Motor control device

Abstract

To estimate electric angular velocity of a rotor from a current value of each phase even in low-speed rotation and low-torque rotation of a motor.SOLUTION: A motor control device 1 controls current to be supplied to a motor on the basis of a current value of phase currents Iu, Iv, Iw of each phase detected by a current sensor 7 which detects the phase currents Iu, Iv, Iw flowing to each phase winding of a three-phase motor. The motor control device 1 comprises an electric angular velocity estimation unit 12 which estimates electric angular velocity in a rotor of the motor on the basis of a ratio between the current values of the phase currents Iu, Iv, Iw and second order differential values Iu",Iv", Iw" of the phase currents Iu, Iv, Iw to time of the current values.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an apparatus for controlling a motor. [Background technology]

[0002] Conventionally, synchronous motors driven by vector control have been increasingly adopted for motors used for driving automobiles, etc., in order to achieve miniaturization, high output, high efficiency, etc. In such synchronous motors, it is necessary to detect the rotor position in order to perform vector control, and the rotor position is generally detected using a rotational position sensor such as a resolver.

[0003] In recent years, in order to further reduce the size and cost of motors, a sensorless control method has been proposed that can determine the rotor position without using a rotational position sensor to control the drive of the motor. Regarding such sensorless control of motors, Patent Document 1 describes a motor drive device that performs an initial angle calculation process to detect the initial angle of the rotor based on the current flowing due to a voltage pulse applied to the stator coil, and a sensorless control process to estimate the angle and speed of the rotor based on the voltage applied to or the current flowing in the multi-phase coils of the motor after the angular speed of the rotor reaches a predetermined rotation speed, and to control the rotation of the rotor based on the estimated angle and speed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-208187 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the method described in Patent Document 1, the current flowing through each phase of a three-phase AC motor is detected by a shunt resistor, and the detected current value of each phase is subjected to coordinate conversion to calculate an excitation component current Id and a torque component current Iq. Then, based on these current values, an excitation component voltage Vd and a torque component voltage Vq, an estimated rotor speed and an estimated rotor position of the motor are calculated. However, with this method, it is difficult to estimate the electrical angular speed of the rotor when the motor is rotating at a low speed where the amount of current change per unit time is small, or when the motor is rotating at a low torque where the current flowing through the motor is small.

[0006] In order to solve the above problems, a main object of the present invention is to estimate the electrical angular velocity of a rotor from the current values ​​of each phase even when the motor is rotating at a low speed or with a low torque. [Means for solving the problem]

[0007] A motor control device according to the present invention controls the current supplied to a three-phase motor based on the current values ​​of phase currents of each phase detected by a current sensor that detects the phase currents flowing through each phase winding, and includes an electrical angular velocity estimator that estimates the electrical angular velocity of a rotor of the motor based on the ratio between the current values ​​and a second-order derivative of the current values ​​with respect to time. Effect of the Invention

[0008] According to the present invention, even when the motor is rotating at a low speed or with a low torque, the electrical angular velocity of the rotor can be estimated from the current values ​​of each phase. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing the overall configuration of a motor drive system including a motor control device according to an embodiment of the present invention; [Diagram 2] 1 is a block diagram showing a functional configuration of a motor control device according to an embodiment of the present invention; [Diagram 3] 4 is a diagram showing the relationship between the phase current of each phase and an electrical angular velocity estimate value calculated from the phase current of each phase; FIG. [Figure 4] 5 is a diagram showing how the phase current of each phase changes over time according to the rotation direction of the motor. FIG. [Diagram 5] A table summarizing the relationship between the magnitude of the phase current of each phase in each pattern and the sign of their differential values. [Figure 6] 11 is a table showing an example of an abnormality determination rule. [Figure 7] 4 is a flowchart showing an operation flow of a motor control device according to an embodiment of the present invention. [Figure 8] 4 is a flowchart showing an operation flow of a motor control device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, an example of application to a motor drive system mounted on and used in an electrically powered vehicle such as an electric vehicle or a hybrid vehicle will be described.

[0011] (Motor Drive System) Fig. 1 is an overall configuration diagram of a motor drive system including a motor control device according to an embodiment of the present invention. In Fig. 1, the motor drive system 100 includes a motor control device 1, an AC motor (hereinafter simply referred to as "motor") 2, an inverter 3, a rotation angle detector 4, and a high-voltage battery 5.

[0012] A target torque required for the motor 2, a voltage value (HVDC voltage) of the high-voltage battery 5, and a temperature (motor temperature) of the motor 2 are input to the motor control device 1 from a higher-level controller (not shown). The motor control device 1 controls the inverter 3 based on these input values, thereby generating a gate signal for controlling the current supplied to the motor 2. The generated gate signal is then output to the inverter 3. Details of the motor control device 1 will be described later.

[0013] The inverter 3 has an inverter circuit 31, a gate drive circuit 32, and a smoothing capacitor 33. The gate drive circuit 32 generates a gate drive signal for controlling each switching element of the inverter circuit 31 based on a gate signal input from the motor control device 1, and outputs the gate drive signal to the inverter circuit 31. The inverter circuit 31 has switching elements corresponding to the upper and lower arms of the U, V, and W phases, respectively. By controlling each of these switching elements according to the gate drive signal input from the gate drive circuit 32, the DC power supplied from the high-voltage battery 5 is converted into AC power and output to the motor 2. The smoothing capacitor 33 smoothes the DC power supplied from the high-voltage battery 5 to the inverter circuit 31.

[0014] The motor 2 is a three-phase synchronous motor that is rotationally driven by AC power supplied from the inverter 3, and has a stator and a rotor. When AC power input from the inverter 3 is applied to armature coils Lu, Lv, and Lw provided in the stator, three-phase AC currents (phase currents) Iu, Iv, and Iw are conducted in the motor 2, and armature magnetic flux is generated in each armature coil. Attractive and repulsive forces are generated between the armature magnetic flux of each armature coil and the magnetic flux of the permanent magnets arranged in the rotor, generating torque in the rotor and driving the rotor to rotate.

[0015] An angle sensor 8 for detecting the rotational position (electrical angle) of the rotor is attached to the motor 2. The rotational angle detector 4 calculates the rotational position from the input signal of the angle sensor 8 and outputs the calculation result as an electrical angle measurement value φs. The electrical angle measurement value φs obtained by the rotational angle detector 4 is input to the motor control device 1 and is used in the phase control of AC power that the motor control device 1 performs in accordance with the phase of the induced voltage of the motor 2.

[0016] Here, a resolver composed of an iron core and a winding is more suitable for the angle sensor 8, but a sensor using a magnetic resistance element such as a GMR sensor or a Hall element may also be used.

