Method and device for determining output torque of motor and vehicle
阅读说明：本技术 确定电机输出扭矩的方法、装置及车辆 (Method and device for determining output torque of motor and vehicle ) 是由 孙赫男 于 2018-08-10 设计创作，主要内容包括：本公开涉及一种确定电机输出扭矩的方法、装置及车辆。在该方法中,由于电机控制系统的效率会随着电池电压的降低而降低,因此,在确定电机控制系统的当前效率时,除了考虑到电机的当前转速和当前扭矩之外,还考虑了电池的当前电压。这样,可以准确地确定出电机控制系统的当前效率,进而可以根据该当前效率,精确地计算出电机的当前最大允许输出功率,之后,根据该当前最大允许输出功率,可以确定出电机的最大允许输出扭矩。因此,采用上述技术方案,不仅可以确保在不同的电池电压下,车辆具有最优的动力性能,还可以避免因电机控制系统效率计算不准确而导致电池出现过放现象,延长了电池的使用寿命。(The disclosure relates to a method and a device for determining output torque of a motor and a vehicle. In this method, since the efficiency of the motor control system may decrease as the voltage of the battery decreases, the current voltage of the battery is also taken into account in addition to the current rotational speed and the current torque of the motor when determining the current efficiency of the motor control system. Therefore, the current efficiency of the motor control system can be accurately determined, the current maximum allowable output power of the motor can be accurately calculated according to the current efficiency, and then the maximum allowable output torque of the motor can be determined according to the current maximum allowable output power. Therefore, by adopting the technical scheme, the vehicle can be ensured to have optimal power performance under different battery voltages, the phenomenon of over-discharge of the battery caused by inaccurate efficiency calculation of the motor control system can be avoided, and the service life of the battery is prolonged.)
1. A method of determining output torque of an electric machine, comprising:
obtaining the current available power P of the motor control systemsys；
Determining the current voltage V of the battery according to the corresponding relation among the preset battery voltage, the preset motor torque, the preset motor rotating speed and the preset motor control system efficiencycuThe target efficiency is corresponding to the current torque and the current rotating speed of the motor, and the target efficiency is determined as the current efficiency of the motor control system;
according to the current available power PsysAnd the current efficiency, determining the current maximum allowable output power of the motor;
and determining the maximum allowable output torque of the motor according to the current maximum allowable output power and the current rotating speed of the motor.
2. Method according to claim 1, characterized in that said obtaining of the currently available power P of the motor control systemsysThe method comprises the following steps:
according to the current voltage VcuAnd the present current I of the batterycuDetermining the present output power P of the batterycu；
Obtaining the current maximum allowable discharge power P of the batterymax；
According to the current output power PcuAnd the current maximum discharge power PmaxDetermining the current maximum available power P of the batteryus；
According to the current maximum available power PusAnd the current power of the whole vehicle accessory, and determining the current available power P of the motor control systemsysWherein, the vehicle accessory includes: a DC-DC converter, an air conditioner compressor, an electric heater, a high-pressure steering and an air pump.
3. Method according to claim 2, wherein said current output power P is dependent on said current output powercuAnd the current maximum discharge power PmaxDetermining the current maximum available power P of the batteryusThe method comprises the following steps:
determining the current output power PcuAnd the current maximum discharge power PmaxThe current ratio of (d);
determining a target battery power limiting coefficient corresponding to the current ratio according to a corresponding relation between a preset ratio of output power to maximum discharge power and a battery power limiting coefficient, wherein the battery power limiting coefficient is less than or equal to 1;
according to the current maximum discharge power PmaxAnd the target battery power limiting coefficient, determining the current maximum available power P of the batteryus。
4. The method according to claim 3, wherein the battery power limiting factor is equal to 1 when the ratio of the output power to the maximum discharge power is less than or equal to a preset threshold, and the battery power limiting factor is less than 1 when the ratio of the output power to the maximum discharge power is greater than the preset threshold.
5. The method of claim 4, wherein the battery power limiting factor varies inversely with the ratio of the output power to the maximum discharge power when the ratio of the output power to the maximum discharge power is greater than the preset threshold.
6. An apparatus for determining output torque of an electric motor, comprising:
a first obtaining module for obtaining the current available power P of the motor control systemsys；
The device comprises a first determining module, a second determining module and a control module, wherein the first determining module is used for determining target efficiency corresponding to the current voltage Vcu of a battery, the current torque and the current rotating speed of a motor according to the corresponding relation among preset battery voltage, motor torque, motor rotating speed and motor control system efficiency, and determining the target efficiency as the current efficiency of a motor control system;
a second determining module, configured to determine the current available power P obtained by the first obtaining modulesysDetermining the current maximum allowable output power of the motor according to the current efficiency determined by the first determining module;
and the third determining module is used for determining the maximum allowable output torque of the motor according to the current maximum allowable output power and the current rotating speed of the motor determined by the second determining module.
