CN116552485A - Automobile single-wheel failure fault-tolerant control method and system for distributed brake-by-wire - Google Patents
Automobile single-wheel failure fault-tolerant control method and system for distributed brake-by-wire Download PDFInfo
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- 210000001258 synovial membrane Anatomy 0.000 claims description 4
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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
- B60T17/00—Component parts, details, or accessories of power brake systems not covered by groups B60T8/00, B60T13/00 or B60T15/00, or presenting other characteristic features
- B60T17/18—Safety devices; Monitoring
- B60T17/22—Devices for monitoring or checking brake systems; Signal devices
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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
- B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
- B60T8/88—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration with failure responsive means, i.e. means for detecting and indicating faulty operation of the speed responsive control means
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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
- B60W10/00—Conjoint control of vehicle sub-units of different type or different function
- B60W10/18—Conjoint control of vehicle sub-units of different type or different function including control of braking systems
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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
- B60W10/00—Conjoint control of vehicle sub-units of different type or different function
- B60W10/20—Conjoint control of vehicle sub-units of different type or different function including control of steering systems
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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
- B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
- B60W30/02—Control of vehicle driving stability
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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
- B60W50/0205—Diagnosing or detecting failures; Failure detection models
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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
- B60W50/029—Adapting to failures or work around with other constraints, e.g. circumvention by avoiding use of failed parts
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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
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Abstract
The invention relates to a distributed line control action-oriented automobile single-wheel failure fault-tolerant control method and system, wherein the method comprises the following steps: acquiring a state signal of an automobile brake-by-wire system, and acquiring fault factors respectively representing fault types and fault degrees, thereby acquiring corresponding fault codes; according to the fault code, adopting a corresponding fault control strategy, and reconstructing braking force of each wheel of the vehicle based on braking force balance; loading the vehicle model into a linear two-degree-of-freedom automobile model according to the vehicle speed and the steering angle to obtain an ideal yaw rate, and then performing yaw moment control through a sliding film controller to obtain an additional yaw moment so as to realize differential braking control; if the target braking force of the wheels is larger than the maximum braking force, the active steering control is carried out, a weight factor for coordinating the differential braking control and the active steering control is set, the additional yaw moment is adjusted, and the integral control for introducing auxiliary steering is realized. Compared with the prior art, the invention has the advantages of high system safety, fault tolerance, high stability and the like.
Description
Technical Field
The invention relates to the technical field of automobile brake control, in particular to a distributed brake-by-wire oriented automobile single-wheel failure fault-tolerant control method and system.
Background
With the development trend of the electric and intelligent of the automobile industry, the wire control technology becomes a key technology for realizing the intelligent of the vehicle, and the application of the wire control technology to the vehicle control becomes a new trend. The drive-by-wire technology is initially used in the aerospace field, with the development of the drive-by-wire technology, almost all mechanical mechanisms of traditional automobiles can be replaced by electric execution elements, electronic control of automobiles is realized, and currently, integrated control of a drive-by-wire chassis and the drive-by-wire automobiles are main trends of future vehicle researches.
In the on-line control technology, a Brake-by-Wire (Brake-by-Wire) replaces the original complex and heavy hydraulic pipeline and related mechanical structures by utilizing an electronic control technology, and meanwhile, the on-line control system has the characteristics of quick response and high precision, and is one of the hot spots in the research of the current intelligent vehicle field. The brake-by-wire intention is converted into an electric signal to be transmitted to the brake controller, and then the brake motor is utilized to realize the braking of the vehicle, so that the response speed and accuracy of the brake are greatly improved compared with the traditional brake system. However, the brake-by-wire system may cause serious consequences when a failure occurs, and failure of part of the electronic control units in the system may directly lead to failure or abnormality of the brake system, and when failure of single-wheel or unbalanced braking force occurs, the brake system may not only lead to decrease of the total braking force of the vehicle, but also may lead to instability and rollover of the vehicle. Therefore, fault diagnosis measures and fault tolerant control for ensuring safety of a vehicle when braking fails become key technologies for future development.
The invention discloses a fault-tolerant control system and a control method aiming at automobile brake-by-wire failure faults, which can be applied to a brake-by-wire hydraulic braking system. When the brake-by-wire system fails, the control unit controls the brake-by-wire system to stop working and controls the two-position three-way electromagnetic valve to enable the master cylinder of the hydraulic brake system to be communicated with the wheel cylinder, and the hydraulic brake system is utilized to realize vehicle braking.
The invention discloses a digital twin-based brake-by-wire system and a dynamic optimization control method thereof, and provides a control method combining a physical brake-by-wire system, a whole vehicle control system and a digital twin-by-wire braking system, wherein the physical brake-by-wire system and the whole vehicle control system are connected through a vehicle-mounted CAN bus, the whole vehicle control system is connected with the digital twin-by-wire braking system through a high-speed communication link, and the digital twin-by-wire braking system is connected with the whole vehicle control system through the high-speed communication link, so that indirect communication and data interaction with the physical brake-by-wire system are realized.
The invention of application number CN202121121661.1 discloses a vehicle line control braking system based on a six-phase fault-tolerant motor, and provides a vehicle line control braking system which comprises a brake detection device, a brake execution device, an electronic control device and a warning device, wherein the six-phase fault-tolerant brake execution motor is adopted and can be used as two groups of three-phase motors for control, the six-phase fault-tolerant brake execution motor is an output shaft with two through ends, the output shafts at the two ends of the motor are respectively connected to cams and pistons at the two sides to form two sets of ABS pumps, and the outputs of the two groups of three-phase motors are mutually redundant; under the normal working condition of the brake-by-wire system, the two groups of three-phase motors work together, and if one motor fails, a warning is given and the basic ABS function is realized.
The invention of application number CN202211157787.3 discloses a redundant safety control system based on brake-by-wire, which proposes an electric booster brake mechanism and an electronic car body stabilizing system which are connected through at least two CAN buses, wherein the information transmitted by the two CAN buses is mutually backed up; the electric boosting braking mechanism and the electronic vehicle body stabilizing system are also connected with the whole vehicle controller, the motor controller and the electronic parking system through one path of CAN bus. And the fault risk identification and the corresponding redundant safety control of the brake-by-wire system are realized.