[0017] A current sensor 7 is disposed between the inverter 3 and the motor 2. The current sensor 7 detects phase currents Iu, Iv, Iw (U-phase current Iu, V-phase current Iv, and W-phase current Iw) flowing through the armature coils Lu, Lv, and Lw of each phase in response to the AC power supplied from the inverter 3 in the motor 2. The current sensor 7 is configured using, for example, a Hall current sensor. The detection results of the phase currents Iu, Iv, and Iw by the current sensor 7 are input to the motor control device 1, whereby the current values ​​of the phase currents Iu, Iv, and Iw are obtained in the motor control device 1. The obtained current values ​​of the phase currents Iu, Iv, and Iw are used for the phase control of the AC power performed by the motor control device 1, similarly to the electrical angle measurement value φs from the rotation angle detector 4. Note that, although FIG. 2 shows an example in which the current sensor 7 is configured with three current detectors, it is also possible to use two current detectors and calculate the current value of the remaining one phase because the sum of the three-phase AC currents Iu, Iv, and Iw is zero. In addition, the pulsed DC current flowing from the high-voltage battery 5 to the inverter 3 may be detected by a shunt resistor or the like inserted between the smoothing capacitor 33 and the inverter 3, and the current values ​​of each phase current Iu, Iv, Iw may be calculated based on this DC current and the three-phase AC voltages Vu, Vv, Vw applied from the inverter 3 to the motor 2.

[0018] (Motor control device) Next, the motor control device 1 will be described in detail. FIG. 2 is a block diagram showing a functional configuration of the motor control device 1 according to an embodiment of the present invention. In FIG. 2, the motor control device 1 has functional blocks of an electrical angular velocity calculation unit 11, an electrical angular velocity estimation unit 12, an electrical angle estimation unit 13, an abnormality determination unit 14, a mode selection unit 15, switching units 16 and 17, a dq axis conversion unit 18, a target dq axis current calculation unit 19, a voltage command calculation unit 20, a three-phase conversion unit 21, and a gate signal generation unit 22. The motor control device 1 is configured by, for example, a microcomputer, and these functional blocks can be realized by executing a predetermined program in the microcomputer. Alternatively, some or all of these functional blocks may be realized using hardware circuits such as logic ICs and FPGAs.

[0019] The electrical angular velocity calculation unit 11 calculates the electrical angular velocity of the rotor of the motor 2 from the change over time of the electrical angle measurement value φs obtained by the rotation angle detector 4. Then, the calculated value of the electrical angular velocity is output as the electrical angular velocity measurement value ωs to the abnormality determination unit 14 and the switching unit 16. Note that, when a resolver is used as the angle sensor 8 and an output signal from this resolver is converted into a digital signal by the rotation angle detector 4 and input to the motor control device 1, the electrical angular velocity calculation unit 11 may simultaneously calculate the electrical angle measurement value φs and the electrical angular velocity measurement value ωs by a tracking loop for that signal.

[0020] Electrical angular velocity estimation unit 12 acquires the current values ​​of phase currents Iu, Iv, Iw detected by current sensor 7, and estimates the electrical angular velocity of the rotor of motor 2 based on the current values. Then, the estimated result of the electrical angular velocity is output as an electrical angular velocity estimate value ωc to electrical angle estimation unit 13, abnormality determination unit 14, and switching unit 16. The method of estimating the electrical angular velocity by electrical angular velocity estimation unit 12 will be described in detail later.

[0021] The electrical angle estimator 13 estimates the electrical angle of the rotor of the motor 2 based on the current values ​​of the phase currents Iu, Iv, Iw detected by the current sensor 7 and the electrical angular velocity estimate value ωc obtained by the electrical angular velocity estimator 12. Then, the electrical angle estimation result is output to the switching unit 17 as an electrical angle estimate value φc. The method of estimating the electrical angle by the electrical angle estimator 13 will be described in detail later.

[0022] An abnormality determination unit 14 receives an abnormality diagnosis result for the current sensor 7 or the angle sensor 8 from a diagnostic device (not shown) provided outside the motor control device 1. Anomaly determination unit 14 determines an abnormality in either the current sensor 7 or the angle sensor 8 based on the abnormality diagnosis result from the external diagnostic device and the electrical angular velocity measurement value ωs and the electrical angular velocity estimation value ωc input from the electrical angular velocity calculation unit 11 and the electrical angular velocity estimation unit 12, respectively, and outputs a diagnosis result according to the determination result to each of the mode selection unit 15 and the switching units 16 and 17. The method of abnormality determination by abnormality determination unit 14 will be described in detail later.

[0023] Note that a diagnostic device external to the motor control device 1 can diagnose an abnormality in the current sensor 7 by, for example, comparing the detection results of the currents of the respective phases by the current sensor 7, or by using the sum of the currents of the respective phases. Also, it can diagnose an abnormality in the angle sensor 8 by, for example, using a change over time in the detection result of the rotational position by the angle sensor 8, or the sum of the squares of the rotational position. In addition to this, the external diagnostic device can diagnose an abnormality in the current sensor 7 and the angle sensor 8 by any method.

[0024] Based on the diagnosis result of the occurrence of an abnormality in the current sensor 7 and the angle sensor 8 input from the abnormality determination unit 14, the mode selection unit 15 generates a mode control signal for controlling the mode of the gate signal generated by the gate signal generation unit 22 when the motor 2 is driven, and outputs the generated mode control signal to the gate signal generation unit 22. Specifically, when the mode selection unit 15 receives a diagnosis result from the abnormality determination unit 14 that no abnormality has occurred in either the current sensor 7 or the angle sensor 8, the mode selection unit 15 outputs a signal instructing the gate signal generation unit 22 to perform normal PWM control (PWM mode) as a mode control signal. On the other hand, when the mode selection unit 15 receives a diagnosis result from the abnormality determination unit 14 that an abnormality has occurred in the angle sensor 8 and no abnormality has occurred in the current sensor 7 while the motor 2 is being driven (the rotor is rotating), the mode selection unit 15 outputs a signal instructing a mode in which the upper arm or the lower arm of the inverter circuit 31 is in a three-phase short-circuit state (three-phase short-circuit mode) in order to estimate the electrical angle by the electrical angle estimation unit 13. Thereafter, when the rotor position (electrical angle) is estimated by the electrical angle estimator 13 in the three-phase short circuit mode, the mode control signal is switched from the three-phase short circuit mode to the PWM mode, thereby allowing the electric vehicle to continue operating.

