JP2003348884A - Current detector and controller using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current detector where detection accuracy when detecting a weak current is improved without raising the performance on a calculation side. <P>SOLUTION: Current detection circuits 40-44 output signals corresponding to the amount of the flowing current to a motor 24 which is so feedback- controlled that the amount of the current which actually flows agrees with a target amount of the current. A U-phase of the motor 24 is provided with a large current detection circuit 40 which can A/D converts a maximum amount of the current to a voltage of a specified range, and a small current detection circuit 41 which A/D converts only a weak current close to '0' to a voltage of a specified range. If an absolute value of the amount of the current flowing in the U-phase of the motor 24 exceeds a prescribed value ω, a large current detection value by the large current detection circuit 40 is set as a detection current. If an absolute value of the amount of the current flowing the U-phase of the motor 24 is less than the prescribed value γ, a small current detection value by the small current detection circuit 41 is set as a detection current. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detection device and a control device using the current detection device. It relates to the control device used.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Utility Model Application Laid-Open No. HEI 3-11247.
As disclosed in Japanese Unexamined Patent Application Publication No. 2 (1999) -1995, there is known a current detection device including a current detection circuit for detecting an amount of current flowing through a motor. This device detects the amount of current flowing on one path connected to a motor using one current detection circuit. That is, regardless of the magnitude of the current flowing through the motor, the current amount is detected with a constant resolution enough to detect the current amount within the desired current detection range. And the motor is
Based on the detected current amount, feedback control is performed so that the actual current amount matches the target current amount.

[0003]

However, in the above-described conventional current detecting device, the amount of current flowing on one path connected to the motor is detected at a fixed resolution, so that the current amount is large when the current amount is large. Can accurately detect the amount of current, but if the amount of current is a minute current near "0", the detection accuracy of the minute current may decrease. For this reason, in the above-mentioned conventional current detection device,
When a minute current flows, the controllability of the current feedback of the motor is deteriorated, and the torque ripple and the shaft vibration of the motor are generated.

In order to avoid such inconvenience and maintain high detection accuracy of a minute current of a motor, the performance of a calculation side (for example, a microcomputer) for calculating a current amount based on an output value of a current detection circuit must be improved. Can be considered. However, in such a configuration, the cost is increased due to the high performance, so that it is difficult to improve the detection accuracy of the current flowing through the motor with a low-cost system.

The present invention has been made in view of the above points, and it is possible to improve the detection accuracy when detecting a minute current flowing to an object such as a motor without increasing the performance on the calculation side. An object of the present invention is to provide a current detection device and a control device using the current detection device.

[0006]

The above object is achieved by the present invention.
As described in the above, a first current detection circuit capable of detecting a current flowing through the object within a region equal to or less than a first predetermined value, and a second predetermined current flowing through the object being smaller than the first predetermined value The first value that can be detected in an area equal to or less than the value.
Having a higher resolution than that of the current detection circuit of FIG.
A current detection circuit, and a current detection circuit whose detection value is used as a current amount of the target, the first current detection circuit when a current flowing through the target exceeds the second predetermined value, The present invention is achieved by a current detection device including: detection circuit setting means for setting the second current detection circuit when the current flowing through the object is equal to or less than the second predetermined value.

In the present invention, when the amount of current flowing through the object exceeds a second predetermined value, a first current detection circuit capable of detecting a current equal to or less than a first predetermined value larger than the second predetermined value. On the other hand, when the detected value is less than or equal to the second predetermined value, the amount of current flowing through the object is smaller than that of the first current detection circuit which can detect a current equal to or less than the second predetermined value. The detection value of the second current detection circuit having a high resolution is used as the target current amount. In such a configuration, when the target current amount is equal to or less than the second predetermined value, the current amount is detected with higher resolution than when the target current amount exceeds the second predetermined value. For this reason, the detection accuracy of the current when a minute current equal to or smaller than the second predetermined value flows to the target is improved. Further, in such a configuration, in order to improve the detection accuracy of the target minute current,
It is not necessary to increase the performance of the calculation side that calculates the current amount based on the output value of the current detection circuit.

By the way, the difference between the current value obtained by the first current detection circuit and the current value obtained by the second current detection circuit is at most only an error of the detection accuracy when both circuits are normal. If an abnormality occurs in at least one of the two circuits, the detection accuracy becomes larger than the error of the detection accuracy.

Therefore, as described in claim 2, in the current detection device according to claim 1, a parameter based on a detection value of the first current detection circuit and a parameter based on a detection value of the second current detection circuit. And an abnormality detecting means for detecting an abnormality in the first and second current detection circuits by comparing the first and second current detection circuits, it is possible to accurately detect an abnormality in the detection of the first and second current detection circuits. it can.

The second current detection circuit can detect only a current amount in a range equal to or less than a second predetermined value.
Cannot be detected.

Therefore, as described in claim 3, in the current detecting device according to claim 2, the abnormality detecting means includes:
If the abnormality detection processing is performed in a situation where the current flowing through the object is equal to or less than the second predetermined value, the abnormality detection processing of the current detection circuit is performed when the current amount exceeds the second predetermined value. Therefore, it is possible to prevent the accuracy of the abnormality detection of the current detection circuit from lowering.

In these cases, as described in claim 4,
4. The current detection device according to claim 1, wherein the target is a polyphase motor, and the first and second current detection circuits are respectively provided for each phase of the polyphase motor. 5. It may be provided correspondingly and detect the amount of current flowing through the phase.

Further, as described in claim 5, claim 1 is
5. The current detection device according to claim 4, wherein the object is feedback-controlled such that an amount of current actually flowing matches a target amount of current.

Furthermore, as described in claim 6, claim 1
6. The current detection device according to claim 5, wherein the target is an auxiliary motor that is provided in a steering system of the vehicle and that generates an assist force with respect to a steering operation performed by a driver.

