Rotating electrical machine control device

Abstract

The present invention provides a rotating electrical machine control device. A current detection unit (30) has current detection elements (31-33) of each phase arranged on the high potential side of an upper arm element (21-23) or the low potential side of a lower arm element (24-26). The upper arm element (21-23) or the lower arm element (24-26) on the side where the current detection element (31-33) is arranged is used as a detection object element, and the duty cycle of the detection object element is set as a target duty cycle. A control unit (60) has a current acquisition unit (70), a power-on control unit (61), and an abnormality determination unit (65). The current acquisition unit (70) acquires a current detection value from the current detection unit (30). The abnormality determination unit (65) performs an abnormality determination based on the current detection value. The abnormality determination unit (65) makes a determination threshold used in the abnormality determination based on the current detection value variable according to the target duty cycle.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on Japanese Patent Application No. 2019-181510 filed on October 1, 2019, and the contents of the Japanese Patent Application are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a rotating electric machine control device. Background Art

[0004] For example, Patent Document 1 discloses that, in a three-phase brushless motor, a current detection circuit is considered abnormal when the absolute value of the sum of the currents flowing simultaneously through the three-phase coils exceeds a set value.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-237597 Summary of the Invention

[0006] For example, when current sensing elements are located on the low-potential side of an inverter, all phases of the lower arm elements must be conducting to simultaneously detect the three-phase current. However, if the lower arm elements are conducting for a short time, detection accuracy is reduced due to the effects of ringing and other factors, necessitating a higher threshold for abnormality detection. The present disclosure aims to provide a rotating electrical machine control device capable of appropriately detecting abnormalities.

[0007] The rotary electric machine control device disclosed herein is a device for controlling a rotary electric machine having multi-phase coils, and includes an inverter unit, a current detection unit, and a control unit. The inverter unit includes: an upper arm element corresponding to each phase of the coil and connected to the high potential side; and a lower arm element connected to the low potential side of the upper arm element and turned on and off complementarily with the corresponding upper arm element. The current detection unit includes current detection elements for each phase, which are arranged on the high potential side of the upper arm element or the low potential side of the lower arm element. Here, the upper arm element or the lower arm element on the side where the current detection element is arranged is used as the detection target element, and the duty cycle of the detection target element is used as the target duty cycle.

[0008] The control unit includes a current acquisition unit, an energization control unit, and an abnormality determination unit. The current acquisition unit acquires a current detection value from the current detection unit. The energization control unit controls the energization of the coil based on the current detection value. The abnormality determination unit performs an abnormality determination based on the current detection value. The abnormality determination unit adjusts the determination threshold used in the abnormality determination based on the current detection value according to the target duty cycle. This allows for appropriate abnormality detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above-mentioned objects and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings.

[0010] Figure 1 It is a schematic structural diagram of a steering system according to an embodiment.

[0011] Figure 2 This is a circuit diagram showing a driving device according to one embodiment.

[0012] Figure 3 This is a circuit diagram showing an amplifier circuit portion according to one embodiment.

[0013] Figure 4 This is a timing chart illustrating on-off control of the upper arm element and the lower arm element according to one embodiment.

[0014] Figure 5 This is a timing chart illustrating sample-and-hold according to one embodiment.

[0015] Figure 6 1 is a timing chart showing the voltage across both ends of a current detection element according to one embodiment.

[0016] Figure 7 This is an explanatory diagram for explaining an overcurrent determination threshold value according to one embodiment.

[0017] Figure 8 This is an explanatory diagram for explaining a short-circuit determination threshold value according to one embodiment.

[0018] Figure 9 This is a flowchart illustrating overcurrent determination processing according to one embodiment.

[0019] Figure 10 This is a flowchart illustrating the short-circuit determination process according to one embodiment. DETAILED DESCRIPTION

[0020] (One embodiment)

[0021] Hereinafter, the rotary electric machine control device of the present disclosure will be described based on the accompanying drawings. Figures 1 to 10 .like Figure 1 As shown, the drive device 10 includes an ECU 15 as a rotary electric machine control device and a motor 80 as a rotary electric machine, and is suitable for, for example, an electric power steering device 8 as a steering device for assisting vehicle steering operation.

[0022] Figure 1The structure of a steering system 90 equipped with an electric power steering device 8 is shown. The steering system 90 includes a steering wheel 91 as a steering member, a steering shaft 92, a pinion 96, a rack shaft 97, wheels 98, and the electric power steering device 8. The steering wheel 91 is connected to the steering shaft 92. A torque sensor 94 is provided on the steering shaft 92 to detect the steering torque Ts. A pinion 96 is provided at the front end of the steering shaft 92. The pinion 96 meshes with the rack shaft 97. A pair of wheels 98 are connected to both ends of the rack shaft 97 via tie rods and the like.

[0023] When the driver rotates the steering wheel 91, the steering shaft 92 connected to the steering wheel 91 rotates. The rotational motion of the steering shaft 92 is converted into linear motion of the rack shaft 97 by the pinion 96. The pair of wheels 98 are steered at an angle corresponding to the displacement of the rack shaft 97.

[0024] The electric power steering system 8 includes a motor 80, an ECU 15, and a reduction gear 89 serving as a power transmission unit that reduces the rotation of the motor 80 and transmits it to the steering shaft 92. Specifically, the electric power steering system 8 of this embodiment is a so-called "column-assisted" system, with the steering shaft 92 being the driven component. Alternatively, a so-called "rack-assisted" system may be employed, in which the rotation of the motor 80 is transmitted to the rack shaft 97.

[0025] like Figure 1 and Figure 2 As shown, the motor 80 outputs part or all of the torque required for steering operation and is driven by power supplied from the battery 105 as a power source, causing the reduction gear 89 to rotate forward and reverse. The motor 80 is a three-phase brushless motor and has a rotor and a stator (not shown). Figure 2 As shown, the position sensor 85 detects the electrical angle θe as the rotational position of the motor 80 and outputs the detected value to the control unit 60 .

