Motor control device, motor control method, and electric power steering device

Abstract

To provide a motor control device, a motor control method, and an electric power steering device capable of suppressing unnecessary current limitation while continuing temperature-dependent current limitation, even when an abnormality occurs in a temperature sensor that detects the temperature of a substrate on which a drive element of a motor is mounted.SOLUTION: According to one embodiment of the present invention, a motor control device calculates a temperature change amount of a drive element from an actual current value of a motor, executes first current limitation control that limits a target current value on the basis of a temperature detection value and the temperature change amount when the temperature sensor is in a normal state, executes second current limitation control that limits the target current value from the temperature change amount lower than the time of the first current limitation control on the basis of the temperature change amount when the temperature sensor is in an abnormal state, and resets the temperature change amount used for current limitation in the second current limitation control such that the current limitation state by the first current limitation control before switching is maintained when switching from the first current limitation control to the second current limitation control on the basis of the abnormality occurrence in the temperature sensor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a motor control device, a motor control method, and an electric power steering device. [Background technology]

[0002] The electric power steering device of Patent Document 1 is equipped with a temperature estimation calculation means for estimating the temperature of the heating element, and a temperature sensor failure detection means for detecting failure of the temperature sensor of the heating element, and if the temperature sensor fails, the motor current is limited based on the estimated temperature instead of the detected temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-044437 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when an abnormality occurs in the temperature sensor and the accuracy of the temperature estimation decreases, the effect of preventing overheating can be more reliably achieved by switching to implement current limiting from a lower temperature. However, if the start temperature of current limitation is changed to a lower temperature due to an abnormality in the temperature sensor, unnecessary current limitation may be implemented, which may cause a change in the steering feel of the driver, for example, in the case of an electric power steering device.

[0005] The present invention has been made in consideration of the conventional situation, and its object is to provide a motor control device, a motor control method, and an electric power steering device that are capable of suppressing unnecessary current limiting while continuing current limiting according to temperature even if an abnormality occurs in the temperature sensor. [Means for solving the problem]

[0006] According to the present invention, in one aspect, a temperature change amount of a drive element that drives a motor is obtained from an actual current value flowing through the motor, and when a temperature sensor that detects the temperature of a substrate on which the drive element is mounted is normal, a first current limiting control is performed to limit a target current value supplied to the motor based on a temperature detection value by the temperature sensor and the temperature change amount, and when the temperature sensor is abnormal, a second current limiting control is performed to limit a target current value supplied to the motor based on the temperature change amount from a temperature change amount that is lower than that during the first current limiting control, and when switching from the first current limiting control to the second current limiting control based on the occurrence of an abnormality in the temperature sensor, the temperature change amount used for current limiting in the second current limiting control is reset so that the current limiting state by the first current limiting control before switching is maintained. Effect of the Invention

[0007] According to the present invention, even if an abnormality occurs in the temperature sensor, it is possible to continue current limiting according to the temperature and prevent unnecessary current limiting. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an electric power steering device. [Diagram 2] FIG. 4 is a block diagram showing a calculation logic for a current limiting rate. [Diagram 3] 4 is a block diagram showing a configuration of a temperature change amount calculation unit. FIG. [Figure 4] FIG. 13 is a block diagram showing a configuration of a resetting unit. [Diagram 5] 11 is a diagram illustrating a correlation between estimated temperature TDE and current limit rate CLR1. [Figure 6] 11 is a diagram illustrating an example of a correlation between a temperature change amount ΔT and a current limiting rate CLR2. [Figure 7] 11 is a diagram illustrating an example of a correlation between a temperature change amount ΔT and a current limiting rate CLR3. [Figure 8] 1 is a diagram showing characteristics for converting a current limit rate CLR into a temperature change amount ΔTCLR. [Figure 9]11 is a diagram showing a manner in which a current limiting rate CLR changes when a reset function is not provided. FIG. [Figure 10] FIG. 13 is a diagram showing a manner in which the temperature change amount ΔT is reset. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a motor control device, a motor control method, and an electric power steering device according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an electric power steering device 200 as an application example of a motor control device and a motor control method according to the present invention.

[0010] Electric power steering device 200 attached to vehicle 100 includes a motor 220 that applies a steering force to steering mechanism 210, and a motor control device 230 as a control unit that controls motor 220 (in other words, a control unit that implements a motor control method). The motor control device 230 has a function to control the motor drive current in response to the required value of the steering force, and a function to limit the motor drive current based on an estimated temperature of the drive element of the motor 220.

[0011] The steering mechanism 210 of the electric power steering device 200 has, as its basic components, a steering wheel 201 as a steering member (in other words, a steering operation input member operated by the driver of the vehicle 100), a pinion shaft 203 that is provided at the end of a steering shaft 202 that is a rotating shaft and operates in response to the rotation of the steering shaft 202, a rack bar 204, and a rack housing 205 that accommodates the rack bar 204. In the steering mechanism 210 , when the driver of the vehicle 100 turns the steering wheel 201 , the steering torque of the steering wheel 201 is transmitted to the pinion shaft 203 via the steering shaft 202 .

[0012] The rotational motion of the pinion shaft 203 is converted into linear motion of the rack bar 204, whereby the tire angles of the left and right wheels 110, 110 connected to both ends of the rack bar 204 via tie rods 250 are changed. In other words, the rotational motion of the steering shaft 202 is converted into linear motion of the rack bar 204 by a rack-and-pinion system in which the pinion shaft 203 meshes with rack teeth formed on the rack bar 204, thereby changing the tire angle of the wheels 110, 110.

[0013] The steering shaft 202 is provided with a steering angle sensor 206A that detects a steering angle β, which is a rotation angle of the steering shaft 202, and a steering torque sensor 206B that detects a steering torque TS of the steering wheel 201. Steering angle sensor 206A detects steering angle β as 0 [deg] when steering wheel 201 is in the neutral position, and distinguishes the left and right steering directions from the neutral position by positive or negative signs.

[0014] In addition, the steering mechanism 210 includes a motor 220 that applies torque (steering force) to the rack bar 204. The rotational motion of the motor 220 is transmitted to the rack bar 204 via a transmission mechanism 208 including a belt, a ball screw, or the like. The application of the steering force by the motor 220 is performed to assist the steering force of the driver or for autonomous steering (in other words, automatic steering).