By the way, if an abnormality occurs in the second current detection circuit, it becomes impossible for the second current detection circuit to detect a current equal to or less than a second predetermined value. The second predetermined value is a value smaller than the first predetermined value that is the upper limit of the detectable area of the first current detection circuit. In this regard, even if it is impossible to detect the current equal to or less than the second predetermined value using the second current detection circuit, it is possible to detect the current using the first current detection circuit. is there.

Therefore, as set forth in claim 7, in the current detection device according to claim 1, the detection circuit setting means determines whether the second current detection circuit is abnormal when the abnormality of the second current detection circuit is detected. If the first current detection circuit is set as a current detection circuit whose detected value is used as the target current amount even when the flowing current is equal to or less than the second predetermined value, Even when the current detection circuit is abnormal, a very small current equal to or less than the second predetermined value can be detected.

Further, in the configuration in which the predetermined control is executed based on the detection value of the current detection circuit set by the detection circuit setting means, if an abnormality occurs in the second current detection circuit, the current is reduced to the first value. If it is equal to or less than the predetermined value of 2, the second
It is impossible to execute the predetermined control based on the detection value of the current detection circuit.

Therefore, in a control device using the current detection device according to any one of claims 1 to 6, the detection value of the current detection circuit set by the detection circuit setting means is provided. Control execution means for executing a predetermined control based on the control signal. When the abnormality of the second current detection circuit is detected, the control execution means changes the current flowing through the object to the second predetermined value. Even in the following case, if the predetermined control is executed based on the detection value of the first current detection circuit, even if an abnormality of the second current detection circuit occurs, The predetermined control can be continued using the first current detection circuit when a minute current equal to or less than the value flows.

Further, if an abnormality occurs in the first current detection circuit, it becomes impossible for the first current detection circuit to detect a current equal to or less than a first predetermined value. On the other hand, even in such a case, when the second current detection circuit is normal, a current equal to or less than the second predetermined value can be detected using the second current detection circuit. In this regard, when such a situation occurs, if the predetermined control is limited to the detectable region of the second current detection circuit, the control can be continued.

According to a ninth aspect of the present invention, in a control device using the current detection device according to any one of the first to sixth aspects, the detection value of the current detection circuit set by the detection circuit setting means is provided. Control execution means for executing a predetermined control based on the control signal, wherein the control execution means executes the predetermined control when the abnormality of the first current detection circuit is detected. If it is to be limited to an area not more than the second predetermined value, which is a detectable area of
Even if an abnormality occurs in the first current detection circuit, the predetermined control can be continued within a region equal to or less than the second predetermined value.

[0021]

FIG. 1 is a block diagram of a system having a current detecting device according to an embodiment of the present invention. The system of the present embodiment is a system of an electric power steering device (hereinafter, simply referred to as a steering device) 10 mounted on a vehicle. The steering device 10 is a rack and pinion type steering device, and includes a steering shaft 12 connected to a steering wheel (not shown) operated by a driver to steer the vehicle, and a pinion 14 provided on the steering shaft 12. And a rack 16 that engages with the pinion 14. Steering wheels (not shown) are connected to both ends of the rack 16 via ball joints, tie rods, and knuckle arms.

In the above configuration, when the steering wheel is operated, the pinion 14 is rotated accordingly, and the rack 16 is displaced in the longitudinal direction along the vehicle width direction. When the rack 16 is displaced along the vehicle width direction, the tie rod and the knuckle arm operate, and the wheels are steered.
That is, the steering device 10 has a function of converting the rotational motion of the pinion 14 into the linear motion of the rack 16 in the longitudinal direction, thereby turning the wheels by the driver's steering operation.

In this embodiment, the steering device 10
Is a vehicle speed-sensitive power steering device that assists a steering torque required when a driver turns a wheel in order to reduce a burden of a steering operation by the driver using a motor described later. Steering shaft 1
2, a torque sensor 20 is provided. The torque sensor 20 outputs a signal corresponding to a steering torque T applied to a steering wheel by a driver's steering operation. The output signal of the torque sensor 20 is supplied to an electronic control unit (hereinafter, referred to as ECU) 22.
The ECU 22 detects the steering torque T applied to the steering wheel based on the output signal of the torque sensor 20.

The steering device 10 also includes a rack 1
6 is provided with a three-phase AC brushless motor (hereinafter simply referred to as a motor) 24 that engages with the motor 6. The motor 24 includes a stator 2 fixed to a housing on the vehicle body side covering the rack 16.
6 and a rotor 28 which is a tubular member that engages with and surrounds the rack 16 and is rotatably supported by a housing via a bearing. Stator 2
Reference numeral 6 includes a coil and a core. Rotor 2
8 is provided with a magnet. Stator 2
When the rotor 28 is rotated by the excitation of 6, the rack 16 is displaced in the longitudinal direction along the vehicle width direction. That is, in the steering device 10, the motor 24 generates a torque for displacing the rack 16 in the vehicle width direction by its rotational drive.

An ECU 22 is connected to each of the U, V, and W phases of the motor 24. ECU 22
Has a drive circuit 32 that supplies power to each phase of the motor 24 using the battery 30 as a power supply. The drive circuit 32 has three pairs of power switching elements corresponding to each phase. Each power switching element of the drive circuit 32 is PWM-driven by the ECU 22 and applies a voltage to the motor 24.

A vehicle speed sensor 34 is connected to the ECU 22. The vehicle speed sensor 34 outputs a pulse signal at a cycle corresponding to the speed of the vehicle. The ECU 22 controls the vehicle speed sensor 3
4, the vehicle speed SPD is detected based on the output signal. ECU
22 has an assist current calculation unit 36, and uses the assist current calculation unit 36 to determine the assist force to be applied to the rack 16 based on the relationship between the steering torque T by the torque sensor 20 and the vehicle speed SPD by the vehicle speed sensor 34. The motor 24 is operated so that the assist force is applied to the rack 16.
Calculates the target assist current amount necessary to drive.

