Control device for a rotating electric machine and electric power steering device

Abstract

This invention provides a control device for a rotating electric motor and an electric power steering device, which can set the control gain for controlling the d-axis current command value based on the q-axis current deviation between the q-axis current command value and the q-axis current detection value, taking into account the responsiveness of the q-axis current. In the control device (10) of the rotating electric motor, the d-axis current command value (Ido) is changed based on the value obtained by multiplying the deviation between the q-axis current command value (Iqo) and the q-axis current detection value (Iqs), i.e., the q-axis current deviation (ΔIq_err), by the proportional gain (Kpid), and the proportional gain (Kpid) is changed inversely proportional to the rotational angular velocity (ω).

Description

Technical Field

[0001] This application relates to a control device for a rotating electric motor and an electric power steering device. Background Technology

[0002] In permanent magnet synchronous rotating motors, the linkage flux of the permanent magnets generates an induced voltage proportional to the rotor's rotational angular velocity. At high speeds, if the difference between the maximum applied voltage and the induced voltage decreases, the desired q-axis current cannot energize the windings, resulting in a drop in output torque. Therefore, under normal circumstances, during high-speed rotation, the d-axis current is increased in the negative direction to generate a flux in the windings that weakens the linkage flux of the permanent magnets, thus achieving field weakening control to reduce the induced voltage.

[0003] There are various methods for field weakening control. In Patent Document 1, the method involves proportional or integral control based on the deviation between the q-axis current command value and the q-axis current detection value, thereby increasing or decreasing the d-axis current and performing field weakening control.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 3559258 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] However, Patent Document 1 does not disclose a method for setting the control gain based on the control of the d-axis current command value based on the q-axis current deviation. Since the q-axis current moves along the voltage limiting ellipse as the d-axis current increases or decreases, the responsiveness of the q-axis current during field weakening control depends on the responsiveness of the control based on the d-axis current command value. The responsiveness of the q-axis current relates to the torque responsiveness and is therefore important for the performance of the rotating electrical machine.

[0009] Therefore, the purpose of this application is to provide a control device for a rotating electric motor and an electric power steering device, which can set the control gain for controlling the d-axis current command value based on the q-axis current deviation between the q-axis current command value and the q-axis current detection value, and taking into account the responsiveness of the q-axis current.

[0010] Technical means for solving technical problems

[0011] The control device for the rotating electric motor involved in this application controls a rotating electric motor having a stator equipped with multi-phase windings and a rotor equipped with magnets via a power converter. The control device for the rotating electric motor includes:

[0012] A current detection unit that detects the current flowing through the multiphase winding;

[0013] The current coordinate conversion unit converts the current detection value into the d-axis current detection value and the q-axis current detection value in a rotating coordinate system consisting of the d-axis determined in the direction of the magnetic pole position of the rotor and the q-axis determined in the direction that is 90 degrees ahead of the d-axis in electrical angle.

[0014] A current command value calculation unit calculates the current command value for the d-axis and the current command for the q-axis.

[0015] A voltage command value calculation unit that varies the voltage command values ​​of the d-axis and the q-axis to make the current detection value of the d-axis close to the current command value of the d-axis and the current detection value of the q-axis close to the current command value of the q-axis, and converts the voltage command values ​​of the d-axis and the q-axis into multi-phase voltage command values ​​based on the rotation angle; and

[0016] A switching control unit, based on the voltage command value of the multiphase, causes multiple switching elements of the power converter to turn on and off.

[0017] The current command value calculation unit changes the current command value of the d-axis based on the value obtained by multiplying the deviation between the current command value of the q-axis and the current detection value of the q-axis (i.e., the q-axis current deviation) by a proportional gain, and makes the proportional gain change inversely proportional to the rotational angular velocity of the rotor.

[0018] The electric power steering system involved in this application includes:

[0019] Control device for rotating electric machines;

[0020] The power converter;

[0021] The rotary motor; and

[0022] The driving force of the rotary motor is transmitted to the driving force transmission mechanism of the vehicle's steering device.

[0023] Invention Effects

[0024] According to the control device for the rotating electric machine and the electric power steering device involved in this application, when the q-axis current is limited by a voltage limiting ellipse, the response from the change in the d-axis current to the change in the q-axis current is proportional to the rotational angular velocity. By making the proportional gain used to calculate the d-axis current command value multiplied by the q-axis current deviation change inversely proportional to the rotational angular velocity, the characteristic of being proportional to the rotational angular velocity in the response from the d-axis current to the q-axis current can be counteracted. Therefore, the response from the q-axis current deviation to the q-axis current does not change according to the rotational angular velocity, making it easy to set the responsiveness of the q-axis current to the desired responsiveness and obtain the desired torque responsiveness. Attached Figure Description

[0025] Figure 1 This is a simplified structural diagram of the rotary electric machine, power converter, and control device involved in Embodiment 1.

[0026] Figure 2 This is a simplified block diagram of the control device involved in Embodiment 1.

[0027] Figure 3 This is a hardware structure diagram of the control device involved in Implementation Method 1.

[0028] Figure 4 This is a diagram illustrating the field weakening control involved in Implementation Method 1.

[0029] Figure 5 This is a block diagram of the d-axis current command value change unit involved in Implementation Method 1.

[0030] Figure 6 This is a block diagram used to explain the setting of the proportional gain involved in Implementation Method 1.

[0031] Figure 7 It is a Bode plot of the number of open-loop transfer loops from the q-axis current offset deviation to the q-axis current detection value, as described in Implementation Method 1.

[0032] Figure 8 This is a Bode plot of the number of open-loop transfer loops from the q-axis current offset deviation to the q-axis current detection value, as involved in the comparative example.

