JP2019146304A - Motor drive device and electric vehicle with the motor drive device - Google Patents

Abstract

To provide a motor drive device capable of making a control system redundant, improving a noise resistance performance and effectively utilizing it to improve a control performance, and an electric vehicle with the motor drive device.SOLUTION: A motor drive device 6 comprises: a current drive circuit 8; a current sensor S for detecting a current flowing to a motor 4; and a control device 9 which gives a current driving signal to the current drive circuit 8 on the basis of a torque command and the current detected by the current sensor S. As the current sensor S, current sensors to be two pairs capable of detecting a magnitude and a direction of the current are provided in a mutually opposing direction and in any two phases in three phases. The control device 9 includes differential calculation means 16 which calculates a differential of currents detected by the paired current sensors for each of the two phases including the paired current sensors, cancels in-phase noise superimposed on output of the paired current sensors, and uses obtained current values to perform current control.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a motor drive device and an electric vehicle equipped with the motor drive device, and more particularly to a technique for improving control performance while making redundant to prepare for an abnormality of a current sensor provided in the motor drive device.

  Currently, a three-phase AC motor used as a drive source in many electric vehicles can exhibit its performance by flowing an optimal current according to the motor angle. For this reason, current feedback control is often performed by detecting the amount of current with a current sensor attached to a three-phase power line.

On the basis of the principle that the current flowing through the three-phase power lines of a three-phase AC motor becomes zero when summed, a method is often used in which current sensors are attached to two phases and the remaining one phase is obtained by calculation. The merits are for reducing the size and weight by reducing the number of parts, reducing the cost, and simplifying the control. Simplification of control means that when calculation is performed based on actual measurement of three-phase current, the total of the three-phase current is not necessarily zero due to current sensor error or noise, and the target value of the current is obtained. It is necessary to handle the model expression of the vector control calculation for the assumption that an error is included, but if the method is to obtain the current value of the remaining one phase from the current value of the two phases, the model expression of the vector control calculation is It is a point that can be adapted as it is.
Here, noise mainly refers to noise that is superimposed on the output of the current sensor due to switching noise during current control. When noise is superimposed on the output of the current sensor in this way, for example, the control device undesirably performs current control, induces undesirable torque fluctuations, and is observed as vibration or noise. It has become a constant issue.

JP-A-6-253585 JP 2014-72973 A JP 2006-352949 A

  However, as a disadvantage of controlling with only two phase current sensors, if an abnormality occurs in one of the current sensors, current control is performed based on the output abnormal current value, and an abnormal large current is generated. It may cause the motor or motor drive device to overheat or generate unintended torque in the vehicle, improving the safety performance of the automobile and maintaining the performance even when an abnormality occurs. Methods or improvements have been proposed.

  In Patent Literature 1, when the current is detected by attaching current sensors to all three phases using the principle that the sum of the current amounts of the previous three phases becomes zero, the sum of the obtained current amounts does not become zero. A configuration has been proposed in which any current sensor is detected to be abnormal when the difference from zero exceeds a specified value. In this method, even if the occurrence of an abnormal state of the current sensor can be detected, it cannot be detected which current sensor is abnormal.

Paying attention to this point, Patent Document 2 proposes a configuration that employs a process that can attach current sensors to all three phases and specify which current sensor is abnormal from the obtained current values. ing.
In Patent Document 3, the purpose of detecting an abnormality is common, but in addition to the current sensor for two phases necessary for control for detecting an abnormality, the provision of another phase current sensor requires space and From the viewpoint of being disadvantageous in terms of cost, there has been proposed a method for detecting an abnormality of a current sensor by supplying a specific pattern of current for detecting the abnormality.

  In any case, the recognition of the importance of current sensor abnormality detection is consistent. In Patent Document 2, an emphasis is placed on identifying an abnormal current sensor and preventing a decrease in running performance with a normal current sensor that remains even when one-phase abnormality occurs. In Patent Document 3, it is unnecessary for normal time and proposed for the purpose of space reduction and cost reduction by reducing the current sensor for one phase used only at the time of abnormality detection.

  In any case, the current sensors that are installed in excess of the minimum number are used only for fault detection and function replacement at the time of abnormality. There was also room to contribute to improving control performance.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a motor drive device capable of making a control system redundant, improving noise resistance performance and improving control performance, and an electric vehicle equipped with the motor drive device. .

The motor drive device of the present invention is a motor drive device 6 that drives a three-phase AC motor 4 that is a driving source for driving an electric vehicle, and detects a current that flows through the current drive circuit 8 and the three-phase AC motor 4. A current sensor S that controls the current drive circuit 8 based on a given torque command and a current detected by the current sensor S.
As the current sensor S, two pairs of current sensors capable of detecting the magnitude and direction of the current are provided in directions facing each other and in any two phases in three phases,
The control device 9 takes the difference between the currents detected by the pair of current sensors for each of the two phases including the pair of current sensors, and superimposes the difference on the output of the pair of current sensors. The differential operation means 16 that cancels the common-mode noise and performs current control using the obtained current values, respectively.