[0015] The motor 220 is a three-phase brushless DC motor having a stator coil including a U-phase, a V-phase, and a W-phase, and a motor rotor. The motor control device 230 includes a microcomputer 231 and a drive circuit 232 for the motor 220 , and the microcomputer 231 and the drive circuit 232 are mounted on a circuit board 233 . The drive circuit 232 includes a three-phase bridge inverter made up of six semiconductor switching elements, and controls the power supplied to the stator coil of the motor 220 by controlling the on / off of the semiconductor switching elements.

[0016] Alternatively, the motor 220 may have two winding sets, and may be a redundant drive system having two independent drive systems for driving and controlling the energization of each winding set. Here, each of the two driving systems includes a microcomputer 231 and a driving circuit 232 as a pair.

[0017] The microcomputer 231 acquires various sensor signals for use in controlling the motor 220, in other words, in controlling the steering force. In detail, the microcomputer 231 acquires a signal relating to the steering angle β (steering operation amount) of the steering wheel 201 outputted from the steering angle sensor 206A, a signal relating to the steering torque TS outputted from the steering torque sensor 206B, a signal relating to the vehicle speed VS outputted from the vehicle speed sensor 207 (or the wheel speed sensor), and further a signal relating to the rotor rotation angle θ of the motor 220 outputted from the motor rotation angle sensor 209.

[0018] Then, the microcomputer 231 determines a command torque (target steering force) which is a target value of the torque (steering force) output by the motor 220, based on information such as the steering torque TS, the vehicle speed VS, and the steering angle β. The microcomputer 231 controls the drive current of the motor 220 by controlling the on / off of each semiconductor switching element constituting an inverter included in the drive circuit 232 using PWM (Pulse Width Modulation) based on the command torque.

[0019] In addition, the microcomputer 231 has an overheat protection function that limits the motor drive current to a predetermined maximum current value (upper limit value) or less in response to a rise in temperature of the motor drive elements, such as each semiconductor switching element of the inverter, in order to prevent the motor drive elements from being damaged due to a temperature exceeding their heat-resistant temperature. For the purpose of overheat protection, a temperature sensor 234 is provided for detecting a temperature TB of a circuit board 233 on which a drive circuit 232 (that is, a motor drive element to be protected) is mounted. Then, the microcomputer 231 acquires a signal of the substrate temperature TB and a signal of the motor drive current value output by the temperature sensor 234, and calculates a current limit rate [%] used to limit the motor drive current.

[0020] In detail, the microcomputer 231 estimates the temperature change amount ΔT of the motor driving element that constitutes the driving circuit 232 from the signal of the motor driving current value, and calculates the current limiting rate [%] that makes the maximum current value variable based on the temperature change amount ΔT and the substrate temperature TB. In other words, the substrate temperature TB correlates with the temperature of the motor driving element when no current is passing through the motor driving element, and when current is passed through the motor driving element, the temperature of the motor driving element rises from a base temperature corresponding to the substrate temperature TB.

[0021] Therefore, the microcomputer 231 estimates the base temperature of the motor driving element based on the substrate temperature TB detected by the temperature sensor 234, and further estimates the temperature rise from the base temperature due to motor current flow as a temperature change amount ΔT based on the motor driving current value. Then, the microcomputer 231 obtains the temperature of the motor driving element by adding the temperature change amount ΔT (temperature increase) to the base temperature. Furthermore, the microcomputer 231 calculates a current limit rate CLR [%] based on the temperature of the motor driving element, and limits the upper limit of the motor driving current based on the current limit rate CLR, thereby preventing the motor driving element from overheating.

[0022] The current limit rate CLR is a parameter that is set so as to reduce the upper limit of the current flowing through the motor driving element as the temperature of the motor driving element increases. In other words, when the current limit rate CLR is 100%, the reference maximum current value (reference upper limit current value) is used as is for upper limit limiting the motor drive current, and the smaller the current limit rate CLR is below 100%, the smaller the maximum current value used for upper limit limiting the motor drive current is changed to. In the present application, a state in which the current limit rate CLR is set to less than 100% is referred to as a temperature-based current limit state, and the temperature at which the current limit rate CLR starts to change to less than 100% is referred to as a limit start temperature.

[0023] For example, if the reference maximum current value is 100A, when the current limit rate CLR is 100%, the motor drive current is limited to 100A or less, and when the current limit rate CLR is 80%, the motor drive current is limited to 80A or less. When the current limit rate CLR is 0%, the maximum current value is set to 0 A, and therefore the motor drive is stopped.

[0024] Basically, the microcomputer 231 changes the maximum current value to a smaller current value by setting a smaller current limiting rate CLR as the temperature of the motor driving element increases, and by limiting the current value flowing through the motor driving element to a smaller value as the temperature of the motor driving element increases, thereby preventing overheating of the motor 220. Here, the microcomputer 231 is configured to be able to deal with the occurrence of an abnormality in the temperature sensor 234 in the calculation of the current limiting rate CLR. The presence or absence of an abnormality in temperature sensor 234 is diagnosed by various known methods. For example, temperature sensor 234 is diagnosed as normal or abnormal based on whether the output voltage thereof is within a predetermined range.

[0025] As a function for dealing with the occurrence of an abnormality in the temperature sensor 234, the microcomputer 231 has a function of calculating the current limit rate CLR based on the motor drive current value without using information on the substrate temperature TB when it detects the occurrence of an abnormality (fault) in the temperature sensor 234 based on a diagnostic signal indicating whether the temperature sensor 234 is normal or abnormal. Furthermore, the microcomputer 231 has a function of switching the correlation between the temperature change amount ΔT and the current limit rate CLR depending on whether the temperature sensor 234 is normal or abnormal in the process of calculating the current limit rate CLR from the temperature change amount ΔT.

[0026] In other words, the microcomputer 231 has a first current limiting section that limits the current of the motor 220 based on the substrate temperature TB detected by the temperature sensor 234 and a temperature change amount ΔT when the temperature sensor 234 is normal, and a second current limiting section that limits the current of the motor 220 based on the temperature change amount ΔT when the temperature sensor 234 is abnormal, and limits the current of the motor 220 from a temperature change amount ΔT that is lower than that of the first current limiting section, and switches from the first current limiting section to the second current limiting section based on the occurrence of an abnormality in the temperature sensor 234.

