JP6497231B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device.

  2. Description of the Related Art Conventionally, there is known a motor control device that converts a torque command value into a dq-axis current command value and controls an inverter to feedback control the amplitude and phase of a motor winding current. For example, the motor control device described in Patent Document 1 controls the current with the current phase that is the minimum current for obtaining the target torque. Thereby, the improvement of motor efficiency is aimed at.

JP 2012-200073 A

  However, in the conventional motor control device, electromagnetic excitation force (vibration force) caused by current control is generated in the stator, which may cause noise. The present invention focuses on the above-described problem, and an object thereof is to propose a motor control device that can suppress noise.

For this purpose, the motor control device of the present invention has a current phase that is closer to 0 ° than the current phase that is the minimum current for obtaining the target torque , and a predetermined allowable current increase amount with respect to the minimum current. The current is controlled with an increased magnitude, and the change in motor efficiency due to the increase in current by the allowable current increase with respect to the minimum current is within the range of variations in motor efficiency due to other factors. In addition, the allowable current increase amount is set .

Than the current phase as a minimum current for obtaining a target torque at the current phase is close to 0 °, and, with respect to the minimum current, controls the current in magnitude is increased by the predetermined allowable current increase, the The allowable current increase amount is set so that the margin of change in motor efficiency due to the increase in current by the allowable current increase amount is within the range of variation in motor efficiency due to other factors. Vibration force is reduced. Therefore, noise can be suppressed.

It is a block diagram showing roughly the composition of motor control device 1 of an embodiment. The operating condition judgment map when the battery voltage V of embodiment is low is shown. The operating condition judgment map when the battery voltage V of embodiment is high is shown. The current command value map of an embodiment is shown. 6 is a characteristic curve of current phase β and torque T according to the embodiment. 4 is a characteristic curve of current phase β and current Ia of the embodiment. The motor efficiency η when using the efficiency-oriented current map of the embodiment and when using the quietness-oriented current map is shown including variations. A characteristic curve of the current phase β and the current Ia of the embodiment is shown for each of a plurality of torques T. 5 is a characteristic curve showing the relationship between the current phase β and the electromagnetic excitation force F of the embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  First, the configuration will be described. FIG. 1 schematically shows a configuration of a motor control device 1 according to an embodiment. The motor control device 1 is applied to an electric vehicle. The electric vehicle includes a rotating electrical machine 2, a power source 3, a sensor 4, and a motor control device 1. A power source (hereinafter referred to as a battery) 3 is an in-vehicle DC power source. A rotating electrical machine (hereinafter referred to as a motor) 2 is used for an in-wheel motor (wheel drive unit) of an electric vehicle. The motor 2 is provided on each wheel, and enables the vehicle to travel by driving the wheels individually. The motor 2 functions as an electric motor to generate power when the battery 3 is discharged, and also functions as a generator so that the battery 3 can be charged. The motor 2 is accommodated in a member that rotatably supports the wheel. The motor 2 is a three-phase AC synchronous motor SM, which is a permanent magnet type PMSM using a permanent magnet PM, and is an internal type IPMSM in which a permanent magnet is embedded in a rotor.

  The motor 2 is an inner rotor type, and has an annular (hollow cylindrical shape) stator (stator), a rotor (movable element) coupled to an output shaft, and a motor case that houses the stator. The stator has a stator core and a coil wound around the stator core. The stator core is configured, for example, by arranging a plurality of core pieces (divided stator cores) in an annular shape. The core piece is formed, for example, by laminating a plurality of magnetic steel sheets made of magnetic material in the axial direction. The stator core has a plurality of (for example, 18) teeth on the inner peripheral side thereof. The teeth are salient poles extending in the radial direction and projecting to the rotor side. The plurality of teeth are arranged side by side in the circumferential direction, and are connected to each other by a back yoke portion on the base end side. A slot is formed between adjacent teeth. The coil is a motor winding wound around a tooth via an insulator (insulating member) so as to fit into the slot. The motor case is cylindrical, and the stator is housed inside and fixedly held by fitting the stator on the inner peripheral side thereof.

