CN113459817A - Braking energy recovery control method and system based on wheel hub motor vehicle - Google Patents
Braking energy recovery control method and system based on wheel hub motor vehicle Download PDFInfo
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- CN113459817A CN113459817A CN202110534034.9A CN202110534034A CN113459817A CN 113459817 A CN113459817 A CN 113459817A CN 202110534034 A CN202110534034 A CN 202110534034A CN 113459817 A CN113459817 A CN 113459817A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L7/00—Electrodynamic brake systems for vehicles in general
- B60L7/10—Dynamic electric regenerative braking
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L7/00—Electrodynamic brake systems for vehicles in general
- B60L7/10—Dynamic electric regenerative braking
- B60L7/18—Controlling the braking effect
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/72—Electric energy management in electromobility
Abstract
The invention discloses a braking energy recovery control method and system based on a wheel hub motor vehicle, relating to the field of braking energy recovery, and the method comprises the following steps: determining total braking torque according to the opening degree of a brake pedal; determining the braking torque required by the single front wheel and the single rear wheel based on the total braking torque and the ideal braking force distribution curve; after the energy recovery mode is judged, respectively determining the single-motor electric braking demand torque of the front axle and the single-motor electric braking demand torque of the rear axle according to the braking torque and the opening degree of a braking pedal required by a single front wheel and a single rear wheel; and determining the output torque distributed to the front axle single motor brake, the output torque of the rear axle single motor brake and the target hydraulic pressure of the electronic hydraulic booster according to the front axle single motor electric brake demand torque, the rear axle single motor electric brake demand torque and the current maximum output negative torque of the front axle motor. The braking energy recovery control method based on the wheel hub motor vehicle can greatly reduce energy loss and improve the energy recovery utilization rate.
Description
Technical Field
The invention relates to the field of braking energy recovery, in particular to a braking energy recovery control method and system based on a wheel hub motor vehicle.
Background
The hub motor is designed by integrating a power system, a transmission system and a brake system of a vehicle. The hub motor drive is to directly install the driving motor in the driving wheel, is a novel driving arrangement form for solving the power and power efficiency of the automobile, has the outstanding advantages of short driving transmission chain, high transmission efficiency, compact structure, quick response and the like, and is an important direction for the development of the future electric vehicle.
The electric automobile has many advantages in the aspects of energy conservation, environmental protection, vehicle performance improvement and the like, but the driving range of the electric automobile charged once is generally short, and the insufficient driving range charged once is a main problem which restricts the further development of the electric automobile. The four-wheel drive electric automobile adopting the hub motor can reduce energy loss during driving and braking energy recovery.
The braking energy usually occupies a larger proportion in the total driving energy of the whole vehicle, the proportion is even up to 50% under the urban road working condition of frequent acceleration, braking and parking, and the driving range of the whole vehicle can be increased by 20% -30% by adopting a reasonable braking energy recovery strategy. The regenerative braking is used for recovering the braking energy, so that the significance of improving the energy utilization rate and increasing the driving range of the electric automobile is very important, and the regenerative braking is an important technical means for improving the performance of the electric automobile. However, an efficient braking energy recovery control strategy is not available at present to improve the driving range of the vehicle.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a braking energy recovery control method based on an in-wheel motor vehicle, which can greatly reduce energy loss and improve the energy recovery utilization rate.
In order to achieve the above purposes, the technical scheme adopted by the invention is as follows:
a braking energy recovery control method based on an in-wheel motor vehicle comprises the following steps:
determining total braking torque according to the opening degree of a brake pedal;
determining the braking torque required by the single front wheel and the single rear wheel based on the total braking torque and the ideal braking force distribution curve;
after the energy recovery mode is judged, respectively determining the single-motor electric braking demand torque of the front axle and the single-motor electric braking demand torque of the rear axle according to the braking torque and the opening degree of a braking pedal required by a single front wheel and a single rear wheel;
and determining the output torque distributed to the front axle single motor brake, the output torque of the rear axle single motor brake and the target hydraulic pressure of the electronic hydraulic booster according to the front axle single motor electric brake demand torque, the rear axle single motor electric brake demand torque and the current maximum output negative torque of the front axle motor.
In some embodiments, the determining the total braking torque according to the opening degree of the brake pedal includes:
determining a target deceleration under the current brake pedal opening degree according to the brake pedal opening degree;
and calculating the total braking torque according to the mass of the whole vehicle, the gravity acceleration, the rolling radius of the wheels and the target deceleration.
