阅读说明：本技术 在线的车辆行驶控制区域划分及区域边界估计方法 (Online vehicle driving control area division and area boundary estimation method ) 是由 李梓涵 王萍 刘胜涛 林佳眉 胡云峰 陈虹 于 2021-06-11 设计创作，主要内容包括：一种在线的车辆行驶控制区域划分及区域边界估计方法,属于车辆安全技术领域。本发明的目的是根据驾驶员行为及行驶路况信息,考虑车辆横-纵-垂向动力学特性,在线得到关于质心侧偏角和横摆角速度控制区域的在线的车辆行驶控制区域划分及区域边界估计方法。本发明步骤是：软件联合仿真设置及车辆模型搭建；车辆行驶控制区域划分及边界估计。本发明将控制区域划分为稳定区、不稳定区和作为过渡区域的临界稳定区,并为不同的区域赋予不同的控制需求,可以更好地开发控制区域在稳定性控制中的应用潜能。(An online vehicle running control area division and area boundary estimation method belongs to the technical field of vehicle safety. The invention aims to obtain an online vehicle running control area division and area boundary estimation method related to a centroid side deviation angle and a yaw rate control area on line according to the behavior of a driver and the information of the running road condition and by considering the lateral-longitudinal-vertical dynamic characteristics of a vehicle. The method comprises the following steps: setting software combined simulation and building a vehicle model; and dividing a vehicle running control area and estimating a boundary. The control area is divided into a stable area, an unstable area and a critical stable area serving as a transition area, different control requirements are given to different areas, and the application potential of the control area in stability control can be better developed.)

1. An on-line vehicle driving control area dividing and area boundary estimating method comprises the following steps:

s1, setting software joint simulation and building a vehicle model;

s2, vehicle driving control area division and boundary estimation

(1) Steady region boundary estimation

Firstly, establishing a vehicle dynamic model

② tire model

Part linearization of non-linear model

The method is characterized in that:

(2) control region partitioning

Forming transition region and dividing region

The areas of beta and gamma are updated in real time along with the steering, driving/braking behaviors of a driver and road condition information and are changed correspondingly, and the area formed by the boundary at the lowest vehicle speed in the current interval is defined as a stable area R1 in the vehicle speed interval; and a boundary under the condition of the highest vehicle speed in the current interval, wherein a region outside the boundary is an unstable region R3 in the current vehicle speed interval, an inner region formed by the boundary is overlapped with the stable region R1 which is just obtained, and the non-overlapped region part is defined as a critical stable region R2 which is used as a transition region of the stable region and the unstable region; the current vehicle state (β, γ) is in a region, and the control demand for the vehicle stability changes in each region as follows:

the control requirements for each zone are introduced as follows: in the stable region R1, where the maneuverability and lateral stability of the vehicle can be ensured, the tire longitudinal anti-skid performance can be considered, the tire is prevented from locking up, and the energy consumption can be considered; when the vehicle state enters the critical stability region R2, it should be ensured as much as possible that the vehicle state can return to the stable region, so that the control demand regarding the steering stability and the lateral stability is increased, and as the vehicle state gradually moves away from R1 in R2, the demand gravity center for the tire longitudinal slip prevention and the energy consumption should also gradually shift to the steering stability and the lateral stability of the vehicle; in the unstable region R3, the primary control requirement is to ensure maneuverability and lateral stability to ensure driving safety;

region position judgment

For the division of the control area, the area position to which the current vehicle state (β, γ) belongs needs to be judged in real time so as to judge the control requirement that the current vehicle state needs to meet, if the current vehicle state (β, γ) is known, and the fitted β on each boundary is known_matAnd gamma_matAre all in one-to-one correspondence, then each boundary can be written as a function β of the centroid yaw angle with respect to the yaw rate_mat(γ_mat) Therefore, can pass through the function β_mat(γ_mat) Obtain each boundary a_in,b_in,a_out,b_outC, d is the beta value under the current gamma, namely the coordinate of the gamma value on each boundary is (beta)_ain,γ),(β_bin,γ),(β_aout,γ),(β_bout,γ),(β_c,γ),(β_dγ), comparing their abscissa values with β values fed back from the vehicle, respectively, i.e. judging the area where the current vehicle state (β, γ) is located by the following relation:

if the current centroid slip angle and yaw rate (beta, gamma) of the vehicle are known, the control area to which the vehicle currently belongs can be determined according to the relation (12).

Technical Field

The invention belongs to the technical field of vehicle safety.