[0025] The switching unit 16 receives the measured electrical angular velocity ωs calculated by the electrical angular velocity calculation unit 11 and the estimated electrical angular velocity ωc calculated by the electrical angular velocity estimation unit 12. The switching unit 16 selects one of these input values ​​based on the diagnosis result by the abnormality determination unit 14, and outputs the selected value to the target dq-axis current calculation unit 19 as the electrical angular velocity ω of the rotor of the motor 2. Specifically, when the abnormality determination unit 14 outputs a diagnosis result indicating that there is no abnormality in both the current sensor 7 and the angle sensor 8, or that there is an abnormality in the angle sensor 8, the switching unit 16 selects the measured electrical angular velocity ωs and outputs it as the electrical angular velocity ω. On the other hand, when the abnormality determination unit 14 outputs a diagnosis result indicating that there is an abnormality in the angle sensor 8, the switching unit 16 selects the estimated electrical angular velocity ωc and outputs it as the electrical angular velocity ω. Note that when there is no abnormality in both the current sensor 7 and the angle sensor 8, the estimated electrical angular velocity ωc may be selected instead of the measured electrical angular velocity ωs.

[0026] The switching unit 17 receives the electrical angle measurement value φs obtained by the rotation angle detector 4 and the electrical angle estimate value φc calculated by the electrical angle estimation unit 13. The switching unit 17 selects one of these input values ​​based on the diagnosis result by the abnormality determination unit 14, and outputs the selected value to the dq-axis conversion unit 18 and the three-phase conversion unit 21 as the electrical angle φ representing the rotational position of the rotor of the motor 2. Specifically, when the abnormality determination unit 14 outputs a diagnosis result indicating that there is no abnormality in both the current sensor 7 and the angle sensor 8, or that there is an abnormality in the angle sensor 8, the switching unit 17 selects the electrical angle measurement value φs and outputs it as the electrical angle φ. On the other hand, when the abnormality determination unit 14 outputs a diagnosis result indicating that there is an abnormality in the angle sensor 8, the switching unit 17 selects the electrical angle estimate value φc and outputs it as the electrical angle φ. Note that when there is no abnormality in both the current sensor 7 and the angle sensor 8, the electrical angle estimate value φc may be selected instead of the electrical angle measurement value φs.

[0027] The dq-axis converter 18 performs dq conversion on the phase currents Iu, Iv, Iw detected by the current sensor 7 based on the electrical angle φ, and calculates the d-axis current value Id and the q-axis current value Iq based on the result of this dq conversion. Then, the calculated d-axis current value Id and q-axis current value Iq are output to the voltage command calculator 20.

[0028] The target dq-axis current calculation unit 19 calculates the target d-axis current Id* and the target q-axis current Iq* based on the target torque, HVDC voltage, motor temperature, and electrical angular velocity ω input to the motor control device 1. Here, the target d-axis current Id* and the target q-axis current Iq* according to the combination of the target torque, HVDC voltage, motor temperature, and electrical angular velocity ω are obtained by using, for example, a preset current command map or a calculation formula.

[0029] Based on the deviation between the target d-axis current Id* and the target q-axis current Iq* input from the target dq-axis current calculation unit 19 and the d-axis current value Id and the q-axis current value Iq input from the dq-axis conversion unit 18, the voltage command calculation unit 20 calculates a d-axis voltage command Vdc* and a q-axis voltage command Vqc* corresponding to the target torque so that these values ​​match each other. Here, the d-axis voltage command Vdc* corresponding to the deviation between the target d-axis current Id* and the d-axis current value Id and the q-axis voltage command Vqc* corresponding to the deviation between the target q-axis current Iq* and the q-axis current value Iq are calculated for each predetermined calculation period by current control calculation using a control method such as PI control.

[0030] The three-phase conversion unit 21 performs three-phase conversion based on the electrical angle φ on the d-axis voltage command Vdc* and the q-axis voltage command Vqc* input from the voltage command calculation unit 20, to determine the phase voltages Vu, Vv, Vw (U-phase voltage value Vu, V-phase voltage value Vv, and W-phase voltage value Vw) that the inverter circuit 31 should output to the motor 2.

[0031] The gate signal generation unit 22 performs PWM calculation based on the phase voltages Vu, Vv, Vw calculated by the three-phase conversion unit 21 to determine the pulse width of the gate drive signal to be output to each switching element of the inverter circuit 31, and generates gate signals Du, Dv, Dw for each phase according to the pulse width. Then, the generated gate signals Du, Dv, Dw are output to the gate drive circuit 32 of the inverter 3, thereby controlling the voltage output from the inverter 3 to the armature coils Lu, Lv, Lw of each phase of the motor 2. This allows the motor control device 1 to control the current supplied from the inverter 3 to the motor 2.

[0032] As described above, the gate signal generating unit 22 switches the method of generating the gate signals Du, Dv, and Dw depending on the mode control signal input from the mode selecting unit 15. That is, when a mode control signal instructing the PWM mode is input, the gate signals Du, Dv, and Dw are generated by performing PWM calculation based on the phase voltages Vu, Vv, and Vw as described above. On the other hand, when a mode control signal instructing the three-phase short circuit mode is input, the gate signals Du, Dv, and Dw are generated so that all of the upper arms or all of the lower arms of the inverter circuit 31 are turned on to achieve a three-phase short circuit state, regardless of the phase voltages Vu, Vv, and Vw.

[0033] (Method of estimating electrical angular velocity) Next, a method for estimating the electrical angular velocity by the electrical angular velocity estimator 12 will be described in detail.

[0034] The electrical angular velocity estimator 12 selects one of the phase currents Iu, Iv, and Iw detected by the current sensor 7, and calculates an estimate ωc of the electrical angular velocity from the current value of the selected phase current. Specifically, if the current value of the selected arbitrary phase current is Ix (x is one of u, v, or w), the electrical angular velocity estimate ωc can be obtained by performing, for example, the following calculation process.

[0035] If the electrical angular velocity of the rotor is denoted by an estimated electrical angular velocity ωc, the phase current value Ix, which changes periodically according to the rotor position, is expressed as a function of time t by the following equation (1): In equation (1), A represents the amplitude of the current value Ix. Ix = A * sin(ωc * t) (1)

[0036] From equation (1), the first derivative of the current value Ix is expressed by the following equation (2). Ix'=ωc*A*cos(ωc*t) ···(2)

[0037] Furthermore, from equation (2), the second derivative of the current value Ix is expressed by the following equation (3). Ix''=-ωc 2 *A*sin(ωc*t) (3)

[0038] By dividing equation (3) by equation (1), we obtain the following equation (4). ωc 2 =-Ix'' / Ix (4)

[0039] From equation (4), the following equation (5) is obtained. ωc=±√(-Ix'' / Ix) (5)

[0040] From equation (5), it can be seen that an estimated value ωc of the electrical angular velocity of the rotor of motor 2 can be found based on the ratio between current value Ix and second derivative value Ix″ of current value Ix with respect to time t.