[0033] Figure 9 This is a block diagram of the d-axis current command value change unit involved in Embodiment 2. Detailed Implementation

[0034] 1. Implementation Method 1

[0035] The control device 10 of the rotary electric machine according to Embodiment 1 (hereinafter referred to as the control device 10) will be described with reference to the accompanying drawings. Figure 1This is a simplified structural diagram of the rotary motor 1, power converter 4, and control device 10 involved in this embodiment. In this embodiment, the rotary motor 1 serves as the driving force source for the electric power steering device 100, and the rotary motor 1, power converter 4, and control device 10 constitute the electric power steering device 100.

[0036] 1-1. Rotary motor 1

[0037] The rotary electric motor 1 includes a stator and a rotor disposed radially inside the stator. The stator has multi-phase windings (in this example, three-phase windings Cu, Cv, and Cw of phases U, V, and W). Permanent magnets are provided on the stator, and the rotary electric motor 1 is a permanent magnet type synchronous rotary electric motor. It is configured as a surface magnet type with permanent magnets on the outer circumference of the rotor. Alternatively, it can be configured as an embedded magnet type with permanent magnets inside the rotor. The three-phase windings can be star-connected or delta-connected.

[0038] The rotor includes a rotation sensor 2 for detecting the rotation angle of the rotor. The rotation sensor 2 may use a rotary transformer, encoder, MR sensor, etc. The output signal of the rotation sensor 2 is input to the control device 10. Alternatively, as described later, a sensorless structure that estimates the angle based on current information may be used instead of the rotation sensor 2.

[0039] 1-2. Power Converter 4

[0040] An inverter is used as power converter 4. Alternatively, a power converter other than an inverter, such as a matrix converter, can also be used as power converter 4.

[0041] Inverter 4 is provided with three sets of series circuits (branches) corresponding to each of the three phases. Each series circuit is connected in series with a positive-side switching element SP connected to the positive side of DC power supply 3 and a negative-side switching element SN connected to the negative side of DC power supply 3. Then, the connection point of the two switching elements in the series circuit of each phase is connected to the winding of the corresponding phase.

[0042] Specifically, in the U-phase series circuit, the switching element SCu on the positive side of U-phase and the switching element SNu on the negative side of U-phase are connected in series, and the connection point of the two switching elements is connected to the U-phase winding Cu. In the V-phase series circuit, the switching element SPv on the positive side of V-phase and the switching element SNv on the negative side of V-phase are connected in series, and the connection point of the two switching elements is connected to the V-phase winding Cv. In the W-phase series circuit, the switching element SPw on the positive side of W-phase and the switching element SNw on the negative side of W-phase are connected in series, and the connection point of the two switching elements is connected to the W-phase winding Cw. The smoothing capacitor 5 is connected between the positive and negative sides of the DC power supply 3.

[0043] For the switching elements, IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), and bipolar transistors with diodes connected in reverse parallel are used. The gate terminals of each switching element are connected to the control device 10 via gate drive circuits, etc. Each switching element is turned on or off by switching signals GPU to GNw output from the control device 10.

[0044] The DC power supply 3 outputs a DC voltage Vdc to the inverter 4. In this embodiment, the DC voltage Vdc is set to 12V. The DC power supply 3 can be any device that outputs a DC voltage Vdc, such as a battery, DC-DC converter, diode rectifier, or PWM rectifier. The DC power supply 3 is equipped with a voltage sensor to detect the DC voltage Vdc, and the output signal of the voltage sensor can be input to the control device 10. The control device 10 can use the detected DC voltage Vdc for control.

[0045] A current sensor 6 is provided to detect the current flowing through each phase winding. The current sensor 6 is configured as a shunt resistor or a Hall element, etc. The output signal of the current sensor 6 is input to the control device 10.

[0046] In this embodiment, the current sensor 6 can also be set in the series circuit of two switching elements in each phase. The U-phase resistor Ru, the V-phase resistor Rv, and the W-phase resistor Rw are connected in series to the negative side of the switching element SN on the negative side of each phase. The potential difference between the two ends of the three-phase resistors Ru, Rv, and Rw is detected by amplifiers 21, 22, and 23, and the potential difference is input to the control device 10.

[0047] Alternatively, the current sensor 6 can be installed on the wires connecting the series circuit of the two switching elements of each phase and the coils of each phase. Or, the current sensor can be installed on the wires connecting the inverter 4 and the DC power supply 3, and the current of each phase winding can be detected using the known "bus 1 shunt method".

[0048] 1-3. Electric power steering system 100

[0049] The electric power steering system 100 includes a control device 10 for a rotary motor, an inverter 4, a rotary motor 1, and a drive force transmission mechanism 101 that transmits the driving force of the rotary motor 1 to the steering system 102 of the vehicle.

[0050] The rotor shaft of the rotary motor 1 is connected to the steering device 102 of the wheel 103 via a drive force transmission mechanism 101. For example, the electric power steering device 100 includes a steering wheel 104 that the driver rotates left and right, a shaft 105 connected to the steering wheel 104 and transmitting the steering torque of the steering wheel 104 to the wheel 103 via the steering device 102, a torque sensor 106 mounted on the shaft 105 and detecting the steering torque Ts of the steering wheel 104, and a worm gear mechanism connecting the rotor shaft of the rotary motor 1 to the shaft 105, etc., as part of the drive force transmission mechanism 101. The output signal of the torque sensor 106 is input to the control device 10 (input circuit 92).

[0051] 1-4. Control device 10

[0052] The control device 10 controls the rotating motor 1 via the inverter 4. For example... Figure 2 As shown, the control device 10 includes a rotation detection unit 31, a current detection unit 32, a current coordinate conversion unit 33, a current command value calculation unit 34, a voltage command value calculation unit 35, and a switch control unit 36. Each function of the control device 10 is implemented by the processing circuitry provided by the control device 10. Specifically, the control device 10 is as follows... Figure 3 As shown, the processing circuit includes: an arithmetic processing unit 90 (computer) such as a CPU (Central Processing Unit); a storage device 91 for exchanging data with the arithmetic processing unit 90; an input circuit 92 for inputting external signals to the arithmetic processing unit 90; and an output circuit 93 for outputting signals from the arithmetic processing unit 90 to the outside.

