CN108595745B - Method and system for determining vehicle phase plane stable region - Google Patents
Method and system for determining vehicle phase plane stable region Download PDFInfo
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- CN108595745B CN108595745B CN201810177896.9A CN201810177896A CN108595745B CN 108595745 B CN108595745 B CN 108595745B CN 201810177896 A CN201810177896 A CN 201810177896A CN 108595745 B CN108595745 B CN 108595745B
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Abstract
The invention discloses a method and a system for determining a vehicle phase plane stable region. The determination method comprises the following steps: obtaining vehicle parameters; establishing a nonlinear tire model by utilizing a Dugoff tire formula according to the vehicle parameters; determining the vehicle tire cornering power according to the nonlinear tire model; obtaining a current wheel corner; determining a vehicle phase plane stability region of a centroid slip angular velocity-centroid slip angle phase diagram according to the wheel rotation angle by using the nonlinear tire model and a linear vehicle model; the phase plane stable region includes a closed quadrilateral and a closed triangle. According to the determining method and the determining system provided by the invention, the stable area of the vehicle phase plane can be accurately divided, so that the judgment precision of the vehicle stability is improved.
Description
Technical Field
The invention relates to the field of vehicle stability judgment, in particular to a method and a system for determining a vehicle phase plane stable region.
Background
With the development of technologies, people have higher and higher requirements on the safety of vehicles, and many technologies are used to improve the safety and stability of vehicles. However, since the vehicle is a nonlinear system, it is difficult to determine whether the running vehicle is still in a stable state, that is, it cannot be determined whether the vehicle can return to a corresponding stable point by itself, and it is difficult to implement stability and safety control.
For determining a stable region of a vehicle phase plane, the phase plane method is very important for determining the stability of a nonlinear vehicle system. The phase plane method can analyze the stability of the nonlinear system, the solution is not needed for the high nonlinear system such as a vehicle, the phase trajectory of the vehicle system and the corresponding phase diagram under a series of initial values of the vehicle state are drawn according to the phase plane method under a certain working condition, and based on the phase diagram, whether the phase trajectory regresses to a stable point or not can be determined, so that the stable region of the corresponding vehicle can be automatically regressed to the stable point when the vehicle is in which states under the working condition.
At present, most of phase plane methods are centroid slip angular velocity-centroid slip angle phase diagrams, that is, a phase plane stable region of a vehicle in a phase plane is established by taking the centroid slip angular velocity and the centroid slip angle of the vehicle as a vehicle state basis for vehicle stability judgment. For the current method for determining the phase plane stable region of the phase diagram of the centroid slip angular velocity-centroid slip angle, the method mainly comprises the following steps: 1. establishing a corresponding whole vehicle simulation model according to the linear two-degree-of-freedom bicycle model and the tire model, and establishing a corresponding vehicle dynamic model in matlab-simulink; 2. and (3) setting a series of different vehicle state (centroid slip angle, centroid slip angle speed) simulation initial values under the input of a certain determined working condition (vehicle speed and road surface adhesion coefficient), inputting the working condition into the whole vehicle simulation Simulink model in the step (3), and obtaining a corresponding phase locus through a series of different vehicle state simulation initial values so as to finally form a phase plane under the input of the currently determined working condition. 3. And (3) dividing a phase plane stable region according to whether the phase trajectory regresses to a stable point or not according to the phase plane diagram obtained in the step (3), and finally taking two fitted straight lines which are symmetrical about the stable point center as the boundary of the stable region on the phase plane, thereby determining the phase plane stable region in the step (3). 4. Changing the determined working condition input in the step 3 and repeating the steps 2 and 3, thereby obtaining corresponding stable areas of the vehicle under different working conditions and establishing a phase plane stable area library of the vehicle. 5. After the stable region library of the vehicle is established, for the judgment of the stability of the vehicle under any working condition, the judgment result of whether the current vehicle is stable can be obtained only by judging whether the state of the current vehicle belongs to the phase plane region under the corresponding working condition in the phase plane vehicle stable region library.
For the above conventional centroid slip angular velocity and centroid slip angular velocity phase diagram, there is actually a partially unstable region in the vehicle phase plane stable region divided by two symmetrical straight lines, such as the stable region of the original centroid slip angular velocity-centroid slip angular velocity phase diagram under a certain working condition shown in fig. 1, the middle of the two straight lines of the phase plane is the stable region of the vehicle, the phase plane stable region is an open stable region divided by regions and contains many unstable phase trajectory curves, the phase plane trajectory 1 is the phase trajectory curve returning to the stable point, and the phase trajectory 2 and the phase trajectory curve below the phase trajectory 2 (there is a corresponding unstable region above the phase trajectory curve due to the symmetry of the conventional centroid slip angular velocity-centroid slip angle) are regions not returning to the stable point and therefore the regions below the phase trajectory 2 should be unstable, once the vehicle mass center slip angle is formed, when the mass center slip angular velocity state is located in an area below the phase track 2 (or located above a symmetrical phase track), the current state of the vehicle is judged to be stable according to the original mass center slip angular velocity-mass center slip angular velocity method, so that the stable state of the vehicle is judged incorrectly, and great hidden danger is caused to the safety of the vehicle.