In some embodiments, said determining the braking torque required for the single front wheel and the single rear wheel based on the total braking torque and the ideal braking force distribution curve comprises:
respectively determining the axle load of a front axle and the axle load of a rear axle based on the total braking torque and the ideal braking force distribution curve;
calculating the front and rear axle braking torque distribution ratio according to the front axle load and the rear axle load;
and calculating the braking torque required by the single front wheel and the single rear wheel according to the total braking torque and the distribution ratio of the braking torque of the front axle and the rear axle.
In some embodiments, after the determining that the energy recovery mode is entered, determining the single-motor electro-mechanical braking demand torque for the front axle and the single-motor electro-mechanical braking demand torque for the rear axle according to the braking torque and the opening degree of the brake pedal required for the single front wheel and the single rear wheel respectively includes:
when the opening degree of the brake pedal does not exceed a preset value, the counter torques of the braking torques required by the single front wheel and the single rear wheel are respectively used as the required torque of the single-motor electromechanical braking of the front axle and the required torque of the single-motor electromechanical braking of the rear axle;
when the opening degree of the brake pedal exceeds a preset value, the counter torque after the influence of the overflow pressure of the electronic hydraulic booster is removed by the braking torque required by a single front wheel and a single rear wheel is respectively used as the required torque of the single-motor electric brake of the front axle and the required torque of the single-motor electric brake of the rear axle.
In some embodiments, the determining the output torque allocated to the front axle single motor brake, the output torque of the rear axle single motor brake, and the target hydraulic pressure of the electro-hydraulic booster based on the front axle single motor electro-mechanical brake demand torque, the rear axle single electro-mechanical brake demand torque, and the current maximum output negative torque of the front axle motor includes:
when the current maximum output negative torque of a front shaft motor is smaller than the electric braking demand torque of a front shaft single motor, the output torque of the front shaft single motor braking is the electric braking demand torque of the front shaft single motor, the output torque of the rear shaft single motor braking is the electric braking demand torque of the rear shaft single motor, and the target hydraulic pressure of the electronic hydraulic booster is the overflow pressure of the electronic hydraulic booster;
when the current maximum output negative torque of the front shaft motor is larger than or equal to the current maximum output negative torque of the front shaft single motor electric braking demand torque, the output torque of the front shaft single motor electric braking is the current maximum output negative torque of the front shaft motor, the output torque of the rear shaft single motor electric braking demand torque is the rear shaft single motor electric braking demand torque, and the target hydraulic force of the electronic hydraulic booster is determined based on the overflow pressure of the electronic hydraulic booster, the current maximum output negative torque of the front shaft motor and the front shaft single motor electric braking demand torque.
Meanwhile, the invention provides a braking energy recovery control system based on the wheel hub motor vehicle, which can greatly reduce energy loss and improve the energy recovery utilization rate.
In order to achieve the above purposes, the technical scheme adopted by the invention is as follows:
a braking energy recovery control system based on an in-wheel motor vehicle comprises:
the braking force calculation module is used for determining total braking torque according to the opening degree of a brake pedal;
a braking force distribution module for determining braking torques required for the individual front and rear wheels based on the total braking torque and the ideal braking force distribution curve;
the electro-hydraulic brake distribution module is used for determining the braking torque and the braking pedal opening degree required by a single front wheel and a single rear wheel and respectively determining the front axle single-motor electro-mechanical braking demand torque and the rear axle single-motor electro-mechanical braking demand torque after judging that the energy recovery mode is entered;
and determining the output torque distributed to the front axle single motor brake, the output torque of the rear axle single motor brake and the target hydraulic pressure of the electronic hydraulic booster according to the front axle single motor electric brake demand torque, the rear axle single motor electric brake demand torque and the current maximum output negative torque of the front axle motor.
In some embodiments, the braking force calculation module is to:
determining a target deceleration under the current brake pedal opening degree according to the brake pedal opening degree;
and calculating the total braking torque according to the mass of the whole vehicle, the gravity acceleration, the rolling radius of the wheels and the target deceleration.
In some embodiments, the braking force distribution module is to:
respectively determining the axle load of a front axle and the axle load of a rear axle based on the total braking torque and the ideal braking force distribution curve;
calculating the front and rear axle braking torque distribution ratio according to the front axle load and the rear axle load;
and calculating the braking torque required by the single front wheel and the single rear wheel according to the total braking torque and the distribution ratio of the braking torque of the front axle and the rear axle.
