JP2002362386A - Motor driving device and electric power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor driving device and an electronic power steering that can improve accuracy in detecting the abnormal state of a steering auxiliary circuit for outputting a steering auxiliary indicator current to a motor for applying steering auxiliary force. SOLUTION: This motor driving device is provided with a threshold setting means a for setting the abnormality determining threshold of a driving circuit according to a driving indicator current; a current detecting means b for detecting an actual current actually inputted to the motor; and an abnormality detecting means c for detecting the abnormality of the driving circuit when the actual current detected by the current detecting means b is not more than the abnormality determining threshold set by the threshold setting means a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor driving device and an electric power steering device for applying a steering assist force by an electric motor to a steering shaft, and more particularly to a technique for detecting an abnormality in a driving circuit that outputs a driving instruction current to the electric motor. About.

[0002]

2. Description of the Related Art As a conventional electric motor driving device or electric power steering device provided with this kind of abnormality detecting means, for example, the one described in Japanese Patent Application Laid-Open No. 63-180567 (electric power steering device) is known. Have been. That is, in general, in the electric power steering device, an abnormality occurs in the steering assist circuit (drive circuit) such as a short circuit of the power element of the power element unit that controls the current and the direction of the current supplied to the electric motor that applies the steering assist force. Causes the troubles such as burnout of the wiring and the inability to use the battery. In order to prevent this, in the conventional example, as shown in the time chart of FIG. If the difference between the steering assist command current for the motor and the actual current actually flowing to the electric motor exceeds a predetermined abnormality determination threshold and the state continues for a certain period of time, it is determined that the steering assist circuit such as the power element unit is abnormal. However, as an abnormal process, each power element is switched to an off state.

[0003]

However, in the conventional power steering apparatus, as described above, the abnormality determination threshold for determining the abnormality of the steering assist circuit such as the power element unit is fixed to a constant value. Therefore, the abnormality determination threshold value cannot be changed in accordance with the fluctuation of the steering assist instruction current value, and therefore, the detection accuracy when detecting an abnormal state of the steering assist circuit such as the power element unit is detected. There was a problem that cannot be raised.

The present invention has been made in view of the above-mentioned conventional problems, and provides an electric power steering apparatus capable of improving the accuracy of detecting an abnormal state of a drive circuit that outputs a drive instruction current to an electric motor. The purpose is to do.

[0005]

In order to achieve the above object, an electric power steering apparatus according to a first aspect of the present invention provides an electric motor for applying a rotational force to a driven portion, and outputs a drive instruction current to the electric motor. A threshold value setting unit a for setting an abnormality determination threshold value of the drive circuit according to the drive instruction current, as shown in the claim correspondence diagram of FIG. Current detection means b for detecting an actual current actually inputted to the electric motor
And abnormality detection means c for detecting an abnormality in the drive circuit when the actual current detected by the current detection means b is equal to or less than the abnormality determination threshold value set by the threshold value setting means a. An electric motor drive device characterized by the above-mentioned.

According to a second aspect of the present invention, there is provided an electric power steering apparatus, comprising: a torque sensor for detecting a torque acting on a steering shaft; an electric motor for applying a steering assisting force to the steering shaft; and a motor acting on the steering shaft detected by the torque sensor. A drive circuit for outputting a drive instruction current to the motor based on the torque signal to be applied; threshold setting means a for setting an abnormality determination threshold of the drive circuit in accordance with the drive instruction current; Current detection means b for detecting the actual current input to the
Means for detecting an abnormality in the drive circuit when the actual current detected by the current detection means b is equal to or less than the abnormality determination threshold value set by the threshold value setting means; and c. And

According to a third aspect of the present invention, there is provided the electric motor driving device or the electric power steering device according to the first or second aspect, wherein the abnormality detecting means c is provided with the electric current detecting means b.
When the state in which the actual current detected in step (a) is equal to or less than the abnormality determination threshold value set by the threshold value setting means (a) continues for a predetermined time, the drive circuit is configured to detect abnormality.

According to a fourth aspect of the present invention, in the electric power steering apparatus according to any one of the first to third aspects, the threshold value setting means a is configured to reduce the drive instruction current. The abnormality determination threshold value is variably set so that the difference between the drive instruction current and the actual current is smaller than when it is large.

According to a fifth aspect of the present invention, in the electric motor driving device or the electric power steering device according to any one of the first to third aspects, the threshold value setting means a includes the driving device. The abnormality determination threshold is variably set so that the difference between the drive instruction current and the actual current is larger when the indicated current is smaller than when it is larger.

