CN117087626A - Redundant braking method and device based on in-splayed active steering, vehicle and medium - Google Patents
Redundant braking method and device based on in-splayed active steering, vehicle and medium Download PDFInfo
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- 238000005096 rolling process Methods 0.000 claims description 12
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/17—Using electrical or electronic regulation means to control braking
- B60T8/171—Detecting parameters used in the regulation; Measuring values used in the regulation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
- B60W50/02—Ensuring safety in case of control system failures, e.g. by diagnosing, circumventing or fixing failures
- B60W50/0225—Failure correction strategy
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
- B60W2050/0001—Details of the control system
- B60W2050/0019—Control system elements or transfer functions
- B60W2050/0028—Mathematical models, e.g. for simulation
- B60W2050/0031—Mathematical model of the vehicle
- B60W2050/0034—Multiple-track, 2D vehicle model, e.g. four-wheel model
Abstract
The application relates to the technical field of vehicles, in particular to a redundant braking method, a device, a vehicle and a medium based on in-splayed active steering, wherein a plurality of wheels of a full-drive electric vehicle are independently controlled, and the method comprises the following steps: receiving a braking demand of a user; judging whether a driving system and a braking system of the full-drive electric vehicle are in a fault state or not based on braking requirements, and determining a target braking strategy of the vehicle based on a pre-established whole vehicle model when the driving system and/or the braking system of the vehicle are in the fault state; and performing front-wheel in-eight-character active steering braking, or rear-wheel in-eight-character active steering braking, or four-wheel in-eight-character active steering braking on the all-wire electric vehicle based on the target braking strategy. Therefore, redundant braking is realized through the four-wheel independent steering system, and the problem that the braking function of the vehicle is completely lost due to the failure of the braking system at the present stage is solved, so that the driving safety is improved.
Description
Technical Field
The application relates to the technical field of vehicles, in particular to a redundant braking method and device based on in-splayed active steering, a vehicle and a medium.
Background
The energy crisis and environmental pollution make electric vehicle become global trend, meanwhile, the requirement of the user on vehicle performance is also continuously improved, the traditional vehicle is difficult to have great improvement on the whole vehicle performance due to the limitation of the inherent chassis form, and the full-drive electric vehicle based on four-wheel independent driving, independent braking and independent steering accords with the development trend of vehicle electrodynamic property due to the fact that the driving force, braking force and rotation angle of each wheel are controllable, has more controllable degrees of freedom, can further improve the vehicle performance, is easier to realize active fault-tolerant control, and has better development prospect. The active fault-tolerant control is used for indicating the failure of a single or a plurality of actuators, and by reconstructing the working modes of the other actuators, the execution actions of the other actuators are reasonably distributed, so that the vehicle can still stably run, and the active fault-tolerant control has important significance for ensuring the safety of the full-drive electric vehicle.
In the related art, various active fault-tolerant control methods based on four-wheel driving force and braking force distribution are proposed, and the principle is that when a steering system fails, an additional yaw moment of the whole vehicle is calculated through a controller and distributed to each wheel, and a redundant steering function is realized by changing the distribution of the four-wheel driving force and the braking force.
However, when the driving system and the braking system fail, the study on how to perform redundant braking through the four-wheel independent steering system is in a blank state, the braking function is the most basic and important function for ensuring the safe running of the automobile, and under the extreme working condition that the driving system and/or the braking system fail, the complete loss of the braking function seriously threatens the running safety, so that the problem needs to be solved.
Disclosure of Invention
The application provides a redundant braking method, device, vehicle and medium based on in-eight active steering, which are used for solving the problem that the braking function of the vehicle is completely lost due to the failure of a braking system at the present stage, so that the driving safety is improved.
In order to achieve the above object, an embodiment of a first aspect of the present application provides a redundant braking method based on in-splayed active steering, including the following steps:
receiving a braking demand of a user;
judging whether a driving system and a braking system of the full-drive electric vehicle are in a fault state or not based on the braking requirement, and determining a target braking strategy of the vehicle based on a pre-established whole vehicle model when the driving system and/or the braking system of the vehicle are in the fault state; and
and performing front-wheel in-splayed active steering braking, or rear-wheel in-splayed active steering braking, or four-wheel in-splayed active steering braking on the all-drive-by-wire electric vehicle based on the target braking strategy.
According to one embodiment of the present application, before determining the target braking strategy of the all-wire electric vehicle based on the pre-established vehicle model, the method further comprises:
pre-establishing a whole vehicle model based on the rotation freedom degree, steering freedom degree, vehicle longitudinal direction freedom degree, vehicle transverse direction freedom degree and vehicle yaw direction freedom degree of each wheel of the vehicle to be trained;
based on the whole vehicle model, the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels and the braking effect of the splayed active steering in the four wheels are simulated respectively to obtain the simulation result of the splayed active steering braking in the front wheels, the simulation result of the splayed active steering braking in the rear wheels and the simulation result of the splayed active steering braking in the four wheels.
According to one embodiment of the present application, the pre-building of the vehicle model based on the rotational degree of freedom, the steering degree of freedom, the longitudinal degree of freedom, the lateral degree of freedom and the yaw direction degree of freedom of the vehicle includes:
according to the rotational freedom degree, the steering freedom degree, the longitudinal freedom degree of the vehicle body, the transverse freedom degree of the vehicle body and the transverse freedom degree of the vehicle body of each wheel of the vehicle to be trained, establishing a first dynamic equation, a rotational dynamic equation, a kinematic equation and a tire model of the vehicle body of the vehicle to be trained in the longitudinal, transverse and transverse directions of the vehicle body;
And pre-establishing the whole vehicle model by using a preset simulation algorithm according to the first dynamics equation, the rotation dynamics equation, the kinematics equation and the tire model.
