Control device for permanent magnet synchronous motor and electric power steering device having the same

Abstract

This invention provides a control device for a permanent magnet synchronous motor capable of following rapid changes in rotational speed with a weak current command. The control device (2) for the permanent magnet synchronous motor includes a reference voltage value calculation unit (3) for calculating a reference voltage value, an output voltage value calculation unit (4) for calculating an output voltage value based on a voltage command, a weak current command calculation unit (5) for calculating a weak current command based on the reference voltage value and the output voltage value, a voltage command calculation unit (6) for calculating a voltage command based on the weak current command, and a power converter (7) for supplying power to the permanent magnet synchronous motor (1) based on the voltage command. The weak current command calculation unit calculates a weak current command with amplified high-frequency components based on the difference between the reference voltage value and the output voltage value.

Description

Technical Field

[0001] This application relates to a control device for a permanent magnet synchronous motor and an electric power steering device having the control device. Background Technology

[0002] The induced voltage of a permanent magnet synchronous motor increases with increasing speed. Due to the limitation of the power supply voltage, voltage saturation occurs, making it difficult for current to pass through. As a result, the output torque decreases in the high-speed rotation region.

[0003] In permanent magnet synchronous motors, field weakening control is employed to prevent a decrease in output torque during high-speed rotation. In field weakening control, a negative current flows through the d-axis current to reduce the magnetic flux in the d-axis direction, thereby suppressing voltage saturation. Furthermore, the current command for the d-axis current during field weakening control is called the field weakening current command.

[0004] For example, in existing permanent magnet synchronous motors, methods for controlling a weak current command based on the speed are known (e.g., see Patent Document 1). Furthermore, in other permanent magnet synchronous motors, methods for controlling a weak current command based on the power supply voltage are known (e.g., see Patent Document 2).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-20411

[0008] Patent Document 2: WO2008 / 152929 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] However, conventional permanent magnet synchronous motors that control the low current command based on the speed have a problem where the low current command cannot keep up with rapid changes in speed.

[0011] This application is made to solve the above-mentioned problems, and its purpose is to provide a control device for a permanent magnet synchronous motor that enables a weak current command to follow a rapid change in rotational speed.

[0012] Technical means for solving technical problems

[0013] The control device for the permanent magnet synchronous motor of this application includes: a reference voltage value calculation unit that calculates a reference voltage value based on the power supply voltage; an output voltage value calculation unit that calculates an output voltage value based on a voltage command; a weak current command calculation unit that calculates a d-axis current command, i.e., a weak current command, for field weakening control based on the reference voltage value and the output voltage value; a voltage command calculation unit that calculates the voltage command based on the weak current command; and a power converter that supplies power to the permanent magnet synchronous motor based on the voltage command. Furthermore, the weak current command calculation unit calculates a weak current command with amplified high-frequency components based on the difference between the reference voltage value and the output voltage value.

[0014] Invention Effects

[0015] The control device for the permanent magnet synchronous motor of this application includes a weak current command calculation unit that calculates a weak current command with amplified high-frequency components based on the difference between the reference voltage value and the output voltage value, thus enabling the weak current command to follow rapid changes in rotational speed. Attached Figure Description

[0016] Figure 1 This is a structural diagram of the control device for the permanent magnet synchronous motor according to Embodiment 1.

[0017] Figure 2 This is a structural diagram of the voltage command arithmetic unit according to Embodiment 1.

[0018] Figure 3 This is a structural diagram of the weak current command processing unit involved in Embodiment 1.

[0019] Figure 4 This is a characteristic diagram of the phase-lead filter involved in Implementation Method 1.

[0020] Figure 5 This is a structural diagram of the weak current command processing unit involved in Embodiment 2.

[0021] Figure 6 This is a structural diagram of the weak current command processing unit involved in Embodiment 3.

[0022] Figure 7 This is a structural diagram of the high-frequency amplification section of the weak current command processing unit involved in Embodiment 4.