According to a sixth aspect of the present invention, there is provided an electric motor driving apparatus or an electric power steering apparatus according to any one of the first to fifth aspects, wherein the instruction for calculating a change rate of the driving instruction current is provided. Current change rate calculation means; and abnormality detection prohibition means for prohibiting abnormality detection in the abnormality detection means c when the change rate of the drive instruction current calculated by the instruction current change rate calculation means is equal to or greater than a predetermined value. That means.

According to a seventh aspect of the present invention, in the electric motor driving apparatus or the electric power steering apparatus according to any one of the first to sixth aspects, the abnormality detecting means c is replaced with the electric current detecting means b.
Means for detecting an abnormality in the drive circuit even when the actual current detected in step (1) exceeds a preset upper threshold regardless of the drive instruction current.

[0012]

In the motor drive device according to the first aspect of the present invention, as described above, the threshold value setting means a can freely set the abnormality determination threshold value of the drive circuit in accordance with the drive instruction current. The accuracy of detecting an abnormal state of the drive circuit that outputs the drive instruction current can be improved.

In the electric power steering apparatus according to the second aspect of the invention, as described above, the threshold value setting means a can freely set the abnormality determination threshold value of the drive circuit according to the drive instruction current. The detection accuracy of the abnormal state of the drive circuit that outputs the drive current is improved, and thereby, particularly, the safety during running of the vehicle can be improved.

In the electric driving device or the electric power steering device according to the third aspect, the abnormality detecting means c determines the abnormality determination threshold value set by the threshold value setting means a based on the actual current detected by the current detecting means b. By being configured to detect an abnormality of the drive circuit only when the state equal to or less than the value continues for a predetermined time, the detection accuracy of the abnormal state can be further improved.

In the electric driving device or the electric power steering device according to the present invention, the error for detecting an abnormality generally increases as the actual current flowing through the electric motor increases. In a
When the drive instruction current is small, the abnormality determination threshold is variably set so that the difference between the drive instruction current and the actual current is smaller than when the drive instruction current is large. Can be improved, and
It is possible to prevent erroneous detection of abnormality detection when the drive instruction current is large.

In the electric driving apparatus or the electric power steering apparatus according to the fifth aspect, in general, as the actual current flowing through the motor increases, the danger due to self-steering (the motor outputs more driving force than necessary due to abnormality in the driving circuit). Since the degree of accuracy is high, especially in the electric power steering apparatus, it is necessary to make the detection accuracy of the abnormality detection strict. Therefore, as described above, in the threshold value setting means a,
The abnormality determination threshold is variably set so that the difference between the drive instruction current and the actual current is larger when the drive instruction current is small than when it is large (the difference is smaller as the drive instruction current is larger). Therefore, the accuracy of abnormality detection when the drive instruction current is large can be improved, and thereby the accuracy of abnormality detection when the drive instruction current, which does not significantly affect the occurrence of self-steering, is small. This prevents detection.

In the electric drive device or the electric power steering device according to the present invention, when the change rate of the drive command current calculated by the command current change rate calculation means is equal to or more than a predetermined value, abnormality detection is prohibited. By prohibiting the abnormality detection by the abnormality detecting means c, the erroneous determination of the abnormality detection when the steering speed is high is prevented, especially in the electric power steering device, and thereby unnecessary stop of the device is prevented. You can avoid it.

In the electric driving device or the electric power steering device according to the present invention, as described above, the actual current detected by the current detecting means b is set to a predetermined upper threshold regardless of the driving instruction current. Abnormality detection means c when exceeding
By detecting abnormalities in the drive circuit in
With a simple configuration, it is possible to perform abnormality detection when the actual current flows excessively with respect to the command current.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) First, Embodiment 1 of the present invention
Corresponds to the invention of claims 2 to 4,
The configuration will be described with reference to FIGS.

FIG. 2 is an overall schematic view showing an electric power steering apparatus according to Embodiment 1 of the present invention. As shown in FIG. 2, when the steering wheel 1 is manually rotated, the rotation is changed to a steering shaft (input). Shaft) 2, a steering shaft (output shaft) 5, a universal joint 6, an intermediate shaft 7, and a universal joint 8 to be transmitted to a pinion shaft 9, and the pinion shaft 9 is screwed into the rack shaft 10 to rotate the pinion shaft 9. Is converted into a linear motion of the rack shaft 10, and this linear motion changes (steers) the directions of the left and right front wheels via the tie rods 11a and 11b. And the steering shaft (input shaft) 2
The steering shaft (output shaft) 5 is configured to be rotatable via the speed reducer 4 by the electric motor 12 provided between the steering shaft (output shaft) 5 and the steering shaft (output shaft) 5, so that the manual steering force is assisted. It has become.