[0027] 2 to 4 are block diagrams showing an embodiment of the calculation logic for the current limit rate CLR [%], including a function for dealing with the occurrence of an abnormality in the temperature sensor 234. The first-order lag processor 310 (see FIG. 2) is an infinite impulse response (IIR) digital filter that is composed of three elements: a delay element, coefficients K1 and K2, and an adder, and has a feedback loop from the output to the input.

[0028] Then, the first-order lag processing unit 310 acquires the signal of temperature TB of the circuit board 233 output by the temperature sensor 234, and applies first-order lag processing to the acquired signal of temperature TB to approximate the temperature change characteristics of the motor driving element mounted on the circuit board 233. In other words, the signal of temperature TB that has been subjected to primary delay processing and that is output by primary delay processor 310 becomes a base temperature signal that correlates with the temperature of the motor driving element when no current is applied to the motor driving element.

[0029] The temperature change amount calculation unit 320 (see Figure 3) is a temperature change amount estimation unit that acquires a signal of the drive current value of the motor 220 and calculates the temperature change amount ΔT of the motor drive element from the motor drive current value, in other words, the temperature rise from the base temperature due to current flow. Here, the temperature change amount calculation unit 320 includes a current squared integrated value calculation unit 321 , a conversion unit 322 , a first-order lag processing unit 323 , a first switching unit 324 , and a switching request generation unit 325 .

[0030] The current squared integrated value calculation unit 321 obtains signals of the q-axis current value Iq and the d-axis current value Id in the vector control of the motor 220 as signals of the motor drive current value, and calculates a current squared integrated value. The conversion unit 322 converts the current squared integrated value calculated by the current squared integrated value calculation unit 321 into a temperature change amount ΔT based on a predetermined conversion coefficient. In other words, the temperature change amount ΔT is an estimate of the temperature change of the motor driving element according to the current squared integrated value.

[0031] The first-order lag processor 323 is an infinite impulse response (IIR) digital filter that is composed of three elements: a delay element, coefficients K3 and K4, and an adder. Then, first-order lag processor 323 performs first-order lag processing on the temperature change amount ΔT found by converter 322 to approximate the temperature rise characteristics of the motor driving element due to the motor driving current.

[0032] The first switching unit 324 selects and outputs either the signal of the temperature change amount ΔT that has been subjected to first-order delay processing by the first-order delay processing unit 323 or the signal of the temperature change amount ΔTR that is output from the resetting unit 400 described later, in accordance with the output of the switching request generating unit 325. The output of the first switching unit 324 is fed back as an input to the first-order lag processing unit 323 .

[0033] The switching request generating unit 325 acquires a fault diagnosis signal indicating whether the temperature sensor 234 is normal or abnormal, and outputs a switching request signal to the first switching unit 324 to instruct the selection of the temperature change amount ΔTR the first time the temperature sensor 234 switches from a normal state to an abnormal state. That is, when the temperature sensor 234 is normal, the first switching unit 324 outputs the output of the first-order lag processing unit 323 as a signal of the temperature change amount ΔT.

[0034] On the other hand, the first time that the temperature sensor 234 becomes abnormal, the first switching unit 324 outputs the signal of the temperature change amount ΔTR output from the resetting unit 400 as a signal of the temperature change amount ΔT. Thereafter, the first switching unit 324 returns to a state in which it outputs the output of the first-order lag processing unit 323 as a signal of the temperature change amount ΔT, and the first-order lag processing unit 323 performs first-order lag processing using the fed-back temperature change amount ΔTR as the initial value.

[0035] The estimated temperature calculation unit 330 (see FIG. 2) acquires the signal of the substrate temperature TB output by the first-order lag processing unit 310, i.e., the signal of the base temperature of the motor driving element, and the signal of the temperature change amount ΔT output by the temperature change amount calculation unit 320 (see FIG. 3). Then, the estimated temperature calculation section 330 adds the temperature change amount ΔT and a predetermined offset temperature to the signal of the temperature TB to obtain the estimated temperature TDE [° C.] of the motor driving element. That is, the estimated temperature calculation section 330 estimates the temperature of the motor driving element based on the substrate temperature TB detected by the temperature sensor 234 and the amount of temperature change ΔT.

[0036] The first current limiting rate setting unit 340 (see FIG. 2) calculates the current limiting rate CLR1 based on the estimated temperature TDE obtained by the estimated temperature calculation unit 330. FIG. 5 is a diagram illustrating the correlation between the estimated temperature TDE and the current limit rate CLR1 in the first current limit rate setting unit 340 (a conversion map for obtaining the current limit rate CLR1 from the estimated temperature TDE).

[0037] The current limit rate CLR1 is maintained at 100% while the estimated temperature TDE ranges from 0°C to the first threshold value T1 [°C] (T1 > 0°C), decreases at a constant gradient from 100% to 0% while the estimated temperature TDE rises from the first threshold value T1 to the second threshold value T2 [°C] (T1 < T2), and is set to 0% when the estimated temperature TDE is equal to or higher than the second threshold value T2. That is, when the estimated temperature TDE rises to the first threshold value T1, the current limit of the motor 220 is started, and when the estimated temperature TDE becomes equal to or higher than the second threshold value T2, the energization of the motor 220 is stopped, as set for the current limit rate CLR1.

[0038] For example, the first threshold value T1 is set to about 150°C to 160°C, and the second threshold value T2 is set to a temperature about 5°C to 10°C higher than the first threshold value T1. Here, the first threshold value T1 is the limit start temperature at which the limitation of the motor drive current is started according to the temperature of the motor drive element by setting the current limit rate CLR1 by the first current limit rate setting unit 340.

[0039] Also, the second current limit rate setting unit 350 (see FIG. 2) acquires the signal of the temperature change amount ΔT output by the temperature change amount calculation unit 320 (see FIG. 3), and calculates the current limit rate CLR2 based on the temperature change amount ΔT. FIG. 6 is a diagram illustrating the correlation (conversion map for obtaining the current limit rate CLR2 from the temperature change amount ΔT) between the temperature change amount ΔT (in other words, the temperature rise due to motor energization) and the current limit rate CLR2 in the second current limit rate setting unit 350. The current limit rate CLR2 is maintained at 100% while the temperature change amount ΔT ranges from 0°C to the third threshold value T3 [°C] (T1 > 0°C), decreases at a constant gradient from 100% to 0% while the temperature change amount ΔT rises from the third threshold value T3 to the fourth threshold value T4 [°C] (T3 < T4), and is set to 0% when the temperature change amount ΔT is equal to or higher than the fourth threshold value T4.