The ECU 22 includes a drive circuit 32 and a motor 24
Current detection circuits 40 to 44 provided corresponding to the respective current paths between the U, V, and W phases. Each of the current detection circuits 40 to 44 has a current amount flowing through a current path corresponding to itself, that is,
And outputs a signal corresponding to the amount of current iu, iv, iw flowing through each phase. In this embodiment, the current flowing from the drive circuit 32 to the motor 24 is defined as a positive current, and the current flowing in the reverse direction is defined as a negative current.

Specifically, the current detection circuits 40 and 41
Analog current amount iu from-side to + side flowing in phase
And the current detection circuits 42 and 43 output +
, And the current detection circuit 44 converts the analog current amount iw flowing from the − side to the + side flowing in the W phase into a voltage in the range of “0” V to “5” V, for example. They are A / D converted and output. Current detection circuits 40, 4
2 and 44 each have a resolution enough to detect the maximum amount of current that can flow through the motor 24,
A / D conversion processing can be performed according to the amount of current from the maximum value on the minus side to the maximum value on the plus side. In addition, the current detection circuits 41 and 43 respectively output “0”.
The A / D converter has a resolution enough to detect a minute current equal to or less than a predetermined value in the vicinity, and performs A / D conversion corresponding to a current amount in a range narrower than the current detection range of the current detection circuits 40, 42, and 44 described above. It is configured so that processing can be performed. Hereinafter, the current detection circuits 40, 42, and 44 are referred to as large current detection circuits 40, 42, and 44, and the current detection circuits 41 and 43 are referred to as small current detection circuits 41 and 43, respectively.

The current detection circuits 40 to 44 include the motor 24
A three-phase to two-phase conversion circuit 4 for performing dq conversion in which a three-phase AC current and voltage are represented by two-axis DC in order to simplify the control method of
6 is connected. The steering device 10 includes a rotation angle sensor 48 provided on the motor 24. The rotation angle sensor 48 outputs a signal corresponding to the rotation angle position δ of the rotor 28 of the motor 24 with respect to the stator 26. The output signal of the rotation angle sensor 48 is supplied to the ECU 22. The ECU 22 detects the rotation angle position δ of the motor 24 based on the output signal of the rotation angle sensor 48.
The output signals of the current detection circuits 40 to 44 and the output signal of the rotation angle sensor 48 are both supplied to a three-phase to two-phase conversion circuit 46. The three-phase to two-phase conversion circuit 46 determines the rotor 2 based on the output signals of the current detection circuits 40 to 44.
Outputs 8 signal corresponding to the rotational angular position q-axis current according to [delta] I _q and the d-axis current I _d of.

A current feedback calculator 50 is connected to the assist current calculator 36 and the three-phase to two-phase converter 46. The output signal of the assist current calculation unit 36 and the output signal of the three-phase to two-phase conversion circuit 46 are both supplied to the current feedback calculation unit 50. ECU 22
Performs feedback control on the motor 24 so that the amount of current flowing through each phase of the motor 24 matches the target assist current amount. Current feedback computation unit 50, a three-phase - a q-axis current I _q and the d-axis current I _d by two-phase conversion circuit 46 by comparing a target q-axis current and d-axis current according to the assist current calculation unit 36, which Is calculated based on the deviation of the current.

The current feedback calculation unit 50 is connected to a two-phase to three-phase conversion circuit 52 for performing an inverse dq conversion of two-axis DC by three-phase AC voltage and current. The two-axis current command value by the current feedback calculation unit 50 and the output signal of the rotation angle sensor 48 are both supplied to the two-phase to three-phase conversion circuit 52. The two-phase to three-phase conversion circuit 52 includes:
Based on the output signal of the current feedback calculation unit 50, a signal corresponding to the three-phase alternating current according to the rotation angle position δ of the rotor 28 is output.

A PWM command unit 54 is connected to the two-phase to three-phase conversion circuit 52. The output signal of the two-phase to three-phase conversion circuit 52 is supplied to a PWM command unit 54. PWM
The command unit 54 sets each power switching element of the drive circuit 32 to PW based on the output signal of the two-phase to three-phase conversion circuit 52.
M drive is performed, and a voltage application to the motor 24 is commanded so that a target assist current flows through each phase of the motor 24.

In the above arrangement, when the driver operates the steering wheel, the motor 24 is driven so that an assist force corresponding to the steering torque T is applied to the rack 16. Specifically, the driving of the motor 24 is
The operation is performed such that the larger the steering torque T, the larger the assist force is generated. The assist force is a value corresponding to the vehicle speed SPD of the vehicle. Therefore, according to the steering device 10 of the present embodiment, it is possible to reduce the burden of the driver's steering operation using the motor 24.

By the way, if the amount of current flowing through each phase of the motor 24 is to be detected by one current detection circuit, the current detection circuit operates under the condition that the resolution for current detection is constant. In this state, the current from the minimum current (current amount = “0”) that can flow to the maximum current amount should be detected. Therefore, when the actual current amount is a minute current near “0”, The detection accuracy will be reduced. For this reason, in such a configuration, when a minute current flows, the controllability of the current feedback of the motor 24 deteriorates, and the torque ripple and the shaft vibration of the motor 24 occur.
The steering feeling for the driver's steering operation is reduced.

In order to avoid such inconvenience and maintain high detection accuracy of the minute current of the motor 24, it is conceivable to increase the resolution of the current detection circuit and improve the performance of the ECU 22. However, in such a configuration, the ECU
Since the cost associated with the high performance of the motor 22 is increased, it is difficult to improve the detection accuracy of the current flowing through the motor 24 with a low-cost system.

