CN108583293B - Brake feedback torque distribution method of new energy automobile and four-wheel drive control system thereof - Google Patents
Brake feedback torque distribution method of new energy automobile and four-wheel drive control system thereof Download PDFInfo
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- CN108583293B CN108583293B CN201810570378.3A CN201810570378A CN108583293B CN 108583293 B CN108583293 B CN 108583293B CN 201810570378 A CN201810570378 A CN 201810570378A CN 108583293 B CN108583293 B CN 108583293B
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Abstract
The invention discloses a brake feedback torque distribution method of a new energy automobile, which comprises the following steps: the calculating system can absorb braking feedback torque, calculate the total braking feedback required torque of the system, calculate the stability expected feedback torque of the front axle, calculate the economy expected feedback torque of the front axle, calculate the braking feedback required torque of the rear axle, calculate the braking required torque of the front axle and the braking required torque of the rear axle, and calculate the mechanical braking required torque of the front axle and the rear axle. The method can calculate the total braking demand torque of the driver, can also judge whether the posture of the vehicle body is in the optimal stable state, and calculates the braking torque proportion of the front axle and the rear axle which maintains the optimal stability of the vehicle body. The method can well coordinate the management of electric energy, the stability of the vehicle and the electric driving system capacity of the front axle and the rear axle, and reasonably distribute the feedback torque between the front axle and the rear axle. The method is suitable for hybrid four-wheel drive vehicles with completely decoupled independent power source configurations at the front and rear axles. The invention also discloses a four-wheel drive control system of the new energy automobile.
Description
Technical Field
The invention relates to the technical field of new energy automobiles, in particular to a brake feedback torque distribution method of a new energy automobile and a four-wheel drive control system thereof.
Background
In recent years, energy and environmental problems are increasingly prominent, and the development of energy-saving, environment-friendly and efficient automobiles is a consensus of all circles of society. Under the background, electric vehicles and plug-in hybrid vehicles gradually step on the traffic stage, and the electric vehicles and the plug-in hybrid vehicles will replace more traditional vehicles to become transportation tools for people in the future. Accordingly, meeting social demands for automotive charging facilities is also becoming increasingly important.
In addition to work, people pay more and more attention to the remote self-driving tour, and accordingly, the requirement on the driving capability of the vehicle is higher and higher. Under such circumstances, four-wheel drive vehicles with new energy power systems (such as hybrid power systems or pure electric systems) are becoming increasingly popular.
Different from the engine driving mode of a conventional internal combustion engine powered vehicle, the driving mode of a new energy power system or a pure electric system is more flexible, and the system configuration is not limited to a single power source. The power configuration of the complete decoupling of the front axle and the rear axle is more flexible in arrangement, so that a larger arrangement space can be provided for the power battery, the power source can realize more intelligent control and more efficient braking energy feedback, and therefore the power configuration becomes a popular choice at present.
Compared with a two-drive automobile, the new energy automobile with the independent electrically-driven rear axle has better energy feedback potential, the electric drive systems of the front axle and the rear axle are reasonably utilized for speed reduction feedback, the feedback with the acceleration not lower than 0.3G can be realized, complete feedback can be realized on most common road surfaces, and even the intervention of a hydraulic braking system is rarely needed. Since feedback distribution involves coordination between management of electrical energy, vehicle stability, and the ability of the front and rear axle electric drive systems, rational distribution of the feedback torque between the front and rear axles is a key and difficult point to achieve the good potential of the system.
Disclosure of Invention
In view of the above, the present invention provides a method for distributing brake feedback torque of a new energy vehicle, which can reasonably distribute feedback torque between a front axle and a rear axle and exert good potential of the system. The invention also provides a four-wheel drive control system of the new energy automobile.