[0023] Figure 8 This is a structural diagram of the electric power steering device involved in Embodiment 6.

[0024] Figure 9 This is a schematic diagram illustrating an example of the hardware of the control device for the permanent magnet synchronous motor according to embodiments 1 to 5. Detailed Implementation

[0025] The control device for a permanent magnet synchronous motor and the electric power steering device using the control device, according to embodiments of this application, will now be described in detail with reference to the accompanying drawings. Furthermore, the same reference numerals in the drawings indicate the same or equivalent parts.

[0026] Implementation method 1.

[0027] Figure 1 This is a structural diagram of the control device for the permanent magnet synchronous motor according to Embodiment 1. Additionally, Figure 1 In the diagram, the object controlled by the control device of the permanent magnet synchronous motor, namely the permanent magnet synchronous motor, is also shown.

[0028] The permanent magnet synchronous motor 1 can be a commonly known type of motor, such as a surface permanent magnet synchronous motor (SPM) or an interior permanent magnet synchronous motor (IPM). The permanent magnet synchronous motor 1 has three-phase windings: U-phase, V-phase, and W-phase. Furthermore, the permanent magnet synchronous motor 1 has a rotor that generates excitation flux through permanent magnets or excitation windings.

[0029] An angle detector 11 is mounted on the permanent magnet synchronous motor 1 to detect the rotation angle θ of the permanent magnet synchronous motor 1. The angle detector 11 can be an angle detector such as a rotary transformer or a Hall sensor.

[0030] The control device 2 for the permanent magnet synchronous motor consists of a reference voltage value calculation unit 3, an output voltage value calculation unit 4, a low current command calculation unit 5, a voltage command calculation unit 6, and a power converter 7. First, the operation of each component of the control device 2 for the permanent magnet synchronous motor will be briefly described.

[0031] The reference voltage calculation unit 3 calculates the reference voltage value, which serves as the reference for field weakening control, based on the power supply voltage. The output voltage calculation unit 4 calculates the output voltage value based on the three-phase voltage command related to the voltage applied to the three-phase windings of phases U, V, and W. The field weakening current command calculation unit 5 calculates the d-axis current command used for field weakening control based on the output voltage value and the reference voltage value. The voltage command calculation unit 6 calculates the three-phase voltage command based on the d-axis current command and the q-axis current command. The power converter 7 applies the three-phase voltage to the permanent magnet synchronous motor 1 based on the three-phase voltage command.

[0032] Next, the operation of each structural part of the control device 2 for the permanent magnet synchronous motor will be described in detail.

[0033] Power converter 7 supplies power to the power supply voltage V from the power source. dc Perform the conversion to change the three-phase voltage V u vv v w The three-phase windings of the permanent magnet synchronous motor 1 are applied. The power converter 7 is composed of an inverter and other power converters. The power converter 7 transmits power to the three-phase voltage command v (described later). u * v v * v w * Modulation processing is performed by applying AC voltages to the U-phase winding, V-phase winding, and W-phase winding respectively. Furthermore, the modulation processing performed by the power converter 7 includes, for example, PWM (Pulse Width Modulation) or PAM (Pulse Amplitude Modulation).

[0034] A current detector (not shown) is installed on the power converter 7 to detect the current flowing to the permanent magnet synchronous motor 1. The current detector detects the current i in the U-phase winding. u The current i in phase V winding v and the current i of phase W winding w i u i v i w This is collectively referred to as the three-phase winding current. The current detector is constructed using current detectors such as shunt resistors and Hall elements. Additionally, the three-phase winding current i... u i v i w The current is the value obtained from the current detector, but it is also possible to use a value estimated from the voltage equation, etc., without using a current detector. That is, the three-phase winding current of the permanent magnet synchronous motor 1 is the detected or estimated current.

[0035] Figure 2 This is a structural diagram of the voltage command calculation unit 6 in this embodiment. The voltage command calculation unit 6 includes a coordinate transformation unit 61 and a voltage command generation unit 62.