Background

In the vehicle running process, the vehicle state can change in real time according to the road condition and the behavior of a driver, for the stability of the vehicle, the vehicle state which intuitively reflects the maneuverability and the stability can be described as a control area, and a stable area, an unstable area and the like can be divided according to the stability boundary condition, so that the method is applied to the vehicle stability control. Yaw rate, centroid and side slip angle, etc. as important states representing yaw and side motion of a vehicle, vehicle handling performance and side stability can be generally described by using control areas related to the yaw and side motion, and the following problems exist in the current research on vehicle driving control area division and area boundary estimation:

1. most of the existing vehicle running control areas adopt a phase plane formed by a centroid slip angle and a centroid slip angle speed, a stable area is divided according to the change characteristics of the phase plane, and for a moving vehicle, particularly under a limit working condition, the offline area cannot provide reliable vehicle safety evaluation in real time.

2. The control area is divided, boundary conditions of each area can be obtained according to vehicle dynamics, and most of the existing control area dividing methods only consider the lateral motion of the vehicle, do not consider dynamics in other directions and coupling of dynamics among all directions, so that estimation of the area boundary and area division are not accurate enough.

3. In terms of control area applications, most of the existing methods only divide the control area into a stable area and an unstable area, and only consider the same control performance to be achieved in different areas, which limits the application potential of the control area in vehicle stability control.

Disclosure of Invention

The invention aims to obtain an online vehicle running control area division and area boundary estimation method related to a centroid side deviation angle and a yaw rate control area on line according to the behavior of a driver and the information of the running road condition and by considering the lateral-longitudinal-vertical dynamic characteristics of a vehicle.

The method comprises the following steps:

s1, setting software joint simulation and building a vehicle model;

s2, vehicle driving control area division and boundary estimation

(1) Steady region boundary estimation

Firstly, establishing a vehicle dynamic model

② tire model

Part linearization of non-linear model

(2) Control region partitioning

Forming transition region and dividing region

The areas of beta and gamma are updated in real time along with the steering, driving/braking behaviors of a driver and road condition information and are changed correspondingly, and the area formed by the boundary at the lowest vehicle speed in the current interval is defined as a stable area R1 in the vehicle speed interval; and a boundary under the condition of the highest vehicle speed in the current interval, wherein a region outside the boundary is an unstable region R3 in the current vehicle speed interval, an inner region formed by the boundary is overlapped with the stable region R1 which is just obtained, and the non-overlapped region part is defined as a critical stable region R2 which is used as a transition region of the stable region and the unstable region; the current vehicle state (β, γ) is in a region, and the control demand for the vehicle stability changes in each region as follows:

the control requirements for each zone are introduced as follows: in the stable region R1, where the maneuverability and lateral stability of the vehicle can be ensured, the tire longitudinal anti-skid performance can be considered, the tire is prevented from locking up, and the energy consumption can be considered; when the vehicle state enters the critical stability region R2, it should be ensured as much as possible that the vehicle state can return to the stable region, so that the control demand regarding the steering stability and the lateral stability is increased, and as the vehicle state gradually moves away from R1 in R2, the demand gravity center for the tire longitudinal slip prevention and the energy consumption should also gradually shift to the steering stability and the lateral stability of the vehicle; in the unstable region R3, the primary control requirement is to ensure maneuverability and lateral stability to ensure driving safety;

region position judgment

For the division of the control area, the area position to which the current vehicle state (β, γ) belongs needs to be judged in real time so as to judge the control requirement that the current vehicle state needs to meet, if the current vehicle state (β, γ) is known, and the fitted β on each boundary is known_matAnd gamma_matAre all in one-to-one correspondence, then each boundary can be written as a function β of the centroid yaw angle with respect to the yaw rate_mat(γ_mat) Therefore, can pass through the function β_mat(γ_mat) Obtain each boundary a_in,b_in,a_out,b_outC, d is the beta value under the current gamma, namely the coordinate of the gamma value on each boundary is (beta)_ain,γ),(β_bin,γ),(β_aout,γ),(β_bout,γ),(β_c,γ),(β_dγ), comparing their abscissa values with β values fed back from the vehicle, respectively, i.e. judging the area where the current vehicle state (β, γ) is located by the following relation:

if the current centroid slip angle and yaw rate (beta, gamma) of the vehicle are known, the control area to which the vehicle currently belongs can be determined according to the relation (12).