According to one embodiment of the application, the first kinetic equation is:
ma y ＝F Xfl sinδ fl +F Xfr sinδ fr +F Yfl cosδ fl +F Yfr cosδ fr +F Xrl sinδ rl +F Xrr sinδ rr +F Yrl cosδ rl +F Yrr cosδ rr
wherein m is the mass of the whole vehicle, a x For longitudinal acceleration, a y For lateral acceleration, F X For longitudinal forces exerted on the wheels F Y The lateral force (transverse force) applied to the wheel, delta is the wheel rotation angle, C D Is wind resistance coefficient, A is windward area, ρ is air density, I z For the moment of inertia of the vehicle in yaw,yaw acceleration of vehicle, B is wheelDistance, L f For the distance from the centre of mass to the front wheel, L r Fl, fr, rl, rr is the distance from the center of mass to the rear wheel, and v is the left front wheel, the right front wheel, the left rear wheel and the right rear wheel respectively x For lateral velocity, v y For longitudinal speed, omega z Yaw rate for the vehicle;
the rotation dynamics equation is:
wherein J is w For the moment of inertia of the wheel,for angular acceleration of the wheel, T m R is the driving moment of the wheel w For the rolling radius of the wheels, F Z Is the vertical force applied to the wheel, f w Is the rolling resistance coefficient.
The kinematic equation is:
wherein alpha is the tire slip angle;
The tire model is as follows:
F Y ＝Dsin(Carctan(Bα(1-E)+Earctan(Bα)))
the model parameters B, C, D, E are respectively:
C＝α 0
E＝a 6 F z +a 7
wherein,
wherein F is Z Is the vertical force applied to the wheel.
According to an embodiment of the present application, based on the whole vehicle model, the simulation of the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels, and the braking effect of the splayed active steering in the four wheels is performed respectively, and includes:
setting a vehicle speed, a driving moment and a braking moment based on the whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
setting the corners of the two front wheels to be in a left-right symmetrical inner splayed shape, and respectively simulating the braking effect of the inner splayed active steering of the two front wheels according to a plurality of different inner splayed corners.
According to an embodiment of the present application, based on the whole vehicle model, the simulation is performed on the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels, and the braking effect of the splayed active steering in the four wheels, and further includes:
setting a vehicle speed, a driving moment and a braking moment based on the whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
Setting the corners of the two rear wheels to be in a left-right symmetrical splayed shape, and respectively simulating the braking effect of the splayed active steering in the two rear wheels according to a plurality of different splayed corners.
According to an embodiment of the present application, based on the whole vehicle model, the simulation is performed on the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels, and the braking effect of the splayed active steering in the four wheels, and further includes:
setting a vehicle speed, a driving moment and a braking moment based on the whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
setting the corners of the two front wheels and the two rear wheels to be in a left-right symmetrical inner splayed shape at the same time, and respectively simulating the braking effect of the inner splayed active steering of the four wheels according to a plurality of different inner splayed corners.
According to the redundancy braking method based on the in-vehicle splayed active steering, which is provided by the embodiment of the application, whether the driving system and the braking system of the full-drive electric vehicle are in a fault state can be judged through the braking requirement of a user, when the driving system and/or the braking system of the vehicle are in the fault state, the target braking strategy of the vehicle is determined based on a pre-established whole vehicle model, and the front-wheel in-vehicle splayed active steering braking, or the rear-wheel in-vehicle splayed active steering braking, or the four-wheel in-vehicle splayed active steering braking is carried out on the full-drive electric vehicle based on the strategy. Therefore, redundant braking is realized through the four-wheel independent steering system, and the problem that the braking function of the vehicle is completely lost due to the failure of the braking system at the present stage is solved, so that the driving safety is improved.
To achieve the above object, a second aspect of the present application provides a redundant brake device based on in-splayed active steering, wherein a plurality of wheels of a full-drive electric vehicle are independently controlled, the device comprising:
the receiving module is used for receiving the braking requirement of a user;
the processing module is used for judging whether the driving system and the braking system of the full-drive electric vehicle are in a fault state or not based on the braking requirement, and determining a target braking strategy of the vehicle based on a pre-established whole vehicle model when the driving system and/or the braking system of the vehicle are in the fault state; and
and the braking module is used for performing front-wheel in-eight-character active steering braking, or rear-wheel in-eight-character active steering braking, or four-wheel in-eight-character active steering braking on the all-line electric vehicle based on the target braking strategy.
According to one embodiment of the application, before determining a target braking strategy for the all-wire electric vehicle based on a pre-established vehicle model, the processing module comprises:
the building unit is used for pre-building a whole vehicle model based on the rotation freedom degree, the steering freedom degree, the longitudinal freedom degree, the transverse freedom degree and the yaw direction freedom degree of the vehicle;
And the simulation unit is used for respectively simulating the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels and the braking effect of the splayed active steering in the four wheels based on the whole vehicle model to obtain a front-wheel splayed active steering braking simulation result, a rear-wheel splayed active steering braking simulation result and a four-wheel splayed active steering braking simulation result.
According to one embodiment of the application, the establishing unit is specifically configured to:
according to the rotational freedom degree, the steering freedom degree, the longitudinal freedom degree of the vehicle body, the transverse freedom degree of the vehicle body and the transverse freedom degree of the vehicle body of each wheel of the vehicle to be trained, establishing a first dynamic equation, a rotational dynamic equation, a kinematic equation and a tire model of the vehicle body of the vehicle to be trained in the longitudinal, transverse and transverse directions of the vehicle body;
and according to the first dynamics equation, the rotation dynamics equation, the kinematics equation and the tire model, the whole vehicle model is built in advance by using a preset simulation algorithm.
According to one embodiment of the application, the first kinetic equation is:
ma y ＝F Xfl sinδ fl +F Xfr sinδ fr +F Yfl cosδ fl +F Yfr cosδ fr +F Xrl sinδ rl +F Xrr sinδ rr +F Yrl cosδ rl +F Yrr cosδ rr
wherein m is the mass of the whole vehicle, a x For longitudinal acceleration, a y For lateral acceleration, F X For longitudinal forces exerted on the wheels F Y The lateral force (transverse force) applied to the wheel, delta is the wheel rotation angle, C D Is wind resistance coefficient, A is windward area, ρ is air density, I z For the moment of inertia of the vehicle in yaw,is yaw acceleration of the vehicle, B is track, L f For the distance from the centre of mass to the front wheel, L r Fl, fr, rl, rr is the distance from the center of mass to the rear wheel, and v is the left front wheel, the right front wheel, the left rear wheel and the right rear wheel respectively x For lateral velocity, v y For longitudinal speed, omega z Yaw rate for the vehicle;
the rotation dynamics equation is:
wherein J is w For the moment of inertia of the wheel,for angular acceleration of the wheel, T m R is the driving moment of the wheel w For the rolling radius of the wheels, F Z Is the vertical force applied to the wheel, f w Is the rolling resistance coefficient;
the kinematic equation is:
wherein alpha is the tire slip angle;
the tire model is as follows:
F Y ＝Dsin(Carctan(Bα(1-E)+Earctan(Bα)))
the model parameters B, C, D, E are respectively:
C＝α 0
E＝a 6 F z +a 7
wherein,
wherein F is Z Is the vertical force applied to the wheel.
