Servo motor control system for controlling a servo motor

Abstract

Servo motor control system (1000) for controlling a drive axis servo motor (105) that drives an axis (8) of an industrial machine or machine tool, comprising: - a rectifier (2) which is configured to convert alternating current energy from an alternating current supply (4) into direct current energy and to output the direct current energy to a direct current intermediate circuit, - a first inverter (103) which is connected to the DC intermediate circuit and is configured to perform an energy conversion between the DC energy in the DC intermediate circuit and the AC energy or regenerative energy of the drive axis servomotor (105) used as drive energy, - a flywheel (7), - a flywheel servo motor (5-1) connected to the flywheel (7) and configured to rotate the flywheel (7), - a second inverter (3-1) connected to the DC link and configured to perform an energy conversion between the DC energy in the DC link and the AC energy or regenerative energy of the flywheel servomotor (5-1) used as drive energy, and - a servo motor control device (1) configured to control the flywheel servo motor (5-1), - comprising the servo motor control device (1): - a storage unit (11) configured to store a predefined torque constant for the servo motor (5), - a torque constant correction unit (12) configured to correct the torque constant stored in the storage unit (11) when magnetic saturation occurs in a winding of the servo motor (5), and - a power calculation unit (13) configured to calculate a power of the servo motor (5) based on the torque constant stored in the storage unit (11) or the torque constant calculated after correction by the torque constant correction unit (12), a value associated with a current of the servo motor (5) and a value associated with a speed of the servo motor (5), and - wherein the energy conversion by the second inverter (3-1) is controlled such that the alternating current energy regenerated by the flywheel servomotor (5-1) is converted into direct current energy or the direct current energy in the DC intermediate circuit is converted into alternating current energy to drive the flywheel servomotor (5-1) according to a power of the drive axle servomotor (105) and a power of the flywheel servomotor (5-1) which are calculated by the power calculation unit (13).

Description

Background of the invention 1. Field of the invention

[0001] The present invention relates to a servo motor control system for controlling a servo motor. 2. Description of the relevant state of the art

[0002] In a servo motor control device for driving and controlling a servo motor in a machine tool or industrial machine, such as a forming machine, a molding machine or a robot, alternating current energy from an alternating current supply is temporarily converted into direct current energy, the direct current energy is again converted into alternating current energy and the alternating current energy is used as drive energy for the servo motor provided for each drive axis.The servo motor control device comprises a rectifier that converts alternating current energy supplied by the alternating current supply into direct current energy and outputs the direct current energy, and an inverter that is connected to a DC intermediate circuit on the DC side of the rectifier and performs an energy conversion between the direct current energy in the DC intermediate circuit and the alternating current energy or regenerative energy used as drive energy of the motor, wherein the servo motor control device controls the speed, torque or rotor position of the servo motor that is connected to the AC output side of the inverter.

[0003] Since the motor has high energy consumption during acceleration, high AC energy can preferably be supplied by a power supply device on the AC supply side. Therefore, the power supply device on the AC supply side is preferably capable of supplying a peak value of AC energy required for the power supply. For this reason, to avoid a situation where the capacity of the power supply device on the AC supply side is insufficient for the peak energy value, the motor is preferably operated under a lower operating condition to reduce the motor's energy consumption, or the power supply device is preferably designed with a peak energy range.However, operating the motor according to the lower operating condition is inefficient and not preferred, as implementing the power supply device with such a range leads to higher costs and a larger installation space.

[0004] Therefore, as disclosed, for example, in the unexamined Japanese patent publication (Kokai) JP 2017 - 17 931 A, a technique was employed in which the peak energy demand for the power supply device on the AC supply side is reduced by providing an energy storage device in a DC link connecting a rectifier and an inverter. In this technique, energy is supplied or stored via the DC link by the energy storage device according to the energy consumption and energy regeneration of the servo motor in order to reduce the peak energy demand for the power supply device on the AC supply side.

[0005] For example, the average energy consumption of a press driven by a servo motor is lower than that of a press that uses hydraulic pressure as a drive source, even though the maximum energy consumption incurred when performing a pressing operation is considerable and can lead to a problem where the capacity of the power supply device on the AC supply side is insufficient.In the servomotor control device of such a press machine, the peak energy value for the power supply device on the AC supply side can be reduced by providing an energy storage device for supplying and storing energy, calculating the energy consumed during the operation of the press machine and, as a result of the calculation, supplying energy from the energy storage device when the press machine consumes energy, or causing the energy storage device to consume energy when the press machine regenerates energy.

[0006] US 4 661 756 A describes a method for driving a motor with a required torque and for calculating a current based on a torque requirement.

[0007] JP H08 - 275 599 A describes a motor that can precisely control torque. Current is calculated based on a torque command and the relationship between current and torque.

[0008] DE 697 27 018 T2 discloses magnetic saturation at high currents, proposes a method for correcting the rotor phase for saturation correction.

[0009] The publication, RP Deodhar, DA Staton and TJE Miller, “Variation of torque constant with armature current in brushless PM motors,”, 1995 Seventh International conference on Electrical Machines and Drives (Conf. Publ. No. 412), 1995, pp. 405-409, describes the variation of the torque constant in a brushless PM motor.

[0010] DE 10 2006 033 562 B3 discloses a flywheel for supplying energy to a DC intermediate circuit or for storing energy from a DC intermediate circuit. Summary of the invention

[0011] When the current flowing through a servo motor winding increases, the magnetic flux generated in the winding also increases. The maximum magnetic flux density is determined by the core material, winding shape, and number of turns. When the magnetic flux density exceeds its maximum value, the winding enters a state of magnetic saturation. The relationship between the current flowing through the servo motor winding and the generated torque is linear in a state where magnetic saturation does not occur, with the torque increasing linearly as the current through the winding increases. However, as the current continues to increase and magnetic saturation occurs, the generated torque does not increase linearly, and the torque constant, which is the rate of increase in torque, gradually decreases.The torque is determined based on the torque constant and the current flowing through the winding, whereas the servo motor's power is determined based on its speed and torque. Since the torque does not increase linearly and the torque constant decreases when the winding is in a magnetic saturation state, the actual power of the servo motor is lower compared to a case where the power is calculated without considering the decrease in the torque constant (i.e., without taking magnetic saturation into account). In other words, calculating the servo motor's power without considering the decrease in the torque constant due to magnetic saturation lacks accuracy.

[0012] In a servo motor control device for controlling a drive axis servo motor that drives an axis of an industrial machine or machine tool, an energy storage device for reducing peak energy levels for a power supply device on the AC supply side can be implemented, for example, with a flywheel and a flywheel servo motor driving the flywheel. Depending on the energy state of the drive axis servo motor, the electrical energy supplied to or consumed (stored) by the energy storage device is determined by the power output of the flywheel servo motor in the energy storage device. Therefore, to control the power output of the flywheel servo motor, its power is preferably calculated precisely.

[0013] As described above, in an area where a servo motor is used, the power output of the servo motor is preferably calculated with a high degree of accuracy.