  According to this configuration, the control device 9 gives a current drive signal to the current drive circuit 8 based on the torque command and the current detected by the current sensor S. For example, when all the current sensors are normal, the output of the pair of current sensors attached to two phases among the current values received by the differential calculation means 16 is adopted. The differential calculation means 16 takes, for example, the difference between the two outputs of the current sensors facing each other, and multiplies the gain so that the magnification becomes 1 as necessary to obtain a current value used for current control.

By the way, in the ideal state without noise, there is no difference even if the difference between the outputs of the pair of current sensors is taken or the output of one current sensor is used without taking the difference. However, in-phase noise may be superimposed on the output of each of the current sensors attached facing each other. The cause of this common-mode noise is, for example, switching noise when performing current control.
Therefore, the differential calculation means 16 takes the difference between the currents detected by the pair of current sensors, cancels the common-mode noise superimposed on the output of the pair of current sensors, and obtains the obtained current value. Each is used for current control. As a result, the same effect as a so-called operation amplification circuit is expected, and the removal of common-mode noise can be expected. Therefore, by preventing undesired current control, it is possible to suppress undesirable torque fluctuations and improve control performance.

The control device 9 includes an abnormality detection means 14 that takes in the output of the pair of current sensors, determines whether the obtained current value satisfies a predetermined conditional expression, and detects an abnormality of the current sensor. It may be. The above “determining whether the obtained current value satisfies a predetermined conditional expression” means, for example, comparing the sum of the obtained current values with a threshold value.
The threshold value is a threshold value arbitrarily determined by design or the like, and is determined by obtaining an appropriate threshold value by one or both of testing and simulation, for example.
In this case, if the paired current sensors mounted in opposition are both normal, the absolute values of the obtained current values are the same, but if any one of the current sensors is abnormal, the result is different. The abnormality of the current sensor can be detected on the basis of the occurrence of.

The abnormality detection means 14 is configured such that when a difference between a current value obtained by adding the outputs of the pair of current sensors and a threshold value is present, one of the pair of current sensors is abnormal. You may diagnose it.
The threshold value is a threshold value arbitrarily determined by design or the like, and is determined by obtaining an appropriate threshold value by one or both of testing and simulation, for example.
In this case, when the outputs of the current sensors mounted opposite to each other are added, if both of the paired current sensors are normal, the addition result is substantially zero or a constant is diagnosed based on the fact that the result is substantially zero or a constant. be able to.

  When one of the paired current sensors is diagnosed as abnormal by the abnormality detection means 14, the control device 9 causes a current to flow as an abnormal location diagnostic current only in the phase having the current sensor. In addition, the current drive circuit 8 may be operated and the abnormal part diagnosis current 15 may be detected by the current sensor so as to have an abnormal part diagnosis unit 15 that identifies a current sensor that is abnormal. By specifying a current sensor that is abnormal as described above, the control device 9 can perform current control using the remaining current sensors that are not diagnosed as abnormal. Therefore, the control performance can be improved.

The current sensor S includes the pair of current sensors provided in the two phases, and a current sensor that detects a current flowing in the remaining one of the three phases.
The control device 9 calculates the sum of the outputs of the current sensors provided in the three phases, one by one from each phase, and when the sum exceeds a threshold value without becoming zero, any current An abnormality location diagnosis unit 15 that identifies an abnormal current sensor by determining that an abnormality has occurred in the sensor and changing the combination of the sums may be provided.
The threshold value is a threshold value arbitrarily determined by design or the like, and is determined by obtaining an appropriate threshold value by one or both of testing and simulation, for example.
By specifying a current sensor that is abnormal as described above, the control device 9 can perform current control using the remaining current sensors that are not diagnosed as abnormal. Therefore, the control performance can be improved.

  When an abnormal current sensor is identified by the abnormal part diagnosis means 15, the control device 9 does not use the output current value of the abnormal current sensor, but uses the output current value of the remaining current sensor. Control may be performed. In this case, even if an abnormality occurs in any of the current sensors, the control performance can be improved and the redundancy can be ensured.

  The electric vehicle according to the present invention includes the motor driving device 6 according to any one of the foregoing embodiments according to the present invention. In this case, each effect mentioned above about the motor drive device 6 of this invention is acquired. In addition, the drivability of electric vehicles can be improved.

