CN109635516B - Method for predicting dangerous area of difference of turning inner wheels of large vehicle - Google Patents
Method for predicting dangerous area of difference of turning inner wheels of large vehicle Download PDFInfo
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Abstract
The invention discloses a method for predicting a dangerous area with poor turning inner wheel of a large vehicle, which comprises the following steps: 1, judging a turning stage of a vehicle, establishing a simulation coordinate system, and inputting related parameters; 2, performing coordinate simulation based on the algorithm model of the invention, calculating a simulated driving curve of the vehicle and predicting; and 3, outputting the dangerous area of the vehicle. The invention can predict the running track of the vehicle in the next period of time according to the control condition of the driver on the vehicle and the vehicle state, and obtain the predicted dangerous area, thereby improving the turning safety of large-sized vehicles.
Description
Technical Field
The invention belongs to the field of active early warning of automobiles, and particularly relates to a method for predicting a dangerous area of a turning track of an automobile by using instantaneous parameters of the automobile.
Background
With the development of science and technology, the number of large vehicles is increasing day by day, and in recent years, traffic accidents are getting more serious while the road transportation industry is vigorously developed. Vehicle steering accidents, particularly major vehicle steering accidents, are more severe and frequent than other traffic accidents. The statistical data of the administration of public security department shows that 5.04 thousands of truck responsibility road traffic accidents occur in 2016 years all over the country, resulting in 2.5 thousands of people dying and 4.68 thousands of people being injured, which respectively account for 30.5%, 48.23% and 27.81% of the total amount of the truck responsibility accidents, and are much higher than the ratio of the truck inventory to the total amount of the trucks.
In all papers or patents published in China, modeling calculation for dangerous areas is few and few, but at present, in China, deep research and development are lacked in the aspect, and due to the complexity of the areas, errors are easily generated in subjective judgment, and accidents are very easily caused. Because only one qualitative understanding exists at present in the dangerous area, the dangerous area is an important reason for causing traffic accidents or damaging road surfaces by scratch and graze edges for large-sized vehicles.
Just because of the lack of understanding and research on dangerous areas at present, the incidence rate of accidents is high, and the safety of large-sized vehicles during turning is greatly reduced;
disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a method for predicting a dangerous area with poor turning inner wheel of a large-sized vehicle, so that the running track of the vehicle in the next period can be predicted according to the control condition of the driver on the vehicle and the vehicle state, and the predicted dangerous area can be obtained, and the turning safety of the large-sized vehicle can be improved.
The invention adopts the following technical scheme for solving the technical problems:
the invention relates to a method for predicting a dangerous area of a large-scale vehicle turning inner wheel difference, which is characterized by comprising the following steps of:
step 1, establishing a dangerous area theoretical model of the wheel difference in turning of the large vehicle:
step 1.1, dividing a vehicle turning process into three stages, including a bending stage, a stabilizing stage and a correcting stage;
the bending stage is as follows: rate of change of front wheel steering angle
Constant and positive, constant vehicle speed u, yaw rate omega r Constant;
the stabilization phase is as follows: front wheel corner alpha 2 Constant, constant vehicle speed u, yaw angular velocity omega r Constant;
the correcting stage is as follows: rate of change of front wheel angle
Constant and negative, constant vehicle speed u, yaw rate omega r Constant;
step 1.2, establishing a theoretical model of the dangerous area in the bending stage and calculating the dangerous area in the bending stage:
step 1.2.1, obtaining the instantaneous turning radius rho of the automobile by using the formula (1):
in the formula (1), a is the wheel base of the front wheel of the automobile, b is the wheel base of the rear wheel of the automobile, and alpha 1 Is a rear wheel side slip angle, α 2 Is a front wheel corner; and comprises the following components:
tanα 2 ＝(v+ω r a)/(u-ω r d) (2)
tanα 1 ＝(v-ω r b)/(u-ω r d) (3)
