FIG. 3, in the subtraction element e1, the current position of the servo motor 3 fed back from the encoder 10 and the target position command are subtracted to calculate a position deviation. The position deviation is multiplied by the position gain by the position deviation calculator 11 and output to the subtraction element e2 as a speed command. In the subtraction element e2, the current speed of the servo motor 3 fed back from the encoder 10 and the speed command from the position deviation calculator 11 are subtracted to calculate a speed deviation. The current speed of the servo motor 3 is detected by the speed detector 12 by dividing the difference between the current position of the servo motor 3 in the control loop and the position one cycle before by the calculation period of the control loop (the current speed is calculated). Step to detect).

  The speed deviation is multiplied by the speed gain by the speed deviation calculator 13 and output to the filter circuit 14 as a command current (torque command) (step of generating a command current). That is, the speed deviation calculator 13 functions as a command current generator that generates a command current from the current speed of the servo motor 3. In the filter circuit 14, the fluctuation component due to the load fluctuation included in the torque command is removed by the filter (step of removing the fluctuation component). The center frequency of the filter is calculated by the frequency calculator 16 based on the set speed obtained by differentiating the position command by the differentiator 15. In the filter circuit 14, a filter is set at the center frequency calculated by the frequency calculator 16.

Specifically, first, the speed frequency is obtained from the set speed of the servo motor 3. When the speed frequency is f ₀ [Hz] and the set speed is N [rpm], the speed frequency f ₀ is obtained as shown in the equation (1). Thereby, the rotation speed (frequency) of the servo motor 3 per unit time is obtained.
(1)
f ₀ = N / 60

Next, the center frequency of the filter is obtained from the speed frequency of the servo motor 3 and the number of times the load fluctuates during one rotation of the servo motor 3. When the center frequency is f ₁ [Hz] and the number of load fluctuations during one rotation of the servo motor 3 is n, the center frequency f ₁ is obtained as shown in Expression (2). Thereby, the load fluctuation number (frequency) of the servo motor 3 per unit time is obtained.
(2)
f ₁ = n · f ₀

  In this way, when load fluctuation occurs in one cycle during one rotation of the servo motor 3, n times the speed frequency of the servo motor is set in the filter circuit 14 as the center frequency of the filter. Thereby, the center frequency of the filter is adjusted to the fluctuation frequency of the load fluctuation, and the fluctuation component due to the load fluctuation is removed from the command current. Note that a notch filter having a narrow removal band is used as the filter, and only the band of fluctuation components due to load fluctuations from the command current is attenuated to a low level. Further, since the center frequency of the filter is varied according to the position command for the servo motor 3, the fluctuation component that varies according to the set speed can be appropriately removed.

  The filtered command current is output from the filter circuit 14 to the subtraction element e3. In the subtraction element e3, a current deviation (torque deviation) is calculated by subtracting the current detected by the current sensor 9 and the command current from the filter circuit 14. The current deviation is multiplied by the current gain by the current deviation calculator 17 and output to the current amplifier 18. Then, a PWM signal is generated by the current amplifier 18 and a motor current is output to the servomotor 3 through the inverter bridge circuit 4 (see FIG. 1). The servo control for the servo motor 3 is performed by repeating the above operation.

  The motor control device 5 includes a processor that executes various processes, a memory, and the like. The memory is composed of one or a plurality of storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application, and a program for executing motor control is stored in the motor control device 1. ing.

  Next, with reference to FIG. 4 to FIG. 6, speed fluctuations of the motor control device without a filter and the motor control device with a filter will be described. FIG. 4 is an explanatory diagram of motor control without a filter and with a filter. FIG. 5 shows an effective current waveform and a speed fluctuation waveform without a filter. FIG. 6 shows an effective current waveform and a speed fluctuation waveform with a filter. In FIG. 4, the current speed is indicated by a solid line, the command speed is indicated by a broken line, the command current is indicated by a one-dot chain line, and the U-phase current is indicated by a two-dot chain line. 5 and 6, the speed fluctuation waveform is indicated by a solid line, the U-phase current is indicated by a one-dot chain line, the W-phase current is indicated by a two-dot chain line, and the Z-phase signal (encoder signal) is indicated by a broken line. 5 and 6, the V-phase current is omitted for convenience of explanation.