[0053] The processing unit 90 can include ASIC (Application Specific Integrated Circuit), IC (Integrated Circuit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), various logic circuits, and various signal processing circuits. Furthermore, the processing unit 90 can also include multiple processing units of the same or different types to share the execution of various processes. The storage unit 91 can include RAM (Random Access Memory) configured to read and write data from the processing unit 90, or ROM (Read-Only Memory) configured to read data from the processing unit 90. The input circuit 92 is connected to various sensors and switches such as the rotation sensor 2, current sensor 6, and torque sensor 106, and includes an A / D converter that inputs the output signals of these sensors and switches to the processing unit 90. The output circuit 93 is connected to electrical loads such as a gate drive circuit that drives the switching elements to turn on and off, and includes a drive circuit that outputs control signals from the arithmetic processing unit 90 to these electrical loads.

[0054] Furthermore, the functions of each control unit 31 to 36 in the control device 10 are achieved by the arithmetic processing unit 90 executing software (programs) stored in a storage device 91 such as a ROM, and in cooperation with other hardware of the control device 10 such as the storage device 91, the input circuit 92, and the output circuit 93. Additionally, the setting data such as the internal resolution and control gain used by each control unit 31 to 36 are stored as part of the software (program) in the storage device 91 such as a ROM. The functions of the control device 10 will be described in detail below.

[0055] 1-4-1. Basic Control

[0056] <Rotation Detection Unit 31>

[0057] The rotation detection unit 31 detects the rotor's magnetic pole position θ (rotor rotation angle θ) and rotational angular velocity ω at an electrical angle. In this embodiment, the rotation detection unit 31 detects the rotor's magnetic pole position θ (rotation angle θ) and rotational angular velocity ω based on the output signal of the rotation sensor 2. In this embodiment, the magnetic pole position is set in the direction of the N pole of the permanent magnet provided on the rotor. The rotational angular velocity ω is calculated by differentiating the rotation angle θ. Alternatively, the rotation detection unit 31 can be configured to estimate the rotation angle (magnetic pole position) based on current information obtained by superimposing harmonic components onto the current command value, without using a rotation sensor (a so-called sensorless method).

[0058] <Current Detection Unit 32>

[0059] The current detection unit 32 detects the currents Ius, Ivs, and Iws flowing through the three-phase windings based on the output signal of the current sensor 6. Specifically, the current detection unit 32 detects the current Ius flowing through the U-phase winding, the current Ivs flowing through the V-phase winding, and the current Iws flowing through the W-phase winding, all based on the output signal of the current sensor 6. Furthermore, the current sensor 6 is configured to detect the winding currents of two phases; the winding current of the remaining phase can be calculated based on the detected values ​​of the two phase winding currents. For example, the current sensor 6 can detect the winding currents Ivs and Iws of phases V and W, and the winding current Ius of phase U can be calculated using Ius = -Ivs - Iws.

[0060] <Current Coordinate Transformation Section 33>

[0061] The current coordinate conversion unit 33 converts the current detection values ​​Ius, Ivs, and Iws of the three-phase windings into the d-axis current detection value Ids and the q-axis current detection value Iqs based on the rotation angle θ. In this embodiment, the current coordinate conversion unit 33 performs three-phase two-phase conversion and rotation coordinate conversion on the current detection values ​​Ius, Ivs, and Iws of the three-phase windings based on the rotation angle θ, as shown in the following formula, thereby converting them into the d-axis and q-axis current detection values ​​Ids and Iqs.

[0062] [Mathematical formula 1]

[0063]

[0064] In addition, the d-axis is determined in the direction of the magnet's magnetic pole (N pole), and the q-axis is determined in the direction that is 90 degrees ahead of the d-axis in terms of electrical angle.

[0065] <Voltage Command Value Calculation Unit 35>

[0066] The voltage command value calculation unit 35 includes a current control unit 351, a q-axis voltage limiting unit 352, and a voltage coordinate transformation unit 353. The current control unit 351 changes the d-axis voltage command value Vdo and the q-axis voltage command value Vqo so that the d-axis current detection value Ids approaches the d-axis current command value Ido, and the q-axis current detection value Iqs approaches the q-axis current command value Iqo. The calculation of the d-axis and q-axis current command values ​​Ido and Iqo performed by the current command value calculation unit 34 will be explained later. For example, the voltage command value calculation unit 35 performs proportional-integral control as shown in the following formula.

[0067] [Mathematical Expression 2]

[0068]

[0069]

[0070] Here, Kd and Kq are the proportional gains, Td and Tq are the integration times, and s is the Laplace operator.

[0071] Alternatively, feedforward control can be implemented to prevent interference between the d-axis and q-axis currents. That is, "-ω×Lq×Iqo" can be added to the d-axis voltage command value Vdo, and "ω×(Ld×Ido+φ)" can be added to the q-axis voltage command value Vqo. Lq is the q-axis inductance, Ld is the d-axis inductance, and φ is the linkage flux between the magnetomotive force of the magnet and the winding.

[0072] The q-axis voltage limiting unit 352 limits the q-axis voltage command value Vqo based on the DC voltage Vdc and the d-axis voltage command value Vdo, so that the three-phase voltage command values ​​Vuo, Vvo, and Vwo do not exceed the range of the maximum applied voltage Vdc / Km corresponding to the DC voltage Vdc. For example, as shown in the following formula, the q-axis voltage limiting unit 352 imposes an upper limit and a lower limit on the q-axis voltage command value Vqo, so that the q-axis voltage command value Vqo does not exceed the upper limit value VqlmtH and the lower limit value VqlmtL calculated based on the maximum applied voltage Vdc / Km and the d-axis voltage command value Vdo, and calculates the values ​​after the upper and lower limits as the final q-axis voltage command value Vqo.

