JPH05236607A - Electric automobile - Google Patents

Abstract

PURPOSE:To provide an electric automobile employing a DC brushless motor as a drive source and the armature current of the motor is controlled through an inverter according to a torque command wherein excess and deficiency of torque command value are eliminated and a torque command harmonized with the step angle of accelerator pedal is obtained. CONSTITUTION:Maximum torque Tm of motor is determined at a limiter value operating section 24 based on the number of revolutions of the motor open voltage of battery, and parameters of the motor and the battery, and the like, and a torque command TACC is limited by the maximum torque Tm at a limiter circuit 22. Excess or deficiency of torque command for an inverter 21 is eliminated by limiting the torque command TACC corresponding to the step angle of accelerator pedal by means of the maximum torque Tm.

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 using a DC brushless motor as a drive source.

[0002]

2. Description of the Related Art An electric vehicle uses a battery as a DC power source, transmits the driving force of a DC motor or an AC motor directly to wheels or through a gear, and controls the motor speed or torque to achieve a desired driving force. 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
This is a battery that supplies the necessary DC power to the battery.

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

A control device using such a DC brushless motor as a drive source of an electric vehicle is configured to obtain a torque command from the potentiometer 5 and control the output currents of the inverters 3 _{1 to} 3 ₄ .

This control device is constructed, for example, as shown in FIG. The DC power from the DC power supply 11 is converted into a PWM waveform power output controlled by the inverter main circuit 12, and is 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. The command I _1ref is set to a multiplier of the multipliers 15 ₁ and 15 ₂ , and the multiplicands of the multipliers 15 ₁ and 15 ₂ are sine wave signals from the sine wave generator 16 that are phase-shifted by 120 degrees. This sine wave phase is controlled according to the encoder 14 and the phase signal θ.

The output of the multipliers 15 ₁ and 15 ₂ is the motor 13
The u-phase and w-phase sine wave current commands I _u and I _w of the three-phase input to the motor are taken out, and these current commands I _u and I _w use the motor currents I _u ′ and I _w ′ as feedback signals. Proportional / integral calculation is performed by the current control amplifiers 17 ₁ and 17 ₂ , and u
It is taken out as the voltage commands V _u and V _w for the phase w and the phase _w .

The voltage commands V _u and V _w are added by the adder 18 so that the output of the adder 19 receives the v-phase voltage command V _u .
_v is generated. These voltage commands V _u , V _w , and V _v are PWM
The triangular wave signal from the carrier wave generator 20 is supplied to the comparators 19 ₁ , 19 ₂ and 19 ₃ as a generating circuit for comparison, and the comparators 19 ₁ to 19 ₁
A PWM waveform of a sine wave approximation is taken out from the output of 9 ₃ , and these PWM waveforms are converted into gate signals for each phase of the inverter main circuit 12 and amplified by the gate circuit 21 to drive signals for each phase switch element of the inverter main circuit 12. To be

[0009]

In a conventional electric vehicle using a DC brushless motor as a drive source, the torque command value becomes the output of the potentiometer 5 which rises in proportion to the depression angle of the accelerator pedal 4.

On the other hand, the DC brushless motor has a higher induced voltage as the rotational speed thereof 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 (driving 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 the low speed range, it becomes impossible to secure the power supply voltage necessary to supply the current according to the torque command in the high speed range. , Amplifier 1 in the current control system for feedback control of current
The outputs of 7 ₁ and 17 ₂ are saturated, and this saturated output becomes close to a trapezoidal wave in the PWM control of the sine wave approximation, and the three-phase current becomes imbalanced, so that normal torque current supply cannot be performed.

In order to solve the above-mentioned problem, it is conceivable to limit the torque command value according to the number of rotations of the motor, but mere limitation according to the number of rotations is an inappropriate limit.