[0026] The motor 80 includes a three-phase motor winding 81. The motor winding 81 includes a U-phase coil 811, a V-phase coil 812, and a W-phase coil 813, and is wound around the stator. The ECU 15 controls the driving of the motor 80 and includes an inverter unit 20, a current detection unit 30, an amplifier circuit unit 40, and a control unit 60.

[0027] The inverter unit 20 includes six switching elements 21 to 26, which convert the power supplied to the motor winding 81. Hereinafter, the switching elements are referred to as "SW elements." The SW elements 21 to 26 are MOSFETs, but may also be IGBTs, thyristors, or the like.

[0028] Switching elements 21-23 are connected to the high potential side, while switching elements 24-26 are connected to the low potential side. The connection point of the paired U-phase switching elements 21 and 24 is connected to one end of the U-phase coil 811. The connection point of the paired V-phase switching elements 22 and 25 is connected to one end of the V-phase coil 812. The connection point of the paired W-phase switching elements 23 and 26 is connected to one end of the W-phase coil 813. The other ends of coils 811-813 are connected.

[0029] The SW elements 21 to 23 located on the high-potential side are connected to the positive electrode of the battery 105 via the upper bus bar 27. The SW elements 24 to 26 located on the low-potential side are connected to the ground via the lower bus bar 28. Hereinafter, the SW elements 21 to 23 connected to the high-potential side will be referred to as "upper arm elements," and the SW elements 24 to 26 located on the low-potential side will be referred to as "lower arm elements."

[0030] The current detection unit 30 includes a U-phase current detection element 31, a V-phase current detection element 32, and a W-phase current detection element 33, and is disposed on the low-potential side of the inverter unit 20. Specifically, the U-phase current detection element 31 is disposed between the U-phase lower arm element 24 and the lower bus bar 28, the V-phase current detection element 32 is disposed between the V-phase lower arm element 25 and the lower bus bar 28, and the W-phase current detection element 33 is disposed between the W-phase lower arm element 26 and the lower bus bar 28. In other words, the current detection elements 31-33 are connected in series with the low-potential sides of the corresponding lower arm elements 24-26.

[0031] The current detection elements 31 to 33 of this embodiment are all shunt resistors. The voltages across the current detection elements 31 to 33 are output to the control unit 60 via the amplifier circuit unit 40 as detection values ​​of the phase currents Iu, Iv, and Iw, respectively.

[0032] Capacitor 51 and coil 52 are placed between battery 105 and inverter unit 20, forming a filter circuit. The presence of capacitor 51 and coil 52 reduces noise transmitted from other devices sharing battery 105, and also reduces noise transmitted from inverter unit 20 to other devices sharing battery 105.

[0033] Capacitor 51 is connected to upper busbar 27 and lower busbar 28 on the inverter unit 20 side of coil 52. Capacitor 51 stores charge to assist in the power supply to inverter unit 20 and to suppress noise components such as inrush current. A power relay (not shown) is provided between battery 105 and the filter circuit to cut off the power supply from battery 105 to inverter unit 20.

[0034] The control unit 60 is mainly composed of a microcomputer or the like, and internally includes a CPU, ROM, RAM, I / O, and a bus connecting these components (all not shown). Each process of the control unit 60 may be software processing implemented by the CPU executing a program pre-stored in a physical memory device such as ROM (i.e., a readable, non-transitory, tangible storage medium), or hardware processing performed by a dedicated electronic circuit.

[0035] The control unit 60 includes a power supply control unit 61, an abnormality determination unit 65, and an A / D converter unit 70. The power supply control unit 61 generates a drive signal for controlling the on / off operation of the SW elements 21 to 26 based on, for example, the phase currents Iu, Iv, and Iw, the electrical angle θe, and the steering torque Ts. The generated drive signal is output to the gates of the SW elements 21 to 26 via the drive circuit 55. The SW elements 21 to 26 are turned on and off according to the drive signal, thereby controlling the energization of the coils 811 to 813. The drive of the motor 80 is thus controlled by the control unit 60. The abnormality determination unit 65 performs an abnormality determination based on the detection value of the current detection unit 30.

[0036] The amplifier circuit section 40 is shown in FIG. Figure 3 .like Figure 3 As shown, the amplifier circuit section 40 includes a U-phase amplifier circuit section 41, a V-phase amplifier circuit section 42, and a W-phase amplifier circuit section 43, which are provided, for example, in an integrated circuit section (not shown). The U-phase amplifier circuit section 41 includes a differential amplifier circuit 410, a sample-and-hold circuit 416, and an operational amplifier 419, and outputs a U-phase current detection signal SGNu corresponding to the voltage across the current detection element 31. The differential amplifier circuit 410 includes resistors 411-414 and an operational amplifier 415. The sample-and-hold circuit 416 includes a switch 417 and a capacitor 418.

[0037] V-phase amplifier circuit section 42 includes a differential amplifier circuit 420, a sample-and-hold circuit 426, and an operational amplifier 429, and outputs a V-phase current detection signal SGNv corresponding to the voltage across current detection element 32. Differential amplifier circuit 420 includes resistors 421 to 424 and an operational amplifier 425. Sample-and-hold circuit 426 includes a switch 427 and a capacitor 428.

[0038] W-phase amplifier circuit section 43 includes a differential amplifier circuit 430, a sample-and-hold circuit 436, and an operational amplifier 439, and outputs a W-phase current detection signal SGNw corresponding to the voltage across current detection element 33. Differential amplifier circuit 430 includes resistors 431-434 and an operational amplifier 435. Sample-and-hold circuit 436 includes a switch 427 and a capacitor 428. Amplifier circuit sections 41, 42, and 43 are identical in detail, so the following description focuses on U-phase amplifier circuit section 41.