in the formulas (2) and (3), v is the speed perpendicular to the direction of the vehicle speed u, and d is the length between the center of mass of the vehicle and a connecting line between the centers of the front wheel and the rear wheel;
step 1.2.2, obtaining the average speed u of the front wheel of the automobile in the bending stage by using the formula (4) L ：
In the formula (4), alpha is the instantaneous turning angle of the front wheel of the automobile;
step 1.2.3, obtaining the front wheel corner alpha by using the formula (5) 2 From initial zero degree to alpha 2max Time t:
in the formula (5), α 2max The maximum rotation angle of the front wheel and the maximum radius rho according to the instantaneous rotation of the automobile max Is equal to the turning radius r of the road surface;
step 1.2.4, obtaining the distance s of the front wheel of the automobile in the time t by using the formula (6):
s＝u L t (6)
step 1.2.5, establishing a turning model coordinate system o-xy by taking the position of a front wheel when a vehicle turns into a curve as an origin o, taking the instantaneous speed direction of the front wheel turning into the curve as an x axis and taking the instantaneous speed direction vertical to the turning into the curve of the front wheel as a y axis; and the maximum included angle alpha between the central axis of the mass center and the x axis of the automobile in the bending stage is obtained by using the formula (7) 0max ：
α 0max ＝tω r (7)
Step 1.2.6, obtaining the maximum included angle beta between the track of the front wheel of the automobile and the x axis by using the formula (8) max ：
β max ＝α 0max +α 2max (8)
Step 1.2.7, establishing an equation set shown as a formula (9), and obtaining a terminal point seat M of the front wheel track in the bending stage 1 (x 1 ,y 1 ) Distance c between the center of the road surface circle and the x-axis 1 And front wheel track curve parameter A 1 ：
Step 1.2.8, setting the coordinates of the front wheel of the automobile in the bending stage as (x) 1 ',y 1 ') the coordinates of the rear wheel of the car in the bending stage are (x) 1 '-(a+b)cosα 0 ,y 1 '+(a+b)sinα 0 ) And is used as a theoretical model of the dangerous area in the bending stage; taking a running track of coordinates of a rear wheel of the automobile in the bending stage as a dangerous area of the automobile in the bending stage; wherein alpha is 0 The included angle between the central axis of the mass center and the x axis when the automobile is in a bending stage;
step 1.3, establishing a dangerous area theoretical model in a stable stage and calculating a dangerous area in the stable stage:
obtaining the turning radius r of the front wheel in the stable stage by using the formula (10) 1 And the turning radius r of the rear wheel in the stabilization phase 2 And according to the turning radius r of the rear wheel in the stable stage 2 Obtaining the running track of the coordinates of the rear wheel of the automobile and using the running track as a dangerous area theoretical model in a stable stage to stabilize the running track of the coordinates of the rear wheel of the automobile in the stable stageAs a danger zone in the cornering phase of the vehicle;
step 1.4, establishing a return-to-normal stage dangerous area theoretical model and calculating a dangerous area in a return-to-normal stage:
step 1.4.1, establishing a turning model coordinate system o '-x' y 'by taking the position of a front wheel when a vehicle bends as an origin o', taking the bending instantaneous speed direction of the front wheel as an x 'axis and taking the bending instantaneous speed direction vertical to the front wheel as a y' axis;
establishing an equation set shown as a formula (11), and obtaining a coordinate M of a starting point of the front wheel track in the aligning stage 2 (x 2 ,y 2 ) Distance c between the center of the road surface circle and the x' axis 2 And front wheel track curve parameter A 2 ：
Step 1.4.2, setting the coordinates of the front wheel of the automobile in the turning-back segment to be (x' 2 ,y′ 2 ) Then the coordinates of the rear wheel of the return stage automobile are (x' 2 +(a+b)cosα 0 ,y′ 2 +(a+b)sinα 0 ) And is used as a dangerous area theoretical model of the correcting stage; taking the running track of the coordinates of the rear wheels of the automobile in the aligning stage as a dangerous area of the automobile in the bending stage;
step 2, judging the turning stage according to the change value of the front wheel steering angle and the change rate of the front wheel steering angle:
step 2.1, when Δ α 2 ＞k 1 Is greater than 0 and
when the automobile enters the bending stage, the automobile enters the bending stage;
when in use
And-k 3 ＜Δα 2 ＜k 3 When, it means the vehicle enters a stable phase;
when in use
And Δ α 2 ＜k 5 If the value is less than 0, the automobile enters a stable stage; wherein, k 1 ，k 2 ，k 3 ，k 4 ，k 5 Δ α as an adjustable sensitivity parameter 2 Is the variation of the front wheel corner;