The invention with the application number of CN202211231810.9 discloses a dual-redundancy electronic brake booster system and a control method, wherein the dual-redundancy electronic brake booster system consists of a pedal module U1 and a booster module U2, and the dual-redundancy electronic brake booster system comprises a linkage pedal, a first simulation master cylinder and a second simulation master cylinder. When a driver applies pedal force to the linkage pedal, the linkage pedal pushes the two simulation master cylinders to simultaneously establish hydraulic pressure, the pedal travel signals are sent to the ECU controller by the pedal sensor I and the pedal sensor II, the power assisting module U2 is connected with the U1 through a pipeline, the power assisting module U2 is connected with the ESC outside, the ESC is communicated with the brake, mutual redundancy can be achieved, and the multi-stage backup capability is achieved.
The above prior art has the following drawbacks:
1. At present, most of vehicle brake-by-wire systems are EHB systems, and hydraulic structures are not completely removed, so that hydraulic redundancy is mostly adopted, and the vehicle brake-by-wire systems are not completely controlled by wires.
2. Most of current schemes for improving the brake-by-wire safety are to add redundant devices, and the scheme can improve the reliability of the system, but greatly improve the manufacturing cost of the system.
3. At present, a direct turn-off or switching redundancy backup device is generally adopted for a processing scheme of the failure of the brake-by-wire system, and the same control scheme is adopted for different types of failures.
Disclosure of Invention
The invention aims to overcome the defects that a wire control braking system is not complete and the same control scheme is adopted for different types of faults in the prior art, and provides a distributed wire control-oriented automobile single-wheel failure fault-tolerant control method and system.
The aim of the invention can be achieved by the following technical scheme:
a distributed line control action-oriented automobile single-wheel failure fault-tolerant control method comprises the following steps:
acquiring a state signal of an automobile brake-by-wire system; obtaining fault factors respectively representing the fault type and the fault degree according to the actual braking force of the wheels and the expected braking force of the wheels in the state signals, so as to obtain corresponding fault codes;
According to the fault code, adopting a corresponding fault control strategy, reconstructing braking force of each wheel of the vehicle based on braking force balance, and performing single-wheel failure preliminary braking control of the vehicle;
loading a linear two-degree-of-freedom automobile model based on lateral force and yaw moment according to the speed and the steering angle in the state signal, and obtaining an ideal yaw rate; according to the ideal yaw rate and the actual yaw rate, performing yaw moment control through a sliding film controller to obtain an additional yaw moment; distributing the additional yaw moment to the other wheels of the vehicle according to the failed wheels and the corresponding failure factors, and performing differential braking control;
judging whether the target braking force of each wheel is larger than the maximum braking force or not according to the braking force of each wheel and the additional yaw moment, if so, performing active steering control, calculating an additional turning angle based on the additional yaw moment according to the geometric structure of the vehicle and the tire cornering characteristics, setting a weight factor for coordinating differential braking control and active steering control, and adjusting the additional yaw moment and the additional turning angle to realize integral control for introducing auxiliary steering.
Further, the fault factor includes a fault factor lambda 1_i And a fault factor lambda 2_i The fault factor lambda 1_i For representing the type of failure of wheel i, said failure factor lambda 1_i The assigned expression of (2) is:
the fault factor lambda 2_i For representing the degree of failure of wheel i, said failure factor lambda 2_i The assigned expression of (2) is:
wherein i=fl/FR/RL/RR respectively represents a front axle left wheel, a front axle right wheel, a rear axle left wheel, and a rear axle right wheel, F xb_i For the actual braking force of wheel i, F exb_i Is the desired braking force for wheel i.
Further, if the front axle left wheel is a faulty wheel, the distribution expression for performing braking force reconstruction on each wheel of the vehicle based on braking force balance includes:
wherein F is dxb_FL Braking force distributed for left wheel of front axle, F exb_f Lambda is the desired braking force of the front axle 1_FL Lambda is the failure type of the left wheel of the front axle 2_FL F is the failure degree of the left wheel of the front axle dxb_FR Braking force distributed for front axle right wheel, F exb_r F for the desired braking force of the rear axle dxb_RL Braking force distributed for left wheel of rear axle, F dxb_RR The rear axle right wheel is assigned a rear braking force.
Further, the expression of the motion differential equation of the linear two-degree-of-freedom automobile model based on the lateral force and the yaw moment is as follows:
in the method, in the process of the invention,for centroid cornering angle gain +.>For yaw rate gain, C f For the yaw rigidity of the front axle C r The rigidity of the lateral deflection of the rear axle is M, the mass of the whole vehicle is V x Is the longitudinal speed, beta is the centroid slip angle, L a For the front axis to centroid distance, L b For the rear axle to centroid distance, ω is yaw rate, δ is front wheel angle, I z To rotate about the z-axis, ΔM b Is an additional yaw moment;
substituting the centroid slip angle and the yaw rate gain of 0 into the motion differential equation to obtain an ideal yaw rate calculation expression as follows:
wherein omega is exp For an ideal yaw rate, K is the stability factor and L is the front-to-rear axis distance.
Further, the process of yaw moment control by the slide film controller specifically includes:
setting a difference value between the ideal yaw rate and the actual yaw rate as a sliding film surface of a sliding film controller, and calculating by the sliding film controller to obtain a calculation expression of the additional yaw moment, wherein the calculation expression is as follows:
in the method, in the process of the invention,to the ideal yaw rate after the differentiation process omega exp Is an ideal yaw rate, and ζ is a slip film control parameter;
in the control process of the synovial membrane controller, the constraint of the ideal yaw rate and the ideal centroid slip angle comprises the following steps:
wherein omega is max Is the maximum value of ideal yaw rate, beta max Is the maximum value of ideal centroid slip angle.
