CN113147735B - Differential braking/driving coordination rollover prevention control system and control method thereof - Google Patents

Differential braking/driving coordination rollover prevention control system and control method thereof Download PDF

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CN113147735B
CN113147735B CN202110406616.9A CN202110406616A CN113147735B CN 113147735 B CN113147735 B CN 113147735B CN 202110406616 A CN202110406616 A CN 202110406616A CN 113147735 B CN113147735 B CN 113147735B
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wheel
unit
rear wheel
longitudinal force
front wheel
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CN113147735A (en
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王骏骋
吕林峰
陈士安
费相宜
任洁雨
李浩然
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Zhejiang Sci Tech University ZSTU
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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, or advanced driver assistance systems for ensuring comfort, stability and safety or drive control systems for propelling or retarding the vehicle
    • B60W30/02—Control of vehicle driving stability
    • B60W30/04—Control of vehicle driving stability related to roll-over prevention
    • 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
    • B60W10/04—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units
    • B60W10/08—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units including control of electric propulsion units, e.g. motors or generators
    • 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
    • B60W10/184—Conjoint control of vehicle sub-units of different type or different function including control of braking systems with wheel brakes
    • 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, or advanced driver assistance systems for ensuring comfort, stability and safety or drive control systems for propelling or retarding the vehicle
    • B60W30/02—Control of vehicle driving stability
    • B60W30/04—Control of vehicle driving stability related to roll-over prevention
    • B60W2030/043—Control of vehicle driving stability related to roll-over prevention about the roll axis
    • 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
    • B60W2520/00—Input parameters relating to overall vehicle dynamics
    • B60W2520/10—Longitudinal speed
    • 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
    • B60W2520/00—Input parameters relating to overall vehicle dynamics
    • B60W2520/10—Longitudinal speed
    • B60W2520/105—Longitudinal acceleration
    • 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
    • B60W2520/00—Input parameters relating to overall vehicle dynamics
    • B60W2520/12—Lateral speed
    • B60W2520/125—Lateral acceleration
    • 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
    • B60W2520/00—Input parameters relating to overall vehicle dynamics
    • B60W2520/28—Wheel speed
    • 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
    • B60W2540/00—Input parameters relating to occupants
    • B60W2540/10—Accelerator pedal position
    • 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
    • B60W2540/00—Input parameters relating to occupants
    • B60W2540/12—Brake pedal position
    • 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
    • B60W2710/00—Output or target parameters relating to a particular sub-units
    • B60W2710/08—Electric propulsion units
    • B60W2710/083—Torque
    • 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
    • B60W2710/00—Output or target parameters relating to a particular sub-units
    • B60W2710/18—Braking system

Abstract

A differential braking/driving coordination rollover prevention control system comprises a sensor unit, a signal acquisition and processing unit, a rollover early warning unit, an optimal counter balance moment calculation unit, an attachment coefficient identification unit, a vehicle control unit VCU, a differential braking/driving coordination control unit, a left front wheel motor controller, a left front wheel disc brake, a left front wheel hub motor, a right front wheel motor controller, a right front wheel disc brake, a right front wheel hub motor, a left rear wheel motor controller, a left rear wheel disc brake, a left rear wheel hub motor, a right rear wheel motor controller, a right rear wheel disc brake and a right rear wheel hub motor. The invention provides a differential braking/driving coordination anti-rollover control system and a control method thereof, fully considers the influence of a road adhesion coefficient on the differential braking anti-rollover control effect, and has important research significance for improving the driving safety of vehicles.

Description

Differential braking/driving coordination rollover prevention control system and control method thereof
Technical Field
The invention relates to the technical field of automobile active rollover prevention control, in particular to a differential braking/driving coordination rollover prevention control system and a control method thereof.
Background
The distributed driving electric automobile is one of high and new technology carriers integrating the advantages of zero emission, high transmission efficiency, flexible control and the like under the trend of automobile electromotion development. However, as the vehicle speed is faster and faster, the rollover accident rate is increased, and the distributed drive electric vehicle also faces the complex dynamic instability control problem.
Compared with passive rollover prevention measures, the active rollover prevention control technology has a more ideal rollover prevention control effect, wherein the differential braking technology rollover prevention control technology is a typical vehicle active rollover prevention control technology. The essence of the differential braking rollover prevention control is that a braking system applies braking force to corresponding wheels to generate anti-yaw moment acting on a vehicle to reduce the yaw velocity, so that the vehicle is recovered to a stable state. For example, application No. 2019101350310 proposes a vehicle roll and yaw motion control system method based on differential braking and active suspension, and an automobile roll motion and yaw motion controller is designed to solve suspension control force and differential braking moment according to parameters such as automobile lateral acceleration, yaw velocity tracking error and the like, but the invention does not consider the influence of a road adhesion coefficient on the differential braking rollover prevention control effect, and when the road adhesion coefficient is lower in the actual driving working condition, the road adhesion coefficient is possibly limited by a maximum braking force limit value provided by the ground and cannot provide enough yaw moment to improve the rollover prevention control effect of the vehicle, so that potential rollover safety hazards are caused; furthermore, it is known from the analysis of the longitudinal dynamics of the vehicle that active rollover prevention control by applying a braking force causes a loss of the vehicle speed.