7. The apparatus of claim 6, wherein the first obtaining module comprises:
a first determining submodule for determining the current voltage VcuAnd the present current I of the batterycuDetermining the present output power P of the batterycu；
A first obtaining submodule for obtaining the current maximum allowable discharge power P of the batterymax；
A second determining submodule for determining the current output power P according to the current output power P determined by the first determining submodulecuAnd the current maximum discharge power P acquired by the first acquisition submodulemaxDetermining the current maximum available power P of the batteryus；
A third determining submodule for determining the current maximum available power P according to the current maximum available power P determined by the second determining submoduleusAnd the current power of the whole vehicle accessory, and determining the current available power P of the motor control systemsysWherein, the vehicle accessory includes: a DC-DC converter, an air conditioner compressor, an electric heater, a high-pressure steering and an air pump.
8. The apparatus of claim 7, wherein the second determination submodule comprises:
a ratio determination submodule for determining the current output power PcuAnd the current maximum discharge power PmaxThe current ratio of (d);
the coefficient determination submodule is used for determining a target battery power limiting coefficient corresponding to the current ratio determined by the ratio determination submodule according to the corresponding relation between the preset ratio of the output power to the maximum discharge power and the battery power limiting coefficient, wherein the battery power limiting coefficient is smaller than or equal to 1;
a power determining submodule for determining the current maximum discharge power P obtained by the first obtaining submodulemaxAnd determining the current maximum available power P of the battery by the target battery power limiting coefficient determined by the coefficient determination submoduleus。
9. The apparatus of claim 8, wherein the battery power limiting factor is equal to 1 when the ratio of the output power to the maximum discharge power is less than or equal to a preset threshold, and wherein the battery power limiting factor is less than 1 when the ratio of the output power to the maximum discharge power is greater than the preset threshold.
10. The apparatus of claim 9, wherein the battery power limiting factor varies inversely with the ratio of the output power to the maximum discharge power when the ratio of the output power to the maximum discharge power is greater than the preset threshold.
11. A vehicle, characterized by comprising: a battery, a motor, and a motor controller, wherein the motor controller is configured to perform the steps of the method of any of claims 1-5.
Technical Field
The disclosure relates to the technical field of vehicles, in particular to a method and a device for determining output torque of a motor and a vehicle.
Background
With the development of economy and the rapid increase of vehicle conservation, the energy crisis taking fossil as fuel is increasingly prominent, and the problem of environmental pollution caused by the energy crisis also becomes more serious. In order to solve the problems of energy and pollution, electric vehicles are widely popularized in various countries in the world, and compared with the traditional vehicles, the electric vehicles mainly use a vehicle-mounted power supply as power and use motors to drive wheels to run. Specifically, a battery is provided in the electric vehicle to provide power, which mainly supplies power to driving devices (e.g., MCU or motor) and vehicle accessories (e.g., DCDC, PTC, air conditioner compressor, high voltage steering, air pump, etc.). The mcu (motor control unit) is a motor control unit or a motor controller, and is configured to control an output torque of the motor according to an electric quantity obtained from the battery, where the dcdc (Direct Current to Direct Current) is a dc-dc converter, and the ptc (positive temperature coefficient) is an electric heater.
In general, the larger the output torque of the motor is, the larger the power provided by the battery to the MCU is, which may cause the power required by the MCU to be greater than the maximum power that can be provided by the battery, and further cause the over-discharge phenomenon of the battery, and reduce the service life of the battery. Therefore, a Vehicle Control Unit (VCU) is required to limit the output torque of the motor according to the maximum allowable output torque of the motor, and further limit the power of the MCU to prevent the over-discharge of the battery.
Disclosure of Invention
In order to achieve the above purpose, the embodiments of the present disclosure provide a method and an apparatus for determining an output torque of a motor, and a vehicle.
According to a first aspect of embodiments of the present disclosure, there is provided a method of determining an output torque of an electric machine, comprising:
obtaining the current available power P of the motor control systemsys；
Determining target efficiency corresponding to the current voltage Vcu of a battery, the current torque and the current rotating speed of a motor according to the corresponding relation among preset battery voltage, motor torque, motor rotating speed and motor control system efficiency, and determining the target efficiency as the current efficiency of a motor control system;
according to the current available power PsysAnd the current efficiency, determining the current maximum allowable output power of the motor;
and determining the maximum allowable output torque of the motor according to the current maximum allowable output power and the current rotating speed of the motor.
Optionally, the current available power P of the motor control system is obtainedsysThe method comprises the following steps:
according to the current voltage VcuAnd the present current I of the batterycuDetermining the present output power P of the batterycu；
Obtaining the current maximum allowable discharge power P of the batterymax；
According to the current output power PcuAnd the current maximum discharge power PmaxDetermining the current maximum available power P of the batteryus；
According to the current maximum available power PusAnd the current power of the whole vehicle accessory, and determining the current available power P of the motor control systemsysWherein, the vehicle accessory includes: a DC-DC converter, an air conditioner compressor, an electric heater, a high-pressure steering and an air pump.
