JP6683064B2 - Motor control device - Google Patents

Description

  The technique disclosed in the present specification relates to a motor control device that controls a motor for running an electric vehicle. The "electric vehicle" in this specification includes a hybrid vehicle including both a motor and an engine, and a fuel cell vehicle.

  Rectangular wave control and PWM control are known as typical control rules for a traveling motor. The rectangular wave control is suitable for high output, but has a drawback that it is apt to cause overcurrent. The PWM control has an advantage that it has good controllability, but has a disadvantage that it is not suitable for high output because of limited voltage utilization rate. Patent Documents 1 and 2 disclose a motor control device that switches the control law of a traveling motor according to the situation. The motor control device of Patent Document 1 switches from rectangular wave control to PWM control when the voltage phase according to the rotation speed of the motor becomes equal to or lower than a predetermined lower limit curve. The motor control device of Patent Document 2 switches between rectangular wave control and PWM control based on the relationship between the input voltage to the inverter and the required voltage required for the motor. Although detailed description is omitted, the techniques of all the documents aim at suppressing overcurrent.

JP, 2013-074734, A JP2012-060710A

  Since both the rectangular wave control law and the PWM control law require the rotation angle of the motor, the motor control device includes means for acquiring the rotation angle of the motor. A resolver / digital converter that outputs an estimated value of a rotation angle of a motor based on an analog output of a resolver attached to a rotation shaft of the motor is known as a typical means for acquiring the rotation angle. The resolver / digital converter multiplies the error between the analog data including the information on the rotation angle of the motor obtained from the resolver and the estimated value of the rotation angle of the motor specified in the past control cycle by the gain for each control cycle, and calculates the error. The estimated value in the present control cycle is calculated so that becomes smaller. In some resolver / digital converters, the gain that multiplies the error when the error from the true value of the rotation angle of the motor included in the estimated value is larger than a specific error threshold, and the gain when the error is smaller than the error threshold, Some have adopted variable gain control to make them larger. Oscillation becomes easier when the gain is increased, but by increasing the gain only when the error is large and returning the gain when the error is small, the large error is quickly reduced while suppressing the oscillation, and the estimated value becomes true. Approaches the value. When the gain is increased, the error quickly decreases, which means that the estimated value which is the output of the resolver / digital converter changes abruptly.

  If the above error in the resolver / digital converter becomes large due to some factor while controlling the motor according to the rectangular wave control law, the resolver / digital converter switches from a small gain to a large gain. On the other hand, when the error becomes large, the estimated value of the rotation speed, which is the deciding factor of the output of the motor control device (drive power to the motor), deviates greatly from the true value of the rotation speed, so that the drive power to the motor becomes inappropriate The current of the drive power to the motor (motor current) is disturbed. When the current of the motor is disturbed and exceeds the threshold value for overcurrent prevention, the motor control device switches the control law from rectangular wave control to PWM control. The motor current is also transiently disturbed by switching the control law. At the same time, the estimated value of the rotation angle suddenly changes because the gain of the resolver / digital converter increases. If the estimated value, which is a deciding factor of the drive power to the motor, changes suddenly at the same time as the switching of the control law, the disturbance of the motor current becomes further large, and the possibility of an overcurrent flowing increases. There is a demand for a technique for preventing the gain switching of the resolver / digital converter and the switching of the motor control law from occurring at the same time.

  The motor control device disclosed in the present specification includes a resolver / digital converter and a controller. The resolver / digital converter outputs an estimated value of the rotation angle of the motor based on the output of the resolver attached to the traveling motor. The controller controls the motor based on the estimated value output from the resolver / digital converter according to one of the PWM control law and the rectangular wave control law. The resolver / digital converter multiplies the error between the measured value including the rotation angle of the motor obtained from the output of the resolver and the estimated value of the rotation angle specified in the past control cycle by the gain for each control cycle, and the error is calculated. The estimated value of the rotation angle in the current control cycle is specified so that it becomes smaller. The resolver / digital converter employs variable gain control in which the gain to be multiplied when the error is larger than the first error threshold is made larger than the gain to be multiplied when the error is smaller than the first error threshold. Then, when the controller controls the motor by the rectangular wave control, if the error in the resolver / digital converter exceeds the second error threshold value that is smaller than the first error threshold value, the controller applies the rectangular wave control method to the motor. The control is switched to the PWM control law.