For example, if the torque command value is excessively limited, the torque output will not change even when the accelerator pedal is changed in the depression angle, and the torque output will not change. This will make the electric vehicle feel uncomfortable in acceleration and deceleration, and deteriorate the acceleration performance and output performance. .. On the contrary, limiting the shortage of the torque command value causes the above-mentioned problem.

Further, the maximum output torque is greatly affected by the voltage drop caused by the open circuit voltage fluctuation and the internal resistance change due to the depth of discharge of the battery as the DC power supply, and it becomes unsuitable if the torque command value is simply limited.

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

[0016]

In order to solve the above problems, the present invention uses a DC brushless motor as a drive source for wheels and a pedaling angle of an accelerator pedal as a torque command T _ACC and a current corresponding to the torque command. In an electric vehicle including an inverter that controls an armature current of the motor according to a command and a battery that serves as a DC power source of the inverter, a limit value of the torque command based on the rotation speed n of the motor and the open circuit voltage V _{o of the} battery. T _m is

[0017]

[Equation 2]

However, K _T : torque command-current command conversion coefficient K ₁ , K ₂ : inverter loss coefficient K _N : induced voltage constant R _a ′: (1 + K _f ) R _a R _a : motor equivalent winding resistance K _f : Stray loss coefficient R _i : internal battery resistance K _o : motor no-load loss coefficient
A limiter circuit for limiting _ACC with the limit value T _m is provided.

[0019]

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

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

V _o : Battery open voltage R _i : Battery internal resistance E _D , I _D : Inverter DC input voltage, current V _a , I _a : Inverter AC output voltage, 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 consists of a steady loss and a switching loss. If this is expressed as _a function of the AC output current I _a , Becomes

W _INV = K ₁ I _a ² + K ₂ I _a (1) where K ₁ and K ₂ : Inverter loss coefficient Next, the total loss W _{IM of the} motor is the primary copper loss W _CU and no load loss. W _o and stray load loss W _a are expressed by the following formula W _CU = 3R _a I _a ² (2-1) W _o = K _o · n ^{1 6} (2-2) W _a = K _f W _CU ( 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 ) Becomes.

Next, on the DC input side of the inverter, from the relationship shown in FIG. 1, V _o −R _{i ID} = E _D (4) Further, between E _D and V _a

[0024]

[Equation 3]

However, assuming that μ: Inverter control ratio and E _{D ID} = 3V _a I _a (6) are satisfied, from equations (4) to (6)

[0026]

[Equation 4]

Is satisfied.

From the relationship between the input / output of the inverter and the motor loss, 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 + 3I _a E _o = ( K ₁ + R _a ′) I _a ² + (K ₂ + 3E _o ) I _a (8) is obtained. However, no-load loss W _o (= K _o · n) in the equation (3)
¹ ) ^{and 6} ) are ignored and this is subtracted from the final torque as no-load torque.

Substituting equations (4) and (7) into equation (8) above

[0030]

[Equation 5]

When this is sorted out,

[0032]

[Equation 6]

It becomes

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 Since it is expressed as torque, the maximum output torque T with respect to the rotation speed n
_m is the following formula.

[0035]

[Equation 7]

From the equation (13), the battery parameters (V _o , R _i ) and the inverter parameters (K ₁ ,
K ₂₎ and the motor parameters _{(K T, K N, R} a ') is from a known value, it is possible to obtain the maximum torque T _m can be output for each rotation speed n.

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

[0038]

[Equation 8]

The maximum torque T _m is obtained by

The maximum torque T _m is as illustrated in FIG. 2, showing that the region A is limited by the maximum allowable current of the inverter, and the region B is limited by the maximum torque T _m determined according to the rotation speed n. It becomes a value.

From the above, according to the present invention, the torque command value is limited to the maximum torque T _m that can be output from the motor rotation speed n and the open circuit voltage V _{o of the} battery, so that torque control can be performed without excess or deficiency. To

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a block diagram of an apparatus showing an embodiment of the present invention and shows 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 according to the current command value I _1ref to the DC brushless motor 13. The torque command T _ACC output from the potentiometer 5 is limited by the limiter circuit 22 to be 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 is _added to 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 calculation unit 24. In this calculation, the limiter value T _m is calculated from the rotational speed n of the DC brushless motor 13 and the open circuit voltage V _{o of the} battery 11 as described in (14).
It is calculated from the equation or the equation (13).

