JP3127033B2 - Electric car - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric vehicle, and more particularly to a torque control device for an electric vehicle driven by a DC brushless motor.

[0002]

2. Description of the Related Art In an electric vehicle, a battery is used as a DC power source, and the driving force of a DC motor or an AC motor is transmitted directly to wheels or through a gear, and the desired driving force is controlled by controlling the speed or torque of the motor. I'm trying to get

For example, an electric vehicle shown in FIG. 7, four is the wheel ₁ 1 to 1 4-wheel direct drive type to directly connect the respective motor 21 _{to 24} in _4, each motor 21 _{to 24} inverter 3 ₁ to 3 ₄ AC power supply that is a current or voltage control from the output control of the inverters 3 ₁ to 3 ₄ gives a torque command or speed command from the potentiometer 5 interlocked with the depression angle of the accelerator pedal 4. 6 is each inverter 3 _{1 to} 3 ₄
Is a battery that supplies DC power necessary for the battery.

A DC brushless motor that obtains a field magnetic flux by using a permanent magnet uses a field of a permanent magnet as a rotor, detects the position of a magnetic pole of the rotor, and outputs a current (current) of a stator based on the position signal. The current is controlled so that the armature current and the magnetic flux are always orthogonal. That is, by controlling the armature current of the motor and the motor induced voltage to have the same phase, characteristics similar to those of the DC machine are realized.

[0005] controller in the case of such a DC brushless motor as a drive source of an electric vehicle is the configuration for controlling the output current of the inverter 3 ₁ to 3 ₄ to obtain a torque command from the potentiometer 5.

This control device has, for example, the configuration shown in FIG. The DC power from the DC power supply 11 is converted into a power output of a PWM waveform controlled by the inverter main circuit 12 and supplied as an armature current of the DC brushless motor 13. The rotor position of the motor 13 is detected by the absolute encoder 14 as a phase signal θ. Command I _1ref is the multiplier of the multiplier 15 _1, 15 _2, the multiplicand of the multiplier 15 _1, 15 ₂ are sinusoidal signals 120 ° phase-shifted from one another from the sine wave generator 16. The sine wave phase is controlled according to the encoder 14 and the phase signal θ.

The outputs of the multipliers 15 ₁ and 15 ₂ are connected to the motor 13.
Sine-wave current commands I _u , I _w of the three-phase input to the motor are extracted, and these current commands I _u , I _w use the motor currents I _u ′, I _w ′ as feedback signals. The proportional and integral calculations are performed by the current control amplifiers 17 ₁ and 17 ₂ , and u
Voltage command V _u phase and w-phase, it is taken out as V _w.

The voltage commands V _u and V _w are added by an adder 18 so that the output of the adder 19 provides a v-phase voltage command V
_v is generated. These voltage commands V _u , V _w , V _v are PWM
It is the comparison input of the comparator 19 _1, 19 _2, 19 ₃ as generating circuit, the comparator 19 ₁ to 1 by the triangular wave signal from the carrier generator 20 is provided to compare the reference
9 is PWM waveform of sine wave approximation retrieved _third output, these PWM waveform is in phase gate signals of the inverter main circuit 12, the drive signal of each phase switching element is amplified by the gate circuit 21 inverter main circuit 12 To be.

[0009]

In a conventional electric vehicle driven by a DC brushless motor, a torque command value is output from a potentiometer 5 which increases in proportion to the depression angle of an accelerator pedal 4.

On the other hand, the DC brushless motor has a higher induced voltage as its rotation speed increases. For this reason,
Even if the same torque command is given, a normal torque current cannot be supplied depending on the motor rotation speed (travel speed of the electric vehicle) at that time.

That is, since the torque command value given from the potentiometer is associated with the maximum torque of the motor in a low speed range, it is impossible to secure a power supply voltage required to supply a current corresponding to the torque command in a high speed range. In the current control system for feedback control of the current, the amplifier 1
The outputs of 7 ₁ and 17 ₂ are saturated. In the PWM control of the sine wave approximation, the saturated output becomes close to a trapezoidal wave and the three-phase current becomes unbalanced, so that a normal torque current cannot be supplied.

To solve the above-mentioned problem, it is conceivable to limit the torque command value according to the motor rotation speed. However, a mere limitation according to the rotation speed is inappropriate.

For example, when the torque command value is excessively limited, the torque output does not change due to the output torque limitation even when the accelerator pedal is depressed, so that the acceleration / deceleration of the electric vehicle is uncomfortable and the acceleration performance and output performance are deteriorated. . Conversely, the shortage limitation of the torque command value causes the above-described problem.

Further, the maximum output torque is greatly affected by the voltage drop caused by the open voltage fluctuation and the internal resistance change due to the depth of discharge of the battery as a DC power supply, and the mere limitation of the torque command value is inappropriate.

