JP2012147531A - Electric power steering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering apparatus that can identify an anomalous phase even when detecting two phase currents out of three phase currents.SOLUTION: An electric power steering apparatus 10 detects, as an anomalous phase, a phase other than combinations of phases having an interphase voltage of near zero volts in the condition that a torque axis current is at a first threshold or less while a torque axis voltage is applied.

Description

  The present invention relates to an electric power steering apparatus that applies a force (steering assist force) for assisting a driver's steering from a motor when operating a steering handle.

  There is known an electric power steering device that applies a force (steering assist force) for assisting a driver's steering from a motor so that the steering wheel can be easily operated (Patent Document 1, Patent Document). 2 and Patent Document 3).

  In Patent Literature 1, current is detected for each of the three phases of the motor ([0021]), and whether or not current is flowing is determined to determine whether or not an abnormal phase has occurred (abnormal phase). ([0022]). When an abnormal phase occurs, the switching element of the inverter is controlled for a normal phase other than the abnormal phase (see summary and claims 1 and 3).

  Further, in Patent Document 2, two-phase currents (U-phase current and W-phase current) out of three phases are detected, and the remaining one-phase current is calculated from these two-phase currents and used for subsequent inverter control. (FIG. 2, [0023]). Similarly, in Patent Document 3, two-phase currents (U-phase current and V-phase current) among the three phases are detected, and the remaining one-phase current is calculated from these two-phase currents for subsequent inverter control. Used (FIG. 2, [0012], [0018]).

International Publication No. 2005/091488 JP 2009-090817 A JP 2006-256542 A

  As described above, in Patent Document 1, an abnormal phase is specified by detecting current for each of the three phases. However, in the configuration in which currents of two phases out of the three phases are detected as in Patent Document 2 and Patent Document 3, it is difficult to specify an abnormal phase when an abnormality such as disconnection occurs in any one of the phases. .

  The present invention has been made in consideration of such a problem, and provides an electric power steering apparatus capable of specifying an abnormal phase even when a current of two phases out of three phases is detected. The purpose is to do.

  An electric power steering apparatus according to the present invention includes an inverter that supplies three-phase AC power to a motor, a d-axis current that is an excitation current component, and a q-axis current that is a torque current component. Current coordinate conversion means for converting to dq coordinate current, voltage coordinate conversion means for converting a three-phase voltage applied to the motor into d-axis voltage and q-axis voltage, and the q-axis voltage are applied. Nevertheless, an abnormal phase detection means for detecting a phase other than the combination phase in which the interphase voltage is in the vicinity of zero volts as the abnormal phase when the q-axis current is equal to or less than the first threshold value.

  According to the present invention, a phase other than the combination phase in which the interphase voltage is close to zero volts in the state where the q-axis current is equal to or lower than the first threshold despite the q-axis voltage being applied is defined as an abnormal phase. To detect. For this reason, if a value that cannot be obtained according to the q-axis voltage (for example, zero or a value in the vicinity thereof) is set as the first threshold value of the q-axis current, current sensors are provided for only two phases, and the remaining one phase Even if the configuration is not provided, the abnormal phase can be detected.

  The electric power steering device may further include a rotation speed detection unit that detects a rotation speed of the motor, and may operate the abnormal phase detection unit when the rotation speed is equal to or less than a second threshold value. Thereby, for example, if the rotation speed (including the vicinity value) that adversely affects the specific accuracy of the abnormal phase due to the back electromotive force by the motor is set as the second threshold, the abnormality is detected only when the specific accuracy is ensured. By specifying the phase, it is possible to prevent erroneous detection.

  When driving all three phases, if the abnormal phase detection means detects an abnormal phase, the motor output is reduced in the vicinity of an electrical angle at which the motor output decreases due to the abnormal phase not functioning. A phase other than the abnormal phase may be driven so as to increase. As a result, even when an abnormal phase exists, it is possible to suppress a sudden decrease in the output of the motor and to stably generate the steering assist force from the motor.

  According to the present invention, a phase other than the combination phase in which the interphase voltage is close to zero volts in the state where the q-axis current is equal to or lower than the first threshold despite the q-axis voltage being applied is defined as an abnormal phase. To detect. For this reason, if a value that cannot be obtained according to the q-axis voltage (for example, zero or a value in the vicinity thereof) is set as the first threshold value of the q-axis current, current sensors are provided for only two phases, and the remaining one phase Even if the configuration is not provided, the abnormal phase can be detected.

1 is a schematic configuration diagram of an electric power steering apparatus according to an embodiment of the present invention. It is a circuit block diagram about a part of the electric power steering apparatus. It is a figure which shows the internal structure and function of the input and output to an electronic controller (ECU), ECU. It is a flowchart which shows the whole process of ECU in this embodiment. It is a functional block diagram of ECU in normal time electricity supply control. It is a figure which shows an example of the waveform of the torque of each phase in normal time electricity supply control, steering assist torque, and the electric current of each phase. It is a flowchart of the abnormality determination process by ECU. It is a flowchart of the abnormal phase specific process by ECU. It is a functional block diagram of ECU in the electricity supply control at the time of abnormality occurrence. It is a functional block diagram of a gain setting part. It is a figure which shows an example of the relationship between the electrical angle of the motor in the electricity supply control at the time of abnormality generation | occurrence | production at the time of abnormality occurring in a U phase, and the output voltage of each phase. It is a figure which shows an example of the relationship between the electrical angle of the motor in the electricity supply control at the time of abnormality generation | occurrence | production when abnormality occurs in V phase, and the output voltage of each phase. It is a figure which shows an example of the relationship between the electrical angle of the motor in the electricity supply control at the time of abnormality generation | occurrence | production when abnormality occurs in the W phase, and the output voltage of each phase. It is a figure which shows the 1st modification of the relationship between the electrical angle of a motor in the electricity supply control at the time of abnormality generation, and the output voltage of each phase. It is a figure which shows the 2nd modification of the relationship between the electrical angle of the motor in the electricity supply control at the time of abnormality occurrence, and the output voltage of each phase. It is a figure which shows the 3rd modification of the relationship between the electrical angle of the motor in the electricity supply control at the time of abnormality generation, and the output voltage of each phase. It is a figure which shows the 4th modification of the relationship between the electrical angle of the motor in the electricity supply control at the time of abnormality occurrence, and the output voltage of each phase. It is a figure which shows the 5th modification of the relationship between the electrical angle of a motor in the electricity supply control at the time of abnormality generation | occurrence | production, and the output voltage of each phase. It is a figure which shows the 6th modification of the relationship between the electrical angle of the motor in the electricity supply control at the time of abnormality generation | occurrence | production, and the output voltage of each phase.