[0039] One end of resistor 411 is connected to the high potential side of the U-phase current detection element 31, and the other end is connected to the negative input terminal of the operational amplifier 415. Resistors 412 and 413 are connected in series, with the end of resistor 412 connected to the low potential side of the current detection element 31, and the end of resistor 413 connected to the reference potential Vr. The midpoint between resistors 412 and 413 is connected to the positive input terminal of the operational amplifier 415. Resistor 414 is provided in the feedback circuit that connects the output and negative input terminals of the operational amplifier 415.

[0040] In sample-and-hold circuit 416, the voltage across capacitor 418 is non-invertingly amplified by operational amplifier 419, and the resulting signal is output as U-phase current detection signal SGNu. Similarly, the voltage across capacitor 428 is non-invertingly amplified by operational amplifier 429, and the resulting signal is output as V-phase current detection value SGNv. Furthermore, the voltage across capacitor 438 is non-invertingly amplified by operational amplifier 439, and the resulting signal is output as W-phase current detection value SGNw. Current detection signals SGNu, SGNv, and SGNw are all analog signals, which are converted to digital signals by A / D converter 70.

[0041] In this embodiment, when no current is flowing, the U-phase current equivalent value is the reference potential Vr. Furthermore, when current flows toward ground through current detection element 31, the U-phase current equivalent value becomes less than the reference potential Vr. When current flows in the opposite direction, the U-phase current equivalent value becomes greater than the reference potential Vr. Therefore, the direction of current flow can be detected based on the magnitude relationship with the reference potential Vr. Furthermore, depending on the configuration of the amplifier circuit, the magnitude relationship with the detection center and the magnitude relationship with the current flow direction can also be set to be opposite.

[0042] In the following description, the current detection values ​​Iu_det, Iv_det, and Iw_det are obtained by converting the voltage across current detection elements 31-33 into current, assuming that the current is zero when no current flows through them, current flowing toward the ground line is positive, and current flowing away from the ground line is negative. Various voltage-based determinations can be performed during implementation, and determination thresholds and magnitude determinations can be appropriately set based on the definition of current direction.

[0043] like Figure 4 As shown, in this embodiment, the carrier signal Crr based on the triangular wave and the duty ratio command value DH of each phase are *The driving signal is generated by a triangular wave comparison method based on the comparison of the SW elements 21 to 26. The on-off control of the SW elements 21 to 26 can also use a control method other than the triangular wave comparison method. Here, the "duty cycle" in this specification is defined. In this embodiment, the duty cycle of the upper arm elements 21 to 23 is the upper duty cycle DH, and the duty cycle of the lower arm elements 24 to 26 is the lower duty cycle DL, and the subscript representing each phase is marked in the case of "DHu" as needed. In the following, when only "duty cycle" is mentioned, it refers to the upper duty cycle DH. Duty cycle command value DH * The same is true for switching elements 21 and 24. Therefore, if the upper duty cycle DH is 90%, the lower duty cycle DL is 100-90 = 10%. In practice, the on-time ratio is reduced due to the need to maintain dead time, but to avoid complexity, dead time is not considered in this specification.

[0044] Duty ratio command value DH during three-phase modulation * It is a sine wave signal, but Figure 4 In order to simplify the description, the duty cycle command value DH * Recorded as constant. Figure 4 In FIG. 1 , the U phase is represented by a solid line, the V phase is represented by a dotted line, and the W phase is represented by a dashed line. In this embodiment, when the duty ratio command value DHu * When the duty cycle command value DHu is greater than the carrier signal Crr, the upper arm element 21 is turned on and the lower arm element 24 is turned off. * When the voltage is less than the carrier signal Crr, the upper arm element 21 is turned off and the lower arm element 24 is turned on. The same applies to the V phase and the W phase.

[0045] Specifically, during period Pa, which includes the peak of carrier signal Crr, all lower arm elements 24-26 of the phases are turned on. Furthermore, during period Pb, which includes the valley of carrier signal Crr, all lower arm elements 24-26 of the phases are turned off. In this embodiment, since current detection elements 31-33 are located on the side of lower arm elements 24-26, during period Pa, current can be detected in all phases when current is flowing through current detection elements 31-33, while during period Pb, current can be detected in all phases when current is not flowing through current detection elements 31-33.

[0046] Hereinafter, the period during which all lower arm elements 24 to 26 are on when the upper duty ratio DH is at the duty ratio upper limit value Dx (described later) is referred to as the "full-on period," and the period during which all lower arm elements 24 to 26 are off when the upper duty ratio DH is at the duty ratio lower limit value Dy (described later) is referred to as the "full-off period." Depending on the duty ratio, some elements may be off during the full-on period, or some may be on during the full-off period. However, for convenience, these terms are referred to as the "full-on period" and the "full-off period," with details to be provided later.

[0047] In this embodiment, since it is necessary to detect the current of three phases simultaneously, sampling and holding circuits 416, 426, and 436 are provided, and sampling is performed using the same trigger signal output from the control unit 60. Figure 5 In FIG. 1 , from top to bottom, the on / off state of the upper arm element 21, the on / off state of the lower arm element 24, the trigger signal, the current detection signal SGNu, and the AD conversion timing are shown. The AD conversion timing is the on / off state of the switch of the equivalent circuit provided corresponding to each of the AD conversion units 70. Figure 5 As shown in FIG, when the trigger signal is “high”, the tracking mode is achieved by turning on the switch 417, and when the trigger signal is “low”, the hold mode is achieved by turning off the switch 417. Figure 5 In FIG, the solid line shows the current detection signal SGNu with sampling and holding, and the dot-dash line shows the current detection signal without sampling and holding. The sample-and-hold circuit 416 is designed so that the voltage drop during the holding period is within the allowable error range.

[0048] By switching the trigger signal to "Low" during the fully-on period, the values ​​detected simultaneously across the three phases can be retained. Furthermore, by sequentially switching the switches of the AD converter 70 for each phase, the retained detection values ​​can be converted into "simultaneously detected values" and then A / D-converted sequentially across the three phases. This also applies to current acquisition during the fully-off period.