[0036] Coordinate transformation unit 61 assigns d-axis voltage command v based on rotation angle θ d * and q-axis voltage command v q * Perform coordinate transformation to generate the U-phase voltage command v u * V-phase voltage command v v * and W phase voltage command v w * Furthermore, the coordinate transformation unit 61 modulates the U-phase detection current i based on the rotation angle θ. u V-phase detection current i vand W-phase detection current i w Perform coordinate transformation to generate the d-axis detection current i d and q-axis current detection i q Additionally, the d-axis current i is detected. d and q-axis current detection i q This is collectively referred to as the detection current. Furthermore, although the rotation angle θ is a detected value obtained from the angle detector 11, it is also possible to use a value estimated by the power converter 7 instead of the angle detector 11. That is, the rotation angle θ of the permanent magnet synchronous motor 1 is a detected or estimated angle.

[0037] Voltage command generation unit 62 uses d-axis current command i d * and d-axis detection current i d Generate d-axis voltage command v d * and using the q-axis current command i q * and q-axis current detection i q Generate q-axis voltage command v q * The voltage command generation unit 62 includes two subtractors 621 and 622 and two PI controllers 623 and 624. Subtractor 621 calculates the d-axis current command i. d * With d-axis detection current i d The deviation between them. Subtractor 622 calculates the q-axis current command i. q * With q-axis detection current i q The deviation between them. The PI controller 623 calculates the d-axis voltage command v used to control the output voltage of the power converter 7. d * This reduces the deviation calculated by subtractor 621. PI controller 624 calculates the q-axis voltage command v for controlling the output voltage of power converter 7. q * This reduces the deviation calculated by subtractor 622.

[0038] In the voltage command generation unit 62 of this embodiment, a PI controller 623 is used to perform proportional and integral control as the voltage command i for the d-axis current. d * and d-axis detection current i d Calculate the deviation between the d-axis voltage command v d * Feedback control. The calculation method for feedback control is not limited to this; other feedback control calculation methods can be used. Furthermore, the q-axis voltage command v is calculated. q *The same applies to the operation method of feedback control.

[0039] d-axis current command i d * The calculation is performed by the weak current command arithmetic unit 5. In addition, the q-axis current command i... q * There are no particular restrictions on the calculation method. For example, the calculation method can be performed using the traditional feedback control methods such as torque control and speed control.

[0040] Figure 3 This is a structural diagram of the weak current command processing unit 5 in this embodiment. The weak current command processing unit 5 in this embodiment consists of a high-frequency amplifier 51, a subtractor 52, and a compensator 53. It processes the output voltage value V... a and reference voltage value V b Input is sent to the low-current command processing unit 5. Output voltage value V a This is a value related to the output voltage of power converter 7. Output voltage value V a In the output voltage value calculation unit 4, the three-phase voltage command v is used... u * v v * v w * Use equation (1) to perform the operation.

[0041] [Mathematical Expression 1]

[0042]

[0043] Reference voltage value V b The power supply voltage V is used in the reference voltage calculation unit 3. dc and maximum modulation rate k max The calculation is performed using equation (2). Here, the reference voltage value V... b It is based on the power supply voltage V dc Values ​​related to the maximum output voltage. Maximum modulation rate k. max For example, k max =1. m represents the margin relative to the maximum output voltage. Furthermore, even if k... max Setting it to a value smaller than the maximum modulation rate, such as 0.9, can also provide a margin relative to the maximum voltage.

[0044] [Mathematical Expression 2]

[0045]

[0046] During the operation phase of the weak current command, V is set. a =V b At that time, due to the influence of differential terms and voltage disturbances, Va Increasing the voltage can sometimes lead to momentary voltage saturation. In this case, a larger m ensures a greater margin and makes it easier to avoid voltage saturation. On the other hand, if m is too large, there will be a problem of applying excessive weak current. Here, to avoid applying excessive weak current, we assume m = 0. Power supply voltage V dc It can be the detected power supply voltage value or a preset constant.