[0041] The above formulas (1) to (5) are arithmetic expressions when the current value of the phase current is expressed by a continuous function Ix of time t. Here, when a discrete phase current value Ix(n) (n is an arbitrary natural number) obtained by acquiring the current value of an arbitrary phase current at a predetermined time interval is used, formulas (2) to (5) are converted to the following formulas (2)' to (5)', respectively. In formulas (2)' to (5)', t(n) and t(n-1) represent the times when the discrete phase current values ​​Ix(n) and Ix(n-1), respectively, are acquired. Ix'(n)={Ix(n)-Ix(n-1)} / {t(n)-t(n-1)} ...(2)' Ix''(n)={Ix'(n)-Ix'(n-1)} / {t(n)-t(n-1)} ...(3)' ωc(n) 2 =-Ix(n) / Ix(n) (4) ωc(n)=±√(-Ix''(n) / Ix(n)) ···(5)'

[0042] From equation (5)', it can be seen that, in the case of a continuous system as well as in the case of a discrete system, an estimate ωc(n) of the electrical angular speed of the rotor of motor 2 can be found based on the ratio between the discrete phase current value Ix(n) and the second derivative Ix''(n) of the discrete phase current value Ix(n) with respect to time t.

[0043] The electrical angular velocity estimator 12 can obtain the electrical angular velocity estimate ωc by performing the above calculation in either a continuous system or a discrete system using any one of the phase currents Iu, Iv, and Iw detected by the current sensor 7. Although an example of the continuous system will be described below, the same applies to the discrete system.

[0044] 3 is a diagram showing a relationship between the phase currents Iu, Iv, and Iw of each phase input to the electrical angular velocity estimator 12 and the electrical angular velocity estimate value ωc calculated from the phase currents Iu, Iv, and Iw of each phase. In FIG. 3, waveforms 41u, 41v, and 41w show examples of time changes of the phase currents Iu, Iv, and Iw, respectively. Moreover, waveforms 42u, 42v, and 42w show the electrical angular velocity estimate value ωc calculated by equation (5) for the phase currents Iu, Iv, and Iw shown in the waveforms 41u to 41w, respectively. From these waveforms, it can be seen that the absolute value of the calculated electrical angular velocity estimate value ωc becomes large near the zero crossing of the phase currents Iu, Iv, and Iw. In other words, it can be seen that the deviation from the original electrical angular velocity becomes large.

[0045] Therefore, in the electrical angular velocity estimator 12 of this embodiment, the phase having the largest current value among the phase currents Iu, Iv, and Iw is sequentially selected as the phase to be estimated for the electrical angular velocity, and the electrical angular velocity estimate value ωc is calculated by equation (5) based on the current value and second-order differential value of the selected phase. Specifically, for example, in a period 43 in which the value of the waveform 41u representing the phase current Iu among the waveforms 41u to 41w is the largest, the U phase is selected as the phase to be estimated for the electrical angular velocity, and the electrical angular velocity estimate value ωc is calculated by equation (5) using the phase current Iu of the U phase and its second-order differential value Iu″. Also, in a period 44 in which the value of the waveform 41v representing the phase current Iv is the largest, the V phase is selected as the phase to be estimated for the electrical angular velocity, and the electrical angular velocity estimate value ωc is calculated by equation (5) using the phase current Iv of the V phase and its second-order differential value Iv″. Similarly, in period 45 when the value of waveform 41w representing the phase current Iw is the largest, the W phase is selected as the phase to be estimated for the electrical angular velocity, and the W phase current Iw and its second-order differential value Iw″ are used to calculate the electrical angular velocity estimate ωc according to equation (5).

[0046] 3, waveform 46 is an example of an electrical angular velocity estimate ωc calculated by selecting the phase with the largest current value as the phase to be estimated for the electrical angular velocity as described above. It can be seen that the error of this electrical angular velocity estimate ωc is kept within a certain range with respect to the true value of the electrical angular velocity shown by line 47.

[0047] As described above, the electrical angular velocity estimator 12 can calculate the electrical angular velocity estimate ωc with high accuracy from the phase currents Iu, Iv, and Iw by switching the phase to be estimated for the electrical angular velocity at each time based on the magnitude of the phase current of each phase. Note that the error in the electrical angular velocity estimate ωc may be further reduced by performing processing such as applying a low-pass filter to the electrical angular velocity estimate ωc obtained by the electrical angular velocity estimator 12.

[0048] In the above, an example has been described in which the phase with the largest current value is selected as the phase to be estimated for the electrical angular velocity, but conversely, the phase with the smallest current value (the phase with the largest current value in the negative direction) may be selected as the phase to be estimated for the electrical angular velocity. Even if the phase with the second largest current value is selected instead of the phase with the largest current value, the phase current near the zero crossing can be excluded, and the same effect as above can be obtained. That is, the electrical angular velocity estimator 12 selects, at each predetermined calculation period, a phase with a current value that is larger in absolute value than at least one of the other phases among the three phases in which the phase currents Iu, Iv, and Iw are detected by the current sensor 7, and can estimate the electrical angular velocity of the motor 2 based on the current value and second-order differential value of the selected phase.

[0049] However, the sign of the electrical angular velocity estimate ωc calculated by equation (5) cannot be determined as it is. Therefore, the electrical angular velocity estimator 12 of this embodiment determines whether the sign of the electrical angular velocity estimate ωc is positive or negative by determining whether the rotation direction of the motor 2 is positive or negative. The method for doing so will be described below with reference to Figs. 4 and 5.

[0050] Fig. 4 is a diagram showing how the phase currents Iu, Iv, Iw of each phase change over time according to the rotation direction of the motor 2. In Fig. 4, (a) is a waveform example showing how the phase currents Iu, Iv, Iw change over time when the motor 2 is rotating in the positive direction, and (b) is a waveform example showing how the phase currents Iu, Iv, Iw change over time when the motor 2 is rotating in the negative direction. In these waveform examples, the magnitude relationship patterns of the phase currents Iu, Iv, Iw can be divided into the following six patterns. Pattern A: Iv≦Iw≦Iu Pattern B: Iw≦Iv≦Iu Pattern C: Iw≦Iu≦Iv Pattern D: Iu≦Iw≦Iv Pattern E: Iu≦Iv≦Iw Pattern F: Iv≦Iu≦Iw

[0051] As shown in Fig. 4(a) when the motor 2 is rotating in the forward direction, the magnitude relationship between the phase currents Iu, Iv, Iw changes in the order of patterns A, B, C, D, E, and F. On the other hand, as shown in Fig. 4(b) when the motor 2 is rotating in the reverse direction, the magnitude relationship between the phase currents Iu, Iv, Iw changes in the opposite order to that in Fig. 4(a), that is, in the order of patterns F, E, D, C, B, and A.

[0052] The signs of the differential values ​​Iu', Iv', Iw' of the phase currents Iu, Iv, Iw detected in each of the above patterns A to F are opposite during positive rotation and negative rotation. For example, in pattern A, during positive rotation, the signs of Iu' and Iv' are positive and the sign of Iw' is negative. On the other hand, during negative rotation, the signs of Iu' and Iv' are negative and the sign of Iw' is positive. The same is true for the other patterns.

