JPH0746721A - Method and apparatus for controlling motor for electric vehicle - Google Patents

Abstract

PURPOSE:To make it possible to operate motors with maximum efficiency without causing the burning of motors of an electric vehicle driven with a plurality of motors. CONSTITUTION:A required output for running is calculated with required output calculating means 2 depending on the running conditions detected by running condition detecting means 1. And the maximum outputs restricted for respective motors are set depending upon the temperature of each motor detected with the temperature detecting means 3 by the maximum output restricting means 4. Output set setting means 5 will set a plurality of output sets for allotting the required running output for each motor within the range of the maximum output, and power consumption calculating means 6 calculate the total power consumption for each output set. And control command means 7 output a control command to each motor in accordance with the output set which makes the smallest total power consumption. Since the allotment is determined in such a manner that the power consumption becomes the smallest within the range where the maximum output is restricted, continuous operation at momentary rating can be avoided and burning fracture can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for an electric vehicle for operating the electric vehicle having a plurality of motors while maximizing the efficiency of the entire motor.

[0002]

2. Description of the Related Art Vehicles traveling on general roads are operated in various driving patterns in accordance with traffic conditions and other factors. An electric vehicle using an electric motor as a power source cannot avoid this restriction, and the required output varies greatly. However, motors have the most efficient operating conditions,
In order to cover the maximum output required for running with a single motor, although the motor becomes large, it is usually operated in a state of low efficiency. For this reason, the applicant previously disclosed in Japanese Patent Application No. 3-17337 that a plurality of motors are connected to driving wheels of a vehicle to determine which one of the outputs is necessary for traveling.
When the power output of each motor is within the maximum output range, only that motor is operated independently, and when the required output exceeds the maximum output of this motor, another motor is additionally operated to supplement the output. is suggesting. As a result, the constantly driven motor operates under relatively efficient conditions.

[0003]

However, even in the above power control device, the required travel output P0 is not sufficient for the output PA of one motor MA, and the other motor MB is also driven at the same time due to the shortage PB. If it is necessary to do so, there is a problem that the total power consumption (= PA / ηA + PB / ηB) does not necessarily become the minimum when the operating efficiency of each motor is ηA and ηB. That is,
The efficiency of the motor is generally high in its rated region and is represented as shown in FIG. When the required travel output is expressed as the required torque T0 kgm at the rotational speed N0 rpm, in the case where the motor MA outputs the torque T1 and the shortage T0-T1 is applied to the motor MB in FIG. 13, the power consumption is

[Equation 1] Required by.

Here, as an example, T0 = 10 kgm, N0
= 2000 rpm, and letting the motor MA output 7 kgm near the maximum torque as the torque T1, the motor MA leaves the maximum efficiency region, for example, ηA = 7.
Assuming that the efficiency is 5% and the efficiency of the motor MB is also η B = 55%,

[Equation 2] Becomes On the other hand, the share torque of the motor MA is T2 = 5 kg
Assuming that ηA = ηB = 82% with equal efficiency is obtained when m,

[Equation 3] Becomes

As described above, when the output required for traveling exceeds the maximum output of one motor, if the other output is simply shared by another motor, useless power is consumed.
Therefore, it is desirable to operate the plurality of motors so as to maximize the efficiency as a whole. On the other hand, in the state where the total power consumption is minimized, one or more motors may be continuously operated at the instantaneous rating. That is, considering a typical example in the case of two motors, when the output torque of each motor is determined so that the total power consumption is minimized, as shown in FIG. The total power consumption is minimum when only the motor with the smallest maximum output of the two motors is used for output.
In addition, if the torque required for running is in the P range larger than that,
This time, the total power consumption becomes the minimum when only the motor with the largest maximum output is used for output.

