JPH09308281A - Motor drive control apparatus in electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively control fluctuation in the number of rotations of motor without use of a rotation sensor which provides lower detection accuracy when the number of rotations is low, in an electric vehicle which adjusts a duty value to be fed to a motor in order to match the actual current of motor to the target current. SOLUTION: Considering that a fluctuation ΔDuty of the duty value Duty outputted to an inverter 6 from a feed back control means 15 is changing proportional to a fluctuation ΔNm of the number of rotations Nm of motor 1, when the motor 1 having a lower accuracy of the motor rotation sensor S3 is rotating at a lower speed, fluctuation of motor rotation Nm is controlled by compensating for a target current ICMD outputted by a target current calculating means 14 depending on fluctuation of duty value ΔDuty. When the motor 1 is rotating at a high speed at which the motor rotation sensor S3 accurately detects the variation, the target current ICMD is compensated directly depending on the fluctuation ΔNm of the number of rotations of motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor for an electric vehicle that converges the actual current to the target current by adjusting the duty value applied to the motor based on the deviation between the actual current of the motor and the target current. The present invention relates to a drive control device.

[0002]

2. Description of the Related Art In a motor used in an electric vehicle, fluctuations in the number of revolutions are unavoidable due to its structural characteristics, and particularly at low speeds, the vibrations due to the variation in the number of revolutions become large, and the vibrations are generated in the drive system. There was a problem that it resonated with the natural frequency of and caused the vehicle body vibration. Therefore, U.S. Pat. No. 5,349,278 proposes a technique for detecting the fluctuation of the motor rotation speed and controlling the motor current based on the fluctuation to suppress the occurrence of the vibration.

[0003]

By the way, the electromagnetic sensor generally used for detecting the number of rotations of the motor is excellent in detection accuracy at high speed rotation, but the detection accuracy at low speed rotation is significantly lowered. There's a problem. Therefore, even if the motor current is controlled based on the motor rotation speed detected using such a motor rotation speed sensor, the fluctuation of the motor rotation speed can be effectively suppressed because the accuracy of the detected value itself is low. This is not possible, and there is a problem that it is difficult to prevent the occurrence of vibration, especially at low speed rotation.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to effectively suppress fluctuations in motor rotation speed without using a motor rotation speed sensor whose detection accuracy decreases at low speed rotation. .

[0005]

In order to achieve the above object, a motor drive control device in an electric vehicle according to a first aspect of the present invention comprises a target current calculation means for calculating a target current of a motor and an actual current of the motor. An actual current calculation means for calculating
A motor current feedback control unit that adjusts a duty value for energizing a motor to match the actual current with the target current, a duty value variation amount calculation unit that calculates a variation amount of the duty value, and a variation of the duty value. Target current correction means for correcting the target current based on the amount is provided.

According to a second aspect of the present invention, there is provided a motor drive control device for an electric vehicle, wherein a target current calculating means for calculating a target current of the motor, an actual current calculating means for calculating an actual current of the motor, and the actual current Motor current feedback control means for adjusting the duty value to be applied to the motor so as to match the target current, average duty value calculation means for calculating the average value of the duty value, deviation of the duty value and the average duty value And a target current correction means for correcting the target current based on the above.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

1 to 5 show a first embodiment of the present invention, FIG. 1 is a diagram showing the overall construction of an electric vehicle, FIG. 2 is a block diagram of a control system, and FIG. 3 is a flow chart for explaining the operation. FIG. 4 is a diagram showing an equivalent circuit of the motor drive circuit, and FIG. 5 is a graph for explaining a gain setting method.

As shown in FIG. 1, a four-wheel electric vehicle V is
A pair of left and right front wheels Wf, W as driving wheels to which the torque of the three-phase AC motor 1 is transmitted via the transmission 2.
f and a pair of left and right rear wheels Wr, Wr as driven wheels. A main battery 3 of, for example, 288 volts mounted on the rear portion of the electric vehicle V is connected to the motor 1 via a contactor 4, a joint box 5, a contactor 4 and an inverter 6 that constitutes a power drive unit.
For example, a 12-volt sub battery 7 and a main switch 8
And electronic control unit 1 connected via fuse 9
0 is connected to the inverter 6 to control the drive torque and regenerative torque of the motor 1. In order to charge the sub battery 7 with the power of the main battery 3, the battery charger 1
1 and a DC / DC converter 12 are provided.

