ENGINE CONTROL DEVICE AND ELECTRIC POWER STEERING DEVICE HEREBY

Abstract

A motor control device for a motor (80, 85) comprises: an inverter circuit (20, 120) that supplies power from a battery (5) to the motor; an inverter input voltage detector (41) that detects an inverter input voltage; and a controller (50) that includes a drive controller (55) for the motor and an abnormality determination unit (60) for determining a power supply abnormality. The abnormality determination unit determines the power supply abnormality when the inverter input voltage is below a voltage threshold and a current from the battery to the inverter circuit is within a determinable range. The abnormality determination unit determines whether the current is within the determinable range based on a motor current electrically supplied to the motor or a rotational speed of the motor.A determination threshold in accordance with the determinable range is set such that the inverter input voltage is greater than or equal to the voltage threshold when the power supply range is normal.

Description

[0001] The present invention relates to a motor control device and an electric power steering device having the motor control device.

[0002] An electric power steering device is known that can determine whether a battery or a power supply is the cause of the fault in the event of a faulty stop. For example, in JP 5 205 981 B2, an output voltage of a power source and a current flowing in a power supply are detected by a battery sensor, and based on the detected output voltage and the detected current flowing in the power supply, it is determined whether a battery or the power supply is the cause of the fault.

[0003] In JP 5 205 981 B2, the battery sensor is provided outside of an electronic control unit (ECU). Consequently, the ECU must be equipped with a connector and a receiving circuit for detecting a detection value from the battery sensor. Furthermore, since the battery sensor itself must be monitored, the device may increase in size.

[0004] From JP 2006-129 567 A, a fault detection processing method and a fault detection processing apparatus in a motor drive apparatus of a vehicle, such as a hybrid vehicle and an electric vehicle, are also known.

[0005] JP H08-324 448 A discloses a diagnostic device for an electric steering device for a vehicle, and more particularly, a device for diagnosing an abnormality in a power supply voltage of a steering actuator.

[0006] It is an object of the present invention to provide a motor control device that determines a power supply abnormality without using a detection value of a battery current, and an electric power steering device having a motor control device.

[0007] The problem is solved by the subject matter of the independent claims. Advantageous further developments are specified in the dependent claims.

[0008] In the motor control devices according to the present invention, the power supply abnormality determination is performed based on the inverter input voltage and the like, without using a battery current detection value. Consequently, the device can be simplified compared to the case where the battery current detection value is used.

[0009] Furthermore, when the power consumption in the motor is high, the current from the battery to the inverter circuit increases, causing an increase in the voltage drop due to a wiring resistance in the power supply region, resulting in a decrease in the inverter input voltage. In this situation, if the power supply abnormality determination is performed by only performing the threshold determination on the inverter input voltage, the voltage drop due to the wiring resistance may be erroneously determined as the power supply abnormality. Accordingly, in the motor control devices according to the present invention, when the inverter input voltage is below the voltage threshold and the current from the battery to the inverter circuit is within the determinable range, it is determined that the power supply abnormality has occurred.Consequently, the voltage drop due to the line resistance that occurs when a large current is supplied from the battery to the inverter circuit can be prevented from being erroneously determined as the power supply abnormality.

[0010] In the electric power steering apparatus according to the present invention, the power supply abnormality determination is performed based on the inverter input voltage and the like without using a battery current detection value. Consequently, the apparatus can be simplified compared to the case where the battery current detection value is used.

[0011] Furthermore, in the above electric power steering device, when the inverter input voltage is below the voltage threshold and the current from the battery to the inverter circuit is within the determinable range, it is determined that a power supply abnormality has occurred. Consequently, the voltage drop caused by the wiring resistance, which occurs when a high current is supplied from the battery to the inverter circuit, can be prevented from being erroneously determined as a power supply abnormality.

[0012] The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. In the drawings: Fig. 1 is a schematic diagram showing a configuration of an electric power steering system according to a first embodiment of the present invention; Fig. 2 is a circuit diagram illustrating a motor control device according to the first embodiment of the present invention; Fig. 3 is a flowchart illustrating abnormality determination processing according to the first embodiment of the present invention; Fig. 4 is a flowchart illustrating abnormality determination processing according to a second embodiment of the present invention; Fig. 5 is a flowchart illustrating abnormality determination processing according to a third embodiment of the present invention; Fig. 6 is an exemplary diagram illustrating a rotation frequency threshold according to the third embodiment of the present invention; Fig. 7 is a circuit diagram illustrating a motor control device according to a fourth embodiment of the present invention; Fig. 8 is a flowchart illustrating abnormality determination processing according to the fourth embodiment of the present invention; Fig. 9 is a flowchart illustrating abnormality determination processing according to a fifth embodiment of the present invention; Fig. 10 is a flowchart illustrating abnormality determination processing according to a sixth embodiment of the present invention; Fig. 11 is a flowchart illustrating abnormality determination processing according to a seventh embodiment of the present invention; Fig. 12 is a flowchart illustrating abnormality determination processing according to an eighth embodiment of the present invention; and Fig. 13 is a circuit diagram illustrating a motor control device according to a ninth embodiment of the present invention.

[0013] A motor control device of the present invention and an electric power steering device incorporating the motor control device will be described below with reference to the drawings. In several embodiments described below, substantially similar configurations are denoted by the same reference numerals and will not be described repeatedly to avoid redundancy. (First embodiment)

[0014] The Fig. 1 to 3 show a first embodiment of the present invention.

[0015] As in Fig. 1, a motor control device 1 as a rotating electric machine control device is applied to an electric power steering device 8 for assisting steering by a driver in conjunction with a motor 80.

[0016] Fig. 1 shows a configuration of a steering system 90 equipped with the electric power steering device 8. The steering system 90 includes a steering wheel 91 as a steering element, a steering shaft 92, a gear train 96, a rack 97, wheels 98, the electric power steering device 8, and the like.

[0017] The steering wheel 91 is connected to the steering shaft 92. The steering shaft 92 is equipped with a torque sensor 94 for detecting a steering torque applied by the driver operating the steering wheel 91. The gear train 96 is arranged at the tip of the steering shaft 92. The gear train 96 is engaged with the rack 97. A pair of wheels 98 are connected to both ends of the rack 97 via tie rods or the like.

[0018] When the driver operates the steering wheel 91, the steering shaft 92 connected to the steering wheel 91 rotates. The rotational movement of the steering shaft 92 is converted by the gear transmission 96 into a linear movement of the rack 97. The pair of wheels 98 are steered at an angle in accordance with a displacement amount of the rack 97.

[0019] The electric power steering device 8 includes the motor 80, a reduction gear 89 that reduces the rotation of the motor 80 and transmits the rotation to the steering shaft 92, the motor control device 1, and the like. The electric power steering device 8 of the present embodiment is of the so-called "column assist type," but may be of the so-called "rack assist type," which transmits the rotation of the motor 80 to the rack 97.

[0020] The motor 80 outputs an auxiliary torque to assist steering of the steering wheel 91 by the driver and is operated by being supplied with energy from a battery 5 (see Fig. 2) to rotate the reduction gear 89 back and forth. The motor 80 of the present embodiment is a brushless three-phase (AC) motor.

[0021] As in Fig. 2, the motor control device 1 includes a power input circuit 10, an inverter circuit 20, a current detection part 30, an inverter input voltage detection part 41, a control part 50, and the like.