Optionally, said current output power P is dependent on saidcuAnd the current maximum discharge power PmaxDetermining the current maximum available power P of the batteryusThe method comprises the following steps:
determining the current output power PcuAnd the current maximum discharge power PmaxThe current ratio of (d);
determining a target battery power limiting coefficient corresponding to the current ratio according to a corresponding relation between a preset ratio of output power to maximum discharge power and a battery power limiting coefficient, wherein the battery power limiting coefficient is less than or equal to 1;
according to the current maximum discharge power PmaxAnd the target battery power limiting coefficient, determining the current maximum available power P of the batteryus。
Optionally, when the ratio of the output power to the maximum discharge power is less than or equal to a preset threshold, the battery power limiting coefficient is equal to 1, and when the ratio of the output power to the maximum discharge power is greater than the preset threshold, the battery power limiting coefficient is less than 1.
Optionally, when the ratio of the output power to the maximum discharge power is greater than the preset threshold, the battery power limit coefficient and the ratio of the output power to the maximum discharge power are in a negative correlation variation relationship.
According to a second aspect of the embodiments of the present disclosure, there is provided an apparatus for determining an output torque of a motor, comprising:
a first obtaining module for obtaining the current available power P of the motor control systemsys；
The device comprises a first determining module, a second determining module and a control module, wherein the first determining module is used for determining target efficiency corresponding to the current voltage Vcu of a battery, the current torque and the current rotating speed of a motor according to the corresponding relation among preset battery voltage, motor torque, motor rotating speed and motor control system efficiency, and determining the target efficiency as the current efficiency of a motor control system;
a second determining module, configured to determine the current available power P obtained by the first obtaining modulesysDetermining the current maximum allowable output power of the motor according to the current efficiency determined by the first determining module;
and the third determining module is used for determining the maximum allowable output torque of the motor according to the current maximum allowable output power and the current rotating speed of the motor determined by the second determining module.
Optionally, the first obtaining module includes:
a first determining submodule for determining the current voltage VcuAnd the present current I of the batterycuDetermining the present output power P of the batterycu；
A first obtaining submodule for obtaining the current maximum allowable discharge power P of the batterymax；
A second determining submodule for determining the current output power P according to the current output power P determined by the first determining submodulecuAnd the current maximum discharge power P acquired by the first acquisition submodulemaxDetermining the current maximum available power P of the batteryus；
A third determining submodule for determining the current maximum available power P according to the current maximum available power P determined by the second determining submoduleusAnd the current power of the whole vehicle accessory, and determining the current available power P of the motor control systemsysWherein, the vehicle accessory includes: a DC-DC converter, an air conditioner compressor, an electric heater, a high-pressure steering and an air pump.
Optionally, the second determining sub-module includes:
a ratio determination submodule for determining the current output power PcuAnd the current maximum discharge power PmaxThe current ratio of (d);
the coefficient determination submodule is used for determining a target battery power limiting coefficient corresponding to the current ratio determined by the ratio determination submodule according to the corresponding relation between the preset ratio of the output power to the maximum discharge power and the battery power limiting coefficient, wherein the battery power limiting coefficient is smaller than or equal to 1;
a power determining submodule for determining the current maximum discharge power P obtained by the first obtaining submodulemaxAnd determining the current maximum available power P of the battery by the target battery power limiting coefficient determined by the coefficient determination submoduleus。
Optionally, when the ratio of the output power to the maximum discharge power is less than or equal to a preset threshold, the battery power limiting coefficient is equal to 1, and when the ratio of the output power to the maximum discharge power is greater than the preset threshold, the battery power limiting coefficient is less than 1.
Optionally, when the ratio of the output power to the maximum discharge power is greater than the preset threshold, the battery power limit coefficient and the ratio of the output power to the maximum discharge power are in a negative correlation variation relationship.
According to a third aspect of the embodiments of the present disclosure, there is provided a vehicle including: the motor controller is used for executing the method for determining the output torque of the motor according to the first aspect of the embodiment of the disclosure.
In the method for determining the output torque of the motor provided by the embodiment of the disclosure, since the efficiency of the motor control system is reduced along with the reduction of the voltage of the battery, the current efficiency of the motor control system is determined by taking the current voltage of the battery into consideration in addition to the current rotation speed and the current torque of the motor. Therefore, the current efficiency of the motor control system can be accurately determined, the current maximum allowable output power of the motor can be accurately calculated according to the current efficiency, and then the maximum allowable output torque of the motor can be determined according to the current maximum allowable output power. By adopting the technical scheme, the vehicle can be ensured to have optimal power performance under different battery voltages, the phenomenon of over-discharge of the battery caused by inaccurate efficiency calculation of the motor control system can be avoided, and the service life of the battery is prolonged.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:
FIG. 1 is a flow chart of a method of determining motor output torque provided by an embodiment of the present disclosure.