Disclosure of Invention
The invention provides a differential braking/driving coordination anti-rollover control system and a control method thereof, aiming at the technical problems that the influence of a road adhesion coefficient on an anti-rollover control effect cannot be fully considered in the implementation process of the differential braking anti-rollover control of the existing distributed drive electric automobile and the running speed loss of the automobile is caused by the fact that the differential braking control is implemented independently.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a differential braking/driving coordination rollover prevention control system comprises a sensor unit, a signal acquisition and processing unit, a rollover early warning unit, an optimal counter-balancing swing moment calculation unit, an attachment coefficient identification unit, a vehicle control unit VCU, a differential braking/driving coordination control unit, a left front wheel motor controller, a left front wheel disc brake, a left front wheel hub motor, a right front wheel motor controller, a right front wheel disc brake, a right front wheel hub motor, a left rear wheel motor controller, a left rear wheel disc brake, a left rear wheel hub motor, a right rear wheel motor controller, a right rear wheel disc brake and a right rear wheel hub motor, wherein the sensor unit is connected with the signal acquisition and processing unit, the signal acquisition and processing unit is respectively connected with the rollover early warning unit, the optimal counter-balancing swing moment calculation unit and the attachment coefficient identification unit, the rollover early warning unit is connected with the vehicle control unit VCU, the VCU, the optimal counter balance moment calculation unit and the attachment coefficient identification unit are all connected with the differential braking/driving coordination control unit;
the sensor unit comprises a vehicle speed sensor for acquiring the running speed v of the vehicle and a sensor unit for acquiring the speed omega of the vehicleiAutomobile wheel speed sensor for acquiring automobile longitudinal acceleration axLongitudinal acceleration sensor for acquiring transverse acceleration a of automobileyThe lateral acceleration sensor is used for acquiring the yaw angular velocity omega of the automobilerYaw angular velocity sensor, suspended mass roll angle sensor for measuring suspended mass roll angle phi, suspension mass roll angle velocity sensor for measuring suspended mass roll angle velocity
Figure BDA0003022617280000031
Suspension mass roll angular velocity sensor for measuring suspension mass roll angular acceleration
Figure BDA0003022617280000032
The suspension mass roll angle acceleration sensor and the driving/braking pedal signal sensor are used for collecting pedal signals of a driver;
the differential braking/driving coordination control unit comprises a tire vertical load calculation unit, a tire maximum longitudinal force calculation unit, a wheel motion form determination unit and an optimal counter balance moment distribution unit;
the sensor unit inputs the acquired data into the signal acquisition and processing unit, and the signal acquisition and processing unit inputs the transverse acceleration a of the automobileyThe suspension mass roll angle phi is input into the rollover early warning unit to judge whether the automobile has rollover danger, and if the rollover early warning unit judges that the automobile has rollover danger, the rollover early warning unit outputs a danger signal to the whole automobile controlThe VCU and the VCU output signals to start the differential braking/driving coordination control unit, and the signal acquisition and processing unit acquires the longitudinal acceleration a of the automobilexAutomobile yaw angular velocity omegarSuspension mass roll angular velocity
Figure BDA0003022617280000033
Suspension mass roll acceleration
Figure BDA0003022617280000034
The moment is input into an optimal counter-balance moment calculation unit, the optimal counter-balance moment calculation unit outputs an optimal counter-balance moment delta M and inputs the optimal counter-balance moment delta M into a wheel motion form determination unit, meanwhile, a signal processing unit inputs a vehicle control unit VCU (vehicle control unit) to a wheel motion form determination unit, the wheel motion form determination unit outputs wheel motion form results to an optimal counter-balance moment distribution unit, and an adhesion coefficient identification unit calculates adhesion coefficients mu of all wheels under respective slip rates lambdai(lambda), inputting the result into a tire maximum longitudinal force calculation unit, and enabling a vehicle control unit VCU to calculate the vehicle acceleration axInputting the vertical loads into a tire vertical load calculation unit which calculates the vertical loads F of the wheelszi(i ═ 1, 2, 3, 4, where 1 represents the front left wheel, 2 represents the front right wheel, 3 represents the rear left wheel, and 4 represents the rear right wheel) is input to the tire maximum longitudinal force calculation unit, which calculates the maximum longitudinal force F that can be provided by each tirexi_max(i ═ 1, 2, 3, 4, where 1 represents the front left wheel, 2 represents the front right wheel, 3 represents the rear left wheel, and 4 represents the rear right wheel), the results are input to the optimal counter-balance moment distribution unit, which distributes the moment in accordance with the maximum longitudinal force Fxi_maxSending an adjusting signal to a wheel motion form determining unit, inputting an adjusted wheel motion form result into an optimal counter-balancing pendulum moment distribution unit by the wheel motion form determining unit, inputting a final wheel longitudinal force distribution result into a vehicle control unit VCU (vehicle control unit), and controlling a left front wheel motor controller, a right front wheel motor controller, a left rear wheel motor controller and a right rear wheel motor controller by the vehicle control unit VCUThe controller enables the left front wheel hub motor, the right front wheel hub motor, the left rear wheel hub motor and the right rear wheel hub motor to output torque and controls the left front wheel disc brake, the right front wheel disc brake, the left rear wheel disc brake and the right rear wheel disc brake to work to provide braking torque.
