Motor control device and electric power steering device

Abstract

This motor control device comprises: an abnormal torque estimation unit (16) for estimating an abnormality of the torque of a motor from a target current value determined by a current command calculation unit (3), a detection current value obtained by a detection phase-current calculation unit (15), and an electrical angle calculated by an electrical angle calculation unit (14); and a cut-off management unit (17) for stopping driving of the motor if the output torque is abnormal.

Description

[Technical field]

[0001] The present application relates to a motor control device and an electric power steering device using the same. [Background technology]

[0002] Generally, a polyphase motor is equipped with a fault detection device for detecting a fault. If the fault detection device detects a fault, it stops driving the motor to prevent the motor from performing unintended operations.

[0003] However, if the detected fault means that it is possible to continue driving the motor, it is desirable to continue driving it. However, conventional fault detection devices are unable to determine whether or not it is possible to continue driving the motor in response to a detected fault, and there is a problem in that the motor drive is stopped as soon as a fault is detected.

[0004] To solve this problem, Patent Document 1 proposes a motor control device that determines whether or not the motor can continue to be driven in the event of a fault detected by a fault detection device, and continues to drive the motor if possible.If an abnormal current value is detected by a current value abnormality detection means from a current detected by a current detection means provided in the motor, and the current value abnormality is due to a fault in the current detection means itself, the detected current is switched to an estimated current, and the motor continues to be driven. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5092538 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, the motor control device disclosed in Patent Document 1 targets the current detection means as a fault detection device, and when the current detection means detects an abnormality in the detected current value, it determines that the motor can continue to be driven only if the cause of the abnormality is the current detection means itself, resulting in the problem that it is not possible to determine whether the motor can continue to be driven based on the extent of the impact that the occurring fault will have on the output (system) of the motor control device.

[0007] The present application has been made to solve the above-mentioned problems, and aims to provide a motor control device that can appropriately determine whether or not to continue driving a motor even when an abnormality occurs in the output torque of the motor. [Means for solving the problem]

[0008] The motor control device disclosed in the present application includes a current command calculation unit that determines a target current value for a multi-phase motor, a detected phase current calculation unit that detects currents of each phase flowing through the motor to obtain detected current values, a control calculation unit that calculates a current command to control the motor current based on the target current value and the detected current value, an electrical angle calculation unit that calculates an electrical angle, which is a phase difference between the rotor rotation position and the motor coil, based on the rotor rotation position of the motor, and a control circuit that calculates a current command based on the target current value, the detected current value, and the electrical angle. The current deviation, which is the difference between the target current value and the detected current value, is calculated for each phase, and based on the difference between the maximum current deviation value, which is the maximum value of the current deviation, and the minimum current deviation value, which is the minimum value of the current deviation, The system is equipped with an abnormal torque estimation unit that estimates an abnormality in the torque of the motor, and a shutoff management unit that stops the drive of the motor if the torque is abnormal. Effect of the Invention

[0009] According to the motor control device disclosed in the present application, even when an abnormality occurs in the output torque of the motor, it is possible to appropriately determine whether or not to continue driving the motor. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an electric power steering device including a motor control device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing an overview of the operation of the electric power steering device according to the first embodiment. [Diagram 3] 3 is a diagram showing an outline of a time chart of a target current and a detected current of a motor in the operational processing of the electric power steering device according to the first embodiment. FIG. [Figure 4] 2 is a block diagram showing an example of a processing configuration of an abnormal torque estimation unit in the electric power steering device according to the first embodiment. FIG. [Diagram 5] 4 is a flowchart showing the processing contents in an abnormal torque estimation unit of the electric power steering device according to the first embodiment. FIG. [Figure 6] 4 is a flowchart showing the contents of a current deviation calculation process in an abnormal torque estimating section of the electric power steering device according to the first embodiment. FIG. [Figure 7] 4 is a flowchart showing a process of selecting a minimum value of a current deviation in an abnormal torque estimating section of the electric power steering device according to the first embodiment. FIG. [Figure 8] 4 is a flowchart showing a process of selecting a maximum value of a current deviation in an abnormal torque estimating section of the electric power steering device according to the first embodiment. FIG. [Figure 9] 4 is a diagram showing an outline of a time chart when a deviation occurs between a target current and a detected current of a motor in the operational processing of the electric power steering device according to the first embodiment. FIG. [Figure 10] 3 is a diagram showing an outline of a time chart of the electrical angle θ in the operational processing of the electric power steering device according to the first embodiment. FIG. [Figure 11] 4 is a block diagram showing another example of the processing configuration of the abnormal torque estimating section in the electric power steering device according to the first embodiment. FIG. [Figure 12] 12 is a flowchart showing the process of calculating an abnormal torque estimated value in FIG. 11. [Figure 13] 4 is a flowchart showing internal processing of a cutoff management unit of the electric power steering device according to the first embodiment. FIG. [Figure 14] 1 is a diagram illustrating an example of a hardware configuration of a motor control device according to an embodiment; [Figure 15]10 is a block diagram showing an electric power steering device including a motor control device according to a second embodiment. FIG. [Figure 16] FIG. 11 is a flowchart showing the processing contents of an open circuit failure determination unit of the electric power steering device according to the second embodiment. [Figure 17] 11 is a flowchart showing the processing contents of a U-phase open circuit fault determination process in an open circuit fault determination unit of an electric power steering device according to Embodiment 2. FIG. [Figure 18] 11 is a flowchart showing the processing contents of a V-phase open circuit fault determination process in an open circuit fault determination unit of an electric power steering device according to Embodiment 2. FIG. [Figure 19] 11 is a flowchart showing the processing contents of a W-phase open fault determination process in an open fault determination unit of an electric power steering device according to Embodiment 2. FIG. [Figure 20] FIG. 11 is a flowchart showing internal processing of a cutoff management unit of the electric power steering device according to the second embodiment. [Figure 21] FIG. 2 is a schematic diagram showing a motor represented as a simple resistor model. [Figure 22] FIG. 1 is a schematic diagram showing a motor when a U-phase open fault occurs, represented as a simple resistor model. [Diagram 23] FIG. 4 is a schematic diagram of target three-phase currents in a normal state. [Figure 24] FIG. 13 is a schematic diagram of detected three-phase currents when a U-phase open fault occurs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a motor control device and an electric power steering device including the motor control device will be described with reference to the drawings.

[0012] Embodiment 1 1 is an overall configuration diagram showing one example of an electric power steering device according to embodiment 1, and includes a motor control device 100 having a current command calculation unit 3 that controls the output torque of a motor 10 that is connected to a gear 11 and outputs a steering assist torque that assists the driver's steering, based on a detected torque Td output by a torque detector 2 that detects a steering torque from a driver acting on a steering wheel 1 of a vehicle steered by the driver and outputs the detected torque Td to the outside, and wheels 12 are steered by the driver's steering torque and the steering assist torque output by the motor 10. The current command calculation unit 3 determines a target current value corresponding to a motor current value of the motor 10.

[0013] Motor 10 is a multi-phase motor, for example a star-connected surface magnet type three-phase brushless motor in which one ends of the U-phase coil, V-phase coil, and W-phase coil are connected to each other, and the other end of each coil is connected to motor drive device 7 via motor current cut-off unit 9. Motor drive device 7 applies a motor drive voltage to each coil, and current flows in each coil according to the voltage applied to each phase.

[0014] A rotor rotational position detector 13 detects the rotor rotational position of the motor 10, and an electrical angle calculation unit 14 calculates an electrical angle θ, which is the phase difference between the rotor rotational position detected by the rotor rotational position detector 13 and the three-phase coils.

[0015] The motor drive device 7 is connected to the motor 10 via the motor current cutoff unit 9, and is composed of, for example, two series-connected field effect transistors QHu and QLu, a series circuit of two similar field effect transistors QHv and QLv connected in parallel to the series circuit, and a series circuit of field effect transistors QHw and QLw. A pulse width modulation (PWM) signal output from the control calculation unit 4 is converted by a FET gate drive unit 6, which is, for example, a FET gate driver IC, into a voltage level that enables gate driving of the field effect transistors QHu, QLu, QHv, QLv, QHw, and QLw in the motor drive device 7 connected in the downstream stage. By driving these field effect transistors (FETs) QHu, QLu, QHv, QLv, QHw, and Qlw in response to the gate drive signal output from the FET gate drive unit 6 after conversion, a predetermined phase voltage is applied to each coil of the motor 10 connected in the downstream stage, and a phase current flows in the motor 10, generating torque in the motor 10.

[0016] Furthermore, the motor drive device 7 includes shunt resistors 8u, 8v, and 8w for detecting the phase currents flowing through the coils of the motor 10.

[0017] The detected phase current calculation unit 15 calculates the phase current I flowing through each phase coil of the motor 10 from the values ​​detected by the shunt resistors 8u, 8v, and 8w. u , I v , I w Calculate.

[0018] The current command calculation unit 3 calculates a q-axis current command and a d-axis current command, which are current commands on two rotation axes (dq axes), from the motor speed calculated using the detected torque Td detected by the torque detector 2, the vehicle speed signal Sv acquired by an external device, and the electrical angle θ from the electrical angle calculation unit 14. This q-axis current command is a target q-axis current I q_t The d-axis current command is expressed as the target d-axis current I d_t It is shown as:

[0019] When the output signal from the interruption management unit 17 is not the PWM signal forced off instruction INoff, the control calculation unit 4 outputs the target q-axis current I q_t and the target d-axis current I d_t and the detected phase current I u , I v , I w The detected current I is converted into a current on two rotation axes (dq axes) from three-phase to two-phase. q_m , I d_m Using these, a known control calculation process, for example a PI control process, is performed, and a U-phase PWM signal S-PWM(U), a V-phase PWM signal S-PWM(V), and a W-phase PWM signal S-PWM(W) corresponding to the results of the process are formed and output to the downstream FET gate drive cutoff unit 5. When the output signal from the cutoff management unit 17 is a PWM signal forced off instruction INoff, the target q-axis current I q_t and the target d-axis current I d_t and the detected phase current I u , I v , I w The detected current I is converted into a current on two rotation axes (dq axes) from three-phase to two-phase. q_m , I d_m Regardless of the above, the PWM circuit 30 forms a U-phase PWM signal S-PWM(U), a V-phase PWM signal S-PWM(V), and a W-phase PWM signal S-PWM(W) such that no PWM is applied to each phase of the motor 10, and outputs these to the downstream FET gate drive cutoff unit 5.

[0020] The motor current interruption unit 9 is inserted in the current path between the motor drive device 7 and the motor 10, and cuts off the current path in accordance with a motor current interruption instruction INci from the interruption management unit 17, thereby setting the output torque of the motor 10 to 0 (zero).

[0021] The FET gate drive cutoff unit 5 is disposed on the path between the control calculation unit 4 and the FET gate drive unit 6, and has a function of forcibly cutting off the U-phase PWM signal S-PWM(U), V-phase PWM signal S-PWM(V), and W-phase PWM signal S-PWM(W) to the FET gate drive unit 6 by, for example, stopping the gate drive of the FET gate driver IC which is the FET gate drive unit 6 in accordance with a FET gate drive cutoff instruction INcg from the cutoff management unit 17, and this function stops the supply of phase voltages to each coil of the motor 10.