In order to achieve the purpose, the invention provides the following technical scheme:
a brake feedback torque distribution method of a new energy automobile comprises the following steps:
the computing system can absorb the brake feedback torque, and the system can absorb the brake feedback torque which is the absorbable brake feedback power of the system/(the efficiency of the motor system multiplied by the efficiency of the transmission system) multiplied by 9550/wheel speed, wherein the absorbable brake feedback power of the system is the total consumed power of the high-voltage load and the chargeable power of the power battery;
calculating the total braking feedback demand torque of the system, and calculating the total braking demand torque of the driver according to the vehicle speed and the position of the brake pedal in combination with the vehicle weight, wherein the total braking feedback demand torque of the system is MAX (the system can absorb the braking feedback torque and the total braking demand torque of the driver);
calculating the expected feedback torque of the stability of the front axle, and calculating the minimum brake torque ratio of the front axle according to the vehicle speed and the steering wheel angle, wherein the expected feedback torque of the stability of the front axle is the total brake feedback demand torque of the system multiplied by the minimum brake torque ratio of the front axle;
calculating the economic expected feedback torque of the front axle, establishing an economic expected torque MAP of the front axle by integrating efficiency characteristics of the front axle and the rear axle, and searching the economic expected torque MAP of the front axle by using the total braking feedback required torque of the system to obtain the economic expected feedback torque of the front axle;
calculating the front axle braking feedback required torque, wherein the front axle braking feedback required torque is MAX { MIN (front axle stability expected feedback torque, front axle economy expected feedback torque), and the current generating torque of a front axle motor };
calculating the rear axle braking feedback required torque, wherein the rear axle braking feedback required torque is MAX (front axle braking feedback required torque x (1-front axle minimum braking torque ratio)/front axle minimum braking torque ratio, and the current power generation torque of a rear axle motor);
calculating the required braking torque of the front axle and the rear axle, wherein the required braking torque of the front axle is equal to the ratio of the total braking required torque of a driver to the minimum braking torque of the front axle; rear axle brake demand torque ═ driver total brake demand torque × (1 — front axle minimum brake torque ratio);
calculating the mechanical braking required torque of the front axle and the rear axle, wherein the mechanical braking required torque of the front axle is equal to the braking required torque of the front axle-the actual braking feedback torque fed back by a front axle driving system; and the rear axle mechanical braking demand torque is equal to the rear axle braking demand torque-the actual braking feedback torque fed back by the rear axle driving system.
The invention provides a brake feedback torque distribution method of a new energy automobile, which comprises the following steps: the calculating system can absorb braking feedback torque, calculate the total braking feedback required torque of the system, calculate the stability expected feedback torque of the front axle, calculate the economy expected feedback torque of the front axle, calculate the braking feedback required torque of the rear axle, calculate the braking required torque of the front axle and the braking required torque of the rear axle, and calculate the mechanical braking required torque of the front axle and the rear axle. The method can calculate the total braking demand torque of the driver, can also judge whether the posture of the vehicle body is in the optimal stable state, and calculates the braking torque proportion of the front axle and the rear axle which maintains the optimal stability of the vehicle body. The method can well coordinate the management of electric energy, the stability of the vehicle and the electric driving system capacity of the front axle and the rear axle, reasonably distribute the feedback torque between the front axle and the rear axle and exert good potential of the system. The method is suitable for hybrid four-wheel drive vehicles with completely decoupled independent power source configurations at the front and rear axles.
The invention provides a four-wheel drive control system of a new energy automobile, which comprises: a power system control unit, a vehicle body stability controller, a steering wheel angle sensor, a wheel speed sensor, a front axle driving system, a rear axle driving system, a power battery and a brake pedal position sensor, wherein,
the power system control unit is used for calculating the absorbable brake feedback torque of the system, wherein the absorbable brake feedback torque of the system is the absorbable brake feedback power of the system/(the efficiency of a motor system multiplied by the efficiency of a transmission system multiplied by 9550 per wheel speed, and the absorbable brake feedback power of the system is the total consumed power of a high-voltage load and the chargeable power of a power battery; the power system control unit is also used for calculating the front axle economical expected feedback torque, establishing a front axle economical expected torque MAP by integrating the efficiency characteristics of a front electric bridge and a rear electric bridge, and searching the front axle economical expected torque MAP by using the total braking feedback required torque of the system to obtain the front axle economical expected feedback torque;
the vehicle body stability controller includes: a system total braking feedback demand torque calculation module, a front axle stability expected feedback torque calculation module, a front and rear axle braking feedback demand torque calculation module, a front and rear axle braking demand torque calculation module, a front and rear axle mechanical braking demand torque calculation module, wherein,
the system total braking feedback demand torque calculation module is used for calculating the total braking demand torque of a driver according to the vehicle speed and the position of a brake pedal in combination with the vehicle weight, wherein the total braking feedback demand torque of the system is MAX (the system can absorb the braking feedback torque and the total braking demand torque of the driver);
the front axle stability expected feedback torque calculation module is used for calculating the minimum braking torque ratio of the front axle according to the vehicle speed and the steering wheel angle, and the front axle stability expected feedback torque is equal to the total braking feedback demand torque of the system multiplied by the minimum braking torque ratio of the front axle;
