JPH08172800A - Induction motor controlling system for electric car - Google Patents

Abstract

PURPOSE: To provide an induction motor controlling equipment for an electric car which can improve a torque responsiveness with peak current being held down. CONSTITUTION: Forward and backward external forces to be applied to a vehicle are estimated by an external force estimating section 18 based on a rotation speed and a target torque of an induction motor. According to the magnitudes of the estimated value of the external force value Td* and a torque command value Te*, either one is applied to a magnetic flux arithmetic section 11. When the estimated value of the external force is larger than the torque command value, the magnetic flux of a high efficiency proportional to the estimated value of the external force can be preliminarily formed in the induction motor before the torque command value rises and a cut-off frequency in a target torque arithmetic section 14 can be varied according to the formed magnetic flux. In other words, this equipment is so structured that it may more quickly respond to a torque command value and hold down peak current if the cut-off frequency are set at high levels according to the target magnetic flux.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an induction motor used in an electric vehicle, and more particularly to a technique for improving torque responsiveness while suppressing peak current.

[0002]

2. Description of the Related Art In order to clarify the problems of the prior art,
First, the vector control of a known induction machine will be described. Considering a rectangular coordinate system (γ-δ coordinates) that rotates at the power source angular velocity applied to the induction motor, the circuit equation of the induction motor is described as shown in the following (Equation 1).

[0003]

[Equation 1]

In the present specification, including the above equation (1), the following symbols represent the following contents. i _γs : γ-axis stator current (excitation current) i _δs : δ-axis stator current (torque current) φ _γr : γ-axis rotor magnetic flux φ _δr : δ-axis rotor magnetic flux ν _γs : γ-axis stator voltage ν _δs : Δ-axis stator voltage R _s : stator resistance R _r : rotor resistance L _s : stator self-inductance L _r : rotor self-inductance M: mutual inductance between stator and rotor ω: power frequency ω _re : Rotor angular velocity (electrical angle) P: Number of pole pairs σ = 1-M ² / L _s L _{r Further} , the output torque T _e is represented by the following formula (Formula 2).

[0005]

[Equation 2]

Here, _assuming that the stator currents i _γs and i _δs are current-controlled, the equation (1) can be rewritten as the following equation (3).

[0007]

(Equation 3)

When the formula on the second line of the formula (3) is rewritten, the formula (4) is obtained.

[0009]

[Equation 4]

However, ω _se is the slip frequency (= ω−
ω _re ). By rewriting the equation (4), the following equation (5) is obtained.

[0011]

(Equation 5)

However, S is a Laplace operator. From the equation (5), the following equation (6) must be established to make the δ-axis rotor magnetic flux φ _δr zero.

[0013]

(Equation 6)

Further, if the relation of φ _δr = 0 is substituted into the equation (3), φ _γr is given by the following equation (7).

[0015]

(Equation 7)

Similarly, by substituting the relationship of φ _δr = 0 into the equation (2), the output torque T _e can be expressed by the following equation (8).

[0017]

(Equation 8)

From the above results, if the slip frequency ω _se is given by the equation (6), the γ-axis rotor magnetic flux φ _γr becomes the first-order lag of the γ-axis stator current i _γs , and the motor output torque T _e is γ.
It is proportional to the product of the axial rotor magnetic flux φ _γr and the δ-axis stator current i _δs . The above is the outline of vector control. In a vector-controlled motor, the γ-axis stator current i _γs is called an exciting current, and the δ-axis stator current i _δs is called a torque current. In normal vector control, torque control is _performed with the rotor magnetic flux φ _{γr kept} constant. By _keeping φ _γr constant, (PM / L _r ) · φ _{γr in the} equation (8) becomes a constant, so the output torque becomes proportional to only the torque current, and high-speed torque response characteristics can be obtained. . However, such constant magnetic flux control generally supplies a constant exciting current regardless of the load of the motor, and therefore generally deteriorates the efficiency under a light load. In order to solve the above-mentioned problem, the applicant of the present invention has invented a device for minimizing the motor loss in the steady state and the stator peak current during the transient torque response by changing the rotor magnetic flux, and has already filed the application. (Japanese Patent Application No. 5-166998: unpublished). Hereinafter, the high efficiency control method in the above-mentioned prior application will be described. When copper loss is considered as the motor loss, the motor loss L _c in the steady state can be expressed by the following (Equation 9).

[0019]

[Equation 9]

To minimize the equation (9), dL _c / d
The slip frequency that satisfies ω _se = 0 may be obtained. The loss minimum slip frequency ω _se-opt that satisfies the above condition is expressed by the following (Equation 10).