As shown in FIG. 2, an AC circuit connecting the motor 1 and the inverter 6 is provided with a current sensor S ₁ ... And an actual current calculating means 1 to which an output signal thereof is inputted.
3 calculates the actual current I _ACT of the motor 1. On the other hand, the accelerator opening theta _AP detected by the accelerator opening sensor S _2, and the motor rotation speed Nm detected by the motor rotational speed sensor S _3, the shift position P and the target current calculating section detected by the shift position sensor S ₄ 14 is input. The target current calculation means 14 calculates the torque command value that the driver is trying to generate in the motor 1 based on the accelerator opening θ _AP , the motor rotation speed Nm, and the position P, for example, by map search, and at the same time, calculates the torque command value and A target current I _CMD to be supplied to the motor 1 or to be extracted from the motor 1 by regeneration is calculated based on the motor rotation speed Nm.

The target current I _CMD calculated by the target current calculation means 14 and the actual current I _ACT devised by the actual current calculation means 13
Are input to the motor current feedback control means 15, and the target current I _CMD and the actual current I _ACT calculated there are
The motor current feedback control means 15 duty-controls the inverter 6 in order to converge the deviation of 0 to zero.
That is, the inverter 6 is provided with a plurality of switching elements, and by inputting a switching signal consisting of a duty signal from the motor current feedback control means 15 to each switching element, the DC power of the main battery 3 is three times when the motor 1 is driven. When the motor 1 is driven (regenerative), the three-phase AC power generated by the motor 1 is converted into DC power and supplied to the main battery 3.

The duty value Duty input from the motor current feedback control means 15 to the inverter 6 is also input to the duty value variation amount calculation means 16, where the variation amount ΔDuty of the duty value Duty is calculated. Further, the motor rotation speed fluctuation amount calculation means 17 to which the motor rotation speed Nm is input
Calculates the fluctuation amount ΔNm of the motor rotation speed Nm. Variation amount ΔDuty of the duty value Duty and motor rotation speed Nm
The variation amount ΔNm of is input to the target current correction means 18.
The target current correction unit 18 corrects the target current I _CMD output by the target current calculation unit 14 based on the duty value fluctuation amount ΔDuty to reduce the rotation fluctuation of the motor 1 when the motor rotation speed Nm is low, and the motor rotation speed is reduced. When the number Nm is high, the target current I _CMD output by the target current calculation means 14 is corrected based on the motor rotation speed fluctuation amount ΔNm.

In the electronic control unit 10, the actual current calculation means 13 and the motor current feedback control means 15 are composed of hardware consisting of electric circuits,
The other means is composed of software having the functions shown in the flowchart of FIG.

Next, the operation of the present invention will be further described based on the flowchart of FIG.

First, in step S1, the target current calculation means 1
4, the accelerator opening θ _AP , the motor speed Nm and the shift position P are read, and the target current I _CMD is read in step S2.
Is calculated. Next, in step S3, the duty value Duty calculation unit 16 reads the duty value Duty, and in step S3
In step 4, the duty value variation amount ΔDuty is calculated. Next, in step S5, the motor rotation speed fluctuation amount calculation unit 17 is loaded with the motor rotation speed Nm, and in step S6, the motor rotation speed fluctuation amount ΔNm is calculated.

In the subsequent step S7, when the motor rotation speed Nm is less than the predetermined value and the detection accuracy of the motor rotation speed sensor S ₃ is low, the target current correction means 18 outputs the output of the target current calculation means 14 in step S8. Target current I
_CMD is corrected based on the duty value variation amount ΔDuty.
That is, the correction term is set by K ₁ * ΔDuty which is the product of the gain K ₁ and the duty value variation amount ΔDuty.
₁ * ΔDuty is subtracted from the target current I _CMD output by the target current calculation means 14.

I _CMD ← I _CMD −K ₁ * ΔDuty (1) Then, in step S 9, the corrected target current I _CMD is output to the motor current feedback control unit 15 to output the motor current feedback control unit. Reference numeral 15 feedback-controls the motor 1 so that the actual current I _ACT of the motor 1 matches the target current I _CMD .

By the way, the drive circuit of the motor 1 can be replaced with an equivalent circuit shown in FIG. Here, the current I flowing through the motor 1 is based on the battery voltage V, the resistance R of the motor 1, the back electromotive force E of the motor 1, and the duty value Duty. I = (V * Duty−E) / R (2 ) Is represented by.