  A motor driving device according to the present invention is a motor driving device that drives a three-phase AC motor serving as a driving source for driving an electric vehicle, and includes a current driving circuit, a current sensor that detects a current flowing through the three-phase AC motor, A control device for providing a current drive signal to the current drive circuit based on a given torque command and a current detected by the current sensor, and the current sensor can detect the magnitude and direction of the current. A pair of current sensors are provided in directions opposite to each other and in any two phases of three phases, and the control device includes the pair of current sensors for each phase in the two phases including the pair of current sensors. Difference between the currents detected by the current sensors to cancel the common-mode noise superimposed on the output of the pair of current sensors, and obtain the obtained current values respectively. There has a differential operation means for performing current control. For this reason, while making the control system redundant, it is possible to enhance noise resistance performance and use it to improve control performance.

It is a block diagram of the conceptual composition which shows the electric vehicle provided with the motor drive device concerning this embodiment by a top view. It is a block diagram which shows schematic structure of the motor drive device. It is a block diagram which shows the structure of the control apparatus of the motor drive device. It is a figure which shows the output of the two current sensors which the motor drive device opposes. It is a figure explaining the removal of the common mode noise by the differential calculation of the control apparatus. It is a flowchart which shows the execution order of each means in the same control apparatus. It is a block diagram which shows the structure of the control apparatus of the motor drive device which concerns on other embodiment of this invention. It is a block diagram of the conceptual structure which shows the electric vehicle provided with the motor drive device which concerns on further another embodiment of this invention with a top view.

A motor driving apparatus according to a first embodiment of the present invention will be described with reference to FIGS.
<Conceptual configuration of this electric vehicle>
FIG. 1 is a block diagram of a conceptual configuration showing a plan view of an electric vehicle equipped with a motor drive device according to this embodiment. This electric vehicle is a four-wheeled vehicle in which the wheels 2 that are the left and right rear wheels of the vehicle body 1 are drive wheels, and the wheels 3 that are the left and right front wheels are driven wheels. The front wheel 3 is a steering wheel.

  The electric vehicle of this example is a one-motor on-board type driven by one three-phase AC motor (simply referred to as “motor”) 4 whose left and right wheels 2 and 2 serve as driving sources for travel. The motor 4 is, for example, an embedded magnet type synchronous motor in which a permanent magnet is built in the core portion of the rotor. The motor 4 is a motor in which a radial gap is provided between a stator fixed to a housing and a rotor attached to a rotation output shaft. The wheels 2 and 2 are driven by the motor 4 via a speed reducer (not shown). Each wheel 2 and 3 is provided with a brake. Further, the wheels 3 and 3 which are the steering wheels which are the left and right front wheels can be steered via a steering mechanism (not shown) and are steered by a steering means 5 such as a steering wheel.

<Schematic configuration of motor drive device>
As shown in FIG. 2, the motor driving device 6 receives a torque command from a host control device 7 that controls the vehicle and drives the motor 4, for example. This motor drive device 6 drives a current drive circuit 8 based on a current drive circuit 8, a current sensor S that detects a current flowing through the motor 4, and a torque command that is applied and a current detected by the current sensor S. And a control device 9 for providing a signal. The control device 9 and the current drive circuit 8 constitute an inverter device.

<About the current sensor S to be used>
As the current sensor S, two pairs of current sensors that respectively detect currents in opposite directions are arranged in either direction opposite to each other and any two phases in three phases (in this example, U phase, V current) is provided, and one current sensor for detecting a current flowing in the remaining one phase (in this example, W phase) is provided. The output current value obtained by the current sensor S is input to the control device 9.

  As the current sensor S attached to each phase, for example, a clamp-type current sensor is used. The type of the clamp type current sensor is not limited, but the current sensor described here is a single power supply, shows a preset offset voltage at a current of 0 A, and outputs a signal according to that when a positive or negative current flows It shall be. It should be noted that even current sensors other than the clamp type can be employed as long as they are independent, can determine the direction of the current, and do not affect one of the current sensors in which the influence of the abnormality of one of the current sensors remains.

  The control device 9 is, for example, a control board on which a CPU for calculation and peripheral components are mounted. In the control device 9, each means described later is stored as a program in the memory of the CPU, and each means is implemented based on the processing flow. Further, the control device 9 outputs a current drive circuit drive signal determined after each process to the current drive circuit 8. The output current from the current drive circuit 8 is output to the motor 4 through the three-phase AC transmission line 10. In an actual configuration, an angle sensor or the like for controlling the motor 4 is often attached, but is omitted in the description of the present embodiment.

  As shown in FIGS. 2 and 3, the current drive circuit 8 drives a plurality of switching elements 12 that convert the power of the DC power supply 11 into three-phase AC power used to drive the motor 4, and these switching elements 12. And a gate drive circuit Gd. As each switching element 12, for example, an insulated gate bipolar transistor (abbreviation: IGBT), a field effect transistor (abbreviation: FET), or the like is applied.

<Configuration of Control Device 9 of Motor Drive Device 6>
The control device 9 includes current control means 13 that controls the current drive circuit 8, abnormality detection means 14, abnormality location diagnosis means 15, and differential calculation means 16. Other known means such as external communication means for communicating with the outside are appropriately implemented.