[0021]

[Equation 10]

In order to set the slip frequency to the minimum loss slip frequency ω _{se-opt of the} equation (10), the following equation (6) is used.
It can be seen that the relationship between the torque current i _δs and the rotor magnetic flux φ _γr is given by the following (Equation 11).

[0023]

[Equation 11]

Substituting equation (11) into equation (8), i
_{When δs} is deleted, the following equation (12) is derived as the relationship between the torque T _e and the rotor magnetic flux φ _γr .

[0025]

(Equation 12)

Therefore, in order to obtain the magnetic flux command value φ * which minimizes the motor loss in the steady state, the output torque T _e is rewritten as the torque command value T _e * by the equation (12) and the following (equation 1)
Calculate the magnetic flux command value φ _γr * by the formula 3).

[0027]

(Equation 13)

Next, the magnetic flux command value φ which minimizes the motor loss in the steady state is calculated by using the equation (14) obtained by modifying the equation (8).
A torque current command value i _T * is calculated from * and the torque command value T _e *.

[0029]

[Equation 14]

Further, the exciting current command value i _φ * is (Equation 7)
The calculation is performed using the following formula (15) obtained by modifying the formula.

[0031]

(Equation 15)

The slip frequency ω _se can be calculated by replacing φ _γr with φ * and i _δs with i _T * in the equation (6). However, as can be seen from the equation (13), with respect to the torque command value that changes stepwise, the magnetic flux command value also becomes a step signal that changes stepwise. Therefore, when the torque command value is a step signal, the exciting current command value _iφ * transiently increases rapidly from the equation (15), the exciting current becomes a large current, and excessive transient loss occurs. Therefore, in the above-mentioned prior application, a target magnetic flux calculation unit including a low-pass filter with a first-order lag shown in the following (Formula 16) is provided, and the excitation current peak value is suppressed by reducing the amount of change in the magnetic flux. ing. These calculations are as shown in the following equations (16) and (17).

[0033]

[Equation 16]

[0034]

[Equation 17]

Here, φ _r is the target magnetic flux calculated by the target magnetic flux calculating section, and ω _φ is the cutoff frequency in the target magnetic flux calculating section. However, when the target magnetic flux φ _r is set to the equation (16), the equation (14) becomes the following equation (18). Therefore, the target magnetic flux φ _r gradually rises with respect to the stepped torque command value, This time, the torque current command value i _T * transiently increases rapidly and the torque current becomes a large current, resulting in excessive transient loss.

[0036]

(Equation 18)

Therefore, in the above-mentioned prior application, the responsiveness of the target torque is set as in the following equation (19).

[0038]

[Formula 19]

However, T _m is the target torque, and ω _T is the cutoff frequency for the target torque calculation. Therefore, the torque current command value i _T * (= i _δs ) can be obtained by calculating the following equation (20).

[0040]

(Equation 20)

FIG. 8 is a block diagram showing the control system of the prior application constructed as described above. In FIG. 8, 11 is a steady loss minimum magnetic flux calculation unit, and
Flux command value φ that minimizes steady loss by calculating the formula
Output *. Reference numeral 12 is a target magnetic flux calculation unit, and
6) performs the calculation of equation obtains a target magnetic flux phi _r, and calculates the first-order differential value d / dt φ _r of the target magnetic flux phi _r. Reference numeral 13 denotes an exciting current calculation unit, which performs the calculation of the equation (17). 14
Is a target torque calculation unit, which calculates the equation (19). Reference numeral 15 denotes a torque current calculation unit, which calculates the equation (20). Reference numeral 16 is a slip frequency calculation unit, which calculates the slip frequency ω _se by performing the calculation of the following equation (21) from the torque current command value i _T * and the target magnetic flux φ _r .

[0042]

[Equation 21]

Reference numeral 17 denotes a motor rotation speed calculation unit,
The number of pole pairs of the motor is added to the rotational angular velocity ω _r (mechanical angle) of the motor.
This is a block for calculating the angular velocity ω _re (electrical angle) of the motor rotor by multiplying by, and the power source frequency ω is calculated by adding this angular velocity ω _re and the slip frequency ω _se . Further, in the above-mentioned prior application, as shown in FIG. 9, with respect to the given cutoff frequency ω _T in the target torque calculation, the cutoff frequency of the target magnetic flux calculation that minimizes the peak loss when the stepwise torque command value is input. ω _φ
It is disclosed that it becomes possible to drive the motor with high efficiency both in the transient state and in the steady state by focusing on the existence of the above, and configuring the control system using this ω _φ .