[0022] The power input circuit 10 includes a power interruption part 11 and a capacitor 12 and is connected between the battery 5 and the inverter circuit 20. The battery 5 and the power input circuit 10 are connected using a wire harness or the like. Fig. In Figure 2, a line resistance 70 between the battery 5 and the power input circuit 10 is shown as a resistor 71 on a high-potential side and a resistor 72 on a low-potential side. Hereinafter, a voltage of the battery 5 is referred to as a battery voltage Vbat.

[0023] The power interruption part 11 can interrupt the power supply from the battery 5 to the inverter circuit 20. The capacitor 12 is connected in parallel with the battery 5 and the inverter circuit 20. The capacitor 12 stores charges to support the power supply to the inverter circuit 20 and mitigates noise components such as surge current.

[0024] The inverter circuit 20 includes six switching elements 21 to 26 and converts power supplied to the motor 80. Hereinafter, each "switching element" is referred to as an "SW element." The SW elements 21 to 23 are connected to the high potential side, and the SW elements 24 to 26 are connected to the low potential side. A node of the paired U-phase SW elements 21, 24 is connected to one end of a U-phase coil 81. A node of the paired V-phase SW elements 22, 25 is connected to one end of a V-phase coil 82. A node of the paired W-phase SW elements 23, 26 is connected to one end of a W-phase coil 83. The other ends of the U-phase coil 81, the V-phase coil 82 and the W-phase coil 83 are connected.

[0025] The SW elements 21 to 26 of the present embodiment are metal oxide semiconductor field effect transistors (MOSFETs), but may be insulated gate bipolar transistors (IGBTs), thyristors, or the like.

[0026] The current detection part 30 has current detection elements 31, 32, 33. The current detection elements 31 to 33 of the present embodiment are shunt resistors.

[0027] The U-phase current detection element 31 is connected to the low potential side of the SW element 24 and detects a U-phase current Iu flowing in the U-phase coil 81. A voltage across the ends of the U-phase current detection element 31 is input to the control part 50 as a detection value in accordance with the U-phase current Iu.

[0028] The V-phase current detection element 32 is connected to the low potential side of the SW element 25 and detects a V-phase current Iv flowing in the V-phase coil 82. A voltage across the ends of the V-phase current detection element 32 is input to the control part 50 as a detection value corresponding to the V-phase current Iv.

[0029] The W-phase current detection element 33 is connected to the low potential side of the SW element 26 and detects a W-phase current Iw flowing in the W-phase coil 83. A voltage across the ends of the W-phase current detection element 33 is input to the control part 50 as a detection value in accordance with the W-phase current Iw.

[0030] The inverter input voltage detection part 41 is connected between the power interruption part 11 and the SW elements 21 to 23 on the high potential side, and detects an inverter input voltage Vinv, which is a voltage to be input to the inverter circuit 20. A detection value of the inverter input voltage detection part 41 is output to the control part 50.

[0031] Further, a rotation angle sensor (not shown) that detects a rotation angle θ of the motor 80 outputs a detection value in accordance with the rotation angle θ to the control part 50.

[0032] The control section 50 is mainly composed of a microcomputer. Each processing in the control section 50 may be software processing executed by a central processing unit (CPU) that executes a program stored in advance in a physical storage device such as a read-only memory (ROM), or hardware processing executed by a dedicated electronic circuit.

[0033] The control part 50 controls the drive of the motor 80 and includes a drive control part 55, an abnormality determination part 60 and the like as a functional block.

[0034] The drive control part 55 controls the drive of the motor 80 by controlling an on / off operation of the SW elements 21 to 26 based on the phase currents Iu, Iv, Iw detected by the current detection part 30, the rotation angle θ detected by the rotation angle sensor (not shown), the steering torque detected by the torque sensor 94, and the like. In the present embodiment, the drive control part 55 generates a drive signal that controls the on / off operation of the SW elements 21 to 26 using PWM (Pulse Width Modulation) control to control a duty ratio of the SW elements 21 to 26 such that a feedback current detection value matches a current command value. The generated drive signal is output to gates of the SW elements 21 to 26 via a preamplifier and the like. The on / off operation of the SW elements 21 to 26 is controlled based on the control signal.

[0035] It should be noted that the method for controlling the motor 80 is not limited to PWM control, but may be any other control method.

[0036] The abnormality determination part 60 determines a power supply abnormality in a power supply region Rin, which is a channel from the battery 5 to the inverter circuit 20. The term "power supply abnormality" in the present embodiment describes an abnormality in which power cannot be supplied from the battery 5 to the inverter circuit 20, and includes a breakage of the wire harness in the power supply region Rin, a ground fault of the power input circuit 10, and the like.

[0037] When the power supply abnormality occurs, the inverter input voltage Vinv decreases and the current from the battery 5 to the inverter circuit 20 also decreases.

[0038] Furthermore, in the present embodiment, the motor 80 is used for the electric power steering device 8 with a relatively high power consumption. Accordingly, when the power consumption in the motor 80 is high, the current drawn from the battery 5 to the inverter circuit 20 may increase, causing an increase in the voltage drop across the wiring resistance 70, resulting in a decrease in the inverter input voltage Vinv. Herein, if it is determined that the power supply abnormality has occurred in the power supply region Rin when the inverter input voltage Vinv is simply below a predetermined value, it is erroneously determined that the power supply abnormality has occurred, regardless of the fact that the voltage drop occurred due to the high drawn current.

[0039] Therefore, in the present embodiment, with respect to the power consumption in the motor 80, the power supply abnormality in the power supply region Rin is determined based on the inverter input voltage Vinv.

[0040] The following describes abnormality determination processing in the present embodiment with reference to the Fig. The flowchart shown in Figure 3 is described.

[0041] In step S101, the abnormality determination part 60 first reads the inverter input voltage Vinv. Hereinafter, "step" of step S101 is omitted and simply denoted by the symbol "S." This also applies to the other steps.

[0042] In S102, the abnormality determination part 60 determines whether the inverter input voltage Vinv is below the voltage threshold Vinv_th. If it is determined that the inverter input voltage Vinv is not below the voltage threshold Vinv_th (S102: NO), the processing proceeds to S106. If it is determined that the inverter input voltage Vinv is below the voltage threshold Vinv_th (S102: YES), the processing proceeds to S103.

[0043] In S103, the abnormality determination part 60 reads the phase currents Iu, Iv, Iw detected by the current detection part 30 to calculate a current determination value Ij11. The current determination value Ij11 is a square root of the sum of squares of the phase currents Iu, Iv, Iw and is calculated using the following equation (1). lj11=√{(lu)2+(lv)2+(lw)2}

[0044] In S104, the abnormality determination part 60 determines whether the current determination value Ij11 is below a current threshold value Ith1. The current threshold value Ith1 will be described later. If it is determined that the current determination value Ij11 is below the current threshold value Ith1 (S104: YES), the current drawn from the battery 5 to the inverter circuit 20 is deemed to be within the determinable range, and processing proceeds to S105. If it is determined that the current determination value Ij11 is not below the current threshold value Ith1 (S104: NO), the current drawn from the battery 5 to the inverter circuit 20 is deemed to be outside the determinable range, and processing proceeds to S106.

[0045] In S105, to which the processing proceeds when the inverter input voltage Vinv is below the voltage threshold Vinv_th and the current determination value Ij11 is below the current threshold Ith1 (S102: YES, and S104: YES), it is determined that the power supply abnormality has occurred.

[0046] In S106, to which the processing proceeds, when the inverter input voltage Vinv is not less than the voltage threshold Vinv_th (S102: NO) or the current determination value Ij11 is not less than the current threshold Ith1 (S104: NO), it is assumed that the power supply abnormality has not occurred, and a normality determination is made.