As shown in FIG. 1 and FIG. 3, the host control device 7 receives an accelerator opening signal (acceleration command) output from the accelerator operation unit 17 and a deceleration command output from the brake operation unit 18, or an acceleration command. Then, an acceleration / deceleration command to be given to the motor 4 is generated as a torque command from the deceleration command and the turning command output from the steering means 5, and is output to the control device 9.
The current control means 13 is generally a part corresponding to vector control, and converts a torque command given from the host control device 7 into current target values for three phases. The three-phase current detected by the current sensor S is given to the current control means 13.

<Detailed processing procedure in each means>
The current sensor S exemplified below is a voltage output type current sensor S. As shown in FIG. 4, when the current sensor S shows an offset value (voltage) C at 0A and a current flows in the positive direction of the current sensor, this current sensor The output of the current sensor changes in a direction larger than the offset value C, and when a current flows in the negative direction of the current sensor, the output of the current sensor changes in a direction smaller than the offset value C.

<Specific operation of abnormality detection means>
As shown in FIGS. 3 and 4, the abnormality detection means 14 takes in the output of the paired current sensor, compares the obtained current value with a threshold value, and detects the abnormality of the current sensor.
When a certain current is passed through a pair of current sensors mounted opposite to a certain phase, the outputs of the respective current sensors have the same absolute value, and the current directions indicate opposite directions. Therefore, if there is no influence of noise or error, the detected current value should be canceled out as the sum of the outputs of the pair of current sensors, and the result should be twice the offset value.

  Actually, a difference occurs from this value due to the error and noise of the current sensor, but an allowable difference threshold S1 is determined with reference to the guaranteed value of the current sensor error and the noise level. If the difference exceeds this threshold and becomes large, it is predicted that the current sensor does not output a correct value for some reason, so an abnormality is diagnosed. That is, when the difference between the current value obtained by adding the outputs of the pair of current sensors and the threshold value is large, the abnormality detection unit 14 detects that one of the pair of current sensors is abnormal. Diagnose it. Since this threshold may be exceeded momentarily due to spike noise or the like, the current value obtained by adding the outputs of the paired current sensors exceeds the threshold and has a large difference for a certain time (for example, for 100 ms). If the condition continues, an abnormality may be diagnosed.

  Here, current sensors U1 and U2 are attached as two opposing current sensors for the U phase, and current sensors V1 and V2 are attached as two opposing current sensors for the V phase. It is assumed that one current sensor W1 is attached to the W phase in the same direction as the current sensors U1 and V1. In this case, the abnormality detection means 14 determines whether or not the following conditional expression is satisfied. Hereinafter, values (voltages) obtained from the current sensors U1, U2, V1, and V2 are respectively shown as U1, U2, V1, and V2.

| U1 + U2-2C | <S1 (Formula 1)
| V1 + V2-2C | <S1 (Formula 2)
At this time, it is assumed that the determination result of each expression is Expression 1: True and Expression 2: False. Therefore, the difference in output between the U-phase current sensors U1 and U2 is in an allowable range, and no abnormality is recognized. In addition, the calculation result on the left side of Expression 2 exceeds the threshold value S1 for determining the abnormality, and the outputs of the V-phase current sensors V1 and V2 are determined in advance so that the absolute values of the obtained results are greatly different. It is predicted that the offset value C is greatly deviated, and an abnormality is diagnosed. The deviation of the offset value can be considered such that the output becomes zero when power is not supplied from the power supply to be supplied to the current sensor.

By performing the above processing, it is possible to diagnose whether or not any of the current sensors in that phase is abnormal with respect to the current sensors attached to each other in pairs. The results are shown in Table 1. In Table 1, circles indicate normality and crosses indicate abnormality.

<Specific Operation of Abnormal Location Diagnosis Means 15>
Up to this point, according to the diagnosis of the abnormality detection means 14, the pair of current sensors U1 and U2 attached to the U phase are both normal, and one of the pair of current sensors V1 and V2 attached to the V phase. Has been diagnosed as abnormal. It is not determined whether the W-phase current sensor W1 is abnormal.
Even though the abnormality detection means 14 can diagnose whether there is a current sensor that is abnormal in that phase, it cannot determine which of the current sensors that are paired in that phase is abnormal. Therefore, the abnormal part diagnosis means 15 performs a process for determining this.

  As shown below, the abnormal part diagnosis means 15 calculates the sum of the outputs of the UVW-phase current sensors and determines whether the result is substantially zero. In practice, a difference from “zero” occurs due to the error and noise of the current sensor, but an allowable difference threshold S2 is determined with reference to the guaranteed value of the current sensor error and the noise level. Therefore, the abnormal part diagnosis means 15 determines whether or not the following conditional expression is satisfied. Hereinafter, values (voltages) obtained from the current sensors U1, U2, V1, V2, and W1 are shown as U1, U2, V1, V2, and W1, respectively.

| U1 + V1 + W1-3C | <S2 (Formula 3)
| U2 + V2 + (− 1) × W1-C | <S2 (Formula 4)
Here, the reason why W1 is multiplied by −1 in Expression 4 is that the current sensor W1 is attached in the opposite direction with respect to the current sensor U2 and the current sensor V2, and W1 is increased by −1. Thus, the current directions of the current sensor U2 and the current sensor V2 are matched. Further, since −1 × W1 is added, the offset value is also canceled out, and Expression 4 is obtained.