Further, the specific process of distributing the additional yaw moment to the remaining wheels of the vehicle comprises:
if the left wheel of the front axle is a fault wheel and lambda 1_FL ·λ 2_FL When < 0, the calculated expression for assigning the additional yaw moment to the remaining wheels of the vehicle is:
wherein DeltaF x_FR ' is the longitudinal force of the front axle right wheel after being distributed, deltaF x_FR To achieve the yaw moment additional yaw moment front axle right wheel longitudinal force ΔM b For additional yaw moment, L b B is the wheel distance of the left and right wheels, L a Delta is the front wheel angle, delta F, which is the distance from the front axle to the center of mass x_RL ' is the distributed rear axle left wheel longitudinal force, ΔF x_RL To achieve yaw moment additional yaw moment rear axle left wheel longitudinal force, ΔF x_FL To achieve yaw moment additional yaw moment front axle left wheel longitudinal force, ΔF x_RR ' is the distributed rear axle right wheel longitudinal force, ΔF x_RR The longitudinal force of the right wheel of the rear axle for realizing the yaw moment is added with the yaw moment;
if the left wheel of the front axle is a fault wheel and 2 is more than lambda 1_FL ·λ 2_FL At > 0, the calculated expression for assigning the additional yaw moment to the remaining wheels of the vehicle is:
further, if the front axle left wheel is a faulty wheel, the calculation expression of the weight factor for coordinating the differential braking control and the active steering control is:
Wherein sigma is a weight factor, F xb_obj_i For the target braking force of the wheel i, F xb_max_i For maximum braking force of wheel i, F xb_i The actual braking force of the wheel i is FR/RL/RR respectively a front axle right wheel, a rear axle left wheel and a rear axle right wheel;
the additional yaw moment DeltaM b The control mode of (2) is adjusted as follows:
wherein DeltaM b_b For yaw moment generated by differential braking ΔM b_s For the yaw moment generated by adjusting the front wheel rotation angle, the calculation expression of the additional rotation angle is as follows:
wherein L is a For the rear axle to centroid distance C f Is the yaw stiffness of the front axle.
Further, when the target braking force of the wheels is greater than the maximum braking force, the calculated distribution expression of the additional yaw moment is:
wherein DeltaF xc_FR To assist the steering front axle right wheel longitudinal force ΔF xc_RL To assist the rear axle left wheel longitudinal force after steering ΔF xc_RR To assist the longitudinal force of the rear axle right wheel after steering, L b The distance from the rear axle to the mass center is B, the wheel distance of left and right wheels, delta is the front wheel corner, k s Is the steering ratio between the steering wheel angle and the front wheel angle; delta s Is the steering wheel angle.
The invention also provides a distributed line control-oriented automobile single-wheel failure fault-tolerant control system, which comprises the following steps:
the system failure identification module is used for acquiring a state signal of the automobile brake-by-wire system; obtaining fault factors respectively representing the fault type and the fault degree according to the actual braking force of the wheels and the expected braking force of the wheels in the state signals, so as to obtain corresponding fault codes;
The basic failure control module is used for adopting a corresponding failure control strategy according to the failure code, reconstructing braking force of each wheel of the vehicle based on braking force balance, and performing single-wheel failure primary braking control of the vehicle;
the sliding film differential control module is used for loading a linear two-degree-of-freedom automobile model based on lateral force and yaw moment according to the speed and the steering angle in the state signal to obtain an ideal yaw rate; according to the ideal yaw rate and the actual yaw rate, performing yaw moment control through a sliding film controller to obtain an additional yaw moment; distributing the additional yaw moment to the other wheels of the vehicle according to the failed wheels and the corresponding failure factors, and performing differential braking control;
the auxiliary steering control module is used for judging whether the target braking force of each wheel is larger than the maximum braking force according to the braking force of each wheel and the additional yaw moment, if so, performing active steering control, calculating the additional turning angle based on the additional yaw moment according to the geometric structure of the vehicle and the lateral deviation characteristics of the tire, setting a weight factor for coordinating the differential braking control and the active steering control, and adjusting the additional yaw moment and the additional turning angle to realize integral control for introducing auxiliary steering.
Further, the basic failure control module is a basic failure controller, and the basic failure controller is used for adopting a corresponding failure control strategy according to the failure code, reconstructing braking force of each wheel of the vehicle based on braking force balance, and performing single-wheel failure preliminary braking control on the vehicle;
the sliding film differential control module comprises a sliding film controller and a differential braking controller,
the sliding film controller is used for comparing the ideal yaw rate calculated by the linear two-degree-of-freedom automobile model with the actual yaw rate and performing yaw moment control to obtain an additional yaw moment;
the differential braking controller is used for controlling braking force according to the braking force reconstructed by the basic failure control module, further distributing the additional yaw moment to the rest wheels of the vehicle, and performing differential braking control based on the weight factors fed back by the auxiliary steering control module;
the auxiliary steering control module includes an attachment limit determination module and an auxiliary steering controller,
the attachment limit judging module is used for judging whether the target braking force of each wheel is larger than the maximum braking force according to the braking force of each wheel and the additional yaw moment;
The auxiliary steering controller is used for performing active steering control when the target braking force is judged to be larger than the maximum braking force, calculating an additional turning angle based on the additional yaw moment according to the geometric structure of the vehicle and the lateral deviation characteristics of the tire, setting a weight factor for coordinating differential braking control and active steering control, adjusting the additional turning angle and outputting steering angle control quantity.
Compared with the prior art, the invention has the following advantages:
(1) The failure control scheme provided by the invention can cover most of EMB system fault types, and can realize that different control strategies can be adopted for different faults subsequently by setting fault factors and fault codes to judge;
the wheels which can be braked normally are utilized for braking force reconstruction, and vehicle stability and braking control are realized under the condition that a redundant mechanism is not needed; the sliding film controller is used for carrying out subsequent fault-tolerant controller design by taking the yaw moment of the vehicle as a control target, so that the stability of the vehicle is further improved;
auxiliary steering control is introduced when braking force is insufficient, vehicle stability control is realized through direct yaw control under most conditions, steering is added when the braking force is insufficient, and vehicle stability is guaranteed.
(2) At present, most of vehicle brake-by-wire systems are EHB systems, and hydraulic structures are not completely removed, so that hydraulic redundancy is mostly adopted, and the vehicle brake-by-wire systems are not completely controlled by wires. The invention is based on the fault-tolerant control design of the four-wheel independent EMB line control motor system, all hydraulic pipelines are eliminated, a motor is used as a power source, and an electric signal is used for replacing a mechanical transmission mechanism to transmit braking information. The volume and the installation flexibility of the braking system can be effectively reduced, and the control sensitivity and the control accuracy of the braking system are greatly improved.
(3) Most of current schemes for improving the brake-by-wire safety are to add redundant devices, and the scheme can improve the reliability of the system, but greatly improve the manufacturing cost of the system. The invention performs coordination control of four-wheel braking force based on the working capacity of the original four-wheel braking module, and maximally utilizes the braking capacity of the original system.