In addition, for the original phase plane method, the influence of the change of the vehicle speed and the adhesion coefficient on the stable area of the phase plane of the vehicle is judged under the condition that the front wheel rotation angle of the vehicle is set to be 0 for changing the working condition in the step 4; the front wheel steering angle of the vehicle does not always remain unchanged, and the front wheel steering angle can greatly affect the phase plane stable region of the phase diagram of the centroid slip angle speed-centroid slip angle of the vehicle, so that when the front wheel steering angle is not zero under the actual working condition, the situation of misjudgment can occur for judging the stability of the vehicle by adopting the original phase diagram of the centroid slip angle speed-centroid slip angle. Therefore, although the phase plane method of the current method for judging the phase plane stable region of the vehicle can well determine the phase plane stable region of the vehicle, the current phase plane method divides the stable region of the vehicle into open regions including partial unstable regions, thereby causing great errors in judging the stability of the vehicle.
Disclosure of Invention
The invention aims to provide a method and a system for determining a vehicle phase plane stable region, which are used for solving the problem of large vehicle stability judgment error caused by inaccurate division of the vehicle phase plane stable region in the prior art.
In order to achieve the purpose, the invention provides the following scheme:
a vehicle phase plane stability region determination method, comprising:
obtaining vehicle parameters; the vehicle parameters comprise vehicle speed, adhesion coefficient and front wheel rotation angle;
establishing a nonlinear tire model by utilizing a Dugoff tire formula according to the vehicle parameters;
determining the vehicle tire cornering power according to the nonlinear tire model; the vehicle tire cornering power comprises a front wheel tire cornering power and a rear wheel tire cornering power;
establishing a linear vehicle model according to the vehicle tire lateral deviation force;
obtaining a current wheel corner;
determining a vehicle phase plane stability region of a centroid slip angular velocity-centroid slip angle phase diagram according to the wheel rotation angle by using the nonlinear tire model and a linear vehicle model; the centroid side slip angular velocity-centroid side slip angle phase diagram comprises a first centroid side slip angular velocity-centroid side slip angle phase diagram and a second centroid side slip angular velocity-centroid side slip angle phase diagram; the phase plane stable region includes a closed quadrilateral and a closed triangle.
Optionally, the establishing a non-linear tire model by using a dugoff tire formula according to the vehicle parameters specifically includes:
according to the formula
Establishing a nonlinear tire model;
wherein, FyIs the tire side deflection force of the front wheel tire or the tire side deflection force of the rear wheel tire, K is the tire side deflection rigidity of the front wheel tire or the rear wheel tire, theta is the tire side deflection angle of the front wheel tire or the rear wheel tire, mu is the current road surface adhesion coefficient, FzThe load is the front axle vertical load or the rear axle vertical load.
Optionally, the establishing a linear vehicle model according to the vehicle tire cornering power specifically includes:
according to the formula
Establishing a linear vehicle model;
wherein, ayIs a dieLateral acceleration of type MzIs a yaw moment of the vehicle, FyfIs the tire sidewall bias force of the front wheel, FyrIs the tire side bias of the rear wheel, delta is the front wheel corner of the vehicle, m is the total vehicle mass, LfIs the front wheelbase of the vehicle, LrIs the rear wheelbase of the vehicle.
Optionally, the determining, according to the wheel rotation angle, a vehicle phase plane stability region of the centroid slip angle velocity-centroid slip angle phase diagram by using the nonlinear tire model and the linear vehicle model specifically includes:
judging whether the front wheel steering angle is 0 or not to obtain a first judgment result;
if the first judgment result shows that the corner of the front wheel is 0, acquiring a first vehicle speed and a first adhesion coefficient;
determining a vehicle phase plane stability region of a first centroid slip angular velocity-centroid slip angle phase diagram according to the first vehicle speed and the first adhesion coefficient by using the nonlinear tire model and the linear vehicle model; a phase plane stable region in the first centroid slip angular velocity-centroid slip angle phase diagram is a closed quadrangle;
if the second judgment result shows that the front wheel turning angle is not 0, acquiring a second vehicle speed and a second adhesion coefficient;
determining a vehicle phase plane stability region of a second centroid slip angle speed-centroid slip angle phase diagram according to the second vehicle speed and the second adhesion coefficient by using the nonlinear tire model and the linear vehicle model; and a phase plane stable region in the second centroid slip angular velocity-centroid slip angle phase diagram is a closed triangle.
Optionally, the determining, according to the first vehicle speed and the first adhesion coefficient, a vehicle phase plane stable region of a first centroid slip angle speed-centroid slip angle phase diagram by using the nonlinear tire model and the linear vehicle model specifically includes:
according to the formula
Determining a phase plane stable region of a first centroid slip angular velocity-centroid slip angle phase diagram;
wherein a is the abscissa of the intersection point of the first boundary of the phase plane stable region and the centroid side deflection angle axis, and b1Is the ordinate of the intersection of the second boundary of the phase plane stability region and the centroid yaw angular velocity axis, k is the slope of the first boundary, β is the centroid yaw angle,
is the centroid slip angular velocity.