The motor 12 is controlled by a steering assist circuit (drive circuit) incorporated in a vehicle-mounted control unit 13 based on a signal from a torque sensor 3 for detecting a manual steering force. As a result, the steering force is manually assisted. Also,
A vehicle speed signal from a vehicle speed sensor 14 is input to a steering assist circuit of the control unit 13. In FIG. 1, reference numeral 15 denotes an ignition switch, and reference numeral 16 denotes a vehicle-mounted battery.

Next, a specific configuration of the control unit 13 will be described with reference to a control system block diagram of FIG. 3. A steering torque calculating means 13a calculates a steering torque based on an input signal from the torque sensor 3. On the other hand, the vehicle speed calculating means 13b calculates the vehicle speed based on the input signal from the vehicle speed sensor 14. Then, in the following instruction current calculation means 13c, a steering assist instruction current (drive instruction current) to be output to the electric motor 12 according to the steering torque signal and the vehicle speed signal (hereinafter simply referred to as an instruction current).
icmd is calculated.

In the following PWM duty determining means 13d, an on-duty ratio in the PWM (pulse width modulation) operation of the motor 12 is determined based on the command current icmd and the actual current i detected by the motor current detecting means described later. P of determined on-duty ratio
The WM signal is output to the power element driving means 13f. The power element driving means 13f drives the gates of the power elements 13i, 13j, 13k, and 131 of the power element section P based on the PWM signal of the on-duty ratio to drive the power elements 13i, 13j, 13k, 13l
Is switched, whereby an energizing direction instruction to the electric motor 12 and an ON / OFF instruction for controlling the energizing current value are issued.

Incidentally, the steering torque calculating means 13
a, vehicle speed calculating means 13b, command current calculating means 13c, P
WMDUTY determining means 13d, power element driving means 13
f and the power element section P constitute a steering assist circuit that outputs a command current icmd to the electric motor 12.

In the current detecting means 13e, the motor 1
A voltage difference is taken out from both ends of a shunt resistor 13h constituting a current sensor inserted in series in the middle of the second drive power supply line L, and an actual current flowing to the electric motor 12 is based on this voltage difference (voltage drop value). The current i is detected, and the actual current i is output to the PWM duty determining means 13d and the abnormality detecting means 13g.

The abnormality detecting means 13g detects an abnormality in the PWM duty determining means 13d, the power element driving means 13f, and the power element section P in the steering assist circuit. More specifically, the abnormality detection unit 13g creates an abnormality determination threshold value and performs abnormality detection.

Next, a method of creating an abnormality determination threshold value and an abnormality determination method in the abnormality detection means 13g will be described with reference to FIG.
This will be described in detail based on the flowchart of FIG. First, an abnormality determination threshold value is created in steps S101 to S103. In step S101, an instruction current icmd output from the instruction current calculation unit 13c is read. In step S102, the read instruction is read. The current icmd is converted into an absolute value | icmd |, and in step S103, a predetermined gain K (0 <K) is applied to the absolute value | icmd |
<1) is multiplied to determine an abnormality determination threshold value (K × | icmd |) (see the block diagram of FIG. 5 and the time chart of FIG. 6).
That is, as described above, by multiplying the absolute value | icmd | of the command current icmd by the predetermined gain K, as shown in (c) of FIG. The abnormality determination threshold value (K × | icmd |) is variably set so that the difference between the absolute value | icmd | of icmd and the actual current i becomes small.

Next, at step 104, it is determined whether or not the abnormality determination threshold value (K × | icmd |) is equal to or greater than the abnormality determination dead zone value C. If YES (K × | icmd | ≧ C), Proceeding to step 105, after reading the actual current i actually flowing through the electric motor 12 detected by the motor current detecting means 13e, proceeding to step S106. In this step S106, it is determined whether or not the actual current i is equal to or less than an abnormality determination threshold value (K × | icmd |). If YES (K × | icmd | ≧ i), an abnormality is detected in the steering assist circuit. Is determined to have occurred, the process proceeds to step S107, and the error counter of the abnormality detection timer
After incrementing Cerr by 1, the process proceeds to step S108.

On the other hand, if the determination in step S104 is NO
(K × | icmd | <C), the absolute value of the command current icmd
Since the difference between | icmd | and the actual current i is small and it is easy to make an erroneous abnormality determination, in this case, no abnormality determination is made and step S1
In step S11, the error counter Cerr is reset to 0. In step S112, the abnormality detection flag f_ierr is reset to 0. Then, one flow is completed. If the determination in step S106 is NO (K × | icmd | <i), the process proceeds to step S111 to reset the error counter Cerr to 0, and then resets the abnormality detection flag f_ierr to 0 in step S112. This completes one flow.