[0022] The current command calculation unit 3 calculates a target q-axis current I, which is a current command on two rotation axes (dq axes), from the motor speed calculated using at least the detected torque Td detected by the torque detector 2, the vehicle speed signal Sv acquired by an external device, and the electrical angle θ from the electrical angle calculation unit 14. q_t , target d-axis current I d_t Calculate.

[0023] The battery voltage detection unit 20 has a function of detecting the voltage of the battery 18 input to the motor 10 , and the detected battery voltage is input to the cutoff management unit 17 .

[0024] The battery voltage cut-off unit 19 has a function of cutting off the battery voltage applied to the motor drive device 7 in accordance with a battery voltage cut-off instruction INcv from the cut-off management unit 17.

[0025] The abnormal torque estimation unit 16 estimates the target q-axis current I q_t and the target d-axis current I d_t and the phase current I u , I v , I wand the electrical angle θ that is the output of the electrical angle calculation unit 14, and estimates abnormal torque of the motor 10. With this function, when a fault such as a short circuit or open circuit fault of a field effect transistor or a fault to power or ground of a gate drive signal occurs in the FET gate drive unit 6 and the motor drive device 7, the phase current flowing through each phase coil of the motor 10 becomes abnormal, affecting the output torque of the motor 10, and depending on the degree of the influence, abnormal phenomena such as vibration of the steering wheel 1 and generation of a steering force in the opposite steering direction to the steering direction of the driver (reverse assist) may occur. Below, the influence on the output torque of the motor 10 when a surface permanent magnet type three-phase brushless motor is used will be described.

[0026] Generally, for surface permanent magnet motors, the number of pole pairs P and the actual q-axis current I q_r Using the maximum value φ of the armature interlinkage magnetic flux by the permanent magnet, the output torque can be expressed by equation (1).

[0027]

number

[0028] From equation (1), the number of pole pairs P and the maximum value φ of the armature interlinkage magnetic flux by the permanent magnet are fixed values ​​depending on the motor used, so the factor that directly affects the fluctuation of the output torque value while the motor is rotating is the actual q-axis current I q_r It can be seen that.

[0029] Actual q-axis current I flowing through motor 10 q_r is the actual current I u_r , I v_r , I w_r is the q-axis current when the 3-phase to 2-phase conversion is performed. The target q-axis current I q_t When torque is generated in the motor 10 according to the q_r and the target q-axis current I q_tWhen a current deviation occurs, a torque value corresponding to the current deviation is superimposed on the output torque of the motor 10, generating abnormal torque in the motor 10, and the generated abnormal torque causes a change in the steering torque of the driver.

[0030] The abnormal torque estimation unit 16 estimates the target q-axis current I q_t and the target d-axis current I d_t The target current for each phase of the motor 10 is calculated based on the electrical angle θ output by the electrical angle calculation unit 14. u_t , I v_t , I w_t The detected phase current calculation unit 15 calculates the detected phase current of each phase as I u , I v , I w The abnormal torque is estimated based on the current deviation between the target current and the detected current of each phase. u , ΔI v , ΔI w Then, the following equations (2), (3), and (4) are established. u , I v , I w does not include detection error.

[0031]

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[0032]

number

[0033]

number

[0034] The following equation (5) is the conversion equation for three-phase to two-phase conversion.

[0035]

number

[0036] As described above, the d-axis current does not affect the output torque of the motor 10, and the q-axis current appears in the output torque of the motor 10. Therefore, the q-axis current related to the output torque of the motor 10 will be described below.

[0037] By substituting the above-mentioned equations (2) to (4) into equation (5) and expressing it separately into a term that includes the deviation of the q-axis current and a term that does not include the deviation, equation (6) is obtained.

[0038]

number

[0039] The first half of the above equation (6) is the target q-axis current I q_t The latter half represents the target q-axis current I q_t Therefore, the target q-axis current I q_t The deviation of the q-axis current calculated from the phase currents of the motor 10 calculated by the detected phase current calculation unit 15 is defined as ΔI q This results in the following equation (7).

[0040]

number

[0041] By combining the three sine functions in the above equation (7) and transforming them into one sine function, we obtain the following equation (8).

[0042]

number

[0043] From the above equation (8), the target q-axis current I q_tWhen a current deviation occurs between the target current for each phase of the motor 10 calculated based on the electrical angle θ output by the electrical angle calculation unit 14 and the detected current for each phase calculated by the detected phase current calculation unit 15, the actual q-axis current obtained by converting the current flowing through the motor 10 into a 3-phase to 2-phase current is calculated based on the target q-axis current I q_t For the maximum, ΔI q_amp That is, the target q-axis current I q_t With respect to the torque of the motor 10 output according to q_amp Therefore, there is a possibility that a torque equivalent to the above may be output as an abnormal torque.

[0044]

number

[0045] Next, the ΔI q_amp The possible range of current deviation ΔI u , ΔI v , ΔI w The minimum value of the current deviation minimum value ΔI min Then, ΔI min and ΔI u , ΔI v , ΔI w and the difference value between them is the current deviation difference value ΔI' u , ΔI' v , ΔI' w Then, the following equations (10), (11), and (12) hold.

[0046]

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[0047]

number

[0048]

number

[0049] In addition, the minimum current deviation ΔI min is the current deviation ΔI u , ΔI v , ΔI w Since this is the minimum value of ΔI min The difference value from is 0 (zero).

[0050] From the above-mentioned formulas (10) to (12) and formula (9), the above ΔI q_amp ΔI' u , ΔI' v , ΔI' w Using this, we obtain the following equation (13).

[0051]

number

[0052] Current deviation ΔI u , ΔI v , ΔI w , minimum current deviation ΔI min , current deviation difference value ΔI' u , ΔI' v , ΔI' w The maximum value of the current deviation difference ΔI max Here, the current deviation ΔI u , ΔI v , ΔI w The relationship between the values ​​of ΔI u ≦ΔI w ≦ΔI v Then, the following equations (14), (15), and (16) are obtained.

[0053]

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[0054]

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[0055]

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[0056] Substituting the above equations (14) and (15) into equation (13), ΔI Diff = ΔI max -ΔI min By converting the equation as above, we obtain the following equation (17).

[0057]

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[0058] In the above formula (17), the ΔI q_amp The condition for maximum is ΔI' w = 0 or ΔI' w = ΔI Diff When the ΔI q_amp is expressed by the following equation (18).

[0059]

number

[0060] In addition, the ΔI q_amp The condition for minimizing is ΔI' w = ΔI Diff / 2, and the ΔI q_amp is expressed by the following equation (19).

[0061]

number

[0062] From the above-mentioned formulas (18) and (19), the ΔI q_amp The possible range of the target q-axis current I q_t and the electrical angle θ output by the electrical angle calculation unit 14, and the current deviation ΔI between the target current for each phase of the motor 10 and the detected current for each phase calculated by the detected phase current calculation unit 15.u , ΔI v , ΔI w The minimum value of ΔI min and the maximum value ΔI max The difference between ΔI Diff Using this, it is expressed by the following equation (20).

[0063]

number

[0064] Therefore, the abnormal torque estimation unit 16 estimates the maximum value of the steering shaft converted abnormal torque (abnormal torque) T emu is expressed as the torque constant K m [Nm / A], motor reduction ratio G of gear 11 gear can be estimated from the following equation (21).

[0065]

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[0066] Torque constant K m [Nm / A], motor reduction ratio G of gear 11 gear Since is a constant, the output of the abnormal torque estimation unit 16 is set to the abnormal torque equivalent value ΔI Diff In the above explanation, ΔI' u Minimum value ΔI min However, ΔI' v is the minimum value ΔI min Even if ΔI' w is the minimum value ΔI min Even if this is the case, the possible range of the above-mentioned equation (20) does not change, and equation (21) does not change either.

[0067] An abnormality in the electric power steering device is defined by the amount of change in steering torque by the driver. A method for determining an abnormality in the electric power steering device based on the abnormal torque estimated by the abnormal torque estimation unit 16 will be described below.

[0068] First, the operation of the electric power steering device will be briefly described. When the driver steers the steering wheel 1, the wheels 12 are steered, and a road load torque that tries to return the wheels 12 to a neutral position is generated. When the motor 10 is not outputting a steering assist torque, this road load torque becomes the driver's steering torque. The driver's steering torque is detected by a torque detector 2, and the detected steering torque is input to a current command calculation unit 3, which calculates a target q-axis current I q_t , target d-axis current I d_t is output. Target q-axis current I q_t and the target d-axis current I d_t is input to the control calculation unit 4, and the control calculation unit 4 converts the phase current detected by the detected phase current calculation unit 15 into a q-axis current and a d-axis current, and calculates the target q-axis current I q_t and the target d-axis current I d_t The FET gate driver 6 and the motor driver 7 control the current flowing through the motor 10 so that it coincides with the q-axis component of the current flowing through the motor 10. The output torque of the motor 10 is converted via a gear 11 into a steering assist torque that assists the steering torque of the driver.

[0069] In order to simply explain the relationship between the driver's steering torque Th and the steering assist torque generated by the output of the torque detector 2, if a simple proportional gain is taken as the proportional relationship of G and the road load torque is taken as Ta, the following relational expression (22) is obtained.

[0070]

number

[0071] As a result of an abnormality occurring in the FET gate driver 6 and the motor driver 7, the target q-axis current I q_t The following describes the change in the steering torque of the driver when no current flows through the motor 10 as shown in FIG. q_t When the current does not flow to the motor 10 as shown in FIG. 1, the steering shaft converted torque of the output torque of the motor 10 is equal to the target q-axis current I q_tWhen the current flows to the motor 10 as shown in FIG. 1, a deviation of ΔT occurs with respect to the steering shaft converted torque. Due to this deviation, the driver's steering torque changes to Th'. The changed driver's steering torque is detected by the torque detector 2, and the detected steering torque is input to the current command calculation unit 3, which calculates the target q-axis current I q_t is calculated, and the target output torque of the motor 10 is GTh' in steering shaft conversion. Since the output torque of the motor 10 converted into the steering shaft due to an abnormality has a deviation of ΔT from the target output torque, the output torque of the motor 10 converted into the steering shaft is GTh'+ΔT. On the other hand, since the road load torque Ta does not change, the relational expression (23) below is obtained.

[0072]

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[0073] By substituting the above-mentioned equation (22) into the above-mentioned equation (23) so as to delete the road load torque Ta, and rearranging the equation, the following equation (24) is obtained.

[0074]

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[0075] The left side of the above equation (24) is the difference value when the driver's steering torque changes from a state of Th to Th' due to the occurrence of abnormal torque ΔT, converted into a steering shaft, in the motor 10. Therefore, it is possible to express it as the amount of change ΔTh in the driver's steering torque when abnormal torque ΔT, converted into a steering shaft, occurs in the motor 10, and this relational equation can be expressed by the following equation (25).

[0076]

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[0077] Using the above-mentioned equations (24) and (25), the relational expression between the steering shaft converted abnormal torque ΔT generated in the motor 10 and the driver's steering torque change amount ΔTh can be obtained from the following equation (26).