(4) At present, a direct turn-off or switching redundancy backup device is generally adopted for a processing scheme of the failure of the brake-by-wire system, and the same control scheme is adopted for different types of failures. And the invention adopts different control schemes aiming at different types of faults, confirms the fault type through the failure judging module, and then selects the corresponding fault-tolerant control scheme. The strategy can effectively solve the influence of different faults on the vehicle braking system, so that a better control effect is achieved.
Drawings
Fig. 1 is a schematic flow chart of a single-wheel failure fault-tolerant control method for an automobile facing distributed drive-by-wire provided in an embodiment of the invention;
fig. 2 is a schematic diagram of an overall EMB system vehicle architecture according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a system failure control flow provided in an embodiment of the present invention;
FIG. 4 is a schematic diagram of a linear two-degree-of-freedom model according to an embodiment of the present invention;
fig. 5 is a schematic block diagram of a single-wheel failure fault-tolerant control method for an automobile facing distributed drive-by-wire provided in an embodiment of the invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the present invention, related terms are explained as follows:
EMB: electronic Mechanical Brake electromechanical brake system;
EHB: electronic Hydraulic Brake, electro-hydraulic braking system;
HARA: hazard Analysis and Risk Assessment, risk analysis and risk assessment;
ASIL: automotive Safety Integrity Level, a hybrid vehicle;
PID: proportionl-Integral-Derivative, proportional Integral control.
Example 1
The invention is directed to the new requirements put forward in the intelligent driving environment, and establishes an active fault-tolerant control method of the distributed line control brake system based on the four-wheel independent electronic mechanical brake system EMB. The control strategy mainly comprises two parts of system failure identification and failure control, and the safety and fault tolerance of the system are further improved through identification and system reconstruction of faults. And (3) taking the expected braking strength and the expected yaw rate of the vehicle braking as system control targets, reconstructing the braking force of the vehicle, adding auxiliary steering control when the braking force is insufficient, and ensuring the braking performance and the stability when the vehicle is in fault.
Specifically, as shown in fig. 1, the method comprises the following steps:
system failure identification step S1: acquiring a state signal of an automobile brake-by-wire system; obtaining fault factors respectively representing the fault type and the fault degree according to the actual braking force of the wheels and the expected braking force of the wheels in the state signals, thereby obtaining corresponding fault codes;
and a basic failure control step S2: according to the fault code, adopting a corresponding fault control strategy, reconstructing braking force of each wheel of the vehicle based on braking force balance, and performing primary braking control of single-wheel failure of the vehicle;
and a sliding film differential control step S3: loading the vehicle speed and the steering angle in the state signals into a linear two-degree-of-freedom automobile model based on the lateral force and the yaw moment to obtain an ideal yaw rate; according to the ideal yaw rate and the actual yaw rate, performing yaw moment control through a sliding film controller to obtain an additional yaw moment; distributing the additional yaw moment to the other wheels of the vehicle according to the failed wheels and the corresponding failure factors, and performing differential braking control;
auxiliary steering control step S4: judging whether the target braking force of each wheel is larger than the maximum braking force or not according to the braking force of each wheel and the additional yaw moment, if so, performing active steering control, calculating an additional turning angle based on the additional yaw moment according to the geometric structure of the vehicle and the tire cornering characteristics, setting a weight factor for coordinating differential braking control and active steering control, and adjusting the additional yaw moment to realize integral control for introducing auxiliary steering.
In the steps, the basic braking strength requirement and the braking balance requirement of the vehicle can be met through the basic failure control step; the sliding film differential control step is adopted to carry out subsequent fault-tolerant controller design by taking the yaw moment of the vehicle as a control target, so that the stability of the vehicle can be further improved; by introducing the auxiliary steering control step, the vehicle braking and stability control can be realized by utilizing the differential braking and steering cooperative control for the case where the required braking force exceeds the attachment limit.
The following is a detailed description.
1. Control object
Compared with the traditional braking system, the EMB system can realize interaction with a driving auxiliary function and four-wheel independent braking, can improve the applicability of the system applied to intelligent automobiles and the braking performance of the automobiles, and improves the stability and controllability of the automobiles, and is particularly composed of an electronic pedal simulator, a sensor group, a system control module, an actuator module, a communication network and a power supply system 6, wherein the basic architecture of the system is shown in figure 2.
2. General overview
The invention mainly aims at identifying the fault type through failure identification, obtaining a system fault factor and a fault code, and performing failure control of corresponding faults according to the result, wherein the failure control mainly comprises vehicle braking force reconstruction and auxiliary steering control when the braking force is insufficient. The invention takes the state signal of the brake-by-wire system as the system input, and obtains the system fault factor and the fault code after being processed by the failure identification module, thereby reflecting the type and degree of the system fault and determining to adopt the corresponding failure control strategy. The failure control module consists of a braking force symmetrical controller, a sliding film controller, a differential braking controller and an auxiliary steering controller 4, and different control strategies are adopted according to different faults, and a specific control flow chart is shown in fig. 3.
3. Detailed description of the steps
3.1 System failure identification step
3.1.1 failure identification Module
Because the system is four-wheel independent braking, the actual braking state of each wheel needs to be analyzed, and the invention introduces a fault factor lambda according to the relation between the actually detected wheel braking force and the target braking force 1_i And lambda (lambda) 2_i And the fault code characterizes the wheel braking state, and the system failure judgment is carried out. The design rules for the 2 fault factors are as follows:
λ 1_i representing the fault type, which is classified into 3 types of faults and 1 normal mode:
λ 2_i representing the fault degree, the calculation formula is as follows:
wherein i=fl/FR/RL/RR represents different wheels; f (F) xb_i Representing the actual braking force of the wheels; f (F) exb_i Indicating the desired braking force of the wheel.
In summary, according to the product of two fault factors, the fault mode and the actual braking moment can be basically determined, and the fault code E is respectively formulated for different faults i So as to facilitate the adoption of a corresponding fault control strategy.
