Anti-rollover control method and system for electric automobile

Abstract

The invention provides an anti-rollover control method and system for an electric automobile, and relates to the field of automobile body posture control. The control method comprises the following steps: collecting vehicle driving data; calculating a transverse load transfer rate based on the vehicle driving data, and calculating a comprehensive risk index in combination with the transverse load transfer rate and a sprung mass roll angle; the method comprises the following steps: presetting a comprehensive risk index early warning threshold value and a comprehensive risk index danger threshold value, judging the rollover working condition and the comprehensive risk index of the automobile, and executing a corresponding rollover prevention control strategy: when the rigidity of the suspension is changed, the comprehensive risk index still increases and exceeds the comprehensive risk index danger threshold value; the anti-rollover moment is changed by changing the control force of the suspensions on the two sides. After the suspension control force suppresses roll for a certain period of time, the comprehensive risk index is still not reduced to be below the early warning threshold value, the active steering system intervenes in combined control, the active steering system has two steering modes including front wheel steering and four-wheel steering, and different steering modes are used under different working conditions.

Description

Technical Field

[0001] The present invention relates to the field of vehicle body attitude control, and particularly to an anti-roll control method and system for an electric vehicle. Background Art

[0002] Vehicle rollover is a relatively dangerous type of traffic accident, which will pose a great threat to people's lives and safety. The main reasons for vehicle rollover are excessive speed during turning, sudden steering wheel turning, and too small a turning radius.

[0003] Currently, the industry mainly focuses on active anti-roll bars, differential braking technology, etc. for vehicle anti-rollover. These control methods are relatively single and cannot fully ensure that the vehicle is within the roll safety range. Therefore, how to solve the problem that a single anti-rollover technology cannot fully meet the anti-rollover requirements has become a problem to be solved. Summary of the Invention

[0004] Object of the Invention: Aiming at the multi-unit joint coordination, an anti-roll control method for an electric vehicle is proposed, and a vehicle body electronic stability system developed based on the above control method is proposed to solve the above problems existing in the prior art.

[0005] In the first aspect of the present invention, an anti-roll control method for an electric vehicle is proposed, and the steps are as follows:

[0006] Collect vehicle driving data;

[0007] Based on the vehicle driving data, calculate the lateral load transfer ratio LTR;

[0008] Combine the lateral load transfer ratio LTR and the sprung mass roll angle Calculate the comprehensive risk index R;

[0009] Set the warning threshold R t and the danger threshold R th of the comprehensive risk index, where R t <R th ;

[0010] When the comprehensive risk index R t <R≤R th and lasts for a predetermined time, execute the first control action: increase the stiffness of the inner and outer suspensions of the vehicle during turning to suppress vehicle roll;

[0011] When the comprehensive risk index R>R th and lasts for a predetermined time, execute the second control action: on the basis of maintaining the first control action, control the movement trend of the inner and outer suspensions of the vehicle during turning to offset part of the vehicle roll;

[0012] If after the scheduled duration of the second control action, the comprehensive risk index R still exceeds the comprehensive risk index warning threshold R t and continues to exceed it for a scheduled duration, perform a third control action: on the basis of maintaining the first and second control actions, actively intervene by turning the vehicle to reduce the yaw angle of the vehicle, thereby reducing the yaw rate and lateral acceleration, and thus reducing the lateral load transfer ratio and the sprung mass roll angle.

[0013] In a further embodiment of the first aspect, the vehicle driving data includes the lateral velocity v y , the longitudinal velocity v x , the yaw moment of inertia I of the whole vehicle about the z-axis z , the roll moment of inertia I of the sprung mass about the x-axis x , the yaw angular acceleration the sprung mass roll angle the front wheel steering angle δ f , the rear wheel steering angle δ r ;

[0014] Based on the vehicle driving data, establish a lateral motion equation:

[0015]

[0016] The yaw motion equation:

[0017]

[0018] The roll motion equation:

[0019]

[0020] In the formula, m and m s are the mass of the whole vehicle and the sprung mass respectively; h s is the distance from the vehicle's center of mass to the roll center; is the equivalent roll angle stiffness of the suspension; is the equivalent roll angle damping coefficient; a and b are the distances from the center of mass to the front and rear axles respectively; F yfl , F yfr , F yrl , F yrr are the lateral forces of the four wheels, M s is the anti-roll moment generated by the suspension, and M δ is the influence moment of the vehicle steering angle on the roll motion.