[0073] [Mathematical Expression 3]

[0074]

[0075] Here, Km is a coefficient corresponding to the voltage utilization rate, as shown in the following formula, which is set according to whether there is modulation such as third harmonic superposition.

[0076] [Mathematical Expression 4]

[0077]

[0078] According to this structure, the d-axis voltage command value Vdo is preferentially varied along the voltage limiting circle corresponding to the maximum applied voltage Vdc / Km, while the q-axis voltage command value Vqo is preferentially varied. Thus, as described later, corresponding to the structure in field weakening control that preferentially varies the d-axis current command value Ido, the d-axis voltage command value Vdo and the d-axis current Id can be preferentially varied.

[0079] The q-axis voltage limiting unit 352 can perform low-pass filtering on the d-axis voltage command value Vdo used in the limiting process of the q-axis voltage command value Vqo. Vibration of the d-axis voltage command value Vdo causes vibration of the q-axis voltage command value Vqo. As described above, by using a low-pass filtered value for the d-axis voltage command value Vdo, the vibration of the q-axis voltage command value Vqo can be suppressed, thereby reducing the vibration and noise of the rotating motor.

[0080] The voltage coordinate conversion unit 353 converts the voltage command values ​​Vdo and Vqo of the d-axis and q-axis into three-phase voltage command values ​​Vuo, Vvo, and Vwo based on the rotation angle θ. In this embodiment, the voltage coordinate conversion unit 353 performs fixed coordinate conversion and two-phase to three-phase conversion on the voltage command values ​​Vdo and Vqo of the d-axis and q-axis based on the rotation angle θ, as shown in the following formula, and converts them into three-phase voltage command values ​​Vuo, Vvo, and Vwo.

[0081] [Mathematical Expression 5]

[0082]

[0083] In addition, in order to improve voltage utilization, the voltage coordinate conversion unit 353 can apply known modulation methods such as two-phase modulation and third harmonic superposition to the three-phase voltage command values ​​Vuo, Vvo, and Vwo.

[0084] <Switch Control Unit 36>

[0085] The switching control unit 36 ​​controls the on / off switching of multiple switching elements in the inverter 4 based on the three-phase voltage command values ​​Vuo, Vvo, and Vwo. The switching control unit 36 ​​uses known carrier comparison PWM or space vector PWM.

[0086] When using carrier comparison PWM, the switch control unit 36 ​​compares the carrier with each of the three-phase voltage command values ​​Vuo, Vvo, and Vwo, and turns multiple switching elements on and off based on the comparison results. The carrier is set to a triangular wave that oscillates around 0 with an amplitude of half the DC voltage value Vdc / 2 during the PWM period Tc. For each phase, when the carrier is lower than the voltage command value, the switch control unit 36 ​​turns on the switching signal GP of the positive-side switching element and turns on the positive-side switching element; when the carrier CA exceeds the voltage command value, it turns off the switching signal GP of the positive-side switching element and turns off the positive-side switching element. On the other hand, for each phase, when the carrier is lower than the voltage command value, the switch control unit 36 ​​turns off the switching signal GN of the negative-side switching element and turns off the negative-side switching element; when the negative-side switching element is turned off and the carrier CA exceeds the voltage command value, it turns on the switching signal GN of the negative-side switching element and turns on the negative-side switching element. In addition, for each phase, a short-circuit prevention period (dead time) can be set between the conduction period of the switching element on the positive side and the conduction period of the switching element on the negative side to turn off both the switching elements on the positive and negative sides.

[0087] When using space vector PWM, the switch control unit 36 ​​generates a voltage command vector based on the three-phase voltage command values ​​Vuo, Vvo, and Vwo, determines the output time allocation of the seven basic voltage vectors in the PWM cycle based on the voltage command vector, and generates a switching signal that turns each switching element on and off in the PWM cycle based on the output time allocation of the seven basic voltage vectors.

[0088] 1-4-2. Current Command Value Calculation Unit 34

[0089] The current command value calculation unit 34 calculates the d-axis current command value Ido and the q-axis current command value Iqo. In this embodiment, the voltage command value calculation unit 34 includes a basic current command value calculation unit 341, a d-axis current command value change unit 342, a d-axis current command value limiting unit 343, and a q-axis current command value limiting unit 344.

[0090] 1-4-2-1. Basic Current Command Value Calculation Unit 341

[0091] The basic current command value calculation unit 341 calculates the basic current command value Idob for the d-axis and the basic current command value Iqob for the q-axis. In this embodiment, the basic current command value calculation unit 341 detects the driver's steering torque Ts based on the output signal of the torque sensor 106. The basic current command value calculation unit 341 sets the basic current command value Iqob for the q-axis based on the steering torque Ts, as shown in the following formula, and sets the basic current command value Idob for the d-axis to 0. That is, Id=0 control is performed. In Id=0 control, the basic current command value Idob for the d-axis is set to 0. Id=0 control is suitable for the surface magnet type rotary motor of this embodiment. In the surface magnet type rotary motor, the d-axis inductance Ld and the q-axis inductance Lq are approximately equal, and the torque changes proportionally to the q-axis current Iq.

[0092] [Mathematical Expression 6]

[0093]

[0094] Here, Ka is a constant, but it can also vary depending on the steering torque Ts and the vehicle's speed. Furthermore, the basic current command value Iqob for the q-axis can be set based on known compensation control corresponding to the steering conditions.