A control method of a differential braking/driving coordination rollover prevention control system comprises the following steps:
step 1) determining whether the automobile has rollover danger or not, and whether differential braking/driving rollover prevention control is started or not
The signal acquisition processing unit acquires the transverse acceleration a of the automobile through the sensor unityAnd the suspension mass roll inclination angle phi sends data to the rollover early warning unit, and the lateral load transfer rate LTR is calculated according to the following formula:
Figure BDA0003022617280000041
in the formula, m is the mass of the whole automobile; m issIs a suspended mass; h is the distance between the center of mass of the suspended mass and the roll axis; h isrThe distance between the roll center and the ground; g is the acceleration of gravity; b is a wheel track;
defining the LTR threshold LTR of an automobiletWhen the LTR is more than or equal to 0.8, the vehicle is judged to have a rollover risk, and the vehicle control unit VCU sends out a command to enable the differential braking/driving coordination control unit to work to start the differential braking/driving rollover prevention control; when the | LTR | is less than 0.8, the VCU of the vehicle controller controls the sensor unit to repeatedly collect data to calculate the transverse load transfer rate LTR;
step 2) initial determination of the wheel movement pattern and the distribution of the wheel braking or driving force
The optimal counter balance pendulum moment unit outputs an optimal counter balance pendulum moment delta M and inputs the optimal counter balance pendulum moment delta M to the wheel motion form determining unit, and the vehicle control unit VCU outputs a driver pedal signal to the wheel motion form determining unit; the optimal counter balance pendulum moment distribution unit distributes the longitudinal force of the automobile tire according to the wheel motion form determined by the wheel motion form determination unit, defines the advancing direction of the wheel as positive, and distributes the magnitude of the longitudinal force according to the following formula:
Figure BDA0003022617280000051
in the formula, Fx1Is the left front wheel longitudinal force; fx2Is the right front wheel longitudinal force; fx3Is the left rear wheel longitudinal force; fx4Is the right rear wheel longitudinal force;
step 3) adjustment of the wheel movement pattern and redistribution of the wheel braking or driving force
The signal acquisition processing unit acquires the longitudinal acceleration a of the automobilexInputting the acceleration to a VCU of the vehicle controller, and enabling the VCU of the vehicle controller to convert the longitudinal acceleration axInputting the vertical load into a tire vertical load calculation unit, and calculating the current vertical load F of each wheelziThe calculation formula is as follows:
Figure BDA0003022617280000052
in the formula, Fz1Vertical load of the left front wheel; fz2Is the right front wheel vertical load; fz3Vertical load for the left rear wheel; fz4Is the vertical load of the right rear wheel; a is the distance from the center of the front wheel to the center of mass of the automobile; b is the distance from the center of the rear wheel to the center of mass of the automobile; h is a total ofgThe height of the mass center of the whole vehicle is;
the signal acquisition and processing unit acquires the speed v of the automobile and the speed omega of each wheeliLongitudinal acceleration a of the vehiclexThe adhesion coefficient is input to an adhesion coefficient identification unit which identifies the adhesion coefficient mu at the current slip rate of each wheeli(lambda) is input into a tire maximum longitudinal force calculation unit which calculates the maximum longitudinal force F which can be provided by the wheel to which the longitudinal force has been distributed under the constraint conditions of vertical load and adhesion coefficientxi_maxThe calculation formula is as follows:
Fxi_max＝μi(λ)Fzi (4)
in the formula, mui(lambda) is the wheel adhesion coefficient,i＝1，2，3，4；Fzifor wheel vertical loads, i is 1, 2, 3, 4;
comparing the force of wheel under braking or driving action distributed according to the pedal signal of driver and optimal counter-pendulum moment with the maximum longitudinal force (braking or driving force) provided by the wheel under the constraint of vertical load and adhesion coefficient, if all the wheel with applied longitudinal force satisfies the condition Fxi≤Fxi_max(i is 1, 3 or 2, 4, where 1 represents the front left wheel, 2 represents the front right wheel, 3 represents the rear left wheel, and 4 represents the rear right wheel), the differential braking/driving coordination control unit outputs the primarily distributed longitudinal force of the wheels to the vehicle control unit VCU; if the wheel stress magnitude of the primary distribution longitudinal force exists Fxi＞Fxi_maxAdjusting the motion form of the wheels;
the redistribution of braking or driving force is performed according to the following formula:
Figure BDA0003022617280000061
of formula (II) F'x1Is the redistributed left front wheel longitudinal force, F'x2Is the redistributed front right wheel longitudinal force, F'x3Is redistributed left rear wheel longitudinal force, F'x4Is the redistributed right rear wheel longitudinal force;
if the magnitude of the longitudinal force of the redistributed wheel meets F'xi＜Fxi_max(i is 1, 2, 3, 4), the differential braking/driving coordination control unit outputs the readjusted wheel motion form and the wheel longitudinal force magnitude distributed by the formula (5) to the vehicle control unit VCU;
step 4) correction of the redistribution of wheel braking or driving forces
If wheel longitudinal force satisfying F 'exists after redistribution'xi≥Fxi_maxThen, the wheel braking or driving force redistribution is corrected so that the stress of all wheels satisfies:
Figure BDA0003022617280000071
in the formula F ″)x1For a modified left front wheel longitudinal force, F ″)x2For a modified longitudinal force of the right front wheel, F ″)x3For a modified left rear wheel longitudinal force, F ″)x4Is a modified right rear wheel longitudinal force;
if after correction all wheels reach the adhesion limit or
Figure BDA0003022617280000072
Reminding the driver to take emergency steering and braking to ensure the driving stability of the automobile;
step 5) execution of output result of differential braking/driving coordination control unit
The differential braking/driving coordination control unit inputs the finally distributed wheel longitudinal force result into a vehicle control unit VCU, and the vehicle control unit VCU controls a left front wheel motor controller, a right front wheel motor controller, a left rear wheel motor controller and a right rear wheel motor controller to enable a left front wheel hub motor, a right front wheel hub motor, a left rear wheel hub motor and a right rear wheel hub motor to output torque and control a left front wheel disc brake, a right front wheel disc brake, a left rear wheel disc brake and a right rear wheel disc brake to work to provide braking torque, and corresponding differential braking/driving operation is implemented, and the differential braking/driving coordination control unit adjusts the differential braking/driving operation through vehicle motion state data acquired by a sensor unit in real time.
The invention has the following beneficial effects: the independent driving characteristics of the wheels of the distributed drive electric automobile are fully utilized in the anti-rollover control process, under the condition of being limited by road adhesion conditions, a sufficient counter-swing moment is generated by implementing a coordinated control mode of one-side driving/one-side braking of the coaxial wheels so as to avoid the rollover risk of the automobile, the upper limit value of the maximum anti-swing moment provided by the distributed drive electric automobile under the driving conditions (particularly low-adhesion roads) with different road adhesion coefficients is effectively improved, and meanwhile, the loss of the driving speed of the automobile in the anti-rollover control process is reduced.
