A transfer case anti-lock braking control method

Abstract

The invention discloses a transfer case anti-lock braking control method, which belongs to the technical field of transfer case control. The transfer case anti-lock braking control method comprises the following steps: S10: calculating the preload torque T1 of the transfer case; S20: calculating the target speed v of the main drive shaft; m，target Calculation; S30: Determine the conditions for anti-lock closed-loop control; S40: Closed-loop control of the closed-loop control torque T of the torque transfer box target Calculation; S50: closed-loop control torque transfer box anti-lock braking control torque T t Calculate so that after the vehicle starts the anti-lock closed-loop control, it can follow the calculated T t The value increases or decreases the anti-lock control torque of the closed-loop control torque transfer case, thereby preventing the closed-loop control torque vehicle from locking. The advantage is that it can ensure the stability of the vehicle's sliding.

Description

Technical Field

[0001] The invention relates to the technical field of transfer case control, and in particular to a transfer case coasting anti-lock braking control method. Background Art

[0002] During vehicle driving, when the accelerator pedal is released, the main drive wheels of the vehicle will often lock on slippery roads due to the existence of the engine's anti-drag torque, causing the vehicle to understeer or oversteer, seriously affecting the vehicle's driving safety; at this time, it is necessary to implement anti-lock control on the transfer case; that is, it is necessary to increase or decrease the transfer case's sliding anti-lock control torque to re-achieve a reasonable distribution of the driving torque between the front and rear axles of the vehicle, thereby avoiding the locking state of the main drive wheels and improving the vehicle's sliding stability.

[0003] At present, the anti-lock control for the four-wheel drive transfer case is mainly based on threshold value control, that is, the anti-lock control coefficient and the specific sliding anti-lock control torque value of the transfer case are determined according to the speed difference between the front axle and the rear axle of the vehicle; when the speed difference is greater than the preset threshold value, the sliding anti-lock control torque of the transfer case is quickly increased to achieve four-wheel drive torque distribution; when the speed difference is less than the preset threshold value, the sliding anti-lock control torque of the transfer case is reduced to achieve efficient two-wheel drive driving.

[0004] However, when the vehicle is sliding on a slippery road, it is easy to have frequent and repeated transfer case closed-loop control torque fluctuations, main drive wheel locking fluctuations and longitudinal deceleration fluctuations, which are not conducive to the stability of vehicle sliding.

[0005] In summary, it is urgent to design a transfer case anti-lock braking control method to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a transfer case anti-lock braking control method, which can adjust the transfer case anti-lock braking control torque in real time while avoiding the influence of the locking fluctuation of the main driving wheel of the vehicle and the closed-loop control torque fluctuation of the transfer case, so as to ensure the stability of the whole vehicle sliding.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A transfer case anti-lock braking control method is provided, based on the vehicle being in a sliding state, and comprises the following steps:

[0009] S10: Calculation of the preload torque T1 of the transfer case: When the vehicle speed v is v1≤v≤v2, v1 is the first speed value of the vehicle, v2 is the second speed value of the vehicle, T f is the anti-drag torque of the engine of the vehicle, T1≤preload torque upper limit value;

[0010] S20: Target speed v of the main drive shaft m，target Calculation: v m，target =max(v s，target ,0),v s，target The speed of the main drive shaft in order to take into account the influence of the steering of the vehicle and the tire side slip;

[0011] S30: Determine the conditions for anti-lock braking closed-loop control: When v m <v m，target (1-λ1) and v m <v m，target (1-λ1) is maintained for a time t≥t1, then the anti-lock closed-loop control is started, t1 is related to the deceleration of the main drive shaft, v m is the average value of the two wheel speeds at both ends of the main drive shaft, λ1 is the triggering threshold offset of the anti-lock control function under locking conditions;

[0012] S40: Closed-loop control torque T of the transfer case target Calculation: T target =k p Δ v，m +k I ∫Δ v，m , k p and k I are all modified proportional integral control parameters obtained by modifying the control parameter factor b of the vehicle under the coasting condition, k p and k I It can realize adaptive adjustment according to the vehicle in straight line or turning conditions, Δ v，m is the speed control deviation of the main drive shaft Δ v，m =v m，target -v m ;

[0013] S50: the transfer case's anti-lock braking control torque T t Calculation: T t =T1+T target , so that after the vehicle starts the anti-lock closed-loop control, it can follow T t =T1+T target The calculated T t The anti-lock braking control torque of the transfer case is increased or decreased according to the value, so as to prevent the vehicle from locking.

[0014] Furthermore, in the step S10: when the vehicle speed v is v1>v or v>v2, T1=0.

[0015] Further, in step S20, when the main drive shaft is a rear shaft:

[0016]

[0017] Wherein, λ0 is the target slip rate, θ is the front wheel angle, in rad, γ is the yaw rate of the vehicle, in rad / s, v m,F It is the average speed of the two wheels at both ends of the front axle, in m / s, and L is the wheelbase, in m.