In the above conditional expression, if Expression 3: True, Expression 4: False, the calculation result on the left side of Expression 4 exceeds the threshold value S2 for determining an abnormality, and one of the current sensors U2, V2, W1 is abnormal. Can be diagnosed. Since any one of the V-phase current sensors is diagnosed as abnormal according to the calculation formula 2 of the previous abnormality detection means 14, it can be determined that the abnormal current sensor is the current sensor V2.
By combining the above processing and the processing result of the abnormality detection means 14, it is possible to specify which current sensor is abnormal. The result of the abnormality diagnosis is recorded in a variable that stores the state of each current sensor, and is used as a criterion for determining whether or not to use in subsequent calculations.

The above contents are summarized in Table 2. In Table 2, circles indicate normality and crosses indicate abnormality.

<Specific Operation of Differential Calculation Unit 16>
<< Operation when current sensor is normal >>
First, the operation when there is no abnormality in the current sensor will be described.
The value (voltage) obtained by the current sensor U1 and the current sensor U2 is a value including the offset value C. Here, each sensor output and the current IU flowing in the U phase have the following relationship.
(U1-U2) / 2 = IU
By performing the same process for the V phase, the current IV flowing in the V phase can be obtained. As described above, the current value necessary for the control can be obtained by the current control in the subsequent stage of the processing of the differential operation means 16.

<< Operation when current sensor is abnormal >>
Next, an operation when there is an abnormality in the current sensor will be described.
From the information on which current sensor is abnormal passed from the abnormal part diagnosis means 15, for example, when even one current sensor has an abnormality, the differential calculation may not be performed.

Specifically, ENU1 = 1 when there is no abnormality (valid) in the current sensor U1, similarly, ENU2 = 1 when the current sensor U2 is valid, and ENU1 = 0 and ENU2 = when the current sensors U1 and U2 are abnormal, respectively. A variable to be 0 may be prepared, and the abnormality detecting unit 15 may cause the abnormality detecting unit 14 to update the value. Moreover, you may calculate as follows with obtained ENU1 and ENU2 and output U1, U2 of each current sensor.
IU = (U1 * ENU1-U2 * ENU2) / (ENU1 + ENU2)
However, when ENU1 = ENU2 = 0, the calculation is not performed and the driving of the motor 4 is stopped.
Similarly, the same calculation is performed for the V phase or, depending on the configuration, the W phase.

<Removal of common-mode noise by differential operation>
The differential calculation means 16 takes the difference between the currents detected by the pair of current sensors for the two phases (U phase and V phase in this example) including the pair of current sensors to form the pair. The common-mode noise superimposed on the output of the current sensor is canceled, and current control is performed using the obtained current values.
In the ideal state without noise, there is no difference even if the difference between the currents detected by the pair of current sensors is taken or the output of one current sensor is used without taking the difference. However, if in-phase noise is superimposed on the output of each of the current sensors that are mounted facing each other, the difference between the results obtained from the two paired current sensors can be taken to obtain the same effect as the operation amplification circuit. Expected to eliminate common-mode noise.

  Here, it is assumed that in-phase noise as shown in FIG. 5 is superimposed on U1 and U2 which are outputs of the current sensor U1 and the current sensor U2 attached to the U phase. Here, U1-U2 which took the difference of two signals is also shown in FIG. As shown in FIG. 5, spike-like in-phase noise observed in U1 and U2 is not seen in U1-U2. As described above, it is possible to remove the common mode noise by performing the differential calculation in the differential calculation means 16. The cause of this common-mode noise is, for example, switching noise when performing current control. When the generated noise is superimposed on the power supply of the current sensor, the noise may be superimposed on the output of the current sensor, or the switching noise may be directly superimposed on the output signal of the current sensor.

<Specific Operation of Current Control Unit 13>
As shown in FIGS. 2 and 3, the current control unit 13 performs current control represented by vector control. In this example, the current control unit 13 performs current control based on the U-phase and V-phase currents output from the differential operation unit 16. The current control means 13 further increases the current target value if the detected current is smaller than the calculated current target value, and further decreases the current target value if the detected current is larger than the calculated current target value. Thus, the motor current is feedback controlled. The current control means 13 calculates a command voltage by feedback control, uses this command voltage as a pulse width modulation signal, and gives an on / off command to the gate drive circuit Gd. Changing the current is realized by changing the pulse width by PWM operation.