[0021] In a further embodiment of the first aspect, based on the vehicle driving data, calculate the lateral load transfer ratio LTR, and the formula is as follows:

[0022]

[0023] Where, F ZL represents the sum of the vertical loads of the left wheels, and F ZR represents the sum of the vertical loads of the right wheels.

[0024] In a further embodiment of the first aspect, by combining the lateral load transfer ratio LTR and the sprung mass roll angle the comprehensive risk index R is calculated as follows:

[0025]

[0026] Where, LTR th =1 is the lateral load transfer ratio when the vehicle is at the critical rollover state, is the sprung mass roll angle when the vehicle is at the critical rollover state, and α1 and α2 are the weight coefficients of the lateral load transfer ratio and the sprung mass roll angle respectively, and α1 + α2 = 1.

[0027] In a further embodiment of the first aspect, when the comprehensive risk index R t < R ≤ R th and lasts for a predetermined time duration, the first control action is executed: the rollover prevention system intervenes, and the active suspension increases the stiffness of the inner and outer suspensions;

[0028] When the comprehensive risk index R > R th and lasts for a predetermined time duration, the second control action is executed: the active suspension system controls the control forces of the inner and outer suspensions when the vehicle turns, the inner active suspension generates a downward pulling force, the inner suspension compresses, the outer active suspension generates an upward supporting force, and the outer suspension stretches;

[0029] After using the suspension control force to suppress the roll, if there is still R > R t and it lasts for a predetermined time duration, the third control action is executed: the active steering system intervenes to reduce the body roll angle and lower the lateral load transfer ratio LTR.

[0030] In a further embodiment of the first aspect, when the comprehensive risk index R t < R ≤ R th and lasts for a predetermined time duration, the first control action is executed, and the vehicle dynamics state equation for this process is as follows:

[0031]

[0032] Where, is a non - linear function related to the roll angle and its derivative; is the control gain function; is the active suspension stiffness.

[0033] In a further embodiment of the first aspect, when the comprehensive risk index R > R thAnd continue for a predetermined time, execute the second control behavior, the vehicle dynamics state equation of this process is as follows:

[0034]

[0035] In the formula, m s is the sprung mass; h s v is the distance from the center of mass of the vehicle to the roll center; y 、v x are lateral speed and longitudinal speed respectively; I x is the roll moment of inertia of the sprung mass around the x-axis; M s M is the anti-roll moment generated by the suspension; δ It is the influence moment of the vehicle's turning angle on the rolling motion; is the equivalent roll stiffness of the suspension; is the equivalent roll angle damping coefficient.

[0036] In a further embodiment of the first aspect, after the suspension control force is used to suppress the roll, R>R t And continue for a predetermined period of time, perform the third control behavior, including:

[0037] In emergency cornering and oversteering conditions, the front wheel steering is used. The vehicle dynamics state equation for this process is as follows:

[0038]

[0039] In the formula, It is a nonlinear function related to the roll angle and its derivative; is the control gain function; δ f Control input for the front wheel steering angle;

[0040] Under high-speed rapid lane change and low-speed large-angle steering conditions, four-wheel steering is used to control the rear wheels to move in the opposite direction of the front wheels during low-speed large-angle steering and in the same direction as the front wheels during high-speed rapid lane change, thereby reducing the front wheel turning angle. The vehicle dynamics state equation for this process is as follows:

[0041]

[0042] in, is a nonlinear function related to the roll angle and its derivative, is the control gain function, δ=[δ f ,δ r ] T is the steering angle control input of the front and rear wheels, where δ f is the front wheel steering angle, δ r is the rear wheel steering angle.

[0043] In a second aspect of the present invention, an anti-roll control system for an electric vehicle is disclosed. The system includes: a vehicle data acquisition module, a vehicle rollover prediction unit, a vehicle safety system judgment unit, a vehicle control system, and a vehicle control execution module.

[0044] Wherein:

[0045] The vehicle data acquisition module is used to acquire vehicle driving data.