In some embodiments, the electro-hydraulic brake distribution module is to:
when the opening degree of the brake pedal does not exceed a preset value, the counter torques of the braking torques required by the single front wheel and the single rear wheel are respectively used as the required torque of the single-motor electromechanical braking of the front axle and the required torque of the single-motor electromechanical braking of the rear axle;
when the opening degree of the brake pedal exceeds a preset value, the counter torque after the influence of the overflow pressure of the electronic hydraulic booster is removed by the braking torque required by a single front wheel and a single rear wheel is respectively used as the required torque of the single-motor electric brake of the front axle and the required torque of the single-motor electric brake of the rear axle.
In some embodiments, the electro-hydraulic brake distribution module is further configured to:
when the current maximum output negative torque of a front shaft motor is smaller than the electric braking demand torque of a front shaft single motor, the output torque of the front shaft single motor braking is the electric braking demand torque of the front shaft single motor, the output torque of the rear shaft single motor braking is the electric braking demand torque of the rear shaft single motor, and the target hydraulic pressure of the electronic hydraulic booster is the overflow pressure of the electronic hydraulic booster;
when the current maximum output negative torque of the front shaft motor is larger than or equal to the current maximum output negative torque of the front shaft single motor electric braking demand torque, the output torque of the front shaft single motor electric braking is the current maximum output negative torque of the front shaft motor, the output torque of the rear shaft single motor electric braking demand torque is the rear shaft single motor electric braking demand torque, and the target hydraulic force of the electronic hydraulic booster is determined based on the overflow pressure of the electronic hydraulic booster, the current maximum output negative torque of the front shaft motor and the front shaft single motor electric braking demand torque.
Compared with the prior art, the invention has the advantages that:
according to the braking energy recovery control method based on the wheel hub motor vehicle, the braking force of the front axle and the braking force of the rear axle are distributed in an ideal braking force distribution mode during braking, so that the braking stability of the vehicle is greatly improved; meanwhile, regenerative braking is preferred during braking, and energy recovery is carried out by preferentially utilizing motor braking on the premise that the braking requirement can be met, so that the driving range of the vehicle is greatly increased; the brake feeling can be adjusted according to different drivers; in addition, this scheme is based on in-wheel motor platform, because in-wheel motor does not have the transmission shaft and the response is quick, can reduce energy loss by a wide margin when electric braking, improves energy recuperation utilization ratio.
Drawings
FIG. 1 is a flow chart of a braking energy recovery control method for a vehicle based on an in-wheel motor according to an embodiment of the present invention;
FIG. 2 is a block diagram of a braking energy recovery control system of a vehicle based on an in-wheel motor according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all 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 application.
Referring to fig. 1, an embodiment of the present invention provides a braking energy recovery control method for an in-wheel motor vehicle, including the following steps:
s1, determining total braking torque according to the opening degree of a brake pedal.
In a specific implementation, step S1 includes:
s11, determining a target deceleration degree under the current brake pedal opening degree according to the brake pedal opening degree.
And S12, calculating the total braking torque according to the mass of the whole vehicle, the gravity acceleration, the rolling radius of the wheels and the target deceleration.
Specifically, during driving, when the driver depresses the brake pedal, the vehicle controller looks up a table (brake pedal percentage-target deceleration table) according to the obtained driver opening percentage to obtain the target deceleration A expected by the driverxIt is worth mentioning that the brake pedal percentage-target deceleration table can be reasonably set according to the driver's demand. The total braking torque T can then be calculated according to the following formulatot：
Ttot＝Ax*M*g*R
Wherein M is the vehicle mass, g is the gravity acceleration, and R is the rolling radius of the wheels.
And S2, determining the braking torque required by the single front wheel and the single rear wheel based on the total braking torque and the ideal braking force distribution curve.
And after the total braking torque is determined, the front and rear axle braking force distribution can be carried out on the total braking torque by adopting an ideal braking force distribution mode.
In a specific implementation, step S2 includes:
and S21, respectively determining the axle load of the front axle and the axle load of the rear axle based on the total braking torque and the ideal braking force distribution curve.