Therefore, the system according to the present embodiment employs the ECU 2
The second feature is that the detection accuracy of the minute current when the minute current flows is improved while reliably detecting the maximum amount of current that can flow through the motor 24 without increasing the calculation performance of Step 2. ing. Hereinafter, referring to FIG. 2 and FIG.
The features will be described.

FIG. 2 shows the current detection circuits 40 to 4 of this embodiment.
4 is a diagram illustrating the characteristics of FIG. In the present embodiment, the large current detection circuits 40, 42, and 44 correspond to current amounts from the maximum value on the minus side to the maximum value on the plus side that can flow in each phase of the motor 24, as shown in FIG. Then, the analog current amount is A / D converted to a voltage in the range of “0” V to the power supply voltage “5” V. On the other hand, as shown in FIG. 2, the small current detection circuits 41, 43 are respectively large current detection circuits 40, 42, 4.
4, the analog current amount is set to “0” V corresponding to a current amount from −γ to + γ smaller than the current detection range of No. 4 (where γ is a predetermined current amount smaller than the maximum value of the current flowing to the motor 24). A / D-convert to a voltage in the range of power supply voltage “5” V.

In such a configuration, the amount of current between -γ and + γ is, as shown in FIG.
The output values after A / D conversion by α2 and α44 are α1 and β
1, the output values after A / D conversion by the small current detection circuits 41 and 43 are α2 smaller than α1 and β2 larger than β1.
Appear within a relatively wide range between That is, the small-current detection circuits 41 and 43 are connected to the large-current detection circuits 40 and 4.
Higher resolution than that of 2,44, -γ and + γ
Can be converted into a voltage more finely than the large current detection circuits 40, 42, and 44 and output.

Therefore, in a situation where the amount of current flowing in the U-phase or V-phase of the motor 24 is a value between -γ and + γ, the A / D output value of the small current detection circuits 41 and 43 is used. If the amount of the current is detected by using the small current from −γ to + γ in the motor 24, the detection accuracy of the small current is determined by the A / A by the large current detection circuits 40 and 42.
It is possible to improve the detection as compared with the case where the detection is performed based on the D output value. In this case, the detection accuracy of the minute current flowing through the motor 24 can be improved without increasing the calculation performance of the ECU 22. In a situation where the amount of current flowing in the U phase or the V phase of the motor 24 is not a value between -γ and + γ, the A / D by the large current detection circuits 40 and 42 is used.
If the current amount is detected based on the output value,
Even if the maximum current that can flow through the motor 24 flows, the amount of the current can be reliably detected. Therefore,
According to such a configuration, it is possible to improve the detection accuracy of the minute current while reliably detecting the maximum amount of current that can flow through the motor 24 without increasing the calculation performance of the ECU 22.

FIG. 3 shows a flowchart of an example of a control routine executed by the ECU 22 in the present embodiment to realize the above functions. The routine shown in FIG. 3 is a routine that is repeatedly started every predetermined time (for example, 5 ms). When the routine shown in FIG. 3 is started, first, the process of step 100 is executed.

In step 100, the large current detection circuit 4
A process is executed to capture the output values after A / D conversion by 0 and 42 and the output values after A / D conversion by small current detection circuits 41 and 43, respectively.

In step 102, the above-mentioned step 100
A / D by small current detection circuits 41 and 43 taken in
It is determined whether or not the output value is between predetermined value α2 and predetermined value β2. The predetermined value α2 is determined by the small current detection circuit 4.
A / D output value corresponding to the minimum current (= -γ) to be detected by the small current detection circuits 41 and 43, and the predetermined value β2 is the maximum current (= + γ) to be detected by the small current detection circuits 41 and 43.
Is an A / D output value corresponding to. As a result, when an affirmative determination is made, the process of step 104 is executed next. On the other hand, if a negative determination is made, then step 1
Step 06 is executed.

In step 104, the small current detection circuit 4
2 based on the A / D output values by
The amount of current grasped according to the map (hereinafter, small current detection
F (A / D output value)) is the U phase of the motor 24.
Or the detected current i in the V phase _t(T = u, v)
Is performed. The processing of step 104 is
After that, the current feedback control of the motor 24 is performed.
In the control, detection by the detection circuits 40 and 42 for large current is performed.
Instead of the currents iu and iv, detection circuits 41 and 43 for small currents
, The detected currents iu and iv are used.

In step 106, based on the A / D output values from the large current detection circuits 40 and 42,
The current amount (hereinafter, referred to as a large current detection value; g (A / D output value)) grasped according to the map shown in FIG.
Process of setting the detection current i _t in the U phase or the V phase is executed. After the process of step 104 is performed, the current feedback of the motor 24 is followed by the detection currents iu,
Instead of iv, the currents iu and iv detected by the large current detection circuits 40 and 42 are used. Step 10
When the processing of step 4 or 106 ends, the current routine ends.

According to the routine shown in FIG. 3, the A / D output values of the small current detection circuits 41 and 43 are α2 and β2.
And a small current between −γ and + γ flows through the motor 24, the A of the small current detection circuits 41 and 43
The detection value for small current based on the / D output value can be set as the detection current, while the detection circuits 41 and 43 for small current can be set.
If the A / D output value is smaller than α2 or larger than β2, and the absolute value of the current flowing through the motor 24 exceeds γ, the large current detection circuit 40, 42 The detection value can be set as a detection current.

As described above, the small current detection circuits 41, 43
Has a higher resolution than those of the large current detection circuits 40 and 42, and converts the amount of current between -γ and + γ into a voltage finer than the large current detection circuits 40, 42 and 44. I do. For this reason, according to the above configuration, when a large current flows through the motor 24, the amount of the current can be reliably detected by using the large current detection circuits 40 and 42, and the motor 24 is supplied with -γ. When a small current of + γ flows, the detection accuracy of the small current can be improved as compared with the case where detection is performed based on the A / D output value by the large current detection circuits 40 and 42.