[0078]

number

[0079] On the other hand, as a result of an abnormality occurring in the FET gate driver 6 and the motor driver 7, the target q-axis current I q_t The abnormal torque converted into the steering shaft of the motor 10 that may occur when no current flows through the motor 10 as shown in equation (21). Therefore, the steering torque change amount ΔTh of the driver that may occur due to an abnormality is calculated by multiplying the abnormal torque T estimated by the abnormal torque estimation unit 16 by the following equation (21): emu Using this, it is given by the following equation (27).

[0080]

number

[0081] Therefore, the steering torque change amount of the driver that determines that the electric power steering device is abnormal is ΔTh th Then, the abnormal torque T estimated by the abnormal torque estimation unit 16 emu Therefore, an abnormality in the electric power steering device can be determined by the following equation (28).

[0082]

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[0083] T in the above equation (28) emu By substituting equation (21) into the equation (21) and transforming the equation, ΔI Diff Using this, the following equation (29) is obtained for determining whether the electric power steering device is abnormal.

[0084]

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[0085] According to the above equation (29), the steering torque change amount Δ Th th and maximum deviation ΔI Diff It is possible to show the relationship between the maximum difference in current deviation ΔI Diff By calculating and monitoring, it is possible to indirectly estimate abnormal torque.

[0086] 2 is a diagram showing an outline of the operation of the electric power steering device according to the first embodiment. The steering torque of the driver is acquired by the torque detector 2 shown in FIG. 1 in the steering torque detection process 201, and the current command calculation unit 3 calculates the target q-axis current I in the current command calculation process 301 based on the steering torque detected by the steering torque detection process 201 (the detected torque Td shown in FIG. 1) and the vehicle speed signal Sv shown in FIG. q_t and the target d-axis current I d_t The steering torque detection process 201 and the current command calculation process 301 are repeatedly executed at every period t0.

[0087] Based on the detection signal from the rotor rotation position detector 13, the electrical angle calculation unit 14 detects the electrical angle in electrical angle detection processing 1401. The detected phase current calculation unit 15 calculates the phase current of each phase in detected phase current detection processing 1501. The detected current 3-phase to 2-phase conversion processing 401 of the control calculation unit 4 converts the detected q-axis current I q_m and the detected d-axis current I d_m The target q-axis voltage / target d-axis voltage calculation process 402 calculates the target q-axis current I q_t and the detected q-axis current I q_m In order to match the target q-axis voltage, a process such as a PI feedback control is used to calculate the target d-axis current I d_t and the detected d-axis current I d_mA target d-axis voltage is calculated using a process such as PI feedback control so that the target q-axis voltage and the target d-axis voltage match. The target q-axis voltage and the target d-axis voltage are converted into three-phase voltages to be applied to the motor 10 in a target voltage two-phase to three-phase conversion 403, and a PWM signal is output to the FET gate drive cutoff unit 5 shown in Fig. 1 in a PWM output process 404. The electrical angle detection process 1401, the detected phase current detection process 1501, the detected current three-phase to two-phase conversion process 401, the target q-axis voltage / target d-axis voltage calculation process 402, the target voltage two-phase to three-phase conversion 403, and the PWM output process 404 are repeatedly executed at every cycle t1 which is shorter than the above-mentioned t0.

[0088] FIG. 3 shows the target q-axis current I q_t and the detected q-axis current I q_m As described above, the target q-axis current I q_t is updated every t0, and the detected q-axis current I q_m is the target q-axis current I q_t This shows that the voltage applied to the motor 10 is controlled every t1 so as to match the target q-axis current I q_t When the target q-axis current I q_t (n) and the detected q-axis current I q_m While a deviation occurs in (k), the target q-axis current I q_t (n-1) and the detected q-axis current I q_m The deviation of (k) becomes smaller. The target d-axis current I before t0 d_t (n-1) and the detected d-axis current I d_m The relationship of (k) can be considered in the same way, so the deviation can be considered to be minimal. q_t The detected phase current I u (k), I v (k), I w (k) is a process executed every period t1, in which the three-phase voltage V applied to the motor 10 is calculated using the electrical angle θ(k-1). u (k-1), V v (k-1), V w (k-1) is calculated, and the phase current is caused to flow by the three-phase voltage, so the target q-axis current I q_t (n-1), target d-axis current Id_t The target phase current I calculated using (n-1) and the electrical angle θ(k-1) t1 before u_t , I v_t , I w_t and the detected phase current I u (k), I v (k), I w The deviation of (k) can be considered to be small. Therefore, the abnormal torque estimation 1601 process in the abnormal torque estimation unit 16 is performed after the current command calculation process 301 is performed, and the target q-axis current I q_t (n-1), target d-axis current I d_t The target phase current I calculated using (n-1) and the electrical angle θ(k-1) t1 before u_t , I v_t , I w_t and the detected phase current I u (k), I v (k), I w It is best to run it with (k) as input.

[0089] An example of the abnormal torque estimation process 1601 will be described with reference to Fig. 4. As shown in the figure, a two-phase to three-phase conversion process 1602 and an abnormal torque estimated value calculation process 1603 are executed.

[0090] The 2-phase to 3-phase conversion process 1602 converts the electrical angle θ(k−1) of the electrical angle detection process 1401 and the target q-axis current I q_t (n-1) and the target d-axis current I d_t (n-1) is input and a 2-phase to 3-phase conversion is performed using the following equation (30), and the target U-phase current I u_t , target V-phase current I v_t , target W-phase current I w_t Output.

[0091]

number

[0092] The abnormal torque estimation value calculation process 1603 calculates the target U-phase current I u_t , target V-phase current I v_t , target W-phase current Iw_t and the U-phase detected current I u (k), V-phase detection current I v (k), W-phase detection current I w (k) The maximum current deviation difference ΔI Diff Calculate.

[0093] The abnormal torque estimation value calculation process 1603 will be described with reference to FIG. 5. In step S101 shown in FIG. 5, the current deviation (ΔI u , ΔI v , ΔI w The detailed processing of step S101 is composed of steps S201, S202, and S203 shown in FIG. 6, and the target U-phase current I u_t , target V-phase current I v_t , target W-phase current I w_t and the U-phase detection current I u (k), V-phase detection current I v (k), W-phase detection current I w (k) and each phase are subtracted individually to obtain the current deviation ΔI u , ΔI v , ΔI w Calculate.

[0094] In step S102 shown in Fig. 5, the minimum and maximum values ​​of the current deviations calculated for each phase are selected. The detailed process of selecting the minimum value in step S102 is as shown in Fig. 7. First, in step S301 in Fig. 7, the above-mentioned current deviation ΔI u In step S302, the minimum value of the current deviation and the above-mentioned current deviation ΔI v and the current deviation ΔI v If it is small, in step S303, the minimum value of the current deviation is set as the current deviation ΔI v In step 302, the current deviation ΔI v If it is larger, in step S304, the minimum value of the current deviation and the above-mentioned current deviation ΔI w Compare the current deviation ΔI wIf it is small, in step S305, the minimum value of the current deviation is set to the current deviation ΔI w In step S304, the current deviation ΔI w is larger, no processing is performed, and the minimum value of the current deviation is the current deviation ΔI u It will remain as it is.

[0095] 5. The detailed process of selecting the maximum value in step S102 in FIG. 5 is as shown in FIG. 8. First, in step S401 in FIG. 8, the above-mentioned current deviation ΔI u In step S402, the maximum current deviation and the above-mentioned current deviation ΔI v Compare the current deviation ΔI v If it is larger, in step S403, the maximum value of the current deviation is set to the current deviation ΔI v In step S402, the current deviation ΔI v If is small, in step S404, the maximum value of the current deviation and the above-mentioned current deviation ΔI w Compare the current deviation ΔI w If it is larger, in step S405, the maximum value of the current deviation is calculated as the current deviation ΔI w In step S404, the current deviation ΔI w If is small, no processing is performed, and the maximum value of the current deviation is the current deviation ΔI u It will remain as it is.

[0096] Next, in step S103 shown in FIG. 5, the maximum current deviation difference ΔI Diff Specifically, the minimum value of the current deviation calculated in step S102 is subtracted from the maximum value of the current deviation calculated in step S102 to calculate the maximum current deviation difference ΔI Diff Calculate.

[0097] The above explanation is based on the target q-axis current I q_t , target d-axis current I d_tOn the other hand, the q-axis current I q_m , detected d-axis current I d_m When the target q-axis current is updated by current control that feeds back the above, it is assumed that the detected current coincides with the target current before t0. However, since it is a feedback control, it is inevitable that deviations will occur between the target current and the detected current due to sudden changes in the target current or the effects of disturbances. Figure 9 shows an example of a time chart when such a case occurs. For example, at time point A, the detected current I q_m is the target q-axis current I before t0 q_t (n-1), and the target q-axis current I q_t (n-2) and the target q-axis current I before t0 q_t (n-1). The above explanation concerns the q-axis current, but the same can be applied to the d-axis current.

[0098] Furthermore, when the rotation speed of the motor 10 is high, the voltage applied to each phase of the motor 10 changes with the rotation, and therefore the current of each phase of the motor includes a response delay to the change in the voltage applied to each phase that accompanies the rotation of the motor 10. FIG. 10 shows an overview of an example of a time chart of the change in the electrical angle when the rotation speed of the motor 10 is high. For example, at time point A, the electrical angle is θ(k), and the target q-axis current I q_t , target d-axis current I d_t Even if the target phase current is calculated by performing a 2-phase to 3-phase conversion, it will not match the detected phase current. Therefore, it is considered appropriate to use the electrical angle θ(k-1) before t1, or θ(k-2) even before t1, as the electrical angle used for the 2-phase to 3-phase conversion.

[0099] From the above, it is preferable to calculate the target current for each phase by using the following combination of target current and electrical angle. Target q-axis current I q_t (n-1), target d-axis current I d_t (n-1) and electrical angle θ(k-1). Target q-axis current I q_t (n-2), target d-axis current I d_t(n-2) and electrical angle θ(k-1). Target q-axis current I q_t (n-1), target d-axis current I d_t A combination of (n-1) and electrical angle θ(k-2). Target q-axis current I q_t (n-2), target d-axis current I d_t (n-2) and electrical angle θ(k-2).

[0100] FIG. 11 shows an example of another embodiment of the abnormal torque estimation unit 16 based on the above. In FIG. 11, in the 2-phase to 3-phase conversion process 1606, the electrical angle θ(k-1), the electrical angle θ(k-2), the target q-axis current I q_t (n-1), target d-axis current I d_t (n-1), target q-axis current I q_t (n-2), target d-axis current I d_t (n-2) is input, and 2-phase to 3-phase conversion processing is performed for each of the four combinations of the target current and electrical angle described above, the maximum and minimum values ​​of the target current for each phase are calculated, and the target U-phase maximum current I u_t_Max , the target U-phase current minimum value I u_t_Min , maximum target V-phase current I v_t_Max , the target V-phase current minimum value I v_t_Min , maximum target W-phase current I w_t_Max , the target W-phase current minimum value I w_t_Min In the abnormal torque estimation value calculation process 1607, the target U-phase current maximum value I u_t_Max , the target U-phase current minimum value I u_t_Min , maximum target V-phase current I v_t_Max , the target V-phase current minimum value I v_t_Min , maximum target W-phase current I w_t_Max , the target W-phase current minimum value I w_t_Min and the U-phase detection current I u (k), V-phase detection current I v (k), W-phase detection current I w From (k), after a predetermined process, ΔI Diff Output.