[0047] Output voltage value V a The input is fed into the high-frequency amplification unit 51 of the weak current command processing unit 5. The high-frequency amplification unit 51 amplifies the output voltage value V. a The high-frequency components are calculated and the output voltage value V is corrected. a Here, in order to increase the high-frequency components in the frequency band higher than any other frequency, the high-frequency amplification unit 51 adopts the phase-lead filter F(s) of equation (3). The relationship between the parameters ω1 and ω2 of the phase-lead filter F(s) is ω1 > ω2. By setting the high-frequency amplification unit 51 as a phase-lead filter, a simple structure can be achieved without complex calculations and prior mapping.

[0048] [Mathematical Expression 3]

[0049]

[0050] Figure 4 This is an example of the frequency characteristics of a phase-lead filter F(s). In this phase-lead filter, the stable gain is 1, and when abrupt changes in rotational speed, etc., do not cause abrupt voltage changes, the same performance as in the prior art can be obtained. On the other hand, due to the increased gain in the high-frequency band, the responsiveness can be improved when abrupt changes in rotational speed, etc., cause abrupt voltage changes.

[0051] Furthermore, although the high-frequency amplification unit 51 is a phase-lead filter in this embodiment, it can be any other filter as long as it can amplify high-frequency components. For example, a filter composed of a phase-lead filter and a low-pass filter can be used as the high-frequency amplification unit 51. By using such a filter, it is possible to amplify the high-frequency components of the desired frequency band while cutting off unwanted high-frequency components mixed with noise.

[0052] Subtractor 52 uses the reference voltage value V b Subtract the corrected output voltage value V calculated by the high-frequency amplification unit 51 from the middle. a The voltage deviation ΔV is calculated using the compensator 53. The d-axis current is calculated based on the voltage deviation ΔV using the command i. d * The compensator 53 can be an integrator or a PI controller. Here, the compensator 53 is set as an integrator, using the compensator C(s) given by equation (4). Integral gain Ki By control response ω w The rotational speed ω of the permanent magnet synchronous motor 1 m It is determined by the inductance L.

[0053] [Mathematical Expression 4]

[0054]

[0055] Compensator 53 uses the compensator C(s) given by equation (4) to calculate the d-axis current command i based on the voltage deviation ΔV. d * The d-axis current command i calculated by compensator 53 d * This becomes a weak current command used for field weakening control. Therefore, the weak current command arithmetic unit 5 calculates the weak current command used for field weakening control.

[0056] In this configuration, the control device for the permanent magnet synchronous motor calculates a weak current command with amplified high-frequency components based on the difference between the reference voltage and the output voltage in the weak current command processing unit. Therefore, field weakening control can be performed to prevent voltage saturation. Furthermore, by amplifying the high-frequency components of the weak current command, this control device can ensure that the weak current command changes accordingly when both the rotational speed and output voltage change drastically. Additionally, the control device for the permanent magnet synchronous motor in this embodiment can also ensure that the weak current command changes accordingly when the power supply voltage changes drastically.

[0057] Furthermore, in the weak current command processing unit of this embodiment, by using a phase lead filter as a filter to amplify high-frequency components, the gain is increased in a frequency band higher than the frequency preset in the phase lead filter, thereby amplifying the high-frequency components of the weak current command and improving the responsiveness of the weak current command.

[0058] Implementation method 2.

[0059] The weak current command processing unit in Implementation Method 1 amplifies the output voltage value V using a high-frequency amplification unit. a The high-frequency components are used to calculate and correct the output voltage value V. a ', using a subtractor to obtain the reference voltage value V b Subtract the corrected output voltage value V from the middle a The voltage deviation ΔV is calculated using the weak current command calculation unit in Implementation Method 2, which calculates the voltage deviation ΔV from the reference voltage value V. b Subtract the output voltage value V a The voltage deviation ΔV is calculated, and the high-frequency component of the voltage deviation ΔV is amplified to calculate the corrected voltage deviation ΔV'.