[0046] The vehicle rollover prediction unit is used to predict and judge whether the vehicle will roll over. Based on the vehicle driving data, the lateral load transfer ratio LTR is calculated, and the comprehensive risk index R is calculated by combining the lateral load transfer ratio LTR and the sprung mass roll angle. The comprehensive risk index R is calculated.

[0047] The vehicle safety system judgment unit is used to judge the vehicle rollover condition and the comprehensive risk index R. A preset comprehensive risk index warning threshold R t and a comprehensive risk index danger threshold R th are set, where R t <R th .

[0048] The vehicle control execution module includes an active suspension and an active steering system, is connected to the vehicle control system, and executes anti-roll control.

[0049] In a further embodiment of the second aspect, the vehicle control execution module is connected to the vehicle control system and executes the following anti-roll control process:

[0050] When the comprehensive risk index R t <R≤R th and lasts for a predetermined time, the first control action is executed: increasing the stiffness of the inner and outer suspensions of the vehicle during turning to suppress vehicle roll;

[0051] When the comprehensive risk index R>R th and lasts for a predetermined time, the second control action is executed: on the basis of maintaining the first control action, controlling the movement trend of the inner and outer suspensions of the vehicle during turning to offset part of the vehicle roll;

[0052] If after executing the second control action for a predetermined time, the comprehensive risk index R still exceeds the comprehensive risk index warning threshold R t and lasts for a predetermined time, the third control action is executed: on the basis of maintaining the first control action and the second control action, the active steering intervenes to reduce the yaw rate and lateral acceleration by reducing the vehicle yaw angle, thereby reducing the lateral load transfer ratio and the sprung mass roll angle.

[0053] Compared with the prior art, the present invention has at least the following beneficial effects:

[0054] (1) The present invention calculates a comprehensive risk index based on the lateral load transfer ratio and the sprung mass roll angle, taking into account both the sprung mass roll angle and the lateral load transfer ratio, and more comprehensively and accurately evaluates the rollover risk of the vehicle.

[0055] (2) The control strategy of the present invention is to first control by changing the suspension stiffness. When the comprehensive risk index still increases beyond the dangerous threshold of the comprehensive risk index after the suspension stiffness is changed, the anti-roll moment is changed by changing the suspension control forces on both sides. When the suspension control forces suppress roll for a certain period of time and the comprehensive risk index still does not drop below the warning threshold, the active steering system intervenes for joint control. The active steering system has two steering modes, including front-wheel steering and four-wheel steering, and different steering modes are used under different working conditions.

[0056] (3) The present invention uses the method of terminal sliding mode control to adjust the stiffness and control force of the active suspension, controls the active steering system to reduce the steering angle, introduces an integral term and replaces the sign function with a saturation function to reduce the terminal sliding mode chattering problem. Description of the Drawings

[0057] Figure 1 is a schematic diagram of an electric vehicle anti-roll control system in an embodiment of the present invention.

[0058] Figure 2 is a schematic flow diagram of an electric vehicle anti-roll control method in an embodiment of the present invention. Detailed Embodiments

[0059] In the following description, numerous specific details are given to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other instances, some well-known technical features are not described to avoid confusion with the present invention.

[0060] See Figure 1 , this embodiment discloses an electric vehicle anti-roll control system, which is composed of a vehicle data acquisition module, a vehicle anti-roll prediction unit, a vehicle safety system judgment unit, a vehicle control system, and a vehicle control execution module.

[0061] The vehicle data acquisition module is used to obtain the body roll angle, vehicle yaw rate, lateral speed, and longitudinal speed; the vehicle anti-roll prediction unit predicts and judges whether the vehicle will roll over. The lateral load transfer ratio LTR is calculated in the vehicle anti-roll prediction unit, and the comprehensive LTR and the sprung mass roll angle Calculate the comprehensive risk index R; the vehicle safety system judgment unit judges the vehicle rollover condition and the comprehensive risk index R; the vehicle control system controls the rollover prevention system to work; the vehicle control execution module includes an active suspension and an active steering system, is connected to the vehicle control system, and executes rollover prevention control.

[0062] Based on the electric vehicle rollover prevention control system, this embodiment discloses an electric vehicle rollover prevention control method, and the specific steps are as follows:

[0063] Step 1: The vehicle data acquisition module is responsible for collecting relevant data, including information such as the body roll angle, lateral speed, and longitudinal speed, and sending the collected data to the vehicle rollover prediction unit for prediction and judgment.