[0018] Further, in step S20, when the main drive shaft is the front shaft:

[0019] v s，target =min((v m,R cosθ+γLsinθ)(1-λ0),v m,R )

[0020] Wherein, λ0 is the target slip rate, θ is the rear wheel steering angle, in rad, γ is the yaw rate of the vehicle, in rad / s, v m,R is the average speed of the two wheels at both ends of the rear axle, in m / s, and L is the wheelbase, in m.

[0021] Further, when the main drive shaft is the front shaft, and considering the minimum target speed of the vehicle:

[0022] v s1，target =min(v s，target ,v min )

[0023] Among them, v s1，target is the target speed of the front axle considering the minimum target speed of the vehicle, v min To avoid wheel speed accuracy error and jitter when the vehicle is starting and driving at low speed, the minimum speed of the vehicle is determined.

[0024] Furthermore, the minimum speed v of the vehicle min The calculation formula is:

[0025] v min =MAP(v x0 , v y0,min )

[0026] Where: v x0 and v y0,min All are calibrated values, v x0 =[0 1 2 5 10 20 100], v y0,min =[2 1.5 1.2 10.5 0.2 0.2].

[0027] Furthermore, in step S30, when the anti-lock braking closed-loop control is activated:

[0028] When the closed-loop control torque T target = 0 and T target = 0 and the time t≥t2, t2 is the calibration value; or

[0029] When the output torque value of the engine is positive, the anti-lock closed-loop control is exited.

[0030] Furthermore, in step S30, the calculation formula of time t1 is:

[0031]

[0032] Among them: a axle is the actual deceleration of the main drive shaft, in m / s 2 , a 11 and a 12 are the calibrated values ​​of the deceleration of the main drive shaft, in m / s 2 , a 11 and a 12 To determine the value, t 11 and t 12 All are time calibration values, in s, t 11 and t 12 To determine the value.

[0033] Furthermore, in step S40: when Δ v，m >0, the main drive shaft is in an over-slip state, and the closed-loop control torque T of the transfer case should be increased. target , at this time, k p and k I is a positive value; when Δ v，m <0, the main drive shaft is in an under-slip state, and the control parameter factor b is reduced to reduce the closed-loop control torque T of the transfer case. target The descent speed can extend the anti-lock closed-loop control time.

[0034] Furthermore, between step S30 and step S40, step S35 is further included: calculating a modified proportional integral control parameter k p and k I :

[0035]

[0036]

[0037] Among them, k p0 With k I0is the proportional-integral control parameter.

[0038] Furthermore, in step S35, the control parameter factor b=max(b α , b v , b sw );

[0039] Among them, b α is the throttle control parameter factor of the vehicle, 0≤b α ≤1, b v is the vehicle speed control parameter factor, 0≤b v ≤1, b sw is the control parameter factor of the vehicle under steering conditions.

[0040] Furthermore, the throttle control parameter factor b of the vehicle α The calculation formula is:

[0041]

[0042] Among them, α is the current throttle opening of the vehicle, a thrsh is the throttle opening change threshold value of the vehicle, a thrsh is the calibration value.

[0043] Furthermore, the vehicle speed control parameter factor b v The calculation formula is:

[0044]

[0045] Where: v3 and v4 are the speed calibration values ​​of the vehicle, v3 and v4 are determined values, the unit is m / s, b v1 and b v2 are the calibrated values ​​of the vehicle speed control parameters, b v1 and b v2 To determine the value.

[0046] Furthermore, the control parameter factor b of the vehicle under the steering condition is sw The calculation formula is:

[0047] b sw =max(b δ , b ay , b y )b T

[0048] Where: b δ is the steering wheel angle control parameter factor of the vehicle, 0≤b δ ≤1,b ay is the lateral acceleration control parameter factor of the vehicle, by is the yaw rate control parameter factor of the vehicle, b T is the torque control parameter factor of the vehicle in the steering and sliding condition.

[0049] Furthermore, the steering wheel angle control parameter factor b of the vehicle δ The calculation formula is:

[0050]

[0051] Where: δ is the steering wheel angle of the vehicle, in rad, δ1 and δ2 are the calibrated values ​​of the steering wheel angle of the vehicle, δ1 and δ2 are the determined values, in rad, b δ1 and b δ2 are the steering wheel angle control parameter factor calibration values ​​of the vehicle, b δ1 and b δ2 To determine the value.

[0052] Furthermore, the lateral acceleration control parameter factor b of the vehicle ay The calculation formula is:

[0053]

[0054] Wherein: ay is the lateral acceleration of the vehicle, ay1 and ay2 are the calibrated values ​​of the lateral acceleration of the vehicle, ay1 and ay2 are the determined values, b ay1 and b ay2 are the lateral acceleration control parameter calibration values ​​of the vehicle, b ay1 and b ay2 To determine the value.