the front axle and rear axle braking feedback demand torque calculation module is used for calculating front axle braking feedback demand torque and calculating rear axle braking feedback demand torque, the front axle braking feedback demand torque is MAX { MIN (feedback torque is expected for front axle stability and feedback torque is expected for front axle economy), the front axle motor can generate current torque }, the rear axle braking feedback demand torque is MAX { front axle braking feedback demand torque is x (1-front axle minimum braking torque ratio)/front axle minimum braking torque ratio, and the rear axle motor can generate current torque };
the front axle and rear axle braking demand torque calculation module is used for calculating front axle and rear axle braking demand torque, and the front axle braking demand torque is the ratio of the total braking demand torque of the driver and the minimum braking torque of the front axle; rear axle brake demand torque ═ driver total brake demand torque × (1 — front axle minimum brake torque ratio);
the front axle and rear axle mechanical braking demand torque calculation module is used for calculating front axle and rear axle mechanical braking demand torque, and the front axle mechanical braking demand torque is front axle braking demand torque-actual braking feedback torque fed back by a front axle driving system; the rear axle mechanical braking demand torque is rear axle braking demand torque-actual braking feedback torque fed back by a rear axle driving system;
the steering wheel corner sensor is used for collecting a steering wheel corner and sending a steering wheel corner signal to the vehicle body stability controller;
the wheel speed sensors are used for respectively acquiring the rotating speeds of four wheels and sending four-wheel rotating speed signals to the vehicle body stability controller so as to convert the four-wheel rotating speed signals into vehicle speed and four-wheel speeds;
the front axle driving system is used for providing driving torque to a front axle when a vehicle is driven and providing braking feedback torque when the vehicle is braked;
the rear axle driving system is used for providing driving torque for a rear axle when a vehicle is driven and providing braking feedback torque when the vehicle is braked;
the power battery is used for providing driving electric energy for the electric driving system when the vehicle is driven, and the electric energy fed back by the rear axle driving system and/or the front axle driving system can be stored when the vehicle is braked and fed back;
the brake pedal position sensor is used for converting the displacement or angular displacement of the brake pedal into a voltage signal and transmitting the voltage signal to the vehicle body stability controller;
the front axle driving system and the rear axle driving system are connected with the power battery and are connected with the vehicle body stability controller through the power system control unit, and the steering wheel corner sensor, the wheel speed sensor and the brake pedal position sensor are connected with the vehicle body stability controller.
Preferably, in the four-wheel drive control system of the new energy automobile, the power system control unit is integrated in the vehicle control unit.
Preferably, in the four-wheel drive control system of the new energy automobile, the vehicle body stability controller is internally provided with an acceleration sensor.
In the four-wheel drive control system of the new energy automobile, the automobile body stability controller integrates a brake feedback control function, can calculate the total brake required torque of a driver according to the automobile speed and the position change of a brake pedal, can also calculate the speed of four wheels and the automobile speed, simultaneously monitors the automobile body posture, judges whether the automobile body posture is in the optimal stable state or not by combining the steering wheel rotation angle, the automobile speed, the wheel speed and a built-in acceleration sensor thereof, and calculates the front and rear axle brake torque proportion for maintaining the optimal automobile body stability according to the information of the axle load (preset) of the front and rear axles of the automobile, the acceleration of the automobile, the steering wheel rotation angle and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a four-wheel drive control system of a new energy vehicle according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart of a brake feedback torque distribution method according to an embodiment of the present invention;
fig. 3 is an external characteristic curve of the motor in the embodiment of the present invention.
In fig. 1:
the system comprises a power system control unit 1, a vehicle body stability controller 2, a steering wheel angle sensor 3, a wheel speed sensor 4, a front axle driving system 5, a rear axle driving system 6, a power battery 7 and a brake pedal position sensor 8.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a four-wheel drive control system of a new energy vehicle according to an embodiment of the present invention. In order to reasonably distribute the feedback torque between the front axle and the rear axle and exert good potential of a four-wheel drive control system of a new energy automobile, the invention provides the four-wheel drive control system of the new energy automobile, as shown in fig. 1, the four-wheel drive control system comprises: the device comprises a power system control unit 1, a vehicle body stability controller 2, a steering wheel corner sensor 3, a wheel speed sensor 4, a front axle driving system 5, a rear axle driving system 6, a power battery 7 and a brake pedal position sensor 8. The functions and implementation processes of the parts are specifically as follows:
the control unit 1 of the power system, abbreviated as PCU, is used for calculating the total electric power that the vehicle high-pressure system can input and store, and combine the electric driving system ability and efficiency characteristic of the front axle and rear axle, calculate the feedback torque that the front axle and rear axle of the vehicle expect to output to the wheel end separately on the basis of the best economy; the vehicle high-voltage system is a system capable of storing electric energy, converting other capacity into electric energy and consuming the electric energy to meet other functional requirements of the vehicle, and the voltage of the system is not lower than 60V. Preferably, the power system control unit 1 in the present solution is integrated in the vehicle control unit, that is, relevant function software is integrated in the existing vehicle control unit, so that the parts can be conveniently arranged, and the parts are reduced. Of course, in this embodiment, the power system Control Unit 1 may also be designed as a separate controller, i.e., a Powertrain Control Unit, abbreviated as PCU.