[0047] The current threshold Ith1 is described below.

[0048] First, a lower limit of the battery voltage Vbat when the entire device is normal is referred to as a lower battery voltage limit Vbat_min. For example, assume that the specific voltage of battery 5 is 12 [V] and the lower battery voltage limit Vbat_min is 9 [V]. However, these voltage values are merely examples and can be set as appropriate. This also applies to the voltage values shown below as examples.

[0049] The difference between the lower battery voltage limit Vbat_min and the voltage threshold Vinv_th is referred to as a voltage drop amount threshold ΔV_th (Equation (2)). For example, if the voltage threshold Vinv_th is 5 [V], the voltage drop amount threshold ΔV_th is 4 [V]. ΔV_th=Vbat_min−Vinv_th

[0050] Here, the inverter input voltage Vinv falls below the voltage threshold Vinv_th when the battery 5 is equal to the battery voltage lower limit Vbat_min, the drawn current is high, and a voltage drop amount ΔV, which describes a difference between the battery voltage Vbat and the inverter input voltage Vinv, is above the voltage drop amount threshold ΔV_th. In this case, if the abnormality determination is made solely based on the comparison between the inverter input voltage Vinv and the voltage threshold Vinv_th, an erroneous determination may be made that the power supply abnormality has occurred, even though the power supply abnormality has not occurred.In order to avoid such an erroneous determination, in the present embodiment, the abnormality determination part 60 performs the power supply abnormality determination in a range where the voltage drop amount ΔV is below the voltage drop amount threshold value ΔV_th.

[0051] When a resistance value of the wire resistor 70 is referred to as a wire resistance value Rwire and the current drawn from the battery 5 to the inverter 20 is referred to as a battery current Ibat, the voltage drop amount ΔV is described by the following equation (3). ΔV=Rwire×lbat

[0052] Since the wire resistance value Rwire is a fixed parameter, the battery current threshold value Ibat_th at the time when the voltage drop amount ΔV is equal to the voltage drop amount threshold value ΔV_th is described by the following equation (4). lbat_th=ΔV_th / Rwire

[0053] In the motor control device 1, assuming that the input power and power consumption are equal, the following equation (5) holds. Vinv×lbat=Vu×lu+Vv×lv+Vw×lw

[0054] Furthermore, when the voltage command values Vu*, Vv*, Vw* of the respective phases are used to instruct ratios with respect to the inverter input voltage Vinv, the phase voltages Vu, Vv, Vw are described by the following equations (6-1) to (6-3). Vu=Vinv×Vu* Vv=Vinv×Vv* Vw=Vinv×Vw*

[0055] When equation (5) is converted using equations (6-1) to (6-3), the following equation (7) is obtained. lbat=Vu*×lu+Vv*×lv+Vw*×lw

[0056] When equation (7) is converted using the phase voltage command values, the square root of the sum of squares of the phase currents and the power factor cosφ, the following equation (8) is obtained. lbat=√{(Vu*)2+(Vv*)2+(Vw*)2}×√{(lu)2+(lv)2+(lw)2}×cosφ

[0057] If the maximum value obtained by the square root of the sum of squares of the phase voltage command values (ie √{(Vu*) 2 + (V V *) 2 + (V W *) 2}) is referred to as V*max, at the time when the square root of the sum of squares of the phase voltage command values is equal to the maximum value V*max, the equation (8) is equal to the following equation (9). lbat / V*max / cosφ=√{(lu)2+(lv)2+(lw)2}lbat / V*max / cosφ=lj11

[0058] If the battery current Ibat in equation (9) is referred to as a battery current threshold Ibat_th, equation (9) becomes equations (10-1), (10-2). lbat_th / V*max / cosφ=lj11(ΔV_th / Rwire) / V*max / cosφ=lj11 {(Vbat_min−Vinv_th) / Rwire} / V*max / cosφ=lj11

[0059] In the present embodiment, the current threshold Ith1 is assumed to be less than or equal to the value on the left side of equation (10-2). Specifically, the current threshold Ith1 is determined in accordance with a value obtained by subtracting the voltage threshold Vinv_th from the battery voltage lower limit Vbat_min, dividing it by the wire resistance value Rwire, the maximum value V*max of the square root of the sum of squares of the phase currents, and the power factor cosφ. More specifically, the current threshold Ith1 is determined in accordance with the voltage threshold Vinv_th.

[0060] In the case where the current determination value Ij11 is below the current threshold value Ith1, if the voltage drop across the wiring resistance 70 is small and the power supply abnormality has not occurred, the inverter input voltage Vinv is not below the voltage threshold value Vinv_th. Therefore, in the present embodiment, when the current determination value Ij11 is below the current threshold value Ith1, the current drawn from the battery 5 to the inverter circuit 20 is considered to be within the determinable range. That is, if the inverter input voltage Vinv is below the voltage threshold value Vinv_th and the current determination value Ij11 is below the current threshold value Ith1, it can be determined that the inverter input voltage Vinv has decreased not due to the voltage drop accompanying the increase in the drawn current, but due to the occurrence of the power supply abnormality.Consequently, the energy supply abnormality can be determined appropriately.

[0061] Meanwhile, when the current determination value Ij11 is not less than the current threshold Ith1, the drawn current is high, causing an increase in the voltage drop across the line resistance 70. In such a case, the inverter input voltage Vinv may fall below the voltage threshold Vinv_th depending on the battery voltage Vbat. Therefore, in the present embodiment, when the current determination value Ij11 is not less than the current threshold Ith1, the current drawn from the battery 5 to the inverter circuit 20 is deemed to be outside the determinable range, and the power supply abnormality determination is not made, but the normality determination is made. Therefore, the erroneous determination that the power supply abnormality has occurred when a voltage drop has occurred due to a large drawn current can be avoided.

[0062] That is, in the present embodiment, a determination can be made as to whether the inverter input voltage Vinv has temporarily decreased along with an increase in the drawn current or whether the inverter input voltage Vinv has decreased due to the power supply abnormality by monitoring the inverter input voltage Vinv and the phase currents Iu, Iv, Iw. This also applies to the other embodiments.

[0063] It should be noted that the current threshold value Ith1 is preferably set to the value on the left side of equation (10-2) or a value as close as possible to the value on the left side of equation (10-2). Consequently, the determinable range for a power supply abnormality can be kept wide. This also applies to the other embodiments.

[0064] In the present embodiment, the current threshold Ith1 is assumed to be a fixed value determined in advance by performing the above calculation offline. Furthermore, in the second to sixth embodiments described below, each threshold, like the first embodiment, is assumed to be a fixed value. Using a fixed value as a threshold allows for a reduction in the computational load.

[0065] In the present embodiment, a value such as the inverter input voltage Vinv to be used for power supply abnormality determination can be detected within the motor control device 1. Therefore, compared with the case where the abnormality determination is performed using the detection value of the battery current Ibat, the number of terminals can be reduced and the receiving circuit for the detection value of the battery current Ibat can be omitted, so the configuration can be simplified. Furthermore, although the battery current Ibat is used in the description of the derivation for the current threshold value Ith1, the detection value of the battery current Ibat is not used in the actual power supply abnormality determination.

[0066] Furthermore, since it is not necessary to restrict the current command value, the voltage command value, and the like, the power supply abnormality determination can be made without causing a decrease in the torque T and the rotation frequency N of the motor 80.