[0049] like Figure 6 As shown, the voltage across current sensing element 31 overshoots and rings immediately after lower arm element 24 turns on, then converges to a value corresponding to the current. Accurate current detection cannot be performed during the transition time Xo, which lasts until the ringing converges. Therefore, current detection is performed during the settling time Xs after the transition time Xo. Therefore, for accurate current detection, the on-time or off-time of switching element 24 must be longer than the transition time Xo. Transition time Xo depends on circuit constants.

[0050] In this embodiment, when all the lower arm elements 24 to 26 are in the ON state, current detection is performed simultaneously on the three phases. Figure 7As shown, in order to ensure the on-time of the lower arm elements 24 to 26, the duty cycle range used for control is set to be below the duty cycle upper limit value Dx (for example, 90%). The range greater than the duty cycle upper limit value Dx and less than 100% is not used for control. However, in order to ensure output, a duty cycle of 100% is used for control. Figure 7 and Figure 8 In FIG. 1 , the range of current values ​​that can be obtained under normal conditions is shown by a pear-skin surface.

[0051] When the duty cycle is 100%, the duty cycle command value DH of the three phases is included. * The amplitude of the overmodulation process is larger than the carrier signal Crr, and the two-phase modulation process is performed by adding or subtracting the same value to the three phases so that the maximum value in the duty ratio becomes 100%, thereby shifting the neutral point voltage while maintaining the line voltage.

[0052] When the upper duty cycle DH is below the duty cycle upper limit Dx, Kirchhoff's law states that the sum of the phase currents Iu, Iv, and Iw (hereinafter referred to as the "three-phase sum") is zero. On the other hand, when the upper duty cycle DH is 100%, any of the lower arm elements 24-26 is turned off, making accurate current detection impossible for all three phases simultaneously. Even under normal circumstances, the three-phase sum will be zero.

[0053] Therefore, when using a judgment threshold to detect overcurrent abnormalities, it is necessary to set the threshold based on the worst-case condition of collapse where the sum of the three phases = 0 at a duty cycle of 100%. However, if the power supply circuit is made redundant, for example, to cope with autonomous driving, the wiring resistance of each system may increase due to the parallelization of the circuit. In addition, due to increased safety requirements, it is necessary to continue operating within a wider voltage range. The increase in wiring resistance leads to a decrease in the current generated during a fault. On the other hand, the expansion of the operating voltage range causes an increase in the current value that can be obtained during normal operation. Therefore, when the threshold for abnormality judgment cannot be appropriately set, there is a concern that appropriate fault detection cannot be performed.

[0054] Therefore, in this embodiment, the overcurrent determination threshold value Is_th is switched according to the on-time of the lower arm elements 24 to 26. Specifically, when the duty ratio command value DH * When the duty cycle upper limit value Dx is lower than the duty cycle upper limit value Dx, the first overcurrent determination threshold value Is_th1 is used. *When the overcurrent determination threshold value Is_th2 is 100%, the second overcurrent determination threshold value Is_th2 is used. The first overcurrent determination threshold value Is_th1 is set to a value that can be regarded as the sum of the three phases = 0, taking into account detection errors, etc. The second overcurrent determination threshold value Is_th2 is set to a value greater than the first overcurrent determination threshold value Is_th1, assuming that the sum of the three phases = 0 collapses. In other words, Is_th1 < Is_th2. In addition, since the duty cycle command value DH * When the duty ratio is greater than the upper limit value Dx, the on-time of the lower arm elements 24 to 26 is short, so that no through current flows and a large current is not generated. Therefore, the overcurrent determination threshold value Is_th may be set to a relatively large value.

[0055] Furthermore, in this embodiment, current detection is performed during both the fully-on period and the fully-off period for purposes such as offset correction. When lower arm elements 24-26 are off, the current is normally zero. However, if, for example, a short-circuit fault occurs in lower arm element 24, and a current flows from upper bus 27 to lower bus 28, the current during both the fully-on and fully-off periods becomes non-zero.

[0056] In this embodiment, arm short circuit abnormality detection is performed based on the current detection value of each phase. Figure 8 As shown, the duty cycle command value DH * In the range above the duty ratio lower limit value Dy, the phase currents Iu, Iv, and Iw are substantially zero during the full off period. On the other hand, when the duty ratio command value DH * When the duty ratio is less than the lower limit value Dy (for example, 10%), accurate current detection cannot be performed due to the influence of ringing or the like.

[0057] Therefore, in this embodiment, the arm short circuit determination threshold is switched according to the conduction time of the lower arm elements 24 to 26. For example, in the case of the U phase, when the duty ratio command value DH * When the duty cycle lower limit value Dy is greater than the duty cycle lower limit value Dy, the first short circuit determination threshold value Iu_th1 is used. When the duty cycle command value DH * When the duty ratio is less than the lower limit value Dy, the second short circuit determination threshold value Iu_th2 is used. The second short circuit determination threshold value Iu_th2 is set to a value greater than the first short circuit determination threshold value Iu_th1 in consideration of the influence of ringing, etc. That is, I#_th1<I#_th2.

[0058] exist Figure 8 The symbol "#" indicates u, v, and w of each phase. Here, the current obtained during the full conduction period is the duty cycle command value DH. *In the region greater than the duty ratio lower limit value Dy, it does not matter whether it is normal or greater than the first short circuit determination threshold value Iu_th1. * If the value greater than the duty ratio lower limit value Dy is used for offset correction, the duty ratio command value DH may be used. * The range smaller than the duty ratio lower limit value Dy is used for control.

[0059] In addition, when an overcurrent abnormality or an arm short circuit abnormality is detected, the duty cycle command value DH * The duty cycle is limited to a value greater than the lower duty cycle limit Dy and less than the upper duty cycle limit Dx. Overmodulation and neutral point voltage manipulation are suspended, and duty cycle restriction is implemented to return to three-phase modulation. Even if duty cycle restriction is implemented, if the abnormal state persists, it is determined to be abnormal.