The power system control unit 1 is configured to calculate a braking feedback torque that can be absorbed by the system, where the braking feedback torque is the braking feedback power that can be absorbed by the system/(motor system efficiency × transmission system efficiency) × 9550/wheel speed, where the braking feedback power that can be absorbed by the system is the total power consumption of the high-voltage load + the chargeable power of the power battery. The power system control unit 1 is further configured to calculate a front axle economy expected feedback torque, establish a front axle economy expected torque MAP by integrating efficiency characteristics of a front axle and a rear axle, and find the front axle economy expected torque MAP by using a system total braking feedback demand torque to obtain the front axle economy expected feedback torque.
The vehicle body Stability Controller 2 (ESC for short) is integrated with a brake feedback control function, and is configured to distribute a hydraulic brake torque and an Electric brake torque during a braking process, calculate a four-wheel speed and a vehicle speed, perform vehicle body Stability control according to a steering wheel angle, the vehicle speed and the wheel speed, calculate a total brake demand torque of a driver according to the vehicle speed and a brake pedal position change, calculate an expected front and rear axle deceleration torque ratio based on a vehicle Stability demand, and intervene in a power system as needed during the vehicle body Stability control. Specifically, the vehicle body stability controller 2 includes: the system comprises a system total braking feedback demand torque calculation module, a front axle stability expected feedback torque calculation module, a front and rear axle braking feedback demand torque calculation module, a front and rear axle braking demand torque calculation module and a front and rear axle mechanical braking demand torque calculation module. Preferably, an acceleration sensor is further built in the vehicle body stability controller 2. Specifically, the functions of the calculation modules of the vehicle body stability controller 2 are as follows:
the system total braking feedback demand torque calculation module is used for calculating the total braking demand torque of the driver according to the vehicle speed and the position of the brake pedal in combination with the vehicle weight, wherein the total braking feedback demand torque of the system is MAX (the system can absorb the braking feedback torque and the total braking demand torque of the driver);
the front axle stability expected feedback torque calculation module is used for calculating the minimum braking torque ratio of the front axle according to the vehicle speed and the steering wheel angle, and the front axle stability expected feedback torque is equal to the total braking feedback demand torque of the system multiplied by the minimum braking torque ratio of the front axle;
the front axle and rear axle braking feedback required torque calculation module is used for calculating front axle braking feedback required torque and calculating rear axle braking feedback required torque, the front axle braking feedback required torque is MAX { MIN (front axle stability expected feedback torque, front axle economy expected feedback torque), the front axle motor can generate the torque at present }, the rear axle braking feedback required torque is MAX { front axle braking feedback required torque x (1-front axle minimum braking torque ratio)/front axle minimum braking torque ratio, and the rear axle motor can generate the torque at present };
the front axle and rear axle braking demand torque calculation module is used for calculating front axle and rear axle braking demand torque, and the front axle braking demand torque is equal to the ratio of the total braking demand torque of the driver and the minimum braking torque of the front axle; rear axle brake demand torque ═ driver total brake demand torque × (1 — front axle minimum brake torque ratio);
the front axle and rear axle mechanical braking demand torque calculation module is used for calculating front axle and rear axle mechanical braking demand torque, and the front axle mechanical braking demand torque is front axle braking demand torque-actual braking feedback torque fed back by a front axle driving system; and the rear axle mechanical braking demand torque is equal to the rear axle braking demand torque-the actual braking feedback torque fed back by the rear axle driving system.
The steering wheel angle sensor 3 is used for collecting a steering wheel angle and sending a steering wheel angle signal to the vehicle body stability controller 2.
The wheel speed sensors 4 are used for respectively acquiring the rotating speeds of the four wheels and sending the rotating speed signals of the four wheels to the vehicle body stability controller 2 so as to convert the rotating speeds into vehicle speeds and the speeds of the four wheels; in the present embodiment, each of the four wheels of the vehicle is provided with a wheel speed sensor 4, as shown in fig. 1.