(1)λ 1_i ·λ 2_i When=0, fault code E i =0, indicating no fault;
(2)λ 1_i ·λ 2_i when < 0, fault code E i =1, indicating that a braking force loss has occurred, including a braking failure and a partial loss of braking force, i.e., that-1. Ltoreq.lambda 1_i ·λ 2_i ＜0；
(3)0＜λ 1_i ·λ 2_i When < 2, fault code E i =2, representing that the actual braking force is greater than the expected braking force, and Namely F xb_i ＜3F exb_i When the actual braking torque exceeds the expected braking torque by 3 times or more, the actual braking torque is out of balance with the expected braking force due to overlarge phase difference, so that fault treatment is carried out according to sudden braking;
(4)2≤λ 1_i ·λ 2_i at the time, the fault code E i =3, it indicates that unexpected braking or an actual braking force is not less than three times the expected braking force.
The fault factor is the quantization of the detection result, and the value of the corresponding fault code can be obtained by judging the value of the product of the two fault factors, so that the specific fault type and the fault degree of the system are analyzed. And judging the failure of the system, and determining that the specific failure can select the corresponding failure control strategy is the basis of the subsequent fault-tolerant mechanism design.
3.1.2 failure control Module
Because the invention is based on a four-wheel independent braking architecture, the invention takes the failure of the left front wheel brake as an example, and utilizes the rest three wheels to carry out the whole vehicle braking force reconstruction algorithm design so as to meet the braking requirement and the stability requirement of the vehicle. For different types of fault, i.e. fault code E FL When = {1,2,3}, the corresponding system control policy is formulated:
(1)E FL when=1, it is explained that the braking force of the left front wheel is reduced, and at this time, the braking force is reduced and unbalanced, and the braking force of other three wheels is reconstructed according to the actual working condition;
(2)E FL When=2, other three-wheel braking forces are reconstructed to ensure the vehicle stability requirement;
(3)E FL when=3, it indicates that unexpected braking or unexpected large increase of braking force has occurred, and at this time, the adopted strategy is to disconnect the power of the brake actuator of the faulty wheel (left front wheel), convert the brake actuator into a braking force lost state, and execute the fault code E FL Three rounds of reconstruction operation at=1.
3.2, basic failure control step
3.2.1 basic brake force failure control strategy
When the braking force of the left front wheel is lost or the braking force of a certain range is increased unexpectedly, the difference between the expected total braking force and the actual total braking force is as follows:
in order to meet the braking strength requirement and meet the vehicle stability at the same time, the rest three wheels are subjected to preliminary braking force reconstruction based on braking force balance, and the specific distribution rule is as follows:
according to the distribution rule, the actual total braking force is the same as the expected braking force, namely the expected braking requirement of the vehicle is met. In addition, the strategy can simultaneously realize that the braking forces of the front axle wheel, the rear axle wheel and the left and right side wheels of the vehicle are equal, and the braking force balance requirement is met, namely:
f in the formula xb_ls And F xb_rs Representing the actual braking forces of the left and right wheels, respectively.
When |lambda 1_FL ·λ 2_FL When the I is smaller, the actual braking force is closer to the expected braking force, the basic braking strength requirement and the braking balance requirement of the vehicle can be met through the basic braking force failure control strategy, but when the lost or increased braking force is overlarge and the vertical loads of four wheels are transferred, the vehicle can generate a severe yaw moment caused by unbalanced braking force at the moment of failure, and at the moment, the vehicle is easy to generate instability and deviation. Therefore, after the basic regulation and control of the symmetrical braking force is carried out, in order to improve the stability of the vehicle and reduce the yaw moment of the vehicle, the yaw moment of the vehicle is used as a control target to carry out subsequent fault-tolerant controller design.
3.3 step of differential control of synovial Membrane
3.3.1 additional yaw moment calculation
The relevant parameters of the yaw rate of the vehicle include longitudinal speed, steering wheel input rotation angle and its change rate, vehicle yaw rate deviation, vehicle centroid side deviation and the like, and since the main purpose of the present invention is to adjust the yaw moment of the vehicle for stability control, for convenience of research, the research of additional yaw moment is performed in a linear two-degree-of-freedom model, as shown in fig. 4.
After the additional yaw moment is introduced, the two-degree-of-freedom lateral force and yaw moment calculation formula is as follows:
the slip angle in the model is:
the cornering force is the product of the cornering angle and the cornering stiffness of the tyre, i.e.:
middle cornering stiffness C f And C r The value is obtained by fitting a cornering stiffness curve calculated under different vertical loads according to a magic tire formula, and when the vertical loads are different, the cornering stiffness is also different.
Simultaneous availability:
processing the above equation, the motion differential equation of the linear two-degree-of-freedom automobile can be obtained:
when the vehicle is in steady state, both the centroid slip angle and yaw rate gain are 0, i.eSubstituting the above to obtain ideal yaw rate and centroid slip angle: />
In the above formula, K is a stability factor, and can represent the steady state response condition of the vehicle, and is calculated as follows:
The parameters in the above formulas correspond to those shown in table 1.
TABLE 1 vehicle dynamics model parameter Table
| Parameter name | (symbol) | Unit (B) |
| Front axle side bias force | F f | N |
| Rear axle side bias | F r | N |
| Front axle slip angle | α f | rad |
| Rear axle slip angle | α r | rad |
| Vehicle speed | V | m/s |
| Longitudinal vehicle speed | V x | m/s |
| Transverse vehicle speed | V y | m/s |
| Yaw rate | ω | rad/s |
| Front axis to centroid distance | L a | m |
| Rear axle to centroid distance | L b | m |
| Distance from front axle to rear axle | L | m |
| Yaw stiffness of front axle | C f | N/rad |
| Rear axle yaw stiffness | C r | N/rad |
| Moment of inertia about the z-axis | I z | kg*m 2 |
| Front wheel steering angle | δ | rad |
| Centroid slip angle | β | rad |
| Whole vehicle quality | M | kg |
At present, a sliding film variable structure control algorithm is widely applied to yaw moment control due to good robustness and accuracy, and the control algorithm is adopted for tracking an ideal yaw moment.
The slip film controller needs to set the slip film surface, because the ideal yaw rate is to be tracked, the slip film surface is set as the difference between the ideal yaw rate and the actual yaw rate in the present invention:
s＝ω-ω exp
and carrying out differential treatment on the obtained product to obtain:
the method comprises the following steps:
order theSubstituting the above, the additional yaw can be calculated:
wherein, xi is the synovial membrane control parameter.