According to one embodiment of the present application, the simulation unit is specifically configured to:
setting a vehicle speed, a driving moment and a braking moment based on the whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
Setting the corners of the two front wheels to be in a left-right symmetrical inner splayed shape, and respectively simulating the braking effect of the inner splayed active steering of the two front wheels according to a plurality of different inner splayed corners.
According to an embodiment of the application, the simulation unit is further configured to:
setting a vehicle speed, a driving moment and a braking moment based on the whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
setting the corners of the two rear wheels to be in a left-right symmetrical splayed shape, and respectively simulating the braking effect of the splayed active steering in the two rear wheels according to a plurality of different splayed corners.
According to an embodiment of the application, the simulation unit is further configured to:
setting a vehicle speed, a driving moment and a braking moment based on the whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
setting the corners of the two front wheels and the two rear wheels to be in a left-right symmetrical inner splayed shape at the same time, and respectively simulating the braking effect of the inner splayed active steering of the four wheels according to a plurality of different inner splayed corners.
According to the redundancy braking device based on the in-vehicle splayed active steering, which is provided by the embodiment of the application, through the braking requirement of a user, whether a driving system and a braking system of the full-drive electric vehicle are in a fault state or not can be judged, when the driving system and/or the braking system of the vehicle are in the fault state, a target braking strategy of the vehicle is determined based on a pre-established whole vehicle model, and the front-wheel in-vehicle splayed active steering braking, or the rear-wheel in-vehicle splayed active steering braking, or the four-wheel in-vehicle splayed active steering braking is carried out on the full-drive electric vehicle based on the strategy. Therefore, redundant braking is realized through the four-wheel independent steering system, and the problem that the braking function of the vehicle is completely lost due to the failure of the braking system at the present stage is solved, so that the driving safety is improved.
To achieve the above object, an embodiment of a third aspect of the present application provides a vehicle, including: the device comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, wherein the processor executes the program to realize the redundancy braking method based on the in-eight active steering as described in the embodiment.
To achieve the above object, a fourth aspect of the present application provides a computer storage medium having a computer program stored thereon, the program being executed by a processor for implementing the method for redundant braking based on in-splay active steering as described in the above embodiments.
Additional aspects and advantages of the application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the application.
Drawings
The foregoing and/or additional aspects and advantages of the application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a flow chart of a redundant braking method based on in-splayed active steering according to an embodiment of the present application;
FIG. 2 is a schematic illustration of tire stress during a front in-wheel splayed active steering condition according to one embodiment of the present application;
FIG. 3 is a schematic diagram of a redundant braking method based on in-splay active steering according to one embodiment of the present application;
FIG. 4 is a schematic diagram of a complete vehicle model of a complete drive-by-wire electric vehicle in accordance with one embodiment of the present application;
FIG. 5 is a schematic illustration of the results of an in-front-wheel splayed active steering brake simulation in accordance with one embodiment of the present application;
FIG. 6 is a schematic illustration of a rear in-wheel splayed active steering brake simulation result according to one embodiment of the present application;
FIG. 7 is a schematic illustration of four-wheel in-eight active steering braking simulation results according to one embodiment of the present application;
FIG. 8 is a block schematic diagram of a redundant brake based on in-splayed active steering in accordance with an embodiment of the present application;
fig. 9 is a schematic structural view of a vehicle according to an embodiment of the present application.
Detailed Description
Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present application and should not be construed as limiting the application.
The following describes a redundant braking method, a device, a vehicle and a medium based on in-splayed active steering according to an embodiment of the present application with reference to the accompanying drawings, and first describes a redundant braking method based on in-splayed active steering according to an embodiment of the present application with reference to the accompanying drawings.
FIG. 1 is a flow chart of a redundant braking method based on in-splay active steering in accordance with one embodiment of the present application.
Before describing the redundancy braking method based on the in-splayed active steering, which is provided by the embodiment of the application, the basic principle of the redundancy braking method based on the in-splayed active steering is described by taking the in-splayed active steering of the front wheel as an example, as shown in fig. 2, for the left front wheel, the left front wheel rolls rightwards if the left front wheel is not restrained due to the right turning; similarly for the right front wheel it will scroll to the left. In practice, however, due to the restraint of the front axle, the two wheels can only travel together in a forward direction, so that the left front wheel is subjected to a lateral force to the right and the right front wheel is subjected to a lateral force to the left and the rear, and the components of these two lateral forces in the longitudinal direction of the vehicle can exert a braking effect on the vehicle.
For the basic principle, referring to fig. 1 and 3, the redundant braking method based on the splayed active steering comprises the following steps:
in step S101, a braking demand of a user is received.
The brake system is a special brake mechanism mounted on a vehicle in order to technically secure safe running of the vehicle, to increase the average speed of the vehicle, and the like. Generally, a brake system comprises two independent sets of service brake devices and parking brake devices, wherein the service brake devices are operated by the feet of a driver, so the service brake devices are also called foot brake devices; parking brake devices are operated by the hand of the driver and are also known as hand brake devices. This is achieved by the braking system when there is a need for the user to slow down or stop in a minimum distance during travel.
In step S102, it is determined whether the driving system and the braking system of the all-line electric vehicle are in a failure state based on the braking demand, and when the driving system and/or the braking system of the vehicle are in a failure state, a target braking strategy of the vehicle is determined based on a pre-established model of the whole vehicle.