[0014] One aspect of the present disclosure relates to a servo motor control system provided in claim 1 for controlling a servo motor. Brief description of the drawings

[0015] The present invention will become more fully apparent with reference to the following accompanying drawings. Fig. Figure 1 is a block diagram of a servo motor control device according to one embodiment. Fig. Figure 2A is a diagram describing a correction of a torque constant by a torque constant correction unit and schematically shows a relationship between a current flowing through a winding of a servo motor and a torque generated in the servo motor. Fig. Figure 2B is a diagram describing a correction of a torque constant by a torque constant correction unit and schematically shows a relationship between the current flowing through the winding of the servo motor and the torque constant of the servo motor. Fig. Figure 3 is a block diagram of a servo motor control device of the first form. Fig. Figure 4 is a block diagram of a servo motor control device of a second form. Fig. Figure 5 is a flowchart showing an operating sequence of the servo motor control device according to one embodiment. Fig. Figure 6 is a block diagram of a servo motor control system, which includes the servo motor control device of the first form. Fig. Figure 7 is a block diagram of a servo motor control system that includes the servo motor control device of the second form. Fig. Figure 8 is a flowchart showing the operating sequence of a servo motor control system comprising the servo motor control device according to one embodiment. Detailed description

[0016] A servo motor control device for controlling a servo motor and a servo motor control system comprising this device are described below with reference to the drawings. In each drawing, similar elements are designated by similar reference numerals. The same reference numerals in different drawings denote components with the same functions. For ease of understanding, these drawings may use different scales.

[0017] Fig. Figure 1 is a block diagram of a servo motor control device according to one embodiment. As an example, a case is described here in which a servo motor 5 is controlled by a servo motor control device 1. In the embodiments described below, an AC power supply 4 has three phases, and the servo motor 5 also has three phases, although the number of phases does not specifically restrict the present embodiment and the number of phases can include a single phase. The type of servo motor 5 controlled by the servo motor control device 1 does not specifically restrict the present embodiment and can, for example, be an asynchronous motor or a synchronous motor.

[0018] Before describing the servo motor control device 1 according to one embodiment, a main circuit system for supplying drive energy to the servo motor 5 is described as follows. Alternating current energy for driving the servo motor 5 is supplied by an inverter 3. The inverter 3 is connected to a DC link on its DC input side and performs an energy conversion between the DC energy in the DC link and the AC energy or regenerative energy used as drive energy for the servo motor 5 controlled by the servo motor control device 1. The DC link, which connects the DC output side of a rectifier 2 and the DC input side of the inverter 3, is equipped with a DC link capacitor 6 (also referred to as a smoothing capacitor).The DC link capacitor 6 serves to store DC energy in the DC link and also to suppress a pulsating component of the DC output of the rectifier 2. The rectifier 2 converts AC energy from the AC power supply 4 into DC energy and outputs the DC energy to the DC link on the DC output side.

[0019] Next, a control system comprising the servo motor control device 1 according to one embodiment is described.

[0020] Similar to a conventional servo motor control device, the servo motor control device 1 comprises a motor control unit 30, a current sensing unit 21, and a speed sensing unit 22, and controls the inverter 3, which performs the energy conversion between the DC energy in the DC link and the AC energy or renewable energy used as drive energy for the servo motor 5. The motor control unit 30 comprises a current command generation unit 31 and a speed command generation unit 32. The speed command generation unit 32 generates a speed command for the servo motor 5 based on the (rotor) speed of the servo motor 5 detected by the speed sensing unit 22 (speed feedback) and an operating program of the servo motor 5, and the like.The current command generation unit 31 generates a current command to control the speed, torque, or rotor position of the servomotor 5 based on the current flowing through the winding of the servomotor 5, which is detected by the current sensing unit 21 (current feedback), and a speed command input from the speed command generation unit 32. The energy conversion by the inverter 3 is controlled based on the current command generated by the motor control unit 30 (in other words, based on a switching command generated in response to the current command). The configuration of the motor control unit 30 described here is merely an example; the configuration of the motor control unit 30, including designations such as position command generation unit, torque command generation unit, and switching command generation unit, can be defined as desired.

[0021] The servo motor control device 1 according to one embodiment comprises a storage unit 11, a torque constant correction unit 12, a power calculation unit 13 and a magnetic saturation determination unit 14.

[0022] The memory unit 11 stores a predefined torque constant for the servomotor 5. The torque constant is typically specified as part of the servomotor 5's specifications and is described, for example, in a specification table or an operator's manual for the servomotor 5. The present embodiment does not restrict a method for writing the torque constant to the memory unit 11 itself, wherein the method for writing the torque constant to the memory unit 11 is provided, for example, by an operator input via a numerical control device (not shown) connected to the servomotor control device 1.The memory unit 11 can be implemented using non-volatile memory that can be electrically erased and written, such as an EEPROM (registered trademark), or random-access memory (RAM) that can be read and written at high speed, such as a DRAM or SRAM. The memory unit 11 can also store motor-specific information relating to the servomotor 5 other than the torque constant. This motor-specific information includes, for example, information specifying the servomotor 5, such as its type, specifications, revision number, batch number, or serial number; a call number for a motor control parameter; a counter-electromotive force constant; and the inductance and resistance of the servomotor 5.

[0023] The magnetic saturation detection unit 14 determines whether magnetic saturation has occurred in the winding of the servomotor 5. More precisely, the magnetic saturation detection unit 14 determines that magnetic saturation has occurred in the winding of the servomotor 5 when a value associated with the current of the servomotor 5 exceeds a predetermined current threshold. Generally, magnetic saturation occurs when a current flowing through the winding of the servomotor 5 exceeds a rated current. Therefore, in one embodiment, a current threshold for determining magnetic saturation in the magnetic saturation detection unit 14 is set to a value corresponding to the rated current of the servomotor 5. Alternatively, the current threshold can be set to a value close to the rated current of the servomotor 5.“A value associated with the current of servomotor 5” is either a value of the current flowing through the winding of servomotor 5, which is detected by the current sensing unit 21, or a current command generated by the current command generation unit 31. Therefore, “a value corresponding to the rated current of servomotor 5” is specified either by the value of the rated current of servomotor 5 or by the current command corresponding to the rated current.

[0024] The torque constant correction unit 12 corrects the torque constant stored in the storage unit 11 when magnetic saturation occurs in the winding of the servo motor 5, i.e., when the magnetic saturation detection unit 14 determines that magnetic saturation has occurred in the winding of the servo motor. If magnetic saturation has occurred in the winding of the servo motor 5, the corrected torque constant is sent to the power calculation unit 13 (described later) and used to calculate the power of the servo motor 5. Conversely, if the magnetic saturation detection unit 14 does not determine that magnetic saturation has occurred in the winding of the servo motor, the torque constant stored in the storage unit 11 is not corrected and is used as is by the power calculation unit 13 to calculate the power of the servo motor 5.If magnetic saturation has occurred in the winding of the servo motor 5, the torque constant correction unit 12, in one embodiment, corrects the torque constant stored in the storage unit 11 such that the torque constant decreases as the value associated with the servo motor current increases. In this case, the torque constant calculated by the torque constant correction unit 12 after the correction is expressed by a linear function, where, for example, the value associated with the servo motor 5 current is an independent variable and the torque constant decreases as the value associated with the servo motor current increases. The process described above is further detailed in the following reference. Fig. 2A and Fig. 2B described in more detail.