For this reason, the steering apparatus 1 of the present embodiment
According to 0, even if a minute current flows through the motor 24, the minute current can be detected with high accuracy, so that the controllability of the current feedback can be maintained at a high level. In addition, it is possible to avoid the occurrence of vibration of the shaft and the shaft, and to prevent a decrease in the steering feeling with respect to the driver's steering operation.

In the configuration of the present embodiment, the small current detection circuits 41 and 43 having relatively high resolution are provided together with the large current detection circuits 40 and 42 as current detection circuits for detecting the current flowing through the motor 24. In order to improve the detection accuracy of a minute current, the current detection circuits 40 to 4
EC for converting the output value after A / D conversion by step 4 into a current amount
It is not necessary to increase the performance of U22 on the microcomputer side.
Therefore, according to the present embodiment, it is possible to improve the detection accuracy of a minute current when the minute current flows through the motor 24 without increasing the performance of the microcomputer of the ECU 22.

In the present embodiment, while a large current detection circuit 44 is provided in the W phase of the motor 24,
No detection circuit for small current is provided. That is, the current flowing in the W phase of the motor 24 is detected using the large current detection circuit 44, but is not detected using the small current detection circuit unlike the U phase and V phase currents.

FIG. 4 is a diagram showing a schematic configuration of the drive circuit 32 and the motor 24 provided in the system of this embodiment. FIG. 5 is a diagram showing the relationship between the rotation angle position δ of the rotor 28 of the motor 24 and the current amounts iu, iv, iw flowing in each phase. In the system of the present embodiment,
Since the motor 24 is a three-phase AC brushless motor as described above, the three stator coils of the motor 24
They are arranged at 20 ° intervals. At this point, as shown in FIGS. 4 and 5, at the same time, that is, at the same rotational angle position δ, the sum of the current amounts flowing in the U, V, and W phases is given by the following equation (1).
It is zero as shown in FIG. The state in which the sum of the current amounts is zero is invariant regardless of the rotation angle position δ.

Iu + iv + iw = 0 (1) Therefore, if the current amounts of the two phases at the same timing are detected without detecting all the current amounts flowing through the respective phases of the motor 24, The remaining one-phase current amount at that timing can be detected according to the above equation (1). In this case, it is necessary to provide a current detection circuit for detecting a current in the two phases of the motor 24, but it is not necessary to provide a current detection circuit in the remaining one phase.

Therefore, in this embodiment, the amount of current iu flowing through the U-phase of the motor 24 detected by using the large current detection circuit 40 or the small current detection circuit 41 and the large current detection circuit 42 or small current Based on the current amount iv flowing through the V phase detected by the current detection circuit 43, the current amount iw flowing through the W phase is calculated according to the above equation (1). In this case, the calculated W-phase current amount iw can be a value in consideration of the U-phase current amount iu and the V-phase current amount iv by the small current detection circuits 41 and 43. Therefore, in the present embodiment, even when the small current detection circuit is not provided in the W phase of the motor 24, it is possible to accurately grasp the minute current when the minute current flows in the W phase. . In this regard, it is possible to improve the detection accuracy of a minute current while reducing the number of parts and the cost.

As described above, in the W phase of the motor 24,
A large current detection circuit 44 is provided. ECU 22
Detects the amount of current flowing in the W phase based on the output signal of the large current detection circuit 44. In this regard, the large current detection circuit 4
0,42, U-phase current amount iu and V-phase current amount i
v, and the W-phase current amount iw calculated according to the above equation (1) and the W detected using the large current detection circuit 44.
By comparing with the current amount iw of the phase, a detection abnormality occurring in at least one of the large current detection circuits 40, 42, and 44 can be detected. If the difference in the amount of current generated between them is equal to or greater than a predetermined value, the large current detection circuits 40 and 4
It can be determined that a detection abnormality has occurred in at least one of the circuits 2, 44, and if the difference is smaller than a predetermined value, it can be determined that no detection abnormality has occurred in any of the circuits 40, 42, 44.

Therefore, the system of the present embodiment uses the W-phase current calculated according to the above equation (1) based on the U-phase current iu and the V-phase current iv by the large current detection circuits 40 and 42. The amount iw is compared with the W-phase current amount iw detected using the large current detection circuit 44 to determine whether or not at least one of the large current detection circuits 40, 42, and 44 has a detection abnormality. Detect.

By the way, both the large current detection circuit 40 and the small current detection circuit 41 detect the current flowing in the U phase of the motor 24. Both the large current detection circuit 42 and the small current detection circuit 43 detect the current flowing in the V phase of the motor 24. Therefore, the difference between the current amount by the large current detection circuit 40 and the current amount by the small current detection circuit 41, and
The difference between the amount of current by the large-current detection circuit 42 and the amount of current by the small-current detection circuit 43 is both current detection circuits 40 to 4
There is almost no case where 3 is normal, and at most there is only an error in the detection accuracy. On the other hand, when the difference between them is greater than the error of the detection accuracy, at least one of the large current detection circuits 40 and 42 and the small current detection circuits 41 and 43 is used. 43 can be determined to have a detection abnormality.

Therefore, the system according to the present embodiment uses the current amount by the large current detection circuits 40 and 42 and the small current detection circuit 4
The second feature is that the detection abnormality of the current detection circuits 40 to 43 is detected by comparing the current amounts of the current detection circuits 1 and 43 with each other. Hereinafter, the characteristic portion will be described with reference to FIG.