[0095] In the case of rotary motors with embedded magnets, the basic current command values ​​Idob and Iqob for the d-axis and q-axis can be set using other control methods such as maximum torque current control, instead of Id=0 control. In maximum torque current control, the basic current command values ​​Idob and Iqob for the d-axis and q-axis that maximize the torque for the same current are calculated.

[0096] 1-4-2-2. Magnetic Weakening Control

[0097] <Principles of Field Weakening Control>

[0098] The voltage equation for a rotating electric machine is as shown in equation (1).

[0099] [Mathematical Expression 7]

[0100]

[0101] Here, Vd is the applied voltage along the d-axis, Vq is the applied voltage along the q-axis, Id is the current along the d-axis, Iq is the current along the q-axis, s is the Laplace operator, R is the winding resistance, φ is the AC flux of the rotor magnet, Ld is the d-axis inductance, and Lq is the q-axis inductance.

[0102] The term multiplied by the rotational angular velocity ω of equation (7) is shown in the following equation, which is the term of the induced voltage generated in the winding. The induced voltage Vdi on the d-axis and the induced voltage Vqi on the q-axis increase with the increase of the rotational angular velocity ω.

[0103] [Mathematical Expression 8]

[0104]

[0105] The induced voltage Vi is as shown in the following formula. When the induced voltage Vi approaches the maximum applicable voltage Vdc / Km, the amount of winding current that can be energized decreases, and therefore the torque of the rotating motor decreases.

[0106] [Mathematical Expression 9]

[0107]

[0108] Therefore, as can be seen from equation (9), field weakening control is generally performed. This field weakening control generates a flux that cancels the linkage flux φ of the rotor by increasing the d-axis current Id in the negative direction, thereby reducing the induced voltage Vi and increasing the winding current.

[0109] Next, as shown in the following equation, the winding current is limited by the maximum current value Imax that can flow through the winding. Within the current limiting circle shown in equation (10), it is necessary to control the d-axis current Id and the q-axis current Iq.

[0110] [Mathematical Expression 10]

[0111] I d 2 +I q 2 ≤I max 2 …(10)

[0112] Furthermore, as shown in the following equation, the d-axis current Id and the q-axis current Iq are limited such that the voltage limiting ellipse is consistent with the maximum applicable voltage Vdc / Km of the induced voltage Vi.

[0113] [Mathematical Expression 11]

[0114]

[0115] like Figure 4 As shown, under a selected acceleration ω in the field weakening control region, the d-axis current Id and q-axis current Iq that yield the desired torque become the intersection of the voltage limiting ellipse and the q-axis current command value Iqo. When the q-axis current command value Iqo is limited by the current limiting circle, it becomes the intersection of the voltage limiting ellipse and the current limiting circle.

[0116] However, as in the past, in order to set such optimal d-axis and q-axis current command values ​​in a feedforward manner, high-precision information on the d-axis and q-axis inductances Ld and Lq, as well as the rotor linkage flux φ, related to the voltage limiting ellipse, is required. However, without access to this high-precision information, it is impossible to set the optimal d-axis and q-axis current command values ​​in a feedforward manner. Alternatively, if the d-axis and q-axis inductances Ld and Lq, as well as the rotor linkage flux φ, vary due to historical changes or temperature characteristics, the accuracy of the d-axis and q-axis current command value setting deteriorates.

[0117] On the other hand, in the technology of Patent Document 1, the d-axis current command value is increased or decreased based on the d-axis current deviation between the d-axis current command value and the d-axis current detection value through proportional control or integral control. In the technology of Patent Document 1, due to the increase in rotational angular velocity ω, the current limiting ellipse narrows. When the d-axis current is limited by the voltage limiting ellipse, the negative increase in the d-axis current increases due to the d-axis current deviation. Therefore, field weakening control can be performed without using information about the inductor and rotor linkage flux φ. However, the technology of Patent Document 1 does not disclose a method for setting the control gain of the d-axis current command value based on the d-axis current deviation. Since the d-axis current moves along the voltage limiting ellipse according to the increase or decrease of the d-axis current, the responsiveness of the d-axis current during field weakening control depends on the responsiveness of the d-axis current command value control. The responsiveness of the d-axis current relates to the torque responsiveness and is therefore important for the performance of the rotating machine.

[0118] Therefore, a control device is required that can set the control gain for controlling the d-axis current command value by taking into account the responsiveness of the q-axis current based on the q-axis current deviation between the q-axis current command value and the q-axis current detection value.

[0119] <d-axis current command value change section 342>

[0120] Figure 5 The diagram shows a block diagram of the d-axis current command value changing unit 342. The d-axis current command value changing unit 342 changes the d-axis current command value Ido based on the deviation between the q-axis current command value Iqo and the q-axis current detection value Iqs (i.e., the q-axis current deviation ΔIq_err) multiplied by the proportional gain Kpid. Then, as described later, the proportional gain Kpid changes inversely proportional to the rotational angular velocity ω.

[0121] In this embodiment, the configuration involves both proportional and integral control based on the q-axis current deviation ΔIq_err. Alternatively, integral control may not be performed.

[0122] As shown in the following formula, the d-axis current command value change unit 342 performs proportional and integral control based on the q-axis current deviation ΔIq_err obtained by subtracting the q-axis current detection value Iqs from the q-axis current command value Iqo. It calculates the d-axis current command value change ΔIdo, and adds the d-axis current command value change ΔIdo to the basic d-axis current command value Idob to calculate the d-axis current command value Ido. Depending on whether the q-axis current command value Iqo is positive or negative, it switches whether the proportional gain Kpid is multiplied by -1 or +1.

[0123] [Mathematical Expression 12]

[0124]

[0125] Here, Kpid is the proportional gain used for calculating the d-axis current command value, set to a positive value; Tiid is the integration time used for calculating the d-axis current command value; and s is the Laplace operator. The following explains how to set the proportional gain Kpid and the integration time Tiid used for calculating the d-axis current command value.