[0055] Furthermore, the yaw rate control parameter factor b of the vehicle y The calculation formula is:

[0056]

[0057] Where: y is the yaw rate of the vehicle, y1 and y2 are the calibrated values ​​of the yaw rate of the vehicle, y1 and y2 are the determined values, b y1 and b y2 are the calibrated values ​​of the yaw rate control parameter factors of the vehicle, b y1 and b y2 To determine the value.

[0058] Furthermore, the vehicle's steering and sliding torque control parameter factor b T The calculation formula is:

[0059]

[0060] Where: T is the torque of the vehicle under the steering and sliding condition, T1 and T2 are the torque calibration values ​​of the vehicle under the steering and sliding condition, T1 and T2 are the determined values, b T1 and b T2 are the torque control parameter calibration values ​​of the vehicle under the steering and sliding conditions, b T1 and b T2 To determine the value.

[0061] The beneficial effects of the present invention are:

[0062] By calculating the preload torque of the transfer case And calculate the target speed v of the main drive shaft m，target =max(v s，target , 0), when v m <v m，target (1-λ1) and v m <v m，target (1-λ1) is maintained for a time t≥t1, and the anti-lock closed-loop control is started; and after the vehicle starts the anti-lock closed-loop control, it can t =T1+k p Δ v，m +k I ∫Δ v，m The calculated value increases or decreases the transfer case's anti-lock control torque for coasting, thereby preventing the vehicle from locking, so as to achieve a reasonable redistribution of the front and rear axle drive torques of the vehicle, so as to ensure the stability of the vehicle's coasting; since the vehicle's speed is taken into account in the calculation of the transfer case's preload torque T1, the main drive wheel lock fluctuations that occur in the vehicle's coasting condition can be effectively avoided, and the main drive shaft can be prevented from locking by means of feedforward control; and since the target speed v of the main drive shaft is m，target The calculation process takes into account the influence of vehicle steering and tire side slip, and the closed-loop control torque T of the transfer case target The modified proportional integral control parameter k involved in the calculation p and k I are obtained by correcting the control parameter factor b of the vehicle under the gliding condition, k p and k I It can realize adaptive adjustment according to the vehicle's straight line or turning conditions, so as to effectively avoid the longitudinal deceleration fluctuation and torque fluctuation of the vehicle under the sliding condition, and adjust the closed-loop control torque T of the transfer case in real time. target, realizing the intelligent timely four-wheel drive anti-lock closed-loop control function, and then being able to avoid the locking of the main drive shaft when there is a locking trend through feedback control; in this way, the vehicle's coasting anti-lock control is realized through feedforward + feedback control, avoiding the frequent and repeated transfer case engagement torque fluctuations, main drive wheel locking fluctuations and longitudinal deceleration fluctuations when the vehicle slides on slippery roads, which is beneficial to the stability of the vehicle's coasting. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 The process diagram of the transfer case anti-lock braking control method provided by the present invention is as follows Figure 1 ;

[0064] Figure 2 The process diagram of the transfer case anti-lock braking control method provided by the present invention is as follows Figure 2 . DETAILED DESCRIPTION

[0065] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0066] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other alternative features that are equivalent or have similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features. Throughout the specification, the same reference numerals indicate the same elements.

[0067] In order to make the technical problem solved by the present invention, the technical solution adopted and the technical effect achieved more clearly, the technical solution of the present invention is further explained below with reference to the accompanying drawings and through specific implementation methods.

[0068] In this embodiment, a transfer case anti-lock braking control method is proposed. The transfer case anti-lock braking control method is based on the anti-lock braking control of the vehicle when the vehicle is in a sliding state, so as to realize the anti-lock braking control of the vehicle in a sliding state through a feedforward + feedback control method, so as to avoid frequent and repeated fluctuations in the transfer case engagement torque, main drive wheel locking fluctuations and longitudinal deceleration fluctuations when the vehicle slides on a slippery road, which is beneficial to the stability of the whole vehicle sliding. In this embodiment, the vehicle is a vehicle equipped with a timely four-wheel drive transfer case. Among them, when the throttle opening of the vehicle is less than a certain value (for example, less than 2%), it can be considered that the vehicle is in a sliding state.