[0064] Step 2: Calculate the lateral load transfer ratio LTR, and use the lateral load transfer ratio LTR and the sprung mass roll angle as the rollover prevention indicators of the vehicle. In the vehicle rollover prediction unit, comprehensively consider LTR and to calculate the comprehensive risk index R.

[0065] Step 3: Set the warning threshold R t of the comprehensive risk index and the dangerous threshold R th of the comprehensive risk index. When the comprehensive risk index R > R t , the vehicle rollover prevention control system works, and the suspension system intervenes to suppress vehicle roll by controlling the stiffness of the inner and outer suspensions when the vehicle turns. When the comprehensive risk index R > R th , the active suspension system controls the control forces of the inner and outer suspensions when the vehicle turns to reduce vehicle roll. The terminal sliding mode control algorithm is adopted, with the deviation between the sprung mass roll angle and the ideal sprung mass roll angle as the input to control the stiffness of the inner and outer suspensions, adjust the control forces of the inner and outer suspensions, the inner active suspension generates a downward pulling force to compress the inner suspension; the outer active suspension generates an upward supporting force to stretch the outer suspension, forming an anti-roll moment, thereby reducing the vehicle roll risk.

[0066] Step 4: The vehicle safety system judgment unit judges the comprehensive risk index R and the vehicle rollover condition. When the roll is suppressed by the suspension control force for a certain period of time and R is still greater than R tAnd if it lasts for a certain period of time, the suspension force control cannot fully meet the suppression of roll. At this time, the active steering system intervenes for combined operation. In addition, the vehicle safety system judgment unit judges the working conditions during vehicle rollover and selects different steering methods according to different working conditions. In the case of emergency turning and oversteering working conditions, front-wheel steering is used; in the case of high-speed rapid lane change and low-speed large-angle steering working conditions, four-wheel steering is used. The active steering system reduces the yaw angle, changes the vehicle's yaw moment, reduces the body roll angle, and reduces the probability of vehicle rollover. The terminal sliding mode control algorithm is adopted, with the deviation between the sprung mass roll angle and the ideal sprung mass roll angle as the input to obtain the steering angle correction amount, thereby reducing the sprung mass roll angle and reducing the rollover risk.

[0067] The specific content of the electric vehicle anti-roll control method proposed in this embodiment is as follows:

[0068] S1. Establish a vehicle dynamics model:

[0069] Lateral motion equation:

[0070]

[0071] Yaw motion equation:

[0072]

[0073] Roll motion equation:

[0074]

[0075] where m and m s are the vehicle mass and sprung mass respectively; v y , v x are the lateral speed and longitudinal speed respectively; I z , I x are the yaw moment of inertia of the vehicle about the z-axis and the roll moment of inertia of the sprung mass about the x-axis respectively; is the yaw angular acceleration; is the sprung mass roll angle; δ f , δ r are the front-wheel steering angle and rear-wheel steering angle respectively; h s is the distance from the vehicle's center of mass to the roll center; is the equivalent roll angle stiffness of the suspension; is the equivalent roll angle damping coefficient; a and b are the distances from the center of mass to the front and rear axles respectively; F yfl , F yfr , F yrl , F yrr are the lateral forces of the four wheels, M s is the anti-roll moment generated by the suspension, Mδ The influence moment generated by the vehicle cornering on the roll motion.

[0076] S2. The vehicle rollover prevention prediction unit calculates the lateral load transfer ratio LTR:

[0077]

[0078] where, F ZL represents the sum of the vertical loads of the left wheels, and F ZR represents the sum of the vertical loads of the right wheels.

[0079] Comprehensive risk index R:

[0080]

[0081] where, LTR th = 1, which is the lateral load transfer ratio when the vehicle is at the rollover critical point, is the sprung mass roll angle when the vehicle is at the rollover critical point, and α1 and α2 are the weight coefficients of the lateral load transfer ratio and the sprung mass roll angle respectively, and α1 + α2 = 1.