[0060] Here, when an arm short-circuit abnormality occurs, current is usually generated from the power supply side to the ground side. On the other hand, due to the reverse input, the current caused by the back electromotive force generated by the external rotation of the motor 80 becomes reversed. For example, in the case of a collision with a curb or the like, when the steering wheel 91 is rotated at high speed during a control stop including the initial inspection, there is a large current equivalent to a fault generated by the back electromotive force. Therefore, in order to prevent erroneous judgment, when the direction of the current flowing through the current detection elements 31 to 33 is from the ground side to the power supply side, the overcurrent and arm short-circuit judgments are canceled, or another threshold value is set.

[0061] based on Figure 9 The flowchart of the overcurrent determination process of this embodiment is explained. This process is mainly performed by the abnormality determination unit 65 of the control unit 60 at a predetermined period, but part of the process can also be performed by other than the abnormality determination unit 65. In addition, the operation cycle of the overcurrent determination process can also be different from the current detection cycle. For example, when the operation cycle of the overcurrent determination process is longer than the current detection cycle, the latest current detection value can also be used, and the average value of multiple current detection values ​​can also be used. The same is true for the short-circuit determination process described later. In the following, the writing of "step" in step S101 is omitted and is only recorded as the symbol "S". The same applies to other steps.

[0062] In S101, the abnormality determination unit 65 determines whether the duty ratio command value DH * Is it below the duty cycle upper limit value Dx? * If the duty cycle upper limit value Dx is less than or equal to (S101: YES), the process proceeds to S102, where the overcurrent determination threshold value Is_th is set to the first overcurrent determination threshold value Is_th1. *If it is larger than the duty ratio upper limit value Dx ( S101 : No), the process proceeds to S103 , where the overcurrent determination threshold value Is_th is set to the second overcurrent determination threshold value Is_th2 .

[0063] In S104, the abnormality determination unit 65 determines whether the absolute value of the sum of the three-phase judgment value Is is greater than the overcurrent judgment threshold Is_th. The sum of the three-phase judgment value Is is as shown in formula (1). In addition, when the voltage value before current conversion is used as the current detection value Iu_det, Iv_det, Iw_det, the value of the detection center value equivalent to the current value 0 is corrected and used. When it is determined that the absolute value of the sum of the three-phase judgment value Is is less than the overcurrent judgment threshold Is_th (S104: "No"), a normal determination is made, S105 and subsequent processing are not performed, and this routine is terminated. When it is determined that the absolute value of the sum of the three-phase judgment value Is is greater than the overcurrent judgment threshold Is_th (S104: "Yes"), it is determined to be an overcurrent abnormality and moves to S105.

[0064] Is=Iu_det+Iv_det+Iw_det…(1)

[0065] In S105, the abnormality determination unit 65 determines whether the reverse flow condition is met. Here, when the current detection value Iu_det is less than the reverse flow determination threshold value Ir_th set to a negative value, it is determined to be in a reverse flow state. In this embodiment, since the current value in the reverse flow direction is set to a negative value, when the current detection value Iu_det is less than the reverse flow determination threshold value Ir_th, as an absolute value, the current detection value Iu_det is greater than the reverse flow determination threshold value Ir_th, and is regarded as "the reverse flow current is greater than the reverse flow determination threshold value". The same applies to the V phase and the W phase. In this step, when at least one of the current detection values ​​Iu_det, Iv_det, and Iw_det during the full conduction period and the full cutoff period of each phase is determined to be a reverse flow, an affirmative judgment is made. When it is determined that the reverse flow condition is met (S105: "Yes"), S106 and subsequent processing are not performed, and this routine is terminated. This processing corresponds to the cancellation processing of the overcurrent abnormality judgment. When it is determined that the reverse flow condition is not satisfied (S105: No), the process proceeds to S106 and the overcurrent counter C1 is incremented by 1.

[0066] In S107, the abnormality determination unit 65 determines whether the overcurrent counter C1 is greater than the duty cycle limit determination value E1. The duty cycle limit determination value E1 is set according to the time from the detection of the overcurrent abnormality to the start of the duty cycle limitation. If the duty cycle limit determination value E1 is set to 1, the duty cycle limitation is immediately implemented after the overcurrent abnormality is detected. The same applies to the duty cycle limit determination value E2 described later. When it is determined that the overcurrent counter C1 is less than the duty cycle limit determination value E1 (S107: "No"), S108 and subsequent processing are not performed, and this routine ends. When it is determined that the overcurrent counter C1 is greater than the duty cycle limit determination value E1 (S107: "Yes"), move to S108 and limit the duty cycle instruction value DH * If it is in the three-phase modulation period, the three-phase modulation will continue.

[0067] In S109, the abnormality determination unit 65 determines whether the overcurrent counter C1 is greater than the abnormality determination determination value F1. The abnormality determination determination value F1 is set according to the time from the detection of the overcurrent abnormality to the determination of the abnormality. The same applies to the abnormality determination determination value F2 described later. When it is determined that the overcurrent counter C1 is less than the abnormality determination determination value F1 (S109: "No"), the processing of S110 is not performed and this routine ends. When it is determined that the overcurrent counter C1 is greater than the abnormality determination determination value F1 (S109: "Yes"), it moves to S110, determines the overcurrent abnormality, and stops the drive control of the motor 80. In addition, when the combination of the motor winding 81 and the inverter unit 20 is used as a system, in the case of a plurality of systems, the system with the overcurrent abnormality can also be stopped, and the normal system can continue to drive the motor 80. The same applies to the short circuit abnormality.

[0068] based on Figure 10 The short circuit determination process is described in the flowchart of FIG. This process is performed for each phase and is described here by taking the U phase as an example. In S201, the abnormality determination unit 65 determines whether the duty cycle command value DH * Is it greater than the duty cycle lower limit value Dy? * If the duty ratio command value DH is greater than the duty ratio lower limit value Dy (S201: Yes), the process proceeds to S202, and the short circuit determination threshold value Iu_th is set to the first short circuit determination threshold value Iu_th1. * If it is smaller than the duty ratio lower limit value Dy ( S201 : No), the process proceeds to S203 , where the short-circuit determination threshold value Iu_th is set to the second short-circuit determination threshold value Iu_th2 .