Optionally, the determining, according to the second vehicle speed and the second adhesion coefficient, a vehicle phase plane stable region of a second centroid slip angle speed-centroid slip angle phase diagram by using the nonlinear tire model and the linear vehicle model specifically includes:
according to the formula
Determining a phase plane stable region of a second centroid slip angular velocity-centroid slip angle phase diagram;
wherein, a1Is the intercept of the third boundary of the phase plane stable region and the centroid side off-angle axis, a2Intercept of the fourth boundary of the phase plane stability region with the centroid side off-angle axis, b2Is the ordinate, k, of the fifth boundary of the phase plane stable region and the centroid sideslip angular velocity axis1Is the slope of the third boundary, k2Is the slope of the fourth boundary.
A vehicle phase plane stability region determination system comprising:
the vehicle parameter acquisition module is used for acquiring vehicle parameters; the vehicle parameters comprise vehicle speed, adhesion coefficient and front wheel rotation angle;
the nonlinear tire model establishing module is used for establishing a nonlinear tire model by utilizing a Dugoff tire formula according to the vehicle parameters;
the vehicle tire cornering power determining module is used for determining the vehicle tire cornering power according to the nonlinear tire model; the vehicle tire cornering power comprises a front wheel tire cornering power and a rear wheel tire cornering power;
the linear vehicle model building module is used for building a linear vehicle model according to the vehicle tire lateral deviation force;
the current wheel corner acquisition module is used for acquiring a current wheel corner;
a vehicle phase plane stable region determination module for determining a vehicle phase plane stable region of a centroid slip angular velocity-centroid slip angle phase diagram according to the wheel rotation angle by using the nonlinear tire model and a linear vehicle model; the centroid side slip angular velocity-centroid side slip angle phase diagram comprises a first centroid side slip angular velocity-centroid side slip angle phase diagram and a second centroid side slip angular velocity-centroid side slip angle phase diagram; the phase plane stable region includes a closed quadrilateral and a closed triangle.
Optionally, the nonlinear tire model building module specifically includes:
a non-linear tire model building unit for building a tire model based on a formula
Establishing a nonlinear tire model;
wherein, FyIs the tire side deflection force of the front wheel tire or the tire side deflection force of the rear wheel tire, K is the tire side deflection rigidity of the front wheel tire or the rear wheel tire, theta is the tire side deflection angle of the front wheel tire or the rear wheel tire, mu is the current road surface adhesion coefficient, FzThe load is the front axle vertical load or the rear axle vertical load.
Optionally, the linear vehicle model building module specifically includes:
a linear vehicle model building unit for building a linear vehicle model according to the formula
Establishing a linear vehicle model;
wherein, ayAs lateral acceleration of the model, MzIs a yaw moment of the vehicle, FyfIs the tire sidewall bias force of the front wheel, FyrIs the tire side bias of the rear wheel, delta is the front wheel corner of the vehicle, m is the total vehicle mass, LfIs a vehicleFront wheelbase of the vehicle, LrIs the rear wheelbase of the vehicle.
Optionally, the vehicle phase plane stable region determining module specifically includes:
the first judgment unit is used for judging whether the front wheel steering angle is 0 or not to obtain a first judgment result;
a first vehicle speed and first adhesion coefficient obtaining unit, configured to obtain a first vehicle speed and a first adhesion coefficient if the first determination result indicates that the front wheel rotation angle is 0;
a vehicle phase plane stable region determination unit of a first centroid slip angular velocity-centroid slip angle phase diagram, configured to determine a first centroid slip angular velocity-centroid slip angle phase diagram using the nonlinear tire model and the linear vehicle model according to the first vehicle speed and the first adhesion coefficient; a phase plane stable region in the first centroid slip angular velocity-centroid slip angle phase diagram is a closed quadrangle;
a second vehicle speed and second adhesion coefficient acquisition unit configured to acquire a second vehicle speed and a second adhesion coefficient if the second determination result indicates that the front wheel turning angle is not 0;
a vehicle phase plane stable region determination unit of a second centroid side slip angular velocity-centroid side slip angle phase diagram, configured to determine a vehicle phase plane stable region of the second centroid side slip angular velocity-centroid side slip angle phase diagram by using the nonlinear tire model and the linear vehicle model according to the second vehicle speed and the second adhesion coefficient; and a phase plane stable region in the second centroid slip angular velocity-centroid slip angle phase diagram is a closed triangle.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects: the invention provides a method and a system for determining a vehicle phase plane stable region, wherein a nonlinear tire model and a linear vehicle model are established according to vehicle parameters, and a vehicle phase plane stable region in a centroid side deflection angular velocity-centroid side deflection angular phase diagram determined according to the two models is closed, so that the division of the closed vehicle phase plane stable region determined by the method is more accurate compared with the vehicle phase plane stable region in an open region, the unstable region is greatly reduced, the judgment of the vehicle stability is more accurate, and the stability control of a vehicle is more reliable;