[0044]

However, in the above-mentioned prior application of the applicant of the present invention, it is possible to minimize the peak current for realizing the set target torque, but it is necessary to calculate the target torque. In order to increase the cutoff frequency, that is, to obtain a fast torque response to a given torque command value (for example, the accelerator pedal operation amount), it is inevitable that the peak current becomes large. In the case of an electric vehicle, when stopping uphill temporarily or when going uphill when entering a garage, etc., stop and start are often finely adjusted by adjusting the accelerator pedal. In some situations, faster torque response to the accelerator pedal is preferred. However, as in the above-mentioned prior application, in the control in which the exciting current, that is, the magnetic flux is raised in response to the operation of the accelerator pedal, a sufficient responsiveness is obtained at the time of a normal start on a level ground. In such a situation, the torque response is insufficient. Therefore, if the cutoff frequency of the target torque calculation is controlled to be high in order to speed up the torque responsiveness by detecting the above situation, the peak current becomes large for a fast accelerator operation, and the fastest response is Since it is determined by the current capacity of the inverter, there is a problem that the torque response cannot be sufficiently increased.

The present invention has been made to solve the problems of the prior application as described above, and provides an induction motor control device for an electric vehicle capable of improving the torque response while suppressing the peak current. The purpose is to do.

[0046]

In order to achieve the above object, the present invention is constructed as described in the claims. That is, in the invention described in claim 1, the magnetic flux calculating means for calculating the rotor magnetic flux of the induction motor according to the signal given from the following torque signal switching means, and the rotor magnetic flux are input to obtain the target magnetic flux and Target magnetic flux calculating means for calculating the first derivative of the target magnetic flux, cutoff frequency calculating means for calculating the cutoff frequency in the following target torque calculating means according to the target magnetic flux, a torque command value given from the outside and the cutoff frequency. And a target torque calculating means for calculating a target torque of the induction motor from the torque command value based on a transfer function having the cutoff frequency of the given cutoff frequency as a cutoff frequency of the low-pass characteristic, the target torque and the electric vehicle External force estimating means for estimating an external force applied in the longitudinal direction of the vehicle from a signal correlated with wheel rotation, the torque command value and the external force estimated value And a torque signal switching determination means for outputting a selection signal for selecting one of the torque command value and the external force estimated value according to the magnitude relationship between the two, the torque command value and the external force estimated value. Torque signal switching means for selecting and outputting any one of the torque command value and the external force estimated value according to the selection signal, and the target magnetic flux and the above based on the circuit constant of the induction motor. A vector control calculation unit that calculates a current command value according to the first-order differential value of the target magnetic flux, the target torque, and the rotational angular velocity of the induction motor, and a motor drive that causes the current flowing in the induction motor to follow the current command value. And a section. The above configuration corresponds to, for example, the embodiment shown in FIGS. 1 and 2 described later. Further, the signal correlated with the wheel rotation of the electric vehicle in the external force estimating means, for example, the rotation speed of the wheel, the rotation speed of the induction motor,
It means signals such as rotational angular velocity and vehicle speed of an electric vehicle.

Further, the invention according to claim 2 is such that the magnetic flux calculating means is configured to calculate the rotor magnetic flux which minimizes the steady loss of the induction motor at a given torque command value. is there. In the invention according to claim 3, the target magnetic flux calculation means is configured to perform the target magnetic flux calculation using a filter having a transient response characteristic that minimizes the transient loss of the induction motor. is there. Further, in the invention according to claim 4, the torque signal switching determining means is configured to have a shift position signal, a brake signal, and a wheel for selecting forward / backward movement of the electric vehicle in addition to the torque command value and the external force estimated value. One of the torque command value and the external force estimated value is also input depending on the magnitude relationship between the torque command value and the external force estimated value, the shift position, the operating state of the brake, and the vehicle speed by inputting a signal correlated with rotation. Is configured to output a selection signal for selecting. The configuration described above is shown in FIG.
The processing procedure in the torque signal switching judging means is, for example, as shown in the flowcharts of FIGS. 6 and 7 described later.