By the way, in the range near the upper region boundary line of the E region or the P region in FIG. 14, although the required traveling torque is a relatively small value, considering each motor alone, the instantaneous ratings are respectively different. Will be driving. If the motor is continuously driven at such a point in the case of traveling at a constant speed, the temperature of one of the motors may rise, and the allowable temperature of the motor may be exceeded. Therefore, the present invention provides an electric vehicle in which a plurality of motors connected to driving wheels are selected and driven according to a running state,
An object of the present invention is to provide a motor control device for an electric vehicle, which can be operated at maximum efficiency as a whole without causing a defect due to a temperature rise of the motor exceeding an allowable temperature.

Therefore, the present invention according to claim 1 is a motor control method in an electric vehicle in which a plurality of motors are connected to drive wheels, the method including detecting a running condition,
A step of calculating a required travel output according to the traveling condition,
A step of detecting the temperature of each motor, a step of setting a limit value of each maximum output according to the detected temperature of each motor, and traveling within the range of the limit value for each of the plurality of motors There is a step of determining an output that shares a required output and outputting a control command to each of the motors, and the control command output step determines the shared output so as to minimize the total power consumption of the motor. I decided.

The invention according to claim 2 is a motor control device used for carrying out the above-mentioned method, and as shown in FIG. 1, the driving condition detecting means 1 and the driving condition are detected in accordance with the detected driving condition. Necessary output calculation means 2 for calculating the required travel output
A plurality of motors 8 connected to the drive wheels, a temperature detecting means 3 for detecting the temperature of each of the plurality of motors, and a maximum output limitation for setting a maximum output that is individually limited according to the temperature of the motors. Means 4 and output set setting means 5 for setting a plurality of output sets that share the required travel output within the set maximum output range for each of the plurality of motors,
A power consumption calculating means 6 for calculating the total power consumption of the plurality of motors in each output set, and an output set having the smallest total power consumption among the plurality of output sets are selected, and the selected output set is selected. Therefore, the control command means 7 for outputting a control command to each of the motors is provided.

[0009]

The output required for each motor is determined so that the total power consumption of those motors is minimized, and the control command is issued to each motor. The output is always supplied to the drive wheels with the lowest power consumption. When determining the shared output, set the maximum output limit value according to the temperature of each motor and determine the shared output within the range of this limit value. Continuous operation is avoided, and destruction due to seizure is prevented. Particularly, in the device of claim 2, a plurality of combinations of output sharing of each motor are set as an output set,
The total power consumption of each set is calculated, and the output sharing combination of the set having the minimum total power consumption is selected. A control command is output to each motor according to this sharing.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
FIG. 2 shows a first embodiment of the present invention. The first motor 20 and the second motor 21 are coaxially connected to drive wheels 27, 27 of the vehicle via a differential gear 26. A signal from the accelerator opening sensor 11 and a signal from the motor rotation sensor 22 are input to the controller 10. Further, the first and second motors 20 and 21 are provided with temperature sensors 24 and 25 for monitoring respective temperatures, and the signals thereof are input to the controller 10.

Motor drivers 12 and 13 are connected to the first and second motors 20 and 21, respectively, and output from the controller 10 having a microcomputer inside to each motor driver based on the accelerator opening and the number of rotations of the motor. A torque command is issued. Each function of the invention is realized by the microcomputer of the controller 10. Since the first and second motors 20 and 21 are connected on the same shaft, the output torques of the respective motors are added and the required travel torque T0 is input to the differential gear 26, and the drive wheels 27 are driven.

In the controller, the processing is performed according to the flow shown in FIGS. First, in step 100, the calculation set number is set as k = 1, and then in step 101, the accelerator opening sensor 1
The accelerator opening is read from 1 and the motor speed N0 is read from the rotation sensor 22 in step 102. Based on these, the required travel torque T0 is calculated in step 103.

Next, at step 104, from the temperature sensors 24 and 25, the motor temperature Sn (here, with two motors, n = 1 and 2, the same applies hereinafter), that is, here S1.
And S2 are read. And step 105
Then, it is checked whether or not these Sn are equal to or higher than the maximum allowable temperature Snmax preset for each motor. If at least one motor is at or above its Snmax, step 1
Proceed to 06.