In equation (2), the current feedback control is used.
Since the current I is kept constant by the control,
Assuming that the pressure V and the resistance R of the motor 1 are constant,
The duty value Duty and the counter electromotive force E are proportional.
You. The counter electromotive force E is proportional to the motor speed Nm.
Therefore, the duty value Duty is proportional to the motor rotation speed Nm.
In other words, if the duty value fluctuation amount ΔDuty is monitored,
Is to monitor the motor rotation speed fluctuation amount ΔNm.
Become. Thus, the target voltage output by the target current calculation means 14 is output.
Style I_CMDGain K₁And duty value variation ΔDuty
Correction term K which is the product ₁* Target voltage after correction corrected with ΔDuty
Style I_CMDFeedback control of the motor 1 based on
As a result, the detection accuracy is significantly improved when the motor 1 rotates at low speed.
Decreasing motor speed sensor S_ThreeDo not use the output of
Effectively suppress fluctuations in the rotation speed of the motor 1 and generate vibrations.
It is possible to prevent life, and especially the motor speed Nm is low.
Effectively prevent the occurrence of vibration when the vehicle starts
Can be.

In step S7, the motor rotation speed N
When m is equal to or greater than a predetermined value, that is, when the detection accuracy of the motor rotation speed sensor S ₃ is sufficiently high, in step S10, the motor rotation speed fluctuation amount Δ calculated in step S6 is calculated.
The target current I _CMD output from the target current calculation means 14 is corrected by the correction term K ₂ * ΔNm obtained by multiplying Nm by the gain K ₂ .

I _CMD ← I _CMD −K ₂ * ΔNm (3) In this case, the detection accuracy of the motor rotation speed sensor S ₃ is sufficiently high, and the motor rotation speed fluctuation amount ΔNm is directly used. The rotation speed fluctuation of the motor 1 can be suppressed with high accuracy.

By the way, when the motor rotation speed Nm is increased to accelerate or decelerate the vehicle, the motor rotation speed fluctuation amount ΔNm is generated along with the acceleration or deceleration. Therefore, the motor rotation speed fluctuation amount ΔNm is generated by the motor 1. The control system may erroneously recognize that it is due to a normal rotation fluctuation, and may perform control for suppressing fluctuations in the motor rotation speed Nm (that is, acceleration and deceleration). In particular, when the gain K ₂ used for correction when the motor speed Nm is high is set to a large value, the increase or decrease of the motor speed Nm is strongly suppressed and the acceleration performance of the vehicle or the deceleration performance of the vehicle during regenerative braking is increased. May be hindered.

Therefore, paying attention to the fact that the motor rotation speed fluctuation amount ΔNm during acceleration and deceleration of the vehicle is smaller than the normal motor rotation speed fluctuation amount ΔNm, and as shown in FIG. In a small range in which the number fluctuation amount ΔNm occurs in the normal acceleration / deceleration of the vehicle, the gain K ₂ is set to zero to prevent the acceleration performance and the deceleration performance of the vehicle from deteriorating and the motor rotation speed fluctuation amount. In a region where ΔNm is too large to occur in normal acceleration / deceleration of the vehicle, the gain K ₂ is set to a predetermined value to prevent the occurrence of vibration.

In FIG. 5 (A), the region in which the gain K ₂ is set to zero is narrow on the acceleration side and wide on the deceleration side. This is because the fluctuation amount ΔNm may occur. Further, the gain K ₁ used for correction when the motor rotation speed Nm is low is held constant because rapid acceleration or deceleration does not substantially occur in the region where the motor rotation speed Nm is low. is there.

The gain K is shown in FIG._TwoTo set
Other approaches are shown. That is, when accelerating and decelerating the vehicle
The fluctuation frequency of the motor speed Nm in the normal motor 1
It is extremely small compared to the frequency of the rotational vibration of
Gain K in the small wave number range _TwoTo zero for the vehicle
Ensure the acceleration and deceleration performance,
Gain K in the range_TwoIs set to a predetermined value and the rotation fluctuation of the motor 1
Can be prevented.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. Incidentally, in FIG. 6 and FIG.
The components and steps corresponding to the components and the steps of the flowcharts described in the embodiments have the same reference numerals and step numbers.

In the second embodiment, the target current I _CMD is set to the average duty value Duty when the motor speed Nm is less than a predetermined value.
Corrected based on the deviation Duty _AV -Duty the _AV and duty value Duty, and if the motor rotation speed Nm is equal to or greater than a predetermined value,
The target current I _CMD is corrected based on the deviation Nm _AV −Nm between the average motor rotation speed Nm _AV and the motor rotation speed Nm.