[0069] Specifically, Figure 1 As shown, the transfer case anti-lock braking control method includes the following steps:

[0070] S10: Calculation of the preload torque T1 of the transfer case: When the vehicle speed v is v1≤v≤v2, v1 is the first speed value of the vehicle, v2 is the second speed value of the vehicle, T f is the reverse drag torque of the vehicle's engine, T1≤preload torque upper limit; wherein, the reverse drag torque of the vehicle's engine T f It can be calculated;

[0071] S20: Target speed v of the main drive shaft m，target Calculation: v m，target =max(v s，target ,0),v s，target The speed of the main drive shaft to take into account the vehicle's steering and tire side slip;

[0072] S30: Determine the conditions for anti-lock braking closed-loop control: When v m <v m，target (1-λ1) and v m <v m，target (1-λ1) is maintained for a time t≥t1, then the anti-lock closed-loop control is started. t1 is related to the deceleration of the main drive shaft, v m is the average speed of the two wheels at both ends of the main drive shaft, λ1 is the triggering threshold offset of the anti-lock control function under locking conditions;

[0073] S40: Closed-loop control torque T of the transfer case target Calculation: T target =k p Δ v，m +k I ∫Δ v，m , k p and k I are the corrected proportional integral control parameters obtained by correcting the control parameter factor b of the vehicle under the coasting condition, k p and k I It can realize adaptive adjustment according to the vehicle's straight line or turning conditions, Δ v，m The speed control deviation of the main drive shaft Δ v，m =v m，target -v m ;

[0074] S50: Transfer case anti-lock braking control torque T t Calculation: T t =T1+T target , so that after the vehicle starts the anti-lock control, it can follow T t =T1+T target The calculated T t The value increases or decreases the transfer case's anti-lock control torque to prevent the vehicle from locking.

[0075] By calculating the preload torque of the transfer case And calculate the target speed v of the main drive shaft m，target =max(v s，target , 0), when v m <v m，target (1-λ1) and v m <v m，target When (1-θ1) is maintained for time t≥t1, the anti-lock closed-loop control is started; and after the vehicle starts the anti-lock closed-loop control, it can t =T1+k p Δ v，m +k I ∫Δ v，m The calculated value increases or decreases the transfer case's anti-lock control torque for coasting, thereby preventing the vehicle from locking and achieving a reasonable redistribution of the vehicle's front and rear axle drive torque to ensure vehicle coasting stability.

[0076] By taking the vehicle speed into consideration in the calculation of the transfer case preload torque T1, the main drive wheel locking fluctuation can be effectively avoided in the sliding condition, and the main drive shaft can be prevented from locking by feedforward control; and because the target speed v of the main drive shaft m，target The calculation process takes into account the influence of vehicle steering and tire side slip, and the closed-loop control torque T of the transfer case target The modified proportional integral control parameter k involved in the calculation p and k I are obtained by correcting the control parameter factor b of the vehicle under the gliding condition, k p and k I It can realize adaptive adjustment according to the vehicle's straight line or turning conditions, so as to effectively avoid the longitudinal deceleration fluctuation and torque fluctuation of the vehicle under the sliding condition, and adjust the closed-loop control torque T of the transfer case in real time. target , realizing the intelligent timely four-wheel drive anti-lock closed-loop control function, and then being able to avoid the locking of the main drive shaft when there is a locking trend through feedback control; in this way, the vehicle's coasting anti-lock control is realized through feedforward + feedback control, avoiding frequent and repeated transfer case engagement torque fluctuations, main drive wheel locking fluctuations and longitudinal deceleration fluctuations when the vehicle slides on slippery roads, which is beneficial to maintaining the stability of the vehicle's coasting.

[0077] Specifically, the upper limit value of the preload torque of the transfer case can be 60Nm, the first speed value v1 of the vehicle can be 20km / h, and the second speed value v2 of the vehicle can be 80km / h. By making T1 ≤ the upper limit value of the preload torque, the phenomenon of the front axle and the rear axle of the vehicle being out of sync when turning can be avoided, so as to avoid the problem of steering interference, that is, the steering effect of the whole vehicle can be better.

[0078] Furthermore, in step S10, when the vehicle speed v is v1>v, since the low-adhesion stability of the vehicle is better at this time, the transfer case does not need to generate a preload torque, that is, T1=0 at this time; when v>v2, since the vehicle is traveling in a high gear at this time, the force of the engine's anti-drag torque acting on the wheels is small, and the transfer case does not need to generate a preload torque, that is, T1=0 at this time.

[0079] Specifically, in step S20, when the main drive shaft is the rear axle, the influence of the vehicle's steering and tire side slip is considered at the same time:

[0080]

[0081] Where λ0 is the target slip rate, θ is the front wheel steering angle of the vehicle, in rad, γ is the yaw rate of the vehicle, in rad / s, v m,F It is the average speed of the two wheels at both ends of the front axle, that is, the average speed of the left front wheel and the right front wheel, the unit is m / s, L is the wheelbase, the unit is m.