[0082] Set the warning threshold R t = 0.5 of the comprehensive risk index, and the danger threshold R th = 0.8 of the comprehensive risk index. When R > 0.5 and lasts for a certain period of time, the rollover prevention system intervenes, and the active suspension changes the stiffness of the inner and outer suspensions, reduces the compression amount of the outer suspension, suppresses the vehicle roll, and reduces the rollover risk. When the comprehensive risk index R > 0.8 and lasts for a certain period of time, the active suspension system controls the control forces of the inner and outer suspensions of the vehicle during turning. The inner active suspension generates a downward pulling force, the inner suspension compresses, the outer active suspension generates an upward supporting force, and the outer suspension stretches, thereby reducing the comprehensive risk index. When the roll is suppressed by the suspension control force and R is still greater than 0.5 and lasts for a certain period of time, the active steering system intervenes, reduces the vehicle roll angle, and reduces the lateral load transfer ratio.

[0083] S3. When R > 0.5 and lasts for a certain period of time, the rollover prevention system intervenes, and the active suspension changes the stiffness of the inner and outer suspensions. Define the ideal sprung mass roll angle as Establish a vehicle dynamics equation including the sprung mass roll angle. For the convenience of control design, the simplified state equation is

[0084]

[0085] where, is a non - linear function related to the roll angle and its derivative, is the control gain function, is the active suspension stiffness.

[0086] Define the sprung mass roll angle error Considering the problem of terminal sliding mode chattering, an integral term is introduced, and the terminal sliding mode surface s1 is designed as

[0087]

[0088] where α1>0, β1>0, λ1>0 are the design parameters of the sliding mode surface, which adjust the speed of the system state converging to the sliding mode surface, and p1 and q1 are positive odd numbers, and p1>q1, ensuring that the system state converges to the equilibrium point within a finite time.

[0089] According to the first derivative of the sprung mass roll angle error can be obtained Usually under the expectation of stable driving Take the derivative of the terminal sliding mode surface s1:

[0090]

[0091] Because it can be obtained that

[0092]

[0093] And according to the sliding mode reaching condition Let (η1>0 is the reaching gain, and sgn(s1) is the sign function), and we get

[0094]

[0095] To weaken the chattering, the sign function sgn(s1) is replaced by the saturation function sat(s1 / Δ1), where Δ1 is the boundary layer thickness, so as to obtain the active suspension stiffness u

[0096]

[0097] The saturation function sat(s1 / Δ1) is defined as

[0098]

[0099] By measuring the sprung mass roll angle in real time, calculating the error e and the terminal sliding mode surface s1, the active suspension stiffness is calculated, and the inner and outer suspension stiffnesses are adjusted through the active suspension control system, so as to suppress the vehicle roll. After the suspension stiffness adjustment is intervened, when the comprehensive risk index R is equal to 0 and lasts for a certain period of time, the suspension stiffness control exits and the suspension stiffness returns to normal.

[0100] When the comprehensive risk index R > 0.8 and lasts for a certain period of time, the suspension stiffness adjustment cannot meet the roll suppression, the stiffness adjustment is maintained, and the active suspension control force control intervenes. The active suspension system controls the control forces of the inner and outer suspensions of the vehicle during turning. The state equation is

[0101]

[0102] Sprung mass roll angle error Considering the problem of terminal sliding mode chattering, an integral term is introduced, and the terminal sliding mode surface s2 is designed as

[0103]

[0104] where α2 > 0, β2 > 0, λ2 > 0 are the design parameters of the sliding mode surface, p2 and q2 are positive odd numbers, and p2 > q2.

[0105] According to The first derivative of the sprung mass roll angle error can be obtained Because And usually Usually under the expectation of stable driving Derive the terminal sliding mode surface s2:

[0106]

[0107] And according to the sliding mode reaching condition Let (η2 > 0 is the reaching gain, sgn(s2) is the sign function). To weaken the chattering, the sign function sgn(s2) is replaced by the saturation function sat(s2 / Δ2), where Δ2 is the boundary layer thickness, and the anti-roll moment of the suspension is obtained

[0108]

[0109] The saturation function sat(s2 / Δ2) is defined as

[0110]

[0111] By controlling the control forces of the inner and outer suspensions, a downward pulling force is generated on the inner suspension and an upward supporting force is generated on the outer suspension, reducing the lateral load transfer ratio and the vehicle roll angle, thereby reducing the comprehensive risk index and preventing the vehicle from rolling over. After the suspension control force control intervenes, R equals 0 and lasts for a certain period of time, and the suspension control force control and the suspension stiffness control withdraw, and the suspension control force and stiffness return to normal.