Wherein, a plurality of wheels of the full-drive electric vehicle are all independently controlled. When the braking requirement of a user is received, if the driving system and the braking system of the full-drive electric vehicle are normal, the vehicle can be directly controlled to decelerate or stop based on the braking requirement of the user; if the driving system of the full-drive electric vehicle is normal and the braking system is in a fault state, the vehicle can be controlled to be decelerated or stopped according to the selection of a user by using the driving system or the vehicle can be decelerated or stopped by using the target braking strategy determined by the embodiment of the application based on the pre-established whole vehicle model; similarly, if the brake system of the full-drive electric vehicle is normal and the driving system is in a fault state, the vehicle can be controlled to be decelerated or stopped according to the selection of a user by utilizing the brake system or by utilizing the target brake strategy of the embodiment of the application; if the driving system and the braking system of the full-drive electric vehicle are in a fault state and the driving system and the braking system cannot be used for controlling the vehicle to slow down or stop, the vehicle can be controlled to slow down or stop by utilizing the target braking strategy of the vehicle determined based on the pre-established whole vehicle model.
In step S103, the front-wheel in-eight active steering brake, or the rear-wheel in-eight active steering brake, or the four-wheel in-eight active steering brake is performed on the all-drive-by-wire electric vehicle based on the target braking strategy.
Specifically, when a user selects to utilize the target braking strategy of the embodiment of the application to brake and control the vehicle, the user can select according to actual conditions based on the target braking strategy, for example, for the vehicle with the independent steering function of the front wheels, the splayed active steering braking strategy in the front wheels can be selected, and the vehicle is controlled to perform the splayed active steering braking in the front wheels; for the vehicle with the independent steering function of the rear wheels, the splayed active steering braking strategy in the rear wheels can be selected, and the vehicle is controlled to perform the splayed active steering braking in the rear wheels; when the four-wheel independent steering function is realized and the braking requirement is high, the four-wheel in-eight-character active steering braking strategy can be selected, and the vehicle is controlled to perform four-wheel in-eight-character active steering braking.
The eight-shaped active steering in the front wheel is that the left front wheel of the vehicle steers right, the right front wheel steers left, and the rotation angles of the left wheel and the right wheel are equal; the splayed active steering in the rear wheel is that the left rear wheel of the vehicle turns right, the right rear wheel turns left, and the turning angles of the left wheel and the right wheel are equal; the four-wheel in-eight-character active steering is that the front-wheel in-eight-character active steering and the rear-wheel in-eight-character active steering occur simultaneously, and the corners of the four wheels are equal.
In order to facilitate the technical solution of the embodiment of the present application to be further understood by those skilled in the art, a process for establishing a whole vehicle model is first introduced.
In some embodiments, before determining the target braking strategy for the all-drive electric vehicle based on the pre-established vehicle model, further comprising: pre-establishing a whole vehicle model based on the rotation freedom degree, steering freedom degree, vehicle longitudinal direction freedom degree, vehicle transverse direction freedom degree and vehicle yaw direction freedom degree of each wheel of the vehicle to be trained; based on a whole vehicle model, the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels and the braking effect of the splayed active steering in the four wheels are simulated respectively to obtain a front-wheel splayed active steering braking simulation result, a rear-wheel splayed active steering braking simulation result and a four-wheel splayed active steering braking simulation result.
It can be understood that under the redundant braking working condition based on the in-splayed active steering, the tires of the vehicle are in a sideslip state and the tire wear is severe, so that the method is researched by adopting modeling and simulation means in order to save the cost and shorten the development period.
Since the plurality of wheels of the all-drive electric vehicle are independently controlled, the whole vehicle model of the embodiment of the application needs to reflect the characteristics of four-wheel independent driving, independent braking and independent steering, and therefore, an initial whole vehicle model (comprising 11 degrees of freedom in total) needs to be built based on the rotational degree of freedom (4 degrees of freedom), the steering degree of freedom (4 degrees of freedom), the longitudinal degree of freedom of the vehicle body, the lateral degree of freedom of the vehicle body and the yaw direction degree of freedom of the vehicle body of each wheel of the vehicle to be trained. After the initial whole vehicle model is obtained, the initial whole vehicle model can be respectively simulated based on the initial whole vehicle model, namely the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels and the braking effect of the splayed active steering in the four wheels, so that the front-wheel splayed active steering braking simulation result, the rear-wheel splayed active steering braking simulation result and the four-wheel splayed active steering braking simulation result are obtained, and the initial whole vehicle model is corrected according to the front-wheel splayed active steering braking simulation result, the rear-wheel splayed active steering braking simulation result and the four-wheel splayed active steering braking simulation result, and finally the pre-established whole vehicle model can be obtained.
As one possible implementation, in some embodiments, pre-building the vehicle model based on the rotational degrees of freedom, the steering degrees of freedom, the vehicle longitudinal degrees of freedom, the vehicle lateral degrees of freedom, and the vehicle yaw direction degrees of freedom for each wheel of the vehicle to be trained, includes: according to the rotational freedom degree, steering freedom degree, longitudinal freedom degree, transverse freedom degree and transverse freedom degree of the vehicle body of each wheel of the vehicle to be trained, a first dynamic equation, a rotational dynamic equation, a kinematic equation and a tire model of the longitudinal, transverse and transverse directions of the vehicle to be trained are established; and according to the first dynamics equation, the rotation dynamics equation, the kinematics equation and the tire model, a whole vehicle model is established in advance by using a preset simulation algorithm.
First, as shown in fig. 4, based on newton's law, a first dynamics equation of the longitudinal, lateral and yaw directions of the body of the vehicle to be trained and a rotation dynamics equation of each wheel are established.