In step S108, it is determined whether or not the error counter Cerr of the abnormality detection timer is equal to or greater than the timer threshold Thr. If YES (Cerr ≧ Thr), some abnormality occurs in the steering assist circuit. Then, the process proceeds to step S109 to set the abnormality detection flag f_ierr to 1, and then proceeds to step S110 to perform abnormality processing, thereby ending one flow. Step S
If the determination at 108 is NO (Cerr <Thr), it is due to the temporary fluctuation of the actual current i, and it is not determined that the steering assist circuit is abnormal.
After resetting f_ierr to 0, this ends one flow.

Next, the operation and effect of the first embodiment of the present invention will be described with reference to the time charts of FIGS. That is, generally, the detection error for abnormality detection is
Depends on the magnitude of the actual current i (≒ instruction current icmd) flowing through the power supply. The larger the actual current i is, the smaller the actual current i is. Therefore, in the electric power cylinder device according to the first embodiment of the present invention, as described above, the absolute value | icmd | of the command current icmd is multiplied by a predetermined gain K (0 <K <1) to determine the abnormality determination threshold value. (K × | icmd |) to obtain FIG.
As shown in the time chart (c), when the command current icmd is small, the absolute value of the command current icmd | icmd |
And the actual current i are smaller (the difference between the absolute value | icmd | of the command current icmd and the actual current i is larger when the command current icmd is larger than when the command current icmd is smaller). K × | icmd |) is variably set so that the indicated current
The accuracy of abnormality detection when icmd is small can be improved, and erroneous detection of abnormality when the command current icmd is large can be prevented.

When the abnormality determination threshold value (K × | icmd |) is smaller than the abnormality determination dead zone value C, when the difference between the absolute value | icmd | Since the determination is easy, in this case, the abnormality determination is stopped, so that an erroneous determination when the command current icmd is small can be prevented.

Further, in the conventional example shown in FIG. 7A, even if the command current changes abruptly due to disturbance due to road surface input or the like, the difference between the command current and the actual current is not less than or equal to a predetermined abnormality determination threshold. If the period of time is equal to or greater than a predetermined abnormality determination timer threshold value, it is erroneously determined that the current is abnormal.

On the other hand, in the embodiment of the invention shown in FIG. 7B, even if the command current icmd changes rapidly due to disturbance, the current abnormality determination threshold value K × | icmd | , The time in which i> K × | icmd | is shorter than in the conventional example, so that an erroneous determination can be prevented.

As described above in detail, in the electric power steering apparatus according to the first embodiment of the present invention, the accuracy of detecting the abnormal state of the steering assist circuit that outputs the steering assist instruction current to the motor that applies the steering assist force. Is obtained, and the accuracy of abnormality detection can be improved.

Next, another embodiment of the present invention will be described.
In describing other embodiments of the present invention,
The same components as those in the first embodiment of the invention are omitted from the drawings and description, or the same reference numerals are given and the description is omitted, and only different points will be described.

(Embodiment 2) An electric power steering apparatus according to Embodiment 2 of the present invention corresponds to the inventions of Claims 2, 3 and 5 and is an embodiment of the invention. 1 is different from the method of creating the abnormality determination threshold value in the abnormality detection means 13g and the content of the abnormality determination prohibition processing. The other configuration is the same as that of the first embodiment of the present invention, The description of the components will be omitted, and only the differences will be described.

FIG. 8 is a flowchart showing a method of creating an abnormality determination threshold value and an abnormality determination method in the abnormality detection means 13g. FIG. 9 shows the relationship between the absolute value | icmd | of the command current icmd and the abnormality determination offset value G. FIG. 10 is a block diagram showing a method for calculating an abnormality determination threshold, and FIG.
Is the same time chart. First, the flowchart of FIG. 8 will be described.

In the flowchart of FIG. 8, an abnormality determination threshold value is created in steps S201 to S203. In step S201, an instruction current icmd output from the instruction current calculation means 13c is read. The instruction current icmd read in step S202
Is converted to an absolute value | icmd | in steps S101 and S101 in the flowchart of FIG.
2, but the contents of steps S203 and S204 are different from those of step S103.

That is, in step S203, an offset value G (f (| icmd |)) for generating an abnormality determination threshold is obtained from the absolute value | icmd | of the indicated current with reference to the map shown in FIG. The map used in the second embodiment of the present invention has a content in which the offset G decreases as the absolute value | icmd | of the command current increases.