[0067] Furthermore, instead of the current determination value Ij11 based on the phase currents Iu, Iv, Iw described above, a current determination value Ij12 based on a d-axis current Id and a q-axis current Iq obtained by converting the phase currents Iu, Iv, Iw into dq-axis coordinates via the rotation angle θ may be used. Hereinafter, the d-axis current Id and the q-axis current Iq may be referred to as "dq-axis currents Id, Iq," as appropriate.

[0068] That is, the current determination value Ij12 is a square root of the sum of the squares of the dq-axis currents Id, Iq and is described by the following equation (11). Furthermore, when the current determination value Ij12 is used instead of the current determination value Ij11, the current threshold value Ith1 is determined in a similar manner. lj12=√{(ld)2+(lq)2}

[0069] As described above, the motor control device 1 of the present embodiment controls the drive of the motor 80 and includes the inverter circuit 20, the inverter input voltage detection part 41, and the control part 50. The inverter circuit 20 supplies the motor 80 with power from the battery 5. The inverter input voltage detection part 41 detects the inverter input voltage Vinv to be input to the inverter circuit 20.

[0070] The control part 50 includes the drive control part 55 and the abnormality determination part 60. The drive control part 55 controls the drive of the motor 80. The abnormality determination part 60 determines the power supply abnormality in which the power cannot be supplied from the battery 5 to the inverter circuit 20 in the power supply region Rin between the battery 5 and the inverter circuit 20.

[0071] When the inverter input voltage Vinv is below the voltage threshold Vinv_th and the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range, the abnormality determination part 60 determines that the power supply abnormality has occurred.

[0072] The determination as to whether the current is within the determinable range is made based on a motor current electrically supplied to the motor 80. The determination threshold in accordance with this determination is determined such that the inverter input voltage Vinv is not lower than the voltage threshold Vinv_th when the power supply section Rin is normal. In the present embodiment, each of the phase currents Iu, Iv, Iw or the dq-axis currents Id, Iq is a "motor current," and the current threshold Ith1 is a "determination threshold."

[0073] In the present embodiment, the power supply abnormality determination is performed based on the inverter input voltage Vinv and the like, without using a detection value of the battery current Ibat. Therefore, the device can be simplified compared to the case where the detection value of the battery current Ibat is used.

[0074] Furthermore, when the power consumption in the motor 80 is high, the current drawn from the battery 5 to the inverter circuit 20 may increase, causing an increase in the voltage drop across the wiring resistance 70 in the power supply range Rin, resulting in a decrease in the inverter input voltage Vinv. In this situation, if the threshold determination is performed only on the inverter input voltage Vinv, the voltage drop across the wiring resistance 70 may be erroneously determined as the power supply abnormality. Therefore, in the present embodiment, when the inverter input voltage Vinv is below the voltage threshold Vinv_th and the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range, it is determined that the power supply abnormality has occurred.Accordingly, the voltage drop due to the line resistance, which occurs due to a large current drawn from the battery 5 to the inverter circuit 20, can be prevented from being erroneously determined as the power supply abnormality.

[0075] When the current determination value Ij11 or the current determination value Ij12 calculated from the motor current is below the current threshold value Ith1, which is the determination threshold, the abnormality determination part 60 determines that the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range. In the present embodiment, the motor 80 is a three-phase motor, and the current determination value Ij11 is a square root of the sum of the squares of the phase currents Iu, Iv, Iw. Further, the current determination value Ij12 is a square root of the sum of the squares of the dq-axis currents Id, Iq.

[0076] Therefore, whether the current drawn from battery 5 to inverter circuit 20 is within the determinable range can be appropriately determined based on the motor current. Furthermore, when the current is not flowing due to the power supply abnormality, the phase currents Iu, Iv, Iw and the dq-axis currents Id, Iq are zero. Therefore, using the square root of the sum of the squares of the currents facilitates the determination of the power supply abnormality.

[0077] The electric power steering apparatus 8 includes the motor control device 1 and the motor 80 that outputs auxiliary torque to assist the driver's steering. In the motor control device 1 of the present embodiment, the voltage drop due to the wiring resistance, which occurs due to a large current drawn from the battery 5 to the inverter circuit 20, can be prevented from being erroneously determined as the power supply abnormality. Therefore, the motor control device 1 is suitably applied to a device with a relatively high power consumption, such as the electric power steering apparatus 8. Furthermore, since it is not necessary to restrict the voltage command value and the current command value in the power supply abnormality determination, the power supply abnormality determination can be made without giving the driver a strange feeling.to give a feeling of discomfort when steering. (Second embodiment)

[0078] Fig. Fig. 4 shows a second embodiment of the present invention. In the present embodiment, the abnormality determination processing differs from that in the above embodiment, and therefore, a description will be given mainly with reference to it.

[0079] The abnormality determination processing of the present embodiment is described below with reference to the Fig. The flowchart shown in Figure 4 is described.

[0080] The processing of S201 and S202 is the same as the processing of S101 and S102 in the Fig. 3.

[0081] In S203, the abnormality determination part 60 calculates a current determination value Ij21. That is, the present embodiment differs from the above embodiment in that the current determination value Ij21 is used instead of the current determination value Ij11 for determining whether the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range. The current determination value Ij21 is a value based on the currents and voltages of the respective phases and is equal to the sum of values each obtained by multiplying the current value and the voltage value of each phase. In the present embodiment, a detection value based on a value detected by the current detection part 30 is used as the current value, and the voltage command values Vu*, Vv*, Vw*, which are command values, are used as the voltage values (see equation (12)). lj21=Vu*×lu+Vv*×lv+Vw*×lw

[0082] In S204, the abnormality determination part 60 determines whether the current determination value Ij21 is below a current threshold value Ith2. If the current determination value Ij21 is determined to be below the current threshold value Ith2 (S204: YES), the current drawn from the battery 5 to the inverter circuit 20 is deemed to be within the determinable range, and processing proceeds to S205. If the current determination value Ij21 is determined to be not less than the current threshold value Ith2 (S204: NO), the current drawn from the battery 5 to the inverter circuit 20 is deemed to be outside the determinable range, and processing proceeds to S206.

[0083] The processing of S205 and S206 is the same as the processing of S105 and S106.

[0084] The current threshold Ith2 is described below. If the battery current Ibat in Equation (7) is defined as a battery current threshold Ibat_th, Equation (7) becomes Equations (13-1), (13-2). lbat_th=Vu*×lu+Vv*×lv+Vw*×lwΔV_th / Rwire = lj21 (Vbat_min−Vinv_th) / Rwire=lj21

[0085] In the present embodiment, the current threshold Ith2 is assumed to be a value not higher than the value on the left side of equation (13-2). Specifically, the current threshold Ith2 is determined according to a value obtained by subtracting the voltage threshold Vinv_th from the battery voltage lower limit Vbat_min and dividing it by the wire resistance value Rwire. Specifically, the current threshold Ith2 is determined according to the voltage threshold Vinv_th.

[0086] In the case where the current determination value Ij21 is below the current threshold Ith2, if the voltage drop across the wiring resistance 70 is small and the power supply abnormality has not occurred, the inverter input voltage Vinv is not below the voltage threshold Vinv_th. In the present embodiment, if the current determination value Ij21 is determined to be below the current threshold Ith2, the current drawn from the battery 5 to the inverter circuit 20 is considered to be within the determinable range. That is, if the inverter input voltage Vinv is below the voltage threshold Vinv_th and the current determination value Ij21 is below the current threshold Ith2, it can be determined that the inverter input voltage Vinv has decreased not due to the voltage drop accompanying the increase in the drawn current, but due to the occurrence of the power supply abnormality.Consequently, the energy supply abnormality can be determined appropriately.