An object of the present invention is to provide an electric vehicle capable of eliminating an excess and deficiency of a torque command value and obtaining a torque command value harmonized with the depression angle of an accelerator pedal.

[0016]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a DC brushless motor serving as a driving source for a wheel, a step angle of an accelerator pedal being a torque command _TACC, and a current corresponding to the torque command. an inverter for controlling the armature current of the motor according to the command, an electric vehicle that includes a battery composed of a DC power supply of the inverter, the torque command limit value from the open voltage V _o of the speed n and the battery of the motor T _m is given by

[0017]

(Equation 2)

[0018] However, K _T: Torque command - current command conversion coefficient K _1, K _2: inverter loss factor K _N: induced voltage constant _{R a ': (1 + K} f) R a R a: equivalent motor winding resistance K _f : Stray loss coefficient R _i : battery internal resistance K _o : motor no-load loss coefficient
Characterized in that a limiter circuit for limiting the _ACC with the limit value T _m.

[0019]

The maximum output characteristics when the armature current of the DC brushless motor is controlled by an inverter and the DC power supply of the inverter is a battery will be described with reference to FIG.

FIG. 1 shows one phase of the motor drive system. The constants of the battery, the inverter and the DC brushless motor are as follows.

[0021] V _o: the battery open voltage R _i: battery internal resistance E _D, I _D: DC input voltage of the inverter, the current V _a, I _a: an AC output voltage of the inverter, the current E _o: motor induced voltage (phase voltage ) R _a : Motor equivalent winding resistance (for one phase) In the configuration of FIG. 1, the inverter loss W _INV is a steady loss and a switching loss. If this is expressed as _a function of the AC output current _Ia , Becomes

W _INV = K _{1 Ia} ² + K _{2 Ia} (1) where K ₁ and K _{2 are} inverter loss coefficients. Next, the total loss W _{IM of the} motor is the primary copper loss W _CU and the no-load loss. W _o and the following equation stray load loss _{W a W CU = 3R a I} a 2 ... (2-1) W o = K o · n 1 · 6 ... (2-2) W a = K f W CU ... ( if _{2-3), W IM = W CU} + W o + W a = (1 + K f) R a I a 2 + K o · n 1 · 6 = R a 'I a 2 + K o n 1 · 6 ... (3 ).

Next, the DC input side of the inverter from the relation of FIG. _{1, V o -R i I D} = E D ... (4) In addition, between E _D and V _a

[0024]

(Equation 3)

[0025] However, mu: There is an inverter control rate relationship, further _{E D I D = 3V a I} a ... (6) the relationship is assumed to be satisfied, from (5) - (6)

[0026]

(Equation 4)

Holds.

Further, the relationship between the input and output and motor loss of the _{inverter, E D I D = W INV} + W IM + 3I a E o = K 1 I a 2 + K 2 I a + R a 'I a 2 + 3I a E o = (K ₁ + R _a ′) I _a ² + (K ₂ + 3E _o ) I _a (8) is obtained. However, the no-load loss W _{o in} equation (3) (= K _o · n
^1.6 ) is neglected, and this will be deducted from the final torque as no-load torque.

By substituting equations (4) and (7) into equation (8),

[0030]

(Equation 5)

[0031] When this is arranged,

[0032]

(Equation 6)

## EQU1 ##

Therefore, in the equation (10), the inverter control rate μ is set to the maximum value of 1, and E _o = K _N · n (11) T = K _T · I _a (12) where T: motor , The maximum output torque T for the rotation speed n
_m is given by the following equation.

[0035]

(Equation 7)

According to the above equation (13), the battery parameters (V _o , R _i ) and the inverter parameters (K ₁ ,
Since K ₂ ) and the parameters of the motor (K _T , K _N , R _a ′) are known values, the maximum outputtable torque T _m for each rotation speed n can be obtained.

More precisely, the no-load loss W _o (= K _o · n
By subtracting ^1-6) content of the torque from (13)

[0038]

(Equation 8)

As a result, the maximum torque _Tm is obtained.

[0040] The maximum torque the T _m is as illustrated in FIG. 2, region A indicates that it is limited by the maximum allowable current of the inverter, limited by the maximum torque T _m of region B is determined depending on the rotational speed n Value.

[0041] Since up to this, in the present invention limits the torque command value to the maximum torque T _m which can be output from the open-circuit voltage V _o of the speed n and the battery of the motor, so that it is torque control causing no excess and deficiency To

[0042]

FIG. 3 is a diagram showing the construction of an apparatus according to an embodiment of the present invention, showing a set of torque control devices. The inverter 21 has, for example, the control device configuration of FIG. 8 and includes a current control system that supplies an AC output corresponding to the current command value I _1ref to the DC brushless motor 13. The torque command T _ACC to be output from the potentiometer 5 is limited by the limiter circuit 22 and is converted into a torque signal T. The torque signal T is converted by the torque-current conversion calculator 23 into a torque-current conversion coefficient 1.
/ K _T and the current command I _1ref to the inverter 21
To be.