In the following step S204, as shown in the block diagram of FIG. 10, the offset value G is subtracted from the absolute value | icmd |
d | −G) is determined, and in the subsequent step S205, it is determined whether or not the abnormality determination threshold | icmd |
If ES (| icmd | <0), the process proceeds to step S206 to set the abnormality determination threshold value (| icmd | -G) to 0 (positive limiter process), and then proceeds to step 207,
If NO (| icmd | ≧ 0), step S2
Proceed to 07.

Steps S207 to S214 are the same as those in steps S105 to S112 of FIG. 4 in the first embodiment of the present invention, except that the content of the abnormality determination threshold is different as described above. It is.

Next, the operation and effect of the second embodiment of the present invention will be described with reference to the time chart of FIG. In general, as the actual current i (≒ instruction current icmd) flowing through the motor 12 increases, the risk of self-steering (the motor 12 outputs an unnecessarily large steering assist force due to an abnormality in the steering assist circuit) increases. It is necessary to make the detection accuracy strict (the difference from the actual current i is small), but in this case, the risk of erroneous detection of an abnormality when the actual current i (≒ instruction current icmd) is small increases. Therefore, in the second embodiment of the present invention, as described above, the map of FIG. 9 shows that the abnormality determination threshold value creating offset value G decreases as the absolute value | icmd | of the command current increases. Is used, the difference between the absolute value | icmd | of the indicated current and the actual current i becomes larger when the absolute value | icmd | of the indicated current is smaller than when it is larger (the absolute value | icmd | The abnormality determination threshold value is variably set such that the larger the difference, the smaller the difference becomes), thereby improving the accuracy of abnormality detection when the indicated current is large.

As described above in detail, in the electric power steering apparatus according to the second embodiment of the present invention, the command current which is not so affected even if self-steering occurs.
The abnormality detection accuracy when icmd is small can be reduced, thereby preventing erroneous detection.

(Embodiment 3) An electric power steering apparatus according to Embodiment 3 of the present invention is the electric power steering apparatus according to Embodiment 1.
A command current change rate calculating means, based on the change rate dicmd / dt of the command current icmd calculated by the command current change rate calculating means. The point that the determination prohibition process is performed is different from the first embodiment of the present invention, and the other configuration is the same as that of the first embodiment of the present invention. The description is omitted, and only the differences will be described.

FIG. 12 is a flowchart showing a method of creating an abnormality determination threshold value and an abnormality determination method in the abnormality detection means 13g. In the flowchart of FIG. 12, an abnormality determination threshold value is created in steps S301 to S303, and the contents are the same as those in steps S101 to S103 of the flowchart of FIG. 4 in the first embodiment of the present invention. .

In the subsequent step 304 (instruction current change rate calculating means), the change rate (dicmd / dt) is obtained from the instruction current icmd read in step S301.
FIG. 13 is a block diagram showing a method of calculating a command current change rate, and FIG. 14 is a block diagram showing further details thereof. First, a high-pass filter HPF (cutoff frequency fc =
The current value icmd of the indicated current is differentiated at 50 Hz) and a low-pass filter LPF (cutoff frequency fc = 200 Hz)
By removing the high-frequency components by the above, the change rate dicmd / dt of the command current obtained by smoothing the differential waveform is obtained. In FIG. 14, icmd (n) is the current value of the command current, icmd (n-
1) is a value just before the indicated current, and K1 and K2 are discretizations of the transfer function τs / (1 + τs) of the high-pass filter HPF by bilinear transformation T (1-Z ⁻¹ ) / 2 (1-Z ⁻¹ ). K3 and K4 are the transfer function 1 of the low-pass filter LPF
Like the HPF, / (1 + τs) is a coefficient when discretized by bilinear transformation, Z ⁻¹ is the value of the output of each of the high-pass filter HPF and the low-pass filter LPF, and T is the sample time.

In the following step S305, the command current icmd
After the process of converting the rate of change (dicmd / dt) into the absolute value | dicmd / dt |, the process proceeds to step S306.

In step S306, it is determined whether or not the absolute value | dicmd / dt | of the indicated current change rate is less than a count-up suspension threshold Thd, and YES (| dicmd / d
If t | <Thd), the process proceeds to step S307 to perform an abnormality determination process. Note that steps S307 to S307
The contents of the abnormality determination processing in 315 are described in Embodiment 1 of the invention.
Are the same as steps S105 to S112 in FIG.

In step S306, NO (| dic
If md / dt | ≧ Thd), the abnormality determination is not performed as a temporary operation due to rapid steering, and the process proceeds to step S314 to reset the error counter Cerr to 0. At the next step S315, the abnormality detection flag f_ierr Is reset to 0, and this ends one flow.