  The motor control device disclosed in the present specification switches the control law of the motor before the resolver / digital converter switches the gain. Therefore, switching of the gain and switching of the control law do not occur at the same time. Note that there are two types of PWM control, sine wave PWM control and overmodulation PWM control, but the PWM control adopted by the motor control device disclosed in this specification may be either of them. Details of the technology disclosed in the present specification and further improvements will be described in the following “Description of Embodiments”.

It is a block diagram of the electric power system of the electric vehicle including the motor control device of the embodiment. It is a block diagram of a resolver / digital converter. It is a block diagram of a compensator. It is a flow chart of processing which a controller performs. It is a flow chart of processing of a modification which a controller performs.

  A motor control device according to an embodiment will be described with reference to the drawings. FIG. 1 shows a block diagram of a power system of an electric vehicle 2 including a motor control device 10. The electric vehicle 2 of the embodiment has a motor 6 for traveling. The motor 6 may generate electric power using the kinetic energy of the vehicle.

  The motor control device 10 converts the DC power of the battery 3 into AC and supplies the AC power to the motor 6. The motor control device 10 includes an inverter circuit 4, a current sensor 5, a resolver / digital converter 20, and a controller 30. Hereinafter, for the sake of simplicity, the “resolver / digital converter 20” will be referred to as the “R / D converter 20”.

  Since the structure of the inverter circuit 4 is well known, detailed illustration and description thereof will be omitted. Here, the outline of the inverter circuit 4 will be described. The inverter circuit 4 has a configuration in which three sets of two power transistors are mainly connected in parallel and connected in parallel. By appropriately turning on and off each power transistor, alternating current is output from the midpoint of each series connection. The power transistor group of the inverter circuit 4 is driven by the drive signal from the controller 30. The controller 30 receives the target output of the motor 6 from the higher-order controller 8 and determines a drive signal to each power transistor so that the target output is realized. The controller 30 monitors the output current of the inverter circuit 4 by the current sensor 5, and adjusts the drive signal of each power transistor by feedback control so that the output current matches the target output. The host controller 8 determines the target output of the motor 6 based on the data from the remaining amount sensor 91 that measures the remaining amount of the battery 3, the accelerator pedal 92, the brake pedal 93, and the vehicle speed sensor 94. 10 to the controller 30.

  The upper controller 8 may determine the electric power (regenerative electric power) to be generated by the motor 6 according to the depression amount of the brake pedal 93, and may output the regenerative electric power as a target output. In that case, the target output is a negative value. The controller 30 of the motor control device 10 generates a drive signal for each power transistor so that the inverter circuit 4 converts the AC regenerative power generated by the motor 6 into DC power.

  The controller 30 generates a drive signal for each power transistor based on the rotation angle of the motor 6. The rotation angle of the motor 6 is obtained by the resolver 7 attached to the rotation angle of the motor 6 and the R / D converter 20. The rotation angle obtained by the resolver 7 and the R / D converter 20 includes an error from the true value. Therefore, more accurately, the value obtained by the resolver 7 and the R / D converter 20 is an estimated value of the rotation angle of the motor 6. Since the error from the true value of the rotation angle will be referred to later, the term “estimated value” will be used below.

  The drive signal to each power transistor may be generated by the PWM control law or may be generated by the rectangular wave control immediately. The PWM control law and the rectangular wave control law are well known, so a detailed description will be omitted. Further, the controller 30 appropriately switches the PWM control law and the rectangular wave control law based on the magnitude of the target output and the current value of the drive power (AC power) supplied to the motor 6. Hereinafter, controlling the motor 6 based on the PWM control law will be referred to as a PWM control mode, and controlling the motor 6 based on the rectangular wave control law will be referred to as a rectangular wave control mode. The controller 30 can switch between the PWM control mode and the rectangular wave control mode according to various conditions. One of the conditions for the controller 30 to switch from the rectangular wave control mode to the PWM control mode is when the supply current to the motor 6 measured by the current sensor 5 exceeds a predetermined threshold value. This condition is for preventing overcurrent from flowing through the inverter circuit 4 and the motor 6. In general, overcurrent is less likely to occur in the PWM control mode (PWM control law) than in the rectangular wave control mode (rectangular wave control law).

  As another condition for switching from the rectangular wave control mode to the PWM control mode, the controller 30 controls the rectangular shape even when the current supplied to the motor 6 is likely to be an overcurrent due to the operation of the R / D converter 20. Switch from the wave control mode to the PWM control mode. Hereinafter, the switching will be referred to as “R / D converter interlocking mode switching”. The operation of the R / D converter and the R / D converter interlocking mode switching will be described below.