Wherein, in some embodiments, the first kinetic equation is:
ma y ＝F Xfl sinδ fl +F Xfr sinδ fr +F Yfl cosδ fl +F Yfr cosδ fr +F Xrl sinδ rl +F Xrr sinδ rr +F Yrl cosδ rl +F Yrr cosδ rr
wherein the longitudinal acceleration and the lateral acceleration can be expressed as:
wherein m is the mass of the whole vehicle, and the unit is kg and a x Is longitudinal acceleration in m/s 2 ，a y Is the transverse acceleration, the unit is m/s 2 ，F X Is the longitudinal force applied by the wheel, and has the unit of N, F Y The unit of the lateral force (transverse force) applied to the wheel is N, delta is the wheel rotation angle, and the unit is delta and C D Is wind resistance coefficient, A is windward area, and the unit is m 2 ρ is the air density in N.s 2 /m 4 ，I z The unit is kg.m for the yaw moment of inertia of the vehicle 2 ，Is the yaw acceleration of the vehicle in rad/s 2 B is track, the unit is m, L f Is the distance from the mass center to the front wheel, and the unit is m and L r The distance from the center of mass to the rear wheel is m, and fl, fr, rl, rr is respectively a left front wheel, a right front wheel, a left rear wheel and a right rear wheel, v x For lateral velocity, v y For longitudinal speed, omega z Is the vehicle yaw rate.
For a single wheel, the rotational dynamics equations are:
wherein J is w The unit of the moment of inertia of the wheel is kg.m 2 ，Angular acceleration of the wheel in rad/s 2 ，T m Is the driving moment (torque) of the wheels, in Nm, r w Is the rolling radius of the wheel, and has the unit of m and F Z Is the vertical force applied to the wheel, and has the unit of N, f w Is the rolling resistance coefficient. The remaining vehicle parameters to be trained can be seen in table 1.
TABLE 1
| Parameters and symbols | Numerical value |
| Whole vehicle mass m | 1350kg |
| Wind resistance coefficient C D | 0.3 |
| Frontal area A | 1.8m 2 |
| Air density ρ | 1.2258N·s 2 /m 4 |
| Automobile yaw moment of inertia I z | 2523kg·m 2 |
| Track B | 1.54m |
| Centroid to front wheel distance L f | 0.056m |
| Centroid to rear wheel distance L r | 1.555m |
| Moment of inertia J of wheel w | 1kg·m 2 |
| Wheel rolling radius r w | 0.316m |
| Coefficient of rolling resistance f w | 0.014 |
| Centroid height h | 0.54m |
| Wheelbase L | 2.611m |
| Acceleration of gravity g | 9.8m/s 2 |
In addition, the following kinematic relationship exists between the tire slip angle and the motion state of the vehicle, namely the kinematic equation is:
/>
where α is the tire slip angle in rad.
Based on the lateral force F exerted by the wheel Y With the slip angle α, a tire model may be built as:
F Y ＝Dsin(Carctan(Bα(1-E)+Earctan(Bα))) (5)
wherein B, C, D, E are model parameters, which can be further expressed as:
C＝α 0 (6)
E＝a 6 F z +a 7
wherein the tire model parameters are shown in table 2.
TABLE 2
| (symbol) | Numerical value |
| a 0 | 1.65 |
| a 1 | -34 |
| a 2 | 1250 |
| a 3 | 3036 |
| a 4 | 12.8 |
| a 6 | -0.021 |
| a 7 | 0.7739 |
Wherein the wheel is subjected to a vertical force F Z Can be expressed as:
according to the formulas (1) to (7), a whole vehicle model of the whole electric vehicle is built based on a preset simulation algorithm (such as Matlab, simulink and the like), and the model is formed by the torque (T mfl 、T mfr 、T mrl 、T mrr ) And the rotation angle (delta) of four wheels fl 、δ fr 、δ rl 、δ rr ) As inputs, a vehicle longitudinal speed, a lateral speed, a yaw rate, four wheel speeds, and the like are taken as outputs.
Next, simulation processes performed on the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels and the braking effect of the splayed active steering in the four wheels are respectively described.
In some embodiments, based on a whole vehicle model, the simulation of the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels and the braking effect of the splayed active steering in the four wheels is performed respectively, and the simulation method comprises the following steps: setting a vehicle speed, a driving moment and a braking moment based on a whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force; the turning angles of the two front wheels are arranged in a left-right symmetrical inner splayed shape, and the braking effect of the inner splayed active steering of the two front wheels is simulated according to a plurality of different inner splayed turning angles.
Specifically, based on the whole vehicle model, the vehicle speed can be set to be 30km/h (calibratable), the torques (driving torque and braking torque) of four wheels are 0, at the moment, the whole-line electric vehicle is in a sliding state without driving force and braking force, two rear wheel corners are set to be 0, simulation researches are carried out on the corners of two front wheels at 2 degrees, 4 degrees, 8 degrees, 16 degrees, 32 degrees, 64 degrees and 90 degrees respectively, and the vehicle is manufactured under different in-eight corner conditionsDynamic deceleration simulation results are 0.277870401m/s respectively 2 、0.535423627m/s 2 、1.035068107m/s 2 、1.902587519m/s 2 、3.286014721m/s 2 、4.95147554m/s 2 And 5.15995872m/s 2 . As shown in figure 5, as the turning angle of the inner splayed is gradually increased, the braking deceleration is gradually increased, but the increasing speed is slower and slower, and the maximum braking deceleration generated by the inner splayed steering of the front wheel is 5.1600m/s 2 。
Further, in other embodiments, based on the whole vehicle model, the simulation is performed on the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels and the braking effect of the splayed active steering in the four wheels, and the method further comprises: setting a vehicle speed, a driving moment and a braking moment based on a whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force; the turning angles of the two rear wheels are arranged in a left-right symmetrical inner splayed shape, and the braking effect of the inner splayed active steering of the two rear wheels is simulated according to a plurality of different inner splayed turning angles.
Specifically, based on the whole vehicle model, the vehicle speed can be set to be 30km/h (calibratable), the torques (driving torque and braking torque) of four wheels are 0, at the moment, the whole-line electric vehicle is in a sliding state without driving force and braking force, two front wheel corners are set to be 0, the corners of two rear wheels are respectively subjected to simulation research at 2 degrees, 4 degrees, 8 degrees, 16 degrees, 32 degrees, 64 degrees and 90 degrees, and the simulation results of braking deceleration under different in-eight-shaped corners are 0.236172122m/s respectively 2 、0.410812587m/s 2 、0.732536334m/s 2 、1.250875613m/s 2 、1.992666985m/s 2 、2.754820937m/s 2 And 2.842201m/s 2 . As shown in FIG. 6, as the turning angle of the inner splayed wheel increases gradually, the braking deceleration increases gradually, but the increasing speed is slower and slower, and the maximum braking deceleration generated by the inner splayed steering of the front wheel is 2.842201m/s 2 。
Further, in some embodiments, based on the whole vehicle model, the simulation is performed on the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels and the braking effect of the splayed active steering in the four wheels, and the method further comprises: setting a vehicle speed, a driving moment and a braking moment based on a whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force; the two front wheels and the two rear wheels are arranged at the corners of the left-right symmetrical inner splayed shape, and the braking effect of the inner splayed active steering of the four wheels is simulated according to a plurality of different inner splayed corners.