I. Embodiment A. 1. Description of configuration FIG. 1 is a schematic configuration diagram of an electric power steering device 10 (hereinafter also referred to as “power steering device 10”) according to an embodiment of the present invention. FIG. 2 is a circuit configuration diagram of a part of the power steering apparatus 10.

  As shown in FIG. 1, the power steering apparatus 10 has a steering handle 12 (steering wheel), a steering shaft 14, a rack shaft 16, a tie rod 18, and left and right front wheels 20 as steered wheels. The steering shaft 14, the rack shaft 16, and the tie rod 18 constitute a manual steering system that directly transmits the steering operation of the driver with respect to the steering handle 12 to the front wheels 20.

  As shown in FIGS. 1 and 2, the power steering apparatus 10 includes a motor 22, a worm gear 24, a worm wheel gear 26, a torque sensor 28, a vehicle speed sensor 30, a steering angle sensor 32, and a battery 34. And an inverter 36, current sensors 38 and 40, a resolver 42, voltage sensors 44, 46 and 48, and an electronic control unit 50 (hereinafter referred to as “ECU 50”). The motor 22, the worm gear 24, and the worm wheel gear 26 constitute an assist drive system that generates a force (steering assist force) that assists the driver's steering. The torque sensor 28, the vehicle speed sensor 30, the steering angle sensor 32, the inverter 36, the current sensors 38 and 40, the resolver 42, the voltage sensors 44, 46, and 48 and the ECU 50 constitute an assist control system that controls the assist drive system. . Hereinafter, the assist drive system, the assist control system, and the battery 34 are collectively referred to as a steering assist system.

2. Manual steering system The steering shaft 14 connects a main steering shaft 52 integrally coupled to the steering handle 12, a pinion shaft 54 provided with a pinion 56 of a rack and pinion mechanism, and the main steering shaft 52 and the pinion shaft 54. Universal joint 58.

  The pinion shaft 54 is supported at its upper, middle, and lower portions by bearings 60 a, 60 b, 60 c, and the pinion 56 is provided at the lower end of the pinion shaft 54. The pinion 56 meshes with the rack teeth 62 of the rack shaft 16 that can reciprocate in the vehicle width direction.

  Therefore, the steering torque Tr (rotational force) generated by the driver operating the steering handle 12 is transmitted to the pinion shaft 54 via the main steering shaft 52 and the universal joint 58. The steering torque Tr is converted into thrust by the pinion 56 of the pinion shaft 54 and the rack teeth 62 of the rack shaft 16, and the rack shaft 16 is displaced in the vehicle width direction. As the rack shaft 16 is displaced, the tie rod 18 steers the front wheel 20 so that the direction of the vehicle can be changed.

3. Steering assist system (1) Assist drive system The motor 22 is connected to the rack shaft 16 via a worm gear 24 and a worm wheel gear 26. That is, the output shaft 22 a of the motor 22 is connected to the worm gear 24. The worm wheel gear 26 that meshes with the worm gear 24 is formed on the pinion shaft 54, and the pinion shaft 54 is connected to the rack shaft 16.

  The motor 22 is a three-phase AC brushless type, and power is supplied from the battery 34 via an inverter 36 controlled by the ECU 50. Then, a driving force (steering assist force) corresponding to the electric power is generated. The driving force is transmitted to the rack shaft 16 via the output shaft 22a, the worm gear 24, and the pinion shaft 54 (worm wheel gear 26 and pinion 56). This assists the driver's steering.

(2) Assist Control System (a) Feedforward Sensors The torque sensor 28 is provided between the intermediate bearing 60b and the upper bearing 60a of the pinion shaft 54, and is based on a change in magnetic characteristics due to magnetostriction. The steering torque Tr is detected and output to the ECU 50.

  The vehicle speed sensor 30 detects the vehicle speed V [km / h] and outputs it to the ECU 50. The steering angle sensor 32 detects the steering angle θs [degrees] of the steering handle 12 and outputs it to the ECU 50.

  The steering torque Tr, the vehicle speed V, and the steering angle θs are used for feedforward control in the ECU 50.

(B) Inverter 36
The inverter 36 has a three-phase full-bridge configuration, performs DC / AC conversion, converts DC from the battery 34 into three-phase AC, and supplies it to the motor 22.

  As shown in FIG. 2, the inverter 36 has three-phase arms 70u, 70v, and 70w. The U-phase arm 70u includes an upper arm element 72u having an upper switching element 74u (hereinafter referred to as “upper SW element 74u”) and a diode 76u, a lower switching element 80u (hereinafter referred to as “lower SW element 80u”), and a diode 82u. And the lower arm element 78u.