[0040] Note that the third threshold value T3 is a temperature lower than the first threshold value T1. For example, the third threshold value T3 is set to about 40°C to 50°C, and the fourth threshold value T4 is set to a temperature about 5°C to 10°C higher than the third threshold value T3. Here, the third threshold value T3 is the limit start temperature at which the limitation of the motor drive current is started by the setting of the current limitation rate CLR2 by the second current limitation rate setting unit 350.

[0041] Also, the third current limitation rate setting unit 360 (see FIG. 2) acquires the signal of the temperature change amount ΔT output by the temperature change amount calculation unit 320 in the same manner as the second current limitation rate setting unit 350, and calculates the current limitation rate CLR3 based on the temperature change amount ΔT. Here, the correlation between the temperature change amount ΔT and the current limitation rate CLR2 in the second current limitation rate setting unit 350 is adapted on the premise that the temperature sensor 234 is abnormal and the calculation of the estimated temperature TDE in the estimated temperature calculation unit 330 and the calculation of the current limitation rate CLR1 in the first current limitation rate setting unit 340 cannot be normally performed.

[0042] FIG. 7 is a diagram illustrating the correlation (conversion map for obtaining the current limitation rate CLR3 from the temperature change amount ΔT) between the temperature change amount ΔT (in other words, the temperature rise due to motor energization) and the current limitation rate CLR3 in the third current limitation rate setting unit 360. The current limitation rate CLR3 is maintained at 100% while the temperature change amount ΔT is between 0°C and the fifth threshold value T5 [°C] (T5 > 0°C), decreases at a constant gradient from 100% to 0% while the temperature change amount ΔT rises from the fifth threshold value T5 to the sixth threshold value T6 [°C] (T5 < T6), and is set to 0% when the temperature change amount ΔT is equal to or higher than the sixth threshold value T6. Note that the fifth threshold value T5 is a temperature lower than the third threshold value T3. For example, the fifth threshold value T5 is set to about 10°C, and the sixth threshold value T6 is set to a temperature about 10°C to 20°C higher than the fifth threshold value T5. Here, the fifth threshold value T5 is the limit start temperature at which the limitation of the motor drive current is started by the setting of the current limitation rate CLR3 by the third current limitation rate setting unit 360.

[0043] The second switching unit 370 (see FIG. 2) selects either the current limiting rate CLR2 output by the second current limiting rate setting unit 350 or the current limiting rate CLR3 output by the third current limiting rate setting unit 360 based on a fault diagnosis signal indicating whether the temperature sensor 234 is normal or abnormal, and outputs the selected current limiting rate as the current limiting rate CLRT based on the amount of temperature change. In detail, if the temperature sensor 234 is normal, the second switching unit 370 outputs the current limiting rate CLR2 set by the second current limiting rate setting unit 350 as the current limiting rate CLRT, and if the temperature sensor 234 is abnormal, the second switching unit 370 outputs the current limiting rate CLR3 set by the third current limiting rate setting unit 360 as the current limiting rate CLRT.

[0044] The comparison unit 380 (see FIG. 2) compares the current limiting rate CLR1 based on the estimated temperature TDE output by the first current limiting rate setting unit 340 with the current limiting rate CLRT based on the temperature change amount ΔT output by the second switching unit 370, and outputs the smaller of the current limiting rate CLR1 and the current limiting rate CLRT, i.e., the one which changes the maximum current value lower, as the current limiting rate CLRmin. Therefore, when the temperature sensor 234 is normal, the comparison unit 380 outputs the smaller of the current limiting rate CLR1 based on the estimated temperature TDE and the current limiting rate CLR2 set by the second current limiting rate setting unit 350 as the current limiting rate CLRmin. Furthermore, when the temperature sensor 234 is abnormal, the comparison unit 380 outputs the smaller of the current limiting rate CLR1 based on the estimated temperature TDE and the current limiting rate CLR3 set by the third current limiting rate setting unit 360 as the current limiting rate CLRmin.

[0045] The third switching unit 390 (see FIG. 2) selects either the current limiting rate CLRmin output by the comparison unit 380 or the current limiting rate CLRT based on the amount of temperature change ΔT output by the second switching unit 370 depending on whether the temperature sensor 234 is normal or abnormal, and outputs it as the final current limiting rate CLR. In detail, when the temperature sensor 234 is normal, the third switching section 390 selects the current limiting rate CLRmin output by the comparison section 380 and outputs it as the final current limiting rate CLR. On the other hand, when the temperature sensor 234 is abnormal, the third switching unit 390 selects the current limiting rate CLRT based on the temperature change amount ΔT output by the second switching unit 370, that is, the current limiting rate CLR3 set by the third current limiting rate setting unit 360, and outputs it as the final current limiting rate CLR.

[0046] In the above configuration, the first-order lag processing unit 310, the estimated temperature calculation unit 330, the first current limiting rate setting unit 340, the second current limiting rate setting unit 350, and the comparison unit 380 constitute a first current limiting unit that limits the drive current of the motor 220 based on the detection value of the substrate temperature TB by the temperature sensor 234 and the amount of temperature change ΔT when the temperature sensor 234 is normal. Further, the third current limiting rate setting unit 360, the second switching unit 370, and the third switching unit 390 constitute a current limiting unit that limits the current of the motor 220 based on the temperature change amount ΔT when the temperature sensor 234 is abnormal, and constitute a second current limiting unit that limits the current of the motor 220 from a temperature change amount ΔT that is lower than that of the first current limiting unit.

[0047] On the other hand, the resetting unit 400 (see FIG. 4) acquires a signal of the temperature change amount ΔT output by the temperature change amount calculation unit 320, a signal of the estimated temperature TDE of the motor driving element output by the estimated temperature calculation unit 330, and a signal of the current limiting rate CLR output by the third switching unit 390. Then, the resetting section 400 outputs a signal of the temperature change amount ΔTR to the first switching section 324 of the temperature change amount calculation section 320.