Next, the operation and effect of the third embodiment of the present invention will be described with reference to the time chart of FIG. As in the first embodiment of the present invention, the motor current detecting means 13
e, the actual current i actually flowing through the motor 12 detected by the motor 12 is equal to the abnormality determination threshold (K × | i
cmd |) or less, it is considered that an abnormality has occurred in the steering assist circuit, but the command current icmd may fluctuate temporarily due to disturbance from the road surface. That is, as described above, the command current icmd is calculated based on the steering torque signal detected by the torque sensor 3, and the torque fluctuation is detected by the torque sensor 3 due to disturbance from the road surface. Only the command current icmd fluctuates, and this is not due to an abnormality in the steering assist circuit itself.

In such a case, the absolute value of the indicated current change rate | dicmd / dt |
While it is equal to or greater than Thr, abnormality determination is prohibited (counting up of the error counter Cerr of the abnormality detection timer is stopped), thereby preventing erroneous determination of abnormality detection due to sudden turning, Unnecessary stoppage of the device can be avoided.

(Embodiment 4) An electric power steering apparatus according to Embodiment 4 of the present invention corresponds to the first, second, fourth and fifth aspects of the present invention. A current change rate calculation means, and a change rate di of the command current icmd calculated by the command current change rate calculation means.
The point that the abnormality determination prohibition process is performed based on cmd / dt is different from the first embodiment of the present invention, and the other configuration is the same as that of the first embodiment of the present invention. , The description of the same components is omitted,
Only the differences will be described. The third embodiment differs from the third embodiment in the method of calculating the command current change rate dicmd / dt in the command current change rate calculation means.

FIG. 16 is a flowchart showing a method of creating an abnormality determination threshold value and an abnormality determination method in the abnormality detection means 13g. In the flowchart of FIG. 16, an abnormality determination threshold value is created in steps S401 to S404, and the contents are the same as those in steps S201 to S204 of the flowchart of FIG. 8 in the second embodiment of the present invention. .

In the following step 405 (instruction current change rate calculating means), the change rate (dicmd / dt) is obtained from the instruction current icmd read in step S401.
FIG. 17 is a block diagram showing a method of calculating the indicated current change rate. As shown in this figure, the moving average process twice and the indicated current change rate calculation are performed to remove the high frequency component of the indicated current icmd. That is, the current value of the command current is calculated from the sum of the current value of the command current icmd (n) and the immediately preceding value of the command current icmd (n-1).
The value icmd (nm) m times before icmd (n) and the value m times before the indicated current
Subtract the previous value of icmd (nm-1)
(nm) The change value of the command current icmd during the time period is obtained, and the change value of the command current icmd is calculated by multiplying the change value by a coefficient K (a value corresponding to 1 / minute of n ■ m). Is done.

In the following step S406, the command current icmd
After performing the process of converting the rate of change (dicmd / dt) into the absolute value | icmd / dt |, the process proceeds to step S407 in the same manner as in the third embodiment of the present invention, and the subsequent step S408
Steps S205 to S417 are the same as steps S205 to S214 in FIG. 8 in the second embodiment of the present invention.

As described above in detail, the electric power steering apparatus according to the fourth embodiment of the present invention has the same effects as those of the second and third embodiments of the present invention.

(Embodiment 5) An electric power steering apparatus according to Embodiment 5 of the present invention is the electric power steering apparatus according to Claim 6.
Embodiments 1 to 4 of the present invention
However, the configuration will be described in addition to the first embodiment of the present invention. That is, Embodiment 5 of the present invention.
In FIG. 18, as shown in FIG. 18, a current upper limit abnormality determination threshold value (upper limit threshold value) is set in advance, and the actual current i detected by the current detecting means 13e is set in advance regardless of the command current icmd. The abnormality detecting means 13g also detects abnormality of the steering assist circuit when the current upper limit abnormality determination threshold is exceeded. Therefore, it is possible to detect abnormality when the actual current i flows excessively with respect to the command current icmd with a simple configuration.

Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration is not limited to those embodiments of the present invention, and there are design changes and the like without departing from the gist of the present invention. Are also included in the present invention.

For example, in the first embodiment of the present invention, the electric drive device has been described by taking the electric power steering device as an example, but the present invention can be applied to all other electric motor drive devices.

In the first embodiment of the present invention,
An abnormality determination threshold value (K × | icmd |) is obtained by multiplying the absolute value | icmd | of icmd by a predetermined gain K (0 <K <1), as shown in FIG. By using the map, an abnormality determination threshold value similar to that of the first embodiment can be created as shown in FIG.

In Embodiment 2 of the present invention, FIG.
To the map of FIG. 20, as shown in the map of FIG.
By using a map in which the offset value G for generating an abnormality determination threshold is fixed to a constant value, as shown in FIG. The abnormality determination threshold can be variably set so that the difference between the value | icmd | and the actual current i is always constant.