That is, as shown in FIG. 6, in the second embodiment,
Instead of the duty value fluctuation amount calculation means 16 of the first embodiment
The average duty value calculation means 16 ',
Instead of the motor rotation speed fluctuation amount calculation means 17 of the embodiment,
A uniform motor rotation speed calculation means 17 'is provided. Average duet
Value calculation means 16 'is set at a predetermined time of the duty value Duty.
Average duty value Duty which is the average value over_AVAnd calculate
Average duty value of Duty _AVTo the target current correction means 18
Power. Further, the average motor rotation speed calculation means 17 'is
Average motor that is the average value of the rotational speed Nm over a predetermined time
Rotation speed Nm_AVAnd the average motor speed Nm_AVTo
Output to the target current correction means 18.

Thus, in the flow chart of FIG.
If the motor rotation speed Nm is less than the predetermined value in step S7, in step S8 ', the target is determined by the correction term obtained by multiplying the deviation between the average duty value Duty _AV and the duty value Duty obtained in step S4' by the gain K _1. Correct the current I _CMD .

I _CMD ← I _CMD −K ₁ * (Duty _AV −Duty) (4) If the motor rotation speed Nm is equal to or higher than a predetermined value in step S 7, it is determined in step S 6 ′ in step S 10 ′. The target current I is calculated by the correction term obtained by multiplying the deviation between the average motor speed Nm _AV and the motor speed Nm by the gain K _2.
Correct _CMD .

I _CMD ← I _CMD −K ₂ * (Nm _AV −Nm) (5) Therefore, the second embodiment differs from the first embodiment in the method of calculating the correction term of the target current I _CMD. However, it is possible to achieve the same effects as the effects described in the first embodiment.

Although the embodiments of the present invention have been described in detail above, the present invention can be modified in various ways without departing from the scope of the invention.

[0033]

As described above, according to the present invention, the duty value applied to the motor is adjusted so that the actual current of the motor matches the target current. Since the target current is corrected based on the deviation between the duty value and the average duty value, it is possible to suppress the fluctuation of the motor rotation speed and prevent the occurrence of vibration without directly detecting the motor rotation speed. As a result, even when the motor rotates at a low speed in which the detection accuracy of the motor rotation speed sensor decreases, it is possible to effectively suppress fluctuations in the motor rotation speed.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an electric vehicle.

FIG. 2 is a block diagram of a control system.

FIG. 3 is a flowchart explaining the operation.

FIG. 4 is a diagram showing an equivalent circuit of a motor drive circuit.

FIG. 5 is a graph illustrating a gain setting method.

FIG. 6 is a block diagram of a control system according to a second embodiment of the present invention.

FIG. 7 is a flowchart according to the second embodiment of the present invention.

[Explanation of symbols]

1 Motor 13 Actual Current Calculation Means 14 Target Current Calculation Means 15 Motor Current Feedback Control Means 16 Duty Value Fluctuation Calculation Means 16 'Average Duty Value Calculation Means 18 Target Current Correction Means Duty Duty Values Duty _AV Average Duty Value ΔDuty Duty Value Fluctuations I _ACT Actual current I _CMD Target current

Claims (2)

[Claims] 1. A target current calculation means (14) for calculating a target current (I _CMD ) of a motor (1), and an actual current calculation means (13) for calculating an actual current (I _ACT ) of the motor (1). , A duty value (Du) for energizing the motor (1) so that the actual current (I _ACT ) matches the target current (I _CMD ).
motor current feedback control means (1)
5), a duty value fluctuation amount calculation means (16) for calculating a fluctuation amount (ΔDuty) of the duty value (Duty), and the target current (I) based on the fluctuation amount (ΔDuty) of the duty value (Duty). _{CM D)} the motor drive control device in the electric vehicle, characterized in that it includes a target current correcting means (18) for correcting the. 2. A target current calculation means (14) for calculating a target current (I _CMD ) of the motor (1), and an actual current calculation means (13) for calculating an actual current (I _ACT ) of the motor (1). , A duty value (Du) for energizing the motor (1) so that the actual current (I _ACT ) matches the target current (I _CMD ).
motor current feedback control means (1)
5), an average duty value calculation means (16 ') for calculating an average value (Duty _AV ) of the duty values (Duty), and a deviation between the duty value (Duty) and the average duty value (Duty _AV ) And a target current correction means (18) for correcting the target current (I _CMD ) according to the present invention.