[0087] Meanwhile, when the current determination value Ij21 is not less than the current threshold Ith2, the drawn current is high, causing an increase in the voltage drop across the line resistance 70. In such a case, the inverter input voltage Vinv may fall below the voltage threshold Vinv_th depending on the battery voltage Vbat. Therefore, in the present embodiment, when the current determination value Ij21 is not less than the current threshold Ith2 and the current drawn from the battery 5 to the inverter circuit 20 is deemed to be outside the determinable range, the power supply abnormality determination is not made, but the normality determination is made. Thus, the erroneous determination that the power supply abnormality has occurred when a voltage drop has occurred due to a high drawn current can be prevented.

[0088] Furthermore, instead of the current determination value Ij21 based on the products of the currents and voltages of the respective phases described above, a current determination value Ij22 based on the product of the currents and voltages of the dq axes may be used. That is, the current determination value Ij22 is described by the following equation (14). Furthermore, when the current determination value Ij22 is used instead of the current determination value Ij21, the current threshold value Ith2 is determined in a similar manner. lj22=vd*×ld+Vq*×lq

[0089] In the present embodiment, the current determination value Ij21 is the sum of values obtained by multiplying each of the phase currents Iu, Iv, Iw, which describe the current values of the respective phases, and each of the voltage command values Vu*, Vv*, Vw*, which describe the voltage values. Furthermore, the current determination value Ij22 is the sum of values obtained by multiplying each of the dq-axis currents Id, Iq, which describe the current values of the respective dq axes, and each of the dq-axis voltage command values Vd*, Vq*, which describe the voltage values.

[0090] Therefore, based on the motor current, it can be appropriately determined whether the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range. In the present embodiment, current control is performed, and the value of the product of the current value and the voltage value hardly changes because the voltage command value increases as the current value decreases. Consequently, erroneous determination rarely occurs, and power supply abnormality determination can be made with higher accuracy.

[0091] Furthermore, an effect similar to that of the above embodiment can be produced. (Third embodiment)

[0092] The Fig. 5 and Fig. 6 shows a third embodiment of the present invention. In the present embodiment, the abnormality determination processing differs from that of the above embodiment, and therefore, a description will be given mainly with reference to it.

[0093] The processing of S301 and S302 is the same as the processing of S101 and S102 in the Fig. 3.

[0094] In S303, the abnormality determination part 60 calculates the rotation frequency N of the motor 80 based on the rotation angle θ. If the rotation frequency N has been calculated by another controller or the like, the calculated value may be acquired without the abnormality determination part 60 performing the calculation.

[0095] In S304, the abnormality determination part 60 determines whether the rotation frequency N is below a first rotation frequency threshold Nth1 or whether the rotation frequency N is above a second rotation frequency threshold Nth2. If the rotation frequency N is below the first rotation frequency threshold Nth1 or if the rotation frequency N is above the second rotation frequency threshold Nth2 (S304: YES), the current drawn from the battery 5 to the inverter circuit 20 is deemed to be within the determinable range, and processing proceeds to S305. If the rotation frequency N is not below the first rotation frequency threshold Nth1 or if the rotation frequency N is not above the second rotation frequency threshold Nth2 (S304: NO), the current drawn from the battery 5 to the inverter circuit 20 is deemed not to be within the determinable range, and processing proceeds to S306.Hereinafter, the state in which the rotation frequency N is below the first rotation frequency threshold Nth1 or in which the rotation frequency N is above the second rotation frequency threshold Nth2 is appropriately described as a state in which “the rotation frequency N satisfies the determination condition”.

[0096] The processing of S305 and S306 is the same as the processing of S105 and S106.

[0097] The rotation frequency threshold values Nth1, Nth2 are shown below with reference to the Fig. 6 described.

[0098] Fig. Figure 6 shows a characteristic diagram illustrating the relationship between the rotational frequency N of the motor 80, the torque T and the battery current Ibat. Fig. 6, the rotational frequency N is plotted on the horizontal axis and the torque T and the battery current Ibat are plotted on a vertical axis.

[0099] When the rotation frequency N is not greater than a predetermined value Na, the torque T of the motor 80 assumes a maximum torque value Tmax. Furthermore, when the rotation frequency N is greater than the predetermined value Na, the torque T decreases with increasing rotation frequency N.

[0100] When the rotation frequency N is not greater than the predetermined value Na, the battery current Ibat increases with increasing rotation frequency N. Furthermore, when the rotation frequency N is greater than the predetermined value Na, the battery current Ibat increases with increasing rotation frequency N. When the rotation frequency N is equal to the predetermined value Na, the battery current Ibat assumes a maximum current value Ibat_max. Furthermore, the battery current threshold Ibat_th assumes a value smaller than the maximum current value Ibat_max.

[0101] In the present embodiment, it is assumed that a smaller value of the rotation frequencies N at which the battery current Ibat becomes the battery current threshold Ibat_th is the first rotation frequency threshold Nth1, and a higher value thereof is the second rotation frequency threshold Nth2.

[0102] In the present embodiment, the rotation frequency thresholds Nth1, Nth2 are determined based on the battery current threshold Ibat_th, which is the battery current Ibat when the voltage drop amount ΔV is the voltage drop amount threshold ΔV_th. The voltage drop amount threshold ΔV_th is a value based on the voltage threshold Vinv_th (see equations (2), (4)). That is, the rotation frequency thresholds Nth1, Nth2 can be assumed to be values based on the voltage threshold Vinv_th.

[0103] When the rotation frequency N satisfies the determination condition, the battery current Ibat is below the battery current threshold Ibat_th. For this reason, when the voltage drop across the wiring resistance 70 is small and the power supply abnormality has not occurred, the inverter input voltage Vinv is not below the voltage threshold Vinv_th. Therefore, in the present embodiment, when the rotation frequency N satisfies the determination condition, the current drawn from the battery 5 to the inverter circuit 20 is considered to be within the determinable range. That is, when the inverter input voltage Vinv is below the voltage threshold Vinv_th and the rotation frequency N satisfies the determination condition, it can be determined that the inverter input voltage Vinv has decreased not due to the voltage drop accompanying the increase in the drawn current, but due to the occurrence of the power supply abnormality.Consequently, the energy supply abnormality can be determined appropriately.

[0104] In contrast, when the rotation frequency N is not lower than the first rotation frequency threshold Nth1 and not higher than the second rotation frequency threshold Nth2, and the rotation frequency N does not satisfy the determination condition, the drawn current is high, causing an increase in the voltage drop across the wiring resistance 70. In such a case, the inverter input voltage Vinv may fall below the voltage threshold Vinv_th depending on the battery voltage Vbat. Therefore, in the present embodiment, when the rotation frequency N does not satisfy the determination condition, the current drawn from the battery 5 to the inverter circuit 20 is deemed to be outside the determinable range, and the power supply abnormality determination is not made, but the normality determination is made.In this way, the erroneous determination that the power supply abnormality has occurred when a voltage drop has occurred due to a high drawn current can be prevented.

[0105] In the present embodiment, the determination is made as to whether the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range based on the rotation frequency N of the motor 80. The determination threshold in accordance with this determination is set such that the inverter input voltage Vinv is not lower than the voltage threshold Vinv_th when the power supply range Rin is normal.

[0106] Even if the rotation frequency N is used instead of the motor current, the determination as to whether the current is within the determinable range can be made appropriately as described above.