[0025] Fig. Figure 2A is a diagram describing a correction of a torque constant by a torque constant correction unit and schematically shows a relationship between a current flowing through a winding of a servo motor and a torque generated in the servo motor. Fig. Figure 2B is a diagram describing a correction of the torque constant by the torque constant correction unit and schematically shows a relationship between the current flowing through the winding of the servo motor and the torque constant of the servo motor. Fig. 2A shows a thick solid line indicating a measured actual torque, while a thick dashed line indicates a torque obtained by calculation with a fixed torque constant, without considering magnetic saturation. Fig. 2B shows a thick solid line indicating an actual torque constant, while a thick dashed line indicates the torque constant without considering magnetic saturation.

[0026] The inventor of the present invention observed a relationship between the current flowing through the winding of the servomotor 5 and the generated torque in an experiment to determine that, in a range where the current flowing through the winding of the servomotor 5 exceeds a rated current, the torque can be approximated by a quadratic function where the current is an independent variable. In a range without magnetic saturation, the magnetic flux generated in the winding increases, and the torque increases linearly as the current flowing through the winding of the servomotor 5 is higher, as shown in Fig. Figure 2A shows that if the current flowing through the winding of servomotor 5 continues to increase and exceeds a rated current I1, magnetic saturation occurs. In a region of magnetic saturation, the generated torque deviates from a linear increase, and the rate of increase is slower compared to the torque obtained by calculating the torque constant without considering magnetic saturation. The torque is calculated based on the torque constant and the current flowing through the winding, and the slow rate of increase of the torque, which deviates from a linear increase, indicates a decrease in the torque constant.In other words, in a region without magnetic saturation, where the current flowing through the winding of servomotor 5 is between zero and the rated current I1, the torque increases linearly, reaching the rated torque T1 when the current flowing through servomotor 5 is the rated current I1. In a region with magnetic saturation, where the current flowing through the winding of servomotor 5 exceeds the rated current I1, the generated torque is expressed by a quadratic function, where the current is an independent variable. When the current flowing through the winding of servomotor 5 is the maximum current I2, the torque reaches the maximum torque T2.

[0027] To keep the description brief, it is assumed that Fig. 2A, which represents the relationship between the current and the torque, is a two-dimensional xy-plane, where the current and torque are x and y respectively, and the torque y is expressed by equation 1, where the rated current I1 is a, the rated torque T1 is b, the maximum current I2 is c, and the maximum torque T2 is d. y={ bax(0≤x≤a)bax−bc−ada(c−a)2(x−a)2(a <x≤c)

[0028] As shown in Equation 1, in a region without magnetic saturation where x is at least zero and not more than a, the torque y is expressed by a linear function of x with a slope of "b / a", and in a region with magnetic saturation where x is more than a but not more than c, the torque y is expressed by a quadratic function with a slope of "b / a", where the slope of the line of tangency at a point (a, b) is "b / a" and passes through a point (c, d).

[0029] When equation 1 is differentiated with respect to the current x, a torque constant y' is obtained, as shown in equation 2. y={ bax(0≤x≤a)bax−bc−ada(c−a)2(x−a)2(a <x≤c)

[0030] As shown in Equation 2, in a region without magnetic saturation where x is at least zero and not more than a, the torque constant y' is expressed by a constant "b / a", and in a region with magnetic saturation where x is more than a but not more than c, the constant y' is expressed by a linear function of x. In other words, it is understood that the actual torque constant decreases linearly in a magnetic saturation state compared to the torque constant without regard to magnetic saturation.

[0031] Therefore, in one embodiment, the torque constant correction unit 12 is configured to correct the torque constant stored in the storage unit 11 according to a linear function when magnetic saturation occurs in the winding of the servo motor 5. In this linear function, the value associated with the current of the servo motor 5 is an independent variable, and the torque constant decreases as the value associated with the current of the servo motor 5 increases. In other words, when magnetic saturation occurs in the winding of the servo motor 5, the torque constant obtained by the correction through the torque constant correction unit 12 decreases according to a linear function where the value associated with the current of the servo motor 5 is a variable.

[0032] The nominal current I1 (a in Fig. 2A and Fig. 2B), the rated torque T1 (b in Fig. 2A and Fig. 2B), the maximum current I2 (c in Fig. 2A and Fig. 2B) and the maximum torque T2 (d in Fig. 2A and Fig. 2B) are usually given as specifications of servomotor 5, and these parameters are easily obtainable, as they are given, for example, in a specification table or an operator's manual for servomotor 5. By substituting these parameters into equation 2, both torque constants can be calculated in a state without magnetic saturation and in a state with magnetic saturation.The rated current I1, the rated torque T1, the maximum current I2 and the maximum torque T2 of the servomotor 5 can be stored in the memory unit 11 together with the torque constant predefined for the servomotor 5, wherein the torque constant correction unit 12 reads the rated current I1, the rated torque T1, the maximum current I2, the maximum torque T2 and the torque constant of the servomotor 5 from the memory unit 11 and corrects the torque constant stored in the memory unit 11 according to a function in which the value associated with the current of the servomotor 5 is an independent variable and the torque constant decreases when the value associated with the current of the servomotor 5 increases.A method for writing the rated current I1, the rated torque T1, the maximum current I2 and the maximum torque T2 of the servomotor 5 into the storage unit 11 itself does not restrict the present embodiment, wherein the method for writing these parameters into the storage unit 11 is provided, for example, by an input action of an operator via a numerical control device (not shown) connected to the servomotor control device 1.

[0033] Referring again to Fig. 1. The power calculation unit 13 calculates the power of the servo motor 5 based on the torque constant stored in the storage unit 11 or the torque constant calculated by the torque constant correction unit 12 after correction, the value assigned to the current of the servo motor 5, and the value assigned to the speed of the servo motor 5. More precisely, the power calculation unit 13 calculates the power of the servo motor 5 based on the torque constant calculated by the torque constant correction unit 12 after correction, the value assigned to the current of the servo motor 5, and the value assigned to the speed of the servo motor 5 when the magnetic saturation determination unit 14 determines that magnetic saturation has occurred in the winding of the servo motor.If, however, the magnetic saturation determination unit 14 does not determine that magnetic saturation has occurred in the winding of the servo motor, the power calculation unit 13 calculates the power of the servo motor 5 based on the torque constant stored in the storage unit 11, the value assigned to the current of the servo motor 5, and the value assigned to the rotational speed of the servo motor 5. "The value assigned to the rotational speed of the servo motor 5" is either a rotor speed of the servo motor 5 detected by the rotational speed sensing unit 22 or a rotational speed command for the servo motor 5 generated by the rotational speed command generation unit 32.

[0034] Next, forms of the power calculation unit 13 and the magnetic saturation determination unit 14 in the servomotor control device 1 according to one embodiment described above are described successively. A servomotor control device of a first form uses measured actual values ​​with respect to current and speed, while a servomotor control device of a second form uses commands with respect to current and speed.

[0035] Fig. Figure 3 is a block diagram of the servo motor control device of the first form.