[0060] Figure 5This is a structural diagram of the weak current command calculation unit 5 according to this embodiment. The weak current command calculation unit 5 according to this embodiment is the same as the weak current command calculation unit in Embodiment 1, consisting of a high-frequency amplification unit 51, a subtractor 52, and a compensator 53. Figure 5 As shown, in the weak current command calculation unit 5 of this embodiment, the subtractor 52 calculates the current from the reference voltage value V. b Subtract the output voltage value V a The voltage deviation value ΔV is calculated. Then, the high-frequency amplification unit 51 amplifies the high-frequency component of the voltage deviation ΔV and calculates the corrected voltage deviation ΔV'. The compensator 53 calculates the d-axis current command i based on the corrected voltage deviation ΔV'. d * This refers to a weak current command.

[0061] The control device for this permanent magnet synchronous motor is similar to that in Embodiment 1. It calculates a weak current command with amplified high-frequency components based on the difference between the reference voltage and the output voltage. Therefore, field weakening control can be performed to avoid voltage saturation. Furthermore, by amplifying the high-frequency components of the weak current command, this control device can make the weak current command change accordingly when the rotational speed changes drastically. Moreover, the control device for this embodiment can also make the weak current command change accordingly when the output voltage changes drastically due to a sudden change in the power supply voltage.

[0062] Implementation method 3.

[0063] In Implementation Method 2, the weak current command processing unit amplifies the high-frequency component of the voltage deviation ΔV using a high-frequency amplification unit, calculates and corrects the voltage deviation ΔV', and then uses a compensator to calculate the d-axis current command i based on the corrected voltage deviation ΔV'. d * This refers to the weak current command. In Implementation 3, the weak current command calculation unit uses a compensator to calculate the basic weak current command based on the voltage deviation ΔV, and uses a high-frequency amplification unit to amplify the high-frequency components of the basic weak current command to calculate the weak current command.

[0064] Figure 6 This is a structural diagram of the weak current command arithmetic unit according to this embodiment. The weak current command arithmetic unit 5 according to this embodiment is the same as the weak current command arithmetic unit in Embodiment 2, consisting of a high-frequency amplification unit 51, a subtractor 52, and a compensator 53. Figure 6 As shown, in the weak current command calculation unit 5 of this embodiment, the subtractor 52 calculates the current from the reference voltage value V. b Subtract the output voltage value V a The voltage deviation ΔV is calculated. Then, the compensator 53 calculates the d-axis current command i based on the voltage deviation ΔV. d0 *This refers to the basic weak current command. The high-frequency amplification unit 51 amplifies the basic weak current command i. d0 * The high-frequency components are used to calculate the d-axis current command i. d * This refers to a weak current command.

[0065] The control device for this permanent magnet synchronous motor is similar to that in Embodiment 1. It calculates a weak current command with amplified high-frequency components based on the difference between the reference voltage and the output voltage. Therefore, field weakening control can be performed to avoid voltage saturation. Furthermore, by amplifying the high-frequency components of the weak current command, this control device can make the weak current command change accordingly when the rotational speed changes drastically. Moreover, the control device for this embodiment can also make the weak current command change accordingly when the output voltage changes drastically due to a sudden change in the power supply voltage.

[0066] Implementation method 4.

[0067] In Embodiment 2, the weak current command processing unit amplifies the high-frequency component of the voltage deviation ΔV to calculate and correct the voltage deviation ΔV'. As described in Embodiment 1, this high-frequency amplification unit employs a phase-lead filter F(s) that amplifies the high-frequency component in a frequency band higher than a predetermined frequency. In Embodiment 4, the weak current command processing unit consists of a high-pass filter and a multiplier.