  As shown in FIG. 4A, in the motor control without a filter, the command current changes so as to suppress the speed change of the load fluctuation, so the amplitude of the command current is large. On the other hand, as shown in FIG. 4B, in the motor control with a filter, since the fluctuation component due to load fluctuation is removed from the command current by the filter, the amplitude of the command current is small. Therefore, the effective current of the servo motor 3 (see FIG. 3) can be reduced by reducing the amplitude of the command current without adjusting the gain. Further, since there is no need to change the gain, problems such as overshoot do not occur.

  Subsequently, a filter setting example will be described. As shown in FIG. 5A, when the servo motor 3 (see FIG. 3) is driven without providing a filter, two cycles of speed fluctuation occur during one high / low period of the Z-phase signal. This indicates that the load fluctuation occurs twice while the servo motor 3 rotates once. Therefore, when the set speed is 2800 [rpm], 93 [Hz] is obtained as the fluctuation frequency of the load fluctuation from the above formulas (1) and (2). A current is passed through the servo motor 3 so as to cancel the load fluctuation, but the speed fluctuation is not sufficiently suppressed because the response of the servo motor 3 is limited.

  As shown in FIG. 5B and FIG. 5C, when the set speed is 2000 [rpm] and 1500 [rpm], the above formulas (1) and (2) to 67 [Hz] and 50 [Hz] are respectively loaded. It is obtained as the fluctuation frequency of fluctuation. A current is passed through the servo motor 3 so as to cancel the load fluctuation, but the speed fluctuation is not sufficiently suppressed because the response of the servo motor 3 is limited. Thus, in the case of no filter, the amplitudes of the U-phase current and the W-phase current are increased by the amount of excess current caused by load fluctuations to the servo motor 3, and the effective current of the servo motor 3 is increased. To increase.

  As shown in FIG. 6A, in the servo motor 3 provided with a filter (see FIG. 3), when the set speed is 2800 [rpm], the center frequency of the filter is adjusted to 93 [Hz] which is the fluctuation frequency of the load fluctuation. It is done. As a result, the fluctuation component due to the load fluctuation is removed from the command current, so that a current that cancels the load fluctuation is prevented from flowing to the servo motor 3. Similarly, as shown in FIGS. 6B and 6C, when the set speed is 2000 [rpm] and 1500 [rpm], the center frequency of the filter is adjusted to 67 [Hz] and 50 [Hz], respectively. The fluctuation component due to load fluctuation is removed from the current.

  In this way, when the filter is present, no excess current due to load fluctuations flows to the servo motor 3, so the amplitudes of the U-phase current and the W-phase current are reduced and the effective current is reduced. . Therefore, when a slight speed change due to load fluctuation does not become a problem, the cost can be reduced by using the servo motor 3 having low performance.

表１に示すように、いずれの設定速度においても、フィルタ有りのモータ制御では、フィルタ無しのモータ制御よりも速度リップルが小さく、実効電流が低下することが確認された。 Here, when the inventors measured effective current [A] and speed ripple [rpm] of motor control without a filter and motor control without a filter, the results shown in Table 1 were obtained.

As shown in Table 1, at any set speed, it was confirmed that the motor control with a filter has a smaller speed ripple and the effective current is lower than the motor control without a filter.

  As described above, the motor control device according to the present embodiment removes the fluctuation component due to the load fluctuation from the command current according to the current speed of the servo motor. As a result, no excessive current flows to the servo motor so as to cancel the speed change due to the load fluctuation. When an inexpensive servo motor with a limited response is used, an unnecessary current that does not contribute to the correction of the speed change is suppressed, and the effective current of the servo motor is reduced. Therefore, it is possible to reduce the energy consumed unnecessarily by the servo motor and improve the power factor of the servo motor.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the present embodiment, the motor control device used in the sewing machine has been described as an example, but the present invention is not limited to this configuration. The motor control device may be used for other load devices such as a mounter and a printer as long as the motor control device is configured to be used for a load device in which periodic load fluctuations occur.