[0048] The temperature change amount ΔTR is a value used to reset the temperature change amount ΔT the first time the temperature sensor 234 becomes abnormal. In other words, the first time that the temperature sensor 234 becomes abnormal, the temperature change amount ΔTR output by the resetting unit 400 is output to the estimated temperature calculation unit 330, the second current limiting rate setting unit 350, and the third current limiting rate setting unit 360, instead of the temperature change amount ΔT output by the temperature change amount calculation unit 320.

[0049] The resetting section 400 includes a temperature shift correction section 410 . The temperature shift correction section 410 has a first temperature deviation calculation section 411 , a second temperature deviation calculation section 412 , a comparison section 413 , a third temperature deviation calculation section 414 , and a lower limit section 415 . The first temperature deviation calculation unit 411 calculates a first temperature deviation DT1 (DT1 = third threshold T3 - ΔT), which is the difference between the temperature change ΔT output by the temperature change amount calculation unit 320 and the third threshold T3, which is the start temperature of current limiting in the second current limiting rate setting unit 350. In addition, the second temperature deviation calculation unit 412 calculates a second temperature deviation DT2 (DT2 = T1 - TDE), which is the difference between the estimated temperature TDE of the motor driving element output by the estimated temperature calculation unit 330 and the first threshold value T1, which is the start temperature of current limiting in the first current limiting rate setting unit 340.

[0050] The comparison section 413 selects the smaller one of the first temperature deviation DT1 calculated by the first temperature deviation calculation section 411 and the second temperature deviation DT2 calculated by the second temperature deviation calculation section 412, and outputs it as the temperature deviation DTmin. Then, the third temperature deviation calculation unit 414 calculates a third temperature deviation DT3 (DT3 = fifth threshold T5 - DTmin), which is the difference between the temperature deviation DTmin signal output by the comparison unit 413 and the fifth threshold T5, which is the start temperature of current limiting in the third current limiting rate setting unit 360.

[0051] The lower limit limiting unit 415 compares the third temperature deviation DT3 output by the third temperature deviation calculating unit 414 with 0° C., which is a predetermined lower limit, and outputs the larger one as the temperature deviation DT. In other words, when the third temperature deviation DT3 is a negative value, the lower limit unit 415 sets the temperature deviation DT to 0°C, and when the third temperature deviation DT3 is 0°C or higher, the lower limit unit 415 outputs the value of the third temperature deviation DT3 as is as the temperature deviation DT. In other words, the lower limit unit 415 limits the temperature change amount ΔTR for resetting based on the difference between the first threshold T1, the third threshold T3 (first restriction start temperature), which are the temperatures at which current limiting begins when the temperature sensor 234 is in a normal state, and the fifth threshold T5 (second restriction start temperature), which is the temperature at which current limiting begins when the temperature sensor 234 is in an abnormal state, so that the temperature change amount ΔTR does not fall below a specified temperature (for example, 0°C).

[0052] Moreover, the resetting section 400 has a conversion section 420 , a comparison section 430 , a switching section 440 , and a delay section 450 in addition to the temperature shift correction section 410 . The conversion unit 420 determines the temperature change ΔT corresponding to the current limiting rate CLR output by the third switching unit 390 in the correlation between the temperature change ΔT in the third current limiting rate setting unit 360 and the current limiting rate CLR3, and outputs it as the temperature change ΔTCLR.

[0053] FIG. 8 is a diagram showing the characteristics (conversion map) of the conversion unit 420 for converting the current limit rate CLR into the temperature change amount ΔTCLR. That is, when the current limit rate CLR is 100%, the conversion unit 420 sets the temperature change amount ΔTCLR to the temperature of the fifth threshold T5, and when the current limit rate CLR is 0%, the conversion unit 420 sets the temperature change amount ΔTCLR to the temperature of the sixth threshold T6. Furthermore, when the current limiting rate CLR is between 100% and 0%, the conversion unit 420 increases the temperature change amount ΔT from the fifth threshold value T5 to the sixth threshold value T6 at a constant gradient in response to a decrease in the current limiting rate CLR.

[0054] The comparison unit 430 compares the current limiting rate CLR output by the third switching unit 390 with 100% to determine whether the current limiting rate CLR is in a limited state where the maximum current value is changed to a value smaller than a reference value, or a non-limited state where the maximum current value remains at the reference value due to the current limiting rate CLR, and outputs a signal indicating whether the current limiting rate CLR is in a limited state or a non-limited state. In other words, the comparison unit 430 determines that the current limiting rate CLR output by the third switching unit 390 is 100% (CLR=100%), and determines that the current limiting rate CLR is limited, if the current limiting rate CLR output by the third switching unit 390 is less than 100% (CLR<100%).

[0055] The switching unit 440 selects either the temperature deviation DT output by the lower limit unit 415 of the temperature shift correction unit 410 or the temperature change amount ΔTCLR output by the conversion unit 420 based on the discrimination signal of the restricted state or the non-restricted state output by the comparison unit 430, and outputs it as the temperature change amount ΔTR1. Here, in the case of the restricted state, the switching unit 440 selects the temperature change amount ΔTCLR output by the conversion unit 420, and sets the value of the temperature change amount ΔTCLR as the temperature change amount ΔTR1 and outputs it.

[0056] On the other hand, when in the non-restricted state, the switching unit 440 selects the temperature deviation DT output by the temperature shift correction unit 410, sets the value of the temperature deviation DT as the amount of temperature change ΔTR1, and outputs it. Then, the delay section 450 delays the temperature change amount ΔTR 1 output by the switching section 440 , and outputs the delayed amount to the first switching section 324 of the temperature change amount calculation section 320 .

[0057] The first switching unit 324 outputs the temperature change amount ΔTR output from the resetting unit 400 (delay unit 450) instead of the output from the first-order delay processing unit 323 the first time that the temperature sensor 234 goes from normal to abnormal. That is, the first time that the temperature sensor 234 goes from normal to abnormal, the temperature change amount ΔT is reset to the temperature change amount ΔTR.

[0058] The following describes in detail the function of the process of resetting the temperature change amount ΔT in the calculation logic of the current limit rate CLR. FIG. 9 illustrates an example of a change in the current limiting rate CLR in response to an abnormality occurring in the temperature sensor 234 in a case where there is no function for resetting the amount of temperature change ΔT the first time an abnormality occurs in the temperature sensor 234, that is, where there is no first switching unit 324, switching request generating unit 325, or resetting unit 400. For example, assume that the temperature change ΔT in the normal state before the temperature sensor 234 became abnormal is a temperature change ΔTN1 lower than the third threshold value T3, the second current limiting rate setting unit 350 sets the current limiting rate CLR2 to 100% (no power limit), and the first current limiting rate setting unit 340 also sets the current limiting rate CLR1 to 100%, and the final current limiting rate CLR is set to 100%.