[0126] <Setting the proportional gain Kpid>

[0127] The proportional gain Kpid in equation (12) can be set to a positive value, but a preferred setting method considering responsiveness will be described below. The d-axis current command value change unit 342 causes the proportional gain Kpid used for calculating the d-axis current command value to change inversely proportional to the rotational angular velocity ω. In this embodiment, as shown in the following equation, the value obtained by dividing the target response angular frequency ωido by the rotational angular velocity ω is set as the proportional gain Kpid. The target response angular frequency ωido is the target response angular frequency of the feedback control system that changes the d-axis current command value Ido according to the q-axis current deviation ΔIq_err and reduces the absolute value of the q-axis current deviation ΔIq_err.

[0128] [Mathematical Expression 13]

[0129]

[0130] The target response angular frequency ωido can be set to a value larger than R / Lq. If set in this way, the convergence time (time constant) of the q-axis current deviation ΔIq_err is shorter than the circuit's time constant Lq / R. Therefore, in the field weakening control region, the current command values ​​Ido and Iqo of the d-axis and q-axis can change more rapidly relative to changes in rotational angular velocity and required torque, thus changing the output torque. As in this embodiment, when the rotary motor is used as an auxiliary drive source for the electric power steering device 100, for example, when the target response angular frequency ωido is set to a value between 250 [rad / s] and 1200 [rad / s], a good steering feel can be obtained.

[0131] The integration time Tiid in equation (12) can be set, for example, to the circuit's time constant Lq / R. As shown in the following equation, the integration gain Kiiq becomes Kpid / Tiid. Thus, according to equation (13), the integration gain Kiiq also changes inversely proportional to the rotational angular velocity ω. For example, the integration gain Kiiq is set to the value obtained by multiplying the target response angular frequency ωido by the winding resistance R, and then dividing by the rotational angular velocity ω and the inductance Lq.

[0132] [Mathematical Expression 14]

[0133]

[0134]

[0135] If we extract the formula for the q-axis voltage Vq from the voltage equation of equation (7), replace Vq with Vqo, and replace Id and Iq with Ids and Iqs, then it becomes the following formula.

[0136] [Mathematical Expression 15]

[0137]

[0138] If we solve equation (15) for the current detection value Iqs on the q-axis, we get the following equation.

[0139] [Mathematical Expression 16]

[0140]

[0141] When performing field weakening control, the voltage command value Vqo of the q-axis becomes consistent with the upper limit value VqlmtH or the lower limit value VqlmtL based on the voltage limit circle. Therefore, the control of the current detection value Iqs of the q-axis based on the operation of the voltage command value Vqo of the q-axis is not considered, but the control of the current detection value Iqs of the q-axis based on the operation of the current detection value Ids of the d-axis is considered. Thus, if the terms Vqo and ωφ in equation (16) are ignored, equation (16) becomes the following equation.

[0142] [Mathematical Expression 17]

[0143]

[0144] According to equation (17), the number of transfer loops Gp(s) from the current detection value Ids on the d-axis to the current detection value Iqs on the q-axis becomes as follows.

[0145] [Mathematical Expression 18]

[0146]

[0147] Therefore, it can be seen that the change in the current detection value Iqs of the q-axis caused by the operation of the current detection value Ids of the d-axis increases proportionally to the rotational angular velocity ω.

[0148] If the transfer function Gp(s) is used, the control system is as follows: Figure 6 The block diagram is shown below. The transfer function Gc(s) from the q-axis current deviation ΔIq_err to the d-axis current command value Ido is given by equations (12) and (13) as follows. Wherein, the integration time Tiid is set to Lq / R.

[0149] [Mathematical Expression 19]

[0150]

[0151] The transfer function Gd(s) from the d-axis current command value Ido to the d-axis current detection value Ids is expressed by the following equation. Here, ωids is the target response angular frequency of the d-axis current feedback control.

[0152] [Mathematical Expression 20]

[0153]

[0154] Preferably, the target response angular frequency ωids of the d-axis current feedback control is set sufficiently high compared to the target response frequency ωido of the d-axis current command value. ωids is obtained by using the d-axis proportional gain Kd from equation (2) as Kd / Ld. Therefore, the d-axis proportional gain Kd can be set to a value larger than ωido × Ld. For example, preferably, the d-axis proportional gain Kd can be set to a value larger than 3 × ωido × Ld, and more preferably, the d-axis proportional gain Kd can be set to a value larger than 5 × ωido × Ld. By setting the d-axis proportional gain Kd in this way, it can be considered that Gd(S) ≈ 1.

[0155] [Mathematical Expression 21]

[0156]

[0157] As described above, the open-loop transfer function Gop(s) from the q-axis current deviation ΔIq_err to the q-axis current sensing value Iqs is expressed by the following equation. Here, we assume that the d-axis inductance Ld is approximately equal to the q-axis inductance Lq, and Gd(s)≈1 for simplification.

[0158] [Mathematical Expression 22]

[0159]

[0160] Equation (22) is a simple integral characteristic and does not depend on the rotational angular velocity ω. When plotting the Bode plot, as shown... Figure 7 In this way, the gain slope is a constant value of -20dB / dec, which becomes 0dB at the angular frequency = ωido.

[0161] Therefore, as shown in the following equation, the closed-loop transfer function Gfb(s) of the change in the q-axis current detection value Iqs relative to the change in the q-axis basic current command value Iqob becomes a first-order delay with a time constant that is the reciprocal of the target response angular frequency ωido. Thus, in field weakening control, as shown in equation (13), the proportional gain Kpid used for calculating the d-axis current command value is made to vary inversely with the rotational angular velocity ω, thereby setting the response of the change in the q-axis current detection value Iqs relative to the change in the q-axis basic current command value Iqob to a first-order delay with a time constant that is not affected by the rotational angular velocity ω and has the reciprocal of the target response angular frequency ωido. Therefore, by setting the target response angular frequency ωido, the desired torque responsiveness can be obtained. Thus, the steering feel of the electric power steering system 100 is improved.