[0048]

As described above, according to the first aspect of the invention, it is applied in the front-rear direction of the vehicle based on the target torque and the signal correlated to the wheel rotation of the electric vehicle such as the rotation speed of the induction motor and the vehicle speed. Estimate external force. The external force corresponds to a propulsive force for stopping the vehicle by an accelerator pedal (the operation amount is a torque command value) on an uphill or the like or a motor torque equivalent thereto. Then, either one of the external force estimated value and the torque command value is applied to the magnetic flux computing means in accordance with the magnitude relation between the two. Therefore, when the external force estimated value is larger than the torque command value, that is, before the torque command value rises, a highly efficient magnetic flux corresponding to this external force estimated value can be formed in the induction motor. Accordingly, if the cutoff frequency in the target torque calculation is made variable, that is, if the cutoff frequency in the target torque calculation is set high according to the target magnetic flux, a torque control system that responds quickly to the torque command value becomes possible.
And in this case, because the magnetic flux is started up first,
It does not increase the peak current. Therefore, the output torque response can be improved without increasing the peak values of the exciting current and the torque current, so when stopping temporarily on an uphill or when parking a car in the garage in the back on an uphill. For example, the operation becomes easy in a situation where the accelerator pedal is repeatedly operated to stop and start.

Further, in the invention of claim 2, it is possible to control so as to minimize the steady loss, and in the invention of claim 3, it is possible to perform control so as to minimize the transient loss. Further, in the invention of claim 4, either one of the torque command value and the external force estimated value is selected in accordance with the magnitude relation between the torque command value and the external force estimated value, the shift position, the operating state of the brake, and the vehicle speed. With this configuration, as will be described later in detail in the embodiment of FIG. 5, when it is not necessary to improve the torque response, the magnetic flux is not formed in advance, so that the efficiency can be further improved.

[0050]

1 and 2 are block diagrams of a first embodiment of the present invention. FIG. 2 is a block diagram of the entire vector control system of an induction motor, and FIG. 1 is a highly efficient drive control calculation of FIG. The part 1 is shown. First, in FIG. 2, reference numeral 1 is a high-efficiency drive control calculation unit, which is a feature of the present invention, and details are shown in FIG. 1 (details will be described later). Reference numeral 2 denotes a coordinate conversion unit that converts the excitation current command value i _φ * and the torque current command value i _T * calculated in the γ-δ axis coordinate system that rotates at the motor power supply frequency ω into the three-phase current command value i _u. Convert to *, i _v *, i _w *. 3 is current control PW
It is an M inverter and causes the three-phase current flowing through the induction motor 4 to follow the respective command values. Reference numeral 5 denotes a rotation angular velocity sensor that detects the angular velocity (mechanical angle) of the rotor and also serves as a vehicle speed sensor. Reference numeral 6 denotes a DC power supply, specifically, a vehicle-mounted battery. The high-efficiency drive control calculation unit 1 is the same as the normal vector control system.

Next, FIG. 1 is a detailed diagram of the high-efficiency drive control calculation unit 1 of FIG. In FIG. 1, 11 is a steady loss minimum magnetic flux calculating unit, 12 is a target magnetic flux calculating unit, 13 is an exciting current calculating unit, and 14 is a target torque calculating unit, which will be described later.
The target torque is calculated by the transfer function of the cutoff frequency given by the cutoff frequency calculation unit. Reference numeral 15 is a torque current calculation unit, 16 is a slip frequency calculation unit, and 17 is a motor rotation speed calculation unit. Further, 18 is an external force estimating unit, 19 is a torque signal switching determining unit, 20 is a torque signal switching unit, and 2 is a torque signal switching unit.
Reference numeral 1 is a cutoff frequency calculation unit. Of the above-mentioned configurations, the steady loss minimum magnetic flux calculation unit 11, the target magnetic flux calculation unit 12, the excitation current calculation unit 13, the torque current calculation unit 15, the slip frequency calculation unit 16, and the motor rotation speed calculation unit 17 are as described above. The configuration is similar to that of FIG. In the present embodiment, the steady loss minimum magnetic flux calculation unit 11 is provided to calculate the magnetic flux that minimizes the steady loss. However, instead of the steady loss minimum magnetic flux calculation unit 11, torque signal switching is simply performed. A unit for calculating the magnetic flux according to the external force estimated value or the torque command value given from the unit 20 may be provided.

Next, the operation will be described. In the configuration of FIG. 1, an external force estimation unit 18, a torque signal switching determination unit 19, a torque signal switching unit 20, and a cutoff frequency calculation unit 21 are added to the configuration of FIG. The difference from FIG. 8 is that the frequency is changed according to the magnetic flux. The contents other than these are the same as the above-mentioned prior application of FIG. Hereinafter, the operations of 18 to 21 will be mainly described.