Specifically, based on the whole vehicle model, the vehicle speed can be set to be 30km/h (calibratable), the torques (driving torque and braking torque) of four wheels are 0, at the moment, the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force, the rotation angles of the four wheels are the same, simulation researches are respectively carried out at 2 degrees, 4 degrees, 8 degrees, 16 degrees, 32 degrees, 64 degrees and 90 degrees, and the simulation results of the braking deceleration under different in-splayed rotation angles are 0.375713856m/s respectively 2 、0.807258872m/s 2 、1.61780884m/s 2 、2.973005114m/s 2 、4.9990002m/s 2 、7.233796296m/s 2 And 7.548309179m/s 2 . As shown in FIG. 7, as the turning angle of the inner splayed wheel increases gradually, the braking deceleration increases gradually, but the increasing speed is slower and slower, and the maximum braking deceleration generated by the inner splayed steering of the front wheel is 7.548309179m/s 2 。
It should be noted that, the selection of the splayed corner angle in the wheel is not particularly limited in the embodiment of the application, and in the actual simulation process, the corresponding braking deceleration can be obtained by simulating any splayed corner in the interval of 0-90 degrees. In order to reduce the workload and improve the accuracy of the simulation result, preferably, the embodiment of the application selects the set of rotation angle data (2 °, 4 °, 8 °, 16 °, 32 °, 64 ° and 90 °) to obtain the overall curve shape of the simulation result, and since the rotation angle of the splayed is 90 ° at maximum, the embodiment of the application takes 90 ° at maximum, as can be seen in fig. 5 to 7, the deceleration increases more and more slowly when the rotation angle of the splayed is larger and larger.
In addition, as known from the basic principle of the redundancy braking method based on the in-splayed active steering, the braking force generated based on the in-splayed active steering is mainly related to the magnitude of the in-splayed corner and has a small relationship with the vehicle speed, so that the vehicle speed of 30km/h is selected as an example for simulation analysis, and other vehicle speed simulation results are selected similarly, and the method is not particularly limited.
The simulation results show that the positive steering of the eight characters in the front wheel, the positive steering of the eight characters in the rear wheel and the positive steering of the eight characters in the four wheels can generate braking effects, so that the braking device can be used as a redundant braking mode when a driving system and a braking system are invalid. Under the same inner splayed rotation angle, the three working conditions have the smallest braking deceleration generated by the inner splayed active steering of the rear wheels, the largest braking deceleration generated by the inner splayed active steering of the four wheels, the middle braking deceleration generated by the inner splayed active steering of the front wheels, and a user can select inner splayed steering braking strategies in different forms according to the needs.
In summary, the application realizes the redundant braking function by only controlling the four-wheel independent steering system, fills up the research blank in the aspect of the redundant braking function when the driving system and the braking system are invalid at the present stage, and further digs the potential of the full-drive electric vehicle in the aspect of active fault-tolerant control.
According to the redundancy braking method based on the in-vehicle splayed active steering, which is provided by the embodiment of the application, whether the driving system and the braking system of the full-drive electric vehicle are in a fault state can be judged through the braking requirement of a user, when the driving system and/or the braking system of the vehicle are in the fault state, the target braking strategy of the vehicle is determined based on a pre-established whole vehicle model, and the front-wheel in-vehicle splayed active steering braking, or the rear-wheel in-vehicle splayed active steering braking, or the four-wheel in-vehicle splayed active steering braking is carried out on the full-drive electric vehicle based on the strategy. Therefore, redundant braking is realized through the four-wheel independent steering system, and the problem that the braking function of the vehicle is completely lost due to the failure of the braking system at the present stage is solved, so that the driving safety is improved.
Next, a redundant brake device based on in-eight active steering according to an embodiment of the present application is described with reference to the accompanying drawings, where multiple wheels of a full-drive electric vehicle are independently controlled.
Fig. 8 is a block schematic diagram of a redundant brake based on in-splayed active steering in accordance with one embodiment of the present application.
As shown in fig. 8, the in-eight-character-based active steering redundant brake apparatus 10 includes: a receiving module 100, a processing module 200 and a braking module 300.
Wherein, the receiving module 100 is configured to receive a braking requirement of a user;
the processing module 200 is configured to determine whether a driving system and a braking system of the all-drive electric vehicle are in a fault state based on a braking requirement, and determine a target braking strategy of the vehicle based on a pre-established whole vehicle model when the driving system and/or the braking system of the vehicle are in the fault state; and
the braking module 300 is configured to perform front-wheel in-eight active steering braking, or rear-wheel in-eight active steering braking, or four-wheel in-eight active steering braking on the all-drive-by-wire electric vehicle based on the target braking strategy.
Further, in some embodiments, before determining a target braking strategy for the all-drive electric vehicle based on a pre-established vehicle model, the processing module 200 includes:
the building unit is used for pre-building a whole vehicle model based on the rotation freedom degree, the steering freedom degree, the longitudinal freedom degree, the transverse freedom degree and the yaw direction freedom degree of the vehicle;
The simulation unit is used for respectively simulating the braking effect of the eight-character active steering in the two front wheels, the braking effect of the eight-character active steering in the two rear wheels and the braking effect of the eight-character active steering in the four wheels based on the whole vehicle model to obtain a front-wheel eight-character active steering braking simulation result, a rear-wheel eight-character active steering braking simulation result and a four-wheel eight-character active steering braking simulation result
Further, in some embodiments, the establishing unit is specifically configured to:
according to the rotational freedom degree, steering freedom degree, longitudinal freedom degree, transverse freedom degree and transverse freedom degree of the vehicle body of each wheel of the vehicle to be trained, a first dynamic equation, a rotational dynamic equation, a kinematic equation and a tire model of the longitudinal, transverse and transverse directions of the vehicle to be trained are established;
and according to the first dynamics equation, the rotation dynamics equation, the kinematics equation and the tire model, a whole vehicle model is established in advance by using a preset simulation algorithm.