[0036] As in Fig. As shown in Figure 3, the magnetic saturation detection unit 14 in the servomotor control device 1 of the first form determines, based on the current flowing through the winding of the servomotor 5 as detected by the current sensing unit 21, whether magnetic saturation has occurred in the winding of the servomotor 5. More precisely, the magnetic saturation detection unit 14 determines that magnetic saturation has occurred in the winding of the servomotor 5 if the current flowing through the winding of the servomotor 5, as detected by the current sensing unit 21, exceeds a current threshold value, and determines that magnetic saturation has not occurred in the winding of the servomotor 5 if the current flowing through the winding of the servomotor 5 does not exceed the current threshold value. The current threshold value is set to the rated current of the servomotor 5.Alternatively, the current threshold can be set to a value close to the rated current of the servo motor 5.

[0037] If the magnetic saturation determination unit 14 determines that magnetic saturation has occurred in the winding of the servo motor 5, the power calculation unit 13 in the servo motor control device 1 of the first form calculates the power of the servo motor 5 based on the torque constant after correction calculated by the torque constant correction unit 12, the value of the current flowing through the winding of the servo motor 5, which is detected by the current sensing unit 21, and the rotor speed of the servo motor 5 detected by the speed sensing unit 22.If, however, the magnetic saturation determination unit 14 does not determine that magnetic saturation has occurred in the winding of the servomotor 5, the power calculation unit 13 in the servomotor control device 1 of the first form calculates the power of the servomotor 5 based on the torque constant stored in the storage unit 11, the value of the current flowing through the winding of the servomotor 5, which is detected by the current sensing unit 21, and the rotor speed of the servomotor 5 detected by the speed sensing unit 22. Assume that the value of the current flowing through the winding of the servomotor 5, which is detected by the current sensing unit 21, is i [A], the rotor speed (rotational speed) of the servomotor 5, which is detected by the speed sensing unit 22, is ω [rad / min], and the torque constant K, which is stored in the storage unit 11, is... T[Nm / A] and the torque constant calculated by the torque constant correction unit 12 after correction K T '[Nm / A] is, the power calculation unit 13 in the servo motor control device 1 of the first form calculates the power P1 [W] of the servo motor 1 according to equation 3. P1={2π×KT×i×w60(without magnetic saturation)2π×KT'×i×w60(when magnetic saturation occurs)

[0038] Fig. Figure 4 is a block diagram of the second-type servo motor control device.

[0039] As in Fig. As shown in Figure 4, the magnetic saturation detection unit 14 in the servo motor control device 1 of the second form determines, based on the current command generated by the current command generation unit 31, whether magnetic saturation has occurred in the winding of the servo motor 5. More precisely, the magnetic saturation detection unit 14 determines that magnetic saturation has occurred in the winding of the servo motor 5 if the current command generated by the current command generation unit 31 exceeds a current threshold value, and determines that magnetic saturation has not occurred in the winding of the servo motor 5 if the current command does not exceed the current threshold value. The current threshold value is set to the current command corresponding to the rated current of the servo motor 5. Alternatively, the current threshold value can be set to a value corresponding to the current command corresponding to the rated current of the servo motor 5.Since the current sensing unit 21 detects the value of the current flowing through the winding of the servomotor 5 according to the current command generated by the current command generation unit 31, the current command generated by the current command generation unit 31 precedes the value of the current flowing through the winding of the servomotor 5, which is detected by the current sensing unit 21; therefore, the servomotor control device of the second type can detect the occurrence of magnetic saturation in the winding of the servomotor 5 faster than the servomotor control device of the first type.

[0040] If the magnetic saturation determination unit 14 determines that magnetic saturation has occurred in the winding of the servo motor, the power calculation unit 13 in the servo motor control device 1 of the second form calculates the power of the servo motor 5 based on the torque constant after correction calculated by the torque constant correction unit 12, the current command generated by the current command generation unit 31 and the speed command generated by the speed command generation unit 32 for the servo motor 5.If, however, the magnetic saturation determination unit 14 does not determine that magnetic saturation has occurred in the winding of the servo motor, the power calculation unit 13 in the servo motor control device 1 of the second form calculates the power of the servo motor 5 based on the torque constant stored in the storage unit 11, the current command generated by the current command generation unit 31, and the speed command generated by the speed command generation unit 32 for the servo motor 5. Assume that the current command i* [A] generated by the current command generation unit 31, the speed command for the servo motor 5 ω* [rad / min] generated by the speed command generation unit 32, and the torque constant K stored in the storage unit 11. T [Nm / A] and the torque constant calculated by the torque constant correction unit 12 after correction K T' [Nm / A] is, the power calculation unit 13 in the servo motor control device 1 of the second form calculates the power P2 [W] of the servo motor 1 according to equation 4. P2={2π×KT×i*×w*60(without magnetic saturation)2π×KT'×i*×w*60(when magnetic saturation occurs)

[0041] The power P2 of servomotor 5 obtained according to equation 4 represents, in a sense, a power output expected in the near future rather than in the past. Therefore, using the power P2 of servomotor 5 obtained according to equation 4 in any controller offers the advantage of improving the controller's response sensitivity.

[0042] Fig. 5 is a flowchart showing the operating sequence of the servo motor control device according to one embodiment. The in Fig. The flowchart shown in section 5 can be applied to the servo motor control device of the first type, which uses measured actual values ​​in relation to the current and the speed, as well as with reference to Fig. 3 described, as well as to the servomotor control device of the second type, which uses commands in relation to current and speed, as described in reference to Fig. 4 described.

[0043] In a state where the servo motor control device 1 controls the drive of the servo motor 5, the magnetic saturation detection unit 14 determines in step S101 whether the value associated with the current of the servo motor 5 exceeds the current threshold value to detect the occurrence of magnetic saturation in the winding of the servo motor 5. If the magnetic saturation detection unit 14 determines that the value associated with the current of the servo motor 5 exceeds the current threshold value, the procedure proceeds to step S102; otherwise, the procedure proceeds to step S103.

[0044] In step S102, the torque constant correction unit 12 corrects the torque constant stored in the memory unit 11 such that the torque constant decreases when the value associated with the current of the servo motor 5 increases. In this case, the torque constant calculated by the torque constant correction unit 12 after the correction is expressed by a linear function, where, for example, the value associated with the current of the servo motor 5 is an independent variable, and the torque constant decreases when the value associated with the current of the servo motor 5 increases. The torque constant calculated by the torque constant correction unit 12 after the correction is sent to the power calculation unit 13.

[0045] In step S103, the power calculation unit 13 calculates the power of the servo motor 5 based on the torque constant stored in the storage unit 11 or the torque constant calculated by the torque constant correction unit 12 after correction, the value assigned to the current of the servo motor 5, and the value assigned to the speed of the servo motor 5. More precisely, if the magnetic saturation determination unit 14 determines in step S101 that magnetic saturation has occurred in the winding of the servo motor 5, the power calculation unit 13 calculates the power of the servo motor 5 in step S103 based on the torque constant calculated by the torque constant correction unit 12 after correction, the value assigned to the current of the servo motor 5, and the value assigned to the speed of the servo motor 5.If, however, the magnetic saturation determination unit 14 does not determine in step S101 that magnetic saturation has occurred in the winding of the servo motor 5, the power calculation unit 13 calculates the power of the servo motor 5 based on the torque constant stored in the storage unit 11, the value assigned to the current of the servo motor 5 and the value assigned to the speed of the servo motor 5.