As described above, the torque command value T _ACC is set to the maximum torque T by the limiter circuit 22 and the limiter value calculator 24.
By limiting to _m , the torque is limited to within the optimum torque command value according to the rotation speed, and smooth driving and stable driving are possible.

The limiter value calculation unit 24 limits the maximum torque T _m to the torque command value T _max at 100% accelerator stroke in the region A (see FIG. 2) where the maximum allowable current of the inverter is limited. This calculation is realized by the conditional expression of IF T _m > T _max THEN T _m = T _max .

FIG. 4 is a block diagram of an apparatus showing another embodiment of the present invention. 3 is different from FIG. 3 in that the limiter circuit 2
Instead of 2, the full-scale adjusting unit 25 is provided.

The full-scale adjusting unit 25 obtains the torque command T from the following formula for the torque command value T _ACC .

T = T _ACC × (T _m / T _max ) (15) The function and effect of this embodiment will be described. First, in the above-described embodiment, the limiter value calculator 24 limits the torque command value T _ACC to the maximum torque T _m . The limiting characteristic at this time is, as shown in FIG. 2, the maximum torque T _m depending on the motor speed n.
Is decided.

In this restriction characteristic, in the area B, the maximum torque T _m is limited even if the accelerator is maximally stepped on, and a "play area" occurs in which the torque command T does not change even when the accelerator depression angle is changed.

For example, the motor rotation speed n ₉₀ is limited to the maximum torque T _m90 at that time, and within the range of the play area C, the maximum torque T _m90 is also limited for changing the accelerator depression angle. For this reason, in the play area C, there is no acceleration or deceleration of the electric vehicle even when the accelerator is stepped on or returned, and the driver feels uncomfortable. In particular, when the motor speed is near 100%, the command value T becomes the maximum torque T _m and is limited to this value by simply stepping on the accelerator.

In order to eliminate the uncomfortable feeling of the accelerator depression due to the play area C, the full-scale adjusting unit 25 adjusts the torque command for the full stroke of the accelerator according to the motor rotation speed in this embodiment.

For example, at the motor 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 accelerator full stroke. , The torque command T is T = T _ACC × (T _m90 / T _max ).

At this time, the limiting characteristic by the full-scale adjusting unit 25 is in the range surrounded by the lines of the maximum torque T _m and the torque T _{m90 in} FIG. 2, and the torque command value T _max at the maximum accelerator depression angle is T _m90. become. Therefore, the output torque changes according to the change of the accelerator pedal depression angle, and the acceleration / deceleration of the electric vehicle can be obtained in accordance with the accelerator pedal depression amount.

FIG. 5 is a block diagram of an apparatus showing another embodiment of the present invention. The difference between FIG. 4 and FIG. 4 is that a battery parameter estimation unit 26 is provided.

The battery parameter estimation unit 26 estimates the battery parameters V _o and R _i necessary for the calculation of the limiter value calculation unit 24, and uses this estimated value for the calculation of the maximum torque T _m .

The battery parameters V _o and R _i are known or partially detected as the maximum torque T in the above-mentioned embodiment.
_{Although m} is obtained, it changes as the characteristics shown in FIG. 6 with respect to the depth of discharge of the battery, and the characteristics differ depending on the type of battery and the like.

Therefore, in the present embodiment, the battery parameter is estimated by the battery parameter estimation unit 26 to more appropriately limit the torque.

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

(1) A method in which the depth of discharge of the battery is obtained from the amount of discharge current and the parameters are obtained from the depth of discharge and the battery characteristics.

(2) A method of 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 I _D is detected, and the discharge current amount AH (ampere hour) is obtained by this time integration calculation.