In step 106, the maximum output torque Tnmax of the motor which is equal to or higher than Snmax is set limited to the maximum value Tnβmax within the continuous rating of the motor. On the other hand, for motors that have not reached Snmax, the maximum value T set in the range including the instantaneous rating
nαmax. That is, when the first motor: S1 ≧ S1max, the second motor: S2 <S2max, the respective maximum output torques are set to the first motor: T1max = T1βmax, the second motor: T2max = T2αmax. . The maximum values Tnαmax and Tnβm
ax has a relationship as shown in FIG.

When the first motor: S1 <S1max, the second motor: S2 ≧ S2max, the respective maximum output torques are as follows: First motor: T1max = T1αmax Second motor: T2max = T2βmax Is set. When the first motor: S1 ≧ S1max and the second motor: S2 ≧ S2max, the respective maximum output torques are as follows: first motor: T1max = T1βmax second motor: T2max = T2βmax.

If, in the check in step 105, Snmax has not been reached for any motor, the routine proceeds to step 107, where the maximum output torque of each motor is Tnα.
set to max. That is, the first motor: T1max = T1αmax, the second motor: T2max = T2αmax.

Following the previous step 106, step 10
8, the total of the maximum output torque Timax (i = 1, 2) newly set as described above and the required running torque T0
And are compared. Here, when ΣTimax <T0, the routine proceeds to step 117, where the output torque command Tn * of each motor is determined to the value of Timax set at step 106, and then output to the motor driver at step 115.

As described above, this is Tnαmax> T
Since it is nβmax, when the torque that can be output by all the motors has decreased, and when the required traveling torque T0 is still insufficient, each motor must be operated at its maximum output torque, and the efficiency determination described below is performed. The output torque command is issued soon. When ΣTimax ≧ T0 at step 108, the routine proceeds to step 110, where an output torque command determination routine including efficiency determination is entered. Even after the maximum output torque is set in step 107, the process proceeds to step 110.

In step 110, the required running torque T0
In order to achieve the above, the torque Tn that each motor should output within the range of the newly set maximum output torque described above.
First, k is assumed as a combination when k = 1. In step 111, based on a preset efficiency map, the torque command Tnk of each motor and the efficiency η1 of each motor at the number of revolutions N0 assumed above.
k and η2k are obtained. Then, in step 112, the total power consumption Pok is calculated by the following equation.

[Equation 4]

After steps 113 and 116, k = 1 to 1
The above steps 110 to 112 are repeated for the combination of M, so that the total power consumption Po1, Po2,
..., PoM is required. Next, in step 114, the set number k = * that gives the minimum value among Po1, Po2, ..., PoM is determined. In this way, the torque Tn * of each motor that minimizes the total power consumption is determined. Then, in step 115, Tn * is output as the output torque command of each motor.

Steps 101 to 102 are the running condition detecting means of the invention, step 103 is the required output calculating means, step 104 is the temperature detecting means, and steps 105 to 10 are.
7 is the maximum output limiting means, steps 110, 113, 1
16 is the output set setting means, and steps 111 and 112.
Is the power consumption calculation means, and steps 108, 11
Reference numerals 4, 115, and 117 respectively constitute control command means. As a result, the respective motors 20 and 21 are operated independently or simultaneously according to the output torque command sent to the motor drivers 12 and 13.

This embodiment is configured as described above. For motors that have detected the temperature of each motor and have risen above a predetermined temperature, the output is limited to the continuous rating range,
Since the output torque command of each motor was controlled so that the total power consumption was minimized, the output of a motor that was continuously operated at the instantaneous rating could be reduced to the continuous rating, causing damage such as seizure. It is prevented in advance, and is operated at maximum efficiency as a whole. In addition, even if the maximum output torque of the entire motor becomes smaller than the required running torque by limiting the motor output to the continuous rating range, the maximum torque in the limited range is output. This has the effect of operating at maximum efficiency. Regarding control, an efficiency characteristic map with respect to the number of rotations and output torque of the motor is prepared in advance for each motor, and power consumption and other output set selection can be obtained only by calculation in the controller 10, so that the device configuration is simple. There is an advantage that it can be realized at low cost.