  First, the R / D converter 20 will be described. FIG. 2 shows a block diagram of the R / D converter 20. The R / D converter 20 outputs the estimated value As of the rotation angle of the motor 6 based on the analog output of the resolver 7. The R / D converter 20 is provided with an excitation signal generator 23, and supplies an excitation signal to the resolver 7. The excitation signal is a sine value (sin (wt), "t" represents time) of a predetermined angular velocity w. The angular velocity w is set to a value much larger than the maximum angular velocity of the motor 6. The resolver 7 has two coils, and each coil is arranged adjacent to the rotation shaft of the motor 6. A permanent magnet is attached to the rotating shaft of the motor 6, and magnetically interferes with the coil as the motor 6 rotates. The two coils are arranged so as to be 90 degrees out of phase with the rotation axis of the motor 6. Excitation signals are supplied to the two coils. When the angle of the rotation axis of the motor 6 is “Ar”, the excitation signal sin (wt) flowing in the coil is modulated by the angle Ar. The outputs of the two coils are K · sin (Ar) · sin (wt) and K · cos (Ar) · sin (wt). These values are analog data. That is, the output of the resolver 7 is analog data including information on the true value Ar of the rotation angle of the motor 6. Note that “K” is a constant gain.

  The two analog output values of the resolver 7 are input to the multipliers 21 and 22, respectively. The estimated values As of the rotation angle specified in the previous control cycle are input to the multipliers 21 and 22. In the multiplier 21, the analog output “K · sin (Ar) · sin (wt)” of the resolver 7 is multiplied by the cosine (cos (As)) of the estimated value As. The output of the multiplier 21 is “K · sin (Ar) · sin (wt) · cos (As)”. In the multiplier 22, the analog output “K · cos (Ar) · sin (wt)” of the resolver 7 is multiplied by the sine (sin (As)) of the estimated value As. The output of the multiplier 22 is “K · cos (Ar) · sin (wt) · sin (As)”.

  The outputs of the multiplier 21 and the multiplier 22 are input to the differencer 28. According to the cosine theorem, the difference between the outputs of the multiplier 21 and the multiplier 22 is “K · sin (Ar−As) · sin (wt)”. The output of the differentiator 28 is input to the comparator 29, encoded, and converted from analog data to digital data.

  The digitized output of the differentiator 28 (output of the comparator 29) is input to the synchronous detector 24. The excitation signal “sin (wt)” is also input to the synchronous detector 24 from the excitation signal generator 23. In the synchronous detector 24, the excitation signal component is removed from the digitized output of the differentiator 28. The result is "K.sin (Ar-As)". The output of the synchronous detector 24 becomes a function of the difference between the true value Ar of the rotation angle of the motor 6 and the previous estimated value As of the rotation angle, that is, an estimated value including an error.

  The output of the synchronous detector 24 is input to the compensator 25. In the compensator 25, the error between the true value Ar of the rotation angle and the previous estimated value As is integrated by the control period. The output of the compensator 25 becomes an error for one control cycle of the R / D converter 20. The error amount is input to the counter 26. The counter 26 adds the current error (output of the compensator 25) to the previous estimated value As. The output of the counter 26 becomes the estimated value As of the rotation angle in the current control cycle.

  FIG. 3 shows a block diagram of the compensator 25. The compensator 25 has a configuration of a type 2 direct connection servo loop under PI control. The proportional gain Kv of the amplifier 251 and the integration time constant Ti of the integrator 252 determine the characteristic of the compensator 25. The code “s” in the integrator 252 is a Laplace operator. The integrator 252 calculates the error increment from the previous control cycle of the R / D converter 20 to the current control cycle. The value obtained by multiplying the output (error) of the synchronous detector 24 by the proportional gain Kv is added by the adder 253 with the increment of the error for one control period by the integrator 252 and output to the counter 26. As described above, the counter 26 adds the integrated value of the error up to the current control cycle to the estimated value. The result is the estimated value As of the rotation angle in the current control cycle.

  The compensator 25 is characterized in that the proportional gain Kv is variable. The compensator 25 includes a gain adjuster 254, and the output of the synchronous detector 24 is also input to the gain adjuster 254. When the difference (error) between the true value Ar of the rotation angle and the previous estimated value As exceeds the first error threshold, the gain adjuster 254 sets the proportional gain Kv to the first gain Kv1 that is larger than the first gain Kv1. Change to 2 gain Kv2. In other words, the gain adjuster 254 sets the second gain Kv2 to the proportional gain Kv while the difference (error) between the true value Ar of the rotation angle and the previous estimated value As exceeds the first error threshold. Then, while it is below the first error threshold, the first gain Kv1 is set to the proportional gain Kv. The second gain Kv2 is larger than the first gain Kv1. The second gain Kv2 is, for example, 30 times the first gain Kv1.