<About the execution order of each means in the control device>
FIG. 6 is a flowchart showing the execution order of each means in the control device. Hereinafter, description will be made with reference to FIGS. 2 and 3 as appropriate.
After starting this process, the control device 9 reads the current values output from all the current sensors (step S1). The read current value is transferred to the abnormality detection means 14 (step S2).
As described above, the abnormality detection unit 14 determines whether or not an abnormality has occurred in any of the current sensors and outputs an abnormal signal from the received current value, and outputs the result (step). S3).

  When all the current sensors are normal and there is no abnormality (step S3: no), the current value read by the control device 9 is transferred to the differential calculation means 16 as it is. Assuming that all current sensors are normal, the outputs of two pairs of current sensors attached to two phases (in this example, the U phase and the V phase) among the current values received by the differential operation means 16 are adopted. . The differential calculation means 16 takes the difference between the two outputs of the current sensor mounted opposite to each other, multiplies the gain so that the result is 1 time as necessary, and the current value used for current control. (Step S4).

  The current value used for current control obtained by the calculation of the differential calculation means 16 is transferred to the current control means 13. The current control means 13 performs a calculation based on the current values of the three phases (or the measured values of the current values of the two phases and the current value of the one phase obtained therefrom), and calculates the current target values of the three phases. (Step S5). Generally, the current drive circuit 8 is PWM-controlled, and the current control means 13 obtains and outputs the PWM duty ratio by calculation.

The control device 9 outputs a current drive circuit drive signal to the current drive circuit 8 based on the PWM duty ratio determined by the current control means 13 (step S6). The current drive circuit drive signal is generally a PWM pulse signal. Thereafter, this process is terminated.
When the abnormality detection means 14 diagnoses that there is an abnormality in the current sensor (step S3: yes), the process proceeds to step S7. For example, it is assumed that the difference between the outputs of a pair of opposing current sensors is greater than a threshold value, and that abnormality is diagnosed by the abnormality detection means 14. When the current sensor is diagnosed as abnormal, it is known which of the three phases is abnormal. However, it is unclear which current sensor out of the pair of current sensors attached facing each other is abnormal.

Therefore, in a state in which a certain phase of the abnormal current sensor is found by the abnormality detection unit 14, the abnormal part diagnosis unit 15 determines which current sensor is abnormal in the phase (step S7). The abnormal part diagnosis means 15 updates the abnormal information indicating which current sensor is abnormal (in other words, information indicating which current sensor output cannot be adopted), which has been found as a result, and has updated this information. Abnormal information is transferred to the differential operation means 16 (step S8). Thereafter, the process proceeds to step S4. In the subsequent processing, current control for driving is performed without using the current value obtained by the current sensor diagnosed as abnormal. Thereby, even if an abnormality occurs in any of the current sensors, the control performance can be improved and redundancy can be ensured.
The above is one cycle of the control flow related to current control, and is processed once per calculation cycle.

<About the effects>
In-phase noise may be superimposed on the output of each of the current sensors attached to face each other. The cause of this common-mode noise is, for example, switching noise when performing current control.
Therefore, the differential calculation means 16 takes the difference between the currents detected by the pair of current sensors, cancels the common-mode noise superimposed on the output of the pair of current sensors, and obtains the obtained current value. Each is used for current control. As a result, the same effect as a so-called operation amplification circuit is expected, and the removal of common-mode noise can be expected. Therefore, it is possible to prevent undesired current limitation due to common-mode noise and improve control performance. In addition, the current value obtained by the current sensor diagnosed as abnormal is not used and the current control for driving is performed, so even if any current sensor has an abnormality, the control performance can be improved. Redundancy can be ensured.

<About other embodiments>
In the following description, the same reference numerals are given to portions corresponding to the matters described in advance in the respective embodiments, and overlapping descriptions are omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described in advance unless otherwise specified. The same effect is obtained from the same configuration. Not only the combination of the parts specifically described in each embodiment, but also the embodiments can be partially combined as long as the combination does not hinder.

<Example of adding a procedure to investigate W-phase abnormalities each time>
In the processing of the abnormality detection means 14 and the abnormality location diagnosis means 15 described above, the diagnosis of the abnormality location diagnosis means 15 is performed for the phase to which only one current sensor is attached (the W-phase current sensor W1 in the example of Table 1). Among these, it is determined that there is no abnormality when Expression 3 or Expression 4 holds.
However, if processing is performed according to the procedure shown in FIG. 6, it is not possible to detect that the current sensor W1 is abnormal, and if an abnormality occurs in the current sensor V2 while the current sensor W1 is abnormal, The output of the current sensor W1 required when performing the diagnosis by the diagnosis unit 15 is not normal, and the abnormal part diagnosis unit 15 cannot be completed normally.