FIG. 6 shows a second embodiment. In this embodiment, a temperature sensor attached to each of the first and second motors is eliminated, and an arithmetic unit 24 'for estimating the temperature of each motor 20, 21 is provided in the controller 10'. Other configurations are the same as those in FIG. The calculator 24 'estimates the temperature of each motor based on the output torque command and the motor rotation speed.

7 and 8 show the flow of processing in the controller. Here, in step 204 after step 103, the temperature Sn 'of each motor is calculated in step 204 from the motor speed N0 and the output torque command by the calculator 24'.
(S1 ', S2') is calculated. The output torque command is
The Tn * output in step 115 in the previous flow cycle is used. Then, the next step 205
Then, these Sn ′ are compared with the maximum allowable temperature Snmax preset for each motor. Depending on the comparison result, the process proceeds to step 206 or 207 similar to step 106 and 107 in FIG. Other steps 101 to 103 and steps 108 to 117 are the same as those in FIGS. 3 and 4.

FIG. 9 shows the details of the estimation and calculation of the motor temperature Sn 'in step 204. Here, in addition to the maximum allowable temperature Snmax of each motor,
Maximum temperature Snst 'during continuous operation with continuous rating
Is set as the reference temperature of each motor, and the temperature change per unit time of the motor when the motor whose initial temperature is Snst 'is continuously operated while outputting a constant torque at a constant rotation speed. A map is provided. In this map, the value of the temperature change per unit time is represented by a negative value within the continuous rating and a positive value within the instantaneous rating.

First, in step 301, from the motor speed N0 read in the previous step 102 and the output torque command Tn * (= T1 *, T2 *) output to each motor in step 115 of the previous flow, The temperature change Snch '(= S1ch', S2ch ') per unit time of each motor is read on the map showing the temperature change. Then, in step 302, each is multiplied by the sampling time τ, and in step 303, S1
The signs of ch ′ · τ and S2ch ′ · τ are checked to determine whether the operation is the instantaneous rating or the continuous rating.

When the Snch 'is a positive value, the operation is performed under the instantaneous rating, the process proceeds to step 305, and the estimated motor temperature Sn' at that time is added to the new motor temperature Sn. 'Is said. Also Snc
When h ′ is a negative value, it is determined that the operation is at the continuous rating, and the process proceeds to step 304. Step 304
Then, it is checked whether the estimated motor temperature Sn ′ at that time is higher than the previously set continuous rated maximum temperature Snst ′ as a reference.

If Sn 'is larger than Snst', the process proceeds to step 305. Step 30 in this case
In the addition in 5, Snch ′ · τ to be added is a negative value. If Sn ′ is less than or equal to Snst ′, the process proceeds from step 304 to step 306, where S
n '= Snst' is set. The estimated motor temperature Sn ′ thus calculated is compared with the maximum allowable temperature Snmax in the next step 205.

Since this embodiment is constructed as described above, it has the effect of operating at maximum efficiency as a whole while preventing damage due to seizure or the like, as in the previous embodiment. In addition to this, since the installation of the temperature sensor for each motor is omitted, there is an advantage that the configuration is simple and the cost is reduced.

Next, a third embodiment of the present invention will be shown. In the above-described two embodiments, when the motor temperature becomes equal to or higher than the reference temperature, the maximum output torque of the motor is limited to a value within the continuous rating, whereas in this embodiment, a plurality of efficiency maps corresponding to the motor temperature are set. Is prepared and based on this, control is performed so as to maximize the overall efficiency. The overall configuration is the same as in FIG. 2, but the processing in the controller is performed according to the flow shown in FIGS.