[0101] Next, the abnormal torque estimated value calculation process 1607 in Fig. 11 will be described. The basic flow of the processing contents in the abnormal torque estimated value calculation process 1607 is as shown in Figs. 5 and 6, similarly to the embodiment in Fig. 4. First, in step S101, a current deviation (ΔI u , ΔI v , ΔI w ) is calculated. FIG. 12 shows a flow of the detailed processing contents of FIG. 6. The processing is common to the U phase, V phase, and W phase, and is performed in the order of the U phase, V phase, and W phase, and the current deviation ΔI u , current deviation ΔI v , current deviation ΔI w First, in step S501, the detected X-phase current I x and the target X-phase maximum current I x_t_Max Detected X-phase current I x The target X-phase current maximum value I x_t_Max If it is greater than , the current deviation ΔI x is the detected X-phase current I x to the target X-phase maximum current I x_t_Max The value is the subtraction value.

[0102] In step S501, the detected X-phase current Ix is set to a maximum value I x_t_Max If it is smaller than the detected X-phase current I x and the target X-phase current minimum value I x_t_Min Detect the X-phase current I x The target X-phase current minimum value I x_t_Min If it is smaller than , in step S504, the current deviation ΔI x is the detected X-phase current I x to the target X-phase current minimum value I x_t_Min The detected X-phase current I x The target X-phase current minimum value I x_t_Min If it is greater than , in step S505, the current deviation ΔI x is 0. Note that the detected X-phase current I x , maximum target X-phase current I x_t_Max , the target X-phase current minimum value I x_t_Min and current deviation ΔI xIn the above, X indicates U, V, or W, and x indicates u, v, or w.

[0103] Next, the minimum and maximum values ​​of the current deviation are selected in step S102 shown in Fig. 5. The detailed process of the minimum value selection in step S102 in Fig. 5 is as shown in Fig. 7, similar to the embodiment in Fig. 3. First, in step S301 shown in Fig. 7, the minimum value of the current deviation is set to the current deviation ΔI u In step S302, the minimum value of the current deviation and the current deviation ΔI v and the current deviation ΔI v If it is small, in step S303, the minimum value of the current deviation ΔI v In step S302, the current deviation ΔI v If it is larger, in step S304, the minimum value of the current deviation and the current deviation ΔI w Compare the current deviation ΔI w If it is small, in step S305, the minimum value of the current deviation is set to the current deviation ΔI w In step S304, the current deviation ΔI w If is large, no processing is performed, and the minimum value of the current deviation is the current deviation ΔI u It will remain as it is.

[0104] The detailed process of selecting the maximum value in step S102 in FIG. 5 is the same as that in the embodiment in FIG. 3. As shown in FIG. 8, first, in step S401 shown in FIG. 8, the maximum value of the current deviation is set to the current deviation ΔI u In step S402, the maximum current deviation and the current deviation ΔI v Compare the current deviation ΔI v If it is larger, in step S403, the maximum value of the current deviation is set to the current deviation ΔI v In step S402, the current deviation ΔI v If is small, in step S404, the maximum value of the current deviation and the current deviation ΔI w Compare the current deviation ΔIw If it is larger, in step S405, the maximum value of the current deviation is calculated as the current deviation ΔI w In step S404, the current deviation ΔI w If is small, no processing is performed, and the maximum value of the current deviation is the current deviation ΔI u It will remain as it is.

[0105] Next, the maximum current deviation difference ΔI Diff Specifically, similarly to the embodiment of FIG. 3, the minimum value of the current deviation is subtracted from the maximum value of the current deviation calculated in step S102 to calculate the maximum current deviation difference ΔI Diff Calculate.

[0106] From the above, the abnormal torque estimation value Tae, which is the output signal of the abnormal torque estimation unit 16 in FIG. 1, that is, the maximum current deviation difference ΔI Diff is calculated.

[0107] Next, the process of the cutoff management unit 17 in Fig. 1 will be described. The cutoff management unit 17 calculates the maximum current deviation difference ΔI Diff , the battery voltage Vba detected by the battery voltage detection unit 20, and the motor rotation speed calculated from the electrical angle θ detected by the electrical angle calculation unit 14, to determine whether the motor 10 should be in a motor drive state or a motor drive stop state, and only when it is determined that the motor 10 should be in a drive stop state, the control calculation unit 4 is provided with a function of transmitting a PWM signal forced off instruction INoff to the control calculation unit 4, a FET gate drive cutoff instruction INcg to the FET gate drive cutoff unit 5, and a battery voltage cutoff instruction INcv to the battery voltage cutoff unit 19.

[0108] FIG. 13 shows a process flow of the shutdown management unit 17. First, in step S601, it is determined whether the motor rotation speed calculated from the electrical angle θ obtained by the electrical angle calculation unit 14 is equal to or lower than a preset rotation speed threshold value.

[0109] In a surface permanent magnet motor, an induced voltage proportional to the motor rotation speed is generated. The current that can be passed through the motor 10 is limited by the voltage difference between the induced voltage caused by the motor rotation and the battery voltage. Due to this phenomenon, the line current flowing through the motor is reduced compared to the indicated current calculated from the detected torque detected by the torque detector 2, and the detected current I u , I v , I w is the expected target phase current I u_t , I v_t , I w_t The current deviation is the maximum current deviation difference ΔI Diff If the value of the motor speed exceeds the preset threshold, there is a risk of erroneous determination. For this reason, step S601 is set as a monitoring condition in the process flow of Fig. 13, which is a monitoring condition for the motor speed. If the motor speed exceeds a preset threshold, the driving of the motor 10 is not stopped.

[0110] The rotation speed threshold, which is a monitoring condition for the motor rotation speed, is made variable according to the battery voltage Vba detected by the battery voltage detection unit 20. For example, the rotation speed at which voltage saturation is reached for each battery voltage is prepared in advance as a map, and the battery voltage Vba detected at a certain regular interval is compared with the map to determine the rotation speed threshold. Also, taking into account the operable voltage of the system, a fixed rotation speed value that does not induce erroneous judgment may be used as the rotation speed threshold instead of varying the rotation speed threshold according to the battery voltage Vba.

[0111] In step S601 of FIG. 13, if the motor rotation speed is equal to or lower than the rotation speed threshold, in step S602, the maximum current deviation difference ΔI Diff The threshold is the right side of the above equation (28), which is the torque constant (torque-current conversion coefficient) K m [Nm / A], motor reduction ratio Ggear, output gain G of motor 10 with respect to detected torque, and a change amount Δ of steering torque set in advance according to safety requirements or safety goals. Th th The value is calculated using

[0112] In step S602, the maximum current deviation difference ΔI Diff If it is equal to or greater than the threshold, the abnormality counter is incremented in step S603, and the holding counter is cleared in step S604.

[0113] In step S602, the maximum current deviation difference ΔI Diff If it is less than the threshold, in step S609, it is confirmed that the holding counter is equal to or less than the holding counter threshold. The abnormality counter threshold and the holding counter threshold may be set to appropriate values ​​according to the system to be applied.

[0114] If the result of the check in step S609 is YES (the hold counter value is less than or equal to the hold counter threshold), the hold counter is incremented in step S610, and if the result of step S609 is NO (the hold counter value exceeds the hold counter threshold), the abnormality counter is cleared in step S611.

[0115] If the motor rotation speed exceeds the rotation speed threshold in step S601, then in step S612 it is confirmed that the hold counter value is equal to or less than the hold counter threshold, and if the confirmation result is YES (the hold counter value is equal to or less than the hold counter threshold), then in step S613 the hold counter is incremented.

[0116] If the result of step S612 is NO (the hold counter value exceeds the hold counter threshold), the abnormality counter is cleared in step S614.

[0117] Next, in step S605, it is confirmed whether the abnormal counter value is equal to or greater than the abnormal counter threshold, and if the confirmation result is YES (the abnormal counter value is equal to or greater than the abnormal counter threshold), a transition to a motor drive stop state is made, and in step S606, a PWM signal forced off instruction INoff is sent to the control calculation unit 4, and in step S607, a FET gate drive cutoff instruction INcg is sent to the FET gate drive cutoff unit 5, and a motor current cutoff instruction INci is sent to the motor current cutoff unit 9. In addition, a battery voltage cutoff instruction INcv is sent to the battery voltage cutoff unit 19 (step S608).

[0118] By the processes of steps S605, S606 and S607, the command current to the motor 10 is cut off, so that the motor 10 is brought into a motor drive stop state, and the electric power steering device is brought into an assist stop state.

[0119] If the check result in step S605 is NO (the abnormal count value is less than the abnormal count threshold value), it is determined that no abnormal torque is occurring, and the motor 10 does not enter a motor drive stop state, but maintains the current state.

[0120] Embodiment 2 FIG. 15 is an overall configuration diagram showing one example of an electric power steering device according to embodiment 2. In FIG. 15, a detected phase current abnormality detection unit 21 and an open fault determination unit 22 are added to the overall configuration diagram showing one example of an electric power steering device according to embodiment 1 of FIG. 1, and the processing content of the interruption management unit 17 is changed, thereby electric field and when an open circuit fault in the FET constituting the drive device of the motor drive device 7 or a disconnection fault in the motor line of the motor 10 is detected, openIf the fault involves at least one phase, the motor drive continues with the other phases other than the faulty phase, and if the fault is other than an open fault in the FET constituting the drive device of the motor drive device 7 or other than a disconnection fault in the motor line of the motor 10, or if the fault involves two or more phases, the motor drive is stopped. In the following explanation, these FETs may be referred to as "drive elements".

[0121] Detection of an open fault in the FET of the motor drive device 7 or a broken motor line of the motor 10 is performed by the open fault judgment unit 22 when the abnormal torque estimation value Tae, which is the output of the abnormal torque estimation unit 16, is an abnormal value and a signal Sac indicating an abnormal state of the detected current is output from the detected phase current abnormality detection unit 21.

[0122] Here, the behavior of the motor drive device 7 when an open fault occurs in the U-phase FET will be described. First, the behavior of each phase current immediately after an open fault occurs in the U-phase FET will be described, with the motor 10 being a simple resistor model. This behavior is the behavior before the three-phase applied voltages are changed by the current feedback control in the control calculation unit 4. Note that although the description is given using an open fault occurrence in the U phase as an example, the same changes will occur in the case of an open fault occurrence in the V and W phases, except that the target phases change.

[0123] Figure 21 shows the resistor model under normal conditions. u , I v , I w is the phase voltage V u , V v、 V w Using the resistance R, these can be expressed by the following equations (31), (32), and (33).