Therefore, the abnormality detecting means 14 investigates whether or not the current sensor W1 has any abnormality by examining whether or not the following conditions are satisfied after diagnosis that all of the paired current sensors are normal. Good.
| U1 + V1 + W1-3C | <S2 (Formula 5)
As a result, it is possible to always monitor whether there is an abnormality in the current sensor W1. If it is first diagnosed that only the current sensor W1 is abnormal based on the diagnosis result of whether W1 obtained from the current sensor W1 is normal or abnormal, the current control is stopped without performing the abnormal part diagnosis means 15. If one of the U-phase and V-phase current sensors is abnormal and the current sensor W1 is diagnosed as normal until immediately before, the result of the current sensor W1 is obtained. The measure of trust can be taken.

<Example of using current sensor offset as a variable>
So far, the constant C has been used as the offset of the current sensor. However, depending on the current sensor used, the offset varies depending on the machine difference or temperature, and this difference causes deterioration in control performance. It is conceivable to update the measured values of the data as needed. Therefore, the offset used in the previous abnormality detection means 14 and abnormality location diagnosis means 15 may be a numerical value updated by actual measurement instead of a constant.

<Configurations other than those illustrated>
Up to this point, a configuration using two current sensors in two phases and one current sensor in one phase has been shown. However, a total of six current sensors, two in pairs, are used for each of the three phases, and all phases are diagnosed by the abnormality detection means 14 to determine whether there are any abnormalities. Even when an abnormal part is specified by the diagnostic means 15, for example, in the case of an abnormality in one current sensor, the remaining five current sensors are operated in accordance with the procedure described so far to increase the redundancy. Also good. In addition, when only two current sensors are attached to two phases and no current sensor is attached to the remaining one phase, the abnormal part using the relation that the sum of the three phases proposed by the abnormal part diagnosis means 15 becomes zero is used. The determination method cannot be used.

  As shown in FIG. 7, as a current sensor, two pairs of current sensors that detect currents in opposite directions are arranged in either direction opposite to each other and any two phases in three phases ( In this example, the U phase and the V phase may be provided, and the current sensor may not be attached to the remaining one phase (in this example, the W phase).

  Here, it is assumed that current sensors U1 and U2 are attached as two opposing current sensors for the U phase, and current sensors V1 and V2 are attached as two opposing current sensors for the V phase. In this case, the abnormality detection means 14 (FIG. 3) determines whether or not the following conditional expression is satisfied. Hereinafter, values (voltages) obtained from the current sensors U1, U2, V1, and V2 are respectively shown as U1, U2, V1, and V2.

| U1 + U2-2C | <S1 (Formula 6)
| V1 + V2-2C | <S1 (Expression 7)
At this time, it is assumed that the determination result of each expression is Expression 6: True and Expression 7: False. Therefore, the difference in the output of the U-phase current sensor is within an acceptable range and no abnormality is recognized. In addition, the calculation result on the left side of Expression 7 exceeds the threshold value S1 that is determined to be abnormal, and the output of the V-phase current sensor is largely different from the absolute value of the obtained result or a predetermined offset value. A large deviation from C is expected, and an abnormality is diagnosed. The deviation of the offset value can be considered such that the output becomes zero when power is not supplied from the power supply to be supplied to the current sensor.

By performing the above processing, it is possible to diagnose whether or not any of the current sensors in that phase is abnormal with respect to the current sensors attached to each other in pairs. The results are shown in Table 3. In Table 3, circles indicate normality and crosses indicate abnormality.

<Specific operation of abnormality location diagnosis means>
Up to this point, according to the diagnosis of the abnormality detection means 14 (FIG. 3), the pair of current sensors attached to the U phase are both normal, and one of the pair of current sensors attached to the V phase is abnormal. Has been diagnosed.
Although the abnormality detection means 14 (FIG. 3) can diagnose whether there is a current sensor that is abnormal in that phase, it can determine which of the current sensors that are paired in that phase is abnormal. Can not. Therefore, the abnormal part diagnosis means 15 (FIG. 3) performs a process for determining this.

As shown below, the abnormal part diagnosis means 15 (FIG. 3) has a current drive circuit 8 so that a current flows as an abnormal part diagnostic current only in the phase (the U phase and the V phase in this example) to which the current sensor is attached. Is operated, and the abnormal part diagnosis current is detected by the current sensor, thereby identifying the abnormal current sensor.
In order to allow current to flow only in the U phase and the V phase, the U phase switching element 12 (FIG. 3) has a high side, the V phase switching element 12 (FIG. 3) has a low side, and the W phase switching element 12 (FIG. 3). 3) is realized by turning both off. At this time, the sum of the three-phase alternating currents is zero, and the W-phase current is zero.