[0069] In S204, the abnormality determination unit 65 determines whether the U-phase current detection value Iu_det during the full cutoff period and the full conduction period is greater than the short-circuit determination threshold value Iu_th. When the upper and lower parts are connected due to an arm short circuit, current flows during both the full cutoff period and the full conduction period. When it is determined that the U-phase current detection value Iu_det during the full cutoff period or the full conduction period is less than the short-circuit determination threshold value Iu_th (S204: "No"), S205 and subsequent processing are not performed, and this routine ends. When it is determined that the U-phase current detection value Iu_det during the full cutoff period and the full conduction period is greater than the short-circuit determination threshold value Iu_th (S204: "Yes"), it is determined that the U-phase arm short circuit is abnormal, and the process moves to S205, and the short-circuit abnormality counter C2 is incremented by 1. In addition, since the short-circuit determination threshold value Iu_th is set to a positive value, when an affirmative judgment is made in S204, there is no reverse flow of current in the U phase.

[0070] In S206, the abnormality determination unit 65 determines whether the short-circuit abnormality counter C2 is greater than the duty cycle limit determination value E2. If it is determined that the short-circuit abnormality counter C2 is less than the duty cycle limit determination value E2 (S206: "No"), the processing of S206 and subsequent steps is not performed, and this routine ends. If it is determined that the short-circuit abnormality counter C2 is greater than the duty cycle limit determination value E2 (S206: "Yes"), the routine moves to S207 and limits the duty cycle command value DH. * If it is in the three-phase modulation period, the three-phase modulation will continue.

[0071] In S208, the abnormality determination unit 65 determines whether the short-circuit abnormality counter C2 is greater than the abnormality determination value F2. If the short-circuit abnormality counter C2 is determined to be less than the abnormality determination value F2 (S208: No), the process of S209 is skipped and the routine ends. If the short-circuit abnormality counter C2 is determined to be greater than the abnormality determination value F2 (S208: Yes), the process proceeds to S209, where a U-phase arm short-circuit abnormality is determined and the drive control of the motor 80 is stopped.

[0072] In this embodiment, the overcurrent determination threshold value Is_th and the short-circuit determination threshold value I#_th are variable based on the on-time of the lower arm elements 24-26. When the on-time of the lower arm elements 24-26 is long, current detection accuracy is higher in the fully on state. Therefore, by setting the overcurrent determination threshold value Is_th to a relatively small value, overcurrent detection can be performed with high accuracy. Furthermore, even when the on-time is short, setting the overcurrent determination threshold value Is_th to a relatively large value can prevent erroneous detections.

[0073] When the off-time of lower arm elements 24-26 is long, current detection accuracy is higher in the fully off state. Therefore, by setting the short-circuit determination threshold I#_th to a relatively small value, short-circuit detection can be performed with high accuracy. Furthermore, even when the off-time is short, setting the short-circuit determination threshold I#_th to a relatively large value prevents false detections. Furthermore, when an abnormality is detected, by limiting the upper and lower limits of the duty cycle and continuing detection through three-phase modulation, it is possible to appropriately distinguish between a temporary abnormality and a true abnormality.

[0074] As described above, ECU 15 controls the driving of motor 80 having multi-phase coils 811 to 813 and includes an inverter unit 20, a current detection unit 30, and a control unit 60. Inverter unit 20 includes upper arm elements 21 to 23 and lower arm elements 24 to 26. Upper arm elements 21 to 23 correspond to respective phases of coils 811 to 813 and are connected to the high-potential side. Lower arm elements 24 to 26 are connected to the low-potential sides of upper arm elements 21 to 23 and are turned on and off in a complementary manner to the corresponding upper arm elements 21 to 23.

[0075] The current detection unit 30 includes current detection elements 31-33 for each phase, located on the high-potential side of the upper arm elements 21-23 or the low-potential side of the lower arm elements 24-26. Here, the upper arm elements 21-23 or lower arm elements 24-26 on which the current detection elements 31-33 are located are the detection target elements. In this embodiment, since the current detection elements 31-33 are located on the low-potential side of the lower arm elements 24-26, the lower arm elements 24-26 are the detection target elements. Furthermore, the duty ratios of the lower arm elements 24-26 are the target duty ratios.

[0076] The control unit 60 includes an A / D converter 70, an energization control unit 61, and an abnormality determination unit 65. The A / D converter 70 obtains the current detection values ​​Iu_det, Iv_det, and Iw_det from the current detection unit 30. In this embodiment, the A / D converter 70 obtains the detection values ​​via the amplifier circuit unit 40. The energization control unit 61 controls the energization of the coils 811 to 813 based on the current detection values ​​Iu_det, Iv_det, and Iw_det. The abnormality determination unit 65 performs abnormality determination based on the current detection values ​​Iu_det, Iv_det, and Iw_det.

[0077] The abnormality determination unit 65 varies the determination threshold used for abnormality determination based on the current detection values ​​Iu_det, Iv_det, and Iw_det according to the target duty cycle, thereby enabling appropriate abnormality determination.

[0078] When abnormality determination unit 65 performs abnormality determination based on the sum of all phases at the full conduction timing at which all lower arm elements 24-26 of all phases can conduct, the determination threshold value when the target duty cycle is greater than the full conduction threshold switching duty cycle is a value corresponding to a current smaller than that when the target duty cycle is less than the full conduction threshold switching duty cycle. In this embodiment, this means Is_th1 < Is_th2. This allows for appropriate detection of overcurrent abnormalities.