Drawings
FIG. 1 is a functional block diagram of a differential brake/drive coordinated anti-rollover control system.
Fig. 2 is a functional block diagram of a differential brake/drive coordination control unit.
FIG. 3 is a schematic diagram of the operation flow of the differential braking/driving coordination control rollover prevention.
Fig. 4(a) is a wheel diagram of table 1 in which the optimal anti-yaw moment is clockwise when the driver pedal signal is acceleration.
Fig. 4(b) is a wheel diagram of table 1 in which the optimal anti-yaw moment is counterclockwise when the driver pedal signal is acceleration.
Fig. 4(c) is a wheel diagram of table 1 in which the optimal anti-yaw moment is clockwise when the driver pedal signal is deceleration.
Fig. 4(d) is a wheel diagram of table 1 in which the optimal anti-yaw moment is counterclockwise when the driver pedal signal is deceleration.
Fig. 4(e) is a wheel diagram of table 2 in which the optimal anti-yaw moment is clockwise when the driver pedal signal is acceleration.
Fig. 4(f) is a wheel diagram of table 2 in which the optimal anti-yaw moment is counterclockwise when the driver pedal signal is deceleration.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, the differential braking/driving coordination rollover prevention control system designed by the present invention is composed of a sensor unit 1, a signal acquisition processing unit 2, a rollover warning unit 3, an optimal counter-swing moment calculation unit 4, an adhesion coefficient identification unit 5, a vehicle control unit VCU6, a differential braking/driving coordination control unit 7, a left front wheel motor controller 8, a left front wheel disc brake 9, a left front wheel hub motor 10, a right front wheel motor controller 11, a right front wheel disc brake 12, a right front wheel hub motor 13, a left rear wheel motor controller 14, a left rear wheel disc brake 15, a left rear wheel hub motor 16, a right rear wheel motor controller 17, a right rear wheel disc brake 18, and a right rear wheel hub motor 19, wherein the sensor unit 1 is connected with the signal acquisition processing unit 2, the rollover warning unit 3, the signal acquisition processing unit 2, the left rear wheel disc brake, the rollover warning unit 2, the adhesion coefficient identification unit, the left front wheel disc brake, the right rear wheel hub motor controller, the left rear wheel disc brake, the right rear wheel disc brake, the left rear wheel hub motor, the right rear wheel disc brake, and the right rear wheel hub motor 19, respectively, The optimal counter balance moment calculation unit 4 and the adhesion coefficient identification unit 5 are connected, the rollover warning unit 3 is connected with a vehicle control unit VCU6, the vehicle control unit VCU6, the optimal counter balance moment calculation unit 4 and the adhesion coefficient identification unit 5 are all connected with a differential braking/driving coordination control unit 7, the left front wheel hub motor 10 is connected with the left front wheel motor controller 8, the right front wheel hub motor 13 is connected with the right front wheel motor controller 11, the left rear wheel hub motor 16 is connected with the left rear wheel motor controller 14, the right rear wheel hub motor 19 is connected with the right rear wheel motor controller 17, the left front wheel motor controller 8, the left front wheel disc brake 9, the right front wheel motor controller 11, the right front wheel disc brake 12, the left rear wheel motor controller 14, the left rear wheel disc brake 15, the right rear wheel motor controller 17 and the right rear wheel disc brake 18 are all connected with a VCU6 of the whole vehicle controller.
The sensor unit 1 comprises a vehicle speed sensor for acquiring the vehicle running speed v and a vehicle wheel speed sensor for acquiring the vehicle wheel speed omegai(i ═ 1, 2, 3, 4, where 1 represents the front left wheel, 2 represents the front right wheel, 3 represents the rear left wheel, and 4 represents the rear right wheel), the longitudinal acceleration sensor is used to collect the longitudinal acceleration a of the vehiclexThe transverse acceleration sensor is used for acquiring the transverse acceleration a of the automobileyThe yaw rate sensor is used for acquiring the yaw rate omega of the automobilerThe suspension mass side inclination angle sensor is used for measuring the suspension mass side inclination angle phi, and the suspension mass side inclination angle speed sensor is used for measuring the suspension mass side inclination angle speed
Figure BDA0003022617280000101
Suspension mass roll angle acceleration sensor for measuring suspension mass roll angle acceleration
Figure BDA0003022617280000102
The drive/brake pedal signal sensor is used to collect a driver pedal signal.
The sensor unit 1 inputs the acquired data to the signal acquisitionA processing unit 2, a signal acquisition processing unit 2 and a vehicle transverse acceleration ayThe suspension mass roll angle phi is input into the rollover warning unit 3 to judge whether the automobile has rollover danger, if the rollover warning unit judges that the automobile has rollover danger, the rollover warning unit 3 outputs a danger signal to the vehicle control unit VCU6, the vehicle control unit VCU6 outputs a signal to start the differential braking/driving coordination control unit 7, and the signal acquisition and processing unit 2 acquires the longitudinal acceleration a of the automobilexYaw angular velocity ωrSuspension mass roll angular velocity
Figure BDA0003022617280000103
Suspension mass roll acceleration
Figure BDA0003022617280000104
Inputting the moment into an optimal counter-balance moment calculation unit 4 and outputting the optimal counter-balance moment Delta M to a differential braking/driving coordination control unit 7, and a signal acquisition and processing unit 2 acquires the running speed v, the wheel speed omega and the longitudinal acceleration a of the automobilexThe adhesion coefficient identification unit 5 outputs the adhesion coefficient μ of the running wheels at the respective slip rates λ, and the adhesion coefficient identification unit 5 outputs the adhesion coefficient μ of the running wheels at the respective slip rates λi(lambda) to the differential braking/driving coordination control unit 7, the differential braking/driving coordination control unit 7 outputs the magnitude of the longitudinal force and the wheel to which the longitudinal force (braking force or driving force) is applied, and sends a signal to the vehicle control unit VCU6 to make the vehicle control unit VCU6 send instructions to control the left front wheel hub motor 10, the right front wheel hub motor 13, the left rear wheel hub motor 16, the right rear wheel hub motor 19 to output torque and control the left front wheel disc brake 9, the right front wheel disc brake 12, the left rear wheel disc brake 15, the right rear wheel disc brake 18 to work to provide braking torque according to the braking force or driving force distributed by the differential braking/driving coordination control unit 7, therefore, the driving force or the braking force generated by the wheels can provide a counter-balance moment to keep the running stability of the automobile.