[0107] The determination threshold is the first rotation frequency threshold Nth1 and the second rotation frequency threshold Nth2, which is a higher value than the first rotation frequency threshold Nth1. When the rotation frequency N is below the first rotation frequency threshold Nth1, or when the rotation frequency N is above the second rotation frequency threshold Nth2, the abnormality determination part 60 determines that the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range.

[0108] Consequently, based on the rotational frequency N of the motor 80, it can be appropriately determined whether the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range.

[0109] Furthermore, an effect similar to those of the above embodiments can be produced.

[0110] In the present embodiment, the rotation frequency N corresponds to a "rotational speed," the first rotation frequency threshold Nth1 corresponds to a "first rotational speed threshold," and the second rotation frequency threshold Nth2 corresponds to a "second rotational speed threshold." This also applies to the sixth embodiment and the like. (Fourth embodiment)

[0111] The Fig. 7 and Fig. 8 show a fourth embodiment of the present invention.

[0112] As in Fig. 7, a motor control device 2 includes the power input circuit 10, the inverter circuit 20, the current detection part 30, the inverter input voltage detection part 41, a battery voltage detection part 42, the control part 50, and the like.

[0113] The battery voltage detection part 42 detects the battery voltage Vbat, which is the voltage of the battery 5, and outputs the detection value to the control part 50. Strictly speaking, the voltage detected by the battery voltage detection part 42 drops below the battery voltage Vbat in accordance with a current lig flowing in a wiring resistor 73. In the present embodiment, the current lig is assumed to be sufficiently small, and a voltage detected by the battery voltage detection part 42 is assumed to be the battery voltage Vbat. It should be noted that the battery voltage Vbat is a value normally detected in the motor control device 2 applied to the electric power steering device 8.

[0114] The control part 50 acquires a detection value corresponding to the battery voltage Vbat in addition to detection values corresponding to the phase currents Iu, Iv, Iw, the rotation angle θ, and the inverter input voltage Vinv. In the present embodiment, the control part 50 acquires the battery voltage Vbat, and the abnormality determination part 60 determines the power supply abnormality based on the voltage drop amount ΔV, which represents a difference between the battery voltage Vbat and the inverter input voltage Vinv.

[0115] The following describes the abnormality determination processing in the present embodiment with reference to the Fig. The flowchart shown in Figure 8 is described.

[0116] In S401, the abnormality determination part 60 reads the inverter input voltage Vinv and the battery voltage Vbat.

[0117] In S402, the abnormality determination part 60 determines whether the voltage drop amount ΔV exceeds the voltage drop amount threshold ΔV_th. If the voltage drop amount ΔV is determined not to exceed the voltage drop amount threshold ΔV_th (S402: NO), the inverter input voltage Vinv is deemed not to be below the voltage threshold Vinv_th, and processing proceeds to S406. If the voltage drop amount ΔV is determined to be above the voltage drop amount threshold ΔV_th (S402: YES), the inverter input voltage Vinv is deemed to be below the voltage threshold Vinv_th, and processing proceeds to S403.

[0118] The processing of S403 to S406 is the same as the processing of S103 to S106 in the Fig. 3.

[0119] The voltage drop amount threshold ΔV_th and the current threshold Ith1 are the same as those in the first embodiment (see, for example, equations (2), (10)). Furthermore, it can also be assumed that the current threshold Ith1 is determined in accordance with the voltage drop amount threshold ΔV_th, as can be seen from equation (10-1).

[0120] Further, like the first embodiment, instead of the current determination value Ij11, the current determination value Ij12 based on the dq-axis currents Id, Iq may be used.

[0121] In the case where the current determination value Ij11 is below the current threshold Ith1, if the voltage drop across the wiring resistance 70 is small and the power supply abnormality has not occurred, the voltage drop amount ΔV does not exceed the voltage drop amount threshold ΔV_th. In the present embodiment, if the voltage drop amount ΔV is above the voltage drop amount threshold ΔV_th and the current determination value Ij11 is below the current threshold Ith1, it can be determined that the voltage drop is not the voltage drop due to the increase in the drawn current, but the voltage drop due to the occurrence of the power supply abnormality. Therefore, the power supply abnormality can be appropriately determined.

[0122] Meanwhile, when the current determination value Ij11 is not less than the current threshold Ith1, the drawn current is high, causing an increase in the voltage drop across the wiring resistance 70. In such a case, the voltage drop amount ΔV may exceed the voltage drop amount threshold ΔV_th depending on the battery voltage Vbat. Therefore, in the present embodiment, when the current determination value Ij11 is not less than the current threshold Ith1, the current drawn from the battery 5 to the inverter circuit 20 is deemed to be outside the determinable range, and the power supply abnormality determination is not made, but the normality determination is made. Thus, the erroneous determination that the power supply abnormality has occurred when a voltage drop has occurred due to a large drawn current can be prevented.

[0123] The motor control device 2 further includes the battery voltage detecting part 42 which detects the battery voltage Vbat, which is the voltage of the battery 5.

[0124] When the voltage drop amount ΔV, which describes a difference between the battery voltage Vbat and the inverter input voltage Vinv, is above the voltage drop amount threshold ΔV_th, the abnormality determination part 60 assumes the inverter input voltage Vinv to be below the voltage threshold Vinv_th.

[0125] In this way, too, an effect similar to those in the above embodiments can be produced. (Fifth embodiment)

[0126] Fig. Fig. 9 shows a fifth embodiment of the present invention. In the present embodiment, the abnormality determination processing differs from that in the fourth embodiment, and therefore, a description will be given mainly with reference to it.

[0127] The following describes the abnormality determination processing in the present embodiment with reference to the Fig. The flowchart shown in Figure 9 is described.

[0128] The processing of S501 and S502 is the same as the processing of S401 and S402 in the Fig. 8.

[0129] The processing of S503 to S506 is the same as the processing of S203 to S206 in the Fig. 4.

[0130] The current threshold Ith2 is the same as that in the second embodiment (see equation (13)). Furthermore, it can also be assumed that the current threshold Ith2 is determined in accordance with the voltage drop amount threshold ΔV_th, as can be seen from equation (13-1).

[0131] Further, similarly to the second embodiment, instead of the current determination value Ij21, a current determination value Ij22 based on the product of the currents and voltages of the dq axes may be used.

[0132] In the case where the current determination value Ij21 is below the current threshold Ith2, when the voltage drop across the wiring resistance 70 is small and the power supply abnormality has not occurred, the voltage drop amount ΔV does not exceed the voltage drop amount threshold ΔV_th. In the present embodiment, when the voltage drop amount ΔV is above the voltage drop amount threshold ΔV_th and the current determination value Ij21 is below the current threshold Ith2, it can be determined that the voltage drop is not the voltage drop due to the increase in the drawn current, but the voltage drop due to the occurrence of the power supply abnormality. Therefore, the power supply abnormality can be appropriately determined.

[0133] Meanwhile, when the current determination value Ij21 is not less than the current threshold Ith2, the drawn current is high, causing an increase in the voltage drop across the wiring resistance 70. In such a case, the voltage drop amount ΔV may exceed the voltage drop amount threshold ΔV_th depending on the battery voltage Vbat. Therefore, in the present embodiment, when the current determination value Ij21 is not less than the current threshold Ith1 and the current drawn from the battery 5 to the inverter circuit 20 is deemed to be outside the determinable range, the power supply abnormality determination is not made, but the normality determination is made. Thus, the erroneous determination that the power supply abnormality has occurred when a voltage drop has occurred due to a large drawn current can be prevented.

[0134] In this way, too, an effect similar to that in the above embodiment can be produced. (Sixth Embodiment)

[0135] Fig. 10 shows a sixth embodiment of the present embodiment. In the present embodiment, the abnormality determination processing differs from that in the fourth embodiment, and therefore, a description will be given mainly with reference to it.