The invention has the beneficial effects that:

1. the control area formed by the yaw angular velocity and the centroid slip angle is adopted, the maneuverability and the stability of the vehicle can be better described, the boundaries of each area can change in real time along with the behavior of a driver and road information, and compared with most of traditional control methods using an off-line phase plane area, more reliable vehicle safety evaluation can be provided;

2. the method only considers the lateral motion dynamics of the vehicle, neglects other directions and the coupling characteristics between the other directions, is based on the lateral-longitudinal-vertical dynamics characteristics of the vehicle, considers the influence of road conditions on vertical loads, and can enable the region estimation to be more accurate so as to be convenient to apply;

3. the control area is divided into a stable area, an unstable area and a critical stable area serving as a transition area, different control requirements are given to different areas, and the application potential of the control area in stability control can be better developed.

Drawings

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a schematic representation of a vehicle dynamics model of the present invention;

FIG. 3 is a graph of lateral force versus slip angle for different road adhesion coefficients in accordance with the present invention;

FIG. 4 is a schematic view of the control zone boundary of the present invention with the vehicle at V_xThe vehicle runs on a straight road with a road surface adhesion coefficient of 0.35 as 60km/h, wherein a solid line is a controllable condition boundary, a dotted line is a stable condition boundary, the ordinate is a yaw velocity in rad/s, and the abscissa is a centroid slip angle in rad;

FIG. 5 is a schematic diagram of the boundary and the division of the control area according to the present invention, wherein the vehicle runs on a straight road with a road surface adhesion coefficient of 0.35, and the vehicle speed is in the range of 60-65km/h, wherein the solid line is the controllable boundary, the double-dashed line is the inner boundary of the stable condition obtained at a speed of 60km/h, the dash-dot line is the outer boundary of the stable condition obtained at a speed of 65km/h, the area formed by the inner boundary and the controllable boundary is the stable area R1, the area formed by the inner and outer boundaries is the critical stable area R2, and the other parts are all regarded as the unstable area R3;

FIG. 6 is a control area division and boundary condition of the present invention when the vehicle speed is in the range of 60-65km/h, the steering wheel angle is 45 degrees, the road surface has no slope, and the adhesion coefficient is 0.35;

FIG. 7 is a control area division and boundary condition thereof when the vehicle speed is in the range of 75-80km/h, no steering action, no gradient of the road surface and the adhesion coefficient is 0.35 according to the invention;

FIG. 8 is a control area division and boundary condition thereof when the vehicle speed is in the range of 60-65km/h, no steering action, no gradient of the road surface and the adhesion coefficient is 0.8 according to the present invention;

FIG. 9 shows the control area division and its boundary conditions when the vehicle speed is in the range of 60-65km/h, no steering action, the composite road gradient of 6% and the adhesion coefficient of 0.35.

Detailed Description

The flow chart of the control region division and boundary estimation method is shown in fig. 1, wherein road environment information and vehicle measurement states are collected from vehicle dynamics simulation software CarSim, a vehicle yaw and lateral motion dynamics model is established, a nonlinear tire model is used for describing tire lateral force, local linearization is carried out on the nonlinear vehicle dynamics model through Taylor expansion and local linearization, a yaw angular velocity and a centroid yaw angle which meet stability conditions are screened out based on the relationship between the tire force and the yaw angle in the tire model, and the yaw angular velocity and the centroid yaw angle are fitted to form a region boundary; and then the boundaries of each speed interval are synthesized, the area can be divided into a stable area, a critical stable area and an unstable area, the boundaries of each area can be obtained according to the online estimation of the behavior of a driver and the road condition information, and each area corresponds to different vehicle stability control requirements. The vehicle model and the simulation working condition are constructed in CarSim, and the others are constructed in MATLAB/Simulink.

The invention aims to realize the division of a control area and the real-time estimation of the boundary of each divided area during the running process of a vehicle.

The invention provides a set of devices based on the operation principle and the operation process. The construction and operation processes are as follows:

1. software joint simulation setting and vehicle model building

A simulation model of a controller and a controlled object of the control system is respectively built through software MATLAB/Simulink and CarSim, the software versions are MATLAB R2016a and CarSim 2016.1, and the simulation step length is 0.001 s. To realize the joint simulation of MATLAB/Simulink and CarSim, firstly, the working path of CarSim is set as a specified Simulink Model, then the set vehicle Model and road information in CarSim are added into Simulink, and Simulink is operated so as to realize the joint simulation and communication of the two. If the model structure or parameter settings in the CarSim are modified, a retransmission is required.