Here, the limiter value T of the limiter circuit 22
_m is given by the limiter value calculator 24. Limiter value T _m from the open voltage V _o of the rotational speed n and the battery 11 in this operation DC brushless motor 13 of the aforementioned (14)
It is obtained from the equation or the equation (13).

As described above, the torque command value T _ACC is converted into the maximum torque T _ACC by the limiter circuit 22 and the limiter value calculator 24.
By limiting to _m , the torque is limited to within an optimal torque command value according to the number of revolutions, and smooth driving and stable driving can be performed.

The limiter value calculator 24 limits the maximum torque _Tm to the torque command value _Tmax when the accelerator stroke is 100% in a region A (see FIG. 2) limited by the maximum allowable current of the inverter. This calculation is realized by a conditional expression of IF _Tm > _Tmax THEN _Tm = _Tmax .

FIG. 4 is a diagram showing the configuration of an apparatus according to another embodiment of the present invention. 3 is different from FIG. 3 in that the limiter circuit 2
2 in that a full scale adjustment unit 25 is provided.

The full-scale adjusting unit 25 obtains a torque command T from the following equation for the torque command value _TACC .

T = T _ACC × (T _m / T _max ) (15) The operation and effect of this embodiment will be described. First, the torque command value T _ACC is restricted to a maximum torque T _m by limiter value calculating unit 24 in the embodiment described above. The limiting characteristic at this time is, as shown in FIG. 2, the maximum torque T _m according to the motor speed n.
Is determined.

In this limiting characteristic, in the area B, the accelerator pedal is depressed to the maximum, but the torque is limited to the maximum torque _Tm , so that there is an "play area" in which the torque command T does not change even when the accelerator pedal angle is changed.

[0050] For example, it is limited to a maximum torque T _m90 at the time the motor rotational speed n _90, in a range of play region C is limited by the maximum torque T _m90 to the accelerator depression angle changes. For this reason, in the play area C, there is no acceleration or deceleration of the electric vehicle even when the accelerator is depressed or returned, which gives the driver an uncomfortable feeling. In particular, in the vicinity of 100% of the motor rotation speed, the command value T becomes the maximum torque _Tm and is limited to the maximum torque Tm even if the accelerator is slightly depressed.

In this embodiment, the torque command for the full stroke of the accelerator is adjusted by the full-scale adjusting unit 25 in accordance with the motor speed in order to eliminate the uncomfortable feeling of stepping on the accelerator due to the play area C.

For example, at the motor rotation speed n ₉₀ , the maximum torque T _m is given as T _m90 , and the torque command value T _ACC is proportionally distributed according to the ratio T _m90 / T _{max to} the torque command value T _max at the time of the accelerator full stroke. , And the torque command T is T = T _ACC × (T _m90 / T _max ).

At this time, the limiting characteristic of the full scale adjusting unit 25 is in a range surrounded by a line between the maximum torque _Tm and the torque _{Tm90 in} FIG. 2, and the torque command value _Tmax at the maximum accelerator pedal depression angle is _Tm90. become. Therefore, the output torque changes in accordance with the change in the accelerator pedal depression angle, and acceleration / deceleration of the electric vehicle that matches the accelerator pedal depression amount can be obtained.

FIG. 5 is a block diagram of the apparatus showing another embodiment of the present invention. 4 differs from FIG. 4 in that a battery parameter estimating unit 26 is provided.

[0055] battery parameter estimating unit 26, a battery parameter V _o required for the operation of the limiter value calculation unit 24, estimates the R _i, subjecting the estimated value in the calculation of the maximum torque T _m.

[0056] Battery parameters V _o, R _i is the maximum torque T as or part detection value is known in the above-described embodiment
_{Although m} is obtained, the characteristic varies with the depth of discharge of the battery as shown in FIG. 6, and the characteristic differs depending on the type of the battery.

Therefore, in this embodiment, the torque is more appropriately limited by estimating the battery parameter by the battery parameter estimator 26.

The estimation by the battery parameter estimating unit 26 is performed by any of the following methods.

(1) A method of obtaining the depth of discharge of a battery from the amount of discharge current and obtaining parameters from the depth of discharge and battery characteristics.

(2) A method for obtaining parameters from the input voltage E _D and input current I _D of the inverter when the motor control is stopped.

In the above method (1), first, the inverter input current _ID is detected, and the discharge current amount AH (ampere hour) is obtained by this time integration operation.

[0062]

(Equation 9)

The depth of discharge DOD is obtained from the charge current amount AH _o when the battery is fully charged and the discharge current amount AH by the following equation.