  The rotor has a cylindrical shape (disc shape), and is disposed on the inner peripheral side of the stator substantially coaxially with the stator. The rotor is disposed via a radial air gap (radial gap) with respect to the stator. A magnetic path is formed through this gap. The rotor includes, for example, a rotor core configured by laminating a plurality of magnetic steel plates made of a magnetic material around an output shaft in the axial direction, and a plurality of permanent magnets embedded in the rotor core. The plurality of permanent magnets are embedded in the rotor core so as to be arranged at equal intervals in the circumferential direction. One end side (side near the wheel) of the output shaft is rotatably supported by a bearing on the radially inner side of the motor case and is coupled to the wheel (wheel hub).

  A main magnetic circuit is formed by the permanent magnet embedded in the rotor, the magnetic body (electromagnetic steel plate) constituting the rotor core, and the magnetic body (electromagnetic steel plate) constituting the stator core. A magnetic flux generated from the permanent magnet and an alternating magnetic flux generated when a three-phase alternating current is applied to the stator (coil) by inverter control flows through the main magnetic circuit. Thereby, torque due to electromagnetic force is generated, and the rotor and the output shaft connected thereto are rotationally driven. The output of the motor 2 is transmitted to the wheel as a rotational force, and the electric vehicle can run by rotating the wheel integrally with the output shaft. During regenerative braking of the vehicle, the wheels are rotated by the inertial force of the vehicle body, and the motor 2 is driven via the output shaft by the rotational force from the wheels. At this time, the motor 2 operates as a generator, and the generated electric power is stored in the battery 3 via the inverter 100.

  The sensor 4 has a rotor position sensor 41 and a current sensor 42. The rotor position sensor 41 is an encoder, resolver, or the like provided in the motor 2 and detects the rotational position of the rotor. The current sensor 42 is a Hall element or the like provided corresponding to each phase of the motor 2 and detects the current of each phase energized to the stator, that is, the U-phase current iu, the V-phase current iv, and the W-phase current iw. To do.

  The motor control device 1 includes an inverter 100 and a control device 10. The inverter 100 is a PWM inverter, and the DC power from the battery 3 is converted into a three-phase AC by turning on or off the switching element in accordance with an inverter drive signal from the control device 10. Supply. The control device 10 controls the motor 2 by controlling the output of the inverter 100. The control device 10 converts the torque command value T * into the d-axis and q-axis current command values id * and iq *, and controls the inverter 100 based on the detection value of the sensor 4, thereby making the coil (motor winding) Feedback control is performed on the amplitude and phase of the supplied alternating current. Here, the dq-axis coordinate system is an orthogonal coordinate system composed of the d-axis and the q-axis, and rotates at an electrical rotation speed that is an integral multiple of the mechanical rotation speed of the motor 2. The motor 2 is a synchronous machine, and the dq axis coordinate system rotates in synchronization with the motor rotation. When the current supplied to the coil is divided into a field component current (d-axis current) and a torque component current (q-axis current) and is displayed as a vector, the angle β between the current vector and the q-axis corresponds to the above phase. The vector length Ia corresponds to the amplitude. β is a current phase angle with the q-axis side being 0 °.

  The control device 10 includes a current command value calculation unit 11, a current control unit 12, and an inverter drive signal generation unit 13. The current command value calculation unit 11 receives the rotation speed (rotation speed of the motor 2) N and the torque command value T *, and based on these, the d-axis current command value id * and the q-axis current command value iq * Is calculated. The rotational speed N of the rotor is obtained based on the detection value of the rotor position sensor 41, for example. The torque command value T * is a command value for obtaining the target torque of the motor 2, and is input from, for example, a vehicle control device that comprehensively controls the motion state of the vehicle. id * and iq * are obtained by referring to a current command value map prepared in advance. The determined id * and iq * are output to the current control unit 12.