Since the tire is subjected to lateral forces limited by the road attachment coefficient, the ideal yaw rate and centroid slip angle of the vehicle will be constrained as follows:
the method comprises the following steps:
3.3.2 differential brake control strategy
The yaw moment of the vehicle can be effectively controlled by utilizing three-wheel braking force reconstruction to realize differential braking, and the longitudinal force of the tire can generate the yaw moment of the vehicle around the z axis to realize additional yaw.
From the kinematic relationship, it is possible to obtain:
in the above formula, B is the tread of the left and right wheels, and DeltaF x_total To achieve the total longitudinal force of the yaw moment additional yaw moment, when the additional yaw moment is distributed to four wheels, there are:
when the left front wheel fails, accurate braking control cannot be performed on the braking force of the left front wheel, and three-wheel differential braking is required, namely:
to increase the braking efficiency, the additional longitudinal force value of the left front wheel is assigned to the remaining three wheels according to different fault conditions:
(1) When lambda is 1_FL ·λ 2_FL < 0, i.e. left front wheel generationWhen the braking force is lost:
after the braking force of the left front wheel is lost, the braking force of the right front wheel and the braking force of the left rear wheel are increased, and the braking force of the right rear wheel is reduced through the symmetric regular distribution regulation and control of the braking force. To improve the utilization rate of ground attachment while ensuring good drivability, the left front wheel compensation braking force is distributed to the rear wheels:
(2) When 2 > lambda 1_FL ·λ 2_FL > 0, i.e. when the left front wheel braking force is too great:
after the symmetrical braking force control, the braking force of the right rear wheel is improved, the braking forces of the right front wheel and the left rear wheel are reduced, at the moment, the compensation braking forces of the right front wheel and the left rear wheel are adjusted, and the three-wheel braking force is set as:
The calculated target braking force can achieve the desired additional yaw moment of the vehicle when three-wheel differential braking is performed, but in other extreme situations, such as on icy or snowy roads or emergency braking, it may occur that the target braking force exceeds the road attachment limit. In such a scenario, the actual braking force deviates from the target braking force, and ideal yaw moment control cannot be achieved, so that judgment and solution are required for the scenario.
3.4, auxiliary steering control step
3.4.1 wheel attachment limit constraints
Three-wheel differential braking control is achieved by relying on the longitudinal forces generated by the friction between the tires and the ground, and the additional yaw that differential braking can provide is limited by the limits of friction due to the limits of friction.
The road adhesion coefficient mu limits the maximum friction between the vehicle and the road, so that the stress of the wheels needs to meet the constraint condition:
F xb_i 2 +F y_i 2 ≤(μ·F z_i ) 2
in a braking scenario, the tire lateral force is much smaller than the longitudinal force, and the lateral force in the above equation can be ignored, resulting in a simplified wheel longitudinal force constraint equation:
|F xb_i |≤μ·F z_i ＝|F xb_max_i |
f in the above xb_i For the wheel braking force limit, μ is the ground attachment coefficient, F z_i The vertical load of the wheels is described in detail in chapter three.
When the target braking force obtained by the differential braking is not greater than the maximum braking force, the target braking force is:
F xb_obj_i ＝F xb_i +ΔF x_i ′,|F xb_obj_i |≤|F xb_max_i |
when |F xb_obj_i |＞|F xb_max_i When the vehicle is in a state, the stability control requirement cannot be met only by virtue of differential braking, and a steering system is required to be introduced to ensure the stability of the vehicle.
3.4.2 auxiliary steering controller design
When the wheel braking force approaches to the ground attachment limit, the system performs active steering control, calculates, and avoids severe oscillation of the yaw moment of the vehicle.
According to the controller design, partial additional transverse moment is realized through differential braking, and if steering control is added, coordination control between the differential braking and active steering is needed. Introducing a weight factor sigma to represent the control weights of two control modes, wherein the values of the control weights are related to the actual braking force and the target braking force, and the calculation formula is as follows:
in combination with the above, the overall yaw rate control method is as follows:
m in the formula b_b Representing yaw moment generated by differential braking; ΔM b_s The yaw moment generated by adjusting the front wheel steering angle is obtained according to the geometric structure of the vehicle and the cornering characteristics of the tires, and the relation between the yaw moment and the additional corners is:
c in the formula f The front axle cornering stiffness has been found in the previous tire model.
In summary, the additional yaw moment may be implemented as follows when the target braking force is greater than the maximum braking force that can be provided:
wherein delta is the actual front wheel steering angle; k (k) s Is the steering ratio between the steering wheel angle and the front wheel angle; delta s Is the steering wheel angle.
4. Principle of integration
The overall schematic block diagram of the scheme of the invention is shown in fig. 5, after receiving a brake occurrence signal, the system firstly distributes four-wheel brake torque according to a four-wheel distribution strategy, if the system fails, failure control is activated, and basic brake force reconstruction control is carried out according to a failure judgment result. During this period, if the required braking force exceeds the adhesion limit, assist steering control is introduced, and vehicle braking and stability control is achieved using differential braking and steering cooperative control.
The foregoing description of the embodiments of the method further describes the embodiments of the present invention through system embodiments.
The embodiment also provides a distributed drive-by-wire (drive-by-wire) oriented automobile single-wheel failure fault-tolerant control system, which comprises the following steps:
the system failure identification module is used for acquiring a state signal of the automobile brake-by-wire system; obtaining fault factors respectively representing the fault type and the fault degree according to the actual braking force of the wheels and the expected braking force of the wheels in the state signals, thereby obtaining corresponding fault codes;
The basic failure control module is used for adopting a corresponding failure control strategy according to the failure code, reconstructing braking force of each wheel of the vehicle based on braking force balance, and performing single-wheel failure primary braking control of the vehicle;
the sliding film differential control module is used for loading a linear two-degree-of-freedom automobile model based on lateral force and yaw moment according to the speed and the steering angle in the state signal to obtain an ideal yaw rate; according to the ideal yaw rate and the actual yaw rate, performing yaw moment control through a sliding film controller to obtain an additional yaw moment; distributing the additional yaw moment to the other wheels of the vehicle according to the failed wheels and the corresponding failure factors, and performing differential braking control;
the auxiliary steering control module is used for judging whether the target braking force of each wheel is larger than the maximum braking force according to the braking force of each wheel and the additional yaw moment, if so, performing active steering control, calculating the additional turning angle based on the additional yaw moment according to the geometric structure of the vehicle and the lateral deviation characteristics of the tire, setting a weight factor for coordinating the differential braking control and the active steering control, and adjusting the additional yaw moment and the additional turning angle to realize integral control for introducing auxiliary steering.