[0059] When an abnormality occurs in the temperature sensor 234 with the current limit rate CLR set in this state, the second switching unit 370 switches the output to the current limit rate CLR3 set by the third current limit rate setting unit 360. Here, if the temperature change amount ΔTN1 is a temperature near the sixth threshold value T6, the third current limiting rate setting unit 360 will output a value near 0% as the current limiting rate CLR3, and as a result, the current limiting rate CLR will suddenly switch from 100% to near 0% due to the occurrence of an abnormality in the temperature sensor 234. In other words, when an abnormality occurs in the temperature sensor 234 while the temperature change amount is ΔTN1, the state switches from no current limit to a state in which the motor drive current is limited to a minimum current or to a state in which current supply to the motor is stopped.

[0060] Also, assume that the temperature change amount ΔT in the normal state before the temperature sensor 234 became abnormal was a temperature change amount ΔTN2 that was higher than the third threshold value T3 and lower than the fourth threshold value T4, and that the current limit rate CLR was in a restricted state set to approximately 50%. In this case, when an abnormality occurs in the temperature sensor 234 and the second switching unit 370 switches the output to the current limiting rate CLR3 set by the third current limiting rate setting unit 360, the third current limiting rate setting unit 360 sets the current limiting rate CLR3 to 0% because the temperature change amount ΔTN2 is higher than the sixth threshold value T6. Therefore, when an abnormality occurs in the temperature sensor 234, the current limiting rate CLR switches from a current limiting state of 50% to a current-stopping state of 0%.

[0061] In this way, if the temperature sensor 234 becomes abnormal and the current limit rate CLR suddenly drops from its previous value, unnecessary current limiting that does not match the actual temperature of the motor driving element will be applied. In other words, even if the temperature sensor 234 becomes abnormal, the temperature of the motor drive element does not change suddenly, but the current limit rate CLR drops suddenly due to the switching of the limit start temperature to deal with the decrease in accuracy of temperature estimation due to the occurrence of an abnormality in the temperature sensor 234. In the case of the electric power steering device 200, if the drive current of the motor 220 is unnecessarily limited, this may cause a change in the steering feel given to the driver, resulting in a loss of maneuverability.

[0062] Therefore, the microcomputer 231 (resetting unit 400) resets the temperature change amount ΔT so that the current limiting rate CLR does not change and the current limiting state before the abnormality occurs is maintained the first time an abnormality occurs in the temperature sensor 234, thereby preventing unnecessary restriction of the motor drive current and avoiding a change in the driver's steering feel. In other words, when switching from a first current limiting section that performs current limiting when the temperature sensor 234 is normal to a second current limiting section that performs current limiting when the temperature sensor 234 is abnormal, the microcomputer 231 (resetting section 400) resets the temperature change amount ΔT used by the second current limiting section for current limiting so that the current limiting state by the first current limiting section before switching is maintained.

[0063] FIG. 10 shows how the temperature change amount ΔT is reset the first time an abnormality occurs in the temperature sensor 234. First, the resetting of the temperature change amount ΔT in the case where the current limit rate CLR is set to 100% when the temperature sensor 234 is in a normal state will be described. Under such conditions, in order to maintain the current limit rate CLR at 100% even if an abnormality occurs in the temperature sensor 234, the temperature change amount ΔT used to set the current limit rate CLR3 by the third current limit rate setting unit 360 needs to be less than or equal to the fifth threshold value T5.

[0064] Here, even if the second current limiting rate setting unit 350 sets the current limiting rate CLR2 to 100% based on the temperature change amount ΔTN3 that is slightly lower than the third threshold T3, if the temperature change amount ΔT is reset to decrease by the deviation between the third threshold T3 and the fifth threshold T5 (deviation amount = third threshold T3 - fifth threshold T5), the temperature change amount ΔT after resetting will be lower than the fifth threshold T5. Then, if the temperature change amount ΔT after the resetting is equal to or less than the fifth threshold value T5, which is the limitation start temperature (second limitation start temperature) in the third current limiting rate setting unit 360, the current limiting rate CLR3 by the third current limiting rate setting unit 360 becomes 100%, and the current limiting rate CLR is maintained at 100% before and after the occurrence of an abnormality in the temperature sensor 234.

[0065] Therefore, the temperature shift correction unit 410, which is responsible for resetting the temperature change amount ΔT when the motor drive current is not limited, calculates the temperature change amount ΔTR for resetting so that the current limiting rate CLR3 by the third current limiting rate setting unit 360 becomes 100%, in other words, so that the temperature change amount ΔT used to set the current limiting rate CLR3 in the third current limiting rate setting unit 360 is equal to or less than the fifth threshold value T5.

[0066] In other words, the addition and subtraction by the first temperature deviation calculation unit 411 and the third temperature deviation calculation unit 414 of the temperature shift correction unit 410 can be expressed as a formula: ΔTR=T5-(T3-ΔT), which can be expanded to ΔTR=ΔT+T5-T3, and further, ΔTR=ΔT-(T3-T5). Therefore, the addition and subtraction by the first temperature deviation calculation unit 411 and the third temperature deviation calculation unit 414 of the temperature shift correction unit 410 is a process of performing a resetting process to reduce the temperature change amount ΔT by the deviation between the third threshold value T3 and the fifth threshold value T5 (deviation amount = third threshold value T3 - fifth threshold value T5), in other words, by the amount by which the start temperature of the current limiting decreases due to an abnormality in the temperature sensor 234. The temperature deviation DT output by the temperature shift correction unit 410 is output from the switching unit 440 as the temperature change amount ΔTR1 when the current limiting rate CLR output by the third switching unit 390 is 100%, that is, when the motor drive current is not limited.

[0067] For example, assuming that the temperature change ΔT when the temperature sensor 234 is normal is 20°C, the third threshold T3 is 45°C, and the fifth threshold T5 is 10°C, the temperature change ΔTR is ΔTR = 20°C - (45°C - 10°C) = 20°C - 35°C = -15°C. Here, since the lower limit limiting unit 415 limits the temperature change amount ΔTR to a lower limit value (0°C) or more, the temperature change amount ΔTR after processing by the lower limit limiting unit 415 becomes 0°C.