[0062]

[Equation 9]

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

[0064]

[Equation 10]

The parameters V _o and R _i are estimated online based on the depth of discharge DOD, the open circuit voltage V _o characteristic of the battery and the internal resistance R _i characteristic which are measured in advance. The battery characteristics can be written in the ROM or the like as table data.

Next, the method (2) will be described. Since the open circuit voltage V _o is the output voltage of the battery in the no-load state,
This can be obtained by detecting the voltage when the electric vehicle is stopped or when the motor control is stopped, such as during coasting operation.

As a result, the input voltage E _D of the inverter,
The current I _D is sampled at appropriate time intervals, and the current I _D =
The voltage E _D at 0 is detected and set as the open circuit voltage V _o . next,
From the detected values of the voltage E _D and the current I _D at the time of driving the motor where the current I _D > 0 and the above-mentioned formula (4), the internal resistance R _i is expressed as R _i = (E _D −V _o ) / I _D (18) ) Can be obtained as These calculations are performed every sampling period, and the estimated value is obtained online.

In the above two estimation methods, in the method (1), cumulative error may occur due to cumulative calculation for a long time. On the other hand, in the method (2), the current I _D =
The measurement opportunity of the voltage E _D at 0 may not be obtained for a long time. From such a fact, it is possible to reduce the estimation error by estimating the battery parameters V _o and R _i by using the method (1) and the method (2) together.

[0069]

As described above, according to the present invention, the maximum torque T _m that can be output by the motor from the rotational speed n of the DC brushless motor and the open circuit voltage V _{o of the} battery is changed to the torque command value T.
_{Since the ACC} is limited, it is possible to perform appropriate motor control without excess or deficiency in torque control.

Further, by adding full-scale adjustment to the torque limit, it is possible to eliminate a feeling of strangeness in the depression of the accelerator and the change in the output torque, and more reliable torque limit can be obtained by estimating the parameter of the battery. ..

[Brief description of drawings]

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

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

FIG. 3 is a device configuration diagram of an embodiment.

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

FIG. 5 is a device 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 block diagram of a controller 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 calculator, 25 ... Full scale adjuster, 26 ...
Battery parameter estimation unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Ashikaga 2-17-17 Osaki, Shinagawa-ku, Tokyo Stock Company Shameidensha (72) Inventor Takayuki Mizuno 2-1-117 Osaki, Shinagawa-ku, Tokyo Stock Association Shameidensha (72) Inventor Yoshinori Nakano 2-17 Osaki, Shinagawa-ku, Tokyo Stock company Shameidensha

Claims (4)

[Claims] 1. A DC brushless motor as a drive source for a wheel, an inverter that controls a stepping angle of an accelerator pedal as a torque command T _ACC and controls an armature current of the motor according to a current command according to the torque command, and the inverter. In an electric vehicle equipped with a battery serving as a DC power source, the limiting value T _m of the torque command is calculated from the rotational speed n of the motor and the open circuit voltage V _{o of the} battery as 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 : internal battery resistance K _o : motor no-load loss coefficient, a limiter value calculation unit and the torque command T
An electric vehicle, comprising: a limiter circuit for limiting _ACC with the limit value T _m . 2. In place of the limiter circuit, the torque command T _ACC is calculated from a limit value T _m from the limiter value calculation unit and a torque command value T _max limited by the maximum allowable current of the inverter, and T = T. An electric vehicle having a full-scale adjusting unit for limiting to _ACC x (T _m / T _max ). 3. An electric vehicle comprising a battery parameter estimation unit that obtains the open circuit voltage V _o and internal resistance R _i of the battery from the depth of discharge of the battery and the battery characteristics. 4. A battery parameter estimation for obtaining an open circuit voltage V _{o of the} battery as a voltage E _D when the motor control is stopped, and obtaining an internal resistance R _i from the current I _D during the motor control and the voltages V _o , E _D. An electric vehicle characterized by having a section.