[0046] The torque constant correction unit 12, power calculation unit 13, magnetic saturation determination unit 14, and motor control unit 30 (including the current command generation unit 31 and the speed command generation unit 32) described above can be implemented, for example, as a software program or as a combination of a multitude of electronic circuits and a software program. For example, if these units are implemented as a software program, the functions of the respective units are implemented by installing the software program on a DSP forming the motor control unit 30 and operating an arithmetic processor in the DSP (not shown) according to the software program.Alternatively, the torque constant correction unit 12, the power calculation unit 13 and the magnetic saturation determination unit 14 can be implemented as an integrated semiconductor circuit in which a software program for implementing the functions of the respective units is installed; in this case, the functions of the respective units are implemented by installing the integrated semiconductor circuit into an existing motor control unit.

[0047] The servomotor control device 1 described above, according to one embodiment, can be used, for example, in a servomotor control system to control a drive axis servomotor that drives an axis of an industrial machine or machine tool, in order to control a flywheel servomotor for driving a flywheel that serves as an energy storage device to reduce an energy peak value for the power supply device on the AC supply side. The servomotor control system is described below.

[0048] Fig. Figure 6 is a block diagram of a servo motor control system comprising the servo motor control device of the first form. For example, the servo motor control device 1 for controlling a flywheel servo motor 5-1 is implemented as a servo motor control device of the first form, which is defined by reference to Fig. 3 is described. An example in which the servomotor control device 1 for controlling the flywheel servomotor 5-1 is implemented as a servomotor control device of the second type, which is described with reference to Fig. As described in section 4, is described later Fig. 7 shown.

[0049] Fig. Figure 6 shows a case in which a single axis 8 is driven by a drive axis servomotor 105, although the number of axes 8 does not restrict the present embodiment and can be more than one. The type of drive axis servomotor 105 driving the axis 8 does not restrict the present embodiment and can, for example, be an asynchronous motor or a synchronous motor. The number of phases of the drive axis servomotor 105 does not specifically restrict the present embodiment and can, for example, include a single phase or several phases, apart from three phases.

[0050] The servo motor control system 1000 for controlling the drive axis servo motor 105, which drives the axis 8 of an industrial machine or machine tool, comprises a rectifier 2, a drive axis inverter 103, which serves as the first inverter, an energy storage device 200, and the servo motor control unit 1. The energy storage device 200 comprises a flywheel 7, the flywheel servo motor 5-1, and a flywheel inverter 3-1, which serves as the second inverter. The supply and storage of energy by the energy storage device 200 are controlled by the servo motor control unit 1, wherein the servo motor control unit 1 and the energy storage device 200 form a flywheel energy storage system.

[0051] Rectifier 2 converts alternating current (AC) energy from the AC power supply 4 into direct current (DC) energy and outputs the DC energy to the DC link. Examples of rectifier 2 include a diode rectifier circuit, a 120-degree line-type rectifier circuit, or a PWM-controlled rectifier circuit, all of which contain switching elements. If rectifier 2 is a diode rectifier circuit, it rectifies the alternating current supplied by the AC power supply 4 and outputs direct current to the DC link located on the DC side.If rectifier 2 is a 120-degree line-type rectifier circuit or a PWM-controlled rectifier circuit, rectifier 2 can be implemented as a power converter capable of performing conversion between AC and DC power in both directions, for example converting AC power supplied by AC supply 4 into DC power to output the DC power to the DC side, and converting DC power supplied by the DC link into AC power to output the AC power to AC supply 4.

[0052] The DC link, which connects the DC output side of rectifier 2 and the DC input side of the drive axis inverter 103, is equipped with a DC link capacitor 6. The DC link capacitor 6 has the function of storing DC energy in the DC link as well as suppressing a pulsating component of a DC output of rectifier 2.

[0053] The drive axis inverter 103, which serves as the first inverter, is connected to the DC link and performs an energy conversion between the DC energy in the DC link and the AC energy or renewable energy of the drive axis servomotor 105 used as drive energy. This conversion occurs when, according to the drive command supplied by a drive axis servomotor control device 101, a two-point control is performed for each switching element contained therein. The drive axis inverter 103 is implemented by a bridge circuit consisting of switching elements and diodes connected antiparallel to the switching elements. For each switching element, a two-point control is performed, for example, according to the PWM control method. In the present embodiment, since the drive axis servomotor 105 is three-phase, the drive axis inverter 103 is implemented as a three-phase bridge circuit.Examples of the switching elements include an IGBT, a thyristor, a GTO thyristor, and a transistor, although the type of switching elements itself does not limit the present embodiment and may include other types of switching elements. The drive axis inverter 103 causes the switching elements contained therein to perform a switching operation in accordance with the drive command received from the drive axis servo motor control device 101, in order to convert the DC energy in the DC link into AC energy with a desired voltage and frequency for driving the drive axis servo motor 105 (inversion operation). Through this operation, the drive axis servo motor 105 operates according to the supplied AC energy, which has a variable voltage and a variable frequency.For example, if regenerative energy is generated during the braking of the drive axis servomotor 105, the regenerative energy generated by the drive axis servomotor 105 is converted from alternating current to direct current energy according to the drive command received from the drive axis servomotor control device 101 and fed back to the DC link (conversion process). In order to supply drive energy to each drive axis servomotor 105 individually provided for each of a plurality of axes 8, the number of drive axis inverters 103 provided corresponds, for example, to a number corresponding to the number of drive axis servomotors 105, or is, for example, one for the plurality of drive axis servomotors 105, or corresponds, for example, to a number of drive axis inverters 103 that is a multiple of the number of windings of the drive axis servomotor 105 for one drive axis servomotor 105.In the example shown, the number of drive axis inverters is 103, because the number of drive axis servomotors is 105, to make the drawing concise.

[0054] The power storage device 200 includes the flywheel 7, the flywheel servo motor 5-1 and the flywheel inverter 3-1, which serves as a second inverter.

[0055] The flywheel 7 is capable of storing rotational energy and is connected to a rotating shaft of the flywheel servomotor 5-1.

[0056] The flywheel servomotor 5-1 comprises the rotating shaft to which the flywheel 7 is connected and is a servomotor with rotational inertia for rotating the flywheel 7. The number of phases of the flywheel servomotor 5-1 is not specifically limited by the present embodiment and can, for example, be a single phase or multiple phases, apart from three phases as shown in Fig. 6 shown, include.

[0057] If two-point control is performed for each switching element according to the current command supplied by the (motor control unit 30 of the) servo motor control device 1, the flywheel inverter 3-1, which serves as a second inverter, converts AC energy regenerated by the flywheel servo motor 5-1 into DC energy, or converts DC energy in the DC link into AC energy to drive the flywheel servo motor 5-1, according to the power of the drive shaft servo motor 105 and the power of the flywheel servo motor 5-1, which are calculated by the power calculation unit 13 in the servo motor control device 1. The flywheel inverter 3-1 is implemented by a bridge circuit consisting of switching elements and diodes connected antiparallel to the switching elements, with two-point control being performed for each switching element, for example according to the PWM control method.In the present embodiment, the flywheel inverter 3-1 is implemented as a three-phase bridge circuit, since the flywheel servomotor 5-1 is three-phase. Examples of the switching elements include an IGBT, a thyristor, a GTO thyristor, and a transistor, although the type of switching elements itself does not limit the present embodiment and may include other types of switching elements.