[0124]

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[0125]

number

[0126]

number

[0127] FIG. 22 shows a simple resistor model of the motor 10 when an open fault occurs in the U-phase FET. The current in each phase during this open fault is expressed as I' u , I' v , I' w Then, these can be expressed by the following equations (34), (35), and (36).

[0128]

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[0129]

number

[0130]

number

[0131] According to equations (31) to (36), the V-phase current I' when an open fault occurs in the U-phase FET is V and W-phase current I' W is the normal phase current I U , I V , I W Using this, we obtain the following equations (37) and (38).

[0132]

number

[0133]

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[0134] According to equations (37) and (38), immediately after an open fault occurs in a FET of one phase, the current flowing through the phase in which the open fault occurred is distributed equally to the other phases, and the currents in phases that do not have an open fault have the same absolute value but opposite signs (reverse directions).

[0135] Next, the behavior of the abnormal torque estimation unit 16 when an open circuit fault occurs in the U-phase FET will be described below. u_t , I v_t , I w_t When the phase current is correctly controlled to the target current, the phase current I' u , I' v , I' w can be expressed by the above equation (34) and the following equations (39) and (40), respectively.

[0136]

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[0137]

number

[0138] Here, the U-phase current I' is added to the notation of the above equations (2) to (4). u Converting the above equations (39) and (40), the current deviation ΔI u , ΔI v , ΔI w This is expressed as the following equations (41) to (43).

[0139]

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[0140]

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[0141]

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[0142] From the above equations (41) to (43), the minimum current deviation ΔI min = ΔI u =-I u_t and 、 Maximum current deviation ΔI max = ΔI v = ΔI w =1 / 2I u_t Therefore, the maximum current deviation difference ΔI Diff can be expressed by the following equation (44).

[0143]

number

[0144] Maximum current deviation difference ΔI when U-phase open fault occurs Diff In other words, the estimated abnormal torque can be expressed by the above equation (44). When a U-phase open circuit fault occurs, the target U-phase current I u_t The abnormal torque estimation value changes due to the factor. The preset threshold for determining the occurrence of abnormal torque is set as ΔI Diff_th Then, the target U-phase current I at which abnormal torque is determined to occur when an open fault occurs in the U-phase FET is u_t can be expressed by the following equation (45), and when equation (45) is satisfied, it can be determined that the abnormal torque estimation value Tae is abnormal.

[0145]

number

[0146] Next, the behavior of each phase current in the abnormal torque estimation unit 16 when a U-phase open fault occurs and the open fault determination process will be described. When a U-phase open fault occurs and the condition of equation (45) is satisfied, the electrical angle is θ, and the amplitude of the target current is I pk Then, the target current for each phase I u_t , I v_t , I w_t can be expressed by the following equations (46) to (48).

[0147]

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[0148]

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[0149]

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[0150] The amplitude of the target current at this time is I pk can be expressed by the following equation (49) using equations (45) and (46).

[0151]

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[0152] From equation (49) and equations (46) to (48), the target current I u_t , I v_t , I w_t can be expressed by the following equations (50) to (52).

[0153]

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[0154]

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[0155]

number

[0156] The schematic diagram of the target current of each phase at this time is shown in FIG. 23. The U-phase current I′ flowing through the motor 10 is u is 0, V phase current I' v , W phase current I' wcan be expressed by the following equations (53) and (54) using the above-mentioned equations (39), (40), and (50) to (52).

[0157]

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[0158]

number

[0159] FIG. 24 is a schematic diagram of the phase currents flowing through each phase of the motor at this time. When the U phase current = 0, the V phase current takes the value shown in equation (53), and the W phase current takes the value shown in equation (54). When the electrical angles of 90 deg, 270 deg (not shown, the same applies below) and their surroundings are detected, the U phase current = V phase current = W phase current = approximately 0 A, and in this case, it is difficult to determine whether the open fault has occurred based on the magnitude relationship of the absolute values ​​of the detected phase currents. For this reason, the magnitude relationship of the absolute values ​​of the applied voltages of each phase is used to make the determination. The absolute value of the U phase applied voltage |V when the electrical angles of 90 deg, 270 deg, and their surroundings are detected u | is the absolute value of the V phase applied voltage |V v | and W Absolute value of phase applied voltage |V w Therefore, if the U-phase current is close to 0 A and the following logical formula (55) using the absolute values ​​of the voltages applied to each phase is satisfied, it can be determined that an open fault has occurred in the U-phase FET. Note that the determination of whether the U-phase current is close to 0 A is made based on whether it is equal to or lower than a predetermined threshold value that is set in advance according to the system to which the current is applied.

[0160]

number

[0161] When the electrical angle is other than 90 deg, 270 deg, or the vicinity thereof, if the V-phase current and W-phase current are not close to 0 A even when an open fault occurs in the U-phase FET, and the magnitude relationship of each phase current satisfies the following logical formula (56), it is possible to determine that an open fault has occurred in the U-phase FET. Note that the determination that the V-phase current and W-phase current are not close to 0 A is performed using a preset method that is set according to the system to which the circuit is applied. Greater than a given value It is decided.

[0162]

number

[0163] By combining the logical expressions (55) and (56), it becomes possible to determine an open fault at all electrical angles when an open fault occurs in the U-phase FET. The combined logical expression is given by the following expression (57).

[0164]

number

[0165] In addition, the sum of the phase currents detected and calculated by detected phase current calculation unit 15 is theoretically 0 during normal motor driving. However, when an abnormality such as an abnormality in detected phase current calculation unit 15, failure of shunt resistors 8u, 8v, 8w, or short-circuit failure of a drive element of motor drive device 7 occurs, the sum of the phase currents does not become 0. In the case of an open circuit fault in one phase of the drive element of the motor drive device 7, the current flowing through the phase in which the open circuit fault has occurred is distributed equally to the other phases according to equations (37) and (38), and the sum of the phase currents is zero. Therefore, by adding a condition for the sum of the phase currents to equation (57), it is possible to separate the open circuit fault in one phase of the drive element of the motor drive device 7 from an abnormality in the detected phase current calculation unit 15, faults in the shunt resistors 8u, 8v, and 8w, and short-circuit faults in the drive elements of the motor drive device 7. Whether the sum of the phase currents is zero is determined to be equal to or greater than a predetermined threshold value set in advance according to the system to be applied, and the determination condition is given by the following equation (58).

[0166]

number

[0167] As described above, when abnormal torque is generated by the abnormal torque estimation unit 16, it is possible to determine an open fault phase when the logical product of the equations (57) and (58) is satisfied. Using these, the processing contents of the detected phase current abnormality detection unit 21 and the open fault determination unit 22 will be explained.

[0168] Although an example of an open-circuit fault in the U-phase FET has been shown, the faulty phase determination condition in the event of an open-circuit fault in the V-phase FET is the logical product of the following equation (59) and the above equation (58), and the faulty phase determination condition in the event of an open-circuit fault in the W-phase FET is the logical product of the following equation (60) and the above equation (58).

[0169]

number

[0170]

number

[0171] The detected phase current anomaly detector 21 in FIG. 15 detects the U-phase detected phase current, which is the output of the detected phase current calculator 15 in FIG. phase current I u , V phase detection phase current I v , W phase detection phase current I w The function to judge whether the U phase detection is normal is implemented by the judgment of the formula (58). phase current I u , V phase detection phase current I v , W phase detection phase current I w The absolute value of the sum of the two is used, and the absolute value of the sum is a predetermined threshold value. less thanIf the difference is equal to or greater than the threshold, it is determined to be normal, and if the difference is greater than or equal to the threshold, it is determined to be abnormal, and the result of the determination, that is, the detected current abnormal state, is output. Note that the predetermined threshold is set to an appropriate value depending on the system to be applied.

[0172] The processing contents in the open circuit failure determination unit 22 will be described with reference to Fig. 16. The processing in the open circuit failure determination unit 22, which is the flow in Fig. 16, is periodic processing that is performed at a predetermined period, and is performed at an appropriate period according to the applicable system.

[0173] In step S701 shown in FIG. 16, the abnormal torque estimation value Tae, which is the output calculated by the abnormal torque estimation unit 16, that is, the maximum current deviation difference ΔI Diff is equal to or greater than a predetermined threshold value, and whether the detected current is in an abnormal state (whether a signal Sac indicating an abnormal state of the detected current is output from the detected phase current abnormality detector 21). Diff is equal to or greater than the predetermined threshold, a signal Sac is output indicating that the detected current state is abnormal, and the motor rotation speed is equal to or less than the predetermined rotation speed threshold, the process of determining an open-phase fault in step S702 is performed. Note that the process contents in the abnormal torque estimation unit 16 are the same as those in the first embodiment, and therefore will not be described here. Diff The threshold value to be compared with is the right side of the above equation (28), and is the torque constant (torque-current conversion coefficient) K m [Nm / A], motor reduction ratio Ggear, output gain G of motor 10 with respect to detected torque, and a change amount Δ of steering torque set in advance according to safety requirements or safety goals. Th th The value is calculated using

[0174] The determination of whether the detected current is in an abnormal state in step S701 is made based on the determination condition of equation (58). This is used to determine whether an open circuit fault in one phase of the drive element of the motor drive device 7 is present, an abnormality in the detected phase current calculation unit 15, a fault in the shunt resistors 8u, 8v, and 8w, or a short circuit fault in the drive element of the motor drive device 7 is present.

[0175] If the determination in step S701 is YES, each phase open fault judgment process in step S702 is performed. The each phase open fault judgment process in step S702 performs the U phase open fault judgment process in FIG. 17, the V phase open fault judgment process in FIG. 18, and the W phase open fault judgment process in FIG. 19. These processes are periodic processes performed in the same period, and operate in parallel. Note that the U phase open fault judgment process, the V phase open fault judgment process, and the W phase open fault judgment process may be performed in a predetermined order. That is, the open fault judgment process is executed for the selected phase. Also, if the determination in step S701 is NO, the process in FIG. 16 is terminated.

[0176] First, the U-phase open circuit fault determination process in Fig. 17 will be described. In step S801, the U-phase detected phase current I U_OFF , V phase detected phase current I V_OFF , W phase detected phase current I W_OFF Check that the U-phase detected phase current I is within a predetermined normal range. U_OFF , V phase detected phase current I V_OFF , W phase detected phase current I W_OFF If the state where the U-phase detected phase current I is within the predetermined normal range continues for a predetermined time, the determination result is YES, and the next step S802 is performed. U_OFF , V phase detected phase current I V_OFF , W phase detected phase current I W_OFF If the state where the voltage Vout falls within the predetermined normal range does not continue for a predetermined time, the determination result is NO, and the U-phase open fault determination process of FIG. 17 is terminated.

[0177] The determination process in step S801 is used to determine whether a short-circuit failure has occurred in the lower arm drive element of the motor drive device 7. In this embodiment, a lower arm shunt is used in which shunt resistors 8u, 8v, and 8w are connected between the lower arm drive element of each phase and the ground. Under normal circumstances, the detected phase current detected and calculated by the detected phase current calculation unit 15 when the lower arm drive element is in the off state is close to 0 A. However, when the lower arm drive element has a short-circuit failure, the lower arm drive element is always in the on state, and the voltage (power supply voltage) of the battery 18 applied to the motor drive device 7 is in a state in which the ground is short-circuited when the upper arm drive element is on. As a result, the detected phase current is not close to 0 A, and a short-circuit current flows. In order to perform the above-mentioned determination, each phase current when the lower arm drive element is off is used, instead of the detected phase current when the lower arm drive element is on, which is used during normal motor control.