FIG. 6 shows a flowchart of an example of a control routine executed by the ECU 22 in this embodiment to detect a detection abnormality of the current detection circuits 40 to 43. The routine shown in FIG. 6 is a routine that is repeatedly started at predetermined time intervals. When the routine shown in FIG. 6 is started, first, the process of step 200 is executed.

In step 200, the large current detection circuit 4
It is determined whether or not the absolute value of the current amount (detection value for large current) grasped based on the A / D output values of 0 and 42 is equal to or smaller than γ. As a result, when an affirmative determination is made, a current that can be detected even by using the small current detection circuits 41 and 43 is flowing through the motor 24. Next, the process of step 202 is performed.

In step 202, the small current detection circuit 4
The amount of current (detection value for small current) grasped based on the A / D output values of the first and third detection circuits and the A of the detection circuits 40 and 42 for the large current.
The difference from the large current detection value based on the / D output value is a predetermined value A
It is determined whether or not this is the case. Note that the predetermined value A is the minimum current amount difference at which it can be determined that an abnormality has occurred in the current detection circuits 40 to 43. As a result, if a positive determination is made, the process of step 204 is performed next. on the other hand,
If a negative determination is made, then the process of step 208 is performed.

In step 204, the abnormality counter CNT
Is incremented by "1". The abnormality counter CNT is a counter for counting the duration time in which the condition of step 202 is satisfied. In step 206, the count value of the abnormality counter CNT is
It is determined whether or not NT0 has been reached. The predetermined value C
NT0 is the minimum time during which it can be determined that an abnormality has occurred in the current detection circuits 40 to 43 without fail. As a result, CN
If it is determined that T ≧ CNT0 is not satisfied, the process of step 200 is executed again. On the other hand, CNT ≧
If it is determined that CNT0 is established, the process of step 210 is executed next.

On the other hand, if a negative determination is made in step 200 that | the detection value for large current | ≦ γ is not satisfied, the current that cannot be detected using the detection circuits 41 and 43 for small current is detected. This means that the current flows to the motor 24. Therefore, when such a determination is made, the process of step 208 is executed next. In step 208, processing for resetting the abnormal counter CNT to "0" is executed. When the process of step 208 is completed, the current routine is completed.

In step 210, it is determined that an abnormality has occurred in the current detection circuits 40 to 43, the current feedback control of the motor 24 is stopped, and the assist control for assisting the steering operation is stopped. An abnormality determination process for notifying the user with a speaker or voice guidance is performed. When the process of step 210 ends, the current routine ends.

According to the routine shown in FIG. 6, the large current detection circuit 4 provided in the same phase of the motor 24
If the difference between the detected values for the large current and the small current by the 0, 42 and small current detection circuits 41, 43 is within a desired range, an abnormal detection has occurred in the current detection circuits 40 to 43. As usual, the current feedback control of the motor 24 is executed based on the detected values as usual,
If the difference between the detected value for the large current and the detected value for the small current is larger than a desired range, it is determined that a detection abnormality has occurred in the current detection circuits 40 to 43 in that phase, and the abnormality is determined. Processing can be performed.

If the current flowing through the motor 24 is within the current detection range of the small current detection circuits 41 and 43, and if all of the current detection circuits 40 to 43 are normal, the large current detection circuit 40 The difference between the amount of current and the amount of current by the small-current detection circuit 41, and the difference between the amount of current by the large-current detection circuit 42 and the amount of current by the small-current detection circuit 43 are almost nonexistent. It is only an error.
Therefore, according to the present embodiment, a detection abnormality occurring in the current detection circuits 40 to 43 can be accurately detected.

Further, the current detection circuit 40
In the case where the detection abnormality is detected, the current feedback control of the motor 24 is stopped as an abnormality determination processing, the assist control for assisting the steering operation is stopped, and the driver is notified by a speaker or sound. You will be notified by information. For this reason, in the present embodiment, it is possible to prevent the assist control from being erroneously controlled due to the detection abnormality of the current detection circuits 40 to 43, and to determine that the assist control is not performed by the driver. Thus, it is possible to promptly take measures against abnormal detection of the current detection circuits 40 to 43.

Furthermore, in the present embodiment, the small current detection circuits 41 and 43 have only a current detection range for detecting a minute current near the "0" (not more than the predetermined value γ). A current amount exceeding γ cannot be detected. That is, when a current amount exceeding the predetermined value γ flows through the motor 24, the A / D output value of the small current detection circuits 41 and 43 is “0” V or “5” regardless of the magnitude of the current amount. It is maintained near V. Therefore, when a current exceeding the predetermined value γ flows through the motor 24, the detection abnormality of the current detection circuits 40 to 43 according to the above-described method is determined by using the small current detection value obtained based on the A / D output value. If it is assumed that the detection process is performed, the accuracy of the detection process is reduced.

Therefore, in the present embodiment, the current detection circuit 40 based on the comparison between the small current detection value and the large current detection value.
The detection processing of whether or not the detection abnormalities of (1) to (43) have occurred is performed when the amount of current flowing through the motor 24 is small.
, Specifically, only when the current value is equal to or smaller than the predetermined value γ (when the affirmative determination is made in step 200 of the routine shown in FIG. 6), but not when the current value exceeds the predetermined value γ. . For this reason, according to the system of the present embodiment, the accuracy of the detection processing for determining whether or not the detection abnormality of the current detection circuits 40 to 43 has occurred by comparing the small current detection value and the large current detection value is reduced. It is possible to prevent the situation.

In the above embodiment, the large current detection circuits 40 and 42 correspond to the "first current detection circuit" described in the claims, and the small current detection circuits 41 and 43 correspond to the claims. In the "second current detection circuit" described in the range, the maximum current value of the current detection range of the large current detection circuits 40 and 42 is replaced by the predetermined value γ in the "first predetermined value" described in the claims. Is the "second predetermined value" described in the claims,
Each is equivalent.