In order to ensure the stability during braking, the braking force distribution of the front axle and the rear axle is carried out according to an ideal braking force distribution curve, and the axle load of the front axle and the axle load of the rear axle during braking can be expressed as follows:
wherein M is the vehicle mass, g is the gravity acceleration, a is the distance from the center of mass to the front axle, b is the distance from the center of mass to the rear axle, L is the axle distance, h is the height of the center of mass, axThe real-time braking deceleration of the vehicle is measured by a gyroscope chip of the vehicle control unit.
S22, calculating the braking torque distribution ratio of the front axle and the rear axle according to the axle load of the front axle and the axle load of the rear axle.
Based on the determined axle load of the front axle and the axle load of the rear axle, the distribution ratio of the braking torque of the front axle and the braking torque of the rear axle is as follows:
and S23, calculating the braking torque required by the single front wheel and the single rear wheel according to the total braking torque and the front and rear axle braking torque distribution ratio.
From the front-rear axle braking torque distribution ratio β obtained in step S22, it can be calculated that the braking torques distributed to the front and rear axles are:
wherein T isf_totBraking torque, T, allocated to the front axler_totA braking torque distributed to the rear axle.
The braking torque required by the single front wheel is further calculated as follows:
the braking torque required for a single rear wheel is:
because there are two front wheels on the front axle and two rear wheels on the rear axle, it can be understood that the braking torques required for the two front wheels are the same and the braking torques required for the two rear wheels are the same based on the above expression, but of course, they can be reasonably distributed according to actual situations, so that the braking torques required between the two front wheels and between the two rear wheels are different.
And S3, after the energy recovery mode is judged, respectively determining the front axle single-motor electric braking demand torque and the rear axle single-motor electric braking demand torque according to the braking torque and the braking pedal opening degree required by a single front wheel and a single rear wheel.
In a specific implementation, step S3 includes:
and S31, when the opening degree of the brake pedal does not exceed a preset value, taking the counter torque of the braking torque required by the single front wheel and the single rear wheel as the front axle single motor electric braking demand torque and the rear axle single motor electric braking demand torque respectively.
And S32, when the opening degree of the brake pedal exceeds a preset value, removing counter torque influenced by overflow pressure of the electronic hydraulic booster by using the braking torque required by a single front wheel and a single rear wheel, and respectively using the counter torque as the required torque of the single-motor electric brake of the front axle and the required torque of the single-motor electric brake of the rear axle.
Specifically, the electro-hydraulic brakes may be distributed when the braking torque required for a single front and rear wheel is determined. Firstly, judging the vehicle speed and the battery SOC, if the battery SOC is more than 95 percent or the vehicle speed is less than 10km/h, entering a pure hydraulic braking mode, obtaining a target hydraulic pressure through table look-up (percentage of a brake pedal-target hydraulic pressure gauge), and sending the target hydraulic pressure to an electronic hydraulic booster to realize braking; and entering an energy recovery mode only when the SOC is less than 95% and the vehicle speed is higher than 10 km/h.
After entering the energy recovery mode, based on the hardware characteristics of the electronic hydraulic booster, a decoupling gap exists in the brake master cylinder, and when the stroke of the brake pedal exceeds a preset value, for example, exceeds 0.23, hydraulic pressure overflows. Therefore, when the brake pedal opening is less than 0.23, Tf1＝-Tf_one，Tf2＝-Tr_one(ii) a When the opening degree of the brake pedal is larger than 0.23, Tf1＝-(Tf_one-a*Pmin)，Tf2＝-(Tr_one-a*Pmin) (ii) a In the formula Tf1For a front axle single motor electric braking demand torque, Tf2The torque required for the single-motor electric braking of the rear axle, a is the conversion coefficient between the target hydraulic pressure and the braking force of the tire, PminIs the electronic hydraulic booster spill pressure.
And S4, determining the output torque distributed to the braking of the front axle single motor, the output torque of the braking of the rear axle single motor and the target hydraulic force of the electronic hydraulic booster according to the front axle single motor electric braking demand torque, the rear axle single motor electric braking demand torque and the current maximum output negative torque of the front axle motor.
In a specific implementation, step S4 includes:
s41, when the current maximum output negative torque of the front axle motor is smaller than the required torque of the front axle single motor electric braking, the output torque of the front axle single motor electric braking is the required torque of the front axle single motor electric braking, the output torque of the rear axle single motor electric braking is the required torque of the rear axle single motor electric braking, and the target hydraulic pressure of the electronic hydraulic booster is the overflow pressure of the electronic hydraulic booster.