secondly, the method and the system for determining the phase plane stable region of the vehicle provided by the invention directly obtain the current wheel corner without considering the condition that the front wheel corner is 0, and comprehensively consider the influence of the front wheel corner on the phase plane stable region, thereby ensuring that the judgment of the vehicle stability is more accurate.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic view of a stable region determined by a primary phase plane method provided by the present invention;
FIG. 2 is a flow chart of the simulation model construction and phase plane analysis provided by the present invention;
FIG. 3 is a flow chart of a method for determining a stable area of a phase plane of a vehicle according to the present invention;
FIG. 4 is a two-degree-of-freedom vehicle model diagram of the vehicle provided by the present invention;
FIG. 5 is a schematic view of a phase plane stability region of a vehicle with a front wheel angle of 0 provided by the present invention;
FIG. 6 is a schematic view of a phase plane stability region of a vehicle when a front wheel steering angle is not 0 according to the present invention;
FIG. 7 is a flow chart of two types of phase plane stable region division provided by the present invention;
fig. 8 is a structural diagram of a vehicle phase plane stable region determination system provided by the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a method and a system for determining a phase plane stable region of a vehicle, which can improve the accuracy of dividing the phase plane stable region of the vehicle so as to determine whether the vehicle is in a stable state more accurately.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
In order to obtain the phase plane stable region of the following vehicle, a corresponding whole vehicle simulation model needs to be established firstly. The model mainly comprises two parts: the vehicle simulation model is composed of a linear vehicle model and a non-linear tire model, and the non-linearity of the whole vehicle simulation model is embodied by the tire model. The structure of the complete vehicle simulation model for phase plane analysis and the corresponding analysis process are shown in the following fig. 2.
Fig. 3 is a flowchart of a method for determining a stable region of a vehicle phase plane according to the present invention, and as shown in fig. 3, the method for determining a stable region of a vehicle phase plane includes:
step 301: obtaining vehicle parameters; the vehicle parameters comprise vehicle speed, adhesion coefficient and front wheel rotation angle.
Step 302: and establishing a nonlinear tire model by utilizing a Dugoff tire formula according to the vehicle parameters.
For the built finished automobile simulation model, the nonlinearity of the model is reflected in the selection of the tire model, so that the invention selects a Dugoff tire formula to build a corresponding tire model, and the tire cornering power is generated according to the model as follows:
wherein the content of the first and second substances,Fyis the tire side deflection force of the front wheel tire or the tire side deflection force of the rear wheel tire, K is the tire side deflection rigidity of the front wheel tire or the rear wheel tire, theta is the tire side deflection angle of the front wheel tire or the rear wheel tire, mu is the current road surface adhesion coefficient, FzThe load is the front axle vertical load or the rear axle vertical load.
As can be seen from the above equation, the tire cornering force can be obtained as long as the cornering angle of the tire is input, and therefore the cornering angles of the front and rear tires are obtained from the kinematic relationship in fig. 2 as follows,
wherein, afAs lateral acceleration of the vehicle, arIs the longitudinal acceleration of the vehicle, vxIs the longitudinal speed, v, of the vehicleyIs the lateral velocity of the vehicle, w is the yaw rate of the vehicle, LfIs the front wheelbase of the vehicle, LrIs the rear wheelbase of the vehicle and β is the centroid slip angle.
In practical applications, the non-linear tire model may be replaced by other empirical models or other corresponding theoretical derivation models, such as a magic formula tire model, so as to establish the same phase plane analysis model.
Step 303: determining the vehicle tire cornering power according to the nonlinear tire model; the vehicle tire cornering forces include a front wheel tire cornering force and a rear wheel tire cornering force.
Step 304: and establishing a linear vehicle model according to the vehicle tire lateral deviation force.
Assuming that the vehicle longitudinal acceleration is 0, the longitudinal speed of the vehicle remains unchanged. According to the linear two-degree-of-freedom bicycle model, because the longitudinal acceleration is zero, the longitudinal force is not considered, and a corresponding kinematic formula is established for the longitudinal direction and the horizontal swing of the linear two-degree-of-freedom bicycle model as follows:
wherein M iszIs a yaw moment of the vehicle, IzIs the moment of inertia of the vehicle. In addition, because the mass center slip angle of the vehicle is the ratio of the lateral speed and the longitudinal speed of the vehicle, and because the longitudinal speed of the current model is a fixed value, the vehicle model is divided into two parts
According to the lateral force situation of the two-degree-of-freedom model shown in FIG. 4, therefore, ayAnd MzAs follows:
Mz＝Fyfcosδ·Lf-Fyr·Lr，
wherein, ayAs lateral acceleration of the model, MzIs a yaw moment of the vehicle, FyfIs the tire sidewall bias force of the front wheel, FyrIs the tire side bias of the rear wheel, delta is the front wheel corner of the vehicle, m is the total vehicle mass, LfIs the front wheelbase of the vehicle, LrIs the rear wheelbase of the vehicle.