This flow shows the case where two motors are mounted as in FIG. First, in step 400, the operation set number is set as k = 1. Then, in step 401, the accelerator opening is read from the accelerator opening sensor, and in step 402, the motor rotation speed N0 is read from the rotation sensor. Based on these, the required travel torque T is set in step 403.
0 is calculated.

Next, at step 404, the motor temperatures Si and Sj are read from the temperature sensor attached to each motor. Then, in step 405, an efficiency map corresponding to the temperatures Si and Sj is selected from a plurality of efficiency maps corresponding to the motor temperatures preset for each motor.

Next, at step 406, the torque Tnk (= T1k, T2) to be output by each motor in order to achieve the required running torque T0 previously obtained.
k) is first assumed as a combination when k = 1. This hypothetical combination is performed under the following conditions. O ≦ Tnk ≦ Tnmax T0 = ΣTnk In step 407, based on the efficiency map selected in step 405, the torque commands T1k and T2k of each motor assumed above and the efficiency η1k and η2k of each motor at the rotation speed N0 are calculated. Desired. Then, step 408.
Then, the total power consumption Pok is calculated.

After steps 409 and 410, k = 1 to
The above steps 406 to 408 are repeated for the combination of M, so that the total power consumption Po1, Po2,
..., PoM is required. Next, in step 411, the combination number k = * that gives the minimum value among Po1, Po2, ..., PoM is determined. In this way, the torque Tn * of each motor that minimizes the total power consumption is determined, and in step 412 Tn * is output as the output torque command of each motor. Then, the output torque commands T1 * and T2 * output from the controller are sent to the motor driver, whereby each motor is driven simultaneously and independently.

The above efficiency maps for each temperature are obtained by experiments in advance, but if the efficiency map at the upper limit temperature of each motor is set to a value lower than the actual efficiency, variations in operating conditions and the like will occur. Even if there is, the switching of the motor is surely performed.

This embodiment is configured as described above, and an efficiency map for different motor temperatures is prepared in advance,
Based on this, the torque distribution to each motor is determined so that the overall efficiency is maximized. If the motor temperature rises and the winding resistance value increases, the loss increases and the motor efficiency decreases, so if one of the motors is operated continuously within the instantaneous rating and the temperature rises, As a result, the efficiency map is automatically switched, so that the torque is switched to the torque within the continuous rating based on the new torque distribution. As a result, the motors are automatically switched before the motors are burned, and each motor is driven so that the overall efficiency is maximized, that is, the power consumption is minimized under the conditions.

In the third embodiment, the output torque command Tn * output in step 413 can be further corrected according to the temperature change condition. That is, as shown in FIG. 12, first, the motor temperature Sn (t) at the time t and the previous motor temperature Sn
The difference (t-1) is multiplied by an appropriate gain Kp to obtain a signal a, and the difference between the maximum allowable temperatures Snmax and Sn (t) of the motor is multiplied by a gain Kd to obtain a signal b. A value c obtained by dividing the signal a by the signal b is multiplied by an appropriate gain Kg and standardized to obtain a signal d. Then, a value e obtained by subtracting the value of the signal d from 1
To the output torque command T output in step 413.
The signal f multiplied by n * is used as the final output torque command Tn * ′ to the motor. As a result, even when both motors are driven at the instantaneous rating, the output torque thereof can be reduced to prevent the seizure of the motors more reliably.

In each of the above-described embodiments, the case where two motors are mounted has been described, but the present invention is not limited to this, and can be applied to control of arbitrary plural motors. . At this time, the greater the number of motors, the more the maximum efficiency can be obtained with respect to the required travel torque in multiple stages. Therefore, it may be set according to the running mode of the average pattern of the actual vehicle, which is particularly frequent. Similarly, the number of combinations of output sets may be set corresponding to the average pattern.