[0112] S4. After using the suspension control force to suppress roll for a certain period of time, if R is still greater than 0.5 and lasts for a certain period of time, the suspension force control cannot meet the roll suppression, and at this time, active steering intervenes. When the active steering system intervenes, the suspension control force control and stiffness control still remain.

[0113] The steer-by-wire system includes front-wheel steering and four-wheel steering, and different steering systems are used under different working conditions. The active steering system control reduces the vehicle yaw angle to reduce the yaw rate and lateral acceleration, thereby reducing the lateral load transfer ratio and the sprung mass roll angle.

[0114] ① In the case of emergency turning and oversteering conditions, use front-wheel steering to reduce the front-wheel steering angle and reduce the probability of rollover.

[0115] For the convenience of control design, the simplified vehicle dynamics state equation is

[0116]

[0117] Among them, is a non-linear function related to the roll angle and its derivative, is the control gain function, δ f The front-wheel steering angle control input quantity.

[0118] The sprung mass roll angle error Considering the terminal sliding mode chattering problem, an integral term is introduced, and the terminal sliding mode surface s3 is designed as

[0119]

[0120] Among them, α3>0, β3>0, λ3>0 are the design parameters of the sliding mode surface, p3 and q3 are positive odd numbers, and p3>q3.

[0121] According to the first derivative of the sprung mass roll angle error can be obtained Differentiate the terminal sliding mode surface s3:

[0122]

[0123] Because and usually it can be obtained

[0124]

[0125] And according to the sliding mode reaching condition, let (η3>0 is the reaching gain, sgn(s3) is the sign function), to weaken the chattering, replace the sign function sgn(s3) with the saturation function sat(s3 / Δ3), where Δ3 is the boundary layer thickness, and get

[0126]

[0127] The saturation function sat(s3 / Δ3) is defined as

[0128]

[0129] Thus, the steering angle control input δ of the front wheel is obtained f

[0130]

[0131] The calculated front-wheel steering angle δ f is sent to the actuator of the front-wheel active steering system to reduce a certain angle on the basis of the original angle, change the driving attitude of the vehicle, reduce the deviation between the roll angle and the ideal roll angle, and achieve rollover prevention control.

[0132] ② In the high-speed rapid lane-changing and low-speed large-angle steering conditions, four-wheel steering is used to control the rear wheel to be opposite to the front wheel during low-speed large-angle steering and the same as the front wheel during high-speed rapid lane-changing, reduce the front-wheel rotation angle, and reduce the rollover probability.

[0133] For the convenience of control design, the simplified vehicle dynamics state equation is

[0134]

[0135] where is a non-linear function related to the roll angle and its derivative is the control gain function δ = [δ f , δ r T is the steering angle control input of the front and rear wheels, where δ f is the front-wheel steering angle and δ r is the rear-wheel steering angle.

[0136] Considering the terminal sliding mode chattering problem, an integral term is introduced, and the terminal sliding mode surface s4 is designed as

[0137]

[0138] where λ4>0 is the design parameter of the sliding mode surface, and p4 and q4 are positive odd numbers, and p4>q4.

[0139] According to Differentiate the terminal sliding mode surface s4:[[]]

[0140]

[0141] Because ​And usually It can be obtained that

[0142]

[0143] And according to the sliding mode reaching condition, let (η4>0 is the reaching gain, and sgn(s4) is the sign function). To weaken the chattering, the sign function sgn(s4) is replaced by the saturation function sat(s4 / Δ4), where Δ4 is the boundary layer thickness, and we get

[0144]

[0145] The saturation function sat(s4 / Δ4) is defined as

[0146]

[0147] Thus, the four-wheel steering angle control input δ

[0148]

[0149] The calculated front and rear wheel steering angles δ f 、δ r are sent to the actuators of the front and rear wheel active steering systems, and a certain angle is reduced on the basis of the original angle, thereby changing the driving attitude of the vehicle, reducing the deviation between the roll angle and the ideal roll angle, and achieving the purpose of anti-rollover.