[0068] Then, when an abnormality occurs in the temperature sensor 234 while the current limiting rate CLR output by the third switching unit 390 is 100%, the third current limiting rate setting unit 360 sets the current limiting rate CLR3 to 100% by using the temperature change amount ΔTR=0°C output by the temperature shift correction unit 410 to calculate the current limiting rate CLR3 for the first time after the occurrence of the abnormality. In addition, the temperature change amount ΔTR = 0°C used to calculate the current limiting rate CLR3 in the first calculation after the occurrence of an abnormality is fed back as an input to the primary lag processing unit 323, so that the temperature change amount ΔT output by the primary lag processing unit 323 gradually increases according to the flow of current to the motor, with 0°C as the initial value.

[0069] The same applies to a case where the current limit rate CLR is set to 100% when the temperature sensor 234 is in a normal state, and the current limit rate CLR is switched from the current limit rate CLR1 set by the first current limit rate setting unit 340 to the current limit rate CLR3 set by the third current limit rate setting unit 360 based on the occurrence of an abnormality in the temperature sensor 234. That is, the temperature shift correction unit 410 performs a process of resetting to reduce the temperature change amount ΔT by the deviation between the first threshold T1 and the fifth threshold T5 (deviation=first threshold temperature T1−fifth threshold T5). In this way, the temperature shift correction unit 410 performs a resetting operation to reduce the temperature change amount ΔT by the difference between the first threshold T1 and third threshold T3 (first restriction start temperature), which are the temperatures at which current restriction starts when the temperature sensor 234 is in a normal state, and the fifth threshold T5 (second restriction start temperature), which is the temperature at which current restriction starts when the temperature sensor 234 is in an abnormal state.

[0070] On the other hand, when the temperature sensor 234 is in a normal state, the current limiting rate CLR is set to less than 100% and the motor drive current is limited by the current limiting rate CLR, even if an abnormality occurs in the temperature sensor 234, the resetting unit 400 resets the temperature change amount ΔT so that the current limiting rate CLR is maintained before and after the occurrence of the abnormality in the temperature sensor 234. In this case, when an abnormality occurs in the temperature sensor 234, the current limiting rate CLR3 set by the third current limiting rate setting unit 360 is adopted as the final current limiting rate CLR. Therefore, if the temperature change amount ΔT is reset to a temperature at which the current limiting rate CLR3 set by the third current limiting rate setting unit 360 becomes the same as the current limiting rate CLR before the occurrence of the abnormality, the current limiting rate CLR will be maintained at the same value less than 100% before and after the occurrence of the abnormality in the temperature sensor 234.

[0071] Therefore, the conversion unit 420, which is responsible for resetting the temperature change amount ΔT in the limited state of the motor drive current, calculates the temperature change amount ΔT that will cause the third current limiting rate setting unit 360 to output a current limiting rate CLR3 with the same value as the current limiting rate CLR output by the third switching unit 390, and outputs this as the temperature change amount ΔTCLR. Here, since the current limiting rate CLR output by the third switching unit 390 is less than 100%, the switching unit 440 outputs the temperature change amount ΔTCLR output by the conversion unit 420 as the temperature change amount ΔTR1.

[0072] For example, assume that the temperature change amount ΔTN4 when the temperature sensor 234 is normal is 50° C., the third threshold value T3 is 45° C., and further assume that the current limit rate CLR2 is set to 50% at the temperature change amount ΔTN4. Here, if the temperature change amount ΔT when the third current limiting rate setting unit 360 sets the current limiting rate CLR3 to 50% is, for example, 15°C, the conversion unit 420 sets the temperature change amount ΔTCLR to 15°C and outputs it.

[0073] As described above, when the temperature sensor 234 is in a normal state, if the current limit rate CLR is 100% and the motor drive current is not limited, the resetting unit 400 resets the temperature change amount ΔT to such a value that the third current limit rate setting unit 360 will set the current limit rate CLR3 to 100% the first time an abnormality occurs in the temperature sensor 234. Furthermore, when the temperature sensor 234 is in a normal state, if the current limiting rate CLR is less than 100% and the motor drive current is in a limited state, the resetting unit 400 resets the current limiting rate CLR3 to the temperature change amount ΔT that becomes the same limiting rate as the current limiting rate CLR before the abnormality occurred the first time an abnormality occurs in the temperature sensor 234.

[0074] By resetting the temperature change amount ΔT in this way, the first time an abnormality occurs in the temperature sensor 234, the limited state (current limit rate) of the motor drive current before the abnormality occurs is maintained. Therefore, even if the correlation between the temperature change amount ΔT and the current limiting rate CLR is switched so that current limiting is performed based on the current limiting rate CLR from a lower temperature change amount ΔT following the occurrence of an abnormality in the temperature sensor 234, unnecessary restriction of the motor drive current is prevented while continuing to limit the motor drive current according to the temperature.

[0075] The technical ideas described in the above embodiments can be used in any suitable combination as long as no contradiction occurs. Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that a person skilled in the art can adopt various modified embodiments based on the basic technical concept and teachings of the present invention. For example, in this embodiment, an electric power steering device 200 in which the steering mechanism 210 and the steering wheel 201 as a steering member are connected by a steering shaft 202 has been described as an example, but the present invention may also be applied to a steer-by-wire type electric power steering device that does not use the steering shaft 202.

[0076] Further, the temperature shift correction unit 410 shown in FIG. 4 shifts and corrects the temperature change amount ΔT by the deviation of the restriction start temperature, specifically, the deviation between the first threshold value T1 and the fifth threshold value T5, or the deviation between the third threshold value T3 and the fifth threshold value T5, thereby determining a reset value of the temperature change amount ΔT in the non-restricted state of the motor drive current, but is not limited to such a configuration. For example, in a state where the motor drive current is not limited, the temperature shift correction unit 410 sets the reset value of the temperature change ΔT to a predetermined value ΔTPD (0°C≦ΔTPD≦T5) that is equal to or lower than the fifth threshold T5, which is the limit start temperature at which limiting of the motor drive current begins by setting the current limit rate CLR3 by the third current limit rate setting unit 360, and the first time an abnormality occurs in the temperature sensor 234, the temperature change ΔT can be reset to the predetermined value ΔTPD regardless of the temperature change ΔT or the estimated temperature TDE.