Fig. 2 is a flowchart of a method for obtaining currently available power of a motor control system according to an embodiment of the present disclosure.
Fig. 3 is another flowchart of a method for obtaining currently available power of a motor control system according to an embodiment of the present disclosure.
FIG. 4 is another flow chart of a method of determining motor output torque provided by an embodiment of the present disclosure.
Fig. 5 is a block diagram of an apparatus for determining output torque of a motor according to an embodiment of the present disclosure.
Detailed Description
The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
In practical applications, the VCU limits the output torque of the motor mainly according to the current maximum allowable output torque of the motor, wherein the current maximum allowable output torque of the motor is related to the current remaining capacity of the battery. The related art implementation for calculating the current maximum allowable output torque of the motor is as follows: step 1: the current maximum allowable discharge power of the battery is subtracted by the power of accessories (DCDC, air conditioners, PTC, high-voltage steering, air pumps and the like) of the whole vehicle to obtain the maximum allowable discharge power of the MCU; step 2: finding out the rated motor system efficiency of the corresponding MCU according to the motor torque and the rotating speed; and step 3: multiplying the maximum allowable discharge power of the MCU by the rated motor system efficiency of the MCU to obtain the maximum allowable output power of the motor; and 4, step 4: and obtaining the current maximum allowable output torque of the motor according to the maximum allowable output power of the motor, the current actual rotating speed of the motor and a motor power calculation formula. The VCU then limits the motor torque based on the current maximum allowable output torque.
However, according to the characteristics of the battery, the voltage of the battery decreases with the decrease of the battery State of Charge (SOC), that is, the voltage variation of the battery is a dynamic process, when the voltage of the battery decreases, the efficiency of the motor control system decreases, if the MCU still operates at the rated voltage (step 2 as above), the calculated maximum allowable output power of the motor will be inaccurate, and for example, when the actual voltage of the battery is lower than the rated voltage, if the MCU still operates at the rated voltage, the calculated maximum allowable output power of the motor in step 3 will be larger, and accordingly, the current maximum allowable output torque of the motor calculated in step 4 will be larger, so that the actual operating power of the MCU will be larger than the maximum allowable discharge power of the MCU, so that the over-discharge phenomenon of the battery occurs.
Therefore, in order to solve the problem that the service life of a battery is shortened due to the fact that the battery is over-discharged due to inaccurate efficiency of a motor control system, the embodiments of the present disclosure provide a method and an apparatus for determining the output torque of a motor, and a vehicle.
Referring to fig. 1, fig. 1 is a flowchart illustrating a method for determining an output torque of a motor according to an embodiment of the present disclosure. As shown in fig. 1, the method includes:
s11: obtaining the current available power P of the motor control systemsys。
As previously mentioned, the battery in the vehicle may provide power to the motor control system as well as to the vehicle accessories (e.g., DCDC, PTC, air conditioning compressor, high pressure steering, air pump, etc.), it being understood that a portion of the battery power is consumed by the vehicle accessories and another portion is consumed by the motor control system. Thus, in embodiments of the present disclosure, the maximum available power of the battery may be considered to be equal to the sum of the power of the vehicle accessory and the available power of the motor control system. The motor control system comprises an MCU and a motor, the MCU controls the motor to output torque, and the available power of the motor control system is the power of the MCU, namely the input power of the motor.
In view of the fact that the SOC value of the battery is continuously reduced along with the consumption of the electric quantity of the battery during the driving process of the vehicle, and accordingly, the electric quantity provided by the battery to the motor control system is also continuously reduced, that is, the available power of the motor control system is also correspondingly reduced, therefore, in the embodiment of the present disclosure, the currently available power P of the motor control system needs to be obtainedsys。
Wherein the currently available power P of the motor control systemsysMay be obtained by measuring the input power of the motor control system. However, considering this approach, it may result in the currently available power P being obtainedsysThe method is obtained under the condition that the battery is overdischarged or the vehicle is accelerated suddenly, so that the maximum allowable output torque of the motor determined subsequently is larger, the battery is overdischarged, and the service life of the battery is shortened. In addition, the above-mentioned obtaining method may also result in the obtained current available power PsysNot obtained at the maximum power currently provided by the battery, fromAnd the maximum allowable output torque of the motor determined subsequently is smaller, so that the vehicle cannot exert the maximum power performance of the vehicle.