[0150] After the active steering intervenes, the body roll angle and the yaw load transfer ratio decrease, thereby reducing the comprehensive risk index R and the rollover risk. When the comprehensive risk index R is less than 0.5 and lasts for a certain period of time, the active steering system exits, and the vehicle roll is suppressed by relying on the suspension control force control and stiffness control, so that the comprehensive risk index R is kept below 0.5. When the comprehensive risk index R is equal to 0, the anti-rollover control system exits.

[0151] The electric vehicle rollover prevention control method disclosed in the above embodiments can, in actual application, have its operating logic written as a program product, which is written into a storage medium and runs on an electronic device. More specific examples of the computer-readable storage medium mentioned in this embodiment may include, but are not limited to: electrical connections with one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, optical storage devices, magnetic storage devices, or any suitable combination of the above. The computer-readable storage medium may include data signals propagated in a baseband or as part of a carrier wave, which carry readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable signal medium may also be any readable medium other than the readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0152] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as a limitation of the present invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A method for preventing an electric vehicle from rolling over, characterized in that: The steps include: Collect vehicle driving data; Calculating a lateral load transfer rate LTR based on the vehicle driving data; Combining the lateral load transfer rate LTR and the sprung mass roll angle The comprehensive risk index R is calculated; Set the comprehensive risk indicator warning threshold R t and the comprehensive risk index danger threshold R th , where R t <R th ; When the comprehensive risk index R t <R≤R th And it lasts for a predetermined time, executing the first control behavior: increasing the stiffness of the inner and outer suspensions when the car turns, so as to suppress the vehicle from rolling; When the comprehensive risk index R>R th And continue for a predetermined time, and execute the second control behavior: on the basis of maintaining the first control behavior, control the movement trend of the inner and outer suspensions when the car turns to offset part of the vehicle roll; If the comprehensive risk index R still exceeds the comprehensive risk index warning threshold R after the second control behavior is executed for a predetermined period of time, t And it lasts for a predetermined time, and executes the third control behavior: on the basis of maintaining the first control behavior and the second control behavior, active steering intervention is performed to reduce the yaw angle of the vehicle to reduce the yaw angular velocity and lateral acceleration, thereby reducing the lateral load transfer rate and the sprung mass roll angle.

2. The electric vehicle rollover prevention control method according to claim 1, characterized in that: The vehicle driving data includes the lateral speed v y , longitudinal speed v x 、The yaw moment of inertia of the vehicle around the z-axis I z , the rolling moment of inertia of the sprung mass about the x-axis I x , yaw angular acceleration Sprung mass roll angle Front wheel turning angle δ f , rear wheel turning angle δ r ; The lateral motion equation is established based on the vehicle driving data: Yaw equation of motion: Rolling motion equation: In the formula, m, m s are vehicle mass and sprung mass respectively; h s is the distance from the center of mass of the vehicle to the roll center; is the equivalent roll stiffness of the suspension; is the equivalent roll angle damping coefficient; a and b are the distances from the center of mass to the front and rear axles respectively; F yfl 、F yfr 、F yrl 、F yrr is the lateral force of the four wheels, M s is the anti-roll moment generated by the suspension, M δ It is the torque that affects the rolling motion caused by the vehicle's turning angle.

3. The electric vehicle rollover prevention control method according to claim 2, characterized in that: Based on the vehicle driving data, the lateral load transfer rate LTR is calculated according to the following formula: In the formula, F ZL represents the sum of the vertical loads on the left wheels, F ZR Represents the sum of the vertical loads on the right wheels.

4. The electric vehicle rollover prevention control method according to claim 3, characterized in that: Combining the lateral load transfer rate LTR and the sprung mass roll angle The comprehensive risk index R is calculated: In the formula, LTR th =1 is the lateral load transfer rate of the vehicle at the critical time of rollover, is the sprung mass roll angle of the vehicle at the critical time of rollover, α1 and α2 are the weight coefficients of the lateral load transfer rate and the sprung mass roll angle respectively, and α1+α2=1.