[0136] The processing of S601 and S602 is the same as the processing of S401 and S402 in the Fig. 8.

[0137] The processing of S603 to S606 is the same as the processing of S303 to S306 in the Fig. 3.

[0138] The rotation frequency threshold values Nth1, Nth2 are the same as those in the third embodiment.

[0139] In the present embodiment, when the rotation frequency N satisfies the determination condition, the battery current Ibat is below Ibat_th described above. For this reason, when the voltage drop across the wiring resistance 70 is small and the power supply abnormality has not occurred, the voltage drop amount ΔV does not exceed the voltage drop amount threshold ΔV_th. In the present embodiment, when the voltage drop amount ΔV is above the voltage drop amount threshold ΔV_th and the rotation frequency N satisfies the determination condition, it can be determined that the inverter input voltage Vinv has decreased not due to the voltage drop accompanied by the increase in the drawn current, but due to the occurrence of the power supply abnormality. Consequently, the power supply abnormality can be appropriately determined.

[0140] In contrast, when the rotation frequency N does not satisfy the determination condition, the drawn current is high, causing an increase in the voltage drop across the wiring resistance 70. In such a case, the voltage drop amount ΔV may exceed the voltage drop amount threshold ΔV_th depending on the battery voltage Vbat. Therefore, in the present embodiment, when the rotation frequency N does not satisfy the determination condition, the current drawn from the battery 5 to the inverter circuit 20 is deemed to be outside the determinable range, and the power supply abnormality determination is not made, but the normality determination is made. Thus, the erroneous determination that the power supply abnormality has occurred when a voltage drop has occurred due to a large drawn current can be avoided.

[0141] In this way, too, an effect similar to those in the above embodiments can be produced. (Seventh Embodiment)

[0142] Fig. 11 shows a seventh embodiment of the present invention.

[0143] The following describes the abnormality determination processing in the present embodiment with reference to the Fig. 11 is described. In S151, the abnormality determination part 60 reads the inverter input voltage Vinv and the battery voltage Vbat.

[0144] The processing of S152 and S153 is the same as the processing of S102 and S103 in the Fig. 3.

[0145] In S154, the abnormality determination part 60 calculates the current threshold Ith1 based on the battery voltage Vbat. Specifically, the battery voltage Vbat detected in S151 is used instead of the battery voltage lower limit Vbat_min of equation (2). The other derivation processes are the same as those in the above embodiments, with the current threshold Ith1 being determined to be no greater than the value on the left side of equation (10). The current threshold Ith1 can be determined by performing the above calculation using the battery voltage Vbat, as needed, or by preparing a map in advance in which the battery voltage Vbat is linked to the current threshold Ith1 and then performing a calculation based on the map.

[0146] It should be noted that the current threshold Ith1 can be calculated at any time from S151 to S155, such as the time before the determination processing of S152.

[0147] The processing of S155 to S157 is the same as the processing of S104 to S106.

[0148] In the present embodiment, the current threshold Ith1 is made variable (created or generated) in accordance with the battery voltage Vbat. When the battery voltage Vbat is above the battery voltage lower limit Vbat_min, the range in which the power supply abnormality can be determined can be broadened.

[0149] Although the example in which the current threshold Ith1 is made variable by the battery voltage Vbat is described above, the current threshold Ith2 or the rotation frequency thresholds Nth1, Nth2 may also be made variable based on the battery voltage Vbat in a similar manner.

[0150] In the present embodiment, the determination threshold is variable in accordance with the battery voltage Vbat, which describes the voltage of the battery 5.

[0151] Consequently, the determinable range can be appropriately determined in accordance with a change in the battery voltage Vbat.

[0152] Furthermore, an effect similar to those of the above embodiments can be produced. (Eighth Embodiment)

[0153] Fig. 12 shows an eighth embodiment of the present invention.

[0154] The following describes the abnormality determination processing in the present embodiment with reference to the Fig. The flowchart shown in Figure 12 is described.

[0155] The processing of S451 is the same as the processing of S401 in the Fig. 8.

[0156] In S452, the abnormality determination part 60 calculates the voltage drop amount threshold ΔV_th and the current threshold Ith1 based on the battery voltage Vbat.

[0157] The voltage drop amount threshold ΔV_th is calculated using the battery voltage Vbat detected in S451 instead of the battery voltage lower limit Vbat_min of equation (2). The calculation of the current threshold Ith1 is the same as that in the seventh embodiment. Note that the current threshold Ith1 can be calculated at any time from S451 to S455, such as the time after the YES determination in S453.

[0158] The processing of S453 to S457 is the same as the processing of S402 to S406.

[0159] In the present embodiment, the voltage drop amount threshold ΔV_th and the current threshold Ith1 are made variable in accordance with the battery voltage Vbat. When the battery voltage Vbat is above the battery voltage lower limit Vbat_min, the range in which the power supply abnormality can be determined can be broadened.

[0160] Although the example according to which the voltage drop amount threshold ΔV_th and the current threshold Ith1 of the fourth embodiment are made variable in accordance with the battery voltage Vbat is described above, the voltage drop amount threshold ΔV_th and the current threshold Ith2 of the fifth embodiment, as well as the voltage drop amount threshold ΔV_th and the rotation frequency thresholds Nth1, Nth2 of the sixth embodiment can also be made variable (generated or created) in accordance with the battery voltage Vbat in a similar manner.

[0161] Further, one of the voltage drop amount threshold ΔV_th and the determination threshold may be made variable in accordance with the battery voltage Vbat, and the other of them may be made as a setting value independent of the battery voltage Vbat.

[0162] In the present embodiment, the voltage drop amount threshold ΔV_th is made variable in accordance with the battery voltage Vbat. Consequently, the power supply abnormality determination can be made more appropriately in accordance with the battery voltage Vbat.

[0163] Furthermore, an effect similar to those in the above embodiments can be produced. (Ninth Embodiment)

[0164] Fig. 13 shows a ninth embodiment of the present embodiment.

[0165] As in Fig. 13, a motor 85 in the present embodiment is a direct current (DC) motor with a brush.

[0166] A motor control device 3 includes the power input circuit 10, an inverter circuit 120, a current detection part 35, the inverter input voltage detection part 41, the control part 50, and the like. It should be noted that, similar to the fourth embodiment and the like, the battery voltage detection part 42 may be provided in the motor control device 3.

[0167] The inverter circuit 120 is an H-bridge circuit and has four SW elements 121 to 124. One node of the paired SW elements 121, 123 is connected to one terminal 851 of a coil of the motor 85 (not shown). One node of the paired SW elements 122, 124 is connected to the other terminal 852 of the coil.

[0168] The current detection part 35 detects a winding current Imot, which is a current electrically supplied to the coil of the motor 85. The current detection part 35 of the present embodiment is a shunt resistor, and a voltage across both ends thereof is output to the control part 50 as a detection value in accordance with the winding current Imot.

[0169] The drive control part 55 of the control part 50 controls the drive of the motor 85 by controlling the on / off operation of the SW elements 121 to 124 based on the winding current Imot, the rotation angle θ, the steering torque or the like.