[0068] Figure 7 This is a structural diagram of the high-frequency amplification section of the weak current command arithmetic unit according to this embodiment. Furthermore, the structure of the weak current command arithmetic unit in this embodiment is the same as that in Embodiment 2. Figure 7 As shown, the high-frequency amplification unit 51 in this embodiment is composed of a high-pass filter 511 and a multiplier 512. The high-pass filter 511 extracts the high-frequency component ΔV of the voltage deviation ΔV. h Multiplier 512 multiplies the voltage deviation ΔV by the gain K. h The output corrected voltage deviation ΔV' is obtained by amplifying the high-frequency component of the voltage deviation ΔV. Gain K h The high-frequency component ΔV of the voltage deviation calculated by the high-pass filter 511. h To set. Usually, K is set. h =1, and when the high-frequency component of the voltage deviation ΔV h When the threshold is exceeded, K is set. h >1. In this embodiment, the weak current command calculation unit calculates the d-axis current command i based on the correction voltage deviation ΔV' output from the high-frequency amplification unit 51. d *This refers to a weak current command.

[0069] The control device for this permanent magnet synchronous motor is similar to that in Embodiment 2. It calculates a weak current command with amplified high-frequency components based on the difference between the reference voltage and the output voltage. Therefore, field weakening control can be performed to avoid voltage saturation. Furthermore, by amplifying the high-frequency components of the weak current command, this control device can make the weak current command change accordingly when the rotational speed changes drastically. Additionally, the control device for this embodiment can also make the weak current command change accordingly when the output voltage changes drastically due to a sudden change in the power supply voltage.

[0070] Furthermore, in this embodiment, variable gain is used as the means of amplifying high-frequency components in the high-frequency amplification section. In addition, in embodiment 2, a filter is used as the means of amplifying high-frequency components in the high-frequency amplification section. The means of amplifying high-frequency components in the high-frequency amplification section are not limited to variable gain and filters; pre-set mappings or the like can also be used.

[0071] Implementation method 5.

[0072] The control device for the permanent magnet synchronous motor in Embodiment 5 has the same structure as the control device for the permanent magnet synchronous motor in Embodiment 1. However, the output voltage value V... a Reference voltage value V b The integral gain K of the compensator of the weak current instruction arithmetic unit i Different. Since the modulation rate has the same meaning as the output voltage, in the control device of the permanent magnet synchronous motor in this embodiment, the output voltage value V is set based on the modulation rate. a and reference voltage value V b .

[0073] Reference voltage value V b Based on the reference modulation rate k * Given (V) b =k * Reference modulation rate k * The value is set to the maximum modulation rate k. max The following values. Here, let k be... * =k max This is to maximize the use of the power supply voltage. max Determined by the modulation method, k here max =1. Additionally, if a margin in the power supply voltage is desired, set k... * =k max ×0.9 is sufficient.

[0074] Output voltage value V a From the modulation rate k r Given (V)a =k r Modulation rate k r By three-phase voltage command v u * v v * v w * and power supply voltage V dc The calculation is performed using equations (5) and (6). The modulation rate k calculated using equation (5) is... r The molecule contains the output voltage value calculated using equation (1). Therefore, the modulation rate has the same meaning as the output voltage.

[0075] [Mathematical Expression 5]

[0076]

[0077] [Mathematical Expression 6]

[0078]

[0079] In addition, the integral gain K of the compensator i The result is given by equation (7). Additionally, the power supply voltage V... dc It can be a detected value or a pre-set value.

[0080] [Mathematical Expression 7]

[0081]

[0082] Therefore, even if the output voltage value V is set... a Reference voltage value V b and integral gain K i The modulation rate has the same meaning as the output voltage, so, similar to implementation 1, it can also amplify the high-frequency components of the weak current command.

[0083] Implementation method 6.

[0084] Embodiment 6 relates to an electric power steering device having a control device for a permanent magnet synchronous motor as described in Embodiments 1 to 5. Figure 8 This is a structural diagram of the electric power steering device involved in this embodiment. Figure 8 As shown, the electric power steering device 100 of this embodiment consists of a steering wheel 101, a steering shaft 102, a rack and pinion pair 103, a wheel 104, a permanent magnet synchronous motor 1 for assisting the driver in steering, a control device 2 for the permanent magnet synchronous motor, and a torque sensor 105 for detecting the driver's steering torque.