[0039]

As described above, according to the present invention, the temperature of each of a plurality of motors is detected, and the output of a motor having a temperature equal to or higher than a preset predetermined temperature is limited within a predetermined limit range. Since the output torque of each motor is controlled so that the overall efficiency is maximized, for example, a motor that is continuously operated beyond the continuous rating does not have a shared output without changing the torque. By lowering, the temperature rise of the motor is kept within the allowable temperature.
Further, even if the maximum output torque of the whole becomes smaller than the required running torque due to the above-mentioned limitation, there is an effect that the maximum efficiency as a whole in that state can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a diagram showing a first embodiment of the invention.

FIG. 3 is a flowchart showing the operation of the embodiment.

FIG. 4 is a flowchart showing the operation of the embodiment.

FIG. 5 is a diagram showing an example of setting a maximum output torque of a motor.

FIG. 6 is a diagram showing a second embodiment.

FIG. 7 is a flowchart showing the operation of the second embodiment.

FIG. 8 is a flowchart showing the operation of the second embodiment.

FIG. 9 is a flowchart showing a flow of estimating and calculating a motor temperature.

FIG. 10 is a flowchart showing the operation of the third embodiment.

FIG. 11 is a flowchart showing the operation of the third embodiment.

FIG. 12 is a diagram showing a procedure for correcting an output torque command according to a temperature change.

FIG. 13 is an efficiency characteristic diagram showing the relationship between output torque and efficiency.

FIG. 14 is an explanatory diagram showing a region shared by a motor with respect to a required output torque.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Running condition detecting means 2 Necessary output calculating means 3 Temperature detecting means 4 Maximum output limiting means 5 Output set setting means 6 Power consumption calculating means 7 Control command means 10, 10 'controller 11 Accelerator position sensor 12, 13 Motor driver 20th 1 motor 21 2nd motor 22 rotation sensor 24, 25 temperature sensor 24 'calculator 26 differential gear 27 driving wheel N0 motor rotation speed T0 required torque Tn * output torque command Sn motor temperature

Claims (6)

[Claims] 1. A motor control method for an electric vehicle in which a plurality of motors are connected to driving wheels, the method comprising: detecting a traveling condition; calculating a required traveling output according to the traveling condition; A step of detecting the temperature, a step of setting a limit value for each maximum output in accordance with the detected temperature of each motor, and a required travel output within the range of the limit value for each of the plurality of motors. There is a step of determining an output to be shared and outputting a control command to each of the motors, and the control command output step is to determine the shared output so as to minimize the total power consumption of the motor. A motor control method for an electric vehicle, comprising: 2. A running condition detecting means, a required output calculating means for calculating a required running output according to the detected running condition, a plurality of motors connected to driving wheels, and respective temperatures of the plurality of motors. Temperature detection means for detecting, maximum output limiting means for setting a maximum output limited respectively according to the temperature of the motor, and the traveling within the range of the maximum output set for each of the plurality of motors Output set setting means for setting a plurality of output sets sharing the required output, power consumption calculating means for calculating the total power consumption of the plurality of motors in each output set, and total power consumption of the plurality of output sets Is selected, and a control command means for outputting a control command to each of the motors according to the selected output set is provided. Control device. 3. The running condition detection means includes a rotation sensor for detecting the rotation speed of the motor, and outputs of the required output calculation means and the output set setting means are torques at the rotation speed detected by the rotation sensor. The power consumption calculating means calculates the power consumption of each motor from the efficiency and the shared torque by obtaining the efficiency corresponding to the torque shared by each motor based on a preset map. The motor control device for an electric vehicle according to claim 2. 4. The motor control device for an electric vehicle according to claim 2, wherein the limited maximum output set by the maximum output limiting means is within a range of continuous rating of each motor. . 5. The electric vehicle motor control device according to claim 2, wherein the temperature detecting means is a temperature sensor attached to each of the plurality of motors. 6. The temperature detecting means estimates and calculates the temperature of each motor on the basis of the number of revolutions detected by the rotation sensor and each control command for the plurality of motors. 2. A motor control device for an electric vehicle according to 2, 3, or 4.