Therefore, to guarantee the acquired PsysThe method is obtained under the condition that the battery is not over-discharged and the maximum power which can be provided by the battery currently, and the embodiment of the disclosure provides a method for obtaining the currently available power P of the motor control systemsysThe method (1). Referring to fig. 2, fig. 2 is a flowchart of a method for obtaining currently available power of a motor control system according to an embodiment of the present disclosure. As shown in fig. 2, S11 in fig. 1 includes the following steps:
s111: according to the present voltage VcuAnd the present current I of the batterycuDetermining the present output power P of the batterycu；
S112: obtaining the current maximum allowable discharge power P of the batterymax；
S113: according to the current output power PcuAnd the current maximum discharge power PmaxDetermining the current maximum available power P of the batteryus；
S114: according to the current maximum available power PusAnd the current power of the whole vehicle accessory, and determining the current available power P of the motor control systemsys。
Firstly, the battery management unit can read the current voltage V of the battery in real timecuAnd the present current IcuSo as to be dependent on the current voltage VcuAnd the present current IcuDetermining the current output power P of the batterycuIllustratively, it may be according to the formula Pcu＝Vcu·Icu/1000, calculating the current output power Pcu. Wherein the P iscuPossibly the output power in case of over-discharge of the battery, i.e. the current output power PcuGreater than the maximum allowed discharge power of the battery, and possibly the output power in the case of non-maximum allowed discharge power of the battery, i.e. the current output power PcuLess than the maximum allowed discharge power of the battery.
To determine whether the current battery is in an over-discharged state, or whether it is in an over-discharged stateIn the embodiment of the present disclosure, the current maximum allowable discharge power P of the battery is obtainedmaxTo determine the current state of the battery and to determine the current maximum available power P of the battery according to the current stateus. I.e. according to the current output power PcuAnd the current maximum discharge power PmaxDetermining the current maximum available power P of the batteryusWherein the current maximum discharge power PmaxCan be obtained directly from the battery management unit and the current maximum discharge power PmaxIs related to the current SOC value of the battery.
In particular, according to the current output power PcuAnd the current maximum discharge power PmaxDetermining the current maximum available power P of the batteryusReferring to fig. 3, fig. 3 is another flowchart of a method for obtaining a currently available power of a motor control system according to an embodiment of the present disclosure. As shown in fig. 3, S113 in fig. 2 includes the following steps:
s1131: determining the current output power PcuWith the current maximum discharge power PmaxThe current ratio of (d);
s1132: determining a target battery power limiting coefficient corresponding to the current ratio according to the corresponding relation between the preset ratio of the output power to the maximum discharge power and the battery power limiting coefficient, wherein the battery power limiting coefficient is less than or equal to 1;
s1133: according to the current maximum discharge power PmaxAnd a target battery power limiting coefficient, determining the current maximum available power P of the batteryus。
The current output power P is determined according to the above-mentioned modecuAnd obtaining the current maximum discharge power PmaxThen, the current output power P is measuredcuAnd the current maximum discharge power PmaxComparing, i.e. determining, the current output power PcuWith the current maximum discharge power PmaxThe current ratio, which may reflect whether the battery is currently in an over-discharge state. When the current ratio is smaller than a preset threshold value, the battery is indicated to be in the maximum allowable output power rangeThe inner part of the device works normally. When the current ratio is greater than the preset threshold, it indicates that the battery is in an over-discharge state, and at this time, in order to avoid over-discharge of the battery, a corresponding relationship between the ratio of the output power to the maximum discharge power and the battery power limit coefficient may be set for the battery, where the corresponding relationship may be preset by a driver or default when the vehicle leaves a factory.
The possible implementation of the corresponding relationship between the preset ratio of the output power to the maximum discharge power and the battery power limit coefficient is as follows: when the ratio of the output power to the maximum discharge power is less than or equal to a preset threshold, the battery power limiting coefficient is equal to 1, that is, the current maximum discharge power P ismaxDetermining the current maximum available power P of the batteryusDue to no current maximum discharge power P to the batterymaxLimiting so that the maximum power performance of the vehicle can be exerted; when the ratio of the output power to the maximum discharge power is greater than the preset threshold, it indicates that the SOC of the battery is low, the battery is in an over-discharge state, or the vehicle is in a rapid acceleration state, at this time, the battery management unit does not accurately control the battery, and the response speed of the battery is slow, at this time, the current maximum discharge power P of the battery needs to be setmaxThe limitation is performed, that is, the battery power limit coefficient is set to a value smaller than 1 when the above ratio is larger than a preset threshold.
The preset threshold may be set by the vehicle when the vehicle leaves the factory, or may be set by the driver, and the smaller the preset threshold is, the smaller the probability of the over-discharge of the battery is, but the poorer the dynamic performance of the vehicle is. The larger the preset threshold value is, the greater the probability of the over-discharge of the battery is, the easier the battery is to be damaged, but the better the power performance of the vehicle is, in the embodiment of the present disclosure, the over-discharge problem of the battery and the power performance of the vehicle are considered together, and the preset threshold value may be set to 1.
When the preset threshold is 1, if the current output power P isusNot more than the current maximum discharge power PmaxCurrent maximum discharge power PmaxI.e. the current maximum available power P of the batteryus. If the current output power PusGreater than the maximum discharge power PmaxThe maximum discharge power needs to be limited by the target battery power limit coefficient.
Optionally, when the ratio is greater than the preset threshold, the battery power limit coefficient is in a negative correlation variation relationship with the ratio.