In the above embodiment, the ECU 2
2 are steps 104 and 10 in the routine shown in FIG.
By executing the processing of step 6, the "detection circuit setting means" described in the claims is executed according to the processing results of steps 202 to 206 in the routine shown in FIG.
The “abnormality detecting means” described in the claims is realized by executing the processing of No. 10.

In the above embodiment, the motor 24 for detecting the current is a three-phase brushless motor. However, the present invention is not limited to the three-phase motor, but may be applied to a two-phase motor or a multi-phase motor having four or more phases. It is possible, and it is also possible to apply not only to a brushless motor but also to a motor with a brush.

Further, in the above-described embodiment, the current of the motor 24 used in the electric power steering device 10 mounted on the vehicle is detected. However, the present invention is not limited to the electric power steering device 10. It is also possible to apply to the motor of the use.

In the above embodiment, the motor 2
In the routine shown in FIG. 3, the A / D output values of the small current detection circuits 41 and 43 are determined by determining whether the amount of current flowing through the small current 4 is a very small current between -γ and + γ. 6, and in the routine shown in FIG. 6, the current amount (that is, the large current detection value) itself, which is grasped from the A / D output values of the large current detection circuits 40 and 42, is itself determined. -Γ and +
γ, but the current amount (that is, the small current detection value) itself obtained from the A / D output values of the small current detection circuits 41 and 43 is −
The detection may be performed based on whether or not it is between γ and + γ, or the A /
The determination may be performed based on whether the D output value is between α1 and β1. Further, such determination may be made using the same parameters in the routine shown in FIG. 3 and the routine shown in FIG.

Further, in the above-described embodiment, the detection of whether or not the detection abnormality has occurred in the current detection circuits 40 to 43 is determined by the A / D output values of the large current detection circuits 40 and 42. Detection value for current and detection circuits 41 and 43 for small current
The comparison is made by comparing with the small current detection value obtained from the A / D output value of the above, but the A / D output values may be compared with each other. In this case, the threshold value of the difference between the two for performing the abnormality determination fluctuates according to the amount of current, and the error value is changed to an appropriate value from “0” to (α1−α2) or (β2−β1). Is added.

Further, in the above-described embodiment, it is detected whether or not the current detection circuits 40 to 43 have a detection abnormality by comparing the detected value for the small current with the detected value for the large current. When it is determined that the detection abnormality has occurred, abnormality determination processing such as suspension of the current feedback control of the motor 24 is performed. However, under the situation where the abnormality is detected, the small current detection circuit 41, 43
If the A / D output value is maintained and fixed at “0” V or “5” V, a large current detection value based on the A / D output value of the large current detection circuits 40 and 42 is used. The current feedback and the assist control of the motor 24 may be continued as usual.

That is, the A / D output values of the small current detection circuits 41 and 43 are set to the ground voltage “0” V or the power supply voltage “5” V
If the path is maintained and fixed, it can be determined that a disconnection or short circuit has occurred in the path. When such an abnormality occurs, the detection circuits 41 and 43 for small current are used to change from −γ to + γ.
It is impossible to accurately detect the amount of current up to this point.
On the other hand, the large-current detection circuits 40 and 42 calculate the current detection range of the small-current detection circuits 41 and 43 from the maximum value on the minus side that can flow through the motor 24 completely including the region from −γ to + γ. This circuit sets the current detection range up to the maximum value on the side. For this reason, as described above, the detection circuit 41 for small current,
43, the current detection range is -γ
Detection circuits 40 and 42 for detecting large currents from
It is possible to detect using.

Therefore, when a detection abnormality occurs in the small current detection circuits 41 and 43, the large current detection circuit 4
Using 0 and 42, the amount of current flowing through the motor 24 is detected. According to this configuration, the small current detection circuits 41 and 43
, A small current from -γ to + γ can be detected. As a result, even if the amount of current flowing through the motor 24 is a value from -γ to + γ, a large current detection circuit The current feedback control and the assist control of the motor 24 can be continued based on the detection values detected by using the values 40 and 42. Therefore, according to such a configuration, it is possible to avoid a situation in which the above control is not performed at all due to a detection abnormality of the small current detection circuits 41 and 43, and
It is possible to suppress the driver's steering operation burden from becoming excessive.

In this case, the ECU 22 continues the current feedback control and the assist control of the motor 24 based on the detection value detected by using the detection circuits 40 and 42 for large currents. 8 implements the “control executing means”.

In the above embodiment, the motor 2
Four large-current detection circuits 40, 42, and 44 for detecting the amounts of current flowing in the U, V, and W phases, respectively, are provided. Since the sum of the currents flowing in each phase of the motor 24 is always zero, the A / D of the large current detection circuits 40, 42, 44
If the detection circuits 40, 42, and 44 are operating normally, the sum of the detection values for the large current based on the output value can be calculated as described in (1) above.
It should always be "0" according to the equation. That is, when the sum of the detected values for the large current is not zero, it can be determined that at least one of the detection circuits 40, 42, and 44 has a detection abnormality. When such an abnormality occurs, it becomes impossible to accurately detect the motor current using the large current detection circuits 40, 42, and 44. On the other hand, the small current detection circuit 4
1, 43 has a current detection range of a current amount from -γ to + γ. Therefore, if the amount of current flowing to the motor 24 is the amount of current from -γ to + γ, it is possible to detect the current.