[0178] Next, in step S802, the U-phase detected phase current I U of Absolute value |I U | is a given threshold below As shown in equation (34), when the U-phase driving element has an open circuit fault, the U-phase detected phase current I U The detected phase current I of the U phase is close to 0 A. The predetermined threshold value used to determine whether the phase current I is close to 0 A is set appropriately depending on the system to which it is applied. U Absolute value of |I U | is a given threshold below If so, the determination result is YES, and the next step S803 is executed. U Absolute value of |I U | is a given threshold Greater than In this case, the determination result is set to NO, and the U-phase open fault determination process in FIG. 17 is terminated.

[0179] Next, in step S803, it is determined whether the U phase has an open circuit fault, and the U phase target voltage V U Absolute value of |V U | and V-phase target voltage V V Absolute value of |V V| and W phase target voltage V W Absolute value of |V W | and V phase detection phase current Absolute value of |I V | and W phase detection phase current Absolute value of |I W The determination process of the above-mentioned equation (57) is performed using | and U Absolute value of |V U | is the V-phase target voltage V V Absolute value of |V V | Bigger , and U phase target voltage V U Absolute value of |V U | W Phase Target Voltage V W Absolute value of | V W | If greater than , or V phase detection phase current Absolute value of |I V | and W phase detection phase current Absolute value of |I W | is a given threshold Greater than In this case, it is determined that the U phase has an open circuit fault, the determination result is YES, and step S804 is executed. In step S803, if the determination result is not YES, that is, U phase target voltage V U Absolute value of |V U | is the V-phase target voltage V V Absolute value of |V V | or less, or U phase target voltage V U Absolute value of |V U | is the W phase target voltage V W Absolute value of |V W If it is less than or equal to V phase detection phase current Absolute value of |I V | and W phase detection phase current Absolute value of |I W If either or both of | are equal to or less than the predetermined threshold, it is determined that the U phase does not have an open circuit fault, the determination result is NO, and the U phase open circuit fault determination process of FIG. 17 is terminated. phase current Absolute value of |I V | and W phase detection phase current Absolute value of |I W The predetermined threshold used for the judgment of | is set appropriately depending on the system to be applied.

[0180] Next, in step S804, the U-phase open fault counter is incremented. The U-phase open fault counter is incremented when it is determined in step S803 that the U-phase has an open fault, and holds and accumulates a count value from the start of the increment operation until a preset predetermined cumulative time. In addition, the counter is cleared to zero after the predetermined cumulative time has elapsed from the start of the increment operation. This is provided to prevent malfunctions in the determinations of steps S802 and S803 due to disturbances, etc., and depending on the system to which it is applied, it may be a counter that only performs normal increment operations. In that case, it is sufficient to use a determination condition in step S805 that excludes the conditions within the predetermined cumulative time. In addition, the predetermined cumulative time is set to an appropriate value depending on the system to which it is applied.

[0181] Next, in step S805, it is confirmed whether the U-phase open fault counter has reached a predetermined count value within a predetermined integration time, which is set to an appropriate value depending on the system to be applied. If the U-phase open fault counter has reached a predetermined count value within a predetermined integration time, it is determined that the U-phase open fault is confirmed, the determination result is YES, and the next step S806 is executed. If the U-phase open fault counter has not reached a predetermined count value within a predetermined integration time, it is determined that the U-phase open fault is not confirmed, the determination result is NO, and the U-phase open fault determination process in FIG. 17 is terminated.

[0182] Next, in step S806, a U-phase fault determination flag that is turned on when an open fault in the U-phase is determined is turned on, and the U-phase open fault determination process is terminated. The above is the processing content of the U-phase open fault determination process in FIG.

[0183] Next, the V-phase open circuit fault determination process of Fig. 18 will be described. The U-phase open circuit fault determination process is replaced with the V-phase process, and the determination conditions for each step are different, but the basic operations are the same. In step S901, the gate drive signals output from the FET gate drive unit 6 for the lower arm drive elements QLu, QLv, and QLw are Off command The U-phase detection phase current I U_OFF , V phase detected phase current I V_OFF , W phase detected phase current I W_OFF Check that the U-phase detected phase current I is within the specified normal range. U_OFF , V phase detected phase current I V_OFF , W phase detected phase current I W_OFF If the state where the U-phase detected phase current I is within the predetermined normal range continues for a predetermined time, the determination result is YES, and the next step S902 is performed. U_OFF , V phase detected phase current I V_OFF , W phase detected phase current I W_OFF If the state where the V-phase open fault determination process in FIG. 18 does not continue for a predetermined time period within the predetermined normal range, the determination result is NO, and the V-phase open fault determination process in FIG. 18 is terminated.

[0184] The determination process in step S901 is used to determine whether a short-circuit failure has occurred in the lower arm drive element of the motor drive device 7. In this embodiment, a lower arm shunt is used in which shunt resistors 8u, 8v, and 8w are connected between the lower arm drive element of each phase and the ground. Under normal circumstances, the detected phase current detected and calculated by the detected phase current calculation unit 15 when the lower arm drive element is in the off state is close to 0 A. However, when the lower arm drive element has a short-circuit failure, the lower arm drive element is always in the on state, and the voltage (power supply voltage) of the battery 18 applied to the motor drive device 7 is in a state in which the ground is short-circuited when the upper arm drive element is on. As a result, the detected phase current is not close to 0 A, and a short-circuit current flows. In order to perform the above-mentioned determination, the phase current when the lower arm drive element is off is used instead of the detected phase current when the lower arm drive element is on, which is used during normal motor control.

[0185] Next, in step S902, the V-phase detected phase current I V of Absolute value |I V | is a given threshold below As shown in equation (34), when the U-phase driving element has an open circuit fault, the U-phase detected phase current I U is close to 0A, but if the V-phase drive element has an open circuit fault, the V-phase detected phase current I V The V-phase detected phase current I V Absolute value of |I V | is a given threshold below If so, the determination result is YES, and the next step S903 is executed. V Phase detection phase current I V Absolute value of |I V | is a given threshold Greater than In this case, the determination result is set to NO, and the V-phase open fault determination process in FIG. 18 is terminated.

[0186] Next, in step S903, it is determined whether the V phase has an open circuit fault, and the V phase target voltage V V Absolute value of |V V |And, U Phase target voltage V U Absolute value of |V U | and W phase target voltage V W Absolute value of |V W | and U phase detection phase current Absolute value of |I U | and W phase detection phase current Absolute value of |I W The determination process of the above equation (59) is performed using | and V Absolute value of |V V | is the U-phase target voltage V U Absolute value of |V U | Bigger , and the V-phase target voltage V V Absolute value of |V V | is the W phase target voltage V W Absolute value of |V W| If greater than , or U phase detection phase Absolute value of current |I U | and W Phase Detection phase current Absolute value of |I W | is a given threshold Greater than case, V The phase is judged to have an open fault, the result is YES, Step S904 The following will be implemented. In step S903, if the determination result is not YES, that is, V-phase target voltage V V Absolute value of |V V | is the U-phase target voltage V U Absolute value of |V U | or less, or V phase target voltage V V Absolute value of |V V | is the W phase target voltage V W Absolute value of |V W If it is less than or equal to, or U phase is detected phase current Absolute value of |I U | and W phase detection phase current Absolute value of |I W If either or both of | are equal to or less than the predetermined threshold, it is determined that the V phase does not have an open circuit fault, the determination result is NO, and the V phase open circuit fault determination process of FIG. 18 is terminated. phase current Absolute value of |I U | and W Phase Detection phase current Absolute value of |I W The predetermined threshold used for the judgment of | is set appropriately depending on the system to be applied.

[0187] Next, in step S904, the V-phase open fault counter is incremented. The V-phase open circuit fault counter is incremented when it is determined in step S903 that the V-phase has an open circuit fault, and holds and accumulates a count value from the start of the increment operation until a preset predetermined cumulative time. In addition, the counter is cleared to zero after the predetermined cumulative time has elapsed from the start of the increment operation. This is provided to prevent malfunctions in the determinations of steps S902 and S903 due to disturbances, etc., and depending on the system to which the counter is applied, the counter may only perform normal increment operations. In that case, a condition within the predetermined cumulative time of the determination conditions of step S905 may be excluded. In addition, the aforementioned predetermined cumulative time is set to an appropriate value depending on the system to which the counter is applied.

[0188] Next, in step S905, it is confirmed whether the V-phase open fault counter has reached a predetermined count value within a predetermined integration time. Note that the predetermined count value is set to an appropriate value depending on the system to be applied. If the V-phase open fault counter has reached a predetermined count value within a predetermined integration time, it is determined that the V-phase open fault is confirmed, the determination result is YES, and the next step S906 is executed. If the V-phase open fault counter has not reached a predetermined count value within a predetermined integration time, it is determined that the V-phase open fault is not confirmed, the determination result is NO, and the V-phase open fault determination process in FIG. 18 is terminated.

[0189] Next, in step S906, a V-phase fault determination flag that is turned on when an open fault in the V-phase is determined is turned on, V The phase open fault determination process is completed. V This is the processing content of the phase open fault determination process.

[0190] Next, the contents of the W-phase open fault determination process in Fig. 19 will be described. The above-mentioned U-phase open fault determination process and V-phase open fault determination process are replaced with the W-phase, and although the determination conditions for each step are different, the basic operations are the same. In step S1001, the U-phase detected phase current I U_OFF , V phase detected phase current I V_OFF , W phase detected phase current I W_OFF Check that the U-phase detected phase current I is within the specified normal range for a specified period of time. U_OFF , V phase detected phase current I V_OFF , W phase detected phase current I W_OFF If the state where the U-phase detected phase current I is within the predetermined normal range continues for a predetermined time, the determination result is YES, and the next step S1002 is performed. U_OFF , V phase detected phase current I V_OFF , W phase detected phase current I W_OFF If the state where the value of the W-phase open fault determination process in FIG. 19 does not continue within the predetermined normal range for the predetermined time, the determination result is NO, and the W-phase open fault determination process in FIG. 19 is terminated.

[0191] The determination process in step S1001 is used to determine whether a short-circuit failure has occurred in the lower arm drive element of the motor drive device 7. In this embodiment, a lower arm shunt is used in which the shunt resistors 8u, 8v, and 8w are connected between the lower arm drive element of each phase and the ground. Under normal circumstances, the detected phase current detected and calculated by the detected phase current calculation unit 15 when the lower arm drive element is in the off state is close to 0 A. However, when the lower arm drive element has a short-circuit failure, the lower arm drive element is always in the on state, and the voltage (power supply voltage) of the battery 18 applied to the motor drive device 7 is in a state in which the ground is short-circuited when the upper arm drive element is on. As a result, the detected phase current is not close to 0 A, and a short-circuit current flows. In order to perform the above-mentioned determination, each phase current when the lower arm drive element is off is used, instead of the detected phase current when the lower arm drive element is on, which is used during normal motor control.