[0170] Instead of the current determination value Ij11 of the first embodiment or the fourth embodiment, the abnormality determination part 60 determines whether the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range based on a current determination value Ij13 to perform the power supply abnormality determination. The current determination value Ij13 in the case of the DC motor is the winding current Imot (see equation (14)). lj13=lmot

[0171] Furthermore, instead of the current determination value Ij21 of the second embodiment or the fifth embodiment, the abnormality determination part 60 may determine whether the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range based on a current determination value Ij23 to perform the power supply abnormality determination. The current determination value Ij23 in the case of the DC motor is the product of the winding current Imot and the voltage between both terminals and is described by equation (15). It should be noted that Vm1* in the equation is a voltage command value to be applied to the terminal 851, and Vm2* in the equation is a voltage command value to be applied to the terminal 852. lj23=(Vm1*−Vm2*)×lmot

[0172] Further, as in the third embodiment or the sixth embodiment, the abnormality determination part 60 may determine, based on the rotation frequency N, whether the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range to perform the power supply abnormality determination.

[0173] It should be noted that each threshold value in accordance with the power supply abnormality determination is the same as that in the above embodiment.

[0174] The motor 85 of the present embodiment is a DC motor. The current determination value Ij13 is the winding current Imot. Furthermore, the current determination value Ij23 is the product of a voltage between the terminals (ie, Vm1* - Vm2*) and the winding current Imot. Thus, in the DC motor, it can be appropriately determined whether the current drawn from the battery 5 to the inverter circuit 20 is within the determinable range.

[0175] Furthermore, an effect similar to those in the above embodiments can be produced. (Other embodiments)(I) Current determination value

[0176] In the first embodiment, the third embodiment, and the like, the current determination value is the square root of the sum of the squares of the phase current detection values. According to another embodiment, when calculating the current determination value, a command value or an estimated value may be used instead of the phase current detection value. This also applies to the d-axis current and the q-axis current.

[0177] In the second embodiment, the fourth embodiment, and the like, when calculating the current determination value, the detection value is used as the current value, and the command value is used as the voltage value. According to another embodiment, when calculating the current determination value, the command value or the estimated value may be used as the current value, and the detection value or the estimated value may be used as the voltage value.

[0178] As in the case of the DC motor, any of the detection value, the command value, and the estimation value can be used as the motor current and the voltage between the terminals. (II) Speed

[0179] In the third embodiment and the sixth embodiment, the rotational frequency calculated based on the rotational angle corresponds to the rotational speed. According to another embodiment, a rotational angular velocity may be used as the rotational speed instead of the rotational frequency. Further, according to another embodiment, a terminal voltage detection part may be provided for detecting a terminal voltage of each phase, and the rotational speed may be estimated based on the detected terminal voltage. (III) Determinable range

[0180] In the above embodiment, the current determination value and the rotational speed are used to determine the determinable range. According to another embodiment, a value used to determine the determinable range can be any value as long as it is a value corresponding to the motor current or the rotational speed. Furthermore, the determination threshold value can be appropriately determined in accordance with a value used for the determination, as long as the inverter input voltage at the time when the power supply abnormality has not occurred is a value not lower than the voltage threshold value. (IV) Current detection part

[0181] In the above embodiments, the shunt resistor is used for the current detection part and is arranged on the low potential side of the low-potential side SW element. In another embodiment, a Hall element or the like other than the shunt resistor may be used for the current detection part. Furthermore, the location where the current detection part is provided is not limited to the low potential side of the low-potential side SW element; the current detection part may be provided in any location where a current can be detected. (V) Engine

[0182] The motor in the above embodiments is a three-phase motor or a direct current motor. In another embodiment, the motor can be any motor, such as a motor with four or more phases.

[0183] In the above embodiments, the motor is applied to the electric power steering device. In another embodiment, the motor control device may be applied to a device other than the electric power steering device.

[0184] It is noted that a flowchart or the processing of the flowchart in the present application comprises sections (also referred to as steps), each denoted, for example, as S101. Furthermore, each section may be divided into multiple subsections, while multiple sections may be combined into a single section. Furthermore, each of the thus-configured sections may also be referred to as a device, a module, or a means.

Claims

[1] Motor control device for controlling a drive of a motor (80, 85), comprising: - an inverter circuit (20, 120) which supplies energy from a battery (5) to the motor; - an inverter input voltage detector (41) which detects an inverter input voltage to be applied to the inverter circuit; and - a controller (50) comprising: - a drive controller (55) for controlling the drive of the motor; and - an abnormality determination unit (60) for determining a power supply abnormality in that the power is not supplied from the battery to the inverter circuit in a power supply area between the battery and the inverter circuit, wherein - the abnormality determination unit determines that the power supply abnormality occurs when the inverter input voltage is below a voltage threshold and a current from the battery to the inverter circuit is within a determinable range, - the abnormality determination unit determines whether the current is within the determinable range based on a motor current electrically supplied to the motor or a rotational speed of the motor, - a determination threshold is determined in accordance with the determinable range such that the inverter input voltage is greater than or equal to the voltage threshold when the power supply range is normal, - the abnormality determination unit determines that the current from the battery to the inverter circuit is within the determinable range when a current determination value calculated using the motor current is below a current threshold as the determination threshold, and - the abnormality determination unit determines that a voltage drop occurs due to a line resistance and the power supply is normal without determining the power supply abnormality when the inverter input voltage is below the voltage threshold and the current determination value calculated using the motor current is not below the current threshold. [2] Engine control device according to claim 1, wherein - the motor is a three-phase motor (80); and - the current determination value is a square root of a sum of squares of a phase current or a dq-axis current. [3] Engine control device according to claim 1, wherein - the motor is a three-phase motor (80); and - the current determination value is a sum of values obtained by multiplying a current value and a voltage value of each phase or each dq axis. [4] Engine control device according to claim 1, wherein - the motor is a DC motor (85); and - the current determination value is a winding current flowing in a coil of the motor or a product of a voltage between terminals and the winding current. [5] Motor control device for controlling a drive of a motor (80, 85), comprising: - an inverter circuit (20, 120) which supplies energy from a battery (5) to the motor; - an inverter input voltage detector (41) which detects an inverter input voltage to be applied to the inverter circuit; and - a controller (50) comprising: - a drive controller (55) for controlling the drive of the motor; and - an abnormality determination unit (60) for determining a power supply abnormality in that the power is not supplied from the battery to the inverter circuit in a power supply area between the battery and the inverter circuit, wherein - the abnormality determination unit determines that the power supply abnormality occurs when the inverter input voltage is below a voltage threshold and a current from the battery to the inverter circuit is within a determinable range, - the abnormality determination unit determines whether the current is within the determinable range based on a motor current electrically supplied to the motor or a rotational speed of the motor, - a determination threshold is determined in accordance with the determinable range such that the inverter input voltage is greater than or equal to the voltage threshold when the power supply range is normal, - the determination threshold is a first speed threshold and a second speed threshold which is greater than the first speed threshold, and - the abnormality determination unit determines that the current from the battery to the inverter circuit is in the determinable range when the speed is below the first speed threshold or above the second speed threshold. [6] The engine control device according to any one of claims 1 to 5, further comprising a battery voltage detector (42) that detects a battery voltage of the battery, wherein - the abnormality determination unit determines that the inverter input voltage is below the voltage threshold when a voltage drop amount is above a voltage drop amount threshold; and - the voltage drop amount describes a difference between the battery voltage and the inverter input voltage. [7] The motor control device according to claim 6, wherein the voltage drop amount threshold is variable in accordance with the battery voltage. [8] The engine control device according to any one of claims 1 to 7, wherein the determination threshold is variable in accordance with a battery voltage of the battery. [9] Electric power steering device with: - the engine control device (1, 2, 3) according to one of claims 1 to 8; and - the motor that provides auxiliary torque to assist a driver's steering operation.

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