[0064]

(Equation 10)

Parameters V _o and R _i are estimated online from the depth of discharge DOD and the previously measured open circuit voltage V _o characteristics and internal resistance R _i characteristics of the battery. The battery characteristics can be written as table data in a ROM or the like.

Next, the method (2) will be described. Open-circuit voltage V _o, since the output voltage of the no-load state of the battery,
It can be obtained by voltage detection when the motor control is stopped, such as when the electric vehicle stops or during coasting operation.

As a result, the input voltage E _D of the inverter,
The current _ID is sampled at appropriate time intervals, and the current _ID =
It detects the voltage E _D at the time of the 0 and the open-circuit voltage V _o. next,
Current I _D> detection value of the voltage E _D and the current I _D at the time of motor drive becomes 0 and the internal resistance R _i from the above equation (4) _{R i = (E D -V o} ) / I D ... (18 ). These calculations are performed for each sampling period, and an estimated value is obtained online.

In the two estimation methods described above, the method (1) may cause a cumulative error due to performing a long-time cumulative calculation. On the other hand, in the method (2), when the motor control is continued such as during continuous running, the current _ID =
There may be a measurement occasion voltage E _D not obtained over a long period of time at 0. From such a fact, the estimation error can be reduced by estimating the battery parameters V _o and R _i using both the methods (1) and (2).

[0069]

As evident from the foregoing description, according to the present invention, the torque command value to the maximum torque T _m of the motor can be outputted from the open-circuit voltage V _o of the speed n and the battery of the DC brushless motor T
_{Since the ACC} is limited, it is possible to perform appropriate motor control without excessive or insufficient torque control.

Further, by adding full-scale adjustment to the torque limitation, it is possible to eliminate the sense of incongruity in the accelerator pedal depression and the change in the output torque, and it is possible to obtain a more reliable torque limitation by estimating the battery parameters. .

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a motor drive system.

FIG. 2 is a diagram showing an example of a limiting characteristic of the present invention.

FIG. 3 is a configuration diagram of an apparatus according to an embodiment.

FIG. 4 is a device configuration diagram of another embodiment.

FIG. 5 is an apparatus configuration diagram of another embodiment.

FIG. 6 is a characteristic diagram of a battery.

FIG. 7 is a configuration diagram of an electric vehicle.

FIG. 8 is a configuration diagram of a control device of a DC brushless motor.

[Explanation of symbols]

11 ... battery, 13 ... DC brushless motor, 22 ...
Limiter circuit, 23 ... torque-current conversion calculator, 24 ...
Limiter value calculation unit, 25 ... full scale adjustment unit, 26 ...
Battery parameter estimation unit.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadashi Ashikaga 2-1-117 Osaki, Shinagawa-ku, Tokyo, Japan Inside the Meidensha Corporation (72) Inventor Takayuki Mizuno 2-1-117, Osaki, Shinagawa-ku, Tokyo Meidensha Corporation (72) Inventor Yoshinori Nakano 2-1-17-1 Osaki, Shinagawa-ku, Tokyo Inside Meidensha Co., Ltd. (56) References JP-A-1-218376 (JP, A) JP-A-1-120702 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60L 1/00-15/42

Claims (4)

(57) [Claims] A brushless DC motor serving as a drive source for a wheel; an inverter for controlling an armature current of the motor in accordance with a current command corresponding to a torque command TACC with an accelerator pedal depression angle as a torque command _TACC ; in an electric vehicle that includes a battery composed of a DC power source, the rotational speed n and the open circuit voltage following equation ## EQU1 ## the limit value T _m of a said torque command from V _o of the battery of the motor However, K _T: Torque command - current command conversion coefficient K _1, K _2: inverter loss factor K _N: induced voltage constant _{R a ': (1 + K} f) R a R a: equivalent motor winding resistance K _f: stray loss Coefficient R _i : battery internal resistance K _o : motor no-load loss coefficient
Electric vehicle is characterized in that a limiter circuit for limiting the _ACC with the limit value T _m. 2. In place of the limiter circuit, the torque command T _ACC is calculated from the limit value T _m from the limit value calculation unit and the torque command value T _max limited by the maximum allowable current of the inverter, T = T _2. The electric vehicle according to claim 1, further comprising a full-scale adjustment unit for limiting _ACC × ( _Tm / _Tmax ). 3. 請, characterized in that the open-circuit voltage V _o and the internal resistance R _i of the battery with a battery parameter estimating unit for determining the depth of discharge and battery characteristics of the battery
The electric vehicle according to claim 1 . Sought wherein the open-circuit voltage V _o of the battery as the voltage E _D at a stop motor control, battery parameter estimation current I _D and the voltage V _o in the motor control, the E _D obtains the internal resistance R _i 2. The device according to claim 1, further comprising:
Onboard electric car.