First, the external force estimating unit 18 will be described.
The external force estimation unit 18 estimates an external force applied to the front and rear of the vehicle. The differential equation of the vehicle speed with respect to the target torque T _m or the rotational angular velocity ω _r of the motor equivalent thereto is given by
It is assumed to be represented by the formula 2).

[0054]

[Equation 22]

Therefore, the transfer function G _P (s) from the target torque T _m to the rotational angular velocity ω _r is given by the following equation (23).

[0056]

(Equation 23)

[0057] Figure 3 is a transfer function G _P (s) as a control target, when the external force applied thereto was T _d, is a block diagram showing a control system for estimating the T _d. In FIG.
H (s) is a low-pass filter having a steady gain of 1, and a filter having a relative order that does not include differentiation in the calculation of H (s) / _GP (s) is selected. In this embodiment, G
_Since the relative order of _P (s) is 1, a low-pass fill with a first-order delay shown in the following (Equation 24) is used as H (s).

[0058]

[Equation 24]

Therefore, H (s) / _GP (s) is given by the following equation (25).

[0060]

(Equation 25)

Next, the operating principle of the control system of FIG. 3 will be described. In FIG. 3, the rotational angular velocity ω _r of the rotor can be expressed by the following equation (26).

[0062]

(Equation 26)

The rotational angular velocity ω _r is _calculated as H (s) / G _P (s)
When input to the compensator, the output y ₁ is
It becomes like Formula (7).

[0064]

[Equation 27]

On the other hand, the output y _{2 of} the low-pass filter H (s)
Is expressed by the following (Equation 28), the difference between y ₁ and y ₂ is expressed by the following (Equation 29), and the external force T _d and its estimated value in the frequency range in which the transfer characteristic of the low-pass filter H (s) is 1. T _d *
Turns out to match.

[0066]

[Equation 28]

[0067]

[Equation 29]

The external force estimating unit 18 does not necessarily estimate only physical disturbance such as running resistance. For example,
When the brake is released while the vehicle is stopped on a slope, the vehicle gradually accelerates, but the external force estimation unit 18 estimates an external force equivalent to the acceleration at that time on flat ground. Therefore, it is understood that the external force estimated value is the force that stops acceleration at that time.

Next, returning to FIG. 1, other components will be described. The torque command value T _e * is a signal corresponding to the operation amount of an accelerator pedal (not shown). The torque signal switching determination unit 19 inputs the torque command value T _e * and the external force estimated value T _d *,
The external force estimation value T _d * is input to the steady loss minimum magnetic flux calculation unit 11 when the absolute value of the external force estimated value T _d * is larger than the absolute value of the torque command value T _e *, the torque command value T otherwise _e *
A selection signal for switching the torque signal switching unit 20 is output so that the constant loss minimum magnetic flux calculation unit 11 is input. Because when the absolute value of the external force estimated value T _d * of the is greater than the torque command value T _e * of the absolute value, it means before the torque command value T _e * rises, in the arrangement,
Before the torque command value T _e * rises, a magnetic flux corresponding to the external force estimated value T _d * is formed in advance. The determination using the absolute value as described above is because the external force in both the front direction and the rear direction of the vehicle can be considered.

Next, the operation of the cutoff frequency calculator 21 will be described. First, it is assumed that the torque signal switching unit 20 selects the external force estimated value T _d * shown in FIG. At this time, the target magnetic flux φ _r rises at the time constant (= 1 / ω _φ ) set by the target magnetic flux calculation unit 12. If the target magnetic flux φ _r becomes large to some extent, as can be seen from the equation (20), the torque current command value i _T * is excessively large even if the target torque T _m that rapidly increases is input to the torque current calculation unit 15. Never have a peak current. Therefore, after the magnetic flux of the induction motor is started up in advance, the accelerator pedal is depressed and the torque command value i _e * rises sharply, and the target torque T _m that increases sharply accordingly is input to the torque current calculator 15. However, the torque current command value i _T * does not have an excessive peak current. Therefore, if the cutoff frequency of the target torque calculation is set high in accordance with the target magnetic flux φ _r , a torque control system that responds quickly to the torque command value T _e * becomes possible, and the peak current will not become excessive. For example, the cutoff frequency calculation unit 21 performs calculation as shown in the following (Equation 30).