[0079] When an abnormality is detected through abnormality determination based on the sum of all phase currents, energization control unit 61 sets the target duty cycle to a value greater than the threshold switching duty cycle and limits energization of coils 811-813 through three-phase modulation. Consequently, when a temporary abnormality is detected, the target duty cycle is set to a value greater than the full-conduction threshold switching duty cycle while maintaining the threshold corresponding to low current (i.e., the first overcurrent determination threshold Is_th1), enabling appropriate continued detection of abnormal conditions. Furthermore, the use of three-phase modulation reduces the effects of voltage distortion, compared to, for example, two-phase modulation.

[0080] When abnormality determination unit 65 performs abnormality determination based on the current detection values ​​Iu_det, Iv_det, and Iw_det for each phase at the full cutoff timing at which all phases' detection target elements can be cut off, the determination threshold value when the target duty ratio is less than the full cutoff threshold switching duty ratio is a value corresponding to a current smaller than that when the target duty ratio is greater than the full cutoff threshold switching duty ratio. In this embodiment, this means that I#_th1 < I#_th2. This allows for appropriate detection of short-circuit abnormalities.

[0081] When an abnormality is detected based on the abnormality determination of the current detection values ​​Iu_det, Iv_det, and Iw_det of each phase at the full cutoff occurrence timing, energization control unit 61 sets the target duty cycle to be below the full cutoff threshold switching duty cycle and limits energization of coils 811-813 through three-phase modulation. Thus, when a temporary abnormality is detected, by setting the target duty cycle to be below the full cutoff threshold switching duty cycle and maintaining the determination value corresponding to low current (i.e., the first short-circuit determination threshold I#_th1), abnormality detection can be appropriately continued. Furthermore, by using three-phase modulation, the effects of voltage distortion and other factors can be reduced compared to, for example, two-phase modulation.

[0082] If reverse current is detected from the ground side of current detection elements 31-33 to the power supply side (S105: YES), abnormality determination unit 65 cancels the abnormality determination. This prevents erroneous determinations caused by current generated by the back electromotive force generated by the external rotation of motor 80 due to reverse input.

[0083] The current detection elements 31-33 in this embodiment are shunt resistors. ECU 15 further includes an amplifier circuit unit 40. Amplifier circuit unit 40 includes differential amplifier circuits 410, 420, and 430, and sample-and-hold circuits 416, 426, and 436, which amplify the voltage across the current detection elements 31-33. Sample-and-hold circuits 416, 426, and 436 sample and hold the outputs of differential amplifier circuits 410, 420, and 430 every half cycle of the on-off cycle of the lower arm elements 24-26. In this embodiment, by sampling current detection signals SGNu, SGNv, and SGNw every half cycle of the on-off cycle, that is, by detecting current during the full on period near the peak of the carrier signal Crr and the full off period near the trough of the carrier signal Crr, detection is performed when all phases of the lower arm elements 24-26 are on and when all phases are off. This makes it possible to appropriately perform abnormality determination based on the current detection values ​​Iu_det, Iv_det, and Iw_det.

[0084] In this embodiment, the ECU 15 corresponds to the "rotating electric machine control device," and the A / D converter 70 corresponds to the "current acquisition unit." The current detection unit 30 is located on the low-potential side, and the lower arm elements 24 to 26 correspond to the "detection target elements." Therefore, the lower duty cycle DL corresponds to the "target duty cycle." Furthermore, the overcurrent determination threshold and the short-circuit determination threshold correspond to the "determination threshold." The period of the carrier signal Crr corresponds to the "on-off period of the detection target element."

[0085] The "full-on period" corresponds to the "full-on occurrence timing". In addition, if the duty ratio is 100% or two-phase modulation is used, not all phases of the lower arm elements 24 to 26 need to be turned on. In addition, the duty ratio upper limit value Dx corresponds to the "full-on threshold switching duty ratio", and the duty ratio command value DH * If the duty ratio upper limit value Dx is less than or equal to (S101: YES), it corresponds to "the target duty ratio is greater than or equal to the full-on threshold switching duty ratio", and the duty ratio command value DH * The case where the target duty ratio is greater than the duty ratio upper limit value Dx ( S101 : No) corresponds to the case where the target duty ratio is smaller than the full-on threshold switching duty ratio.

[0086] The "full cut-off period" corresponds to the "full cut-off occurrence timing". In addition, it is also possible to use two-phase modulation, so that not all phases of the lower arm elements 24 to 26 are cut off. In addition, the duty cycle lower limit value Dy corresponds to the "full cut-off threshold switching duty cycle", and the duty cycle command value DH * If the duty ratio lower limit value Dy is greater than or equal to (S201: Yes), it corresponds to "the target duty ratio is less than or equal to the full cutoff threshold switching duty ratio", and the duty ratio command value DH *If the duty cycle is less than the duty cycle lower limit Dy (S201: No), this corresponds to "the target duty cycle is greater than the full-off threshold switching duty cycle." Alternatively, multiple threshold switching duty cycles may be provided to gradually switch the determination threshold. While S204 uses the values ​​of the full-on period and the full-off period for determination, the use of the full-on period value for determination may be omitted.

[0087] The so-called "value corresponding to a small current" means that the first overcurrent determination threshold value Is_th1 is less than the second overcurrent determination threshold value Is_th2, i.e., Is_th1 < Is_th2, and the first short-circuit determination threshold value I#_th1 is less than the second overcurrent determination threshold value Is_th2, i.e., I#_th1 < I#_th2. Furthermore, for example, when performing threshold comparison based on the voltage value before current conversion, if the voltage value decreases with increasing current, the value will be larger when the target duty cycle is greater than the threshold switching duty cycle compared to when the target duty cycle is less than the threshold switching duty cycle. In such cases, the value used for determination is appropriately set based on the relationship between the current value and the value used for determination.

[0088] (Other embodiments)

[0089] In the above embodiment, the current detection element is provided on the low potential side of the lower arm element. In other embodiments, the current detection element may also be provided on the high potential side of the upper arm element. In this case, the upper arm element corresponds to the "detection object element" and the upper side duty cycle corresponds to the "object duty cycle". When the current detection element is on the high potential side, the "full cutoff occurrence timing" is on the trough side of the carrier and the "full conduction occurrence timing" is on the peak side of the carrier. In addition, in the above embodiment, the current detection element is a shunt resistor. In other embodiments, the current detection element may also use an element other than a shunt resistor such as a Hall IC.