As shown in fig. 2, the differential braking/driving coordination control unit 7 in the present invention is composed of a tire vertical load calculation unit 20, a tire maximum longitudinal force calculation unit 21, a wheel motion form determination unit 22, and an optimal counter balance moment distribution unit 23.
The signal acquisition processing unit 2 acquires the longitudinal acceleration a of the automobilexAutomobile yaw angular velocity omegarSuspension mass roll angular velocity
Figure BDA0003022617280000111
Suspension mass roll acceleration
Figure BDA0003022617280000112
The optimal counter balance moment is input to the optimal counter balance moment calculation unit 4, the optimal counter balance moment calculation unit 4 outputs the optimal counter balance moment Δ M and inputs the optimal counter balance moment Δ M to the wheel motion form determination unit 22, the signal processing unit 2 inputs the vehicle control unit VCU6 to the wheel motion form determination unit 22, and the wheel motion form determination unit 22 outputs the wheel motion form result to the optimal counter balance moment distribution unit 23. The adhesion coefficient identification unit 5 calculates the adhesion coefficient μ of each wheel at each slip ratio λi(lambda), the result is input to the tire maximum longitudinal force calculation unit 21, and the vehicle control unit VCU6 calculates the vehicle acceleration axThe vertical loads of the respective wheels F are inputted to the tire vertical load calculation unit 20, and the tire vertical load calculation unit 20 calculates the vertical loads of the respective wheels Fzi(i ═ 1, 2, 3, 4, where 1 represents the left front wheel, 2 represents the right front wheel, 3 represents the left rear wheel, and 4 represents the right rear wheel) is input to the tire maximum longitudinal force calculating unit 21, and the tire maximum longitudinal force calculating unit 21 calculates the maximum longitudinal force F that can be provided by each tirexi_max(i ═ 1, 2, 3, 4, where 1 represents the left front wheel, 2 represents the right front wheel, 3 represents the left rear wheel, and 4 represents the right rear wheel), the results are input to the optimal counter-balance moment distribution unit 23, and the optimal counter-balance moment distribution unit 23 distributes the moment according to the maximum longitudinal force Fxi_maxSending an adjusting signal to a wheel motion form determining unit 22, inputting the adjusted wheel motion form result into an optimal balance pendulum moment distributing unit 23 by the wheel motion form determining unit 22, inputting the final wheel longitudinal force distributing result into a vehicle control unit VCU6 by the optimal balance pendulum moment distributing unit 23, and inputting the vehicle control unit VCU6 controls left front wheel motor controller 8, right front wheel motor controller 11, left rear wheel motor controller 14 and right rear wheel motor controller 17 to make left front wheel hub motor 10, right front wheel hub motor 13, left rear wheel hub motor 16 and right rear wheel hub motor 19 output torque and control left front wheel disc brake 9, right front wheel disc brake 12, left rear wheel disc brake 15 and right rear wheel disc brake 18 to work to provide braking torque.
As shown in FIG. 3, the differential braking/driving coordination control strategy of the invention has the following anti-rollover operation steps:
step 1) determining whether the automobile has rollover danger or not, and whether differential braking/driving rollover prevention control is started or not.
The signal acquisition processing unit 2 acquires the transverse acceleration a of the automobile through the sensor unit 1yAnd the suspension mass roll inclination angle phi sends data to the rollover early warning unit 3, and the lateral load transfer rate LTR is calculated according to the following formula:
Figure BDA0003022617280000121
in the formula, m is the mass of the whole automobile; m issIs a suspended mass; h is the distance between the center of mass of the suspended mass and the roll axis; h isrThe distance between the roll center and the ground; g is the acceleration of gravity; and B is a wheel track.
Defining the LTR threshold LTR of an automobiletWhen LTR |, is greater than or equal to 0.8, it is determined that the vehicle is in a rollover risk, and the vehicle control unit VCU6 sends an instruction to enable the differential braking/driving coordination control unit 7 to work to start the differential braking/driving anti-rollover control; when | LTR | < 0.8, the vehicle control unit VCU controls the sensor unit 1 to repeatedly collect data and calculate the transverse load transfer rate LTR.
Step 2) determining for the first time the wheel movement pattern and the distribution of wheel braking or driving forces.
The optimal counter-balance moment unit 4 outputs the optimal counter-balance moment Δ M and inputs it to the wheel motion pattern determination unit 22, the vehicle control unit VCU6 outputs a driver pedal signal to the wheel motion pattern determination unit 22, and the wheel motion pattern determination unit 22 determines the wheel motion pattern according to table 1. When Δ M has a tendency to steer the vehicle to the left, Δ M is defined as counterclockwise, and when Δ M has a tendency to steer the vehicle to the right, Δ M is defined as clockwise, and none of table 1 indicates that no longitudinal force is applied.