The front axle driving system 5 is used for providing driving torque to a front axle when a vehicle is driven and providing braking feedback torque when the vehicle is braked; the front axle driving system 5 may be a pure electric driving system or a hybrid driving system, and may include a speed reduction or transmission mechanism as required, which may automatically calculate the maximum (driving time) and minimum (brake feedback time) output torques of the front axle driving system 5, and may estimate the actual brake feedback torque of the front axle in real time.
The rear axle driving system 6 is used for providing driving torque for a rear axle when a vehicle is driven and providing braking feedback torque when the vehicle is braked; the rear axle driving system 6 can be a pure electric driving system or a hybrid power driving system, and can include a speed reducing or changing mechanism according to requirements, which can automatically calculate the maximum (driving time) and minimum (brake feedback time) output torques of the rear axle driving system 6, and can estimate the actual brake feedback torque of the rear axle in real time.
And the power battery 7 is used for providing driving electric energy for the electric driving system when the vehicle is driven, and storing electric energy fed back by the rear axle driving system 6 and/or the front axle driving system 5 when the vehicle brakes and feeds back.
And the brake pedal position sensor 8 is used for converting the displacement or angular displacement of the brake pedal into a voltage signal, transmitting the voltage signal to the vehicle body stability controller 2, and calculating the position and the change rate of the brake pedal by the vehicle body stability controller 2.
Wherein, front axle actuating system 5 and rear axle actuating system 6 all connect in power battery 7 and all connect in automobile body stability controller 2 through driving system control unit 1, and steering wheel corner sensor 3, wheel speed sensor 4 and brake pedal position sensor 8 all connect in automobile body stability controller 2.
It should be noted that, in the present embodiment, the vehicle body stability controller 2 integrates a brake feedback control function, and intervenes in the power system as needed in the vehicle body stability control process, specifically, the intervention process is to send an intervention request to the power system control unit 1, and the power system control unit 1 respectively adjusts the output torque of the front and rear axle drive systems to respond to the intervention requirement of the vehicle body stability controller 2. The ESC in the scheme can calculate the total braking demand torque of a driver according to the vehicle speed, the position and the change rate of a brake pedal and the preset vehicle weight, can also collect voltage signals of four wheel speed sensors 4 and convert the voltage signals into wheel speeds and vehicle speeds, simultaneously monitors the posture of the vehicle body, judges whether the posture of the vehicle body is in the optimal stable state by combining a steering wheel corner, the vehicle speed, the wheel speeds and a built-in acceleration sensor thereof, and calculates the front and rear axle braking torque proportion for maintaining the optimal stability of the vehicle body according to the axial load (preset) of front and rear axles of the vehicle, the acceleration of the vehicle, the steering wheel corner and other.
Referring to fig. 2, fig. 2 is a flow chart illustrating a brake feedback torque distribution method according to an embodiment of the invention. The invention also provides a brake feedback torque distribution method of the new energy automobile, which comprises the following steps:
s1: the computing system can absorb the brake feedback torque, and the system can absorb the brake feedback torque which is the brake feedback power which can be absorbed by the system/(the efficiency of the motor system multiplied by the efficiency of the transmission system multiplied by 9550/wheel speed, wherein the brake feedback power which can be absorbed by the system is the total consumed power of the high-voltage load and the chargeable power of the power battery. The execution main body of the step is a power system control unit 1, the power system control unit 1 firstly calculates the brake feedback power which can be absorbed by the system, and then converts the brake feedback power which can be absorbed by the system into brake feedback torque which can be absorbed by the system by combining the average wheel speed of four wheels, the efficiency of a motor system (the conversion efficiency of electric power of a motor inverter to mechanical power of a motor shaft end) and the efficiency of a transmission system (note: the driving torque/power is positive, and the feedback torque/power is negative).
The system absorbable brake feedback power refers to total electric power (including high-voltage load consumption and power battery charging) which can be consumed by the high-voltage system.
The total power consumption of the high-voltage load refers to the capability of the load to consume high voltage, and the calculation method of the total power consumption of the high-voltage load includes but is not limited to: each high-voltage distributed component multiplies a self-collected physical signal, such as current and voltage, to obtain respective power, and the power system control unit 1 adds the power reported by each high-voltage distributed component, or the power system control unit 1 multiplies the current reported by each distributed component by the total voltage of the high-voltage system to obtain the power.
The chargeable power of the power battery refers to the capacity of the power battery to absorb the maximum electric energy, and the calculation method of the chargeable power of the power battery includes but is not limited to: the power battery management system is obtained by table look-up calculation by adopting collected physical signals and estimated signals, including cell voltage, module temperature and the like, and combining with a pre-built data table (a data table established based on battery chemical characteristics).
