Current sensor abnormality detection device

Abstract

To address a problem that it is difficult to detect an abnormality in a current sensor when a value of an output current is small.SOLUTION: A current sensor detection device for a motor control device including an inverter that outputs power to a three-phase motor, a current sensor that detects three-phase output current output from the inverter to the motor, and a control unit that controls the inverter to drive the motor, includes: a first rotation speed computation unit that computes a rotation speed of the motor on the basis of an angle sensor provided in the motor; a second rotation speed computation unit that computes the rotation speed of the motor on the basis of the three-phase output current detected by the current sensor; and an abnormality determination unit that determines an abnormality in the current sensor on the basis of the rotation speed obtained by the first rotation speed computation unit and the rotation speed obtained by the second rotation speed computation unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a current sensor abnormality detection device. [Background technology]

[0002] Vehicles such as hybrid cars and electric cars are equipped with an inverter that controls a motor. The inverter converts DC power supplied from a DC power source into AC power and outputs the AC power to a three-phase motor. In order to control the driving of the motor, current sensors are provided to detect the three-phase output currents output to the motor. In order to appropriately control the driving of the motor, abnormalities in the current sensors are detected.

[0003] Patent document 1 discloses a motor control device that detects that one of the current sensors is abnormal when the difference between the current measurements in at least two phases in which the current sensors are installed and whose current measurements should be the same is greater than a predetermined value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-73351 A Summary of the Invention [Problem to be solved by the invention]

[0005] The device described in Patent Document 1 has a problem in that it becomes difficult to detect an abnormality in the current sensor when the value of the output current is small. [Means for solving the problem]

[0006] The current sensor abnormality detection device according to the present invention is a current sensor abnormality detection device for a motor control device comprising an inverter that outputs power to a three-phase motor, a current sensor that detects output currents of each of the three phases output from the inverter to the motor, and a control unit that controls the inverter to drive the motor, and comprises a first rotational speed calculation unit that calculates the rotational speed of the motor based on an angle sensor provided in the motor, a second rotational speed calculation unit that calculates the rotational speed of the motor based on the output currents of the three phases detected by the current sensor, and an abnormality judgment unit that judges an abnormality in the current sensor based on the rotational speed calculated by the first rotational speed calculation unit and the rotational speed calculated by the second rotational speed calculation unit. Effect of the Invention

[0007] According to the present invention, even when the value of the output current is small, it is possible to detect an abnormality in the current sensor, thereby improving reliability. [Brief description of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram of a motor control device according to an embodiment; [Diagram 2] (A)(B)(C)(D)(E)(F) Graphs showing the pulse wave and count converted based on the output current. [Diagram 3] 4 is a flowchart for detecting an abnormality in a current sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and appropriate omissions and simplifications have been made for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0010] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0011] FIG. 1 is an overall configuration diagram of a motor control device 100 according to an embodiment of the present invention. The motor control device 100 includes a control unit 1, an inverter 2, and a current sensor 3, and drives and controls a motor 4. The motor 4 is a three-phase motor. An angle sensor 41 is provided near the motor 4 and transmits angle information of the motor 4 to the control unit 1.

[0012] The control unit 1 controls the inverter 2 by outputting a PWM signal D for turning on / off a semiconductor element in the inverter 2 in response to a torque command from a higher-level control device (not shown) and by referring to a current value detected by the current sensor 3 and angle information detected by the angle sensor 41. In addition, as will be described later with reference to FIG. 3, the control unit 1 detects an abnormality in the current sensor 3.

[0013] The inverter 2 switches semiconductor elements in response to a PWM signal D, converts DC power supplied from a battery (not shown) into AC power, and drives the motor 4.

[0014] Current sensor 3 detects the output current output from inverter 2 to motor 4 and transmits it to control unit 1. The output current flows through each of the U, V, and W phases, and current sensors 31, 32, and 33 are provided corresponding to each phase. Current sensor 31 detects the value iu of the output current flowing through the U phase. Current sensor 32 detects the value iv of the output current flowing through the V phase. Current sensor 33 detects the value iw of the output current flowing through the W phase.