  Further, in the present embodiment, the filter circuit 14 is configured to remove the fluctuation component due to the load variation from the command current (torque command) output from the speed deviation calculator 13, but the present invention is not limited to this configuration. The command current is a concept including a current deviation (torque deviation), and the filter circuit 14 may be configured to remove a fluctuation component due to load fluctuation from the current deviation. Therefore, the filter circuit 14 may be provided between the subtraction element e3 and the current deviation calculator 17, and between the current deviation calculator 17 and the current amplifier 18, for example, in FIG.

  In the present embodiment, the servo motor 3 is exemplified as the motor. However, the present invention is not limited to this configuration. The motor may be a motor capable of current control, for example, a stepping motor.

  In this embodiment, the control loop has a plurality of feedback loops as shown in FIG. 3, but is not limited to this configuration. The control loop may be configured in any way as long as it includes a feedback loop.

  In the present embodiment, the speed detection unit 12 obtains the current position of the servo motor 3 and the previous position from the encoder 10 from the encoder 10 and calculates the current speed of the servo motor 3. It is not limited. The speed detection unit 12 is not limited to the configuration that detects the current speed of the servo motor 3 by the calculation process, and may be configured to detect the current speed of the servo motor 3 directly by a speed sensor or the like.

  In the present embodiment, the filter circuit 14 is configured to remove the fluctuation component from the command current using a single filter, but may be configured to remove the fluctuation component from the command current using a plurality of filters.

  In the present embodiment, the speed frequency is obtained from the set speed of the servo motor 3, but the present invention is not limited to this structure. The speed frequency may be obtained from the current speed of the servo motor 3 detected by the speed detector 12. In this case, the frequency calculator 16 calculates the center frequency of the filter from the current speed of the servo motor 3.

  As described above, the present invention has an effect of reducing the effective current of the motor by suppressing a useless current that does not contribute to the correction of the speed change, and in particular, the motor connected to the main shaft of the sewing machine. The present invention is useful for a motor control device that controls driving, a motor control method, and a program thereof.

1 Main power supply 2 Rectifier 3 Servo motor (motor)
4 Inverter Bridge Circuit 5 Motor Controller 6 Smoothing Capacitor 7 Main Power Supply Circuit Unit 8 Half Bridge Circuit 9 Current Sensor 10 Encoder 11 Position Deviation Calculator 12 Speed Detection Unit 13 Speed Deviation Calculator (Command Current Generator)
14 Filter circuit 15 Differentiator 16 Frequency calculator 17 Current deviation calculator 18 Current amplifier

Claims (7)

A motor control device that drives and controls a motor in which a speed change is caused by a periodic load fluctuation,
A speed detector for detecting a current speed of the motor;
A command current generator for generating a command current based on the current speed of the motor;
A filter circuit for removing fluctuation components due to load fluctuations included in the command current,
A motor control apparatus, wherein the motor is driven and controlled by a command current from which a fluctuation component due to the load fluctuation is removed.   When load fluctuation occurs in n cycles during one rotation of the motor, the filter circuit sets the center frequency of the filter to n times the speed frequency indicating the number of rotations per unit time of the motor, and The motor control device according to claim 1, wherein a fluctuation component due to load fluctuation is removed from the command current.   The motor control device according to claim 2, wherein the speed frequency is obtained from a set speed based on a position command for the motor.   The motor control device according to claim 2, wherein the speed frequency is obtained from a current speed of the motor detected by the speed detection unit. The motor control device according to any one of claims 1 to 4,
A sewing machine comprising: a motor driven and controlled by the motor control device. A motor control method for driving and controlling a motor in which a speed change is caused by a periodic load fluctuation,
Detecting a current speed of the motor;
Generating a command current based on the current speed of the motor;
Removing fluctuation components due to load fluctuations included in the command current,
A motor control method, wherein the motor is driven and controlled by a command current from which a fluctuation component due to the load fluctuation is removed.   A program for causing a motor control device to execute each step of the motor control method according to claim 6.

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