As described above, when the ratio of the output power to the maximum discharge power is greater than the preset threshold, the control of the battery by the battery management unit is inaccurate, and the response speed of the battery is slow, and specifically, the greater the ratio, the poorer the accuracy of the control of the battery by the battery management unit and the slower the response speed of the battery are. Therefore, when setting the corresponding relationship between the battery power limiting coefficient and the ratio, it is preferable to set the battery power limiting coefficient and the ratio to have a negative correlation variation relationship, that is, the larger the ratio is, the smaller the battery power limiting coefficient corresponding to the larger the ratio is, the smaller the current maximum discharge power P for the battery ismaxThe greater the limit of (c). It should be noted that the relationship between the battery power limiting coefficient and the above ratio can be expressed by a mathematical formula, a curve, a table, or the like, and is not limited in the embodiment of the present disclosure.
Table 1 shows a correspondence between a ratio of output power to maximum discharge power and a battery power limit coefficient, which are preset as an example. Wherein, X is used for representing the ratio of the output power to the maximum discharge power, and Y is used for representing the battery power limiting coefficient. For example, the preset threshold is 1, when the ratio X is smaller than or equal to 1, the battery power limiting coefficients Y are all 1, when the ratio X is greater than 1, the battery power limiting coefficients Y are all smaller than 1, and the battery power limiting coefficients Y and the ratio X have a negative correlation variation relationship, as shown in table 1:
TABLE 1 Table of correspondence between preset ratio of output power to maximum discharge power and battery power limit coefficient
X
0.8
0.9
1
1.05
1.1
1.15
1.2
1.25
1.3
Y
1
1
1
0.95
0.9
0.85
0.8
0.75
0.7
Assume the current output power P determined in the above-mentioned S1131cuWith the current maximum discharge power PmaxThe current ratio is 1.2, and the target battery power limit coefficient corresponding to the current ratio can be determined to be 0.8 by looking up table 1.
After the target battery power limiting coefficient is determined, the current maximum discharge power P can be usedmaxAnd the target battery power limit systemNumber, determining the current maximum available power P of the batteryus(i.e., execution of S1133). Illustratively, the current maximum discharge power P may bemaxMultiplying by the target battery power limit coefficient to calculate the current maximum available power P of the batteryus。
As previously described, the vehicle accessory power plus the motor control system power equals the battery power, and accordingly, the current maximum available power P of the batteryusI.e. the current power of the vehicle accessories and the current available power P of the motor control systemsysIn the disclosed embodiment, therefore, the current maximum available power P of the battery can be determinedusAnd the current power of the finished automobile accessory, and determining the current available power P of the motor control systemsysThe current maximum available power PusSubtracting the current power of the accessories of the whole vehicle to obtain the current available power P of the motor control systemsys。
It should be noted that, since the air conditioner compressor, the PTC, the high-pressure steering, and the air pump are not equipped with current sensors, and the power is variable, the power of the devices cannot be monitored in real time, and the rated power of the devices is usually determined as their current power. Since the real-time voltage and current of the DCDC can be monitored, the power of the DCDC can be calculated by monitoring the voltage and current of the DCDC in real time.
By adopting the technical scheme, the current maximum available power P of the battery is determinedusWhen the vehicle is in a rapid acceleration state or a battery over-discharge state, the battery management unit controls the battery inaccurately and the response speed of the battery is slow, so that the over-discharge phenomenon of the battery is avoided.
Returning to fig. 1, S12: determining the current voltage V of the battery according to the corresponding relation among the preset battery voltage, the preset motor torque, the preset motor rotating speed and the preset motor control system efficiencycuA target efficiency corresponding to the current torque and the current rotation speed of the motor, and determining the target efficiency asCurrent efficiency of motor control systems.
Considering that the voltage variation of the battery is a dynamic process, when the voltage of the battery is reduced, the efficiency of the motor control system is reduced, and if the system efficiency when the motor is operated at the rated voltage is still calculated, the calculated maximum allowable output power of the motor is inaccurate. Therefore, in the embodiment of the present disclosure, the correspondence between the motor rotation speed and the motor torque at different voltages and the motor control system efficiency is calibrated in advance, that is, the correspondence between the battery voltage, the motor torque, the motor rotation speed and the motor control system efficiency is set in advance, where the correspondence may be set when the vehicle leaves a factory or set by a driver.
It should be noted that the preset corresponding relationship may be a corresponding relationship between the motor rotation speed, the motor torque and the system efficiency in different voltage ranges, or a corresponding relationship between the motor rotation speed, the motor torque and the system efficiency in different voltage values. The method comprises the following steps: the correspondence relationship between the motor rotation speed, the motor torque, and the system efficiency may be set to be relationship 1 when the voltage range is V1 to V2, may be set to be relationship 2 when the voltage range is V2 to V3, and the like, or may be set in advance for each voltage value. Likewise, the correspondence relationship between the battery voltage, the motor torque, the motor rotation speed, and the motor control system efficiency may be in the form of a mathematical formula, a curve, a table, or the like, and is not limited in the embodiment of the present disclosure.