[0058] The configuration of the servo motor control device 1, which serves as a servo motor control device of the first type, corresponds to that referred to in Fig. 3 described. The supply and storage of energy by the energy storage device 200 are controlled by the servomotor control device 1. In other words, the servomotor control device 1 causes the energy storage device 200 to supply energy to the DC link by controlling the flywheel inverter 3-1 to convert AC energy regenerated by the flywheel servomotor 5-1 into DC energy, and recovers a portion of the energy in the DC link by controlling the flywheel inverter 3-1 to convert the DC energy in the DC link into AC energy to drive the flywheel servomotor 5-1, in order to store this portion in the energy storage device 200.

[0059] The amount of energy to be supplied and stored by the energy storage device 200 is determined based on the power of the drive axis servomotor 105, the power of the flywheel servomotor 5-1, which are calculated by the power calculation unit 13 in the servomotor control device 1, the capacity of the AC power supply 4, the energy conversion power of the rectifier 2, the energy conversion power of the flywheel inverter 3-1, the energy conversion power of the drive axis inverter 103, and the like. This is determined in particular as follows.

[0060] Since the drive axis servomotor 105 has a high energy consumption during acceleration, the output of high AC energy is preferably carried out by the AC power supply unit 4. In this case, the motor control unit 30 of the servomotor control device 1 controls the energy conversion by the flywheel inverter 3-1 such that the DC energy obtained by converting AC energy regenerated by the flywheel servomotor 5-1 by the flywheel inverter 3-1 is compensated only by the DC energy obtained by converting the AC energy from the AC power supply 4 by the rectifier 2. This DC energy is insufficient for the DC energy in the DC link required for conversion into AC energy, which is supplied by the drive axis inverter 103 as drive energy for the drive axis servomotor 105."The DC energy in the DC link required for conversion into AC energy, which is supplied by the drive axis inverter 103 as drive energy for the drive axis servomotor 105," is determined by information concerning the power of the drive axis servomotor 105 and received by the drive axis servomotor control device 101. "The DC energy obtained by converting the AC energy from the AC power supply 4 by the rectifier 2" is determined by the capacitance of the power supply unit of the AC power supply 4 and the energy conversion power of the rectifier 2.If the difference in electrical energy obtained by subtracting "the DC energy obtained by converting the AC energy of the AC power supply 4 by the rectifier 2" from "the DC energy in the DC link required for conversion into AC energy supplied by the drive axis inverter 103 as drive energy for the drive axis servomotor 105" is positive, this shows that "the DC energy obtained by converting the AC energy of the AC power supply 4 by the rectifier 2" alone cannot cover "the DC energy in the DC link required for conversion into AC energy supplied by the drive axis inverter 103 as drive energy for the drive axis servomotor 105" and is insufficient.In such a case, the DC energy obtained by converting AC energy regenerated by the flywheel servomotor 5-1 via the flywheel inverter 3-1 compensates for the deficit. Through this process, energy supplied to the DC link by the energy storage device 200 during the acceleration of the drive axle servomotor 105 is used in addition to the energy from the AC power supply 4, and it is possible to reduce the peak energy demand on the AC power supply side.

[0061] The amount of energy supplied and stored by the energy storage device 200, as described above, is directly related to the power of the flywheel servomotor 5-1. Therefore, an accurate calculation of the power of the flywheel servomotor 5-1 is important when controlling the energy supplied and stored by the energy storage device 200. The calculation of the power of the flywheel servomotor 5-1 by the power calculation unit 13 in the servomotor control device 1 is carried out as described with reference to Fig. 3 described. In other words, when the magnetic saturation determination unit 14 determines that magnetic saturation has occurred in the winding of the flywheel servomotor 5-1, the power calculation unit 13 calculates the power of the flywheel servomotor 5-1 based on the torque constant after correction calculated by the torque constant correction unit 12, the value of the current flowing through the winding of the flywheel servomotor 5-1, which is detected by the current sensing unit 21, and the rotor speed of the flywheel servomotor 5-1, which is detected by the speed sensing unit 22.If, on the other hand, the magnetic saturation determination unit 14 does not determine that magnetic saturation has occurred in the winding of the flywheel servomotor 5-1, the power calculation unit 13 calculates the power of the flywheel servomotor 5-1 based on the torque constant stored in the storage unit 11, the value of the current flowing through the winding of the flywheel servomotor 5-1, which is detected by the current sensing unit 21, and the rotor speed of the flywheel servomotor 5-1 detected by the speed sensing unit 22.Thus, the torque constant predefined for the flywheel servomotor 5-1 is corrected, and the power of the flywheel servomotor 5-1 is calculated using the torque constant after correction when magnetic saturation has occurred in the winding of the flywheel servomotor 5-1. Conversely, the power of the flywheel servomotor 5-1 is calculated using the torque constant predefined for the flywheel servomotor 5-1 when magnetic saturation has not occurred in the winding of the flywheel servomotor 5-1. Therefore, the power of the flywheel servomotor 5-1 can be calculated with a high degree of accuracy. By using the highly accurate calculation result regarding the power of the flywheel servomotor 5-1, the amount of energy supplied and stored by the energy storage device 200 can be controlled with a high degree of accuracy.

[0062] The power of the drive axis servomotor 105 can be calculated as an energy quantity based on the current flowing through the winding of the drive axis servomotor 105 and the voltage applied to the input terminal of the drive axis servomotor 105. Furthermore, the drive axis servomotor control device 101 can be implemented as a servomotor control device of the first type, which, with reference to Fig. 3, and the calculation of the power of the drive axis servomotor 105 is performed while simultaneously controlling the drive axis servomotor 105. In this case, the magnetic saturation determination unit 14 in the servomotor control device 1 for the drive axis determines whether magnetic saturation has occurred in the winding of the drive axis servomotor 105. If magnetic saturation has occurred, the torque constant correction unit 12 in the servomotor control device 1 for the drive axis corrects the torque constant predefined for the drive axis servomotor 105. If magnetic saturation has occurred, the power calculation unit 13 in the servomotor control device 1 for the drive axis calculates the power of the drive axis servomotor 105, and the motor control unit 30 in the servomotor control device 1 for the drive axis controls the energy conversion by the drive axis inverter 103.

[0063] Regarding the in Fig. In the servomotor control system 1000 shown, the servomotor control device 1 for controlling the flywheel servomotor 5-1 is implemented, for example, as a servomotor control device of the first type, which is designed with reference to Fig. 3 described, however, the servomotor control device 1 can instead be implemented as a servomotor control device of the second form, which is described with reference to Fig. 4 is described below. This is further explained below with reference to Fig. 7 described.