TABLE 1 wheel movement form table
Figure BDA0003022617280000131
The optimal counter-balance pendulum moment distribution unit 23 distributes the longitudinal force of the automobile tire according to the wheel motion form determined by the wheel motion form determination unit 22, defines the forward direction of the wheel as positive, and distributes the magnitude of the longitudinal force according to the following formula:
Figure BDA0003022617280000132
in the formula, Fx1Is the left front wheel longitudinal force; fx2Is the right front wheel longitudinal force; fx3Is the left rear wheel longitudinal force; fx4Is the right rear wheel longitudinal force.
Step 3) adjustment of wheel movement pattern and redistribution of wheel braking or driving force
The signal acquisition processing unit 2 acquires the longitudinal acceleration a of the automobilexThe longitudinal acceleration a is input into a VCU6 of the vehicle control unit, and the VCU6 of the vehicle control unitxInput into the tire vertical load calculation unit 20, and calculate the current vertical load F of each wheelziThe calculation formula is as follows:
Figure BDA0003022617280000141
in the formula, Fz1The left front wheel vertical load; fz2Is the right front wheel vertical load; fz3Vertical load for the left rear wheel; fz4Is a vertical load of the right rear wheel; a is the distance from the center of the front wheel to the center of mass of the automobile; b is the distance from the center of the rear wheel to the center of mass of the automobile; h is a total ofgThe height of the mass center of the whole vehicle.
Further, the signal acquisition processing unit 2 acquires the speed v of the vehicle and the speed ω of each wheeliLongitudinal acceleration a of the vehiclexThe adhesion coefficient is inputted to the adhesion coefficient identification unit 5, and the adhesion coefficient identification unit 5 identifies the adhesion coefficient mu at the current slip ratio of each wheeli(lambda) is inputted to the tire maximum longitudinal force calculation unit 21, and the tire maximum longitudinal force calculation unit 21 calculates the maximum longitudinal force F that the wheel to which the longitudinal force has been distributed can provide under the constraint conditions of the vertical load and the adhesion coefficientxi_maxThe calculation formula is as follows:
Fxi_max＝μi(λ)Fzi (4)
in the formula, mui(λ) is the wheel adhesion coefficient, i ═ 1, 2, 3, 4; fziFor wheel vertical load, i is 1, 2, 3, 4.
Comparing the force of wheel under braking or driving action distributed according to the pedal signal of driver and optimal counter-pendulum moment with the maximum longitudinal force (braking or driving force) provided by the wheel under the constraint of vertical load and adhesion coefficient, if all the wheel with applied longitudinal force satisfies the condition Fxi≤Fxi_max(i ═ 1, 3, or 2, 4, where 1 represents the left front wheel, 2 represents the right front wheel, 3 represents the left rear wheel, and 4 represents the right rear wheel), the differential braking/driving coordination control unit 7 outputs the magnitude of the primarily distributed wheel longitudinal force to the vehicle control unit VCU 6; if the wheel stress magnitude of the primary distribution longitudinal force exists Fxi＞Fxi_maxThen the adjustment of the wheel motion profile is performed according to table 2:
TABLE 2 form table for wheel motion compensation
Figure BDA0003022617280000151
The redistribution of braking or driving force is performed according to the following formula:
Figure BDA0003022617280000152
of formula (II) F'x1Is the redistributed left front wheel longitudinal force, F'x2Is the redistributed front right wheel longitudinal force, F'x3Is redistributed left rear wheel longitudinal force, F'x4Is the redistributed right rear wheel longitudinal force.
If the magnitude of the longitudinal force of the redistributed wheel meets F'xi＜Fxi_max(i is 1, 2, 3, 4), the differential braking/driving coordination control unit 7 outputs the wheel motion form and the magnitude of the wheel longitudinal force distributed according to the formula (5) distributed in table 2 to the vehicle control unit VCU 6.
Step 4) correction of the redistribution of the wheel braking or driving forces
If wheel longitudinal force satisfying F 'exists after redistribution'xi≥Fxi_maxThen, the wheel braking or driving force redistribution is corrected so that the stress of all wheels satisfies:
Figure BDA0003022617280000161
in the formula F ″)x1For a modified left front wheel longitudinal force, F ″)x2For a modified longitudinal force of the right front wheel, F ″)x3For a modified left rear wheel longitudinal force, F ″)x4Is a corrected right rear wheel longitudinal force.
If after correction all wheels reach the adhesion limit or
Figure BDA0003022617280000162
The driver is reminded to take emergency steering and braking to ensure the driving stability of the automobile.
Step 5) execution of output result of differential braking/driving coordination control unit 7
The differential braking/driving coordination control unit 7 inputs the finally distributed wheel longitudinal force result to the vehicle control unit VCU6, and the vehicle control unit VCU6 controls the left front wheel motor controller 8, the right front wheel motor controller 11, the left rear wheel motor controller 14 and the right rear wheel motor controller 17 to make the left front wheel hub motor 10, the right front wheel hub motor 13, the left rear wheel hub motor 16 and the right rear wheel hub motor 19 output torque and control the left front wheel disc brake 9, the right front wheel disc brake 12, the left rear wheel disc brake 15 and the right rear wheel disc brake 18 to work to provide braking torque. And corresponding differential braking/driving operation is carried out, and the differential braking/driving coordination control unit 7 adjusts the differential braking/driving operation through the automobile motion state data acquired by the sensor unit 1 in real time.
As shown in fig. 4(a) to 4(f), the stress diagrams of the wheels of the distributed drive electric vehicle for preventing rollover under different driving conditions are shown. The automobile differential braking/driving control wheel force diagram is under the constraint conditions of a driver pedal signal, an optimal counter pendulum moment, an adhesion coefficient and a vertical load.