[0053] 5 is a table summarizing the magnitude relationship of the phase currents Iu, Iv, Iw of each phase in each of the patterns described above and the signs of their differential values ​​Iu', Iv', Iw'. The electrical angular velocity estimator 12 of this embodiment can determine whether the rotation direction of the motor 2 is positive or negative from the table in FIG. 5 based on the phase currents Iu, Iv, Iw and the differential values ​​Iu', Iv', Iw'. That is, the electrical angular velocity estimator 12 can estimate the rotation direction of the rotor of the motor 2 based on the magnitude relationship of the current values ​​Iu, Iv, Iw of each phase and the positive or negative first-order differential values ​​Iu', Iv', Iw' of the current values ​​Iu, Iv, Iw with respect to time.

[0054] The differential values ​​Iu', Iv', Iw' actually found in the electrical angular velocity estimator 12 are discrete values ​​as expressed by the above-mentioned formula (2)'. Therefore, when the magnitude relationship between the phases crosses or when the differential value of each phase is inverted, the positive or negative value may not be correctly determined. In such a case, the current rotation direction may be determined from the previously estimated rotation direction by utilizing the characteristic that the rotation direction of the motor 2 does not suddenly change.

[0055] (Method of estimating electrical angle) Next, a method for estimating the electrical angle by the electrical angle estimator 13 will be described in detail.

[0056] The value of the electrical angle φ obtained the previous time the motor 2 was stopped is stored in the electrical angle estimator 13 as an initial electrical angle value φcs. When the motor 2 starts to drive, the initial electrical angle value φcs is used to determine an electrical angle estimate value φc according to the following equation (6). In equation (6), t represents the time elapsed since the motor 2 started to drive. φc=ωc*t+φcs (6)

[0057] In practice, the calculation of the electrical angle estimate φc in the electrical angle estimator 13 is performed at every predetermined calculation period Δt. Furthermore, since the electrical angular velocity of the motor 2 changes successively, the electrical angular velocity estimate ωc also changes at every calculation period. Therefore, the discrete system electrical angle estimate φc(n) in the current calculation is found by the following equation (6)' based on the previous electrical angle estimate φc(n-1) and the current electrical angular velocity estimate ωc(n). In equation (6)', the initial value φc(0) of the electrical angle estimate is the aforementioned initial value φcs stored in the electrical angle estimator 13. φc(n)=φc(n-1)+ωc(n)*Δt ···(6)'

[0058] Alternatively, when the motor 2 is being driven (the rotor is rotating), the upper arm or the lower arm of the inverter circuit 31 may be placed in a three-phase short-circuit state to generate an induced voltage in the armature coils Lu, Lv, Lw of the motor 2, and the electrical angle estimate value φc may be calculated based on the phases of the phase currents Iu, Iv, Iw generated by this induced voltage as follows:

[0059] The induced voltage E0x (x is u, v, or w) in a three-phase short circuit state can be expressed by the following equation (7) using the current value Ix of the corresponding phase. In equation (7), K represents the induced voltage constant, and R and L represent the inductance and resistance value of each phase of the motor 2, respectively. E0x=K*ωc*sin(ωx*t) =-{R*Ix+L*(dIx / dt)} (7)

[0060] From equation (7), the current value Ix can be expressed as in equation (8) below. Ix=(-K*ωc) / √{R 2 +(ωc*L) 2}*{e^(-R / L)*sinφi+sin(ωc*t-φi)} ···(8)

[0061] In equation (8), φi represents the phase difference between the induced voltage E0x and the current value Ix, and can be calculated using the following equation (9). φi=arctan(ωc*L / R) (9)

[0062] In equation (9), the inductance L and the resistance value R are physical property values ​​that depend on the motor temperature. Therefore, the electrical angle estimator 13 stores in advance the relationship between the motor temperature and the inductance L and the resistance value R, and can obtain the phase difference φi using equation (9) by obtaining the inductance L and the resistance value R according to the motor temperature from this relationship. Then, the phase of the induced voltage E0x can be obtained by subtracting the obtained phase difference φi from the phase of the current value Ix detected by the current sensor 7, and this can be output as the electrical angle estimate value φc.

[0063] Here, the phase difference φi expressed by the formula (9) can be said to be a value that depends on the electrical angular velocity ωc and the motor temperature. Therefore, instead of using the formula (9), a table with the electrical angular velocity ωc and the motor temperature as arguments may be stored in advance in the electrical angle estimator 13, and the phase difference φi may be calculated using this table.

[0064] After the three-phase short circuit mode ends, the electrical angle estimate value φc can be calculated using the electrical angle estimate value φc obtained during the three-phase short circuit mode as the initial electrical angle value φcs, using the above-mentioned equation (6) or equation (6)'.

[0065] (Abnormality determination method) Next, a method for determining whether or not an abnormality has occurred in the current sensor 7 and the angle sensor 8 by the abnormality determination unit 14 will be described in detail.

[0066] First, the abnormality determination unit 14 compares the electrical angular velocity measurement value ωs input from the electrical angular velocity calculation unit 11 with the electrical angular velocity estimation value ωc input from the electrical angular velocity estimation unit 12, and determines whether or not the difference between them is within a predetermined range. If the difference is within the predetermined range, the current sensor 7 and the angle sensor 8 are diagnosed as normal, and if it is outside the predetermined range, one of the current sensor 7 and the angle sensor 8 is diagnosed as abnormal.

[0067] Next, the abnormality determination unit 14 acquires the diagnosis result of the current sensor 7 or the angle sensor 8 by the external diagnostic device. Then, based on the above-mentioned diagnosis result by the abnormality determination unit 14 itself and the diagnosis result acquired from the external diagnostic device, the abnormality determination unit 14 determines the presence or absence of an abnormality in either the current sensor 7 or the angle sensor 8 by using a predetermined determination rule.

[0068] Fig. 6 is a table showing an example of an abnormality determination rule used by abnormality determination unit 14. Abnormality determination unit 14 can determine the presence or absence of an abnormality in current sensor 7 or angle sensor 8 from a combination of its own diagnosis result and the diagnosis result of an external diagnostic device, in accordance with the abnormality determination rule shown in the table of Fig. 6.