And S42, when the current maximum output negative torque of the front shaft motor is larger than or equal to the braking demand torque of the front shaft single motor, the braking output torque of the front shaft single motor is the current maximum output negative torque of the front shaft motor, the braking output torque of the rear shaft single motor is the braking demand torque of the rear shaft single motor, and the target hydraulic pressure of the electronic hydraulic booster is determined based on the overflow pressure of the electronic hydraulic booster, the current maximum output negative torque of the front shaft motor and the braking demand torque of the front shaft single motor.
Specifically, the front axle single-motor electromechanical braking demand torque and the rear axle single-motor electromechanical braking demand torque obtained through the decision in step S3 need to be distributed to four motors, which is restricted by the torque output capability of the motors. The motor can only send out fixed maximum reverse torque under a certain rotating speed limited by external characteristics, so the braking energy recovery needs to be dynamically adjusted according to the working point of the motor.
Firstly, according to the current rotating speed of motor a table (motor external characteristic curve table) is looked up to obtain the current maximum output negative torque T of front axle motorf_max(when braking, the moment required by the front axle is large, and only need to check whether the capacity of the front axle motor is enough under the same rotating speed), if Tf_max＜Tf1，Tf_out＝Tf1， Tr_out＝Tf2，Pout＝Pmin(ii) a If T isf_max≥Tf1，Tf_out＝Tf_max，Tr_out＝Tf2， 
In the formula Tf_outThe output torque is the braking output torque of the front axle single motor; t isr_outAnd the torque is output for the single-motor braking of the rear axle. PoutIs the actual target hydraulic pressure sent to the electronic hydraulic booster. And finally, the vehicle control unit distributes the determined target hydraulic pressure and the electric braking output torque to the electronic hydraulic booster and the corresponding wheel hub motor controller respectively, so that the braking energy recovery is realized.
In conclusion, the braking energy recovery control method based on the wheel hub motor vehicle adopts an ideal braking force distribution mode to distribute the braking force of the front axle and the braking force of the rear axle during braking, so that the braking stability of the vehicle is greatly improved; meanwhile, regenerative braking is prior during braking, and energy recovery is performed by preferentially utilizing motor braking on the premise of meeting the braking requirement, so that the driving range of the vehicle is greatly increased; the brake feeling can be adjusted according to different drivers; in addition, this scheme is based on in-wheel motor platform, because in-wheel motor does not have the transmission shaft and the response is quick, can reduce energy loss by a wide margin when electric braking, improves energy recuperation utilization ratio.
Meanwhile, the embodiment of the invention also provides a braking energy recovery control system based on the wheel hub motor vehicle, which comprises a braking force calculation module, a braking force distribution module and an electro-hydraulic braking distribution module.
The braking force calculation module is used for determining total braking torque according to the opening degree of a brake pedal. The braking force distribution module is used for determining the braking torque required by the single front wheel and the single rear wheel based on the total braking torque and the ideal braking force distribution curve. And the electro-hydraulic brake distribution module is used for respectively determining the single-motor electro-mechanical brake demand torque of the front axle and the single-motor electro-mechanical brake demand torque of the rear axle according to the brake torque and the brake pedal separation required by the single front wheel and the single rear wheel after judging that the energy recovery mode is entered. And determining the output torque distributed to the front axle single motor brake, the output torque of the rear axle single motor brake and the target hydraulic pressure of the electronic hydraulic booster according to the front axle single motor electric brake demand torque, the rear axle single motor electric brake demand torque and the current maximum output negative torque of the front axle motor.
Further, the braking force calculation module is configured to: a target deceleration at the current brake pedal opening is determined based on the brake pedal opening. And calculating the total braking torque according to the mass of the whole vehicle, the gravity acceleration, the rolling radius of the wheels and the target deceleration.
Further, the braking force distribution module is configured to: and respectively determining the axle load of the front axle and the axle load of the rear axle based on the total braking torque and the ideal braking force distribution curve. And calculating the braking torque distribution ratio of the front axle and the rear axle according to the axle load of the front axle and the axle load of the rear axle. The braking torque required for the individual front and rear wheels is calculated from the total braking torque and the front-rear axle braking torque distribution ratio.
Further, the electro-hydraulic brake distribution module is configured to:
when the opening degree of the brake pedal does not exceed a preset value, the counter torque of the braking torque required by the single front wheel and the single rear wheel is respectively used as the required torque of the single-motor electromechanical braking of the front axle and the required torque of the single-motor electromechanical braking of the rear axle.