  The current control unit 12 performs current feedback control in order to realize id * and iq * input from the current command value calculation unit 11. The current control unit 12 converts the three-phase alternating current iu, iv, iw detected by the current sensor 42 into a d-axis current id and a q-axis current iq based on the phase θ. The phase θ represents the position of the rotor 4 as an electrical phase, and is obtained based on the detection value of the rotor position sensor 41. The current control unit 12 uses the PI control so that the difference between the id * and iq * input from the current command value calculation unit 11 and the converted id and iq is 0, respectively, using the d axis and the q axis. Control voltages Vd and Vq are calculated. The current control unit 12 converts Vd, Vq into voltage command values Vu, Vv, Vw corresponding to each phase after referring to the phase θ. Vu, Vv, and Vw are output to the inverter drive signal generator 13.

  The inverter drive signal generation unit 13 generates an inverter drive signal for realizing Vu, Vv, and Vw input from the current control unit 12, and outputs the inverter drive signal to the inverter 100. By this inverter drive signal, the switching element of the inverter 100 is turned on / off, a voltage is applied to the motor terminal, and a current flows. As a result, torque is generated and the motor 2 is driven.

  The current command value calculation unit 11 includes a battery voltage detection unit 111 and a control switching unit 112. The battery voltage detection unit 111 detects the voltage (hereinafter referred to as battery voltage) V of the battery 3.

  The control switching unit 112 has a plurality of operation condition determination maps and two types of current command value maps. FIG. 2 shows an example of an operation condition determination map when the battery voltage V is low, and FIG. 3 shows an example of an operation condition determination map when V is high. The operating condition judgment map divides the possible output range of the motor 2 defined by the torque command value T * and the motor rotation speed N into two, the high torque side is considered as the efficiency-oriented region, and the low torque side is emphasized as the quietness It is an area. The boundary line that bisects both regions changes according to the level of the battery voltage V. As shown in FIG. 2, when V is relatively low, the boundary line is on the low torque side, the efficiency-oriented area is relatively wide, and the quiet-oriented area is relatively narrow. As shown in FIG. 3, when V is relatively high, the boundary line is on the high torque side, the efficiency-oriented area is relatively narrow, and the quiet-oriented area is relatively wide. The control switching unit 112 has a plurality of operation condition determination maps having different boundary lines according to V (for example, for each of a plurality of Vs). The control switching unit 112 receives an input of the current V, selects an operation condition determination map corresponding to the V, and receives an input of the current N and T *, and refers to the selected operation condition determination map. Then, it is determined whether the current operating point (N, T *) is in an efficiency-oriented area or quietness-oriented area.

  FIG. 4 shows an example of a current command value map. The current command value map is a table in which id * and iq * are defined in advance for each operating point based on the torque command value T * and the motor rotation speed N. The control switching unit 112 has an efficiency-oriented current map and a quietness-oriented current map as current command value maps. The id * and iq * specified at each operating point are different in both maps. The control switching unit 112 selects the efficiency-oriented current map when determining that the current operating point is in the efficiency-oriented region, and selects the silence-oriented current map when determining that the current operating point is in the quietness-oriented region. The current command value calculation unit 11 refers to the current command value map selected by the control switching unit 112 and determines id * and iq * based on the current N and T *.

  In the efficiency-oriented current map, id * and iq * are defined so that the current phase β = βi is realized. βi is a current phase such that the length of the current vector (hereinafter simply referred to as current) Ia becomes the minimum value (minimum current) Ia_i for obtaining the target torque. FIG. 5 shows a characteristic curve showing the relationship between the current phase β and the torque T when the current Ia is constant for each of a plurality of currents Ia. In the motor 2 which is a magnet-embedded synchronous machine, the q-axis reluctance is smaller than the d-axis reluctance, and has the same characteristics as a salient-pole synchronous machine in which an exciting winding is provided on the salient pole rotor of the reluctance motor. That is, the reluctance torque is generated by the saliency of the field pole of the rotor, and this reluctance torque contributes to the torque generation of the motor 2. The maximum torque can be obtained by operating at the current phase βi that maximizes the sum of the magnet torque and the reluctance torque. The smaller the current Ia, the smaller the maximum torque, and the characteristic curve becomes gentle near the maximum torque (the amount of change in T with respect to the amount of change in β is small). As the current Ia increases, the maximum torque increases, and the characteristic curve becomes steeper near the maximum torque (the amount of change in T with respect to the amount of change in β increases). As indicated by the dashed arrow, when the current phase is changed from βi when the torque T is constant at an arbitrary maximum torque, the current Ia increases. In other words, Ia is minimum when β is βi. Maximum efficiency control is performed by id * and iq * determined using an efficiency-oriented current map. The motor efficiency η is maximized by determining the ratio of id * and iq * so that the loss (current Ia) is minimized.