[0192] Next, in step S1002, the W-phase detected phase current I W of Absolute value |I W | is a given threshold below As shown in equation (34), when the U-phase driving element has an open circuit fault, the U-phase detected phase current I U is close to 0A, but if the W-phase drive element has an open circuit fault, the W-phase detection phase current I W The W-phase detected phase current I W Absolute value of |I W | is a given threshold below If so, the determination result is YES, and the next step S1003 is executed. W Absolute value of |I W | is a given threshold Greater than In this case, the determination result is set to NO, and the W-phase open fault determination process in FIG. 19 is terminated.

[0193] Next, in step S1003, it is determined whether the W phase has an open circuit fault, and the W phase target voltage V W Absolute value of |V W | and V-phase target voltage V V Absolute value of |V V | and U phase target voltage V U Absolute value of |V U | and U phase detection phase current Absolute value of |I U | and V phase detection phase current Absolute value of |I V The determination process of the above-mentioned equation (60) is performed using | and W Absolute value of |V W | is the U-phase target voltage V U Absolute value of |V U | Bigger , and the W-phase target voltage V W Absolute value of |V W | is the V-phase target voltage V V Absolute value of |V V | If greater than, or U phase detection phase current Absolute value of |I U | and V phase detection phase current Absolute value of |I V | is a given threshold Greater than In this case, it is determined that the W-phase has an open circuit fault, the determination result is YES, and step S1004 is executed. In step S1003, if the determination result is not YES, that is, W phase target voltage V W Absolute value of |V W | is the U-phase target voltage V U Absolute value of |V U | or less, or W phase target voltage V W Absolute value of |V W | V Phase Target Voltage V V Absolute value of |V V | If the following is true, or U phase is detected phase current Absolute value of |I U | and V phase detection phase current Absolute value of |I V If either or both of | are equal to or less than the predetermined threshold, it is determined that the W phase does not have an open circuit fault, the determination result is NO, and the W phase open circuit fault determination process of FIG. 19 is terminated. phase current Absolute value of |I u | and V phase detection phase current Absolute value of |I v The predetermined threshold used for the judgment of | is set appropriately depending on the system to be applied.

[0194] Next, in step S1004, the W-phase open fault counter is incremented. The W-phase open fault counter is incremented when it is determined in step S1003 that the W-phase has an open fault, and holds and accumulates a count value from the start of the increment operation until a preset predetermined cumulative time. In addition, after the predetermined cumulative time has elapsed from the start of the increment operation, the counter is cleared to zero. This is provided to prevent malfunctions in the determinations of steps S1002 and S1003 due to disturbances, etc., and depending on the system to which it is applied, it may be a counter that only performs normal increment operations. In that case, it is sufficient to use a determination condition in step S1005 that excludes the conditions within the predetermined cumulative time. In addition, the predetermined cumulative time is set to an appropriate value depending on the system to which it is applied.

[0195] Next, in step S1005, it is confirmed whether the W-phase open fault counter has reached a predetermined count value within a predetermined integration time, which is set to an appropriate value depending on the system to be applied. If the W-phase open fault counter has reached a predetermined count value within a predetermined integration time, it is determined that the W-phase open fault is confirmed, the determination result is YES, and the next step S1006 is executed. If the U-phase open fault counter has not reached a predetermined count value within a predetermined integration time, it is determined that the W-phase open fault is not confirmed, the determination result is NO, and the W-phase open fault determination process in FIG. 19 is terminated.

[0196] Next, in step S1006, if the open fault of the W phase is confirmed, the W phase fault determination flag is turned on and the W phase open fault determination process is terminated. The above is the processing content of the W phase open fault determination process in FIG.

[0197] The above is the content of the individual phase open circuit failure judgment process executed in the processing procedure shown in Fig. 16. Next, in step S703 in Fig. 16, it is judged whether only the U phase has an open circuit failure. For the judgment, the U phase failure judgment flag, V phase failure judgment flag, and W phase failure judgment flag in the U phase open circuit failure judgment process, V phase open circuit failure judgment process, and W phase open circuit failure judgment process in step S702 are used. If the U phase failure judgment flag is on and the V phase failure judgment flag and W phase failure judgment flag are off, In step S703, If the determination result is YES, the next step S704 is executed. In a case other than the condition where the U-phase failure determination flag is ON and the V-phase failure determination flag and the W-phase failure determination flag are OFF, In step S703, The determination result is NO, and the next step S705 is executed.

[0198] In step S704, the open circuit fault result, which is the output of the open circuit fault determination unit 22, is set to a U-phase open circuit fault, and a signal Rof of the open circuit fault result is output to the interruption management unit 17.

[0199] In step S705, it is determined whether only the V phase has an open circuit failure. For this determination, the U phase failure determination flag, the V phase failure determination flag, and the W phase failure determination flag in the U phase open circuit failure determination process, the V phase open circuit failure determination process, and the W phase open circuit failure determination process in step S702 are used. If the V phase failure determination flag is on and the U phase failure determination flag and the W phase failure determination flag are off, In step S705, The result of the determination is YES, and the next step S706 is executed. The result of the determination is NO except for the condition that the V-phase failure determination flag is ON, and the U-phase failure determination flag and the W-phase failure determination flag are OFF. In step S705, The next step S707 is performed.

[0200] In step S706, the open circuit fault result, which is the output of the open circuit fault determination unit 22, is set to a V-phase open circuit fault, and a signal Rof of the open circuit fault result is output to the interruption management unit 17.

[0201] In step S707, it is determined whether only the W phase has an open circuit failure. For this determination, the U phase failure determination flag, the V phase failure determination flag, and the W phase failure determination flag in the U phase open circuit failure determination process, the V phase open circuit failure determination process, and the W phase open circuit failure determination process in step S702 are used. If the W phase failure determination flag is on and the U phase failure determination flag and the V phase failure determination flag are off, In step S707, The result of the determination is YES, and the next step S708 is executed. The W-phase failure determination flag is ON, and the U-phase failure determination flag is OFF. VOnly U phase, only V phase, except when the phase fault judgment flag is off W It is judged to be a fault other than an open fault of only a phase, In step S707, The determination result is NO, and the next step S709 is carried out.

[0202] In step S708, the open circuit fault result, which is the output of the open circuit fault determination unit 22, is set to a W-phase open circuit fault, and a signal Rof of the open circuit fault result is output to the interruption management unit 17.

[0203] In step S709, which is performed if the determination result in step S707 is NO, an increment process of the failure counter is performed.

[0204] The fault counter is a counter that increments when one of the U-phase open fault determination flags determined in the U-phase fault determination process of FIG. 17, the V-phase open fault determination flag determined in the V-phase fault determination process of FIG. 18, and the W-phase open fault determination flag determined in the W-phase fault determination process of FIG. 19 is not on, and holds and accumulates a count value from the start of the increment operation until a predetermined cumulative time set in advance. In addition, after the predetermined cumulative time has elapsed from the start of the increment operation, the counter is cleared to zero. Depending on the system to which the counter is applied, the counter may only perform normal increment operation. In that case, a counter that excludes the condition within the predetermined cumulative time of the determination condition of step S710 may be used. In addition, the specified accumulated time is set to an appropriate value depending on the applicable system, taking into consideration the specified accumulated time adapted to the U-phase open fault counter incremented in the U-phase fault determination process of Figure 17, which is performed in step S702, the V-phase open fault counter incremented in the V-phase fault determination process of Figure 18, and the W-phase open fault counter incremented in the W-phase fault determination process of Figure 19.

[0205] Next, in step S710, it is confirmed whether the failure counter has reached a predetermined count value within a predetermined integration time. The predetermined count value is set to an appropriate value according to the applicable system, taking into consideration the predetermined count values ​​applicable to step S805 of the U-phase failure determination process in Fig. 17, step S905 of the V-phase failure determination process in Fig. 18, and step S1005 of the W-phase failure determination process in Fig. 19. If the failure counter has reached a predetermined count value within a predetermined integration time, it is determined that a failure other than an open-circuit failure in only one of the U, V, and W phases is confirmed, the determination result is YES, and the next step S711 is executed. If the failure counter has not reached a predetermined count value within a predetermined integration time, it is determined that a failure other than an open-circuit failure in only one of the U, V, and W phases is not confirmed, the determination result is NO, and the processing of the open-circuit failure determination unit in FIG. 16 is terminated.

[0206] Next, in step S711, the open circuit failure result, which is the output of the open circuit failure determination unit 22, is set to "other", and the open circuit failure result signal Rof is output to the shutdown management unit 17.

[0207] The above is the description of the process of the open circuit failure determination unit 22 in Fig. 15. After the open circuit failure determination unit 22 performs failure determination and determines the failure determination result, which is the output, the open circuit failure determination unit 22 will not operate again.

[0208] Next, the processing contents of the cutoff management unit 17 in Fig. 15 will be described. In the second embodiment, the processing contents of the cutoff management unit 17 in the first embodiment are modified, and a function is provided in which a decision is made to continue driving the motor in multiple phases other than the open fault phase and a decision is made to stop driving the motor according to the open fault result that is the output of the open fault determination unit 22, and an instruction is output to the control calculation unit 4, the FET gate drive cutoff unit 5, the motor current cutoff unit 9, and the battery voltage cutoff unit 19 according to the decision result.

[0209] Fig. 20 is a flow diagram showing the processing contents of the trip management unit 17. The processing of Fig. 20 performed by the trip management unit 17 is periodic processing performed at a predetermined cycle, and the flow of Fig. 20 is constantly performed at the predetermined cycle. The predetermined cycle is set to an optimum cycle for the applicable system, taking into consideration the execution cycles of the processing of the abnormal torque estimation unit 16, the detected phase current abnormality detection unit 21, the open fault determination unit 22, the current command calculation unit 3, and the control calculation unit 4.

[0210] First, in step S1101, it is determined whether the motor rotation speed calculated from the electrical angle θ obtained by the electrical angle calculation unit 14 is equal to or lower than a preset rotation speed threshold value. In a surface permanent magnet motor, an induced voltage proportional to the motor rotation speed is generated. The current that can be passed through the motor 10 is limited by the voltage difference between the induced voltage due to the rotation of the motor and the battery voltage. Due to this phenomenon, the line current flowing through the motor decreases compared to the indicated current calculated from the detected torque by the torque detector 2, and the detected current I u , I v , I w is the expected target phase current I u_t , I v_t , I w_t The current deviation is the maximum current deviation difference ΔI Diff If the value of the motor speed exceeds the set threshold, there is a risk of an erroneous determination being made. For this reason, step S1101 is set as a monitoring condition for the motor speed in the process flow of FIG.

[0211] The rotation speed threshold, which is a monitoring condition for the motor rotation speed, is made variable according to the battery voltage Vba detected by the battery voltage detection unit 20. For example, the rotation speed at which voltage saturation is reached for each battery voltage is prepared in advance as a map, and the battery voltage Vba detected at a certain regular interval is compared with the map to determine the rotation speed threshold. Also, taking into account the operable voltage of the system, a fixed rotation speed value that does not induce erroneous judgment may be used as the rotation speed threshold instead of varying the rotation speed threshold according to the battery voltage Vba.