CarSim is used as high-fidelity vehicle dynamics software to simulate real controlled objects, and the vehicle model used in the invention is constructed based on east wind A60, and the parameters are shown in Table I.

Vehicle model parameter table

2. Vehicle travel control area division and boundary estimation

As described above, the present invention obtains each control area boundary regarding yaw rate and centroid slip angle on-line according to driver behavior and road condition information based on vehicle lateral-longitudinal-vertical dynamics. Firstly, establishing a nonlinear vehicle dynamics model and a tire model, carrying out local linearization on the nonlinear vehicle dynamics model and the tire model, screening out a yaw angular velocity and a mass center slip angle which reasonably meet the system stability, fitting the yaw angular velocity and the mass center slip angle into a region boundary, and taking the formed region as a stable region, wherein the operation stability and the lateral stability of a vehicle in the region can be effectively ensured, and performances such as vehicle skid resistance and the like are required to be considered; then, synthesizing the stable region boundaries obtained from each vehicle speed interval to form a transition region between a stable region and an unstable region, called a critical stable region, wherein the region needs to ensure the vehicle maneuverability and the longitudinal and lateral stability and needs to make the vehicle return to the stable region as much as possible; while the remaining region serves as an unstable region in which the handling stability of the vehicle should be a performance that is to be ensured first.

The specific method of the present invention for control region partitioning and boundary estimation is described as follows:

1) steady region boundary estimation

Firstly, establishing a vehicle dynamic model

First, a dynamic model is built considering the yaw and lateral motion of the vehicle, a schematic diagram of which is shown in fig. 2, and the model is described as follows:

wherein beta is the vehicle mass center slip angle, gamma is the vehicle yaw velocity, delta_fFor turning the front wheel, F_yRepresenting the tire side force, the combination of subscript i e f r, j e l r, where ij f j f j f i f i f i f i n f i n f i f.

② tire model

In order to describe the tire lateral force more accurately, the Fiala tire model is adopted, the model takes the tire slip angle as an internal variable, the saturation nonlinear characteristic of the tire force can be better reflected, and the calculation can be described as follows:

wherein μ is a road surface adhesion coefficient, F_zFor vertical loading, C_iIs the nominal cornering stiffness of the front or rear wheel of the tyre; α is the tire slip angle, which is calculated as follows:

vertical load of tyreThe calculation takes into account the load redistribution on the slope when the vehicle is turning, where a_x,a_yRespectively represent the longitudinal acceleration and the lateral acceleration,is a roll angle, η_h,η_cRespectively representing the slopes of the lateral road and the longitudinal road, and concretely calculating as follows:

wherein the content of the first and second substances,to synthesize the road grade, h_φIs the side-tipping moment arm of the arm,is the angle of the side rake,for front and rear suspension roll stiffness, k_l＝-k_rThe calculation can more accurately consider the distribution of the vertical load of the tire on the complex road surface as-1.

The relationship of the lateral force to the slip angle for different road surface adhesion coefficients is shown in fig. 3, and the yaw value of the tire lateral force with respect to the slip angle can be considered as the transient tire cornering stiffness at the current slip angle.

Part linearization of non-linear model

The vehicle dynamics model (1) is locally linearized by means of a taylor expansion, described in the following form with respect to linearization points and increments:

wherein the content of the first and second substances,β_o、γ_oand delta_foRespectively representing the linearization points of each value,Δβ、Δγ、Δδ_fthe increment of each value is represented separately, and the increment part in equation (5) can be described as follows:

wherein the content of the first and second substances,

in the derivation process, only the lateral force is regarded as a function of the slip angle, soNamely, the tire cornering stiffness C can be obtained according to the deviation of the cornering angle by the lateral force in the tire model (2)_α。

The partial derivatives of α versus β and γ can be obtained from equation (3) as follows:

and then according to equations (1) and (7).

After finishing, the following can be obtained:

by solving matricesIs obtained under the condition that the stability of the system is obtainedNamely, the stable condition and the controllable condition of the system are as follows:

C_αfl+C_αfr≠0, (10)

according to the boundary conditions (9) and (10), by the wheelThe relation between the tire force and the cornering angle in the tire model (2) obtains the cornering stiffness of the tire, and C meeting the conditions is selected from the cornering stiffness_αflAnd C_αfrAnd correspondingly obtaining the slip angle alpha_flAnd alpha_frThen, the mass center slip angle and the yaw rate meeting the conditions are converted through the following changes:

plotting all eligible points (. beta.)_mat,γ_mat) And fitting the points as the boundary of the control region. Taking the case that the vehicle runs on a straight road with a road surface adhesion coefficient of 0.35 and the speed is 60km/h, drawing the control area boundary at this time as shown in fig. 4, wherein a dotted line is a stable condition boundary and also represents an oversteer boundary; the solid line is the controllable condition boundary and also represents the understeer boundary.