  In the silence-oriented current map, id * and iq * are defined so that the current phase β = βn is realized. βn is a current phase closer to 0 ° than βi. At βn, the current Ia becomes Ia_n that is larger by ΔIa than the minimum current Ia_i for obtaining the target torque. FIG. 6 is a characteristic curve showing the relationship between the current phase β and the current Ia when the torque T is constant. When β changes from βi to 0 ° and becomes βn, Ia increases from the minimum current Ia_i by ΔIa to Ia_n. As an idea of the current increase amount ΔIa that can be allowed when the quietness-oriented current map is created, for example, there are the following. That is, when the current command value map to be used is switched from the efficiency-oriented current map to the quietness-oriented current map, the reduction margin Δη of the motor efficiency η caused by ΔIa is the variation of the efficiency η among the individual motors (products). The allowable range of ΔIa is set so as to be smaller than the range (± σ). FIG. 7 shows η including variations in comparison between when the efficiency-oriented current map is used and when the quietness-oriented current map is used. ± σ (= 0.3%) is the tolerance range of η. When the efficiency-oriented current map is used, η is 95%, for example, and the variation range is 0.6% (= 0.3% × 2). When using the quietness-oriented current map, η is decreased by 0.1% to 94.9%, for example, and the variation range is 0.6%. The reduction margin Δη (0.1%) due to ΔIa is smaller than the variation range (0.6%).

  In the quietness-oriented current map, the amount of change Δβ from βi to βn in the predetermined operation region (shaded area in FIG. 4) on the low load (low torque, low rotation speed) side than in the other operation regions. Id * and iq * are specified so that becomes larger. This is because in this operating region, even if Δβ increases, the increase amount ΔIa of Ia from Ia_i falls within a predetermined allowable range. FIG. 8 shows the characteristic curve of FIG. The smaller the torque T, the smaller the minimum current Ia_i and the smoother the characteristic curve in the vicinity of Ia_i (the change amount ΔIa of the current Ia with respect to the change amount Δβ of β becomes smaller). As the torque T increases, the minimum current Ia_i increases and the characteristic curve becomes steeper in the vicinity of Ia_i (ΔIa with respect to Δβ increases). When ΔIa is the same, as indicated by an arrow, the amount of change Δβ from βi of the current phase β is larger when the torque T is small than when it is large.

  Next, the function and effect will be described. The motor 2 vibrates when a driving force is generated as an electric motor. The stator core is an oscillation source of the vibration of the motor 2. When the electromagnetic excitation force F of the stator core is transmitted to the motor case, noise to the outside of the motor case is generated. For example, the stator core vibrates radially (radially) with a relatively large amplitude at the outer periphery. Vibration and noise are generated by the electromagnetic excitation force F in the radial direction of the stator. The electromagnetic excitation force F in the radial direction is generated every time the magnetic pole of the field magnetic flux generated from the magnetic pole of the rotor crosses the opening of the slot provided in the stator when the rotor and the stator rotate relative to each other. This is caused by a change in the magnetic flux distribution in the gap. The rotational order, spatial order, and amplitude of the electromagnetic excitation force F depend on the number of magnetic poles of the motor 2 (the number of effective magnetic pole opening angles of the rotor and the number of slots provided in the stator). As the vibration mode by the electromagnetic excitation force F, there is an annular zero-order mode in which the stator vibrates in the same direction in the radial direction of the motor 2. When an electromagnetic excitation force F that depends on the number of magnetic poles of the motor 2 excites a resonance mode caused by the structure of the motor case, it becomes a high-tone noise that is annoying.