[0082] Furthermore, in step S20, when the main drive shaft is the front axle, the influence of the vehicle's steering and tire side slip is considered at the same time:

[0083] v s，target =min((v m,R cosθ+γLsinθ)(1-λ0),v m,R )

[0084] Among them, v m,R It is the average speed of the two wheels at both ends of the rear axle, that is, the average speed of the left rear wheel and the right rear wheel, and the unit is m / s.

[0085] Specifically, when the main drive shaft is the front axle, and considering the minimum target speed of the vehicle:

[0086] v s1，target =min(v s，target ,v min )

[0087] Among them, v s1，target is the target speed of the front axle under the minimum target speed of the vehicle, v minThe minimum speed of the vehicle is set to avoid wheel speed accuracy errors and jitters when the vehicle is starting and driving at low speeds.

[0088] Furthermore, in order to avoid wheel speed accuracy error and jitter in low-speed driving conditions such as starting, the minimum speed v of the vehicle at different speeds is min The calculation formula is:

[0089] v min =MAP(v x0 , v y0,min )

[0090] Where: v x0 and v y0,min All are calibrated values, v x0 =[0 1 2 5 10 20 100], v y0,min =[2 1.5 1.2 10.5 0.2 0.2].

[0091] Specifically, in step S30, when the closed-loop control torque T target = 0 and T target =0 and the time t≥t2 is maintained, t2 is the calibration value; or when the output torque value of the engine is positive, that is, when any of the above two situations is met, the anti-lock closed-loop control is exited.

[0092] Furthermore, in step S30, in order to quickly start the anti-lock closed-loop control under severe coasting conditions, the time t1 is determined to be related to the deceleration of the main drive shaft, so the specific calculation formula of the time t1 is:

[0093]

[0094] Among them: a axle The actual deceleration of the main drive shaft, in m / s 2 , a 11 and a 12 These are the deceleration values ​​of the main drive shaft, in m / s 2 , a 11 and a 12 To determine the value, t 11 and t 12 All are time calibration values, in s, t 11 and t 12 To determine the value.

[0095] Specifically, in step S40, when Δ v，m >0, the main drive shaft is in an over-slip state, and the closed-loop control torque T of the transfer case should be increased. target, and the modified proportional integral control parameter k at this time p and k I are all positive; when Δ v，m <0, the main drive shaft is in an under-slip state. At this time, the control parameter factor b of the closed-loop control torque of the transfer case should be determined according to the specific driving conditions of the vehicle such as straight line / turning, so as to reduce the control parameter factor b and thus reduce the closed-loop control torque T of the transfer case. target The falling speed is increased to extend the anti-lock control time, so as to avoid the closed-loop control torque T of the transfer case as much as possible. target The fluctuations in speed cause the vehicle to experience speed fluctuations and deceleration fluctuations.

[0096] Furthermore, if Figure 1 As shown, between step S30 and step S40, there is also a step S35: calculating the modified proportional integral control parameter k p and k I :

[0097]

[0098]

[0099] Among them, k p0 With k I0 is the proportional-integral control parameter.

[0100] Specifically, in step S35, when the vehicle is in a straight-line acceleration condition, due to the closed-loop control torque T target The response is slow and the control accuracy is low. In order to avoid torque fluctuation and speed fluctuation caused by frequent reciprocating anti-lock control, the closed-loop control torque T in the transfer case anti-lock control should be slowed down as much as possible. target The decrease of closed-loop control torque T in the transfer case anti-slip control can be slowed down by adjusting the control parameter factor b. target The decrease of the control parameter factor of the vehicle under different working conditions is calculated, and the control parameter factor b = max(b α , b v , b sw ), where b α is the vehicle's throttle control parameter factor, 0≤b α ≤1, b v is the vehicle speed control parameter factor, 0≤b v ≤1, b sw is the control parameter factor of the vehicle under steering conditions.

[0101] Furthermore, in the straight-line acceleration driving condition, the throttle control parameter factor b of the vehicle is calculated according to the minimum throttle opening. α The calculation formula is:

[0102]

[0103] Among them, is the current throttle opening of the vehicle, a thrsh is the vehicle's throttle opening change threshold, a thrsh It is a calibrated value, usually 2%. When the throttle opening α exceeds a certain level, it indicates that the driver intends to accelerate and increase torque. At this time, the closed-loop control torque of the transfer case can be reduced according to the under-slip state.

[0104] Specifically, due to the vehicle's low-speed and high-speed gliding conditions, b v It decreases with the increase of vehicle speed, and decreases with the decrease of vehicle speed in the low-speed section to avoid excessive intervention of anti-lock control in low-speed and high-speed conditions. Therefore, the vehicle speed control parameter factor b v The calculation formula is:

[0105]

[0106] Where: v3 and v4 are the vehicle speed calibration values, v3 and v4 are determined values, the unit is m / s, b v1 and b v2 are the vehicle speed control parameter calibration values, b v1 and b v2 To determine the value.