  The compensator 25 adopting the variable gain control has the following advantages. Generally, when the proportional gain is increased, the response becomes faster, but the oscillation becomes easier. The compensator 25 increases the proportional gain Kv and reduces the error quickly while the error between the true value Ar of the rotation angle and the previous estimated value As is larger than the first error threshold. On the other hand, when the error is below the first error threshold, the proportional gain Kv is reduced to suppress oscillation.

  The features of the compensator 25, that is, the features of the R / D converter 20 are summarized as follows. The R / D converter 20 sets the proportional gain Kv to the error between the true value Ar of the rotation angle of the motor obtained from the output of the resolver 7 and the estimated value As of the rotation angle identified in the past control cycle for each control cycle. A compensator 25 is provided to specify the estimated value As of the rotation angle of the motor 6 in the current control cycle so that the error is reduced by multiplication. The compensator 25 makes the proportional gain (second gain Kv2) multiplied when the error is larger than the first error threshold larger than the gain (first gain Kv1) multiplied when the error is smaller than the first error threshold. Uses variable gain control.

  It should be noted that when the proportional gain Kv is increased, the error is rapidly reduced within a number of control cycle repetitions (a number of rotation angle estimations). This means that the estimated value As of the rotation angle suddenly changes. The sudden change in the estimated value As at this time is a change due to the software processing of the compensator 25, and the band thereof is physically higher than the band of the change in the rotation angle of the motor 6.

  The R / D converter interlocking mode switching executed by the controller 30 will be described. As described above, the controller 30 switches from the rectangular wave control mode to the PWM control mode when there is a high possibility that the current supplied to the motor 6 will be an overcurrent due to the operation of the R / D converter 20. . The R / D converter 20 changes the proportional gain Kv of the compensator 25 from the first gain Kv1 to the second gain Kv2 when the error between the true value Ar of the rotation angle of the motor 6 and the estimated value As exceeds a first error threshold. To do. Here, the first gain Kv1 is a proportional gain when the error is smaller than the first error threshold, and the second gain Kv2 is larger than the first gain Kv1. During execution of the rectangular wave control mode, the controller 30 sets the control mode to the PWM control mode when the error between the true value Ar of the rotation angle and the estimated value As exceeds a second error threshold smaller than the first error threshold. Switch. Note that, due to this processing, the controller 30 receives the data of the error between the true value Ar of the rotation angle and the estimated value As from the R / D converter 20.

  FIG. 4 shows a flowchart of the above-mentioned processing (R / D converter interlocking mode switching processing). The process of FIG. 4 is executed every control cycle. The controller 30 first confirms whether or not the current control mode of the motor 6 is the rectangular wave control mode (S2). When the current control mode is the rectangular wave control mode (S2: YES), the controller 30 checks whether the error received from the R / D converter 20 exceeds the second error threshold (S3). . When the error received from the R / D converter 20 exceeds the second error threshold (S3: YES), the controller 30 switches the control mode from the rectangular wave control mode to the PWM control mode (S4). Here, the "error" is the difference between the true value Ar of the rotation angle of the motor 6 and the estimated value As in the previous control cycle, as described above.

  The R / D converter interlocking mode switching process contributes to the prevention of overcurrent of the motor 6 (inverter circuit 4). The reason will be described. The motor control device 10 switches the rectangular wave control mode and the PWM control mode under predetermined conditions to drive the inverter circuit 4. Specifically, in a rectangular wave control mode in which an overcurrent is likely to occur, when there is a high possibility of overcurrent (or when an overcurrent occurs), in order to prevent overcurrent, from the rectangular wave control mode, Switch to the PWM control mode in which overcurrent is relatively unlikely to occur. One of the situations in which overcurrent is likely to occur is when the R / D converter 20 that employs variable gain control switches the proportional gain from a small value to a large value. This is for the following reason. The R / D converter 20 increases the gain when the error between the true value Ar of the rotation speed of the motor 6 and its estimated value As exceeds the first error threshold. One of the situations where the error becomes large is when the accelerator pedal is depressed and the output torque required for the motor 6 becomes large. In that case, the number of rotations of the motor 6 is accelerated, so that the error becomes large.