step 2.2, predicting the dangerous area in the bending stage:
step 2.2.1, obtaining automobile parameters in the bending stage, including: instantaneous speed u of a motor vehicle 1 Yaw angular velocity ω r1 The wheel base a of the front wheel of the automobile, the wheel base b of the rear wheel of the automobile, the distance d between the center of mass of the automobile and the center line of the front wheel and the center line of the rear wheel of the automobile and the corner alpha of the front wheel' 2 Rate of change of instantaneous turning angle of front wheel of automobile
Step 2.2.2, obtaining the simulation time t' of the automobile in the curve by using the formula (12):
step 2.2.3, obtaining an included angle alpha between a center axis of a mass center and an x axis of the automobile in a bending stage by using the formula (13) 0 ′：
α′ 0 ＝ω r1 t′ (13)
Step 2.2.4, obtaining an included angle beta' between the track of the front wheel of the automobile and the x axis according to the formula (14):
β′＝α′ 0 +α′ 2 (14)
step 2.2.5, obtaining the average speed u 'of the front wheel of the automobile in the bending-in stage according to the formula (16)' L ；
In the formula (15), alpha is an interval [0, alpha' 2 ]An integration section of (1);
step 2.2.6, obtaining the distance s 'of the front wheel of the automobile under the simulation time t' according to the formula (16):
s′＝u′ L t′ (16)
step 2.2.7, setting the coordinates of the front wheels of the vehicle in the turning model coordinate system o ' -x ' y ' as Q (x ″) 1 ,y″ 1 ) (ii) a And establishing an equation set shown as the formula (17) to obtain a front wheel track curve parameter A 1 ', to obtain the trajectory profile of the front wheel during the approach bending stage:
in formula (17), x' is the interval [0,x 2 ]An integration section of (1);
step 2.2.8, according to the coordinate Q (x ″) of the front wheel of the vehicle 1 ,y″ 1 ) Obtaining the coordinates of the rear wheel as (x ″) 1 -(a+b)cosα′ 0 ,y″ 1 -(a+b)sinα′ 0 )；
2.2.9, assuming that the front wheels move according to the track curve of the bending stage in the time period after the automobile parameters of the bending stage are obtained, obtaining a rear wheel predicted track curve according to the track curve of the front wheels in the bending stage, and accordingly predicting the dangerous area in the bending stage;
step 2.3, dangerous area prediction in the stable stage:
step 2.3.1, obtaining the automobile parameters in the stable stage, including: instantaneous speed u of automobile 2 Yaw angular velocity ω r2 The wheel base a of the front wheel of the automobile, the wheel base b of the rear wheel of the automobile, the distance d between the mass center of the automobile and the central line of the front wheel and the rear wheel, and the corner alpha' of the front wheel 2 ；
The turning radius r' of the front wheel at the stable stage is obtained by the formula (18) 1 And the turning radius r' of the rear wheel in the stabilization phase 2 And according to the turning radius r' of the rear wheel in the stable stage 2 Obtaining the rear wheel of the automobileA travel track of coordinates;
in the formula (18), v 2 At a vertical vehicle speed u 2 Speed of direction, alpha ″) 1 The rear wheel side deflection angle in the stabilization stage;
step 2.3.2, assuming that the front wheels move according to the track curve of the stable stage in the time period after the automobile parameters of the stable stage are obtained, and then according to the turning radius r' of the rear wheels 2 Obtaining a rear wheel predicted track curve so as to realize the prediction of a dangerous area in a stable stage;
step 2.4, predicting the dangerous area in the correction stage:
step 2.4.1, obtaining automobile parameters in the aligning stage, including: instantaneous speed u of a motor vehicle 3 Yaw angular velocity ω r3 A vehicle front wheel wheelbase a, a vehicle rear wheel wheelbase b, a vehicle center of mass distance d from a front wheel centerline and a front wheel corner α ″. 2 ；
The turning radius r 'of the front wheel in the return stage is obtained by the formula (19)' 1 And a turning radius r 'of the rear wheel in the return stage' 2 And according to the turning radius r 'of the rear wheel in the return phase' 2 Obtaining a running track of the coordinates of the rear wheel of the automobile;
in the formula (19), v 3 At a vertical vehicle speed u 3 Speed in direction, α' 1 The rear wheel side deflection angle in the return-to-positive stage;
step 2.4.2, assuming that the front wheels move according to the track curve of the aligning stage in the time period after the automobile parameters of the aligning stage are obtained, according to the turning radius r 'of the rear wheels' 2 And obtaining a rear wheel predicted track curve, thereby realizing the prediction of the return-to-normal stage dangerous area.