S2: the vehicle body stability controller 2 calculates the total braking required torque of the driver according to the vehicle speed and the position of the brake pedal and the vehicle weight, and the total braking required torque of the system is MAX (the system can absorb the braking feedback torque and the total braking required torque of the driver).
The system total braking feedback required torque refers to the braking required torque which needs to be actually fed back after the driver total braking required torque and the braking feedback torque which can be absorbed by the system are comprehensively considered. In the development stage, an algorithm based on the relation between the vehicle speed, the position of a brake pedal, the vehicle weight (a fixed value after the development is finished) and the total braking demand torque of the driver is built in software of the vehicle body stability controller 2, and when the driver brakes, the vehicle body stability controller 2 obtains the real-time total braking demand torque of the driver according to the current real-time vehicle speed and the position of the brake pedal by looking up a table.
S3: calculating a front axle stability expected feedback torque, and calculating a front axle minimum braking torque ratio (a ratio of the front axle braking torque to the total braking torque based on stability expected) by the vehicle body stability controller 2 according to the vehicle speed and the steering wheel angle, wherein the front axle stability expected feedback torque is the system total braking feedback demand torque multiplied by the front axle minimum braking torque ratio;
s4: calculating the expected feedback torque of the front axle economy, establishing a expected torque MAP of the front axle economy by integrating efficiency characteristic curves of a front bridge and a rear bridge by the control unit 1 of the power system, and searching the expected torque MAP of the front axle economy by using the total braking feedback required torque of the system to obtain the expected feedback torque of the front axle economy. According to the characteristics of the generating efficiency of the front axle motor, a curve which can enable the comprehensive efficiency of the braking feedback of the system to be optimal is artificially selected on a motor efficiency curve (the horizontal axis is torque and the vertical axis is efficiency), and the curve is called as the economic expected torque MAP of the front axle. As shown in fig. 3, the external characteristic curve of the motor is a curve of maximum power or maximum torque that can be output by the motor in the current state (the power supply voltage in fig. 3 is 330V) as a function of the rotation speed, and the horizontal axis in fig. 3 represents the rotation speed (rpm) of the motor, the left-side vertical axis represents the output torque (Nm) of the motor, and the right-side vertical axis represents the output power (kW) of the motor; during the project, according to the tested curve and the common working points of the vehicle, the designer can select the optimal efficiency curve to form the final expected torque curve. And searching a corresponding inflection point according to the final expected torque curve and the current motor rotating speed, wherein the inflection point (92.98kW) is shown as the position of the circle in the figure 3 and is an optimal point manually selected to ensure that the efficiency of the whole vehicle is optimal.
S5: the vehicle body stability controller 2 calculates a front axle brake feedback request torque, which is MAX { MIN (a front axle stability expected feedback torque, a front axle economy expected feedback torque), and a current power generation torque of a front axle motor }. The front axle brake feedback demand torque refers to brake feedback demand torque which is distributed to a front axle driving system to execute; the current generatable torque of the front axle motor refers to the maximum capacity of a front axle motor system capable of converting mechanical energy of a front axle driving system into electric energy capable of being stored by a power battery, and a specific algorithm is an algorithm which is arranged in a motor controller and is set based on motor characteristics. In this step, it is mainly considered that the brake feedback torque distributed to the front axle should satisfy the following three conditions: 1. should not be less than the stability-considered torque limit (the front axle stability desired feedback torque calculated in step S3); 2. should not be less than the torque limit based on economic considerations (the front axle economic expected regenerative torque calculated in step S4); 3. the brake feedback capability of the motor itself should not be exceeded.
S6: the vehicle body stability controller 2 calculates the rear axle brake feedback required torque, wherein the rear axle brake feedback required torque is MAX (front axle brake feedback required torque x (1-front axle minimum brake torque ratio)/front axle minimum brake torque ratio, and the current power generation torque of a rear axle motor);
s7: the vehicle body stability controller 2 calculates the front axle and rear axle braking demand torque, and the front axle braking demand torque is equal to the ratio of the driver total braking demand torque multiplied by the front axle minimum braking torque; rear axle brake demand torque ═ driver total brake demand torque × (1 — front axle minimum brake torque ratio). The front axle braking demand torque is formed by the front axle mechanical braking demand torque and the front axle braking feedback demand torque; the driver total braking demand torque is the total braking torque that the driver expects the front and rear axles to provide, and the front axle braking demand torque is the braking demand torque that the system allocates to the front axle, i.e., the proportion of the front axle braking demand torque to the driver total braking demand torque (which is obtained through simulation and testing based on vehicle stability), the front axle braking demand torque is subtracted from the driver total braking demand torque, and the remainder is the rear axle braking demand torque.