Claims (2)

1. The utility model provides a differential braking/drive coordination prevents control system that turns on one's side which characterized in that: the device comprises a sensor unit, a signal acquisition and processing unit, a rollover early warning unit, an optimal counter balance moment calculation unit, an adhesion coefficient identification unit, a whole vehicle controller VCU, a differential braking/driving coordination control unit, a left front wheel motor controller, a left front wheel disc brake, a left front wheel hub motor, a right front wheel motor controller, a right front wheel disc brake, a right front wheel hub motor, a left rear wheel motor controller, a left rear wheel disc brake, a left rear wheel hub motor, a right rear wheel motor controller, a right rear wheel disc brake and a right rear wheel hub motor, wherein the sensor unit is connected with the signal acquisition and processing unit, the signal acquisition and processing unit is respectively connected with the rollover early warning unit, the optimal counter balance moment calculation unit and the adhesion coefficient identification unit, the rollover early warning unit is connected with the whole vehicle controller VCU, the whole vehicle controller VCU, The optimal counter balance pendulum moment calculation unit and the attachment coefficient identification unit are both connected with the differential braking/driving coordination control unit;
the sensor unit comprises a vehicle speed sensor for acquiring the running speed v of the vehicle and a sensor unit for acquiring the speed omega of the vehicleiAutomobile wheel speed sensor for acquiring automobile longitudinal acceleration axLongitudinal acceleration sensor for acquiring transverse acceleration a of automobileyIn the transverse direction ofSpeed sensor for acquiring yaw velocity omega of automobilerYaw angular velocity sensor, suspended mass roll angle sensor for measuring the roll angle phi of the suspended mass, and method for measuring the roll angle velocity of the suspended mass
Figure FDA0003509426480000011
Suspension mass roll angular velocity sensor for measuring suspension mass roll angular acceleration
Figure FDA0003509426480000012
A suspension mass roll angle acceleration sensor and a drive/brake pedal signal sensor for acquiring a driver pedal signal;
the differential braking/driving coordination control unit comprises a tire vertical load calculation unit, a tire maximum longitudinal force calculation unit, a wheel motion form determination unit and an optimal counter balance moment distribution unit;
the sensor unit inputs the acquired data into the signal acquisition and processing unit, and the signal acquisition and processing unit inputs the transverse acceleration a of the automobileyThe suspension mass roll angle phi is input into the rollover early warning unit to judge whether the automobile has rollover danger, if the rollover early warning unit judges that the automobile has rollover danger, the rollover early warning unit outputs a danger signal to the vehicle control unit VCU, the vehicle control unit VCU outputs a signal to start the differential braking/driving coordination control unit, and the signal acquisition processing unit acquires and processes the longitudinal acceleration a of the automobilexAutomobile yaw angular velocity omegarSuspension mass roll angular velocity
Figure FDA0003509426480000021
Suspension mass roll acceleration
Figure FDA0003509426480000022
The moment of the optimal counter-balance pendulum is input into an optimal counter-balance pendulum moment calculation unit, the optimal counter-balance pendulum moment calculation unit outputs an optimal counter-balance moment delta M and inputs the optimal counter-balance pendulum moment delta M into a wheel motion form determination unit, and meanwhile, a signal processing unit inputs a driver pedal signal into a wheel motion form determination unit from a vehicle control unit VCUA wheel motion form determining unit for outputting the wheel motion form result to the optimal counter balance moment distributing unit, and an adhesion coefficient identifying unit for calculating the adhesion coefficient [ mu ] of each wheel at each slip ratio [ lambda ]i(lambda), inputting the result into a tire maximum longitudinal force calculation unit, and enabling a vehicle control unit VCU to calculate the vehicle acceleration axInputting the vertical loads into a tire vertical load calculation unit which calculates the vertical loads F of the wheelsziInput to the tire maximum longitudinal force calculation unit, i ═ 1, 2, 3, 4, where 1 represents the left front wheel, 2 represents the right front wheel, 3 represents the left rear wheel, and 4 represents the right rear wheel; the maximum longitudinal force calculation unit of the tire calculates the maximum longitudinal force F which can be provided by each tirexi_max1, 2, 3, 4, wherein 1 represents the left front wheel, 2 represents the right front wheel, 3 represents the left rear wheel, and 4 represents the right rear wheel; inputting the result into an optimal counter-balance moment distribution unit which distributes the moment according to the maximum longitudinal force Fxi_maxThe method comprises the steps of sending an adjusting signal to a wheel motion form determining unit, inputting an adjusted wheel motion form result into an optimal counter-balance swing moment distribution unit by the wheel motion form determining unit, inputting a final wheel longitudinal force distribution result into a vehicle control unit VCU, and controlling a left front wheel motor controller, a right front wheel motor controller, a left rear wheel motor controller and a right rear wheel motor controller by the vehicle control unit VCU to enable a left front wheel hub motor, a right front wheel hub motor, a left rear wheel hub motor and a right rear wheel hub motor to output torque and control a left front wheel disc brake, a right front wheel disc brake, a left rear wheel disc brake and a right rear wheel disc brake to work to provide braking torque.