Compared with the prior art, the invention has the beneficial effects that:
1. the method can actively predict the dangerous area of the turning of the vehicle in real time, solves the problem of the dangerous area of the turning of the vehicle under most conditions, greatly improves the turning safety of the large vehicle, and is suitable for turning of various large vehicle types and curves at various angles.
2. The method accurately calculates the dangerous area, solves the problem that the dangerous area cannot be accurately described due to the qualitative and fuzzy knowledge of the dangerous area at present, and improves the possibility and the accuracy of the technology applied to reality.
3. The method has wide application, and can accurately predict the dangerous area in real time in any angle curve, at any speed and under different road surface conditions theoretically, thereby greatly improving the applicability and the use value of the method.
4. The method has the function of real-time prediction, solves the problem of active prediction of dangerous areas, greatly improves the practical feasibility of the method, can greatly improve the turning safety of large-scale vehicles, and has initiative and great practical significance.
5. The input parameters of the invention are easy to obtain, can be obtained from the automobile assembly or regulated and controlled according to personal preferences, so that additional equipment is not needed to be added on the automobile, and the invention has the advantages of low cost, easy realization and both accuracy and practicability.
Drawings
FIG. 1 is a simulation diagram of a dangerous area of the present invention, in which, in order to visually recognize the dangerous areas at stages I and III, the specific gravities of the areas I and III are increased in the whole turning process, and the hatched lines indicate the inner wheel difference area between the front and rear wheels;
FIG. 2 is an analysis diagram of the instantaneous state of the automobile according to the present invention, wherein x is the distance between the speed of the automobile and the center line of the front and rear wheels of the automobile; the speed direction of the front wheel of the automobile is not parallel to the front wheel of the automobile, and a slip angle is needed, and the slip angle is small and not obvious in the figure;
fig. 3 is a schematic diagram of the positions of the front and rear wheels of the automobile at the bending stage.
Detailed Description
In the embodiment, the method for predicting the dangerous area with the difference of the turning inner wheels of the large-scale vehicle is divided into 2 aspects of model establishment and model application, and is carried out according to the following steps:
step 1, establishing a dangerous area theoretical model of the wheel difference in turning of the large vehicle:
referring to fig. 1, the invention divides the turning of the large vehicle into 3 stages, i is a bending-in stage, and during the bending-in stage, a driver adjusts a steering wheel to adjust a proper front wheel turning angle to turn a curve. And II, a stable stage, wherein the steering wheel angle of the driver does not change greatly and is in a stage that the front wheel steering angle is relatively stable. And III is a returning stage, which refers to a process that a driver returns to a positive steering wheel to re-align the vehicle body and return the front wheel steering angle.
Step 1.1, dividing a vehicle turning process into three stages, including a bending stage, a stabilizing stage and a correcting stage;
the bending stage is as follows: rate of change of front wheel steering angle
Constant and positive, constant vehicle speed u, yaw rate omega r Constant;
the stabilization phase is as follows: front wheel corner alpha 2 Constant, constant vehicle speed u, yaw angular velocity ω r Constant;
the aligning stage is as follows: rate of change of front wheel steering angle
Constant and negative, constant vehicle speed u, yaw rate omega r Constant;
step 1.2, building a theoretical model of the dangerous area in the bending stage and calculating the dangerous area in the bending stage:
in the bending-in phase, the core model of the invention has the following assumptions:
1. the turning speed u of the vehicle is constant in the stage (the uniform turning conforms to the principle of general driving);
2. this is achievedFront wheel angle rate of change of in-phase vehicle turn
Constant (smooth turns are the driver's turning habits);
3. the road surface turning radius r is known (natural condition of the road surface);
4. the instantaneous yaw rate omega of the vehicle in this stage r Constant (too large a change in angular velocity causes discomfort to the occupants of the vehicle and does not conform to the behavioral habits of the driver).