[0071]

[Equation 30]

In the equation (30), ω _T0 is an initial value of the cutoff frequency for the target torque calculation, and is set to a value necessary and sufficient for starting on a level ground. This value is the same as the cutoff frequency of the target torque calculation in the above-mentioned prior application. Further, K is a constant, and the selection method is, for example, the target magnetic flux φ _r when the maximum torque command value is input.
On the other hand, T _m ≈T _e *, that is, K that sets the cutoff frequency ω _T such that the delay of the target torque with respect to the torque command value can be almost ignored can be selected. Further, this calculation is not necessarily limited to the equation (30), and the cutoff frequency ω _T may be obtained using a table map regarding the target magnetic flux φ _r .

FIG. 4 is a characteristic diagram showing a simulation result for confirming the effect of this embodiment, (a) is the characteristic in the above-mentioned prior application, and (b) is the characteristic of this embodiment.
This simulation attempts to determine the ease of vehicle speed control on an uphill road from the manipulated variable of the torque command value. That is, the degree of change of the torque command value T _e * is changed so that the responsiveness of the target torque T _m is substantially the same in the prior application of (a) and the present embodiment of (b), and the operation amount at that time is changed. It is determined from the size whether it is easy to control. According to the result of FIG. 4, in the present embodiment shown in (b), the operation amount on the slope is smaller than that in the prior application of (a), and it is expected that the speed fine adjustment of the vehicle can be easily performed. Further, in (b), the peak values of the exciting current command value I _φ * and the torque current command value I _T * decrease, and it can be seen that the peak values in the transient state decrease.

Next, FIG. 5 is a block diagram of a second embodiment of the present invention, which shows a part of the high-efficiency drive control operation section 1 of FIG. In this embodiment, the torque signal switching determination unit 19
The operation of is determined not only by the torque command value T _e * and the external force estimated value T _d *, but also by including the vehicle speed (the rotation angular velocity ω _r is used because it is equivalent to the motor rotation angular velocity), the shift position signal SP and the brake signal BSW. To do. The shift position signal SP is a signal indicating whether the shift lever is in the forward position or the reverse position, and the brake signal BSW is a signal indicating whether or not the brake is operating. For example, a signal of a brake switch is used.

Next, the operation will be described. In the present embodiment, when the first embodiment is applied, it is configured so that unnecessary magnetic flux is not formed when it is not necessary to improve the torque response, and the efficiency is further improved. Is. That is, as described above, the first embodiment is particularly effective for a use only at a relatively low speed such as temporarily stopping on an uphill or entering a garage at the back, so that the downhill or the vehicle speed is high. In some cases, it may be unnecessary. For example, on a downhill, the shift position is the forward position (D range).
If it is, it does not need more responsiveness than is required on level ground. Further, in the first embodiment, when decelerating with the brake, the decelerating force is judged to be an equivalent external force and the magnetic flux is raised, but this is also unnecessary. Further, if the speed is too fast even on an uphill road, the speed may be adjusted by returning the accelerator, but in such a case, it is not necessary to raise the magnetic flux to further improve the responsiveness.
Therefore, the torque signal switching determination unit 19 in this embodiment operates as follows.

(1) The vehicle speed is a certain predetermined value V ₀ (for example, 5 k
m / h) Even if the absolute value of the external force estimated value T _d * is larger than the absolute value of the torque command value T _e *, the torque command value T _e * is input to the steady loss minimum magnetic flux calculation unit 11. A switching signal that causes the output is output. (2) Even if the brake signal BSW is on an absolute value greater than the absolute value of the external force estimated value T _d * is the torque command value T _e * (when braking), the steady torque command value T _e * A switching signal for inputting to the minimum loss magnetic flux calculation unit 11 is output. (3) When the shift position signal SP is in the forward position (D range) The external force estimated value T _d * has a negative polarity (the external force is applied in the direction of moving the vehicle backward) and the external force estimated value T _d * When the absolute value is larger than the absolute value of the torque command value T _e *, the switching signal for outputting the external force estimated value T _d * to the steady loss minimum magnetic flux calculation unit 11 is output. Therefore, when the polarity of the external force estimated value T _d * is positive, even if the absolute value of the external force estimated value T _d * is larger than the absolute value of the torque command value T _e *,
The torque command value T _e * is input to the steady loss minimum magnetic flux calculation unit 11. (4) When the shift position signal SP is in the backward position (R range) The polarity of the external force estimated value T _d * is positive (the external force is applied in the direction of moving the vehicle forward) and the external force estimated value T _d * When the absolute value is larger than the absolute value of the torque command value T _e *, the switching signal for outputting the external force estimated value T _d * to the steady loss minimum magnetic flux calculation unit 11 is output. Therefore, when the polarity of the external force estimated value T _d * is negative, even if the absolute value of the external force estimated value T _d * is larger than the absolute value of the torque command value T _e *,
The torque command value T _e * is input to the steady loss minimum magnetic flux calculation unit 11. By configuring as above,
When it is not necessary to improve the torque responsiveness, useless magnetic flux is not formed in advance, so that the efficiency can be further improved.