  Similarly, the V-phase arm 70v includes an upper switching element 74v (hereinafter referred to as “upper SW element 74v”) and an upper arm element 72v having a diode 76v, and a lower switching element 80v (hereinafter referred to as “lower SW element 80v”). And a lower arm element 78v having a diode 82v. The W-phase arm 70w includes an upper switching element 74w (hereinafter referred to as “upper SW element 74w”) and an upper arm element 72w having a diode 76w, a lower switching element 80w (hereinafter referred to as “lower SW element 80w”), and a diode 82w. And the lower arm element 78w.

  For the upper SW elements 74u, 74v, 74w and the lower SW elements 80u, 80v, 80w, for example, MOSFETs or IGBTs are employed.

  Hereinafter, the phase arms 70u, 70v, and 70w are collectively referred to as the phase arm 70, the upper arm elements 72u, 72v, and 72w are collectively referred to as the upper arm element 72, and the lower arm elements 78u, 78v, and 78w are The upper SW elements 74u, 74v, and 74w are collectively referred to as the upper SW element 74, and the lower SW elements 80u, 80v, and 80w are collectively referred to as the lower SW element 80.

  In each phase arm 70, midpoints 84 u, 84 v, 84 w of the upper arm element 72 and the lower arm element 78 are connected to the windings 86 u, 86 v, 86 w of the motor 22. Hereinafter, the windings 86u, 86v, and 86w are collectively referred to as a winding 86.

  Each upper SW element 74 and each lower SW element 80 are driven by drive signals UH, VH, WH, UL, VL, WL from the power ECU 50.

(C) Feedback system sensors The current sensor 38 detects a U-phase current (U-phase current Iu) in the winding 86 u of the motor 22 and outputs the detected current to the ECU 50. Similarly, current sensor 40 detects a W-phase current (W-phase current Iw) in winding 86 w and outputs the detected current to ECU 50. The current sensors 38 and 40 may detect currents other than the combination of the U phase and the W phase as long as they detect two of the three phases of the motor 22.

  The resolver 42 detects an electrical angle θ that is a rotation angle of an output shaft (not shown) of the motor 22 or an outer rotor.

  The voltage sensor 44 detects a voltage at the midpoint 84u of the U-phase arm 70u (hereinafter referred to as “U-phase voltage Vu”) and outputs the detected voltage to the ECU 50. Voltage sensor 46 detects a voltage at midpoint 84v of V-phase arm 70v (hereinafter referred to as “V-phase voltage Vv”) and outputs the detected voltage to ECU 50. Voltage sensor 48 detects a voltage at intermediate point 84w of W-phase arm 70w (hereinafter referred to as “W-phase voltage Vw”), and outputs the detected voltage to ECU 50.

(D) ECU 50
FIG. 3 shows the input and output to the ECU 50 and the internal configuration and functions of the ECU 50. The ECU 50 controls the output of the motor 22 based on the output value from each sensor.

  As shown in FIGS. 1 and 3, the ECU 50 includes an input / output unit 90, a calculation unit 92, and a storage unit 94 as a hardware configuration. As shown in FIG. 3, the calculation unit 92 of the ECU 50 includes an abnormality determination function 100, an abnormal phase identification function 102, and an energization control function 104. Among these, the energization control function 104 further includes a normal energization control function 106 and an abnormality energization control function 108. These functions are realized by executing a program stored in the storage unit 94 (details will be described later).

(3) Battery 34
The battery 34 is a power storage device that can output a low voltage (12 volts in the present embodiment), and for example, a secondary battery such as a lead storage battery can be used.

B. Processing and function of ECU 50 Overall Flow FIG. 4 is a flowchart showing the overall processing of the ECU 50 in the present embodiment. In step S <b> 1, the ECU 50 executes the normal energization control using the normal energization control function 106. In the normal energization control, the output of the motor 22 is controlled using the three phase arms 70 (FIG. 2) of the inverter 36 (details will be described later).

  In step S <b> 2, the ECU 50 calculates the rotational speed ω [degrees / sec] of the motor 22 based on the electrical angle θ from the resolver 42.

  In step S3, the ECU 50 determines whether or not the rotational speed ω calculated in step S2 is equal to or less than a threshold value TH_ω. The threshold value TH_ω is a threshold value for determining whether or not to perform the abnormality determination process in step S4. More specifically, the threshold value TH_ω is a threshold value for determining whether or not the motor 22 generates excessive back electromotive force as the accuracy of the abnormality determination process becomes insufficient, and is stored in the storage unit 94. Has been.

  When the rotational speed ω is not equal to or lower than the threshold value TH_ω (S3: NO), the process returns to step S1. When the rotational speed ω is equal to or lower than the threshold value TH_ω (S3: YES), in step S4, the ECU 50 executes an abnormality determination process using the abnormality determination function 100. If no abnormality has occurred as a result of the abnormality determination process in step S4 (S5: NO), the process returns to step S1.

  If an abnormality has occurred as a result of the abnormality determination process in step S4 (S5: YES), in step S6, the ECU 50 executes an abnormal phase identification process. Based on the result of the abnormal phase identification process, the ECU 50 executes an abnormality energization control in step S7 (details will be described later).