[0085] exist Figure 8In the electric power steering system 100 shown, the steering torque applied to the steering wheel 101 by the driver (not shown) is transmitted through the torsion bar of the torque sensor 105 and the steering shaft 102, and then through the rack and pinion pair 103 to the rack, thereby steering the wheels 104. The permanent magnet synchronous motor 1 is driven by the permanent magnet synchronous motor control device 2, generating an auxiliary force as output. This auxiliary force is transmitted to the steering shaft to reduce the steering torque applied by the driver during steering.

[0086] The auxiliary current command used to adjust the auxiliary force output of the permanent magnet synchronous motor 1 is calculated by the control device 2 of the permanent magnet synchronous motor based on the driver's steering torque detected by the torque sensor 105. For example, the control device 2 of the permanent magnet synchronous motor calculates the q-axis current command as a value proportional to the driver's steering torque. That is, the control device 2 of the permanent magnet synchronous motor sets the q-axis current command as the auxiliary current command.

[0087] In this configured electric power steering system 100, an auxiliary torque corresponding to the driver's steering input can be obtained from the permanent magnet synchronous motor 1. Furthermore, even if the driver makes a sudden turn causing a sharp change in the speed of the permanent magnet synchronous motor 1, the auxiliary current command changes accordingly, thus preventing a decrease in auxiliary torque. As a result, an electric power steering system that allows for comfortable steering can be realized.

[0088] As described above, the control device for the permanent magnet synchronous motor described in Embodiments 1 to 5 exhibits particularly significant effects when applied to electric power steering systems. In other devices, such as conveyor belts for transporting goods, since the transport is essentially at a fixed speed, abrupt changes in rotational speed do not occur. Furthermore, in construction machinery, since the drive mode is predetermined, it is easy to implement countermeasures such as additional feedforward compensation to accommodate abrupt changes in rotational speed. In contrast, in conventional electric power steering systems, abrupt changes in rotational speed occur due to unpredictable sudden steering, making it difficult to suppress the torque drop caused by such abrupt changes in rotational speed. By applying the control device for the permanent magnet synchronous motor described in Embodiments 1 to 5 to an electric power steering system, the torque drop caused by unpredictable abrupt changes in rotational speed can be suppressed.

[0089] Additionally, an example of the hardware of the control device 2 for the permanent magnet synchronous motor described in embodiments 1 to 5 is as follows: Figure 9As shown, it consists of a processor 111 and a storage device 112. Although the storage device 112 is not shown, it includes a volatile storage device such as random access memory and a non-volatile auxiliary storage device such as flash memory. Alternatively, an auxiliary storage device such as a hard disk can be used instead of flash memory. The processor 111 executes a program input from the storage device 112. In this case, the program is input from the auxiliary storage device to the processor 111 via the volatile storage device. Furthermore, the processor 111 can output data such as calculation results to the volatile storage device of the storage device 112, and can also save data to the auxiliary storage device via the volatile storage device.

[0090] This application describes various exemplary implementation methods and embodiments, but the various features, forms and functions described in one or more embodiments are not limited to the application of a specific embodiment, and can be applied to the embodiment alone or in various combinations.

[0091] Therefore, it can be assumed that numerous variations not illustrated are also included within the scope of the technology disclosed in this application. For example, this includes cases where at least one constituent element is modified, added to, or omitted, and cases where at least one constituent element is extracted and combined with constituent elements of other embodiments.

[0092] Label Explanation

[0093] 1 Permanent magnet synchronous motor, 2 Control device for permanent magnet synchronous motor, 3 Reference voltage value calculation unit, 4 Output voltage value calculation unit, 5 Weak current command calculation unit, 6 Voltage command calculation unit, 7 Power converter, 11 Angle detector, 51 High frequency amplifier, 52 Subtractor, 53 Compensator, 61 Coordinate transformation unit, 62 Voltage command generation unit, 511 High-pass filter, 512 Multiplier, 621 and 622 Subtractors, 623 and 624 PI controller, 100 Electric power steering device, 101 Steering wheel, 102 Steering shaft, 103 Gear rack pair, 104 Wheel, 105 Torque sensor, 111 Processor, 112 Storage device.