[0107] Furthermore, the control parameter factor b of the vehicle under steering conditions is sw The calculation formula is:

[0108] b sw =max(b δ , b ay , b y )b T

[0109] Where: b δ is the vehicle's steering wheel angle control parameter factor, 0≤b δ ≤1,b ay is the vehicle's lateral acceleration control parameter factor, b y is the vehicle's yaw rate control parameter factor, b T It is the torque control parameter factor of the vehicle's steering and sliding condition.

[0110] Specifically, in the turning and sliding driving condition, b δ As the absolute value of the steering wheel angle increases, it increases to avoid the steering braking phenomenon caused by excessive closed-loop control torque of the transfer case under steering conditions. Therefore, the vehicle's steering wheel angle control parameter factor b δ The calculation formula is:

[0111]

[0112] Where: δ is the steering wheel angle of the vehicle, in rad, δ1 and δ2 are the calibrated values ​​of the steering wheel angle of the vehicle, δ1 and δ2 are the determined values, in rad, b δ1 and b δ2 are the calibrated values ​​of the vehicle's steering wheel angle control parameter factors, b δ1 and b δ2 To determine the value.

[0113] Furthermore, in the turning and sliding driving condition, b ay It increases with the increase of the absolute value of lateral acceleration to avoid the steering braking phenomenon caused by excessive closed-loop control torque of the transfer case under steering conditions. Therefore, the vehicle's lateral acceleration control parameter factor b ay The calculation formula is:

[0114]

[0115] Where: ay is the lateral acceleration of the vehicle, ay1 and ay2 are the calibrated values ​​of the lateral acceleration of the vehicle, ay1 and ay2 are the determined values, b ay1 and b ay2 are the calibrated values ​​of the vehicle's lateral acceleration control parameters, b ay1 and b ay2 To determine the value.

[0116] Specifically, in the turning and sliding driving condition, b y As the absolute value of the yaw rate increases, it increases to avoid the steering braking phenomenon caused by excessive closed-loop control torque of the transfer case under steering conditions. Therefore, the vehicle's yaw rate control parameter factor b y The calculation formula is:

[0117]

[0118] Where: y is the yaw rate of the vehicle, y1 and y2 are the calibrated values ​​of the yaw rate of the vehicle, y1 and y2 are the determined values, b y1 and b y2 are the calibrated values ​​of the vehicle's yaw rate control parameter factors, b y1 and b y2 To determine the value.

[0119] Furthermore, since the vehicle is in a turning and sliding condition, b T As the engine's reverse torque increases, the vehicle's steering and sliding torque control parameter factor b T The calculation formula is:

[0120]

[0121] Where: T is the reverse drag torque of the engine under the steering and sliding conditions, T1 and T2 are the calibrated values ​​of the reverse drag torque of the engine under the steering and sliding conditions, T1 and T2 are determined values, b T1 and b T2 are the calibrated values ​​of the engine's anti-drag torque control parameters under the vehicle's steering and sliding conditions, b T1 and b T2 To determine the value.

[0122] The specific control process of the transfer case anti-lock braking control method in this embodiment is as follows: Figure 2 As shown, the front axle is the main drive axle, and the minimum target speed of the vehicle is taken into account:

[0123] First, the preload torque T1 of the transfer case is calculated according to the vehicle speed v to avoid locking of the main drive shaft.

[0124] Afterwards, according to v s，target =min((v m,R cosθ+γLsinθ)(1-λ0),v m,R ),v min =MAP(v x0 , v y0,min ),v s1，target =min(v s，target ,v min ) Calculate the target speed v of the front axle considering the minimum target speed of the vehicle s1，target , where v m,R It is the average of the two wheel speeds at both ends of the rear axle, that is, the average of the left rear wheel and the right rear wheel speeds.

[0125] Then, according to v m，target =max(v s，target , 0), calculate the target speed v of the main drive shaft m，target ; where v m，target =max(v s，target , 0) in the formula s，target is the v calculated above s1，target .

[0126] Then, according to Calculate t1 and according to v m <v m，target (1-λ1) and v m <v m，target (1-λ1) is maintained for a time t≥t1, and it is determined that the vehicle needs to perform anti-lock brake closed-loop control. At this time, the anti-lock brake closed-loop control is started, where v mis the front axle speed, which is the average of the two wheel speeds at both ends of the front axle.

[0127] Afterwards, according to Δ v，m =v m，target -v m Calculate Δ v，m , and according to Δ v，m >0 or Δ v，m <0 It is determined that the vehicle needs to increase the closed-loop control torque T of the transfer case target Or reduce the closed-loop control torque T of the transfer case target The rate of descent.

[0128] Then, according to the working condition of the vehicle, that is, according to b=max(b α , b v , b sw ) Calculate the control parameter factor b.