Step 305: and acquiring the current wheel rotation angle.
Step 306: determining a vehicle phase plane stability region of a centroid slip angular velocity-centroid slip angle phase diagram according to the wheel rotation angle by using the nonlinear tire model and a linear vehicle model; the centroid side slip angular velocity-centroid side slip angle phase diagram comprises a first centroid side slip angular velocity-centroid side slip angle phase diagram and a second centroid side slip angular velocity-centroid side slip angle phase diagram; the phase plane stable region includes a closed quadrilateral and a closed triangle.
Establishing a corresponding complete vehicle simulation model for phase plane analysis in a simulation platform (MATLAB/Simulink), compiling a corresponding M function, and drawing a series of different vehicle state initial values under a certain working condition input through the established Simulink simulation model
And the corresponding vehicle phase tracks form a vehicle phase plane diagram. In the invention, the working condition input mainly comprises a front wheel corner, a vehicle speed and a road adhesion coefficient which have the largest influence on a vehicle stable area. For the division of the corresponding phase plane stable region, the phase plane stable region can be divided into a quadrangle stable region and a triangle stable region according to whether the front wheel rotation angle is 0, preferably, the quadrangle stable region can be a parallelogram; in addition, the stable region in the invention is divided without calculating the stable region under the negative front wheel steering angle, and the centroid slip angle speed-centroid slip angle phase diagram under the condition can be symmetrically obtained from the center of the corresponding positive front wheel steering angle. The corresponding phase plane stability region can be divided into two categories according to whether the front wheel steering angle is 0:
first, dividing the stable area of the phase plane of the vehicle when the front wheel corner is 0
The remaining vehicle speed and the adhesion coefficient in the operating condition were set at 10m/s, 20m/s, 25m/s, 30m/s, 35m/s, 40m/s, and 0.2, 0.4, 0.6, 0.8, and 1.0. For a certain combination of the above operating conditions, the centroid slip angle speed-centroid slip angle phase diagram of the vehicle under the operating condition can be obtained according to the previous simulink model and is shown in fig. 5.
As can be seen from fig. 5, when the front wheel rotation angle is 0, the phase plane stable region of the vehicle is a parallelogram surrounded by four straight lines, which are stable region boundaries dividing the stable flow pattern returning to the stable point and the unstable flow pattern in the phase plane, but due to the symmetry of each phase trajectory of the vehicle phase plane, the vehicle stable boundary only needs to determine two straight lines L1And L2And (4) finishing. And due to L2Is a straight line with zero slope, so ultimately only the straight line L needs to be determined1Abscissa a and straight line L of intersection point of centroid side deviation angle axis1Slope k, straight line L2Ordinate b of intersection point of centroid side deviation angular velocity axis1These three data volumes are sufficient. Wherein, the straight line L1And L2Between a stable flow pattern and an unstable flow pattern in the phase plane, a and b can be represented byDirect read-out, straight line L1The slope k of (a) can be obtained from a certain feature point A (x, y) and a on the straight line:
it can be concluded that the phase plane stability region of the vehicle under this condition satisfies the following formula:
And dividing the stable areas of the vehicle phase planes under other working condition combinations to obtain 60 stable areas covering the mass center slip angle speed-mass center slip angle phase plane of the vehicle under most actual working condition inputs when the front wheel rotation angle is 0. Thereby establishing a corresponding vehicle phase plane stable area library.
Two, vehicle phase plane stable region division when front wheel steering angle is not zero
The front wheel steering angle is set to be 2 degrees, 4 degrees, 6 degrees and 8 degrees, and the vehicle speed and the road surface adhesion coefficient are set according to the first class, so that corresponding working condition setting is completed.
Under a certain combination of the above working conditions, a centroid slip angle velocity-centroid slip angle phase diagram of the vehicle under the working condition can be obtained according to the simulink model of the phase plane analysis in the foregoing, as shown in fig. 6.
As can be seen from fig. 6, when the front wheel steering angle of the vehicle is not zero, the stable region of the vehicle is a triangular region surrounded by three straight lines, which are the boundaries of the stable region of the stable flow pattern and the unstable flow pattern returning to the stable point in the divided phase plane. It can be seen that the stability zone is not zero when the front wheel steering angle is zeroThe domain may vary widely. To determine the stable area of the phase plane of the vehicle under this condition, the straight line L in the graph needs to be determined1，L2Slope k of1，k2And the intercept a of the straight line and the centroid side off-angle axis1，a2Due to the straight line L3Has a slope of 0, so that only the intersection point b of the center of mass and the yaw rate axis needs to be determined2That is, 5 pieces of data are required to determine the stability boundary and thus the stability region thereof under the condition that the front wheel steering angle is not zero. The determination of the above data is performed in the same manner as the corresponding data acquisition of the straight lines in the first category. And therefore, the stable area of the vehicle phase plane under the working condition meets the following formula:
And dividing the stable areas of the vehicle phase planes under other working condition combinations to obtain 240 stable areas which are formed by combining the front wheel rotation angle with the vehicle speed and the adhesion coefficient and cover the mass center slip angle speed-mass center slip angle phase plane of the vehicle under most actual working condition inputs. Thereby establishing a corresponding vehicle phase plane stable region library, and fig. 7 is a flow chart of two phase plane stable region division types provided by the invention, as shown in fig. 7.