[0069] Specifically, for example, when the abnormality determination unit 14 obtains a diagnosis result of "normal" for the difference between the electrical angular velocity measurement value ωs and the electrical angular velocity estimation value ωc within a predetermined range and an external diagnostic device obtains a diagnosis result of "normal" for the angle sensor 8, it determines that both the current sensor 7 and the angle sensor 8 are normal, and when the angle sensor 8 obtains a diagnosis result of "abnormal" for the angle sensor 8, it determines that an abnormality has occurred in the angle sensor 8. On the other hand, when the abnormality determination unit 14 obtains a diagnosis result of "normal" for the difference between the electrical angular velocity measurement value ωs and the electrical angular velocity estimation value ωc within a predetermined range and an external diagnostic device obtains a diagnosis result of "normal" for the current sensor 7, it determines that both the current sensor 7 and the angle sensor 8 are normal, and when the current sensor 7 obtains a diagnosis result of "abnormal" for the current sensor 7, it determines that an abnormality has occurred in the current sensor 7.

[0070] Also, for example, if abnormality determination unit 14 obtains a diagnosis result of "abnormal" because the difference between the electrical angular velocity measurement value ωs and the electrical angular velocity estimation value ωc is outside a predetermined range, and an external diagnostic device obtains a diagnosis result of "normal" for angle sensor 8 or "abnormal" for current sensor 7, it is determined that an abnormality has occurred in current sensor 7. On the other hand, if abnormality determination unit 14 obtains a diagnosis result of "abnormal" because the difference between the electrical angular velocity measurement value ωs and the electrical angular velocity estimation value ωc is outside a predetermined range, and an external diagnostic device obtains a diagnosis result of "abnormal" for angle sensor 8 or "normal" for current sensor 7, it is determined that an abnormality has occurred in angle sensor 8.

[0071] The mode selection unit 15 acquires the diagnosis result of the abnormality determination unit 14 as described above, and when the diagnosis result indicates an abnormality in the angle sensor 8, that is, when the diagnosis result corresponds to the hatched column in the table of FIG. 6, the mode control signal is switched from the PWM mode to the three-phase short-circuit mode as necessary. For example, when the motor 2 is being driven and the initial value φcs of the electrical angle is not obtained in the electrical angle estimation unit 13, the mode control signal is switched to the three-phase short-circuit mode in order to obtain the phase of the induced voltage E0x by the above-mentioned method from the phase of the current value Ix detected by the current sensor 7 when the inverter circuit 31 is in a three-phase short-circuit state and calculate the electrical angle estimate value φc. As a result, even if an abnormality occurs in the angle sensor 8, the motor 2 can be continuously operated by using the electrical angular velocity estimate value ωc and the electrical angle estimate value φc calculated by the electrical angular velocity estimation unit 12 and the electrical angle estimation unit 13, respectively, and as a result, the availability of the motor drive system 100 can be improved.

[0072] (Operation flow) 7 and 8 are flowcharts showing the operation flow of the motor control device according to one embodiment of the present invention.

[0073] In step S10 in Fig. 7, the motor control device 1 determines whether the motor 2 is rotating. This determination process is performed using, for example, the more likely of the electrical angular velocity estimate ωc or the electrical angle estimate φc. If the motor 2 is rotating, the process proceeds to step S10, and if the motor 2 is stopped, the process proceeds to step S210 in Fig. 8.

[0074] In step S20, the motor control device 1 calculates the electrical angular velocity estimate ωc using the electrical angular velocity estimator 12. As described above, the motor control device 1 acquires a current value Ix of one of the three phase currents detected by the current sensor 7, and calculates the electrical angular velocity estimate ωc based on the ratio between this current value Ix and a second-order differential value Ix″ of the current value Ix. Furthermore, the motor control device 1 determines whether the sign of the electrical angular velocity estimate ωc is positive or negative by estimating the rotation direction of the rotor of the motor 2 based on the magnitude relationship between the current values ​​Iu, Iv, Iw of the respective phases and the positive or negative first-order differential values ​​Iu', Iv', Iw' of the current values ​​Iu, Iv, Iw with respect to time.

[0075] In step S30, the motor control device 1 performs an abnormality diagnosis by the abnormality determination unit 14. As described above, the electric angular velocity measurement value ωs calculated by the electric angular velocity calculation unit 11 is compared with the electric angular velocity estimation value ωc calculated in step S20, and it is determined whether the difference between them is within a predetermined range, thereby diagnosing whether the current sensor 7 or the angle sensor 8 is abnormal. In addition, the diagnosis results for the current sensor 7 or the angle sensor 8 by an external diagnosis device are obtained. Then, based on these diagnosis results, the determination rule in FIG. 6 is referenced to determine whether there is an abnormality in either the current sensor 7 or the angle sensor 8.

[0076] In step S40, the motor control device 1 determines whether the result of the abnormality diagnosis performed in step S30 is an angle sensor abnormality. If the result of the abnormality diagnosis in step S30 is an angle sensor abnormality, that is, if the angle sensor 8 is diagnosed as having an abnormality, the process proceeds to step S50, and if the result is otherwise, that is, if the angle sensor 8 is diagnosed as normal, the process proceeds to step S120.

[0077] In step S50, the motor control device 1 determines whether the result of the abnormality diagnosis performed in step S30 is that the current sensor is normal. If the result of the abnormality diagnosis in step S30 is that the current sensor is normal, i.e., the current sensor 7 is diagnosed as normal, the process proceeds to step S60, and if the result is otherwise, i.e., if the current sensor 7 is diagnosed as having an abnormality, the process proceeds to step S130.

[0078] In step S60, the motor control device 1 determines whether or not the initial value φcs of the electrical angle is stored in the electrical angle estimator 13. If the initial value φcs of the electrical angle is stored in the electrical angle estimator 13 and the electrical angle estimated value φc can be calculated using this value according to the above-mentioned equation (6) or (6)', the process proceeds to step S100, and if not, the process proceeds to step S70.

[0079] In step S70, the motor control device 1 sets the three-phase short-circuit mode. Here, the mode selection unit 15 outputs a mode control signal instructing the three-phase short-circuit mode to the gate signal generation unit 22, and in response to this, the gate signal generation unit 22 generates gate signals Du, Dv, and Dw so that all of the upper arms or all of the lower arms of the inverter circuit 31 are turned on to achieve a three-phase short-circuit state. When the gate signals Du, Dv, and Dw generated by the gate signal generation unit 22 are output in this manner to the inverter 3, one of the upper arms or the lower arms of each switching element of the inverter circuit 31 is switched on and the other is switched off in the inverter 3. As a result, a three-phase short-circuit state is achieved in which both ends of the armature coils Lu, Lv, and Lw of the motor 2 are electrically connected to each other via the upper arm or the lower arm of the inverter circuit 31.

[0080] In step S80, the motor control device 1 acquires the detection results of the phase currents when the inverter circuit 31 is in a three-phase short-circuit state from the current sensor 7. Then, the electrical angle estimator 13 calculates the electrical angle estimate value φc by determining the phase of the induced voltage E0x from the phase of the current value Ix of the acquired phase current as described above.