2. A control method of the differential brake/drive coordinated rollover control system as recited in claim 1, wherein:
the control method comprises the following steps:
step 1) determining whether the automobile has rollover danger or not, and whether differential braking/driving rollover prevention control is started or not
The signal acquisition and processing unit acquires the transverse acceleration of the automobile through the sensor unitSpeed ayAnd the suspension mass roll inclination angle phi sends data to the rollover early warning unit, and the lateral load transfer rate LTR is calculated according to the following formula:
Figure FDA0003509426480000031
in the formula, m is the mass of the whole automobile; m is a unit ofsIs a suspended mass; h is the distance between the center of mass of the suspended mass and the roll axis; h isrThe distance between the roll center and the ground; g is the acceleration of gravity; b is a wheel track;
defining the LTR threshold LTR of an automobiletWhen the LTR is more than or equal to 0.8, the vehicle is judged to have a rollover risk, and the vehicle control unit VCU sends out a command to enable the differential braking/driving coordination control unit to work to start the differential braking/driving rollover prevention control; when | LTR | < 0.8, the vehicle control unit VCU controls the sensor unit to repeatedly collect data and calculate the transverse load transfer rate LTR;
step 2) initial determination of the wheel movement pattern and the distribution of the wheel braking or driving force
The optimal counter balance pendulum moment unit outputs an optimal counter balance pendulum moment delta M and inputs the optimal counter balance pendulum moment delta M to the wheel motion form determining unit, and the vehicle control unit VCU outputs a driver pedal signal to the wheel motion form determining unit; the optimal counter balance pendulum moment distribution unit distributes the longitudinal force of the automobile tire according to the wheel motion form determined by the wheel motion form determination unit, defines the advancing direction of the wheel as positive, and distributes the magnitude of the longitudinal force according to the following formula:
Figure FDA0003509426480000041
in the formula, Fx1Is the left front wheel longitudinal force; fx2Is the right front wheel longitudinal force; fx3Is the left rear wheel longitudinal force; fx4Is the right rear wheel longitudinal force;
step 3) adjustment of the wheel movement pattern and redistribution of the wheel braking or driving force
Signal acquisition processingUnit converts the longitudinal acceleration a of the vehiclexInputting the acceleration to a VCU of the vehicle controller, and enabling the VCU of the vehicle controller to convert the longitudinal acceleration axInputting the vertical load into a tire vertical load calculation unit, and calculating the current vertical load F of each wheelziThe calculation formula is as follows:
Figure FDA0003509426480000042
in the formula, Fz1Vertical load of the left front wheel; fz2Is the right front wheel vertical load; fz3Vertical load for the left rear wheel; fz4Is the vertical load of the right rear wheel; a is the distance from the center of the front wheel to the center of mass of the automobile; b is the distance from the center of the rear wheel to the center of mass of the automobile; h isgThe height of the mass center of the whole vehicle;
the signal acquisition and processing unit acquires the speed v of the automobile and the speed omega of each wheeliLongitudinal acceleration a of the vehiclexThe adhesion coefficient is input to an adhesion coefficient identification unit which identifies the adhesion coefficient mu at the current slip rate of each wheeli(lambda) is input into a tire maximum longitudinal force calculation unit which calculates the maximum longitudinal force F which can be provided by the wheel to which the longitudinal force has been distributed under the constraint conditions of vertical load and adhesion coefficientxi_maxThe calculation formula is as follows:
Fxi_max＝μi(λ)Fzi (4)
in the formula, mui(λ) is the wheel adhesion coefficient, i ═ 1, 2, 3, 4; fziFor wheel vertical loads, i is 1, 2, 3, 4;
comparing the force of wheel under braking or driving action distributed according to the pedal signal of driver and optimal counter-pendulum moment with the maximum longitudinal force provided by the wheel under the constraint of vertical load and adhesion coefficient, if all the wheels with applied longitudinal force meet the condition Fxi≤Fxi_maxAnd i is 1, 3 or 2, 4, where 1 represents the left front wheel, 2 represents the right front wheel, 3 represents the left rear wheel, and 4 represents the right rear wheel, the differential braking/driving coordination control unit outputs the initial timeThe distributed longitudinal force of the wheels reaches the VCU of the whole vehicle controller; if the wheel stress magnitude of the primary distribution longitudinal force exists Fxi＞Fxi_maxAdjusting the motion form of the wheels;
the redistribution of braking or driving force is performed according to the following formula:
Figure FDA0003509426480000051
of formula (II) F'x1Is the redistributed left front wheel longitudinal force, F'x2Is the redistributed front right wheel longitudinal force, F'x3Is redistributed left rear wheel longitudinal force, F'x4Is the redistributed right rear wheel longitudinal force;
if the magnitude of the longitudinal force of the redistributed wheel meets F'xi＜Fxi_maxWherein i is 1, 2, 3, 4, the differential braking/driving coordination control unit outputs the readjusted wheel motion form and the wheel longitudinal force distributed by the formula (5) to the vehicle control unit VCU;
step 4) correction of the redistribution of the wheel braking or driving forces
If wheel longitudinal force satisfying F 'exists after redistribution'xi≥Fxi_maxThen, the wheel braking or driving force redistribution is corrected so that the stress of all wheels satisfies:
Figure FDA0003509426480000061
in the formula F ″)x1For a modified left front wheel longitudinal force, F ″)x2For a modified longitudinal force of the right front wheel, F ″)x3For a modified left rear wheel longitudinal force, F ″)x4Is a modified right rear wheel longitudinal force;
if after correction all wheels reach the adhesion limit or
Figure FDA0003509426480000062
Reminding the driver to take emergency steering and braking to ensure the driving stability of the automobile;
step 5) execution of output result of differential braking/driving coordination control unit
The differential braking/driving coordination control unit inputs the finally distributed wheel longitudinal force result to a vehicle control unit VCU, and the vehicle control unit VCU controls a left front wheel motor controller, a right front wheel motor controller, a left rear wheel motor controller and a right rear wheel motor controller to enable a left front wheel hub motor, a right front wheel hub motor, a left rear wheel hub motor and a right rear wheel hub motor to output torque and control a left front wheel disc brake, a right front wheel disc brake, a left rear wheel disc brake and a right rear wheel disc brake to work to provide braking torque, corresponding differential braking/driving operation is implemented, and the differential braking/driving coordination control unit adjusts the differential braking/driving operation through vehicle motion state data acquired by a sensor unit in real time.
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