2. Normal energization control (normal energization control function 106)
FIG. 5 is a functional block diagram of the ECU 50 in the normal energization control. As shown in FIG. 5, the ECU 50 in the normal energization control includes a torque command value calculation unit 110, a phase compensation unit 112, a three-phase-dq conversion unit 114, a q-axis current target value calculation unit 116, a first Subtractor 118, q-axis PI control unit 120, d-axis current target value setting unit 122, second subtractor 124, d-axis PI control unit 126, dq-3 phase conversion unit 128, PWM control unit 130. The inverter 36 is controlled using these components. In addition, as a control system of the inverter 36, basically, those described in Patent Document 2 and Patent Document 3 can be used, and the components omitted in the present embodiment can be additionally applied. It is.

  The torque command value calculation unit 110 calculates the first torque command value Tr_c1 based on the steering torque Tr from the torque sensor 28 and the vehicle speed V from the vehicle speed sensor 30. The phase compensation unit 112 performs a phase compensation process on the first torque command value Tr_c1 to calculate a second torque command value Tr_c2.

  The three-phase-dq converter 114 performs three-phase-dq conversion using the U-phase current Iu from the current sensor 38, the W-phase current Iw from the current sensor 40, and the electrical angle θ from the resolver 42, A d-axis current Id as a current component (field current component) in the d-axis direction and a q-axis current Iq as a current component (torque current component) in the q-axis direction are calculated. Then, the three-phase-dq converter 114 outputs the q-axis current Iq to the first subtractor 118 and outputs the d-axis current Id to the second subtractor 124.

  In the three-phase-dq conversion, a set of a U-phase current Iu, a W-phase current Iw, and a V-phase current Iw (= −Iu−Iw) obtained from these is converted by a conversion matrix corresponding to the electrical angle θ. This is a process of converting into a set of d-axis current Id and q-axis current Iq.

  The q-axis current target value calculation unit 116 includes the second torque command value Tr_c2 from the phase compensation unit 112, the vehicle speed V from the vehicle speed sensor 30, the steering angle θs from the steering angle sensor 32, and the electrical angle from the resolver 42. Based on θ, a q-axis current target value Iq_t that is a target value of the q-axis current Iq is calculated. For example, the q-axis current target value calculation unit 116 calculates the q-axis current target value Iq_t by combining the reference assist control, the inertia control, and the damper control. For the reference assist control, the inertia control, and the damper control, for example, those described in Patent Document 2, Patent Document 3, or JP 2009-214711 A can be used. This d-axis current target value Id_t has a meaning as a feedforward command value for the d-axis current and the q-axis current for generating the torque of the second torque command value Tr_c2 on the output shaft 22a of the motor 22.

  The first subtractor 118 calculates a deviation (= Iq_t−Iq) between the q-axis current target value Iq_t and the q-axis current Iq (hereinafter referred to as “q-axis current deviation ΔIq”) and sends it to the q-axis PI control unit 120. Output. The q-axis PI control unit 120 calculates a q-axis voltage target value Vq_t that is a target value of the q-axis voltage by PI control (proportional / integral control) as feedback control so that the q-axis current deviation ΔIq approaches zero. And output to the dq-3 phase converter 128.

  The d-axis current target value setting unit 122 sets a target value of the d-axis current Id (hereinafter referred to as “d-axis current target value Id_t”) necessary for using the winding 86 of the motor 22 as a magnet, and a second subtractor. It outputs to 124.

  The second subtractor 124 calculates a deviation (= Id_t−Id) between the d-axis current target value Id_t and the d-axis current Id (hereinafter referred to as “d-axis current deviation ΔId”) and sends it to the d-axis PI control unit 126. Output. The d-axis PI control unit 126 calculates a d-axis voltage target value Vd_t that is a target value of the d-axis voltage by PI control (proportional / integral control) as feedback control so that the d-axis current deviation ΔId approaches zero. And output to the dq-3 phase converter 128.

  The dq-3 phase conversion unit 128 calculates the q-axis voltage target value Vq_t from the q-axis PI control unit 120, the d-axis voltage target value Vd_t from the d-axis PI control unit 126, and the electrical angle θ from the resolver 42. Then, dq-3 phase conversion is performed, and phase voltage target values Vu_t, Vv_t, and Vw_t for the U phase, the V phase, and the W phase are calculated and output to the PWM control unit 130. The dq-3 phase conversion is a process of converting a set of the d-axis voltage target value Vd_t and the q-axis voltage target value Vq_t into a set of phase voltage target values Vu_t, Vv_t, and Vw_t using a conversion matrix corresponding to the electrical angle θ. It is.

  The PWM control unit 130 energizes the winding 86 of each phase of the motor 22 via the inverter 36 by pulse width modulation (PWM) control according to these phase voltage target values Vu_t, Vv_t, and Vw_t. The PWM control unit 130 energizes the winding 86 of each phase by controlling on / off of each upper SW element 74 and each lower SW element 80 of the inverter 36.

  More specifically, the PWM control unit 130 generates drive signals UH, UL, VH, VL, WH, and WL for each phase arm 70 for each switching period. Here, assuming that the duty value DUT in one entire switching cycle is 100%, the duty value DUT2 of the lower SW element 80 is calculated as 100% minus the duty value DUT1 to the upper SW element 74, and further, The drive signals UH, UL, VH, VL, WH, WL that are actually output are obtained by reflecting the dead time dt in the duty values DUT1, DUT2 of the SW element 74 and the lower SW element 80, respectively.

  When the normal energization control as described above is used, torque generated by each phase in the normal energization control (hereinafter referred to as “U-phase torque Tr_u”, “V-phase torque Tr_v”, and “W-phase torque Tr_w”), The total torque output by the motor 22 (hereinafter referred to as “motor torque Tr_m”) and current in each phase (hereinafter referred to as “U-phase current Iu”, “V-phase current Iv”, and “W-phase current Iw”). For example, the waveform shown in FIG. 6 can be obtained.