[0081] In step S90, the motor control device 1 sets the PWM mode. Here, a mode control signal instructing the PWM mode is output from the mode selection unit 15 to the gate signal generation unit 22, and in response to this, the gate signal generation unit 22 performs PWM calculation based on the phase voltages Vu, Vv, Vw determined by the three-phase conversion unit 21 to generate gate signals Du, Dv, Dw.

[0082] In step S100, the motor control device 1 causes the electrical angle estimator 13 to calculate the electrical angle estimate value φc using the initial electrical angle value φcs stored in the electrical angle estimator 13.

[0083] In step S110, the motor control device 1 continues to operate the motor 2 using the electrical angular velocity estimate ωc calculated by the electrical angular velocity estimator 12 in step S20 and the electrical angle estimate φc calculated by the electrical angle estimator 13 in step S80 or S100. Here, the switching unit 16 selects the electrical angular velocity estimate ωc and outputs it as the electrical angular velocity ω, and the switching unit 17 selects the electrical angle estimate φc and outputs it as the electrical angle φ. Then, the gate signal generator 22 performs PWM calculation based on the phase voltages Vu, Vv, Vw calculated using the electrical angular velocity ω and the electrical angle φ to generate gate signals Du, Dv, Dw and output them to the gate drive circuit 32 of the inverter 3, thereby controlling the current supplied from the inverter 3 to the motor 2 to drive the motor 2.

[0084] In step S120, the motor control device 1 continues to operate the motor 2 using the electrical angular velocity measurement value ωs calculated by the electrical angular velocity calculation unit 11 and the electrical angle measurement value φs output from the rotation angle detector 4. Here, the switching unit 16 selects the electrical angular velocity measurement value ωs and outputs it as the electrical angular velocity ω, and the switching unit 17 selects the electrical angle measurement value φs and outputs it as the electrical angle φ. Then, the gate signal generation unit 22 performs PWM calculation based on the phase voltages Vu, Vv, Vw calculated using the electrical angular velocity ω and the electrical angle φ to generate gate signals Du, Dv, Dw and output them to the gate drive circuit 32 of the inverter 3, thereby controlling the current supplied from the inverter 3 to the motor 2 to drive the motor 2.

[0085] In step S130, the motor control device 1 brings the motor 2 to an emergency stop. Here, both the current sensor 7 and the angle sensor 8 are abnormal, and the electrical angular velocity ω and the electrical angle φ cannot be obtained, so the output of the gate signals Du, Dv, and Dw to the gate drive circuit 32 is stopped to safely stop the motor 2.

[0086] After performing the process of step S110, S120, or S130, the motor control device 1 ends the operations shown in the flowcharts of Figures 7 and 8, and waits until the next calculation cycle. When the next calculation cycle arrives, the process is resumed from step S10 in Figure 7.

[0087] When the process proceeds from step S10 to step S210, in step S210 of Fig. 8, the motor control device 1 determines whether or not there is a request to start the stopped motor 2. For example, if a request to start the motor 2 is input to the motor control device 1 by a predetermined operation performed by the driver of an electric vehicle equipped with the motor drive system 100, the process proceeds to the next step S220, and if not, the process waits in step S210.

[0088] In step S220, the motor control device 1 determines whether or not the result of the most recent abnormality diagnosis by the abnormality determination unit 14 is an angle sensor abnormality. If the abnormality determination unit 14 has diagnosed the angle sensor as abnormal, i.e., that the angle sensor 8 is abnormal, the process proceeds to step S230, and otherwise, i.e., if the angle sensor 8 has been diagnosed as normal, the process proceeds to step S270. Note that if the result of the abnormality diagnosis by the abnormality determination unit 14 has not been obtained, the determination process of step S220 may be suspended until the result is obtained, or the angle sensor 8 may be determined to be normal and the process proceeds to step S270.

[0089] In step S230, the motor control device 1 determines whether the result of the most recent abnormality diagnosis by the abnormality determination unit 14 is that the current sensor is normal. If the abnormality determination unit 14 determines that the current sensor is normal, i.e., that the current sensor 7 is normal, the process proceeds to step S240, but otherwise, i.e., if the current sensor 7 is determined to be abnormal, the motor 2 is not started, the operation shown in the flowcharts of Figures 7 and 8 is terminated, and the motor control device 1 waits until the next calculation cycle. When the next calculation cycle begins, the process is resumed from step S10 in Figure 7.

[0090] In step S240, the motor control device 1 determines whether or not the initial value φcs of the electrical angle is stored in the electrical angle estimator 13. If the initial value φcs of the electrical angle is stored in the electrical angle estimator 13 and the electrical angle estimated value φc can be calculated using the above-mentioned equation (6) or (6)', the process proceeds to step S250, otherwise the motor 2 is not started and the operation shown in the flowcharts of Figures 7 and 8 is terminated, and the motor control device 1 waits until the next calculation cycle. When the next calculation cycle begins, the process is resumed from step S10 in Figure 7.

[0091] In step S250, the motor control device 1 causes the electrical angle estimator 13 to calculate the electrical angle estimate value φc using the initial value φcs of the electrical angle stored in the electrical angle estimator 13.

[0092] In step S260, the motor control device 1 starts the motor 2 using the electrical angular velocity estimate ωc calculated by the electrical angular velocity estimator 12 and the electrical angle estimate φc calculated by the electrical angle estimator 13 in step S250. Here, the switching unit 16 selects the electrical angular velocity estimate ωc and outputs it as the electrical angular velocity ω, and the switching unit 17 selects the electrical angle estimate φc and outputs it as the electrical angle φ. Then, the gate signal generator 22 performs PWM calculation based on the phase voltages Vu, Vv, Vw calculated using the electrical angular velocity ω and the electrical angle φ to generate gate signals Du, Dv, Dw and output them to the gate drive circuit 32 of the inverter 3, thereby controlling the current supplied from the inverter 3 to the motor 2 and starting the motor 2.

[0093] In step S270, the motor control device 1 starts the motor 2 using the electrical angular velocity measurement value ωs calculated by the electrical angular velocity calculation unit 11 and the electrical angle measurement value φs output from the rotation angle detector 4. Here, the switching unit 16 selects the electrical angular velocity measurement value ωs and outputs it as the electrical angular velocity ω, and the switching unit 17 selects the electrical angle measurement value φs and outputs it as the electrical angle φ. Then, the gate signal generation unit 22 performs PWM calculation based on the phase voltages Vu, Vv, Vw calculated using the electrical angular velocity ω and the electrical angle φ to generate gate signals Du, Dv, Dw and output them to the gate drive circuit 32 of the inverter 3, thereby controlling the current supplied from the inverter 3 to the motor 2 and starting the motor 2.

[0094] After performing the process of step S260 or S270, the motor control device 1 ends the operations shown in the flowcharts of Figures 7 and 8, and waits until the next calculation cycle. When the next calculation cycle arrives, the process resumes from step S10 in Figure 7.