Optionally, the basic failure control module is a basic failure controller, and the basic failure controller is used for adopting a corresponding failure control strategy according to the failure code, reconstructing braking force of each wheel of the vehicle based on braking force balance, and performing single-wheel failure primary braking control of the vehicle;
the sliding film differential control module comprises a sliding film controller and a differential braking controller,
the sliding film controller is used for comparing the ideal yaw rate calculated by the linear two-degree-of-freedom automobile model with the actual yaw rate and performing yaw moment control to obtain an additional yaw moment;
the differential braking controller is used for controlling braking force according to the braking force reconstructed by the basic failure control module, further distributing the additional yaw moment to the rest wheels of the vehicle, and performing differential braking control based on the weight factors fed back by the auxiliary steering control module;
the auxiliary steering control module includes an adhesion limit determination module and an auxiliary steering controller,
an attachment limit judgment module for judging whether the target braking force of each wheel is greater than the maximum braking force according to the braking force of each wheel and the additional yaw moment;
and the auxiliary steering controller is used for performing active steering control when judging that the target braking force is greater than the maximum braking force, calculating an additional turning angle based on the additional yaw moment according to the geometric structure of the vehicle and the tire cornering characteristics, setting a weight factor for coordinating the differential braking control and the active steering control, adjusting the additional turning angle and outputting steering angle control quantity.
The specific content and the beneficial effects of the system of the present application can be referred to the above method embodiments, and are not described herein.
The foregoing describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention by one of ordinary skill in the art without undue burden. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.
Claims (10)
1. A distributed line control action-oriented automobile single-wheel failure fault-tolerant control method is characterized by comprising the following steps:
acquiring a state signal of an automobile brake-by-wire system; obtaining fault factors respectively representing the fault type and the fault degree according to the actual braking force of the wheels and the expected braking force of the wheels in the state signals, so as to obtain corresponding fault codes;
according to the fault code, adopting a corresponding fault control strategy, reconstructing braking force of each wheel of the vehicle based on braking force balance, and performing single-wheel failure preliminary braking control of the vehicle;
Loading a linear two-degree-of-freedom automobile model based on lateral force and yaw moment according to the speed and the steering angle in the state signal, and obtaining an ideal yaw rate; according to the ideal yaw rate and the actual yaw rate, performing yaw moment control through a sliding film controller to obtain an additional yaw moment; distributing the additional yaw moment to the other wheels of the vehicle according to the failed wheels and the corresponding failure factors, and performing differential braking control;
judging whether the target braking force of each wheel is larger than the maximum braking force or not according to the braking force of each wheel and the additional yaw moment, if so, performing active steering control, calculating an additional turning angle based on the additional yaw moment according to the geometric structure of the vehicle and the tire cornering characteristics, setting a weight factor for coordinating differential braking control and active steering control, and adjusting the additional yaw moment and the additional turning angle to realize integral control for introducing auxiliary steering.
2. The distributed brake-by-wire oriented single wheel failure fault-tolerant control method of claim 1, wherein said fault factor comprises a fault factor λ 1_i And a fault factor lambda 2_i The fault factor lambda 1_i For representing the type of failure of wheel i, said failure factor lambda 1_i The assigned expression of (2) is:
the fault factor lambda 2_i For representing the degree of failure of wheel i, said failure factor lambda 2_i The assigned expression of (2) is:
wherein i=fl/FR/RL/RR respectively represents a front axle left wheel, a front axle right wheel, a rear axle left wheel, and a rear axle right wheel, F xb_i For the actual braking force of wheel i, F exb_i Is the desired braking force for wheel i.
3. The distributed brake-by-wire oriented single wheel failure fault-tolerant control method of claim 2, wherein if the front axle left wheel is a failed wheel, the distribution expression for reconstructing the braking force of each wheel of the vehicle based on the braking force balance comprises:
wherein F is dxb_FL Braking force distributed for left wheel of front axle, F exb_f Lambda is the desired braking force of the front axle 1_FL Lambda is the failure type of the left wheel of the front axle 2_FL F is the failure degree of the left wheel of the front axle dxb_FR Braking force distributed for front axle right wheel, F exb_r F for the desired braking force of the rear axle dxb_RL Braking force distributed for left wheel of rear axle, F dxb_RR The rear axle right wheel is assigned a rear braking force.
4. The distributed brake-by-wire oriented single-wheel failure fault-tolerant control method of the automobile according to claim 1, wherein the expression of the motion differential equation of the linear two-degree-of-freedom automobile model based on the lateral force and the yaw moment is:
In the method, in the process of the invention,for centroid cornering angle gain +.>For yaw rate gain, C f For the yaw rigidity of the front axle C r The rigidity of the lateral deflection of the rear axle is M, the mass of the whole vehicle is V x Is the longitudinal speed, beta is the centroid slip angle, L a For the front axis to centroid distance, L b For the rear axle to centroid distance, ω is yaw rate, δ is front wheel angle, I z To rotate about the z-axis, ΔM b Is an additional yaw moment;
substituting the centroid slip angle and the yaw rate gain of 0 into the motion differential equation to obtain an ideal yaw rate calculation expression as follows:
wherein omega is exp For an ideal yaw rate, K is the stability factor and L is the front-to-rear axis distance.
5. The distributed brake-by-wire oriented fault-tolerant control method for single wheel failure of an automobile of claim 4, wherein the yaw moment control by the slip film controller comprises the following steps:
setting a difference value between the ideal yaw rate and the actual yaw rate as a sliding film surface of a sliding film controller, and calculating by the sliding film controller to obtain a calculation expression of the additional yaw moment, wherein the calculation expression is as follows:
in the method, in the process of the invention,to the ideal yaw rate after the differentiation process omega exp Is an ideal yaw rate, and ζ is a slip film control parameter;
In the control process of the synovial membrane controller, the constraint of the ideal yaw rate and the ideal centroid slip angle comprises the following steps:
wherein omega is max Is the maximum value of ideal yaw rate, beta max Is the maximum value of ideal centroid slip angle.