When the opening degree of the brake pedal exceeds a preset value, the counter torque after the influence of the overflow pressure of the electronic hydraulic booster is removed by the braking torque required by a single front wheel and a single rear wheel is respectively used as the required torque of the single-motor electric brake of the front axle and the required torque of the single-motor electric brake of the rear axle.
Further, the electro-hydraulic brake distribution module is further configured to:
when the current maximum output negative torque of the front shaft motor is smaller than the required torque of the front shaft single motor electric brake, the output torque of the front shaft single motor electric brake is the required torque of the front shaft single motor electric brake, the output torque of the rear shaft single motor electric brake is the required torque of the rear shaft single motor electric brake, and the target hydraulic pressure of the electronic hydraulic booster is the overflow pressure of the electronic hydraulic booster;
when the current maximum output negative torque of the front shaft motor is larger than or equal to the current maximum output negative torque of the front shaft single motor electric braking demand torque, the output torque of the front shaft single motor electric braking is the current maximum output negative torque of the front shaft motor, the output torque of the rear shaft single motor electric braking demand torque is the rear shaft single motor electric braking demand torque, and the target hydraulic pressure of the electronic hydraulic booster is determined based on the overflow pressure of the electronic hydraulic booster, the current maximum output negative torque of the front shaft motor and the front shaft single motor electric braking demand torque.
Referring to fig. 2, the following description is made on the principle of the braking energy recovery control system of the in-wheel motor based vehicle:
when a driver steps on a brake pedal, the vehicle control unit obtains the percentage alpha of the opening degree of the driver and carries out table look-up (percentage of the brake pedal-target deceleration table) to obtain the target deceleration A expected by the driverxThen the braking force calculation module calculates the braking force according to the formula Ttot＝AxM g R can calculate the total braking torque TtotWherein M is the mass of the whole vehicle, g is the gravity acceleration, and R is the rolling radius of the wheel.
Then the braking force distribution module carries out braking force distribution of the front axle and the rear axle according to an ideal braking force distribution curve to obtain the axle load of the front axle during braking
And rear axle load
Wherein M is the vehicle mass, g is the gravity acceleration, a is the distance from the center of mass to the front axle, b is the distance from the center of mass to the rear axle, L is the axle distance, h is the height of the center of mass, axThe real-time braking deceleration of the vehicle is measured by a gyroscope chip of the vehicle control unit. Then the braking force distribution module can calculate the braking torque distribution ratio beta of the front axle and the rear axle. Then the braking force distribution module calculates the total braking torque T based on the braking force calculation moduletotAnd the braking torque distribution ratio beta of the front axle and the rear axle can distribute the front braking force and the rear braking force to obtain the braking torque T distributed by the front axlef_totAnd the braking torque T distributed by the rear axler_tot。
After that, the electro-hydraulic brake distribution module works, and after the energy recovery mode is entered, based on the hardware characteristic of the electronic hydraulic booster, a decoupling gap exists in the brake master cylinder, and when the stroke of the brake pedal exceeds a preset value, for example, exceeds 0.23, hydraulic pressure overflows. Therefore, when the opening degree of the brake pedal is smaller than 0.23, the electro-hydraulic brake distribution module distributes so that Tf1＝-Tf_one，Tf2＝-Tr_one(ii) a When the opening degree of the brake pedal is larger than 0.23, Tf1＝-(Tf_one-a*Pmin)，Tf2＝-(Tr_one-a*Pmin) (ii) a In the formula Tf1For a front axle single motor electric braking demand torque, Tf2The torque required for the single-motor electric braking of the rear axle, a is the conversion coefficient between the target hydraulic pressure and the braking force of the tire, PminIs the electronic hydraulic booster spill pressure.
The electric braking torque obtained through the above decision needs to be distributed to four motors and is limited by the torque output capacity of the motors. The motor can only send out fixed maximum reverse torque under a certain rotating speed limited by external characteristics, so the braking energy recovery needs to be dynamically adjusted according to the working point of the motor.
Obtaining the current maximum output negative torque T of the front axle motor according to the current rotating speed look-up table (motor external characteristic curve table)f_maxIf T isf_max＜Tf1，Tf_out＝Tf1，Tr_out＝Tf2， Pout＝Pmin(ii) a If T isf_max≥Tf1，Tf_out＝Tf_max，Tr_out＝Tf2， 
In the formula Tf_outThe output torque is the braking output torque of the front axle single motor; t isr_outAnd the torque is output for the single-motor braking of the rear axle. PoutIs the actual target hydraulic pressure sent to the electronic hydraulic booster. And finally, the vehicle control unit distributes the determined target hydraulic pressure and the electric braking output torque to the electronic hydraulic booster and the corresponding wheel hub motor controller respectively, so that the braking energy recovery is realized.