3. Abnormality determination processing (abnormality determination function 100)
FIG. 7 is a flowchart (details of S4 in FIG. 4) of the abnormality determination process (abnormality determination function 100) by the ECU 50. In step S11, the ECU 50 calculates the d-axis voltage Vd and the q-axis voltage Vq by calculation. Specifically, the ECU 50 uses the electrical angle θ to convert the U-phase voltage Vu from the voltage sensor 44, the V-phase voltage Vv from the voltage sensor 46, and the W-phase voltage Vw from the voltage sensor 48 into three-phase − dq conversion is performed to obtain a d-axis voltage Vd and a q-axis voltage Vq.

  In step S12, the ECU 50 determines whether or not the q-axis voltage Vq obtained in step S11 exceeds a threshold value TH_Vq. The threshold value TH_Vq is a threshold value for determining whether or not the q-axis voltage Vq is output.

  When the q-axis voltage Vq does not exceed the threshold value TH_Vq (S12: NO), in step S13, the ECU 50 determines that no abnormality has occurred, and returns to the process of FIG. When the q-axis voltage Vq exceeds the threshold value TH_Vq (S12: YES), the process proceeds to step S14.

  In step S14, the ECU 50 determines whether or not the q-axis current Iq is zero. Thereby, it can be determined whether or not the q-axis current Iq is generated. Instead of the determination, a positive threshold is provided for the absolute value of the q-axis current Iq, and it is determined whether or not the q-axis current Iq is equal to or less than the threshold, whereby the q-axis current corresponding to the q-axis voltage Vq is determined. Whether or not Iq has occurred can also be determined.

  If the q-axis current Iq is not zero (S14: NO), the process proceeds to step S13. When the q-axis current Iq is zero (S14: YES), the q-axis current Iq is not flowing even though the q-axis voltage Vq is output. In this case, it can be said that an abnormality (for example, disconnection of the power line or the signal line from the PWM control unit 130 to each of the SW elements 74 and 80) in which no current occurs in any of the phases (phase arm 70) occurs. Therefore, the ECU 50 identifies the occurrence of an abnormality in step S15 (at this time, the phase in which an abnormality has occurred is not identified).

4). Abnormal phase identification processing (abnormal phase identification function 102)
FIG. 8 is a flowchart of the abnormal phase identification process (abnormal phase identification function 102) by the ECU 50 (details of S6 in FIG. 4). In step S21, the ECU 50 determines that the absolute value of the correlation voltage between the V-phase voltage Vv from the voltage sensor 46 and the W-phase voltage Vw from the voltage sensor 48 (hereinafter referred to as “VW interphase voltage Vvw”) is less than the threshold value THv. It is determined whether or not there is. The VW phase voltage Vvw is defined as the difference between the V phase voltage Vv and the W phase voltage Vw (Vvw = Vv−Vw). The threshold value THv is for determining whether or not the VW interphase voltage Vvw is zero or a value in the vicinity thereof (in other words, whether or not the V phase voltage Vv and the W phase voltage Vw are substantially equal).

  When the absolute value of the VW interphase voltage Vvw is less than the threshold value THv (S21: YES), the VW interphase voltage Vvw is substantially zero, and it can be seen that the V phase and the W phase function normally. For this reason, it is understood that an abnormality such as disconnection occurs in the U phase. Therefore, in step S22, the ECU 50 specifies that an abnormality has occurred in the U phase. When the absolute value of the VW interphase voltage Vvw is not less than the threshold value THv (S21: NO), the process proceeds to step S23.

  In step S23, the ECU 50 has an absolute value of a correlation voltage between the W-phase voltage Vw from the voltage sensor 48 and the U-phase voltage Vu from the voltage sensor 44 (hereinafter referred to as “WU-phase voltage Vwu”) less than the threshold value THv. It is determined whether or not. The WU phase voltage Vwu is defined as the difference between the W phase voltage Vw and the U phase voltage Vu (Vwu = Vw−Vu). This makes it possible to determine whether or not the WU phase voltage Vwu is zero or a value in the vicinity thereof (in other words, whether or not the W phase voltage Vw and the U phase voltage Vu are substantially equal).

  When the absolute value of the WU interphase voltage Vwu is less than the threshold value THv (S23: YES), the WU interphase voltage Vwu is substantially zero, and it can be seen that the W phase and the U phase function normally. For this reason, it is understood that abnormality such as disconnection occurs in the V phase. Therefore, in step S24, the ECU 50 specifies that an abnormality has occurred in the V phase. When the absolute value of the WU interphase voltage Vwu is not less than the threshold value THv (S23: NO), the process proceeds to step S25.

  In step S25, the ECU 50 determines that the absolute value of the correlation voltage (hereinafter referred to as “UV phase voltage Vuv”) between the U-phase voltage Vu from the voltage sensor 48 and the V-phase voltage Vv from the voltage sensor 46 is less than the threshold THv. It is determined whether or not. The UV phase voltage Vuv is defined as the difference between the U phase voltage Vu and the V phase voltage Vv (Vuv = Vu−Vv). Thereby, it is possible to determine whether or not the UV phase voltage Vuv is zero or a value in the vicinity thereof (in other words, whether or not the U phase voltage Vu and the V phase voltage Vv are substantially equal).