Thus, in the disclosed embodiments, the present voltage V of the battery is knowncuThe current torque and the current rotating speed of the motor can be determined from the corresponding relation among preset battery voltage, motor torque, motor rotating speed and motor control system efficiencycuAnd determining the target efficiency as the current efficiency of the motor control system.
S13: according to the current availabilityPower PsysAnd a current efficiency, determining a current maximum allowed output power of the motor.
Currently available power P of motor control systemsysI.e. the currently available power of the motor, which is also the currently maximum input power of the motor, the currently available power P of the motor control system is determined at S11, abovesysAnd S12 determines the current efficiency of the motor control system, from which the current maximum allowable output power of the motor can be determined. Illustratively, the currently available power PsysThe current efficiency is multiplied to obtain the current maximum allowable output power of the motor.
S14: and determining the maximum allowable output torque of the motor according to the current maximum allowable output power and the current rotating speed of the motor.
After the current maximum allowable output power of the motor is determined in S13, the maximum allowable output torque of the motor may be determined according to the current maximum allowable output power and the current rotation speed of the motor. The torque of the motor is determined according to the output power and the rotating speed of the motor, which are well known to those skilled in the art and will not be described herein.
In the method for determining the output torque of the motor provided by the embodiment of the disclosure, since the efficiency of the motor control system is reduced along with the reduction of the voltage of the battery, the current efficiency of the motor control system is determined by taking the current voltage of the battery into consideration in addition to the current rotation speed and the current torque of the motor. Therefore, the current efficiency of the motor control system can be accurately determined, the current maximum allowable output power of the motor can be accurately calculated according to the current efficiency, and then the maximum allowable output torque of the motor can be determined according to the current maximum allowable output power. By adopting the technical scheme, the vehicle can be ensured to have optimal power performance under different battery voltages, the phenomenon of over-discharge of the battery caused by inaccurate efficiency calculation of the motor control system can be avoided, and the service life of the battery is prolonged.
Referring to fig. 4, fig. 4 is another flowchart of a method for determining an output torque of a motor according to an embodiment of the present disclosure. As shown in fig. 4, the method of determining the output torque of the motor includes the following steps.
In S41, according to the present voltage V of the batterycuAnd the present current IcuDetermining the present output power P of the batterycu。
In S42, the current maximum allowable discharge power P of the battery is acquiredmax。
In S43, the current output power P is judgedcuWhether it is greater than the current maximum allowable discharge power Pmax. If so, S45 is performed, otherwise S44 is performed.
In S44, the current maximum allowable discharge power PmaxDetermining the current maximum available power P of the batteryus。
In S45, the preset table is queried to determine the battery power limit coefficient. The preset table is a table between the ratio of the output power to the maximum discharge power and the battery power limiting coefficient when the output power is greater than the maximum discharge power.
In S46, the current maximum allowable discharge power PmaxMultiplying by a battery power limit coefficient to determine the current maximum available power P of the batteryus。
At S47, the current maximum available power PusSubtracting the current power of the accessories of the whole vehicle to determine the current available power P of the motor control systemsys。
In S48, the present voltage V of the battery is determinedcuAnd (3) a range.
In S49, according to the current voltage VcuAnd determining the current efficiency of the motor control system in the range and the corresponding relation among the preset battery voltage, the preset motor torque, the preset motor rotating speed and the preset motor control system efficiency.
In S410, the current available power PsysMultiplied by the current efficiency, the current maximum allowed output power of the motor is determined.
In S411, the maximum allowable output torque of the motor is determined based on the current maximum allowable output power and the current rotation speed of the motor.
As shown in figure 4 of the drawings,first, the current voltage V of the battery is obtained from the battery management unitcuAnd the present current IcuAccording to the formula Pcu＝Vcu·IcuCalculating the current output power P of the battery by 1000cuAt the same time, the current maximum allowable discharge power P of the battery is obtainedmax. And judging PcuWhether or not greater than PmaxAt PcuNot more than PmaxWhen it is, P ismaxDetermining the current maximum available power P of the batteryus。
At PcuGreater than PmaxWhen is in accordance with PcuAnd PmaxAnd querying a preset table to determine the battery power limit coefficient. The preset table is a table between the ratio of the output power to the maximum discharge power and the battery power limiting coefficient when the output power is greater than the maximum discharge power. Next, after determining the battery power limiting factor, P is determinedmaxMultiplying by a battery power limit coefficient to determine the current maximum available power P of the batteryus。
Determining the current maximum available power P in either caseusThen, the current maximum available power PusSubtracting the current power of the accessories of the whole vehicle to determine the current available power P of the motor control systemsys。
Then, the present voltage V of the battery is determinedcuIn accordance with the current voltage VcuAnd determining the current efficiency of the motor control system in the range and the corresponding relation among the preset battery voltage, the preset motor torque, the preset motor rotating speed and the preset motor control system efficiency.