[0129] Then, according to as well as Calculate the modified proportional integral control parameter k respectively p and k I ; Then according to T target =k p Δ v，m +k I ∫Δ v，m Calculate the closed-loop control torque T of the transfer case that needs to be adjusted in real time under different working conditions target The specific value of .

[0130] Afterwards, according to T t =T1+T target Calculate the transfer case's anti-lock braking control torque T t , so that after the vehicle starts the anti-lock closed-loop control, it can follow T t =T1+T target The calculated T t The value increases or decreases the transfer case's anti-lock control torque to prevent the vehicle from locking.

[0131] Finally, when the anti-lock closed-loop control is activated: when the closed-loop control torque T target = 0 and T target =0 and the time t≥t2 is maintained, t2 is the calibration value; or when the output torque value of the engine is positive, that is, when any one of the above two situations is met, the anti-lock braking closed-loop control is exited, thereby completing the entire vehicle's coasting anti-lock braking control process.

[0132] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, according to the concept of the present invention, there will be changes in the specific implementation methods and application scopes. The content of this specification should not be understood as limiting the present invention.

Claims

1. A transfer case anti-lock braking control method based on a vehicle being in a sliding state, characterized in that: The following steps are involved: S10: Calculation of the preload torque T1 of the transfer case: When the vehicle speed v is v1≤v≤v2, v1 is the first speed value of the vehicle, v2 is the second speed value of the vehicle, T f is the anti-drag torque of the engine of the vehicle, T1≤preload torque upper limit value; S20: Target speed v of the main drive shaft m，target Calculation: v m，target =max(v s，target ,0),v s，target The speed of the main drive shaft in consideration of the steering of the vehicle and the influence of tire lateral deviation; S30: Determine the conditions for anti-lock braking closed-loop control: When v m <v m，target (1-λ1) and v m <v m，target (1-λ1) is maintained for a time t≥t1, then the anti-lock closed-loop control is started, t1 is related to the deceleration of the main drive shaft, v m is the average value of the two wheel speeds at both ends of the main drive shaft, λ1 is the triggering threshold offset of the anti-lock control function under locking conditions; S40: Closed-loop control torque T of the transfer case target Calculation: T target =k p Δ v，m +k I ∫Δ v，m , k p and k I are all modified proportional integral control parameters obtained by modifying the control parameter factor b of the vehicle under the coasting condition, k p and k I It can realize adaptive adjustment according to the vehicle in straight line or turning conditions, Δ v，m is the speed control deviation of the main drive shaft Δ v，m =v m，target -v m ; S50: the transfer case's anti-lock braking control torque T t Calculation: T t =T1+T target , so that after the vehicle starts the anti-lock closed-loop control, it can follow T t =T1+T target The calculated T t The anti-lock braking control torque of the transfer case is increased or decreased by a value, so as to prevent the vehicle from locking; The parameters controlled by the control parameter factor b include: the throttle, vehicle speed, steering wheel angle, lateral acceleration, yaw rate and torque under steering and sliding conditions of the vehicle.

2. The transfer case anti-lock braking control method according to claim 1, characterized in that: In the step S10: when the vehicle speed v is v1>v or v>v2, T1=0.

3. The transfer case anti-lock braking control method according to claim 1, characterized in that: In step S20, when the main drive shaft is the rear shaft: Wherein, λ0 is the target slip rate, θ is the front wheel angle, in rad, γ is the yaw rate of the vehicle, in rad / s, v m,F It is the average speed of the two wheels at both ends of the front axle, in m / s, and L is the wheelbase, in m.

4. The transfer case anti-lock braking control method according to claim 1, characterized in that: In step S20, when the main drive shaft is the front shaft: v s，target =min((v m,R cosθ+γLsinθ)(1-λ0),v m,R ) Wherein, λ0 is the target slip rate, θ is the rear wheel steering angle, in rad, γ is the yaw rate of the vehicle, in rad / s, v m,R is the average speed of the two wheels at both ends of the rear axle, in m / s, and L is the wheelbase, in m.

5. The transfer case anti-lock braking control method according to claim 4, characterized in that: When the main drive shaft is the front axle, and considering the minimum target speed of the vehicle: v s1，target =min(v s，target ,v min ) Among them, v s1，target is the target speed of the front axle considering the minimum target speed of the vehicle, v min To avoid wheel speed accuracy error and jitter when the vehicle is starting and driving at low speed, the minimum speed of the vehicle is determined.

6. The transfer case anti-lock braking control method according to claim 5, characterized in that: The minimum speed v of the vehicle min The calculation formula is: v min =MAP(v x0 ,v y0,min ) Where: v x0 and v y0,min All are calibrated values, v x0 =[0 1 2 5 10 20 100], v y0,min =[2 1.5 1.2 10.50.2 0.2].