  The inventor investigated the relationship between the electromagnetic excitation force F and the current phase β by analysis and actual measurement, and as a result, found that F was reduced as β was brought closer to 0 °. FIG. 9 is a characteristic curve showing the relationship between β and F. At least in the range of βi or less, when β is small, F tends to be smaller than when it is large, specifically, F tends to be smaller as β approaches 0 ° than βi. When the efficiency-oriented current map is selected, the motor control device 1 sets id * and iq * so as to realize βi, and performs current feedback control. That is, maximum efficiency is achieved by controlling the current with βi. On the other hand, when a quietness-oriented current map is selected, id * and iq * are set so that βn closer to 0 ° than βi is realized, and current feedback control is performed. That is, the motor control device 1 realizes a reduction in the electromagnetic excitation force F by controlling the current with βn. Therefore, the vibration and noise of the motor 2 that the driver feels uncomfortable can be reduced, and a quiet and comfortable vehicle interior space can be provided.

  It is also conceivable to reduce the influence of the electromagnetic excitation force F by mechanical modification such as change of the part shape of the motor 2. For example, it is possible to suppress the generation of the electromagnetic excitation force F by providing a skew in the rotor. However, in this case, the average torque is reduced, and the motor efficiency may be deteriorated. Further, the transmission of the electromagnetic excitation force F can be suppressed by the mounting structure of the stator. For example, it is conceivable to provide a vibration isolating member between the motor case and the stator, or a floating structure that supports the stator in a state where the stator is floated with respect to the motor case. However, in this case, a vibration isolating member or the like is required, and an installation space for the vibration isolating member or the like is required. On the other hand, in-wheel motors have a limited space around the motor. That is, it is difficult to reduce the electromagnetic excitation force F while suppressing deterioration in efficiency and layout. The motor control device 1 can reduce the electromagnetic excitation force F while suppressing deterioration of efficiency and the like by changing the current control, not changing the shape.

  Note that the motor 2 may be used in a drive unit of a hybrid vehicle or the like, and the application is not particularly limited. Further, the AC supplied to the motor 2 is not limited to three phases. The control method of the inverter 100 for converting the direct current of the battery into the alternating current is not limited to PWM as long as it controls the amplitude and phase of the current, and may be PAM. The current control of the embodiment can be applied to other than the motor 2 of the in-wheel motor. By applying the current control to the motor 2 of the in-wheel motor, it is possible to remarkably obtain the effect of suppressing the deterioration of the layout and reducing the vibration and noise.

  In βi realized when the efficiency-oriented current map is selected, the current Ia for obtaining the target torque is the minimum current Ia_i. On the other hand, in βn realized when the quietness-oriented current map is selected, the current Ia for obtaining the target torque is increased by ΔIa from the minimum current Ia_i. The id * and iq * of the quietness-oriented current map are defined so that the increase amount ΔIa falls within a predetermined allowable range. That is, when using the quietness-oriented current map, the motor control device 1 controls the current with a magnitude that is increased by a predetermined allowable current increase amount ΔIa with respect to Ia_i. Thereby, loss due to an increase in Ia can be suppressed, and deterioration of motor efficiency η can be suppressed. That is, by reducing β to 0 ° with respect to βi to such an extent that the copper loss of the coil does not increase excessively, deterioration of efficiency can be suppressed while reducing vibration and noise. The motor to which the above current control is applied has a T-β characteristic that maximizes the torque T when β is greater than 0 ° as shown in FIG. 5 (reluctance torque contributes to generation of motor torque). If it is.

  The predetermined allowable range of ΔIa is set to a range in which a reduction margin Δη of the motor efficiency η caused by ΔIa falls within a variation range of η due to factors other than an increase in Ia (such as a manufacturing error). In other words, the allowable current increase amount ΔIa is set so that the variation amount Δη of η by increasing the current Ia by ΔIa with respect to the minimum current Ia_i is within the range of variation of η due to other factors. In the example shown in FIG. 8, Δη (0.1%) due to ΔIa is smaller than the variation range (0.6%) and smaller than the variation width σ (= 0.3%). Therefore, as shown by the range of the arrow α in FIG. 8, η when the quietness-oriented current map is used in a majority of the individual (product) groups of the motors 2 is η when the efficiency-oriented current map is used. It will be the same. That is, even when the quietness-oriented current map is used, η does not substantially change compared to when the efficiency-oriented current map is used. If Δη due to ΔIa is larger than the variation width σ (= 0.3%) but smaller than the variation range (0.6%), η when using the quietness-oriented current map is There is an individual (product) of the motor 2 that falls within the tolerance range of η when the map is used. Therefore, the efficiency deterioration margin due to ΔIa can be substantially suppressed.