  When the absolute value of the UV phase voltage Vuv is less than the threshold value THv (S25: YES), the UV phase voltage Vuv is substantially zero, indicating that the U phase and the V phase are functioning normally. For this reason, it is understood that an abnormality such as disconnection occurs in the W phase. Therefore, in step S26, the ECU 50 specifies that an abnormality has occurred in the W phase. When the absolute value of the UV phase voltage Vuv is not less than the threshold value THv (S25: NO), the phase in which an abnormality has occurred (abnormal phase) cannot be specified. As such a case, for example, it is conceivable that an abnormality occurs in two phases and no current flows. In this case, in step S27, the ECU 50 determines that the abnormal phase cannot be specified. And the motor 22 is stopped by the fail safe function which ECU50 has.

5. Energization control when an abnormality occurs (Energization control function when an abnormality occurs 108)
(1) Overall FIG. 9 is a functional block diagram of the ECU 50 in the abnormality energization control. In the following, the same components as those in FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 9, the ECU 50 in the abnormality energization control includes a torque command value calculation unit 110, a phase compensation unit 112, a gain setting unit 140, an abnormal phase identification function 102, a reference voltage calculation unit 142, A rotation speed calculation unit 144, a correction voltage calculation unit 146, a first adder 148, a second adder 150, a third adder 152, and a PWM control unit 130 are included. The inverter 36 is controlled using these components.

(2) Torque command value calculation unit 110 and phase compensation unit 112
Similar to the normal energization control, the torque command value calculation unit 110 calculates the first torque command value Tr_c1 based on the steering torque Tr from the torque sensor 28 and the vehicle speed V from the vehicle speed sensor 30. The phase compensation unit 112 performs a phase compensation process on the first torque command value Tr_c1 to calculate a second torque command value Tr_c2.

(3) Gain setting unit 140
FIG. 10 is a functional block diagram of the gain setting unit 140. The gain setting unit 140 calculates the gain Gph based on the second torque command value Tr_c2 and the vehicle speed V. As shown in FIG. 10, the gain setting unit 140 includes an absolute value conversion unit 160, an output voltage table 162 for two-phase energization, a vehicle speed gain table 164 for two-phase energization, a first multiplier 166, a rate A limit processing unit 168, a sine converter 170, and a second multiplier 172 are included.

  The absolute value conversion unit 160 calculates and outputs the absolute value of the second torque command value Tr_c2. The output voltage table 162 for two-phase energization outputs an output voltage Vout corresponding to the absolute value of the second torque command value Tr_c2. The output voltage Vout sets the output of the motor 22 according to the second torque command value Tr_c2.

  The vehicle speed gain table 164 for two-phase energization outputs a ratio R1 corresponding to the vehicle speed V. The ratio R1 is used, for example, to reduce the output of the motor 22 and prevent the steering handle 12 from being cut too much when the vehicle speed V is high. The first multiplier 166 calculates and outputs a product Vout × R1 of the output voltage Vout and the ratio R1. The product Vout × R1 is a value reflecting the vehicle speed V in the steering torque Tr by the driver.

  The rate limit processing unit 168 performs adjustment so that the absolute value of the deviation ΔD between the previous value and the current value of the product Vout × R1 does not exceed the positive threshold value TH_ΔD. That is, when the absolute value of the deviation ΔD is equal to or smaller than the threshold value TH_ΔD, the deviation ΔD is output as it is as the update value P1. When the deviation ΔD is a positive value larger than the threshold value TH_ΔD, the threshold value TH_ΔD is output as the update value P1. When the deviation ΔD is smaller than the value obtained by multiplying the threshold value TH_ΔD by minus 1 (ΔD <−TH_ΔD), a value obtained by multiplying the threshold value TH_ΔD by minus 1 is output as the update value P1.

  The sine converter 170 outputs 1 when the second torque command value Tr_c2 is positive, and outputs -1 when the second torque command value Tr_c2 is negative. By using the sine converter 170, the steering direction can be distinguished between right and left.

  The second multiplier 172 outputs the product of the update value P1 and the output value (−1 or 1) from the sine converter 170 as the gain Gph.

(4) Reference voltage calculation unit 142
Returning to FIG. 9, the reference voltage calculation unit 142 determines the reference voltage Vu_base of each phase based on the gain Gph, the electrical angle θ, and the identification result of the abnormal phase identification function 102 (which phase is abnormal). Vv_base and Vw_base are calculated.

Specifically, when an abnormality occurs in the U phase, the reference voltages Vu_base, Vv_base, and Vw_base are calculated using the following equations (1) to (6). The reference voltages Vu_base, Vv_base, and Vw_base are phase voltage gains set according to the driver's steering operation.
(A) When 0 ° ≦ Φ <180 ° Vu_base = 0 (1)
Vv_base = Gph × (1−0.5 sinΦ) (2)
Vw_base = −Gph × (1−0.5 sinΦ) (3)
(B) When 180 ° ≦ Φ <360 ° Vu_base = 0 (4)
Vv_base = Gph × (−1−0.5 sinΦ) (5)
Vw_base = −Gph × (−1−0.5 sinΦ) (6)

  In the above formulas (1) to (6), Φ is defined as the sum of the electrical angle θ and 270 ° (Φ = θ + 270). However, 0 ° ≦ Φ <360 °. Accordingly, the reference voltages Vu_base, Vv_base, and Vw_base are, for example, as illustrated in FIG. When an abnormality occurs in the U phase, the steering assist force of the motor 22 is not generated when the electrical angle θ is 90 ° and 270 ° in the normal energization control (three-phase energization control). However, in the abnormality energization control, the reference voltages Vv_base and Vw_base are increased in the vicinity of the electrical angle θ of 90 ° and 270 ° as shown in FIG. As a result, it is possible to reduce the influence that the steering assist force of the motor 22 is not generated when the electrical angle θ is 90 ° and 270 °.