7. The transfer case anti-lock braking control method according to claim 1, characterized in that: In step S30, when the anti-lock braking closed-loop control is activated: When the closed-loop control torque T target = 0 and T target = 0 and the time t≥t2, t2 is the calibration value; or When the output torque value of the engine is positive, the anti-lock closed-loop control is exited.

8. The transfer case anti-lock braking control method according to claim 1, characterized in that: In step S30, the calculation formula of time t1 is: Among them: a axle is the actual deceleration of the main drive shaft, in m / s 2 , a 11 and a 12 are the calibrated values ​​of the deceleration of the main drive shaft, in m / s 2 , a 11 and a 12 To determine the value, t 11 and t 12 All are time calibration values, in s, t 11 and t 12 To determine the value.

9. The transfer case anti-lock braking control method according to claim 1, characterized in that: In step S40: when Δ v，m >0, the main drive shaft is in an over-slip state, and the closed-loop control torque T of the transfer case should be increased. target , at this time, k p and k I is a positive value; when Δ v，m <0, the main drive shaft is in an under-slip state, and the control parameter factor b is reduced to reduce the closed-loop control torque T of the transfer case. target The descent speed can extend the anti-lock closed-loop control time.

10. The transfer case anti-lock braking control method according to claim 1, characterized in that: The step S35 is further included between the step S30 and the step S40: calculating a modified proportional integral control parameter k p and k I : Among them, k p0 With k I0 is the proportional-integral control parameter.

11. The transfer case anti-lock braking control method according to claim 10, characterized in that: In step S35, the control parameter factor b=max(b α , b v , b sw ); Among them, b α is the throttle control parameter factor of the vehicle, 0≤b α ≤1, b v is the vehicle speed control parameter factor, 0≤b v ≤1, b sw is the control parameter factor of the vehicle under steering conditions.

12. The transfer case anti-lock braking control method according to claim 11, characterized in that: The throttle control parameter factor b of the vehicle α The calculation formula is: Wherein, a is the current throttle opening of the vehicle, a thrsh is the throttle opening change threshold value of the vehicle, a thrsh is the calibration value.

13. The transfer case anti-lock braking control method according to claim 11, characterized in that: The vehicle speed control parameter factor b v The calculation formula is: Where: v3 and v4 are the speed calibration values ​​of the vehicle, v3 and v4 are determined values, the unit is m / s, b v1 and b v2 are the calibrated values ​​of the vehicle speed control parameters, b v1 and b v2 To determine the value.

14. The transfer case anti-lock braking control method according to claim 11, characterized in that: The control parameter factor b of the vehicle under steering conditions sw The calculation formula is: b sw =max(b δ ,b ay ,b y )b T Where: b δ is the steering wheel angle control parameter factor of the vehicle, 0≤b δ ≤1,b ay is the lateral acceleration control parameter factor of the vehicle, b y is the yaw rate control parameter factor of the vehicle, b T is the torque control parameter factor of the vehicle in the steering and sliding condition.

15. The transfer case anti-lock braking control method according to claim 14, characterized in that: The vehicle's steering wheel angle control parameter factor b δ The calculation formula is: Where: δ is the steering wheel angle of the vehicle, in rad, δ1 and δ2 are the calibrated values ​​of the steering wheel angle of the vehicle, δ1 and δ2 are the determined values, in rad, b δ1 and b δ2 are the steering wheel angle control parameter factor calibration values ​​of the vehicle, b δ1 and b δ2 To determine the value.

16. The transfer case anti-lock braking control method according to claim 14, characterized in that: The lateral acceleration control parameter factor b of the vehicle ay The calculation formula is: Wherein: ay is the lateral acceleration of the vehicle, ay1 and ay2 are the calibrated values ​​of the lateral acceleration of the vehicle, ay1 and ay2 are the determined values, b ay1 and b ay2 are the lateral acceleration control parameter calibration values ​​of the vehicle, b ay1 and b ay2 To determine the value.

17. The transfer case anti-lock braking control method according to claim 14, characterized in that: The vehicle's yaw rate control parameter factor b y The calculation formula is: Where: y is the yaw rate of the vehicle, y1 and y2 are the calibrated values ​​of the yaw rate of the vehicle, y1 and y2 are the determined values, b y1 and b y2 are the calibrated values ​​of the yaw rate control parameter factors of the vehicle, b y1 and b y2 To determine the value.

18. The transfer case anti-lock braking control method according to claim 14, characterized in that: The vehicle's steering and sliding torque control parameter factor b T The calculation formula is: Where: T is the torque of the vehicle under the steering and sliding condition, T1 and T2 are the torque calibration values ​​of the vehicle under the steering and sliding condition, T1 and T2 are the determined values, b T1 and b T2 are the torque control parameter calibration values ​​of the vehicle under the steering and sliding conditions, b T1 and b T2 To determine the value.

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