FIGS. 6 and 7 are flowcharts showing the processing procedure for realizing the above controls (1) to (4). First, in FIG. 6, in step S1, it is determined whether or not the absolute value of the vehicle speed is higher than a predetermined value V ₀ . If "no" in step S1, it is determined in step S2 whether or not the brake switch signal is ON (when the brake is operating). If "no" in step S2, step S3
It is determined whether or not the shift position is the forward drive position, and if it is the forward drive position, the process goes to the logic D in FIG. In the case of "no", it is determined in step S4 whether or not the shift position is in the reverse position. In the case of the reverse position, the process goes to the logic R in FIG. 7, and in the case of "no", the process goes to step S5. If “yes” in steps S1 and S2, that is, if the vehicle speed is higher than the predetermined value or the brake is on, the process goes to step S5. In step S5, a switching signal for inputting the torque command value T _e * to the steady loss minimum magnetic flux calculation unit 11 is selected.

Further, in the logic D of FIG. 7, first, in step S6, it is determined whether or not the polarity of the external force estimated value T _d * is positive. If “no” in the step S6, the absolute value of the torque command value T _e * is the external force estimated value T in a step S7.
_It is determined whether or not it is larger than the absolute value of _d *, and if "no", a switching signal for inputting the estimated external force value _Td * to the steady loss minimum magnetic flux calculation unit 11 is selected in step S8. Further, in the case of “yes” in steps S6 and S7, that is, when the polarity of the external force estimated value T _d * is positive or when the absolute value of the torque command value T _e * is larger than the absolute value of the external force estimated value T _d *. Is
In step S9, a switching signal for inputting the torque command value T _e * to the steady loss minimum magnetic flux calculation unit 11 is selected.

On the other hand, in the logic R of FIG. 7, first, in step S10, it is determined whether or not the polarity of the external force estimated value T _d * is negative. If “no” in step S10,
In step S11, it is determined whether the absolute value of the torque command value T _e * is larger than the absolute value of the external force estimated value T _d *, and “no” is determined.
In this case, in step S12, a switching signal for inputting the external force estimated value T _d * to the steady loss minimum magnetic flux calculation unit 11 is selected. Further, when “yes” in steps S10 and S11, that is, when the polarity of the external force estimated value T _d * is negative or when the absolute value of the torque command value T _e * is larger than the absolute value of the external force estimated value T _d *. Selects the switching signal for inputting the torque command value T _e * to the steady loss minimum magnetic flux calculation unit 11 in step S13.

Next, the difference between the prior art for improving the torque response and the present invention will be described below. For example, in Japanese Patent Laid-Open No. 59-156172, in order to improve the torque responsiveness at the time of starting, an exciting current is increased when a starting command is input, and a magnetic flux formed thereby is quickly raised. The configuration is described. However, in this configuration, since a large exciting current needs to flow, the torque response cannot be improved without increasing the exciting current as in the present invention. In the present invention, when the torque command value is smaller than the external force estimated value, that is, the magnetic flux corresponding to the external force estimated value is preliminarily raised before the torque command value rises, thereby increasing the exciting current. The torque responsiveness is improved without any problem. Further, Japanese Patent Application Laid-Open No. 3-74110 discloses a configuration that improves torque responsiveness when the vehicle is moving in a direction opposite to the direction in which it is about to travel. However, in the case of vector control, if the torque responsiveness is simply improved, the efficiency at the time of transition decreases, so that the effect of the present invention cannot be obtained even in this conventional example. Further, when the torque response is improved by ignoring the magnitude of the magnetic flux, the peak current increases during the transition, but in the present invention, the cutoff frequency of the target torque calculation is changed according to the magnitude of the magnetic flux. This makes it possible to improve the torque response without increasing the peak current.