[0064] Fig. Figure 7 is a block diagram of a servo motor control system that includes the servo motor control device of the second type. The servo motor control device of the second type uses commands with respect to current and speed, respectively. Therefore, by changing the signals that go into the power calculation unit 13 and the magnetic saturation determination unit 14 in the servo motor control device 1 according to the diagram referenced in Figure 7, the following changes can be made: Fig. 6 described embodiment, input from the signals from the current sensing unit 21 and the speed sensing unit 22, as with reference to Fig. 3 described, in signals from the current command generation unit 31 and the speed command generation unit 32, as described with reference to Fig. 4 described, which in Fig. The servomotor control system 1000 shown in section 7 is implemented, comprising the servomotor control device of the second type. Other components besides these are connected with the ones shown in Fig. 4 and Fig. The 6 components shown are comparable. Fig. In the servomotor control system 1000 shown in Figure 7, the current command generated by the current command generation unit 31 precedes the value of the current flowing through the winding of the flywheel servomotor 5-1, which is detected by the current sensing unit 21; therefore, the current command generated by the current command generation unit 31 precedes the current flowing through the winding of the flywheel servomotor 5-1, which is detected by the current sensing unit 21; therefore, the current in the servomotor control system 1000 can be determined by the current command generated by the current command generation unit 31. Fig. The servomotor control system 1000 shown in Figure 7 detects the occurrence of magnetic saturation in the winding of the flywheel servomotor 5-1 more quickly. In other words, the flywheel servomotor 5-1 in the Fig. The servomotor control system 1000 shown in Figure 7, which includes the servomotor control device of the second type, is more sensitive to response than the one shown in Figure 7. Fig. 6 servomotor control system 1000 shown, which includes the servomotor control device of the first form.

[0065] Fig. Figure 8 is a flowchart showing the operating sequence of the servo motor control system, which includes the servo motor control device according to one embodiment. The diagram in Fig. The flowchart shown in section 8 can be applied to the flowchart with reference to Fig. 6 described servomotor control system 1000, which includes the servomotor control device of the first form, as well as the one referred to in Fig. Apply the servomotor control system 1000 described in section 7, which includes the servomotor control device of the second type.

[0066] In a state where the drive-axis servo motor control device 101 controls the drive of the drive-axis servo motor 105, the magnetic saturation detection unit 14 determines in step S101 whether the value associated with the current of the flywheel servo motor 5-1 exceeds the current threshold value to detect the occurrence of magnetic saturation in the winding of the flywheel servo motor 5-1. If the magnetic saturation detection unit 14 determines in step S101 that the value associated with the current of the flywheel servo motor 5-1 exceeds the current threshold value, the procedure proceeds to step S102; otherwise, the procedure proceeds to step S103.

[0067] In step S102, the torque constant correction unit 12 corrects the torque constant stored in the storage unit 11 such that the torque constant decreases when the value associated with the current of the flywheel servomotor 5-1 increases. In this case, the torque constant calculated by the torque constant correction unit 12 after the correction is expressed by a linear function, where, for example, the value associated with the current of the flywheel servomotor 5-1 is an independent variable, and the torque constant decreases when the value associated with the current of the flywheel servomotor 5-1 increases. The torque constant calculated by the torque constant correction unit 12 after the correction is sent to the power calculation unit 13.

[0068] In step S103, the power calculation unit 13 calculates the power of the flywheel servomotor 5-1 based on the torque constant stored in the storage unit 11 or the torque constant calculated by the torque constant correction unit 12 after correction, the value assigned to the current of the flywheel servomotor 5-1, and the value assigned to the rotational speed of the flywheel servomotor 5-1. More precisely, if the magnetic saturation determination unit 14 determines in step S101 that magnetic saturation has occurred in the winding of the flywheel servomotor 5-1, the power calculation unit 13 calculates the power of the flywheel servomotor 5-1 in step S103 based on the torque constant calculated by the torque constant correction unit 12 after correction, the value assigned to the current of the flywheel servomotor 5-1, and the value assigned to the rotational speed of the flywheel servomotor 5-1.If, however, the magnetic saturation determination unit 14 does not determine in step S101 that magnetic saturation has occurred in the winding of the flywheel servomotor 5-1, the power calculation unit 13 calculates the power of the flywheel servomotor 5-1 based on the torque constant stored in the storage unit 11, the value assigned to the current of the flywheel servomotor 5-1 and the value assigned to the speed of the flywheel servomotor 5-1.

[0069] In step S104, the drive axis servo motor control device 101 determines whether the drive axis servo motor 105 is consuming energy. The result of this determination is sent to the motor control unit 30 in the servo motor control device 1, which controls the flywheel servo motor 5-1. The power consumption of the drive axis servo motor 105 can be calculated as the amount of energy based on the current flowing through the winding of the drive axis servo motor 105 and the voltage applied to the input terminal of the drive axis servo motor 105. Furthermore, the drive axis servo motor control device 101 can be implemented as a servo motor control device of the first type, which, with reference to Fig.3 is described, and the power consumption of the drive axis servomotor 105 is calculated. If step S104 determines that the drive axis servomotor 105 consumes energy, the procedure continues with step S105; otherwise, the procedure proceeds to step S107.

[0070] If in step S104 it is determined that the drive axis servomotor 105 is not consuming any energy, the drive axis servomotor 105 decelerates and is in a state of AC energy regeneration, with the AC energy being stored in the power storage device 200 in step S107.More precisely, the drive axis servo motor control device 101 controls the drive axis inverter 103 to convert the regenerative energy generated by the drive axis servo motor 105 from alternating current into direct current energy and feed the direct current energy back into the DC link (conversion process), while the servo motor control device 1 controls the flywheel inverter 3-1 to perform an inversion process in which the direct current energy in the DC link is converted into alternating current energy; therefore, the energy in the DC link flows into the flywheel servo motor 5-1 to enable the flywheel servo motor 5-1 to rotate. Through this process, the input electrical energy is stored in the form of rotational energy of the flywheel 7 (step S107).

[0071] If in step S104 it is determined that the drive axis servomotor 105 consumes energy, the motor control unit 30 in the servomotor control device 1 determines in step S105 whether "the DC energy obtained by converting the AC energy of the AC power supply 4 by the rectifier 2" alone is insufficient for "the DC energy in the DC link required for conversion into AC energy, which is supplied by the drive axis inverter 103 as drive energy for the drive axis servomotor 105".More precisely, the motor control unit 30 calculates a difference by subtracting "the DC energy obtained by converting the AC energy of the AC power supply 4 by the rectifier 2" from "the DC energy in the DC link required for conversion to AC energy, which is supplied by the drive axis inverter 103 as drive energy for the drive axis servomotor 105." If the difference in electrical energy is positive, the motor control unit 30 determines that the DC energy obtained by converting the AC energy of the AC power supply 4 by the rectifier 2 is insufficient on its own to drive the drive axis servomotor 105. If it is determined that the energy to drive the drive axis servomotor 105 is insufficient, the procedure continues with step S106; otherwise, the procedure returns to step S101.