Finally, the current available power P of the motor control system is determined according to the abovesysAnd the current efficiency, determining the current maximum allowable output power of the motor, and determining the maximum allowable output torque of the motor according to the current maximum allowable output power and the current rotating speed of the motor.
Considering that the efficiency of the motor control system decreases with the decrease of the battery voltage, if the current maximum allowable output power of the motor is calculated with the efficiency under the rated voltage, the current maximum allowable output power is larger, the maximum allowable output torque of the motor is larger, and when the requested torque of the user is determined according to the maximum allowable output torque, the over-discharge phenomenon of the battery may occur, which affects the service life of the battery.
Therefore, in the embodiment of the present disclosure, the corresponding relationship between the motor rotation speed, the motor torque and the motor efficiency under different voltages is increased, so that the current efficiency of the motor can be determined according to the current voltage of the battery, the current rotation speed of the motor and the current torque, and then the current maximum allowable output power of the motor and the maximum allowable output torque of the motor are calculated according to the current efficiency. By adopting the method, the optimal power performance of the vehicle under different battery voltages can be ensured, the over-discharge phenomenon of the battery caused by inaccurate efficiency of a motor control system can be avoided, and the service life of the battery is prolonged.
In addition, when the current maximum available power of the battery is determined, the current output power of the battery is compared with the maximum discharge power of the battery, and when the current output power is greater than the maximum discharge power, the maximum discharge power is limited, so that the problems that the battery management unit cannot accurately control the battery and the response speed of the battery is low in the rapid acceleration or over-discharge state of the vehicle are solved, and the over-discharge phenomenon of the battery is further avoided.
Based on the same inventive concept, the embodiment of the disclosure also provides a device for determining the output torque of the motor. Referring to fig. 5, fig. 5 is a block diagram of an apparatus for determining an output torque of a motor according to an embodiment of the present disclosure. As shown in fig. 5, the apparatus 50 for determining the output torque of the motor includes:
a first obtaining module 501, configured to obtain a currently available power P of the motor control systemsys；
A first determining module 502, configured to determine, according to a preset correspondence relationship between a battery voltage, a motor torque, a motor rotation speed, and a motor control system efficiency, a target efficiency corresponding to a current voltage Vcu of the battery, a current torque of the motor, and a current rotation speed, and determine the target efficiency as a current efficiency of the motor control system;
a second determining module 503, configured to determine the current available power P obtained by the first obtaining module 501sysAnd the current efficiency determined by the first determining module 502, determining a current maximum allowed output power of the motor;
a third determining module 504, configured to determine a maximum allowable output torque of the motor according to the current maximum allowable output power and the current rotation speed of the motor determined by the second determining module 503.
Optionally, the first obtaining module includes:
a first determining submodule for determining the current voltage VcuAnd the present current I of the batterycuDetermining the present output power P of the batterycu；
A first obtaining submodule for obtaining the current maximum allowable discharge power P of the batterymax；
A second determining submodule for determining the current output power P according to the current output power P determined by the first determining submodulecuAnd the current maximum discharge power P acquired by the first acquisition submodulemaxDetermining the current maximum available power P of the batteryus；
A third determining submodule for determining the current maximum available power P according to the current maximum available power P determined by the second determining submoduleusAnd the power of the whole vehicle accessory, and determining the current available power P of the motor control systemsysWherein, the vehicle accessory includes: a DC-DC converter, an air conditioner, an electric heater, a high-pressure steering and an air pump.
Optionally, the second determining sub-module includes:
a ratio determination submodule for determining the current output power PcuAnd the current maximum discharge power PmaxThe current ratio of (d);
the coefficient determination submodule is used for determining a target battery power limiting coefficient corresponding to the current ratio determined by the ratio determination submodule according to the corresponding relation between the preset ratio of the output power to the maximum discharge power and the battery power limiting coefficient, wherein the battery power limiting coefficient is smaller than or equal to 1;
a power determining submodule for determining the current maximum discharge power P obtained by the first obtaining submodulemaxAnd determining the current maximum available power P of the battery by the target battery power limiting coefficient determined by the coefficient determination submoduleus。
Optionally, when the ratio of the output power to the maximum discharge power is less than or equal to a preset threshold, the battery power limiting coefficient is equal to 1, and when the ratio of the output power to the maximum discharge power is greater than the preset threshold, the battery power limiting coefficient is less than 1.
Optionally, when the ratio of the output power to the maximum discharge power is greater than the preset threshold, the battery power limit coefficient and the ratio of the output power to the maximum discharge power are in a negative correlation variation relationship.
With regard to the apparatus in the above-described embodiment, the specific manner in which each module performs the operation has been described in detail in the embodiment related to the method, and will not be elaborated here.
Based on the same inventive concept, the embodiment of the present disclosure further provides a vehicle, including: the motor controller is used for executing the method for determining the output torque of the motor according to the first aspect of the embodiment of the disclosure.
The preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.
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