Further, in some embodiments, the first kinetic equation is:
ma y ＝F Xfl sinδ fl +F Xfr sinδ fr +F Yfl cosδ fl +F ffr cosδ fr +F Xrl sinδ rl +F Xrr sinδ rr +F Yrl cosδ rl +F Yrr cosδ rr
wherein m is the mass of the whole vehicle, a x For longitudinal acceleration, a y For lateral acceleration, F X For longitudinal forces exerted on the wheels F Y The lateral force (transverse force) applied to the wheel, delta is the wheel rotation angle, C D Is wind resistance coefficient, A is windward area, ρ is air density, I z For the moment of inertia of the vehicle in yaw,is yaw acceleration of the vehicle, B is track, L f For the distance from the centre of mass to the front wheel, L r Fl, fr, rl, rr is the distance from the center of mass to the rear wheel, and v is the left front wheel, the right front wheel, the left rear wheel and the right rear wheel respectively x For lateral velocity, v y For longitudinal speed, omega z Yaw rate for the vehicle;
the rotation dynamics equation is:
wherein J is w For the moment of inertia of the wheel,for angular acceleration of the wheel, T m R is the driving moment of the wheel w For the rolling radius of the wheels, F Z Is the vertical force applied to the wheel, f w Is the rolling resistance coefficient;
the kinematic equation is:
/>
wherein alpha is the tire slip angle;
the tire model is as follows:
F Y ＝Dsin(Carctan(Bα(1-E)+Earctan(Bα)))
the model parameters B, C, D, E are respectively:
C＝α 0
E＝a 6 F Z +a 7
wherein,
wherein F is Z Is the vertical force applied to the wheel.
Further, in some embodiments, the simulation unit is specifically configured to:
setting a vehicle speed, a driving moment and a braking moment based on a whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
The turning angles of the two front wheels are arranged in a left-right symmetrical inner splayed shape, and the braking effect of the inner splayed active steering of the two front wheels is simulated according to a plurality of different inner splayed turning angles.
Further, in some embodiments, the simulation unit is further configured to:
setting a vehicle speed, a driving moment and a braking moment based on a whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
the turning angles of the two rear wheels are arranged in a left-right symmetrical inner splayed shape, and the braking effect of the inner splayed active steering of the two rear wheels is simulated according to a plurality of different inner splayed turning angles.
Further, in some embodiments, the simulation unit is further configured to:
setting a vehicle speed, a driving moment and a braking moment based on a whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
the two front wheels and the two rear wheels are arranged at the corners of the left-right symmetrical inner splayed shape, and the braking effect of the inner splayed active steering of the four wheels is simulated according to a plurality of different inner splayed corners.
It should be noted that the foregoing explanation of the embodiment of the redundant braking method based on the in-splayed active steering is also applicable to the redundant braking device based on the in-splayed active steering of the embodiment, and will not be repeated herein.
According to the redundancy braking device based on the in-vehicle splayed active steering, which is provided by the embodiment of the application, through the braking requirement of a user, whether a driving system and a braking system of the full-drive electric vehicle are in a fault state or not can be judged, when the driving system and/or the braking system of the vehicle are in the fault state, a target braking strategy of the vehicle is determined based on a pre-established whole vehicle model, and the front-wheel in-vehicle splayed active steering braking, or the rear-wheel in-vehicle splayed active steering braking, or the four-wheel in-vehicle splayed active steering braking is carried out on the full-drive electric vehicle based on the strategy. Therefore, redundant braking is realized through the four-wheel independent steering system, and the problem that the braking function of the vehicle is completely lost due to the failure of the braking system at the present stage is solved, so that the driving safety is improved.
Fig. 9 is a schematic structural diagram of a vehicle according to an embodiment of the present application. The vehicle may include:
memory 901, processor 902, and a computer program stored on memory 901 and executable on processor 902.
The processor 902 implements the redundant braking method based on in-eight active steering provided in the above embodiment when executing a program.
Further, the vehicle further includes:
A communication interface 903 for communication between the memory 901 and the processor 902.
Memory 901 for storing a computer program executable on processor 902.
The memory 901 may include a high-speed RAM (Random Access Memory ) memory, and may also include a nonvolatile memory, such as at least one magnetic disk memory.
If the memory 901, the processor 902, and the communication interface 903 are implemented independently, the communication interface 903, the memory 901, and the processor 902 may be connected to each other through a bus and perform communication with each other. The bus may be an ISA (Industry Standard Architecture ) bus, a PCI (Peripheral Component, external device interconnect) bus, or EISA (Extended Industry Standard Architecture ) bus, among others. The buses may be divided into address buses, data buses, control buses, etc. For ease of illustration, only one thick line is shown in fig. 9, but not only one bus or one type of bus.
Alternatively, in a specific implementation, if the memory 901, the processor 902, and the communication interface 903 are integrated on a chip, the memory 901, the processor 902, and the communication interface 903 may communicate with each other through internal interfaces.
The processor 902 may be a CPU (Central Processing Unit ) or ASIC (Application Specific Integrated Circuit, application specific integrated circuit) or one or more integrated circuits configured to implement embodiments of the present application.
The embodiment of the application also provides a computer readable storage medium, on which a computer program is stored, which when being executed by a processor, realizes the redundancy braking method based on the in-eight active steering.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.
Claims (10)
1. A redundant braking method based on in-eight active steering, characterized in that a plurality of wheels of a full-drive electric vehicle are all independently controlled, wherein the method comprises the following steps:
receiving a braking demand of a user;
judging whether a driving system and a braking system of the full-drive electric vehicle are in a fault state or not based on the braking requirement, and determining a target braking strategy of the vehicle based on a pre-established whole vehicle model when the driving system and/or the braking system of the vehicle are in the fault state; and
and performing front-wheel in-splayed active steering braking, or rear-wheel in-splayed active steering braking, or four-wheel in-splayed active steering braking on the all-drive-by-wire electric vehicle based on the target braking strategy.