[0015] Here, the current sensors 31, 32, and 33 may all be current sensors using a Hall element and a core, but in this embodiment, the current sensors 31 and 32, which are the first current sensors, use highly accurate current sensors using a Hall element and a core. The current sensor 33, which is the second current sensor, uses an inexpensive current sensor using a coreless or shunt resistor. This current sensor 33 may be configured to detect at least the zero cross point of the output current flowing through the W phase. Note that, although the following description is given using an example in which the current sensor 33 is provided corresponding to the W phase, the same applies to a configuration in which the current sensor 33 is provided in one of the three phases and the current sensors 31 and 32 are provided in the remaining phases.

[0016] The control unit 1 includes an angle sensor abnormality detection unit 11, a first rotation speed calculation unit 12, a pulse conversion unit 13, a counting unit 14, a second rotation speed calculation unit 15, a current sensor abnormality determination unit 16, and a motor control unit 17.

[0017] The angle sensor abnormality detection unit 11 detects whether there is an abnormality in the angle sensor 41 based on the angle information output from the angle sensor 41. If there is an abnormality, the angle sensor abnormality detection unit 11 outputs information indicating the abnormality of the angle sensor 41 to the current sensor abnormality determination unit 16 and the motor control unit 17.

[0018] The first rotation speed calculation unit 12 calculates the rotation speed of the motor 4, for example, by a differential calculation, based on the angle information output from the angle sensor 41. Then, the first rotation speed calculation unit 12 outputs the calculated rotation speed to the current sensor abnormality determination unit 16 and the motor control unit 17.

[0019] The pulse converter 13 generates a pulse wave for each phase based on the zero crossing points of the values ​​iu, iv, and iw of the output currents flowing through the respective phases detected by the current sensors 31, 32, and 33. Details will be described later. The counter 14 counts the timing of the rising edge of the pulse wave of each phase, or the timing of the rising edge and the falling edge of the pulse wave of each phase. Details will be described later.

[0020] The second rotation speed calculation unit 15 calculates the rotation speed of the motor 4 based on the time required for a count value obtained by counting the timing of the rise of the pulse wave of each phase to reach a predetermined count value, or calculates the rotation speed of the motor 4 based on the time required for a count value obtained by counting the timing of the rise and fall of the pulse wave of each phase to reach a predetermined count value.

[0021] When no information indicating an abnormality in the angle sensor 41 is input from the angle sensor abnormality detection unit 11, the current sensor abnormality determination unit 16 compares the rotation speed calculated by the first rotation speed calculation unit 12 with the rotation speed calculated by the second rotation speed calculation unit 15. If the difference between the two is within a predetermined range, the rotation speeds are deemed to match and the current sensors 31, 32 are determined to be normal. On the other hand, if the difference between the two exceeds a predetermined range, the current sensors 31, 32 are determined to be abnormal. If an abnormality is determined, information indicating an abnormality in the current sensors 31, 32 is output to the motor control unit 17.

[0022] During normal operation, the motor control unit 17 generates a PWM signal D to be output to the inverter 2 based on the rotation speed of the motor 4 from the first rotation speed calculation unit 12 and the output current values ​​iu and iv from the first current sensors (current sensors 31 and 32) in response to a torque command from a higher-level control device (not shown). The output current values ​​iu and iv are the detection values ​​from the first current sensors (current sensors 31 and 32), while the W-phase current value iw is calculated by the motor control unit 17 as, for example, iw=-iu-iv. This calculation is based on the assumption that the sum of the current flowing into and out of the motor coil of each phase of the motor 4 is 0. Note that if the current sensors 31, 32, and 33 are all first current sensors using hall elements and cores, the motor control unit 17 uses these output current values ​​iu, iv, and iw.

[0023] On the other hand, when information indicating an abnormality in the sensor is input from the angle sensor abnormality detection unit 11 or the current sensor abnormality determination unit 16, the motor control unit 17 generates, for example, a PWM signal D for turning off all the semiconductor elements in the inverter 2. This causes the motor 4 to transition to a safe state.

[0024] Figures 2(A), 2(B), 2(C), 2(D), 2(E), and 2(F) are graphs showing the pulse wave and count converted based on the output current. 2(A) shows the output current values ​​iu, iv, and iw of each phase output from inverter 2 during normal operation, with the horizontal axis representing the phase angle and the vertical axis representing the current value. The output current of each phase is a sine wave with a phase difference of 120 degrees. A first current sensor (current sensors 31, 32) detects the output current values ​​iu and iv of the U and V phases, and a second current sensor (current sensor 33) detects the output current value iw of the W phase.