Therefore, the large current detection circuits 40, 42, 4
When the detection abnormality occurs in the motor 4, the target assist current amount to be passed to the motor 24 is reduced by the small current detection circuits 41 and 43.
The target assist force to be applied to the rack 16 in the assist control is limited to a predetermined range so that the target assist force falls within the range of -γ to + γ, which is the detectable range of the above. In this case, the amount of current flowing through the motor 24 is prevented from increasing beyond the range from -γ to + γ. For this reason, according to this configuration, even when a detection abnormality occurs in the large current detection circuits 40, 42, and 44, the current feedback control and the assist control are continued using the small current detection circuits 41 and 43. Can be. For this reason, according to this configuration, it is possible to avoid a situation in which the above control is not performed at all due to a detection abnormality of the large current detection circuits 40, 42, and 44.
It is possible to suppress the driver's steering operation burden from becoming excessive.

In this case, the ECU 22 continues the current feedback control and the assist control of the motor 24 based on the detection value detected by using the detection circuits 41 and 43 for small currents. 9 is realized.

[0081]

As described above, according to the first and fourth to sixth aspects of the present invention, the predetermined value can be set to the target without increasing the performance of the calculation side for calculating the amount of current based on the output value of the current detection circuit. It is possible to improve the current detection accuracy when the following minute current flows.

According to the second aspect of the present invention, it is possible to accurately detect a detection abnormality of the current detection circuit including the large current detection circuit and the small current detection circuit.

According to the third aspect of the present invention, when the current amount of the target exceeds a predetermined value, the abnormality detection processing of the current detection circuit is not performed, so that the accuracy of the abnormality detection of the current detection circuit is reduced. Can be prevented.

According to the seventh aspect of the present invention, the first current detection circuit is used even when an abnormality occurs in the second current detection circuit capable of detecting a current in a region equal to or less than the second predetermined value. A small current equal to or less than the second predetermined value can be detected.

According to the eighth aspect of the present invention, even when an abnormality occurs in the second current detection circuit capable of detecting a current in a region equal to or less than the second predetermined value, the target is kept at the second predetermined value or less. When the minute current flows, predetermined control can be continued using the first current detection circuit.

According to the ninth aspect of the present invention, the first
If an abnormality occurs in the current detection circuit of
It is possible to continue within a region that is equal to or less than a second predetermined value, which is a detectable region of the second current detection circuit.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a system including a current detection device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating characteristics of a current detection device included in the system of the present embodiment.

FIG. 3 is a flowchart of a control routine executed to determine a current detection circuit that uses a detected value as a current amount of a motor in the embodiment.

FIG. 4 is a diagram illustrating a schematic configuration of a drive circuit and a motor included in the system of the present embodiment.

FIG. 5 is a diagram illustrating a relationship between a rotational angle position δ of a motor and current amounts iu, iv, and iw flowing in each phase.

FIG. 6 is a flowchart of a control routine executed to detect a detection abnormality of a current detection circuit in the present embodiment.

[Explanation of symbols]

10 Electric power steering device 22 Electronic Control Unit (ECU) 24 Three-phase AC brushless motor (motor) 40, 42, 44 Detection circuit for large current 41,43 Small current detection circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B62D 119: 00 H02P 6/02 351P F-term (Reference) 3D032 CC30 CC35 DA15 DA23 DA63 DA64 DD10 EC23 GG01 3D033 CA03 CA13 CA16 CA20 CA32 5H560 AA10 BB04 DA00 DB00 DC01 DC03 DC12 JJ01 RR01 RR10 SS02 XA02 XA05 XA12 XA13

Claims (9)

[Claims] 1. A first current detection circuit capable of detecting a current flowing through an object within a region equal to or less than a first predetermined value, and a second predetermined current flowing through the object being smaller than the first predetermined value. A second current detection circuit that has a higher resolution than that of the first current detection circuit and that can be detected in a region equal to or less than the value, and a current detection circuit whose detected value is used as the target current amount. The first current detection circuit when the current flowing through the target exceeds the second predetermined value, and the second current detection circuit when the current flowing through the target is equal to or less than the second predetermined value. And a detection circuit setting means for setting each of the current detection circuits. 2. The method according to claim 1, wherein the first and second current detection circuits compare a parameter based on a detection value with a parameter based on a detection value of the second current detection circuit.
2. The current detection device according to claim 1, further comprising abnormality detection means for detecting an abnormality of the detection circuit. 3. The current detection device according to claim 2, wherein the abnormality detection unit performs the abnormality detection process under a situation where a current flowing through the target is equal to or less than the second predetermined value. 4. The object is a multi-phase motor, and the first and second current detection circuits are respectively provided for each phase of the multi-phase motor, and the amount of current flowing in the phase The current detection device according to claim 1, wherein the current is detected. 5. The current detection device according to claim 1, wherein the object is subjected to feedback control so that an amount of current actually flowing matches a target amount of current. 6. The vehicle according to claim 1, wherein the target is an auxiliary motor provided in a steering system of the vehicle and configured to generate an assist force in response to a steering operation by a driver. The current detection device according to claim 1. 7. The detection circuit setting means, when an abnormality of the second current detection circuit is detected, even when a current flowing through the target is equal to or less than the second predetermined value. 2. The current detection device according to claim 1, wherein the first current detection circuit is set as a current detection circuit whose detected value is used as the current amount of the target. 8. A control execution means for executing a predetermined control based on a detection value of the current detection circuit set by the detection circuit setting means, wherein the control execution means is configured to detect an abnormality of the second current detection circuit. Is detected, the current flowing through the object is reduced to the second
The current detection device according to any one of claims 1 to 6, wherein predetermined control is performed based on a detection value of the first current detection circuit even when the current detection value is equal to or less than a predetermined value. Control device used. 9. A control execution unit for executing a predetermined control based on a detection value of the current detection circuit set by the detection circuit setting unit, wherein the control execution unit is configured to detect an abnormality of the first current detection circuit. 7. When a is detected, the predetermined control is limited to an area that is not more than the second predetermined value, which is a detectable area of the second current detection circuit. A control device using the current detection device according to claim 1.