[0162] [Mathematical Expression 23]

[0163]

[0164] Unlike equation (13), the case where the proportional gain Kpid used for calculating the d-axis current command value is not set to a fixed value according to the rotational angular velocity ω will be explained. In this case, in equation (22), the ω term in Gp(s) is not canceled by the 1 / ω term in Gc(s) without using the proportional gain Kpid. Therefore, as shown in the following equation, the number of open-loop transfer loops Gop(s) becomes proportional to ω.

[0165] [Mathematical Expression 24]

[0166]

[0167] Here, K is a constant. To obtain the same properties as in equation (22) at ω = ωmd, K is set to 1 / ωmd. Figure 8 As shown in the Bode plots for ω = 0.5 × ωmd, ω = 1 × ωmd, and ω = 2 × ωmd, if the rotational angular velocity ω changes from ωmd, the response changes by a factor of ω / ωmd. In the case of ω = 1 × ωmd, the response of the open-loop transfer function Gop(s) becomes ωido, thus obtaining the desired response. However, in the case of ω = 2 × ωmd, the response of Gop(s) becomes twice, which, while having the advantage of improved responsiveness, also doubles the amount of noise component feedback contained in the q-axis current detection value Iqs, potentially increasing abnormal noise from the rotating motor. On the other hand, in the case of ω = 0.5 × ωmd, the response of Gop(s) becomes 0.5 times, the response of the q-axis current deteriorates, and the torque response worsens. Therefore, the torque response varies with the rotational angular velocity ω, potentially worsening the steering feel of the electric power steering system 100.

[0168] <Upper and lower limits of the d-axis current command value Ido>

[0169] As shown in the following formula, the d-axis current command value limit 343 limits the d-axis current command value Ido to an upper limit through an upper limit limit value IdlmtH, and to a lower limit through a lower limit limit value IdlmtL. The upper limit limit value IdlmtH is set as the basic d-axis current command value Idob. The lower limit limit value IdlmtL is set as a negative limit value to prevent irreversible demagnetization of the rotor's permanent magnets.

[0170] [Mathematical Expression 25]

[0171]

[0172] In cases where the rotational angular velocity ω is below the base rotational angular velocity, Ido can be forcibly set to Idob in areas where field weakening control is not required.

[0173] <q-axis current command value limiting unit 344>

[0174] The q-axis current command value limiting unit 344 limits the q-axis current command value Iqo based on the maximum current value Imax and the d-axis current command value Ido, so that the current supplied to the three-phase winding does not exceed the range of the maximum current value Imax that can be supplied to the three-phase winding. For example, as shown in the following formula, the q-axis current command value limiting unit 344 applies upper and lower limits to the basic q-axis current command value Iqob, so that the basic q-axis current command value Iqob does not exceed the upper limit value IqlmtH and the lower limit value IqlmtL calculated based on the maximum current value Imax and the d-axis current command value Ido, and calculates the values ​​after the upper and lower limits as the q-axis current command value Iqo. This limiting process is a process that limits the d-axis and q-axis current command values ​​Iqo and Ido to the range of the current limiting circle of the maximum current value Imax.

[0175] [Mathematical Expression 26]

[0176]

[0177] According to this structure, when the basic current command value Iqob on the q-axis is restricted to a current limiting circle corresponding to the maximum current value Imax, the current command value Ido on the d-axis can be preferentially varied along the current limiting circle corresponding to the maximum current value Imax, while the current command value Iqo on the q-axis can be preferentially varied. Therefore, in field weakening control, the current command value Ido on the d-axis can be preferentially varied, and the field weakening flux can be optimized.

[0178] 2. Implementation Method 2

[0179] The control device 10 according to Embodiment 2 will be described. Descriptions of structural parts identical to those in Embodiment 1 are omitted. The basic structures of the rotary motor 1, power converter 4, and control device 10 according to this embodiment are the same as in Embodiment 1, but the calculation method for the q-axis current deviation ΔIq_err differs from that in Embodiment 1. Figure 9 The diagram shows a block diagram of the d-axis current command value change unit 342.

[0180] In this embodiment, the d-axis current command value change unit 342 calculates the q-axis current deviation ΔIq_err by the deviation between the offset q-axis current command value Iqoffo obtained by reducing the absolute value of the q-axis current command value Iqo by the q-axis offset value ΔIqoff and the q-axis current detection value Iqs.

[0181] As shown in the following formula, when the q-axis current command value Iqo is positive, the d-axis current command value change unit 342 calculates the deviation between the offset q-axis current command value Iqoffo (obtained by subtracting the positive q-axis offset value ΔIqoff from the q-axis current command value Iqo) and the q-axis current detection value Iqs as the q-axis current deviation ΔIq_err. On the other hand, when the q-axis current command value Iqo is negative, the d-axis current command value change unit 342 calculates the deviation between the offset q-axis current command value Iqoffo (obtained by adding the q-axis offset value ΔIqoff to the q-axis current command value Iqo) and the q-axis current detection value Iqs as the q-axis current deviation ΔIq_err. Similar to formula (12) in Embodiment 1, the d-axis current command value Ido is changed based on the value obtained by multiplying the q-axis current deviation ΔIq_err by the proportional gain Kpid.