S8: the vehicle body stability controller 2 calculates the front and rear axle mechanical braking demand torque, and the front axle mechanical braking demand torque is front axle braking demand torque-actual braking feedback torque fed back by a front axle driving system; and the rear axle mechanical braking demand torque is equal to the rear axle braking demand torque-the actual braking feedback torque fed back by the rear axle driving system. The front axle mechanical braking demand torque refers to torque at which the front axle provides vehicle deceleration through a mechanical system. The actual braking feedback torque fed back by the front axle driving system is the torque fed back by the motor at the wheel end of the vehicle through the actual braking of the motor obtained by monitoring the state of the motor in the braking feedback process of the motor system. In the braking process, a mechanical braking system and an electric braking system (namely a driving motor system) jointly provide braking torque to meet the requirement of a driver on wheel end braking torque, and the electric braking system provides braking feedback torque preferentially in the mechanical braking torque and the electric braking torque, if the braking requirement of the driver cannot be met, the mechanical braking system compensates the braking torque to finally meet the requirement of the driver on total braking torque.
The brake feedback torque distribution method of the new energy automobile can calculate the total brake demand torque of a driver, judge whether the posture of the automobile body is in the optimal stable state or not and calculate the front axle and rear axle brake torque proportion maintaining the optimal stability of the automobile body. The method can well coordinate the management of electric energy, the stability of the vehicle and the electric driving system capacity of the front axle and the rear axle, reasonably distribute the feedback torque between the front axle and the rear axle and exert good potential of the system. The method is suitable for hybrid four-wheel drive vehicles with completely decoupled independent power source configurations at the front and rear axles.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (4)
1. A brake feedback torque distribution method of a new energy automobile is characterized by comprising the following steps:
the computing system can absorb the brake feedback torque, and the system can absorb the brake feedback torque which is the absorbable brake feedback power of the system/(the efficiency of the motor system multiplied by the efficiency of the transmission system) multiplied by 9550/wheel speed, wherein the absorbable brake feedback power of the system is the total consumed power of the high-voltage load and the chargeable power of the power battery;
calculating the total braking feedback demand torque of the system, and calculating the total braking demand torque of the driver according to the vehicle speed and the position of the brake pedal in combination with the vehicle weight, wherein the total braking feedback demand torque of the system is MAX (the system can absorb the braking feedback torque and the total braking demand torque of the driver);
calculating the expected feedback torque of the stability of the front axle, and calculating the minimum brake torque ratio of the front axle according to the vehicle speed and the steering wheel angle, wherein the expected feedback torque of the stability of the front axle is the total brake feedback demand torque of the system multiplied by the minimum brake torque ratio of the front axle;
calculating the economic expected feedback torque of the front axle, establishing an economic expected torque MAP of the front axle by integrating efficiency characteristics of the front axle and the rear axle, and searching the economic expected torque MAP of the front axle by using the total braking feedback required torque of the system to obtain the economic expected feedback torque of the front axle;
calculating the front axle braking feedback required torque, wherein the front axle braking feedback required torque is MAX { MIN (front axle stability expected feedback torque, front axle economy expected feedback torque), and the current generating torque of a front axle motor };
calculating the rear axle braking feedback required torque, wherein the rear axle braking feedback required torque is MAX (front axle braking feedback required torque x (1-front axle minimum braking torque ratio)/front axle minimum braking torque ratio, and the current power generation torque of a rear axle motor);
calculating the required braking torque of the front axle and the rear axle, wherein the required braking torque of the front axle is equal to the ratio of the total braking required torque of a driver to the minimum braking torque of the front axle; rear axle brake demand torque ═ driver total brake demand torque × (1 — front axle minimum brake torque ratio);
calculating the mechanical braking required torque of the front axle and the rear axle, wherein the mechanical braking required torque of the front axle is equal to the braking required torque of the front axle-the actual braking feedback torque fed back by a front axle driving system; and the rear axle mechanical braking demand torque is equal to the rear axle braking demand torque-the actual braking feedback torque fed back by the rear axle driving system.