2) Control region partitioning

The transition area formation and area division are carried out according to the steering, driving/braking behaviors of a driver and road condition information, wherein the areas related to beta and gamma are obtained by the boundary, and the road condition information is updated in real time and changed correspondingly. Analysis and verification show that the area can be expanded along with the increase of the vehicle speed, can be translated along with the steering of the vehicle, can be reduced along with the reduction of the road adhesion coefficient, and is less influenced by the gradient change. In order to improve the real-time performance of the boundary of the control area obtained on line, the vehicle speed is divided into several intervals of 50-55km/h, 55-60km/h,60-65km/h,65-70km/h,70-75km/h and 75-80km/h, and the stable condition boundaries obtained under all vehicle speeds in the current interval are synthesized, so that an area formed by the boundary under the lowest vehicle speed in the current interval can be obtained and is defined as a stable area R1 under the vehicle speed interval; and a boundary under the condition of the highest vehicle speed in the current section, wherein the region outside the boundary is an unstable region R3 in the current vehicle speed section, an inner region formed by the boundary is overlapped with the stable region R1 which is just obtained, and the non-overlapped region part is defined as a critical stable region R2 which is used as a transition region between the stable region and the unstable region.

To be more intuitively fixedDefining the respective regions, taking the case where the vehicle runs on a straight road having a road surface friction coefficient of 0.35 and the vehicle speed is within 60-65km/h as an example, the control region of the vehicle speed section is plotted as shown in FIG. 5, a_inAnd b_inIs a V_xThe stable condition boundary obtained at 60km/h is called inner boundary; a is_outAnd b_outIs a V_xThe stable condition boundary obtained at 65km/h is called outer boundary; c and d are controllable condition boundaries; and the region formed by the inner boundary and the controllable boundary is defined as a stable region R1, the region formed by the inner boundary and the outer boundary is defined as a critical stable region R2, and the rest parts are regarded as unstable regions R3.

As described above, different control demands need to be considered for the respective regions, and if the region in which the current vehicle state (β, γ) is known, the control demand change with respect to the vehicle stability in each region is as shown in the following table.

Control of demand changes in regions of the watch two

The control requirements for each zone are described below in conjunction with the table: in the stable region R1, where the maneuverability and lateral stability of the vehicle can be ensured, the tire longitudinal anti-skid performance can be considered, the tire is prevented from locking up, and the energy consumption can be considered; when the vehicle state enters the critical stability region R2, it should be ensured as much as possible that the vehicle state can return to the stable region, so that the control demand regarding the steering stability and the lateral stability is increased, and as the vehicle state gradually moves away from R1 in R2, the demand gravity center for the tire longitudinal slip prevention and the energy consumption should also gradually shift to the steering stability and the lateral stability of the vehicle; in the unstable region R3, the primary control requirement is to ensure handling and lateral stability and thus driving safety. The above control requirements can be switched in different areas by the objective function and its weight value in the controller design, and the change and adjustment of the constraint conditions.

Region position judgment

Based on the above controlThe division of the control region needs to judge the region position to which the current vehicle state (beta, gamma) belongs in real time so as to judge the control requirement which needs to be met by the current vehicle state. If the current vehicle state (β, γ) is known, and β on each boundary of the fit is known_matAnd gamma_matAre all in one-to-one correspondence, then each boundary can be written as a function β of the centroid yaw angle with respect to the yaw rate_mat(γ_mat) Therefore, can pass through the function β_mat(γ_mat) Obtain each boundary a_in,b_in,The beta value under the current gamma is used for obtaining the coordinate (beta) of the gamma value on each boundary_ain,γ),(β_bin,γ),(β_aout,γ),(β_bout,γ),(β_c,γ),(β_dγ), comparing their abscissa values with β values fed back from the vehicle, the area where the current vehicle state (β, γ) is located can be determined by the following relationship:

in summary, if the current centroid slip angle and yaw rate (β, γ) of the vehicle are known, the control region to which the vehicle currently belongs can be determined according to the relationship (12). In addition, for different road information and driver behaviors, the third table lists some driving conditions, and the division of the control area and the boundaries of each area under the conditions are shown in fig. 6-9.

Region division and boundary under table three different road information and driver behaviors