When an abnormality occurs in the V phase, the reference voltages Vu_base, Vv_base, and Vw_base are calculated using the following equations (7) to (12).
(C) When 0 ° ≦ Φ <180 ° Vv_base = 0 (7)
Vw_base = Gph × (1−0.5 sinΦ) (8)
Vu_base = −Gph × (1−0.5 sinΦ) (9)
(D) When 180 ° ≦ Φ <360 ° Vv_base = 0 (10)
Vw_base = Gph × (−1−0.5 sinΦ) (11)
Vu_base = −Gph × (−1−0.5 sinΦ) (12)

  In the above formulas (7) to (12), Φ is defined as the sum of the electrical angle θ and 150 ° (Φ = θ + 150). However, 0 ° ≦ Φ <360 °. Accordingly, the reference voltages Vu_base, Vv_base, and Vw_base are, for example, as illustrated in FIG. If an abnormality has occurred in the V phase, the steering assist force of the motor 22 is not generated when the electrical angle θ is 30 ° and 210 ° in the normal energization control (three-phase energization control). However, in the abnormality energization control, the reference voltages Vw_base and Vu_base are increased when the electrical angle θ is in the vicinity of 30 ° and 210 ° as shown in FIG. As a result, it is possible to reduce the influence that the steering assist force of the motor 22 is not generated when the electrical angle θ is 30 ° and 210 °.

When abnormality occurs in the W phase, the reference voltages Vu_base, Vv_base, and Vw_base are calculated using the following equations (13) to (18).
(E) When 0 ° ≦ Φ <180 ° Vw_base = 0 (13)
Vu_base = Gph × (1−0.5 sinΦ) (14)
Vv_base = −Gph × (1−0.5 sinΦ) (15)
(F) When 180 ° ≦ Φ <360 ° Vw_base = 0 (16)
Vu_base = Gph × (−1−0.5 sinΦ) (17)
Vv_base = −Gph × (−1−0.5 sinΦ) (18)

  In the above formulas (13) to (18), Φ is defined as the sum of the electrical angle θ and 30 ° (Φ = θ + 30). However, 0 ° ≦ Φ <360 °. Accordingly, the reference voltages Vu_base, Vv_base, and Vw_base are, for example, as illustrated in FIG. If an abnormality has occurred in the W phase, the steering assist force of the motor 22 is not generated when the electrical angle θ is 150 ° and 330 ° in the normal-time energization control (three-phase energization control). However, in the abnormality energization control, the reference voltages Vu_base and Vv_base are increased when the electrical angle θ is in the vicinity of 150 ° and 330 ° as shown in FIG. As a result, it is possible to reduce the influence that the steering assist force of the motor 22 is not generated when the electrical angle θ is 150 ° and 330 °.

(5) Rotational speed calculation unit 144
The rotation speed calculation unit 144 in FIG. 9 calculates the rotation speed ω of the motor 22 based on the electrical angle θ from the resolver 42.

(6) Correction voltage calculation unit 146
The correction voltage calculation unit 146 determines the correction voltages Vu_emf, Vv_emf, and Vw_emf for each phase based on the electrical angle θ, the rotational speed ω, and the specification result of the abnormal phase specification function 102 (which phase is abnormal). calculate. The correction voltages Vu_emf, Vv_emf, and Vw_emf are for canceling the induced voltage caused by the motor 22.

Specifically, when an abnormality occurs in the U phase, the correction voltages Vu_emf, Vv_emf, and Vw_emf are calculated using the following equations (19) to (21).
Vu_emf = 0 (19)
Vv_emf = − (√3 / 2) Ke × ω × sinΦ (20)
Vw_emf = (√3 / 2) Ke × ω × sinΦ (21)

  In the above formulas (19) to (21), Φ is defined as the sum of the electrical angle θ and 270 ° (Φ = θ + 270). However, 0 ° ≦ Φ <360 °. Ke is a one-phase induced voltage constant. “√3 / 2” is a coefficient for converting the induced voltage from a three-phase component to a two-phase component.

When an abnormality occurs in the V phase, the correction voltages Vu_emf, Vv_emf, and Vw_emf are calculated using the following equations (22) to (24).
Vv_emf = 0 (22)
Vw_emf = − (√3 / 2) Ke × ω × sinΦ (23)
Vu_emf = (√3 / 2) Ke × ω × sinΦ (24)

  In the above formulas (22) to (24), Φ is defined as the sum of the electrical angle θ and 150 ° (Φ = θ + 150). However, 0 ° ≦ Φ <360 °.

When an abnormality occurs in the W phase, the correction voltages Vu_emf, Vv_emf, and Vw_emf are calculated using the following equations (25) to (27).
Vw_emf = 0 (25)
Vu_emf = − (√3 / 2) Ke × ω × sinΦ (26)
Vv_emf = (√3 / 2) Ke × ω × sinΦ (27)

  In the above formulas (25) to (27), Φ is defined as the sum of the electrical angle θ and 30 ° (Φ = θ + 30). However, 0 ° ≦ Φ <360 °.

(7) First adder 148, second adder 150, and third adder 152
The first adder 148 in FIG. 9 outputs the sum of the U-phase reference voltage Vu_base and the correction voltage Vu_emf as the U-phase voltage target value Vu_t. The second adder 150 outputs the sum of the V-phase reference voltage Vv_base and the correction voltage Vv_emf as the V-phase voltage target value Vv_t. The third adder 152 outputs the sum of the W-phase reference voltage Vw_base and the correction voltage Vw_emf as the W-phase voltage target value Vw_t.