2. The utility model provides a four-wheel drive control system of new energy automobile which characterized in that includes: a power system control unit, a vehicle body stability controller, a steering wheel corner sensor, a wheel speed sensor, a front axle driving system, a rear axle driving system, a power battery and a brake pedal position sensor,
the power system control unit is used for calculating the absorbable brake feedback torque of the system, wherein the absorbable brake feedback torque of the system is the absorbable brake feedback power of the system/(the efficiency of a motor system multiplied by the efficiency of a transmission system multiplied by 9550 per wheel speed, and the absorbable brake feedback power of the system is the total consumed power of a high-voltage load and the chargeable power of the power battery; the power system control unit is also used for calculating the front axle economical expected feedback torque, establishing a front axle economical expected torque MAP by integrating the efficiency characteristics of a front electric bridge and a rear electric bridge, and searching the front axle economical expected torque MAP by using the total braking feedback required torque of the system to obtain the front axle economical expected feedback torque;
the vehicle body stability controller includes: a system total braking feedback demand torque calculation module, a front axle stability expected feedback torque calculation module, a front and rear axle braking feedback demand torque calculation module, a front and rear axle braking demand torque calculation module, a front and rear axle mechanical braking demand torque calculation module, wherein,
the system total braking feedback demand torque calculation module is used for calculating the total braking demand torque of a driver according to the vehicle speed and the position of a brake pedal in combination with the vehicle weight, wherein the total braking feedback demand torque of the system is MAX (the system can absorb the braking feedback torque and the total braking demand torque of the driver);
the front axle stability expected feedback torque calculation module is used for calculating the minimum braking torque ratio of the front axle according to the vehicle speed and the steering wheel angle, and the front axle stability expected feedback torque is equal to the total braking feedback demand torque of the system multiplied by the minimum braking torque ratio of the front axle;
the front axle and rear axle braking feedback demand torque calculation module is used for calculating front axle braking feedback demand torque and calculating rear axle braking feedback demand torque, the front axle braking feedback demand torque is MAX { MIN (feedback torque is expected for front axle stability and feedback torque is expected for front axle economy), the front axle motor can generate current torque }, the rear axle braking feedback demand torque is MAX { front axle braking feedback demand torque is x (1-front axle minimum braking torque ratio)/front axle minimum braking torque ratio, and the rear axle motor can generate current torque };
the front axle and rear axle braking demand torque calculation module is used for calculating front axle and rear axle braking demand torque, and the front axle braking demand torque is the ratio of the total braking demand torque of the driver and the minimum braking torque of the front axle; rear axle brake demand torque ═ driver total brake demand torque × (1 — front axle minimum brake torque ratio);
the front axle and rear axle mechanical braking demand torque calculation module is used for calculating front axle and rear axle mechanical braking demand torque, and the front axle mechanical braking demand torque is front axle braking demand torque-actual braking feedback torque fed back by a front axle driving system; the rear axle mechanical braking demand torque is rear axle braking demand torque-actual braking feedback torque fed back by a rear axle driving system;
the steering wheel corner sensor is used for collecting a steering wheel corner and sending a steering wheel corner signal to the vehicle body stability controller;
the wheel speed sensors are used for respectively acquiring the rotating speeds of four wheels and sending four-wheel rotating speed signals to the vehicle body stability controller so as to convert the four-wheel rotating speed signals into vehicle speed and four-wheel speeds;
the front axle driving system is used for providing driving torque to a front axle when a vehicle is driven and providing braking feedback torque when the vehicle is braked;
the rear axle driving system is used for providing driving torque for a rear axle when a vehicle is driven and providing braking feedback torque when the vehicle is braked;
the power battery is used for providing driving electric energy for the electric driving system when the vehicle is driven, and the electric energy fed back by the rear axle driving system and/or the front axle driving system can be stored when the vehicle is braked and fed back;
the brake pedal position sensor is used for converting the displacement of a brake pedal into a voltage signal and transmitting the voltage signal to the vehicle body stability controller;
the front axle driving system and the rear axle driving system are connected with the power battery and are connected with the vehicle body stability controller through the power system control unit, and the steering wheel corner sensor, the wheel speed sensor and the brake pedal position sensor are connected with the vehicle body stability controller.
3. The four-wheel drive control system of the new energy automobile as claimed in claim 2, wherein the power system control unit is integrated in a vehicle control unit.
4. The four-wheel drive control system of the new energy automobile as claimed in claim 2, wherein an acceleration sensor is built in the body stability controller.
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| CN112622642A (en) * | 2021-01-07 | 2021-04-09 | 北京车和家信息技术有限公司 | Torque control method and device for four-wheel drive electric automobile and vehicle |
| CN113415175B (en) * | 2021-07-12 | 2022-10-11 | 重庆长安汽车股份有限公司 | Method for estimating maximum available torque of whole pure electric four-wheel drive vehicle |
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