5. The electric vehicle rollover prevention control method according to claim 2, characterized in that: When the comprehensive risk index R t <R≤R th And it lasts for a predetermined time, and the first control behavior is executed: the anti-rollover system intervenes, and the active suspension increases the stiffness of the inner and outer suspensions; When the comprehensive risk index R>R th And it lasts for a predetermined time, and executes the second control behavior: the active suspension system controls the control force of the inner and outer suspensions when the car turns, the inner active suspension generates a downward pulling force, the inner suspension is compressed, and the outer active suspension generates an upward supporting force, and the outer suspension is stretched; When the suspension control force is used to suppress the roll, there is still R>R t And it lasts for a predetermined time, executing the third control behavior: the active steering system intervenes to reduce the body roll angle and reduce the lateral load transfer rate LTR.

6. The electric vehicle rollover prevention control method according to claim 5, characterized in that: When the comprehensive risk index R t <R≤R th And continue for a predetermined time, execute the first control behavior, the vehicle dynamics state equation of this process is as follows: In the formula, It is a nonlinear function related to the roll angle and its derivative; is the control gain function; is the active suspension stiffness.

7. The electric vehicle rollover prevention control method according to claim 5, characterized in that: When the comprehensive risk index R>R th And continue for a predetermined time, execute the second control behavior, the vehicle dynamics state equation of this process is as follows: In the formula, m s is the sprung mass; h s v is the distance from the center of mass of the vehicle to the roll center; y 、v x are lateral speed and longitudinal speed respectively; I x is the roll moment of inertia of the sprung mass around the x-axis; M s M is the anti-roll moment generated by the suspension; δ It is the influence moment of the vehicle's turning angle on the rolling motion; is the equivalent roll stiffness of the suspension; is the equivalent roll angle damping coefficient.

8. The electric vehicle rollover prevention control method according to claim 5, characterized in that: When the suspension control force is used to suppress the roll, there is still R>R t And continue for a predetermined period of time, perform the third control behavior, including: In emergency cornering and oversteering conditions, the front wheel steering is used. The vehicle dynamics state equation for this process is as follows: In the formula, It is a nonlinear function related to the roll angle and its derivative; is the control gain function; δ f Control input for the front wheel steering angle; Under high-speed rapid lane change and low-speed large-angle steering conditions, four-wheel steering is used to control the rear wheels to move in the opposite direction of the front wheels during low-speed large-angle steering and in the same direction as the front wheels during high-speed rapid lane change, thereby reducing the front wheel turning angle. The vehicle dynamics state equation for this process is as follows: in, is a nonlinear function related to the roll angle and its derivative, is the control gain function, δ=[δ f ,δ r ] T is the steering angle control input of the front and rear wheels, where δ f is the front wheel steering angle, δ r is the rear wheel steering angle.

9. An electric vehicle rollover prevention control system, characterized in that: include: Vehicle data collection module, used to collect vehicle driving data; The vehicle rollover prevention prediction unit is used to predict whether the vehicle will roll over, calculate the lateral load transfer rate LTR based on the vehicle driving data, and combine the lateral load transfer rate LTR and the sprung mass roll angle The comprehensive risk index R is calculated; The vehicle safety system judgment unit is used to judge the vehicle rollover condition and the comprehensive risk index R, and preset the comprehensive risk index warning threshold R t and the comprehensive risk index danger threshold R th , where R t <R th ; The vehicle control execution module, including active suspension and active steering systems, is connected to the vehicle control system to perform anti-rollover control.

10. The electric vehicle rollover prevention control method according to claim 9, characterized in that: The vehicle control execution module is connected to the vehicle control system and executes the following anti-rollover control process: When the comprehensive risk index R t <R≤R th And it lasts for a predetermined time, executing the first control behavior: increasing the stiffness of the inner and outer suspensions when the car turns, so as to suppress the vehicle from rolling; When the comprehensive risk index R>R th And continue for a predetermined time, and execute the second control behavior: on the basis of maintaining the first control behavior, control the movement trend of the inner and outer suspensions when the car turns to offset part of the vehicle roll; If the comprehensive risk index R still exceeds the comprehensive risk index warning threshold R after the second control behavior is executed for a predetermined period of time, t And it lasts for a predetermined time, and executes the third control behavior: on the basis of maintaining the first control behavior and the second control behavior, active steering intervention is performed to reduce the yaw angle of the vehicle to reduce the yaw angular velocity and lateral acceleration, thereby reducing the lateral load transfer rate and the sprung mass roll angle.

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