[0081]

As described above, in the present invention, the external force applied in the front-rear direction of the vehicle is estimated, and the rotor magnetic flux is calculated according to the magnitude relationship between the estimated external force and the torque command value. By making a selection based on which value and changing the response in the target torque calculation according to the rotor magnetic flux, without increasing the peak value of the exciting current or the torque current, The responsiveness of output torque can be improved. Therefore, there is an effect that the operation becomes easy in a situation where the vehicle is stopped once on an uphill, the car is stored in the garage with the back on an uphill, and the operation is repeatedly stopped and started by operating the accelerator pedal. In addition to the magnitude relationship between the external force estimated value and the torque command value, the shift position position, the presence or absence of the brake operation, and the vehicle speed are used to determine which of the torque command value and the external force estimated value is to be used. In the configuration, when it is not necessary to improve the torque response,
Since the useless magnetic flux is not formed, the effect that the efficiency can be further improved is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention, showing a portion of a high-efficiency drive control calculation section 1 in FIG.

FIG. 2 is a block diagram showing the overall configuration of an induction motor vector control system.

[3] The transfer function G _P (s) as a control target, when the external force applied thereto was T _d, a block diagram showing a control system for estimating the T _d.

4A and 4B are characteristic diagrams showing simulation results for confirming the effects of the present embodiment, where FIG. 4A is the characteristic in the above-mentioned prior application, and FIG. 4B is the characteristic of the present embodiment.

FIG. 5 is a block diagram of a second embodiment of the present invention, and is a diagram showing a portion of the high efficiency drive control calculation section 1 in FIG.

FIG. 6 is a part of a flowchart showing a processing procedure for realizing control in the second embodiment.

FIG. 7 is another part of the flowchart showing the processing procedure for realizing the control in the second embodiment.

FIG. 8 is a block diagram showing the configuration of the applicant's prior application.

FIG. 9 is a characteristic diagram showing a relationship between a peak loss and a target magnetic flux cutoff frequency.

[Explanation of symbols]

1: High-efficiency drive control calculation unit 4: Induction motor 2: Coordinate conversion unit 5: Rotational angular velocity sensor 3: Current control PWM inverter 6: DC power supply 11: Steady loss minimum magnetic flux calculation unit 12: Target magnetic flux calculation unit 17: Motor rotation Number calculation unit 13: Excitation current calculation unit 18: External force estimation unit 14: Target torque calculation unit 19: Torque signal switching determination unit 15: Torque current calculation unit 20: Torque signal switching unit 16: Slip frequency calculation unit 21: Cutoff frequency calculation Department

Claims (4)

[Claims] 1. A magnetic flux calculating means for calculating a rotor magnetic flux of an induction motor according to a signal given from a torque signal switching means, and a rotor magnetic flux as an input to obtain a target magnetic flux and a first derivative of a target magnetic flux. A target magnetic flux calculating means, a cutoff frequency calculating means for calculating a cutoff frequency in the following target torque calculating means according to the target magnetic flux, a torque command value given from the outside and the cutoff frequency are inputted, and the given Target torque calculating means for calculating the target torque of the induction motor from the torque command value based on the transfer function having the cutoff frequency as the cutoff frequency of the low-pass characteristic, and from the signal correlating with the target torque and the wheel rotation of the electric vehicle. An external force estimating means for estimating an external force applied in the front-rear direction of the vehicle, and the torque command value and the external force estimated value are input, and the magnitude relationship between the two is input. According to the selection signal, the torque signal switching determination means for outputting a selection signal for selecting one of the torque command value and the external force estimated value, and the torque command value and the external force estimated value are input. Torque signal switching means for selecting and outputting any one of the torque command value and the external force estimated value, and the target magnetic flux and the first-order differential value of the target magnetic flux based on the circuit constant of the induction motor, and A vector control computing unit that computes a current command value according to a target torque and the rotational angular velocity of the induction motor; and a motor drive unit that causes the current flowing in the induction motor to follow the current command value. An induction motor control device for an electric vehicle that controls the output torque of the electric motor to a value corresponding to the target torque. 2. The magnetic flux calculating means calculates a rotor magnetic flux that minimizes a steady loss of the induction motor at a given torque command value.
An induction motor control device for an electric vehicle according to item 1. 3. The target magnetic flux calculation means performs the target magnetic flux calculation using a filter having a transient response characteristic that minimizes the transient loss of the induction motor. Item 3. An induction motor controller for an electric vehicle according to Item 2. 4. The torque signal switching determination means also inputs, in addition to the torque command value and the external force estimated value, a shift position signal for selecting forward / backward movement of the electric vehicle, a brake signal, and a signal correlated with the wheel rotation. Then, a selection signal for selecting one of the torque command value and the external force estimated value is output according to the magnitude relation between the torque command value and the external force estimated value, the shift position, the operating state of the brake, and the vehicle speed. The induction motor control device for an electric vehicle according to claim 1, wherein the induction motor control device is for an electric vehicle.