(8) PWM controller 130
Similar to the normal energization control, the PWM control unit 130 energizes the winding 86 of each phase of the motor 22 via the inverter 36 by pulse width modulation (PWM) control according to the phase voltage command values Vu_t, Vv_t, and Vw_t. To do. The PWM control unit 130 energizes the windings 86 of each phase by controlling on / off of the SW elements 74 and 80 of the inverter 36.

C. As described above, according to the present embodiment, the interphase voltage is in the vicinity of zero volts when the q-axis current Iq is zero despite the q-axis voltage Vq being applied. A phase other than the combination phase is detected as an abnormal phase (FIG. 8). For this reason, even if it has composition which has only two current sensors 38 and 40 for phase current detection, detection of an abnormal phase is attained.

  In the present embodiment, the abnormality determination process is performed when the rotation speed ω of the motor 22 is equal to or less than the threshold value TH_ω. Thereby, when the back electromotive force by the motor 22 adversely affects the specific accuracy of the abnormal phase, it is possible to prevent erroneous detection by specifying the abnormal phase only when the specific accuracy is ensured. It becomes possible.

  In the present embodiment, when the ECU 50 detects an abnormal phase during the normal-time energization control, the motor 22 has an output near the electrical angle θ where the output of the motor 22 decreases due to the abnormal phase not functioning. A phase other than the abnormal phase is driven so as to increase the output. Thereby, even when an abnormal phase exists, it is possible to suppress a sudden decrease in the output of the motor 22 and to stably generate the steering assist force from the motor 22.

II. Modifications It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification. For example, the following configuration can be adopted.

A. Identification of Abnormal Phase In the above embodiment, the q-axis current Iq is zero (S14 in FIG. 7) as a criterion for determining whether or not an abnormality has occurred in any phase. However, the present invention is not limited to this, and a positive threshold value and a negative threshold value near zero may be provided, and the determination criterion may be that the q-axis current Iq is in between. Alternatively, the determination criterion may be that the absolute value of the q-axis current Iq is equal to or less than a positive threshold value near zero.

B. 14 to 19 are first to sixth modifications of the relationship between the electrical angle θ of the motor 22 and the output voltage of each phase in the abnormality energization control. An example is shown. In other words, the examples of FIGS. 14 to 19 show modified examples of processing in the gain setting unit 140. 14 to 19 are based on the assumption that the W phase is disconnected.

  FIG. 14 shows an example in which the U-phase voltage Vu and the V-phase voltage Vv are output in a trapezoidal wave according to the electrical angle θ, the second torque command value Tr_c2, and the vehicle speed V.

  FIG. 15 is an example in which the U-phase voltage Vu and the V-phase voltage Vv are output in a waveform of “(1−0.5 sin θ)” according to the electrical angle θ, the second torque command value Tr_c2, and the vehicle speed V.

  FIG. 16 is an example in which the U-phase voltage Vu and the V-phase voltage Vv are output in a waveform of “1 / cos (θ−60 °)” according to the electrical angle θ, the second torque command value Tr_c2, and the vehicle speed V. . However, limit control is performed for a voltage that is greater than 1.5 times the maximum voltage in normal energization control.

  FIG. 17 is an example in which the U-phase voltage Vu and the V-phase voltage Vv are output in a waveform of “1 / cos (θ−60 °)” according to the electrical angle θ, the second torque command value Tr_c2, and the vehicle speed V. . However, limit control is performed for a voltage that is greater than twice the maximum voltage in normal energization control.

  FIG. 18 is an example in which the U-phase voltage Vu and the V-phase voltage Vv are output in a waveform of “1 / cos (θ−60 °)” according to the electrical angle θ, the second torque command value Tr_c2, and the vehicle speed V. . However, limit control is performed for a voltage that is greater than three times the maximum voltage in normal energization control.

  FIG. 19 is an example in which the U-phase voltage Vu and the V-phase voltage Vv are output in a waveform of “1 / cos (θ−60 °)” according to the electrical angle θ, the second torque command value Tr_c2, and the vehicle speed V. .

C. Use of Rotational Speed ω of Motor 22 In the above embodiment, the rotational speed ω is compared with the threshold value TH_ω, and abnormality determination processing is performed only when the rotational speed ω is equal to or lower than the threshold value TH_ω (FIG. 4). However, a configuration in which the rotation speed ω is not compared with the threshold value TH_ω is also possible.

DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus 22 ... Motor 36 ... Inverter 50 ... ECU (Current coordinate conversion means, voltage coordinate conversion means, abnormal phase detection means, rotational speed detection means)

Claims (3)

An inverter that supplies three-phase AC power to the motor;
Current coordinate conversion means for converting the current flowing in the three phases into a dq coordinate current of a d-axis current that is an excitation current component and a q-axis current that is a torque current component;
Voltage coordinate conversion means for converting a three-phase voltage applied to the motor into a d-axis voltage and a q-axis voltage;
An abnormal phase in which a phase other than the combination phase in which the interphase voltage is near zero volts is detected as an abnormal phase when the q-axis current is equal to or lower than the first threshold value even though the q-axis voltage is applied. An electric power steering apparatus comprising: detecting means. The electric power steering apparatus according to claim 1,
Furthermore, a rotation speed detecting means for detecting the rotation speed of the motor is provided,
The electric power steering apparatus, wherein the abnormal phase detection means is operated when the rotation speed is equal to or lower than a second threshold value. In the electric power steering apparatus according to claim 1 or 2,
When driving all three phases, if the abnormal phase detection means detects an abnormal phase, the motor output is reduced in the vicinity of an electrical angle at which the motor output decreases due to the abnormal phase not functioning. An electric power steering apparatus, wherein a phase other than the abnormal phase is driven so as to increase.

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