[0090] In the above embodiment, whether the reverse flow condition is met is determined based on the current detection value. In other embodiments, the reverse flow determination can also be performed based on the motor speed. That is, when the motor speed is greater than the reverse flow determination value, the abnormality determination can also be blocked.

[0091] In the above embodiment, one motor winding, one inverter unit, and one control unit are each provided. In other embodiments, two or more motor windings, inverter units, and control units may be provided. Furthermore, the number of motor windings, inverter units, and control units may vary, for example, providing one control unit for multiple motor windings and inverter units, or providing multiple inverter units and motor windings for one control unit.

[0092] In the above embodiment, the amplifier circuit unit is provided in the integrated circuit unit. In other embodiments, for example, the differential amplifier circuit may be provided in the integrated circuit unit, while the sample-and-hold circuit may be provided within a microcomputer constituting the control unit. Furthermore, the sample-and-hold circuit may be provided separately from the integrated circuit unit and the control unit.

[0093] In the above embodiment, the rotating electric machine is a three-phase brushless motor. In other embodiments, the rotating electric machine is not limited to a brushless motor and may have four or more phases. Furthermore, it may be a so-called electric generator that also functions as a generator. In the above embodiment, the control device is applied to an electric power steering system. In other embodiments, the control device may be applied to steering systems other than electric power steering systems that control steering, such as steer-by-wire systems. Furthermore, the control device may be applied to in-vehicle devices other than steering systems or to non-in-vehicle devices.

[0094] The control unit and method thereof described in the present disclosure may also be implemented by a special-purpose computer, which is provided by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and method thereof described in the present disclosure may also be implemented by a special-purpose computer provided by a processor composed of one or more special-purpose hardware logic circuits. Alternatively, the control unit and method thereof described in the present disclosure may also be implemented by one or more special-purpose computers composed of a combination of a processor and a memory programmed to execute one or more functions and a processor composed of one or more hardware logic circuits. In addition, the computer program may also be stored as an instruction executed by a computer in a non-transitional tangible recording medium that is readable by a computer. As described above, the present disclosure is not limited in any way by the above-mentioned embodiments and can be implemented in various ways without departing from its main purpose.

[0095] The present disclosure is described based on the embodiments. However, the present disclosure is not limited to the embodiments and configurations. The present disclosure also includes various modifications and variations within the scope of the equivalents. In addition, various combinations and methods, and other combinations and methods that include only one element, more than one, or less than one element, also fall within the scope and spirit of the present disclosure.

Claims

1. A rotating electrical machine control device for controlling the driving of a rotating electrical machine having a multi-phase coil, The above-mentioned rotating electrical machine control device comprises: The inverter unit includes an upper arm element and a lower arm element, wherein: The upper arm element corresponds to each phase of the coil and is connected to a high potential side, and the lower arm element is connected to a low potential side of the upper arm element and is turned on and off complementarily to the corresponding upper arm element; a current detection unit having a current detection element, wherein the current detection element is provided at each phase on the high potential side of the upper arm element or each phase on the low potential side of the lower arm element; as well as The control unit includes a current acquisition unit, a power-on control unit, and an abnormality determination unit, wherein the current acquisition unit acquires a current detection value from the current detection unit, the power-on control unit controls the power-on of the coil based on the current detection value, and the abnormality determination unit performs abnormality determination based on the current detection value. If the upper arm element or the lower arm element on the side where the current detection element is provided is used as the detection object element, and the duty ratio of the detection object element is used as the target duty ratio, then The abnormality determination unit makes variable a determination threshold value used for abnormality determination based on the current detection value, according to the target duty ratio.

2. The rotating electrical machine control device according to claim 1, wherein: When the abnormality judgment unit makes an abnormality judgment based on the current sum of all phases at the full conduction timing when the detection object elements of all phases can be turned on, the judgment threshold when the object duty cycle is above the full conduction threshold switching duty cycle corresponds to a current value smaller than the object duty cycle when it is less than the full conduction threshold switching duty cycle.

3. The rotating electrical machine control device according to claim 2, wherein: When an abnormality is detected by the abnormality determination based on the current sum of all phases, the energization control unit sets the target duty ratio to be equal to or greater than the full-on threshold switching duty ratio and limits energization of the coil by three-phase modulation.

4. The rotating electrical machine control device according to any one of claims 1 to 3, wherein: When the abnormality judgment unit performs abnormality judgment based on the current detection value of each phase at the full cut-off occurrence timing when the detection object elements of all phases can be cut off, the judgment threshold when the object duty cycle is below the full cut-off threshold switching duty cycle corresponds to a current value smaller than the current when the object duty cycle is greater than the full cut-off threshold switching duty cycle.

5. The rotating electrical machine control device according to claim 4, wherein: When an abnormality is detected by abnormality determination based on the current detection values ​​of each phase at the full cutoff occurrence timing, the energization control unit sets the target duty ratio to be less than the full cutoff threshold switching duty ratio and limits energization of the coil by three-phase modulation.

6. The rotating electrical machine control device according to any one of claims 1 to 3, wherein: The abnormality determination unit cancels abnormality determination based on the current detection value when a reverse current flowing from the ground side to the power supply side of the current detection element is larger than a reverse current determination threshold value.

7. The rotating electrical machine control device according to any one of claims 1 to 3, wherein: The above current sensing element is a shunt resistor, The rotating electrical machine control device comprises an amplifier circuit unit having a differential amplifier circuit and a sample-and-hold circuit. The differential amplifier circuit amplifies the voltage across the current detection element. The sample-and-hold circuit samples and holds the output of the differential amplifier circuit every 1 / 2 of the on-off period of the detection object element.

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