Regarding the vehicle stability determination:
after the vehicle phase plane stable region library is established, the vehicle stability judging steps are as follows: firstly, entering different vehicle stability area libraries according to whether the front wheel steering angle under the current working condition is zero or not; secondly, according to the speed and the road adhesion coefficient of the current working condition, carrying out interpolation according to the phase plane stable area library established in the front so as to obtain 3 or 5 data for determining the boundary of the vehicle stable area under the current vehicle working condition; and finally, obtaining a judgment result of whether the vehicle is stable or not according to whether the centroid slip angle speed and the centroid slip angle of the current vehicle are positioned in the phase plane stable region determined in the front.
Fig. 8 is a structural diagram of a vehicle phase plane stable region determination system provided by the present invention, and as shown in fig. 8, a vehicle phase plane stable region determination system includes:
a vehicle parameter obtaining module 801, configured to obtain vehicle parameters; the vehicle parameters comprise vehicle speed, adhesion coefficient and front wheel rotation angle.
A non-linear tire model building module 802 for building a non-linear tire model using the dugoff tire formula based on the vehicle parameters.
A vehicle tire cornering power determination module 803 for determining a vehicle tire cornering power from the non-linear tire model; the vehicle tire cornering forces include a front wheel tire cornering force and a rear wheel tire cornering force.
And the linear vehicle model building module 804 is used for building a linear vehicle model according to the vehicle tire cornering power.
And a current wheel rotation angle obtaining module 805 for obtaining a current wheel rotation angle.
A vehicle phase plane stability region determination module 806 for determining a vehicle phase plane stability region of a centroid slip angle velocity-centroid slip angle phase diagram using the non-linear tire model and a linear vehicle model according to the wheel rotation angle; the centroid side slip angular velocity-centroid side slip angle phase diagram comprises a first centroid side slip angular velocity-centroid side slip angle phase diagram and a second centroid side slip angular velocity-centroid side slip angle phase diagram; the phase plane stable region includes a closed quadrilateral and a closed triangle.
In practical applications, the nonlinear tire model building module 802 specifically includes:
a non-linear tire model building unit for building a tire model based on a formula
Establishing a nonlinear tire model;
wherein, FyIs the tire side deflection force of the front wheel tire or the tire side deflection force of the rear wheel tire, K is the tire side deflection rigidity of the front wheel tire or the rear wheel tire, theta is the tire side deflection angle of the front wheel tire or the rear wheel tire, mu is the current road surface adhesion coefficient, FzThe load is the front axle vertical load or the rear axle vertical load.
In practical applications, the linear vehicle model building module 803 specifically includes:
a linear vehicle model building unit for building a linear vehicle model according to the formula
Establishing a linear vehicle model;
wherein, ayAs lateral acceleration of the model, MzIs a yaw moment of the vehicle, FyfIs the tire sidewall bias force of the front wheel, FyrIs the tire side bias of the rear wheel, delta is the front wheel corner of the vehicle, m is the total vehicle mass, LfIs the front wheelbase of the vehicle, LrIs the rear wheelbase of the vehicle.
In practical applications, the vehicle phase plane stable region determining module 806 specifically includes:
the first judgment unit is used for judging whether the front wheel steering angle is 0 or not to obtain a first judgment result;
a first vehicle speed and first adhesion coefficient obtaining unit, configured to obtain a first vehicle speed and a first adhesion coefficient if the first determination result indicates that the front wheel rotation angle is 0;
a vehicle phase plane stable region determination unit of the first centroid slip angular velocity-centroid slip angle phase diagram, configured to determine a vehicle phase plane stable region of the first centroid slip angular velocity-centroid slip angle phase diagram by using the nonlinear tire model and the linear vehicle model according to the first vehicle speed and the first adhesion coefficient; a phase plane stable region in the first centroid slip angular velocity-centroid slip angle phase diagram is a closed quadrangle;
a second vehicle speed and second adhesion coefficient acquisition unit configured to acquire a second vehicle speed and a second adhesion coefficient if the second determination result indicates that the front wheel turning angle is not 0;
a vehicle phase plane stable region determination unit of a second centroid side slip angular velocity-centroid side slip angle phase diagram, configured to determine a vehicle phase plane stable region of the second centroid side slip angular velocity-centroid side slip angle phase diagram by using the nonlinear tire model and the linear vehicle model according to the second vehicle speed and the second adhesion coefficient; and a phase plane stable region in the second centroid slip angular velocity-centroid slip angle phase diagram is a closed triangle.