[0077] Furthermore, the conversion unit 420 may ultimately set the temperature change amount ΔT corresponding to the current limiting rate CLR before the occurrence of an abnormality in the temperature sensor 234 as the reset value in the setting characteristics of the current limiting rate CLR3 in the third current limiting rate setting unit 360, and is not limited to a configuration using a conversion map that converts the current limiting rate CLR into the temperature change amount ΔT. In addition, the conversion unit 420 is not limited to a configuration in which the temperature change amount ΔT is set as a reset value so that the current limiting rate CLR is set to the same value as before the abnormality occurred in the temperature sensor 234, but can determine a reset value for the temperature change amount ΔT so that the current limiting rate CLR is within an acceptable range that is adapted taking into account changes in steering force, etc. In other words, the current limiting rate CLR before the occurrence of an abnormality in the temperature sensor 234 and the initial current limiting rate CLR after the occurrence of the abnormality do not need to be the same, but may be approximately the same within a range that does not substantially affect the steering force.

[0078] In addition, in the correlation between the temperature change ΔT or estimated temperature TDE and the current limiting rate CLR, the correlation between the temperature and the current limiting rate CLR when the current limiting rate CLR changes from 100% to 0% in a temperature range higher than the first threshold T1, the third threshold T3, and the fifth threshold T5, which are the limitation start temperatures, is not limited to being linear and may be non-linear. Also, a configuration may be adopted in which the second current limiting rate setting unit 350 is not provided, and either the current limiting rate CLR1 set by the first current limiting rate setting unit 340 or the current limiting rate CLR3 set by the third current limiting rate setting unit 360 is selected depending on whether the temperature sensor 234 is normal or abnormal. [Explanation of symbols]

[0079] 220...motor, 230...motor control device (control unit), 231...microcomputer, 232...drive circuit, 233...circuit board, 234...temperature sensor

Claims

1. A motor control device that acquires a temperature detection value by a temperature sensor that detects a temperature of a substrate on which a drive element that drives a motor is mounted and an actual current value flowing through the motor, and limits a target current value supplied to the motor to a small value based on the temperature detection value, The motor control device includes: A temperature change amount of the driving element is calculated from an actual current value flowing through the motor; performing a first current limiting control for limiting a target current value supplied to the motor based on a temperature detection value by the temperature sensor and the amount of temperature change when the temperature sensor is normal; When the temperature sensor is abnormal, a second current limiting control is performed to limit a target current value to be supplied to the motor based on the temperature change amount from the temperature change amount that is lower than that during the first current limiting control. when switching from the first current limiting control to the second current limiting control based on the occurrence of an abnormality in the temperature sensor, the temperature change amount used for current limiting in the second current limiting control is reset so that a current limiting state by the first current limiting control before the switching is maintained. Motor control device.

2. 2. The motor control device according to claim 1, When the current limiting by the first current limiting control has not been performed before switching to the second current limiting control, the temperature change amount is reset based on a temperature equal to or lower than a second limiting start temperature at which the current limiting is started by the second current limiting control; When the current limiting control is performed by the first current limiting control before switching to the second current limiting control, the temperature change amount is reset so that the current limiting control is performed by the second current limiting control to the same extent as the current limiting control by the first current limiting control. Motor control device.

3. 3. The motor control device according to claim 2, When the current limiting by the first current limiting control unit has been performed before switching to the second current limiting control, a reset is performed to reduce the temperature change amount by a difference between a first limiting start temperature at which the current limiting is started by the first current limiting control and a second limiting start temperature at which the current limiting is started by the second current limiting control. Motor control device.

4. 4. The motor control device according to claim 3, In resetting the temperature change amount based on the difference between the first restriction start temperature and the second restriction start temperature, the temperature change amount after resetting is limited so as not to fall below a specified temperature. Motor control device.

5. 2. The motor control device according to claim 1, estimating a temperature of the driving element based on the temperature detected by the temperature sensor and the amount of temperature change; selecting a current limit based on the estimated value of the temperature of the drive element or a current limit based on the amount of change in temperature that limits the target current value lower, and then performing the current limit; Motor control device.

6. 2. The motor control device according to claim 1, The motor is a motor that applies a steering force to a steering mechanism of an electric power steering device mounted on a vehicle. Motor control device.

7. A motor control method implemented by a control unit, comprising: acquiring a temperature detection value by a temperature sensor that detects a temperature of a substrate on which a drive element that drives a motor is mounted, and an actual current value flowing through the motor; and limiting a target current value supplied to the motor to a small value based on the temperature detection value, A temperature change amount of the driving element is calculated from an actual current value flowing through the motor; performing a first current limiting control for limiting a target current value supplied to the motor based on a temperature detection value by the temperature sensor and the amount of temperature change when the temperature sensor is normal; When the temperature sensor is abnormal, a second current limiting control is performed to limit a target current value to be supplied to the motor based on the temperature change amount from the temperature change amount that is lower than that during the first current limiting control. when switching from the first current limiting control to the second current limiting control based on the occurrence of an abnormality in the temperature sensor, the temperature change amount used for current limiting in the second current limiting control is reset so that a current limiting state by the first current limiting control before the switching is maintained. Motor control methods.

8. An electric power steering device having a steering mechanism for changing a tire angle of a wheel of a vehicle, a motor for applying a steering force to the steering mechanism, and a control unit for controlling the motor based on an operation of a steering member of the vehicle, The control unit is a temperature detection value by a temperature sensor that detects the temperature of a substrate on which a drive element that drives the motor is mounted and an actual current value flowing through the motor are obtained, and a target current value to be supplied to the motor is limited to a small value based on the temperature detection value; A temperature change amount of the driving element is calculated from an actual current value flowing through the motor; performing a first current limiting control for limiting a target current value supplied to the motor based on a temperature detection value by the temperature sensor and the amount of temperature change when the temperature sensor is normal; When the temperature sensor is abnormal, a second current limiting control is performed to limit a target current value to be supplied to the motor based on the temperature change amount from the temperature change amount that is lower than that during the first current limiting control. when switching from the first current limiting control to the second current limiting control based on the occurrence of an abnormality in the temperature sensor, the temperature change amount used for current limiting in the second current limiting control is reset so that a current limiting state by the first current limiting control before the switching is maintained. Electric power steering device.

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