  In the quietness-oriented current map, the amount of change Δβ from βi to βn is larger in the predetermined operation region (shaded area in FIG. 4) on the low load (low torque, low rotation speed) side than in the other operation regions. Id * and iq * are specified so that That is, the motor control device 1 controls the current with a current phase βn close to 0 ° with respect to the current phase βi that is the minimum current Ia_i when the torque T is small and larger. This is because, in the operation region where the torque T is relatively small, the increase amount ΔIa of Ia from Ia_i falls within a predetermined allowable range even when Δβ increases. Therefore, the electromagnetic excitation force can be effectively reduced by increasing Δβ as much as possible while suppressing the deterioration in efficiency due to ΔIa.

  The control switching unit 112 refers to the driving condition determination map, and determines whether the current driving point (N, T *) is in the efficiency-oriented area or quietness-oriented area. When it is determined that the current operating point is in the efficiency-oriented area, the efficiency-oriented current map is selected, and when it is determined that the current operating point is in the quiet-oriented area, the silence-oriented current map is selected. This switches between current control (with emphasis on efficiency) at the current phase βi that is the minimum current Ia_i and current control (with emphasis on silence) at a current phase βn close to 0 °. In this way, it is possible to switch between efficiency-oriented control and quietness-oriented control, so switching both controls according to operating conditions, etc., suppresses the deterioration of efficiency and reduces vibration and noise. Can be improved together.

  In the operating condition determination map, the boundary line between the efficiency-oriented area and the quiet-oriented area changes according to the level of the battery voltage V. Switching the determination of whether importance is placed on efficiency or quietness according to the battery voltage V in the same operating state (T, N) corresponds to switching the current control based on the state of charge (SOC) of the battery 3. That is, V correlates directly with SOC. Switching from quietness-oriented to efficiency-oriented when V decreases is equivalent to switching the current control of the motor 2 from quietness-oriented to efficiency-oriented when SOC decreases. As described above, the motor control device 1 performs the current control at the current phase βi that is the minimum current Ia_i from the current control at the current phase βn close to 0 ° (emphasis on quietness) when the capacity (SOC) of the battery 3 decreases. Switch to current control (with emphasis on efficiency). As a result, the current Ia is reduced, and further reduction in the capacity of the battery 3 is suppressed, so that the cruising distance of the vehicle can be ensured.

[Other embodiments]
As mentioned above, although the form for implementing this invention was demonstrated using drawing, the concrete structure of this invention is not limited to embodiment, The design change of the range which does not deviate from the summary of invention, etc. Is included in the present invention.

1 Motor control device 100 Inverter

Claims (4)

A motor control device that converts a torque command value into a dq-axis current command value and controls an inverter to feedback control the amplitude and phase of a motor winding current,
When the q-axis side is set to 0 °, the current phase is closer to 0 ° than the current phase that is the minimum current for obtaining the target torque , and the minimum current is increased by a predetermined allowable current increase amount. While controlling the current by the magnitude ,
The allowable current increase amount is set so that a change in motor efficiency due to the increase in current by the allowable current increase amount with respect to the minimum current is within a range of variations in motor efficiency due to other factors.
The motor control apparatus characterized by the above-mentioned . The motor control device according to claim 1,
Switching between current control at a current phase that is the minimum current and current control at a current phase close to 0 °;
The motor control apparatus characterized by the above-mentioned. The motor control device according to claim 2,
When the capacity of the battery is reduced, the current control at the current phase close to 0 ° is switched to the current control at the current phase that is the minimum current .
The motor control apparatus characterized by the above-mentioned. In the motor control device according to any one of claims 1 to 3,
When the target torque is small, the current is controlled with a current phase closer to 0 ° than when the target torque is large .
The motor control apparatus characterized by the above-mentioned.

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