In conclusion, the braking energy recovery control system based on the wheel hub motor vehicle adopts an ideal braking force distribution mode to distribute the braking force of the front axle and the braking force of the rear axle during braking, so that the braking stability of the vehicle is greatly improved; meanwhile, regenerative braking is prior during braking, and energy recovery is performed by preferentially utilizing motor braking on the premise of meeting the braking requirement, so that the driving range of the vehicle is greatly increased; the brake feeling can be adjusted according to different drivers; in addition, this scheme is based on in-wheel motor platform, because in-wheel motor does not have the transmission shaft and the response is quick, can reduce energy loss by a wide margin when electric braking, improves energy recuperation utilization ratio.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an", and/or "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the features, steps, operations, devices, components, and/or combinations thereof.
The relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters indicate like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
The present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are also considered to be within the scope of the present invention. Those not described in detail in this specification are within the skill of the art.
Claims (10)
1. A braking energy recovery control method based on an in-wheel motor vehicle is characterized by comprising the following steps:
determining total braking torque according to the opening degree of a brake pedal;
determining the braking torque required by the single front wheel and the single rear wheel based on the total braking torque and the ideal braking force distribution curve;
after the energy recovery mode is judged, respectively determining the single-motor electric braking demand torque of the front axle and the single-motor electric braking demand torque of the rear axle according to the braking torque and the opening degree of a braking pedal required by a single front wheel and a single rear wheel;
and determining the output torque distributed to the front axle single motor brake, the output torque of the rear axle single motor brake and the target hydraulic pressure of the electronic hydraulic booster according to the front axle single motor electric brake demand torque, the rear axle single motor electric brake demand torque and the current maximum output negative torque of the front axle motor.
2. The braking energy recovery control method for the in-wheel motor vehicle according to claim 1, wherein the determining the total braking torque according to the opening degree of the braking pedal comprises:
determining a target deceleration under the current brake pedal opening degree according to the brake pedal opening degree;
and calculating the total braking torque according to the mass of the whole vehicle, the gravity acceleration, the rolling radius of the wheels and the target deceleration.
3. The method of claim 1, wherein determining the braking torque required for each of the front and rear wheels based on the total braking torque and the ideal braking force distribution curve comprises:
respectively determining the axle load of a front axle and the axle load of a rear axle based on the total braking torque and the ideal braking force distribution curve;
calculating the front and rear axle braking torque distribution ratio according to the front axle load and the rear axle load;
and calculating the braking torque required by the single front wheel and the single rear wheel according to the total braking torque and the distribution ratio of the braking torque of the front axle and the rear axle.
4. The method for controlling recovery of braking energy of a vehicle based on an in-wheel motor according to claim 1, wherein after the energy recovery mode is determined, the required braking torque of the single-motor electro-mechanical brake on the front axle and the required braking torque of the single-motor electro-mechanical brake on the rear axle are respectively determined according to the braking torque and the opening degree of the braking pedal required by the single front wheel and the single rear wheel, and the method comprises the following steps:
when the opening degree of the brake pedal does not exceed a preset value, the counter torques of the braking torques required by the single front wheel and the single rear wheel are respectively used as the required torque of the single-motor electromechanical braking of the front axle and the required torque of the single-motor electromechanical braking of the rear axle;
when the opening of the brake pedal exceeds a preset value, the braking torque required by a single front wheel and a single rear wheel is used for removing the counter torque influenced by the overflow pressure of the electronic hydraulic booster, and the counter torque is respectively used as the single-motor electric braking demand torque of the front axle and the single-motor electric braking demand torque of the rear axle.