[0063]

As described above, in the motor drive device according to the first aspect of the present invention, as described above, the threshold value for setting the abnormality determination threshold value of the drive circuit according to the drive instruction current Setting means, current detection means for detecting an actual current actually input to the electric motor, and an actual current detected by the current detection means being equal to or less than an abnormality determination threshold value set by the threshold value setting means. And abnormality detecting means for detecting an abnormality of the drive circuit at the time, since the threshold value setting means can freely set the abnormality determination threshold value of the drive circuit according to the drive instruction current, The effect is obtained that the accuracy of detecting an abnormal state of the drive circuit that outputs the drive instruction current to the motor can be improved.

In the electric power steering apparatus according to the second aspect, as described above, the threshold setting means for setting the abnormality determination threshold of the drive circuit according to the drive instruction current, Current detection means for detecting an input actual current; and an abnormality for detecting an abnormality in the drive circuit when the actual current detected by the current detection means is equal to or less than an abnormality determination threshold value set by the threshold value setting means. A threshold value setting unit that can freely set an abnormality determination threshold value of the drive circuit in accordance with the drive instruction current. The detection accuracy of the abnormal state of the circuit is improved, and thereby, an effect is obtained that it is possible to improve the safety particularly during running of the vehicle.

In the motor drive device or the electric power steering device according to the third aspect, in the motor drive device or the electric power steering device according to the second aspect, the abnormality detection means is detected by the current detection means. Means for detecting an abnormality in the drive circuit when the state in which the actual current is equal to or less than the abnormality determination threshold value set by the threshold value setting means has continued for a predetermined period of time. The detection accuracy can be further improved.

In the electric motor driving device or the electric power steering device according to the fourth aspect, in the electric motor driving device or the electric power steering device according to any one of the first to third aspects, the threshold value setting means may include the driving instruction. When the current is small, the abnormality determination threshold is variably set so that the difference between the drive instruction current and the actual current is smaller than when the current is large, so that the drive instruction The abnormality detection accuracy when the current is small can be improved, and erroneous detection of abnormality detection when the drive instruction current is large can be prevented.

According to a fifth aspect of the present invention, in the electric motor driving apparatus or the electric power steering apparatus according to any one of the first to third aspects, the threshold value setting means may include the driving signal. When the current is small, the abnormality determination threshold is variably set so that the difference between the drive instruction current and the actual current is larger than when the current is large, so that the drive instruction Abnormality detection accuracy when the current is large can be improved, and in particular, in the electric power steering device, the abnormality detection accuracy when the drive instruction current that is not so much affected even when self-steering occurs is small is reduced. This can prevent erroneous detection.

According to a sixth aspect of the present invention, in the electric motor driving apparatus or the electric power steering apparatus according to any one of the first to fifth aspects, an instruction for calculating a change rate of the driving instruction current is provided. Current change rate calculation means, and abnormality detection prohibition means for prohibiting abnormality detection in the abnormality detection means when the change rate of the drive instruction current calculated by the instruction current change rate calculation means is equal to or more than a predetermined value. In particular, in the electric power steering device, erroneous determination of abnormality detection when the steering speed is high can be prevented, and thereby unnecessary stop of the device can be avoided.

According to a seventh aspect of the present invention, in the motor driving device or the electric power steering device according to any one of the first to sixth aspects, the abnormality detecting means is detected by the current detecting means. Means for detecting an abnormality in the drive circuit even when the actual current obtained exceeds a preset upper threshold regardless of the drive instruction current. An abnormality can be detected when the current flows excessively with respect to the command current.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is an overall schematic diagram showing the electric power steering device according to the first embodiment of the present invention.

FIG. 3 is a system block diagram illustrating the electric power steering device according to the first embodiment of the present invention;

FIG. 4 is a flowchart showing a method for determining an abnormality in the electric power steering device according to the first embodiment of the present invention.

FIG. 5 is a block diagram illustrating a method of calculating an abnormality determination threshold value in the electric power steering device according to the first embodiment of the present invention.

FIG. 6 is a time chart illustrating a method of calculating an abnormality determination threshold value in the electric power steering device according to the first embodiment of the present invention.

FIGS. 7A and 7B are time charts showing the operation contents of the abnormality detecting means, wherein FIG. 7A shows the operation contents of the conventional example, and FIG. 7B shows the operation contents of the electric power steering apparatus according to the first embodiment of the present invention.

FIG. 8 is a flowchart illustrating a method for determining an abnormality in the electric power steering device according to the second embodiment of the present invention.

FIG. 9 is a map for obtaining an offset value for generating an abnormality determination threshold value in the electric power steering device according to the second embodiment of the present invention.