2. The method of claim 1, further comprising, prior to determining the target braking strategy for the all-drive electric vehicle based on a pre-established vehicle model:
Pre-establishing a whole vehicle model based on the rotation freedom degree, steering freedom degree, vehicle longitudinal direction freedom degree, vehicle transverse direction freedom degree and vehicle yaw direction freedom degree of each wheel of the vehicle to be trained;
based on the whole vehicle model, the braking effect of the splayed active steering in the two front wheels, the braking effect of the splayed active steering in the two rear wheels and the braking effect of the splayed active steering in the four wheels are simulated respectively to obtain the simulation result of the splayed active steering braking in the front wheels, the simulation result of the splayed active steering braking in the rear wheels and the simulation result of the splayed active steering braking in the four wheels.
3. The method of claim 2, wherein the pre-building the vehicle model based on the rotational degrees of freedom, the steering degrees of freedom, the longitudinal degrees of freedom, the lateral degrees of freedom, and the yaw degrees of freedom of the vehicle for each wheel of the vehicle to be trained comprises:
according to the rotational freedom degree, the steering freedom degree, the longitudinal freedom degree of the vehicle body, the transverse freedom degree of the vehicle body and the transverse freedom degree of the vehicle body of each wheel of the vehicle to be trained, establishing a first dynamic equation, a rotational dynamic equation, a kinematic equation and a tire model of the vehicle body of the vehicle to be trained in the longitudinal, transverse and transverse directions of the vehicle body;
And pre-establishing the whole vehicle model by using a preset simulation algorithm according to the first dynamics equation, the rotation dynamics equation, the kinematics equation and the tire model.
4. A method according to claim 3, wherein the first kinetic equation is:
ma y ＝ Xfl sinδ fl + Xfr sinδ fr + Yfl cosδ fl + Yfr cosδ fr +
F xrl sinδ rl + Xrr sinδ rr + Yrl cosδ rl + Yrr cosδ rr
wherein m is the mass of the whole vehicle, a x For longitudinal acceleration, a y For lateral acceleration, F X For longitudinal forces exerted on the wheels F Y The lateral force (transverse force) applied to the wheel, delta is the wheel rotation angle, C D Is wind resistance coefficient, A is windward area, ρ is air density, I z For the moment of inertia of the vehicle in yaw,is yaw acceleration of the vehicle, B is track, L f For the distance from the centre of mass to the front wheel, L r Fl, fr, rl, rr is the distance from the center of mass to the rear wheel, and v is the left front wheel, the right front wheel, the left rear wheel and the right rear wheel respectively x For lateral velocity, v y For longitudinal speed, omega z Yaw rate for the vehicle;
the rotation dynamics equation is:
wherein J is w For the moment of inertia of the wheel,for angular acceleration of the wheel, T m R is the driving moment of the wheel w For the rolling radius of the wheels, F Z Is the vertical force applied to the wheel, f w Is the rolling resistance coefficient;
the kinematic equation is:
wherein alpha is the tire slip angle;
The tire model is as follows:
F Y ＝D sin(Carctan(Bα(1-E)+Earctan(Bα)))
the model parameters B, C, D, E are respectively:
C＝α 0
E＝a 6 F Z + 7
wherein,
wherein F is Z Is the vertical force applied to the wheel.
5. The method according to claim 2, wherein the simulating the braking effect of the two front-wheel in-splay active steering, the braking effect of the two rear-wheel in-splay active steering, and the braking effect of the four in-wheel splay active steering based on the whole vehicle model respectively comprises:
setting a vehicle speed, a driving moment and a braking moment based on the whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
setting the corners of the two front wheels to be in a left-right symmetrical inner splayed shape, and respectively simulating the braking effect of the inner splayed active steering of the two front wheels according to a plurality of different inner splayed corners.
6. The method according to claim 2, wherein the simulating the braking effect of the two front-wheel in-splay active steering, the braking effect of the two rear-wheel in-splay active steering, and the braking effect of the four in-wheel splay active steering based on the whole vehicle model respectively further comprises:
setting a vehicle speed, a driving moment and a braking moment based on the whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
Setting the corners of the two rear wheels to be in a left-right symmetrical splayed shape, and respectively simulating the braking effect of the splayed active steering in the two rear wheels according to a plurality of different splayed corners.
7. The method according to claim 2, wherein the simulating the braking effect of the two front-wheel in-splay active steering, the braking effect of the two rear-wheel in-splay active steering, and the braking effect of the four in-wheel splay active steering based on the whole vehicle model respectively further comprises:
setting a vehicle speed, a driving moment and a braking moment based on the whole vehicle model, so that the whole drive-by-wire electric vehicle is in a sliding state without driving force and braking force;
setting the corners of the two front wheels and the two rear wheels to be in a left-right symmetrical inner splayed shape at the same time, and respectively simulating the braking effect of the inner splayed active steering of the four wheels according to a plurality of different inner splayed corners.
8. A redundant brake apparatus based on in-eight active steering, wherein a plurality of wheels of a full-drive electric vehicle are each independently controlled, wherein the apparatus comprises:
the receiving module is used for receiving the braking requirement of a user;
The processing module is used for judging whether the driving system and the braking system of the full-drive electric vehicle are in a fault state or not based on the braking requirement, and determining a target braking strategy of the vehicle based on a pre-established whole vehicle model when the driving system and/or the braking system of the vehicle are in the fault state; and
and the braking module is used for performing front-wheel in-eight-character active steering braking, or rear-wheel in-eight-character active steering braking, or four-wheel in-eight-character active steering braking on the all-line electric vehicle based on the target braking strategy.
9. A vehicle, characterized by comprising: a memory, a processor and a computer program stored on the memory and executable on the processor, the processor executing the program to implement the method of in-splay active steering based redundant braking as claimed in any one of claims 1 to 7.
10. A computer readable storage medium having stored thereon a computer program, the program being executed by a processor for implementing a method of redundant braking based on active in-splay steering as claimed in any one of claims 1 to 7.
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