[0072] In step S106, the servo motor control device 1 controls the flywheel inverter 3-1 to perform a conversion process in which the AC energy regenerated by reducing the speed of the flywheel servo motor 5-1 is converted into DC energy. Through this process, the rotational energy stored in the flywheel 7 is converted into electrical energy via the flywheel servo motor 5-1 and the flywheel inverter 3-1 and supplied to the DC link (S106). By incorporating such a configuration, when the drive axis servo motor 105 consumes energy (during acceleration of the drive axis servo motor 105), the energy supplied to the DC link by the energy storage device 200 can be used in addition to the energy from the AC power supply 4, thus reducing the peak energy demand on the AC power supply side.After this step, the procedure returns to step S101 and the operations of steps S101 to S107 are executed again.

[0073] Thus, when a flywheel energy storage system is provided to reduce an energy peak value for the power supply device on the AC supply side in a servo motor control system for controlling a drive axis servo motor that drives an axis of an industrial machine or machine tool, a highly accurate calculation result regarding the power of the flywheel servo motor is used; therefore, the amount of energy supplied and stored by the energy storage device can be controlled with a high degree of accuracy.

[0074] According to one aspect of the present disclosure, if magnetic saturation occurs in a winding of a servo motor, a torque constant predefined for the servo motor is corrected, and the power of the servo motor is calculated based on the torque constant after the correction, a value associated with a current of the servo motor, and a value associated with a speed of the servo motor; if, on the other hand, no magnetic saturation occurs in the winding of the servo motor, the power of the servo motor is calculated based on the torque constant predefined for the servo motor, the value associated with the current of the servo motor, and the value associated with the speed of the servo motor, whereby the power of the servo motor can be calculated with a high degree of accuracy.

Claims

[1] Servo motor control system (1000) for controlling a drive axis servo motor (105) that drives an axis (8) of an industrial machine or machine tool, comprising: - a rectifier (2) which is configured to convert alternating current energy from an alternating current supply (4) into direct current energy and to output the direct current energy to a direct current intermediate circuit, - a first inverter (103) which is connected to the DC intermediate circuit and is configured to perform an energy conversion between the DC energy in the DC intermediate circuit and the AC energy or regenerative energy of the drive axis servomotor (105) used as drive energy, - a flywheel (7), - a flywheel servo motor (5-1) connected to the flywheel (7) and configured to rotate the flywheel (7), - a second inverter (3-1) connected to the DC link and configured to perform an energy conversion between the DC energy in the DC link and the AC energy or regenerative energy of the flywheel servomotor (5-1) used as drive energy, and - a servo motor control device (1) configured to control the flywheel servo motor (5-1), - comprising the servo motor control device (1): - a storage unit (11) configured to store a predefined torque constant for the servo motor (5), - a torque constant correction unit (12) configured to correct the torque constant stored in the storage unit (11) when magnetic saturation occurs in a winding of the servo motor (5), and - a power calculation unit (13) configured to calculate a power of the servo motor (5) based on the torque constant stored in the storage unit (11) or the torque constant calculated after correction by the torque constant correction unit (12), a value associated with a current of the servo motor (5) and a value associated with a speed of the servo motor (5), and - wherein the energy conversion by the second inverter (3-1) is controlled such that the alternating current energy regenerated by the flywheel servomotor (5-1) is converted into direct current energy or the direct current energy in the DC intermediate circuit is converted into alternating current energy to drive the flywheel servomotor (5-1) according to a power of the drive axle servomotor (105) and a power of the flywheel servomotor (5-1) which are calculated by the power calculation unit (13). [2] Servo motor control system (1000) according to claim 1, further comprising: - a magnetic saturation determination unit (14) designed to determine whether magnetic saturation has occurred in the winding of the servomotor (5), - wherein, when the magnetic saturation determination unit (14) determines that magnetic saturation has occurred in the winding of the servo motor (5), the torque constant correction unit (12) corrects the torque constant stored in the storage unit (11) and the power calculation unit (13) calculates a power of the servo motor (5) based on the torque constant calculated by the torque constant correction unit (12) after correction, the value associated with the current of the servo motor (5) and the value associated with the speed of the servo motor (5). [3] Servo motor control system (1000) according to claim 2, wherein, when the value associated with the current of the servo motor (5) exceeds a predetermined current threshold value, the magnetic saturation determination unit (14) determines that magnetic saturation has occurred in the winding of the servo motor (5). [4] Servo motor control system (1000) according to claim 3, wherein the current threshold is set to a value corresponding to a rated current of the servo motor (5) or to a value close to the rated current. [5] Servo motor control system (1000) according to one of claims 1 to 4, wherein, when magnetic saturation has occurred in the winding of the servo motor (5), the torque constant correction unit (12) corrects the torque constant stored in the storage unit (11) such that the torque constant decreases when the value associated with the current of the servo motor (5) increases. [6] Servo motor control system (1000) according to claim 5, wherein the torque constant calculated by the torque constant correction unit (12) is expressed after correction by a linear function in which the value associated with the current of the servo motor (5) is an independent variable and the torque constant decreases when the value associated with the current of the servo motor (5) increases. [7] Servo motor control system (1000) according to any one of claims 1 to 6, comprising: - a current sensing unit (21) configured to detect a value of the current flowing through the winding of the servo motor (5), - wherein the value assigned to the current of the servomotor (5) is the value of the current flowing through the winding of the servomotor (5) which is detected by the current sensing unit (21). [8] Servo motor control system (1000) according to any one of claims 1 to 6, comprising: - a current command generation unit (31) configured to generate a current command for current flowing in the winding of the servo motor (5), - where the value assigned to the current of the servo motor (5) is the current command generated by the current command generation unit (31). [9] Servo motor control system (1000) according to any one of claims 1 to 8, comprising: - a speed detection unit (22) which is configured to detect a rotor speed of the servo motor (5), - wherein the value assigned to the speed of the servomotor (5) is the rotor speed of the servomotor (5) as detected by the speed sensing unit (22). [10] Servo motor control system (1000) according to any one of claims 1 to 8, comprising: - a speed command generation unit (32) configured to generate a speed command for the servo motor (5), - wherein the value assigned to the speed of the servo motor (5) is a value of the speed command for the servo motor (5) generated by the speed command generation unit (32). [11] Servo motor control system (1000) according to any one of claims 1 to 10, comprising: - at least two of the servo motor control devices (1) according to one of claims 1 to 10, which are configured to control the drive axle servo motor (105) and the flywheel servo motor (5-1) respectively, - wherein the energy conversion by the second inverter (3-1) is controlled such that the alternating current energy regenerated by the flywheel servomotor (5-1) is converted into direct current energy or the direct current energy in the DC intermediate circuit is converted into alternating current energy to drive the flywheel servomotor (5-1) according to a power of the drive axle servomotor (105) and a power of the flywheel servomotor (5-1) which are calculated by the power calculation unit (13). [12] Servo motor control system (1000) according to one of claims 1 to 11, wherein the energy conversion by the second inverter (3-1) is controlled such that direct current energy obtained by converting alternating current energy regenerated by the flywheel servo motor (5-1) by the second inverter (3-1) compensates for a portion that is insufficient for the direct current energy in the DC link required for conversion into alternating current energy supplied by the first inverter (103) as drive energy of the drive axis servo motor (105) only with direct current energy obtained by converting the alternating current energy of the AC supply (4) by the rectifier (2).

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