FIG. 10 is a block diagram illustrating a method for calculating an abnormality determination threshold value in the electric power steering device according to the second embodiment of the present invention.

FIG. 11 is a time chart illustrating a method of calculating an abnormality determination threshold value in the electric power steering device according to the second embodiment of the present invention.

FIG. 12 is a flowchart illustrating a method of determining an abnormality in the electric power steering device according to the third embodiment of the present invention.

FIG. 13 is a flowchart illustrating a method for calculating a command current change rate in the electric power steering device according to the third embodiment of the present invention.

FIG. 14 is a block diagram showing specific contents of a method for calculating a command current change rate in the electric power steering device according to Embodiment 3 of the present invention.

FIG. 15 is a time chart showing operation contents of abnormality detection means in the electric power steering device according to Embodiment 3 of the present invention.

FIG. 16 is a flowchart illustrating a method for determining an abnormality in the electric power steering device according to the fourth embodiment of the present invention.

FIG. 17 is a block diagram showing specific contents of a method of calculating a command current change rate in the electric power steering apparatus according to Embodiment 4 of the present invention.

FIG. 18 is a time chart showing operation contents of abnormality detection means in the electric power steering device according to Embodiment 5 of the present invention.

FIG. 19 is another example of a map for obtaining an offset value for generating an abnormality determination threshold value (a), and a time indicating a relationship between an abnormality determination threshold value and an indicated current value based on the offset value obtained from the map. It is a chart.

FIG. 20 is another example of a map for obtaining an offset value for generating an abnormality determination threshold value (a), and a time indicating a relationship between an abnormality determination threshold value and an indicated current value based on the offset value obtained from the map. It is a chart.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 2 steering shaft 3 torque sensor 4 speed reducer 5 steering shaft 6 universal joint 7 intermediate shaft 8 universal joint 9 pinion shaft 10 rack shaft 11a tie rod 11b tie rod 12 electric motor 13 control unit 14 vehicle speed sensor 15 ignition switch 16 battery L drive power supply Line P Power element

Claims (7)

[Claims] 1. A motor driving device comprising: a motor for applying a rotational force to a driven portion; and a drive circuit for outputting a drive instruction current to the motor, wherein an abnormality of the drive circuit is determined according to the drive instruction current. Threshold value setting means for setting a threshold value; current detection means for detecting an actual current actually input to the electric motor; actual current detected by the current detection means being set by the threshold value setting means An abnormality detection means for detecting an abnormality in the drive circuit when the abnormality is equal to or less than the abnormality determination threshold value. 2. A torque sensor for detecting a torque acting on a steering shaft; an electric motor for applying a steering assist force to the steering shaft; A drive circuit that outputs a drive instruction current; a threshold setting unit that sets an abnormality determination threshold value of the drive circuit according to the drive instruction current; a current that detects an actual current that is actually input to the electric motor Detection means; and abnormality detection means for detecting an abnormality in the drive circuit when the actual current detected by the current detection means is equal to or less than the abnormality determination threshold value set by the threshold value setting means. An electric power steering device characterized by the above-mentioned. 3. The drive circuit according to claim 2, wherein the abnormality detection means detects an abnormality in the drive circuit when the actual current detected by the current detection means remains below the abnormality determination threshold value set by the threshold value setting means for a predetermined time. The electric motor driving device according to claim 1, wherein the electric power steering device according to claim 2 is configured to detect the electric power steering. 4. The threshold setting means variably sets the abnormality determination threshold so that the difference between the drive instruction current and the actual current is smaller when the drive instruction current is small than when the drive instruction current is large. The electric motor drive device or the electric power steering device according to any one of claims 1 to 3, wherein the electric motor drive device or the electric power steering device is configured to be driven. 5. The threshold setting means variably sets the abnormality determination threshold so that the difference between the drive instruction current and the actual current is larger when the drive indicating current is smaller than when it is larger. The electric motor drive device or the electric power steering device according to any one of claims 1 to 3, wherein the electric motor drive device or the electric power steering device is configured to be driven. 6. A command current change rate calculation means for calculating a change rate of the drive command current, and detecting the abnormality when the change rate of the drive command current calculated by the command current change rate calculation means is a predetermined value or more. An electric motor driving device or an electric power steering device according to any one of claims 1 to 5, further comprising an abnormality detection prohibiting unit that prohibits abnormality detection in the means. 7. The abnormality detection means detects an abnormality in the drive circuit also when the actual current detected by the current detection means exceeds a preset upper threshold regardless of the drive instruction current. The electric motor driving device or the electric power steering device according to any one of claims 1 to 6, wherein