[0212] In step S1101, if the motor rotation speed is equal to or lower than the predetermined rotation speed threshold, the determination result is YES, and step S1102 is executed. Greater than In this case, the determination result is NO, and the process of FIG. 20 in the shutdown management unit 17 is terminated.

[0213] Next, in step S1102, it is confirmed whether the open circuit fault result signal Rof output from the open circuit fault judgment unit 22 indicates only a U-phase open circuit fault. If the open circuit fault result signal Rof output from the open circuit fault judgment unit 22 indicates only a U-phase open circuit fault, the judgment result is set to YES, and step S1103 is performed. If the open circuit fault result signal Rof output from the open circuit fault judgment unit 22 indicates not only a U-phase open circuit fault, the judgment result is set to NO, and step S1105 is performed.

[0214] In step S1103, which is performed when the judgment result in step S1102 is YES, the control instruction, which is the output of the cutoff management unit 17 and is an instruction to the control calculation unit 4, is set as a motor drive instruction for a phase other than the U phase, and in the next step S1104, a motor current cutoff instruction INci for the U phase is executed to the motor current cutoff unit 9.

[0215] The motor current cut-off unit 9 cuts off the current path of the U-phase motor line by performing a cut-off operation on the U-phase motor current cut-off unit in the motor current cut-off unit 9 in accordance with the U-phase motor current cut-off instruction INci output from the cut-off management unit 17, and the control calculation unit 4 continues motor drive in phases other than the faulty U-phase in accordance with a motor drive instruction in phases other than the U-phase, which is a control instruction INco from the cut-off management unit 17. The process of continuing motor drive in phases other than the faulty phase may be any process as long as it is executable.

[0216] If the determination result in step S1102 is NO, then in step S1105 it is confirmed whether the open circuit fault result signal Rof output from the open circuit fault determination unit 22 is only a V-phase open circuit fault. If the open circuit fault result signal Rof output from the open circuit fault determination unit 22 is only a V-phase open circuit fault, the determination result is set to YES, and step S1106 is performed. If the open circuit fault result output from the open circuit fault determination unit 22 is not only a V-phase open circuit fault, the determination result is set to NO, and step S1108 is performed.

[0217] In step S1106, which is performed when the judgment result in step S1105 is YES, the control instruction INco, which is the output of the cutoff management unit 17 and an instruction to the control calculation unit 4, is set as a motor drive instruction for a phase other than the V phase, and in the next step S1107, a V-phase motor current cutoff instruction INci is executed for the motor current cutoff unit 9.

[0218] The motor current cut-off unit 9 cuts off the current path of the V-phase motor line by performing a cut-off operation on the V-phase motor current cut-off unit in the motor current cut-off unit 9 in accordance with the V-phase motor current cut-off instruction INci output from the cut-off management unit 17, and the control calculation unit 4 continues motor drive in phases other than the faulty phase, V-phase, in accordance with a motor drive instruction in phases other than V-phase, which is a control instruction from the cut-off management unit 17. The process of continuing motor drive in phases other than the faulty phase may be any process as long as it is executable.

[0219] If the result of the determination in step S1105 is NO, then in step S1108, it is confirmed whether the signal Rof of the open circuit fault result, which is the output of the open circuit fault determination unit 22, is the W-phase open circuit fault only. W If only an open-phase fault exists, the determination result is YES, and step S110 9 When the open circuit fault result signal Rof, which is the output of the open circuit fault determination unit 22, does not indicate only the W-phase open circuit fault, the determination result is set to NO, and step S1111 is performed.

[0220] In step S1109, which is performed when the judgment result in step S1108 is YES, the control instruction INco, which is the output of the cutoff management unit 17 and an instruction to the control calculation unit 4, is set as a motor drive instruction for a phase other than the W phase, and in the next step S1110, a W-phase motor current cutoff instruction INci is executed to the motor current cutoff unit 9.

[0221] The motor current cut-off unit 9 cuts off the current path of the W-phase motor line by cutting off the W-phase motor current cut-off unit in the motor current cut-off unit 9 in accordance with the W-phase motor current cut-off instruction output from the cut-off management unit 17, and the control calculation unit 4 continues motor drive in phases other than the faulty W phase in accordance with the motor drive instruction in phases other than the W phase, which is a control instruction from the cut-off management unit 17. The process of continuing motor drive in phases other than the faulty phase may be any process as long as it is executable.

[0222] If the judgment result in step S1108 is NO, the open fault result output by open fault judgment unit 22 is "other," so it is judged that it is not an open fault of only one phase, and the shutdown management unit 17 outputs a PWM signal forced off instruction as an instruction to control calculation unit 4 in step S1111, outputs a FET gate drive shutdown instruction to FET gate drive shutdown unit 5 in step S1112, outputs a motor current shutdown instruction to motor current shutdown unit 9 in step S1113, and outputs a battery voltage shutdown instruction to battery voltage shutdown unit 19 in step S1114.

[0223] By processing steps S1111, S1112, S1113, and S1114, control calculation unit 4 stops outputting U-phase PWM signal S-PWM(U), V-phase PWM signal S-PWM(V), and W-phase PWM signal S-PWM(W), FET gate drive cut-off unit 5 stops output to FET gate drive unit 6, motor current cut-off unit 9 cuts off motor current of all phases, and battery voltage cut-off unit 19 cuts off the applied voltage from the voltage (power supply voltage) of battery 18 to motor drive device 7, thereby setting the output torque of motor 10 to 0 (zero) and stopping motor drive.

[0224] The above is the processing content of the shutdown management unit 17 executed in the processing procedure shown in Fig. 20. Depending on the signal Rof of the failure determination result which is the output of the open failure determination unit 22, the shutdown management unit 17 judges whether or not the motor should be continued to be driven and issues various instructions for the judgment.

[0225] In this second embodiment, a failure judgment process in the event of an open circuit failure in the FET which is the driving element of the motor driving device 7, a judgment as to whether the motor can continue to be driven, and a process of continuing or stopping the motor drive in response to the judgment as to whether the motor can continue to be driven are described. However, a failure judgment can also be made by the same processing judgment in the event of a disconnection failure in the motor 10 and an open circuit failure in the motor current cut-off unit 9, and this is not limited to the event of an open circuit failure in the FET which is the driving element of the motor driving device 7.

[0226] The motor control device 100 is configured with a processor 101 and a storage device 102, as shown in FIG. 14, which is an example of hardware. The storage device 102 includes, for example, a volatile storage device such as a random access memory, and a non-volatile auxiliary storage device such as a flash memory. Also, instead of the flash memory, a hard disk auxiliary storage device may be included. The processor 101 executes a program input from the storage device 102. In this case, the program is input from the auxiliary storage device to the processor 101 via the volatile storage device. Also, the processor 101 may output data such as a calculation result to the volatile storage device of the storage device 102, or may store the data in the auxiliary storage device via the volatile storage device.

[0227] Although the present application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless modifications not exemplified are assumed within the scope of the technology disclosed in the present specification, including, for example, modifying, adding, or omitting at least one component, and further, extracting at least one component and combining it with a component of another embodiment. [Explanation of symbols]

[0228] 1 Handle, 2 Torque detector, 3 Current command calculation unit, 4 Control calculation unit, 5 FET gate drive cutoff unit, 6 FET gate drive unit, 7 Motor drive device, 10 Motor, 13 Rotor rotation position detector, 14 Electrical angle calculation unit, 15 Detected phase current calculation unit, 16 Abnormal torque estimation unit, 17 Cutoff management unit, 21 Detected phase current abnormality detection unit, 22 Open fault determination unit, 100 Motor control device

Claims

1. a current command calculation unit that determines a target current value of a multi-phase motor; a detected phase current calculation unit that detects currents of each phase flowing through the motor and obtains a detected current value; a control calculation unit that calculates a current command for controlling a motor current based on the target current value and the detected current value; an electrical angle calculation unit that calculates an electrical angle, which is a phase difference between the rotational position of the rotor and a coil of the motor, based on the rotor rotational position of the motor; an abnormal torque estimation unit that calculates a current deviation, which is a difference between the target current value and the detected current value, for each phase from the target current value, the detected current value, and the electrical angle, and estimates an abnormality in torque of the motor based on a difference between a maximum current deviation value that is a maximum value of the current deviation and a minimum current deviation value that is a minimum value of the current deviation; A motor control device comprising: a shutoff management unit that stops driving of the motor if the torque is abnormal.

2. 2. The motor control device according to claim 1, wherein the cutoff management unit stops driving the motor when it is determined that the change in torque estimated by the abnormal torque estimation unit is abnormal.

3. 3. The motor control device according to claim 1, wherein the shutoff management unit does not stop driving of the motor when the motor rotation speed calculated from the electrical angle obtained by the electrical angle calculation unit exceeds a preset rotation speed threshold value.

4. 4. The motor control device according to claim 3, wherein the threshold value of the rotation speed is changed in response to a voltage input to the motor.

5. a detected phase current abnormality detection unit that detects an abnormality in the detected phase current calculation unit; an open circuit fault determination unit that, when the abnormal torque estimation unit estimates that the torque of the motor is abnormal and the detected phase current abnormality detection unit determines that an abnormality has occurred, determines a phase in which an open circuit fault has occurred by using the detected phase current of the detected phase current calculation unit and a voltage command of the control operation unit; The motor control device according to claim 1 , wherein the interruption management unit continues or stops driving of the motor depending on a result of the determination by the open circuit failure determination unit.

6. When an absolute value of a detected phase current of a phase selected by the detected phase current calculation unit is equal to or smaller than a predetermined value, and an absolute value of the voltage command of the selected phase by the control calculation unit is greater than an absolute value of the voltage command of another phase by the control calculation unit, and when the absolute value of the phase current of the selected phase of the detected phase current calculation unit is equal to or smaller than a predetermined value, and the absolute values ​​of the phase currents of the other phases of the detected phase current calculation unit are all greater than a predetermined current threshold value, 6. The motor control device according to claim 5, wherein it is determined that an open fault occurs in a selected phase.

7. 7. The motor control device according to claim 5, wherein the detected phase current abnormality detection unit calculates a sum of the detected phase current values ​​detected by the detected phase current calculation unit, and determines that the detected phase current is abnormal if the sum is equal to or greater than a predetermined threshold value.

8. 8. The motor control device according to claim 5, wherein the cutoff management unit does not execute processing to continue or stop driving of the motor when the motor rotation speed calculated from the electrical angle obtained by the electrical angle calculation unit exceeds a preset rotation speed threshold value.

9. 9. The motor control device according to claim 8, wherein the rotation speed threshold is changed in response to a voltage input to the motor.

10. The motor control device according to any one of claims 5 to 9, characterized in that when the open circuit failure judgment unit judges that an open circuit failure has occurred and that the open circuit failure is in at least one phase, the cutoff management unit has a function of continuing motor drive in other phases that do not have an open circuit failure, and stopping motor drive if there is no open circuit failure.

11. 11. An electric power steering device comprising the motor control device according to claim 1, wherein the motor applies a steering assist torque to wheels of a vehicle.

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