6. A distributed brake-by-wire oriented single wheel failure fault tolerant control method according to claim 2, characterized in that the specific process of distributing the additional yaw moment to the remaining wheels of the vehicle comprises:
if the left wheel of the front axle is a fault wheel and lambda 1_FL ·λ 2_FL When < 0, the calculated expression for assigning the additional yaw moment to the remaining wheels of the vehicle is:
wherein DeltaF x_FR ' is the longitudinal force of the front axle right wheel after being distributed, deltaF x_FR To achieve the yaw moment additional yaw moment front axle right wheel longitudinal force ΔM b For additional yaw moment, L b B is the wheel distance of the left and right wheels, L a Delta is the front wheel angle, delta F, which is the distance from the front axle to the center of mass x_RL ' is the distributed rear axle left wheel longitudinal force, ΔF x_RL To achieve yaw moment additional yaw moment rear axle left wheel longitudinal force, ΔF x_FL To achieve yaw moment additional yaw moment front axle left wheel longitudinal force, ΔF x_RR ' is the distributed rear axle right wheel longitudinal force, ΔF x_RR To realize the transverseSwing moment adds the rear axle right wheel longitudinal force of yaw moment;
if the left wheel of the front axle is a fault wheel and 2 is more than lambda 1_FL ·λ 2_FL At > 0, the calculated expression for assigning the additional yaw moment to the remaining wheels of the vehicle is:
7. the distributed brake-by-wire oriented single-wheel failure fault-tolerant control method of the automobile according to claim 1, wherein if the front axle left wheel is a faulty wheel, the calculation expression of the weight factors for coordinating the differential braking control and the active steering control is:
wherein sigma is a weight factor, F xb_obj_i For the target braking force of the wheel i, F xb_max_i For maximum braking force of wheel i, F xb_i The actual braking force of the wheel i is FR/RL/RR respectively a front axle right wheel, a rear axle left wheel and a rear axle right wheel;
the additional yaw moment DeltaM b The control mode of (2) is adjusted as follows:
wherein DeltaM b_b For yaw moment generated by differential braking ΔM b_s For the yaw moment generated by adjusting the front wheel rotation angle, the calculation expression of the additional rotation angle is as follows:
in the middle of，L a For the rear axle to centroid distance C f Is the yaw stiffness of the front axle.
8. The distributed brake-by-wire oriented single wheel failure fault-tolerant control method of claim 7, wherein when the target braking force of the wheels is greater than the maximum braking force, the calculated distribution expression of the additional yaw moment is:
Wherein DeltaF xc_FR To assist the steering front axle right wheel longitudinal force ΔF xc_RL To assist the rear axle left wheel longitudinal force after steering ΔF xc_RR To assist the longitudinal force of the rear axle right wheel after steering, L b The distance from the rear axle to the mass center is B, the wheel distance of left and right wheels, delta is the front wheel corner, k s Is the steering ratio between the steering wheel angle and the front wheel angle; delta s Is the steering wheel angle.
9. The distributed line control action-oriented automobile single-wheel failure fault-tolerant control system is characterized by comprising the following steps of:
the system failure identification module is used for acquiring a state signal of the automobile brake-by-wire system; obtaining fault factors respectively representing the fault type and the fault degree according to the actual braking force of the wheels and the expected braking force of the wheels in the state signals, so as to obtain corresponding fault codes;
the basic failure control module is used for adopting a corresponding failure control strategy according to the failure code, reconstructing braking force of each wheel of the vehicle based on braking force balance, and performing single-wheel failure primary braking control of the vehicle;
the sliding film differential control module is used for loading a linear two-degree-of-freedom automobile model based on lateral force and yaw moment according to the speed and the steering angle in the state signal to obtain an ideal yaw rate; according to the ideal yaw rate and the actual yaw rate, performing yaw moment control through a sliding film controller to obtain an additional yaw moment; distributing the additional yaw moment to the other wheels of the vehicle according to the failed wheels and the corresponding failure factors, and performing differential braking control;
The auxiliary steering control module is used for judging whether the target braking force of each wheel is larger than the maximum braking force according to the braking force of each wheel and the additional yaw moment, if so, performing active steering control, calculating the additional turning angle based on the additional yaw moment according to the geometric structure of the vehicle and the lateral deviation characteristics of the tire, setting a weight factor for coordinating the differential braking control and the active steering control, and adjusting the additional yaw moment and the additional turning angle to realize integral control for introducing auxiliary steering.
10. The distributed brake-by-wire oriented single-wheel failure fault-tolerant control system of the automobile according to claim 9, wherein the basic failure control module is a basic failure controller, and the basic failure controller is used for adopting a corresponding failure control strategy according to the failure code, reconstructing braking force of each wheel of the automobile based on braking force balance, and performing initial braking control of single-wheel failure of the automobile;
the sliding film differential control module comprises a sliding film controller and a differential braking controller,
the sliding film controller is used for comparing the ideal yaw rate calculated by the linear two-degree-of-freedom automobile model with the actual yaw rate and performing yaw moment control to obtain an additional yaw moment;
The differential braking controller is used for controlling braking force according to the braking force reconstructed by the basic failure control module, further distributing the additional yaw moment to the rest wheels of the vehicle, and performing differential braking control based on the weight factors fed back by the auxiliary steering control module;
the auxiliary steering control module includes an attachment limit determination module and an auxiliary steering controller,
the attachment limit judging module is used for judging whether the target braking force of each wheel is larger than the maximum braking force according to the braking force of each wheel and the additional yaw moment;
the auxiliary steering controller is used for performing active steering control when the target braking force is judged to be larger than the maximum braking force, calculating an additional turning angle based on the additional yaw moment according to the geometric structure of the vehicle and the lateral deviation characteristics of the tire, setting a weight factor for coordinating differential braking control and active steering control, adjusting the additional turning angle and outputting steering angle control quantity.
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| CN117162995A (en) * | 2023-10-24 | 2023-12-05 | 苏州坐标系智能科技有限公司 | Drive-by-wire chassis system and dynamic control method thereof |
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2023
- 2023-04-28 CN CN202310478609.9A patent/CN116552485A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117162995A (en) * | 2023-10-24 | 2023-12-05 | 苏州坐标系智能科技有限公司 | Drive-by-wire chassis system and dynamic control method thereof |
| CN117162995B (en) * | 2023-10-24 | 2024-06-07 | 苏州坐标系智能科技有限公司 | Drive-by-wire chassis system and dynamic control method thereof |
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