  Immediately after the R / D converter 20 changes the gain, the error rapidly decreases. With the rapid reduction of the error, the output of the R / D converter 20, that is, the estimated value As of the rotation angle suddenly changes. The controller 30 generates a drive signal for the power transistor of the inverter circuit 4 based on the estimated value As of the rotation angle. The fact that the estimated value As includes a large error means that the appropriateness of the drive signal to the power transistor is reduced. At this point, overcurrent is already likely to occur. Further, the sudden change in the estimated value As causes a sudden change in the drive signal, which disturbs the drive signal and disturbs the current supplied to the motor 6. Here, when the current of the motor 6 exceeds the current threshold for preventing overcurrent, the controller 30 switches from the rectangular wave control mode to the PWM control mode. The current to the motor 6 is disturbed even during the transition period of switching the control mode. If the gain switching in the R / D converter 20 occurs during traveling, the control mode may be switched at the same time, and at that time, overcurrent is likely to occur.

  Therefore, in the R / D converter interlocking mode switching process, the controller 30 switches the control mode to the PWM control mode before the error of the rotation angle exceeds the first error threshold value at which the gain switching occurs. By the R / D converter interlocking mode switching process, switching of the gain and switching of the control mode are avoided at the same time, which contributes to prevention of overcurrent.

  Next, a modified example in which the mode switching condition is limited so that the R / D converter interlocking mode switching process does not occur frequently will be described. FIG. 5 shows a flowchart of the R / D converter interlocking mode switching process of the modified example. Overcurrent is likely to occur when relatively large electric power is supplied to the motor 6. A typical example of such a case is when the accelerator pedal depression amount is relatively large and the vehicle is accelerating. Therefore, in the flowchart of FIG. 5, the condition for mode switching is limited to the case of acceleration in the rectangular wave control mode (S22). Other processes (S23, S24) are the same as the processes (S3, S4) in the flowchart of FIG. In this modification, the control mode is not switched during deceleration in which an overcurrent is unlikely to occur.

  Instead of the process of step S22, if the current is being controlled in the rectangular wave control mode and the current supplied to the motor 6 exceeds a predetermined current threshold, the process may proceed to step S23. Good. This is because if the current supplied to the motor 6 is originally small, overcurrent is unlikely to occur. Since the current measured by the current sensor 5 is alternating current, “when the current exceeds the predetermined current threshold” means that the effective value of the alternating current exceeds the current threshold.

  Points to be noted regarding the technique described in the embodiment will be described. The PWM control includes sine wave PWM control and overmodulation PWM control, but any PWM control adopted by the motor control device 10 may be used. The technique disclosed in this specification is also suitable for application to a hybrid vehicle or a fuel cell vehicle that includes both an engine and a motor for traveling.

  The proportional gain Kv of the compensator 25 in the embodiment corresponds to an example of “gain” in the claims. The “compensator” in the claims only needs to reduce the error between the true value of the rotation angle and the estimated value, and is not limited to the configuration of the compensator 25 of the embodiment.

  Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in the present specification or the drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technique illustrated in the present specification or the drawings can simultaneously achieve a plurality of objects, and achieving the one object among them has technical utility.

2: Electric vehicle 3: Battery 4: Inverter circuit 5: Current sensor 6: Motor 7: Resolver 8: Controller 10: Motor controller 20: Resolver / digital converter (R / D converter)
21, 22: Multiplier 23: Excitation signal generator 24: Synchronous detector 25: Compensator 26: Counter 28: Differencer 29: Comparator 30: Controller 91: Remaining amount sensor 92: Accelerator pedal 93: Brake pedal 94: Vehicle speed sensor 251: Amplifier 252: Integrator 253: Adder 254: Gain adjuster

Claims (1)

A motor control device for controlling a motor for running an electric vehicle,
A resolver / digital converter that outputs an estimated value of a rotation angle of the motor based on an output of a resolver attached to the motor;
A controller that controls the motor according to one of the PWM control law and the rectangular wave control law based on the estimated value;
Is equipped with
The resolver / digital converter multiplies the error between the measured value including the rotation angle of the motor obtained from the output of the resolver and the estimated value of the rotation angle specified in the past control cycle by a gain for each control cycle. , Equipped with a compensator that specifies the estimated value of the rotation angle in the current control cycle so that the error becomes small,
A variable gain control is adopted in which the gain to be multiplied when the error is larger than the first error threshold is larger than the gain to be multiplied when the error is smaller than the first error threshold.
When the controller controls the motor according to the rectangular wave control law and the error exceeds a second error threshold smaller than the first error threshold, the controller controls the motor control law according to A motor control device that switches from a rectangular wave control law to the PWM control law.

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