Claims

1. A control device for a permanent magnet synchronous motor, characterized in that, include: A reference voltage value calculation unit that calculates the reference voltage value based on the power supply voltage; Output voltage value calculation unit that calculates the output voltage value according to the voltage command; A weak current command calculation unit that calculates the d-axis current command, i.e., the weak current command, for field weakening control based on the reference voltage value and the output voltage value. A voltage command calculation unit that calculates the voltage command based on the weak current command; and A power converter that supplies power to a permanent magnet synchronous motor according to the voltage command. The weak current command processing unit calculates the weak current command with amplified high-frequency components based on the difference between the reference voltage value and the output voltage value.

2. The control device for a permanent magnet synchronous motor as described in claim 1, characterized in that, The weak current command processing unit includes: a high-frequency amplification unit that amplifies the high-frequency components of the output voltage value using a filter for amplifying high-frequency components, and performs calculations on the corrected output voltage value; a subtractor that calculates the difference, i.e., the voltage deviation, between the reference voltage value and the corrected output voltage value calculated by the high-frequency amplification unit; and a compensator that calculates the weak current command based on the voltage deviation calculated by the subtractor.

3. The control device for a permanent magnet synchronous motor as described in claim 1, characterized in that, The weak current command calculation unit includes: a subtractor that calculates the difference between the reference voltage value and the output voltage value, i.e., the voltage deviation; a high-frequency amplification unit that uses a filter for amplifying high-frequency components to amplify the high-frequency components of the voltage deviation and calculates the correction voltage deviation; and a compensator that calculates the weak current command based on the correction voltage deviation calculated by the high-frequency amplification unit.

4. The control device for a permanent magnet synchronous motor as described in claim 1, characterized in that, The weak current command calculation unit includes: a subtractor that calculates the difference between the reference voltage value and the output voltage value, i.e., the voltage deviation; a compensator that calculates the basic weak current command based on the voltage deviation; and a high-frequency amplification unit that amplifies the high-frequency components of the basic weak current command using a filter for amplifying high-frequency components, and calculates the weak current command.

5. The control device for a permanent magnet synchronous motor as described in any one of claims 2 to 4, characterized in that, The filter used to amplify high-frequency components is a phase-lead filter.

6. The control device for a permanent magnet synchronous motor as described in claim 3, characterized in that, The high-frequency amplification section includes a high-pass filter and a multiplier. The high-pass filter is used to extract the high-frequency component of the voltage deviation. The multiplier multiplies the voltage deviation by a gain set based on the high-frequency component of the voltage deviation extracted by the high-pass filter, and outputs a corrected voltage deviation.

7. The control device for a permanent magnet synchronous motor as described in any one of claims 1 to 4, characterized in that, The reference voltage value calculation unit sets the reference modulation rate calculated based on the power supply voltage as the reference voltage value, and the output voltage value calculation unit sets the modulation rate calculated based on the power supply voltage and the voltage command as the output voltage value.

8. The control device for a permanent magnet synchronous motor as described in claim 5, characterized in that, The reference voltage value calculation unit sets the reference modulation rate calculated based on the power supply voltage as the reference voltage value, and the output voltage value calculation unit sets the modulation rate calculated based on the power supply voltage and the voltage command as the output voltage value.

9. The control device for a permanent magnet synchronous motor as described in claim 6, characterized in that, The reference voltage value calculation unit sets the reference modulation rate calculated based on the power supply voltage as the reference voltage value, and the output voltage value calculation unit sets the modulation rate calculated based on the power supply voltage and the voltage command as the output voltage value.

10. An electric power steering device, characterized in that, It includes a permanent magnet synchronous motor that generates auxiliary torque to assist the driver's steering torque, and a control device for the permanent magnet synchronous motor as claimed in any one of claims 1 to 9.

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