Compared with the original centroid slip angular velocity-centroid slip angle phase plane method, the method also adds the influence of the front wheel rotation angle of the vehicle into the vehicle stability area division, so that the established phase plane stability area library is more accurate; the method considers the influence of the front wheel corner on the phase plane stable region, and obtains the method for dividing the vehicle stable region when the front wheel corner is not 0, so that the stable region obtained by the phase plane method is more accurate; compared with an open vehicle stable area determined by an original centroid slip angular velocity-centroid slip angle phase plane method, the invention provides an improved closed vehicle phase plane stable area, namely when the corner of a front wheel provided by the invention is 0, the vehicle phase plane stable area is a quadrangle; when the corner of the front wheel of the vehicle is not 0, the stable area of the vehicle phase plane is triangular.
And because the closed type vehicle phase plane stable region is divided, the division of the vehicle phase plane stable region is more accurate, compared with the original stable region, the unstable part is greatly reduced, the judgment of the vehicle stability is more accurate, and the control of the vehicle stability is more reliable.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (8)
1. A vehicle phase plane stability region determination method, comprising:
obtaining vehicle parameters; the vehicle parameters comprise vehicle speed, adhesion coefficient and front wheel rotation angle;
establishing a nonlinear tire model by utilizing a Dugoff tire formula according to the vehicle parameters;
determining the vehicle tire cornering power according to the nonlinear tire model; the vehicle tire cornering power comprises a front wheel tire cornering power and a rear wheel tire cornering power;
establishing a linear vehicle model according to the vehicle tire lateral deviation force;
obtaining a current wheel corner;
determining a vehicle phase plane stability region of a centroid slip angular velocity-centroid slip angle phase diagram according to the wheel rotation angle by using the nonlinear tire model and a linear vehicle model; the centroid side slip angular velocity-centroid side slip angle phase diagram comprises a first centroid side slip angular velocity-centroid side slip angle phase diagram and a second centroid side slip angular velocity-centroid side slip angle phase diagram; the phase plane stable region comprises a closed quadrangle and a closed triangle;
according to the wheel rotation angle, the vehicle phase plane stable region of the centroid slip angle speed-centroid slip angle phase diagram is determined by utilizing the nonlinear tire model and the linear vehicle model, and the method specifically comprises the following steps:
judging whether the front wheel steering angle is 0 or not to obtain a first judgment result;
if the first judgment result shows that the corner of the front wheel is 0, acquiring a first vehicle speed and a first adhesion coefficient;
determining a vehicle phase plane stability region of a first centroid slip angular velocity-centroid slip angle phase diagram according to the first vehicle speed and the first adhesion coefficient by using the nonlinear tire model and the linear vehicle model; a phase plane stable region in the first centroid slip angular velocity-centroid slip angle phase diagram is a closed quadrangle;
if the first judgment result shows that the front wheel turning angle is not 0, acquiring a second vehicle speed and a second adhesion coefficient;
determining a vehicle phase plane stability region of a second centroid slip angle speed-centroid slip angle phase diagram according to the second vehicle speed and the second adhesion coefficient by using the nonlinear tire model and the linear vehicle model; and a phase plane stable region in the second centroid slip angular velocity-centroid slip angle phase diagram is a closed triangle.
2. The method of claim 1, wherein the building a non-linear tire model using the dugoff tire equation based on the vehicle parameters specifically comprises:
according to the formula
Establishing a nonlinear tire model;
wherein, FyIs the tire side deflection force of the front wheel tire or the tire side deflection force of the rear wheel tire, K is the tire side deflection rigidity of the front wheel tire or the rear wheel tire, theta is the tire side deflection angle of the front wheel tire or the rear wheel tire, mu is the current road surface adhesion coefficient, FzThe load is the front axle vertical load or the rear axle vertical load.
3. The method for determining according to claim 1, wherein said building a linear vehicle model from said vehicle tire cornering power comprises:
according to the formula
Establishing a linear vehicle model;
wherein, ayAs lateral acceleration of the model, MzIs a yaw moment of the vehicle, FyfIs the tire sidewall bias force of the front wheel, FyrIs the tire side bias of the rear wheel, delta is the front wheel corner of the vehicle, m is the total vehicle mass, LfIs the front wheelbase of the vehicle, LrIs the rear wheelbase of the vehicle.
4. The method of determining according to claim 1, wherein determining the vehicle phase plane stability region of the first centroid slip angle velocity-centroid slip angle phase diagram using the non-linear tire model and the linear vehicle model based on the first vehicle speed and the first adhesion coefficient comprises:
according to the formula
Determining a phase plane stable region of a first centroid slip angular velocity-centroid slip angle phase diagram;
wherein a is the abscissa of the intersection point of the first boundary of the phase plane stable region and the centroid side deflection angle axis, and b1Is the ordinate of the intersection of the second boundary of the phase plane stability region and the centroid yaw angular velocity axis, k is the slope of the first boundary, β is the centroid yaw angle,
is the centroid slip angular velocity.