5. The braking energy recovery control method for the in-wheel motor vehicle according to claim 1, wherein the determining of the output torque allocated to the braking of the front axle single motor, the output torque of the braking of the rear axle single motor and the target hydraulic pressure of the electronic hydraulic booster according to the front axle single motor electric braking demand torque, the rear axle single motor electric braking demand torque and the current maximum output negative torque of the front axle motor comprises:
when the current maximum output negative torque of a front shaft motor is smaller than the required torque of the front shaft single motor electric braking, the output torque of the front shaft single motor electric braking is the required torque of the front shaft single motor electric braking, the output torque of the rear shaft single motor electric braking is the required torque of the rear shaft single motor electric braking, and the target hydraulic pressure of the electronic hydraulic booster is the overflow pressure of the electronic hydraulic booster;
when the current maximum output negative torque of the front shaft motor is larger than or equal to the current maximum output negative torque of the front shaft single motor electric braking demand torque, the output torque of the front shaft single motor electric braking is the current maximum output negative torque of the front shaft motor, the output torque of the rear shaft single motor electric braking demand torque is the rear shaft single motor electric braking demand torque, and the target hydraulic pressure of the electronic hydraulic booster is determined based on the overflow pressure of the electronic hydraulic booster, the current maximum output negative torque of the front shaft motor and the front shaft single motor electric braking demand torque.
6. A braking energy recovery control system based on an in-wheel motor vehicle is characterized by comprising:
the braking force calculation module is used for determining total braking torque according to the opening degree of a brake pedal;
a braking force distribution module for determining the braking torque required for a single front wheel and rear wheel based on the total braking torque and an ideal braking force distribution curve;
the electro-hydraulic brake distribution module is used for determining the braking torque and the braking pedal opening degree required by a single front wheel and a single rear wheel and respectively determining the front axle single-motor electro-mechanical braking demand torque and the rear axle single-motor electro-mechanical braking demand torque after judging that the energy recovery mode is entered;
and determining the output torque distributed to the front axle single motor brake, the output torque of the rear axle single motor brake and the target hydraulic pressure of the electronic hydraulic booster according to the front axle single motor electric brake demand torque, the rear axle single motor electric brake demand torque and the current maximum output negative torque of the front axle motor.
7. The braking energy recovery control system for an in-wheel motor vehicle according to claim 6, wherein the braking force calculation module is configured to:
determining a target deceleration under the current brake pedal opening degree according to the brake pedal opening degree;
and calculating the total braking torque according to the mass of the whole vehicle, the gravity acceleration, the rolling radius of the wheels and the target deceleration.
8. The braking energy recovery control system for an in-wheel motor vehicle according to claim 6, wherein the braking force distribution module is configured to:
respectively determining the axle load of a front axle and the axle load of a rear axle based on the total braking torque and the ideal braking force distribution curve;
calculating the front and rear axle braking torque distribution ratio according to the front axle load and the rear axle load;
and calculating the braking torque required by the single front wheel and the single rear wheel according to the total braking torque and the distribution ratio of the braking torque of the front axle and the rear axle.
9. The braking energy recovery control system for an in-wheel motor vehicle according to claim 6, wherein the electro-hydraulic brake distribution module is configured to:
when the opening degree of the brake pedal does not exceed a preset value, the counter torques of the braking torques required by the single front wheel and the single rear wheel are respectively used as the required torque of the single-motor electromechanical braking of the front axle and the required torque of the single-motor electromechanical braking of the rear axle;
when the opening of the brake pedal exceeds a preset value, the braking torque required by a single front wheel and a single rear wheel is used for removing the counter torque influenced by the overflow pressure of the electronic hydraulic booster, and the counter torque is respectively used as the single-motor electric braking demand torque of the front axle and the single-motor electric braking demand torque of the rear axle.
10. The braking energy recovery control system for an in-wheel motor vehicle according to claim 6, wherein the electro-hydraulic brake distribution module is further configured to:
when the current maximum output negative torque of a front shaft motor is smaller than the required torque of the front shaft single motor electric braking, the output torque of the front shaft single motor electric braking is the required torque of the front shaft single motor electric braking, the output torque of the rear shaft single motor electric braking is the required torque of the rear shaft single motor electric braking, and the target hydraulic pressure of the electronic hydraulic booster is the overflow pressure of the electronic hydraulic booster;
when the current maximum output negative torque of the front shaft motor is larger than or equal to the current maximum output negative torque of the front shaft single motor electric braking demand torque, the output torque of the front shaft single motor electric braking is the current maximum output negative torque of the front shaft motor, the output torque of the rear shaft single motor electric braking demand torque is the rear shaft single motor electric braking demand torque, and the target hydraulic pressure of the electronic hydraulic booster is determined based on the overflow pressure of the electronic hydraulic booster, the current maximum output negative torque of the front shaft motor and the front shaft single motor electric braking demand torque.
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