[0025] 2B, 2C, and 2D show pulse waves generated by the pulse converter 13 based on the zero crossing points of the output current values ​​iu, iv, and iw of each phase detected by the first current sensor (current sensors 31 and 32) and the second current sensor (current sensor 33). FIG. 2B shows a U-phase pulse wave, FIG. 2C shows a V-phase pulse wave, and FIG. 2D shows a W-phase pulse wave. In each case, the pulse converter 13 generates pulse waves that rise at the zero crossing points when the output current values ​​iu, iv, and iw change from negative to zero, and fall at the zero crossing points when they change from positive to zero. The pulse waves have a phase difference of 120 degrees for each phase. It is also possible to generate pulse waves that rise at the zero crossing points when the output current values ​​iu, iv, and iw change from positive to zero, and fall at the zero crossing points when they change from negative to zero.

[0026] Figures 2(E) and 2(F) are graphs showing the counting of the pulse waves in the counter 14. Figure 2(E) shows an example of counting the timing of the rising edge of the pulse wave of each phase, and Figure 2(F) shows an example of counting the timing of the rising edge and falling edge of the pulse wave of each phase. The counter 14 detects the timing of the rising edge or the rising edge and falling edge of the pulse wave shown in Figures 2(B), 2(C), and 2(D), and counts up an internally provided counter.

[0027] FIG. 3 is a flowchart showing a process for detecting an abnormality in a current sensor. This flowchart shows the operation of the control unit 1, and mainly shows the operations of the pulse conversion unit 13, the counting unit 14, the second rotation speed calculation unit 15, and the current sensor abnormality determination unit 16.

[0028] In step S10, it is determined whether information indicating an abnormality in the angle sensor 41 is output from the angle sensor abnormality detection unit 11. If information indicating an abnormality is output, the process of detecting an abnormality in the current sensor is terminated. If the angle sensor 41 is abnormal, this is because the rotation speed calculated by the first rotation speed calculation unit 12 is not accurate, and the operation of the current sensor abnormality determination unit 16 is also not accurate. If information indicating an abnormality is not output in step S10, the process proceeds to step S11.

[0029] In step S11, the counter 14 counts the timing of the rise or the timing of the rise and fall of the pulse wave generated by the pulse converter 13. Then, the process proceeds to step S12.

[0030] In step S12, counting unit 14 determines whether the count value is 3 or 6 or more. In an example where the timing of the rising edge of a pulse wave is counted, it determines whether the count value is 3 or more, and in an example where the timing of the rising and falling edges of a pulse wave is counted, it determines whether the count value is 6 or more. If the count value is not the predetermined count value of 3 or 6 or more, it returns to step S11 and continues counting. If the count value reaches the predetermined count value, it proceeds to step S13.

[0031] In step S13, second rotation speed calculation unit 15 calculates the time t required from when counting unit 14 starts counting until a predetermined count value is reached, and then the process proceeds to step S14. In step S14, the second rotation speed calculation unit 15 calculates the rotation speed of the motor 4 based on the time t required to reach a predetermined count value. Specifically, if the count value is 3 or 6, this indicates that the motor 4 has rotated once, and the rotation speed of the motor 4 is calculated from the time required for one rotation. Then, the process proceeds to step S15.

[0032] In step S15, current sensor abnormality determination unit 16 compares the rotation speed calculated by first rotation speed calculation unit 12 with the rotation speed calculated by second rotation speed calculation unit 15. If the difference between the two is within a predetermined range, the rotation speeds are deemed to match, and the process proceeds to step S16. If the difference between the two exceeds a predetermined range, the first current sensor (current sensors 31, 32) is determined to be abnormal, and the process proceeds to step S17.

[0033] In step S16, current sensor abnormality determination unit 16 resets the count value of counter 14 to an initial value, for example, zero, and proceeds to step S10. Thereafter, the process from step S10 is repeated. In step S17, current sensor abnormality determination unit 16 outputs to motor control unit 17 information indicating an abnormality in the current sensor. When information indicating an abnormality in the sensor is input from the current sensor abnormality determination unit 16, the motor control unit 17 generates a PWM signal D required to transition the motor 4 to a safe state.

[0034] Generally, in cases where this embodiment is not applied, when detecting an abnormality in a current sensor, the magnitude of the output current value is measured and compared with a threshold value. In this case, a threshold value that takes into account the maximum load is required. Therefore, when the output current value is small, it becomes difficult to detect an abnormality in the current sensor. In addition, the current sensor is required to have an expensive configuration because it is necessary to measure the magnitude of the output current value.