(U-phase current) + (V-phase current) + (W-phase current) = 0 (Expression 8)
Here, from W phase current = 0,
(U phase current) = − (V phase current) (Equation 9)
Therefore, U1−V1 = 0 and U2−V2 = 0 ideally, but in reality, a difference from “zero” is caused by the error or noise of the current sensor. An allowable difference threshold S2 is determined with reference to the level. Therefore, the abnormal part diagnosis means 15 (FIG. 3) determines whether or not the following conditional expression is satisfied.
| U1-V1 | <S2 (Formula 10)
| U2-V2 | <S2 (Formula 11)

In the above conditional expressions, when Expression 10: True and Expression 11: False, it is understood that the current sensor U2 or the current sensor V2 is abnormal. Here, since the abnormality detection means 14 (FIG. 3) knows that the V-phase current sensor is abnormal, it can be determined that the current sensor V2 is abnormal.
By combining the above processing and the processing result of the abnormality detection means 14 (FIG. 3), it is possible to identify which current sensor is abnormal. The result of the abnormality diagnosis is recorded in a variable that stores the state of each current sensor, and is used as a criterion for determining whether or not to use in subsequent calculations.

その他第１の実施形態と同様の構成を有し、第１の実施形態と同様の作用効果を奏する。また図７の構成によれば、第１の実施形態よりも電流センサの個数を低減することでコスト低減を図れる。 The above contents are summarized in Table 4. In Table 4, circles indicate normality and crosses indicate abnormality.

In addition, it has the same configuration as that of the first embodiment, and has the same effects as those of the first embodiment. Further, according to the configuration of FIG. 7, the cost can be reduced by reducing the number of current sensors as compared with the first embodiment.

  The electric vehicle including the motor drive device according to any one of the embodiments is not limited to the one motor on-board type described above. For example, as shown in FIG. 8 (a), two motors 4, 4 and a speed reducer corresponding to each motor 4 are provided in the vehicle body 1, and the left and right wheels 3, 3 are driven by these motors 4, 4. The motor driving devices 6 and 6 may be provided in a motor-on-board type electric vehicle. As shown in FIG. 8 (b), the left and right wheels 2 and 2 are each in-wheel motor type electric vehicle driven by a motor 4 constituting an in-wheel motor drive device IWM. May be provided. 8A and 8B, the left and right wheels driven by the motor 4 may be either the front or rear wheels 3 or 2. Also, four-wheel drive may be used.

  As mentioned above, although the form for implementing this invention based on embodiment was demonstrated, embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

4 ... Three-phase AC motor 6 ... Motor drive device 8 ... Current drive circuit 9 ... Control device 14 ... Abnormality detection means 15 ... Abnormal part diagnosis means 16 ... Differential operation means S ... Current sensor

Claims (7)

A motor driving device for driving a three-phase AC motor serving as a driving source for driving an electric vehicle, comprising: a current driving circuit; a current sensor for detecting a current flowing through the three-phase AC motor; a torque command to be applied and the current A control device for providing a current drive signal to the current drive circuit based on a current detected by a sensor,
As the current sensor, two pairs of current sensors capable of detecting the magnitude and direction of the current are provided in directions facing each other and in any two of the three phases, respectively.
The control device takes a difference between currents detected by the pair of current sensors for each phase in the two phases including the pair of current sensors and superimposes them on the output of the pair of current sensors. A motor drive device having differential arithmetic means for canceling common-mode noise and performing current control using the obtained current values.   2. The motor drive device according to claim 1, wherein the control device captures an output of the pair of current sensors, determines whether the obtained current value satisfies a predetermined conditional expression, and detects an abnormality of the current sensor. Motor drive device having an abnormality detection means for detecting   3. The motor drive device according to claim 2, wherein when there is a difference between a current value obtained by adding outputs of the pair of current sensors and a threshold value, the abnormality detection unit is the pair of current sensors. A motor drive device that diagnoses that one of the current sensors is abnormal.   4. The motor drive device according to claim 3, wherein the control device is only in a phase having a current sensor when any one of the paired current sensors is diagnosed as abnormal by the abnormality detecting means. A motor drive having an abnormal location diagnosis means for identifying an abnormal current sensor by operating the current drive circuit so as to pass a current as an abnormal location diagnosis current and detecting the abnormal location diagnosis current with the current sensor apparatus. 4. The motor drive device according to claim 1, wherein the current sensor includes a current flowing in one phase of the pair of the current sensors provided in the two phases and the remaining one of the three phases. 5. A current sensor to detect,
The control device takes the sum of the outputs of the current sensors provided in the three phases, one by one from each phase, and when the sum exceeds a threshold value without becoming zero, any current sensor A motor drive device having an abnormality location diagnosis means for determining a current sensor that is abnormal by determining that an abnormality has occurred and changing the combination that takes the sum.   6. The motor driving device according to claim 4, wherein when the abnormal current sensor is specified by the abnormal part diagnosis means, the control device does not use the output current value of the abnormal current sensor and remains. Motor drive device that performs current control using the output current value of the current sensor.   An electric vehicle comprising the motor drive device according to any one of claims 1 to 6.

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