5. The method according to claim 4, wherein the determining a vehicle phase plane stability region of a second centroid slip angle velocity-centroid slip angle phase diagram using the nonlinear tire model and the linear vehicle model based on the second vehicle speed and the second adhesion coefficient comprises:
according to the formula
Determining a second centroidA phase plane stability region of the slip angular velocity-centroid slip angle phase diagram;
wherein, a1Is the intercept of the third boundary of the phase plane stable region and the centroid side off-angle axis, a2Intercept of the fourth boundary of the phase plane stability region with the centroid side off-angle axis, b2Is the ordinate, k, of the fifth boundary of the phase plane stable region and the centroid sideslip angular velocity axis1Is the slope of the third boundary, k2Is the slope of the fourth boundary.
6. A vehicle phase plane stability region determination system, comprising:
the vehicle parameter acquisition module is used for acquiring vehicle parameters; the vehicle parameters comprise vehicle speed, adhesion coefficient and front wheel rotation angle;
the nonlinear tire model establishing module is used for establishing a nonlinear tire model by utilizing a Dugoff tire formula according to the vehicle parameters;
the vehicle tire cornering power determining module is used for determining the vehicle tire cornering power according to the nonlinear tire model; the vehicle tire cornering power comprises a front wheel tire cornering power and a rear wheel tire cornering power;
the linear vehicle model building module is used for building a linear vehicle model according to the vehicle tire lateral deviation force;
the current wheel corner acquisition module is used for acquiring a current wheel corner;
a vehicle phase plane stable region determination module for determining a vehicle phase plane stable region of a centroid slip angular velocity-centroid slip angle phase diagram according to the wheel rotation angle by using the nonlinear tire model and a linear vehicle model; the centroid side slip angular velocity-centroid side slip angle phase diagram comprises a first centroid side slip angular velocity-centroid side slip angle phase diagram and a second centroid side slip angular velocity-centroid side slip angle phase diagram; the phase plane stable region comprises a closed quadrangle and a closed triangle;
the vehicle phase plane stable region determination module specifically comprises:
the first judgment unit is used for judging whether the front wheel steering angle is 0 or not to obtain a first judgment result;
a first vehicle speed and first adhesion coefficient obtaining unit, configured to obtain a first vehicle speed and a first adhesion coefficient if the first determination result indicates that the front wheel rotation angle is 0;
a vehicle phase plane stable region determination unit of the first centroid slip angular velocity-centroid slip angle phase diagram, configured to determine a vehicle phase plane stable region of the first centroid slip angular velocity-centroid slip angle phase diagram by using the nonlinear tire model and the linear vehicle model according to the first vehicle speed and the first adhesion coefficient; a phase plane stable region in the first centroid slip angular velocity-centroid slip angle phase diagram is a closed quadrangle;
a second vehicle speed and second adhesion coefficient acquisition unit, configured to acquire a second vehicle speed and a second adhesion coefficient if the first determination result indicates that the front wheel steering angle is not 0;
a vehicle phase plane stable region determination unit of a second centroid side slip angular velocity-centroid side slip angle phase diagram, configured to determine a vehicle phase plane stable region of the second centroid side slip angular velocity-centroid side slip angle phase diagram by using the nonlinear tire model and the linear vehicle model according to the second vehicle speed and the second adhesion coefficient; and a phase plane stable region in the second centroid slip angular velocity-centroid slip angle phase diagram is a closed triangle.
7. The determination system according to claim 6, wherein the non-linear tire model building module comprises in particular:
a non-linear tire model building unit for building a tire model based on a formula
Establishing a nonlinear tire model;
wherein, FyIs the tire side deflection force of the front wheel tire or the tire side deflection force of the rear wheel tire, K is the tire side deflection rigidity of the front wheel tire or the rear wheel tire, theta is the tire side deflection angle of the front wheel tire or the rear wheel tire, mu is the current road surface adhesion coefficient, FzThe load is the front axle vertical load or the rear axle vertical load.
8. The determination system according to claim 6, wherein the linear vehicle model building module specifically comprises:
a linear vehicle model building unit for building a linear vehicle model according to the formula
Establishing a linear vehicle model;
wherein, ayAs lateral acceleration of the model, MzIs a yaw moment of the vehicle, FyfIs the tire sidewall bias force of the front wheel, FyrIs the tire side bias of the rear wheel, delta is the front wheel corner of the vehicle, m is the total vehicle mass, LfIs the front wheelbase of the vehicle, LrIs the rear wheelbase of the vehicle.
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| CN111497825A (en) * | 2020-03-31 | 2020-08-07 | 南京航空航天大学 | Phase space vehicle stability judging method |
| CN112572411B (en) * | 2020-12-22 | 2021-09-07 | 北京理工大学 | Vehicle chassis coordination control method and system considering tire cornering characteristic |
| CN112752691B (en) * | 2020-12-30 | 2022-04-26 | 华为技术有限公司 | Vehicle front and rear driving torque distribution method and device and vehicle |
| CN113008240B (en) * | 2021-03-01 | 2021-12-14 | 东南大学 | Four-wheel independent drive intelligent electric vehicle path planning method based on stable domain |
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