[0035] On the other hand, according to the present embodiment, an abnormality in the current sensor is detected based on the zero crossing point of the output current, so that an abnormality in the current sensor can be detected regardless of the value of the output current, even when the value of the output current is small. Furthermore, since the second current sensor (current sensor 33) does not need to detect the magnitude of the value of the output current and only needs to detect the zero crossing point of the output current, an inexpensive current sensor using a coreless or shunt resistor can be used.

[0036] According to the embodiment described above, the following advantageous effects can be obtained. (1) The current sensor abnormality detection device is a current sensor abnormality detection device for a motor control device 100 including an inverter 2 that outputs power to a three-phase motor 4, a current sensor 3 that detects the output current of each of the three phases output from the inverter 2 to the motor 4, and a control unit 1 that controls the inverter 2 to drive the motor 4, and includes a first rotation speed calculation unit 12 that calculates the rotation speed of the motor 4 based on an angle sensor 41 provided in the motor 4, a second rotation speed calculation unit 15 that calculates the rotation speed of the motor 4 based on the three-phase output current detected by the current sensor 3, and a current sensor abnormality determination unit 6 that determines an abnormality in the current sensor 3 based on the rotation speed calculated by the first rotation speed calculation unit 12 and the rotation speed calculated by the second rotation speed calculation unit 15. This makes it possible to detect an abnormality in the current sensor even when the value of the output current is small, improving reliability.

[0037] The present invention is not limited to the above-described embodiments, and other forms that are conceivable within the scope of the technical idea of ​​the present invention are also included in the scope of the present invention as long as they do not impair the characteristics of the present invention. [Explanation of symbols]

[0038] 1...control unit, 11...angle sensor abnormality detection unit, 12...first rotation speed calculation unit, 13...pulse conversion unit, 14...counting unit, 15...second rotation speed calculation unit, 16...current sensor abnormality determination unit, 17...motor control unit, 2...inverter, 3, 31, 32, 33...current sensor, 4...motor, 41...angle sensor, 100...motor control device.

Claims

1. A current sensor abnormality detection device for a motor control device including an inverter that outputs power to a three-phase motor, a current sensor that detects an output current of each of the three phases output from the inverter to the motor, and a control unit that controls the inverter to drive the motor, a first rotation speed calculation unit that calculates a rotation speed of the motor based on an angle sensor provided in the motor; a second rotation speed calculation unit that calculates a rotation speed of the motor based on the three-phase output current detected by the current sensor; an abnormality determination unit that determines an abnormality in the current sensor based on the rotation speed calculated by the first rotation speed calculation unit and the rotation speed calculated by the second rotation speed calculation unit.

2. 2. The current sensor abnormality detection device according to claim 1, a pulse converter that generates a pulse wave for each phase based on a zero cross point of the output current for each phase detected by the current sensor; The second rotation speed calculation unit is a current sensor anomaly detection device that calculates the rotation speed of the motor based on the time required for a count value obtained by counting the rising timing of the pulse wave of each phase to reach a predetermined count value.

3. 2. The current sensor abnormality detection device according to claim 1, a pulse converter that generates a pulse wave for each phase based on a zero cross point of the output current for each phase detected by the current sensor; The second rotation speed calculation unit is a current sensor anomaly detection device that calculates the rotation speed of the motor based on the time required for a count value obtained by counting the rise and fall timings of the pulse waves of each phase to reach a predetermined count value.

4. The current sensor abnormality detection device according to any one of claims 1 to 3, the current sensor includes a first current sensor for detecting two phases of output current output from the inverter to the motor, and a second current sensor for detecting the remaining one phase of output current; The second current sensor is a current sensor abnormality detection device that detects at least the zero crossing point of the output current.

5. 5. The current sensor abnormality detection device according to claim 4, the first current sensor is a current sensor using a Hall element and a core, The second current sensor is a current sensor abnormality detection device using a coreless or shunt resistor.

6. The current sensor abnormality detection device according to any one of claims 1 to 3, The control unit is a current sensor abnormality detection device that controls the inverter using the value of the first current sensor.

7. 7. The current sensor abnormality detection device according to claim 6, The control unit includes an abnormality detection unit that detects an abnormality in the angle sensor, The abnormality determination unit is a current sensor abnormality detection device that determines whether the current sensor is abnormal when the abnormality detection unit does not detect an abnormality in the angle sensor.

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