[0095] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0096] (1) The motor control device 1 controls the current supplied to the motor 2 based on the current values ​​of the phase currents Iu, Iv, Iw of each phase detected by a current sensor 7 that detects the phase currents Iu, Iv, Iw flowing through each phase winding (armature coils Lu, Lv, Lw) of the three-phase motor 2. The motor control device 1 includes an electrical angular velocity estimation unit 12 that estimates the electrical angular velocity of the rotor of the motor 2 based on the ratio between the current values ​​of the phase currents Iu, Iv, Iw and second-order derivative values ​​Iu'',Iv'',Iw'' of the current values ​​of the phase currents Iu, Iv, Iw with respect to time. As a result, the electrical angular velocity of the rotor can be estimated from the current values ​​of each phase even when the motor 2 is rotating at a low speed or with a low torque.

[0097] (2) The electrical angular velocity estimator 12 selects a phase having a current value greater than that of at least one of the other phases among the three phases in which the phase currents Iu, Iv, and Iw are detected, for each predetermined calculation period, and estimates the electrical angular velocity based on the current value and second-order differential value of the selected phase. In this way, the electrical angular velocity can be estimated while excluding the phase current near the zero crossing, and therefore the electrical angular velocity of the motor 2 can be estimated.

[0098] (3) The electrical angular velocity estimator 12 estimates the rotation direction of the rotor based on the magnitude relationship between the phase currents Iu, Iv, Iw of each phase and the positive or negative first derivatives Iu', Iv', Iw' of the phase currents Iu, Iv, Iw of each phase with respect to time. This makes it possible to correctly estimate whether the sign of the electrical angular velocity of the rotor is positive or negative.

[0099] (4) The motor control device 1 includes an electrical angular velocity calculation unit 11 that calculates an electrical angular velocity based on the position of the rotor detected by an angle sensor 8 that measures the position of the rotor of the motor 2, and an abnormality determination unit 14 that compares the electrical angular velocity estimated by the electrical angular velocity estimation unit 12 (electrical angular velocity estimated value ωc) with the electrical angular velocity calculated by the electrical angular velocity calculation unit 11 (electrical angular velocity measured value ωs) and determines an abnormality in either the angle sensor 8 or the current sensor 7 based on the result of the comparison. As a result of this configuration, when an abnormality occurs in either the angle sensor 8 or the current sensor 7, the abnormality can be reliably detected.

[0100] (5) The abnormality determination unit 14 acquires abnormality diagnosis results for the angle sensor 8 and the current sensor 7 by an external diagnostic device, and based on the acquired abnormality diagnosis results and the result of comparison between the electrical angular velocity estimate value ωc and the electrical angular velocity measurement value ωs, if an abnormality occurs in either the current sensor 7 or the angle sensor 8, the location of the abnormality can be identified according to the determination rules shown in the table of Fig. 6. As a result, if an abnormality occurs in either the angle sensor 8 or the current sensor 7, the location of the abnormality can be identified reliably.

[0101] (6) When the abnormality determination unit 14 determines that an abnormality has occurred in the angle sensor 8 (step S40: Yes or step S220: Yes), the motor control device 1 continues the operation of the motor 2 using the electrical angular velocity estimated by the electrical angular velocity estimator 12 (electrical angular velocity estimated value ωc) (steps S110, S260). As a result, even if an abnormality has occurred in the angle sensor 8, the operation of the motor 2 can be continued.

[0102] (7) The motor control device 1 includes an electrical angle estimator 13 that estimates the electrical angle of the rotor of the motor 2 based on the phases of the phase currents Iu, Iv, Iw in a three-phase short-circuit state in which both ends of each phase winding (armature coils Lu, Lv, Lw) of the three-phase motor 2 are electrically connected to each other. As a result, even if an abnormality occurs in the angle sensor 8, the electrical angle can be estimated and the operation of the motor 2 can be continued.

[0103] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0104] 1...motor control device, 2...motor, 3...inverter, 4...rotation angle detector, 5...high voltage battery, 7...current sensor, 8...angle sensor, 11...electrical angular velocity calculation unit, 12...electrical angular velocity estimation unit, 13...electrical angle estimation unit, 14...abnormality determination unit, 15...mode selection unit, 16, 17...switching unit, 18...dq axis conversion unit, 19...target dq axis current calculation unit, 20...voltage command calculation unit, 21...three-phase conversion unit, 22...gate signal generation unit, 31...inverter circuit, 32...gate drive circuit, 33...smoothing capacitor, 100...motor drive system

Claims

1. 1. A motor control device that controls a current supplied to a three-phase motor based on a current value of a phase current of each phase detected by a current sensor that detects a phase current flowing through each phase winding of the motor, comprising: a motor control device comprising an electrical angular velocity estimator that estimates an electrical angular velocity of a rotor of the motor based on a ratio between the current value and a second-order derivative of the current value with respect to time.

2. 2. The motor control device according to claim 1, The motor control device, for each predetermined calculation period, the electrical angular velocity estimator selects a phase among the three phases in which the phase current has been detected, the absolute value of the current value being greater than that of at least any other phase, and estimates the electrical angular velocity based on the current value and the second-order differential value of the selected phase.

3. 2. The motor control device according to claim 1, The motor control device, wherein the electrical angular velocity estimator estimates a rotation direction of the rotor based on a magnitude relationship between the current values ​​of the phase currents of each phase and a positive or negative first-order derivative of the current values ​​with respect to time.

4. 2. The motor control device according to claim 1, an electrical angular velocity calculation unit that calculates the electrical angular velocity based on a position of the rotor detected by an angle sensor that measures a position of the rotor of the motor; an abnormality determination unit that compares the electrical angular velocity estimated by the electrical angular velocity estimation unit with the electrical angular velocity calculated by the electrical angular velocity calculation unit, and determines an abnormality in either the angle sensor or the current sensor based on a result of the comparison.

5. 5. The motor control device according to claim 4, The abnormality judgment unit acquires abnormality diagnosis results for each of the angle sensor and the current sensor by an external diagnostic device, and based on the acquired abnormality diagnosis results and the result of the comparison, if an abnormality has occurred in either the current sensor or the angle sensor, identifies the location of the abnormality.

6. 6. The motor control device according to claim 5, A motor control device that continues operation of the motor using the electrical angular velocity estimated by the electrical angular velocity estimation unit when the abnormality determination unit determines that an abnormality has occurred in the angle sensor.

7. 2. The motor control device according to claim 1, a motor control device comprising: an electrical angle estimator that estimates an electrical angle of a rotor of the motor based on a phase of the phase current in a three-phase short-circuit state in which both ends of each phase winding of the three-phase motor are electrically connected to each other.

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