[0182] [Mathematical Expression 27]

[0183]

[0184] According to this structure, when the q-axis current is limited by the voltage limiting ellipse, the negative increase of the d-axis current command value Ido is adjusted to move to the intersection of the voltage limiting ellipse and the straight line obtained by decreasing or increasing the q-axis offset value ΔIqoff compared to the q-axis current command value Iqo. At this time, the q-axis current detection value Iqs being lower or higher than the q-axis current command value Iqo is equivalent to the q-axis offset value ΔIqoff. Therefore, the q-axis voltage command value Vqo can be attached to the upper limit value VqlmtH or the lower limit value VqlmtL based on the voltage limiting circle, maintaining the voltage utilization rate at its maximum. Furthermore, even when the amplitude of the noise component of the q-axis offset value ΔIqoff is larger than that of the q-axis current detection value Iqs, the q-axis voltage command value Vqo can still be attached to the limit value even when noise is generated, reducing abnormal noise and vibration of the rotating motor.

[0185] <Example>

[0186] The rotary motor 1 can be used as a driving force source for various devices other than the electric power steering system 100. For example, the rotary motor 1 can be used as a driving force source for the wheels.

[0187] The stator may also have multi-phase windings other than three-phase (e.g., two-phase, four-phase).

[0188] The stator may also be provided with multiple sets (e.g., two sets) of three-phase windings, and corresponding to each set of three-phase windings are various parts of the power converter and control device.

[0189] While this application describes various exemplary embodiments and examples, the various features, methods, and functions described in one or more embodiments are not limited to the application of a particular embodiment and can be applied to the embodiments individually or in various combinations. Therefore, it can be considered that numerous modifications 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.

[0190] Label Explanation

[0191] 1 Rotary electric motor

[0192] 4 Power Converter

[0193] 10. Control device for rotating electric machines

[0194] 31 Rotary Detection Unit

[0195] 32 Current Detection Unit

[0196] 33 Current coordinate transformation unit

[0197] 34 Current Command Value Calculation Unit

[0198] 35 Voltage Command Value Calculation Unit

[0199] 36 Switch Control Unit

[0200] Ido d-axis current command value

[0201] Ids d-axis current detection value

[0202] Iqo q-axis current command value

[0203] Iqs q-axis current sensing value

[0204] Vdo d-axis voltage command value

[0205] Vqo is the voltage command value for the q-axis.

[0206] ΔIdo: Change in d-axis current command value

[0207] ωido is the target response angular frequency.

Claims

1. A control device for a rotating electric motor, comprising controlling a rotating electric motor having a stator with multi-phase windings and a rotor with magnets via a power converter, the control device for the rotating electric motor being characterized in that it includes: A current detection unit that detects the current flowing through the multiphase winding; The current coordinate conversion unit converts the current detection value into the d-axis current detection value and the q-axis current detection value in a rotating coordinate system consisting of the d-axis determined in the direction of the magnetic pole position of the rotor and the q-axis determined in the direction that is 90 degrees ahead of the d-axis in electrical angle. A current command value calculation unit calculates the current command value for the d-axis and the current command value for the q-axis. A voltage command value calculation unit changes the voltage command value of the d-axis and the voltage command value of the q-axis so that the current detection value of the d-axis is close to the current command value of the d-axis and the current detection value of the q-axis is close to the current command value of the q-axis, and converts the voltage command value of the d-axis and the voltage command value of the q-axis into a multi-phase voltage command value based on the rotation angle. as well as A switching control unit, based on the voltage command value of the multiphase, causes multiple switching elements of the power converter to turn on and off. The current command value calculation unit changes the current command value of the d-axis based on the deviation between the current command value of the q-axis and the current detection value of the q-axis, i.e., the q-axis current deviation, multiplied by a proportional gain, and makes the proportional gain change inversely proportional to the rotational angular velocity of the rotor.

2. The control device for a rotating electric motor as described in claim 1, characterized in that, The current command value calculation unit changes the current command value of the d-axis based on the q-axis current deviation, and sets the value obtained by dividing the target response angular frequency of the feedback control system that reduces the absolute value of the q-axis current deviation by the rotational angular velocity as the proportional gain.

3. The control device for a rotating electric motor as described in claim 2, characterized in that, The current command value calculation unit sets the target response angular frequency to a value that is larger than the value obtained by dividing the resistance of the winding by the inductance.

4. The rotary motor control device as described in claim 2 or 3, characterized in that, The voltage command value calculation unit calculates the voltage command value of the d-axis based on the deviation between the current command value of the d-axis and the current detection value of the d-axis, i.e., the d-axis current deviation multiplied by the proportional gain of the d-axis, and sets the proportional gain of the d-axis to a value larger than the value obtained by multiplying the target response angular frequency by the inductance.

5. The control device for a rotating electric motor as described in any one of claims 1 to 4, characterized in that, The current command value calculation unit calculates the current command value of the d-axis based on the sum of the value obtained by multiplying the q-axis current deviation by the proportional gain and the integral value obtained by multiplying the q-axis current deviation by the integral gain, and makes the integral gain change inversely proportional to the rotational angular velocity.

6. The control device for a rotating electric motor as described in claim 5, characterized in that, The current command value calculation unit changes the current command value of the d-axis based on the q-axis current deviation, and sets the target response angular frequency of the feedback control system that reduces the absolute value of the q-axis current deviation to be divided by the rotational angular velocity, as the proportional gain. The value obtained by multiplying the target response angular frequency by the winding resistance is divided by the rotational angular velocity and inductance, and the resulting value is used as the integral gain.

7. The control device for a rotating electric machine as described in any one of claims 1 to 6, characterized in that, The current command value calculation unit calculates the q-axis current deviation by comparing the offset q-axis current command value (obtained by subtracting the q-axis offset value from the absolute value of the q-axis current command value) with the q-axis current detection value.

8. An electric power steering device, characterized in that, include: Control device for a rotating electric motor as described in any one of claims 1 to 7; The power converter; The rotary motor; as well as The driving force of the rotary motor is transmitted to the driving force transmission mechanism of the vehicle's steering device.

Images