Thus, in the bending-in phase, the trajectory of the front wheels is studied: the change rate of the turning angle of the front wheel is constant, because the change of the angle is not large in the bending stage, tan alpha 2 Is also substantially constant or slightly greater than alpha 2 Accuracy and safety are guaranteed, so that the front wheel trajectory is obtained by the invention using a quadratic curve y = Ax through the origin of coordinates 2 And (6) simulating. The process of turning a vehicle into a curve is essentially a process of adjusting the instantaneous turning radius ρ of the front wheels of the vehicle to coincide with the fixed turning radius r on the road by the operation of the driver. As can be seen from FIG. 1, the secondary curve is tangent to the road surface specified turning radius circle at the point M (x) 0 ,y 0 ) The center of the circle defined by the road surface is on the y-axis.
Step 1.2.1, obtaining the instantaneous turning radius rho of the automobile by using the geometrical relation of the figure 2 and the formula (1):
in the formula (1), the instantaneous turning radius rho of the front wheel of the automobile, a is the wheel base of the front wheel of the automobile, b is the wheel base of the rear wheel of the automobile, and alpha 1 Is a rear wheel side slip angle, α 2 Is a front wheel corner;
from the correlation velocity and its geometrical relationship of fig. 2, equations (2) and (3) can be derived:
tanα 2 ＝(v+ω r a)-(u-ω r d) (2)
tanα 1 ＝(v-ω r b)/(u-ω r d) (3)
in the formulas (2) and (3), v is the speed perpendicular to the direction of the vehicle speed u, and d is the length between the center of mass of the vehicle and a connecting line between the centers of the front wheel and the rear wheel;
step 1.2.2, obtaining the instantaneous speed of the front wheel according to the front wheel and the mass center associated speed in the figure 2, and calculating the average value to obtain the average speed u of the front wheel of the automobile in the bending stage L ：
In the formula (4), alpha is the instantaneous turning angle of the front wheel of the automobile;
step 1.2.3, obtaining the front wheel steering angle alpha by using the formula (5) 2 From initial zero degree to alpha 2max Time t:
in the formula (5), α 2max The maximum rotation angle of the front wheel and the maximum radius rho according to the instantaneous rotation of the automobile max Is equal to the turning radius r of the road surface;
step 1.2.4, obtaining the running distance s of the front wheel of the automobile within the time t by using the formula (6):
s＝u L t (6)
step 1.2.5, as shown in fig. 3, establishing a turning model coordinate system o-xy by taking the position of a front wheel when a vehicle turns into a curve as an origin o, taking the instantaneous speed direction of the front wheel turning into the curve as an x axis and taking the instantaneous speed direction vertical to the turning into the curve of the front wheel as a y axis; and the maximum included angle alpha between the central axis of the mass center and the x axis of the automobile in the bending stage is obtained by using the formula (7) 0max And as can be seen from fig. 3:
from this stage the instantaneous yaw rate omega of the vehicle r Constant, one can obtain:
α 0max ＝tω r (7)
step 1.2.6, as shown in FIG. 3, obtaining the maximum included angle beta between the front wheel track of the automobile and the x axis by using the formula (8) max ：
β max ＝α 0max +α 2max (8)
Step 1.2.7, establishing an equation set shown in the formula (9) by simultaneously establishing a road surface turning circle equation, a front wheel track equation, an end point tangent equation and an end point curvature equation, and obtaining an end point seat M of the front wheel track in the bending stage 1 (x 1 ,y 1 ) Distance c between the center of the road surface circle and the x-axis 1 And front wheel track curve parameter A 1 ：
Step 1.2.8, setting the coordinates of the front wheel of the automobile in the bending stage as (x) 1 ',y 1 ')；
The car is located at (x) in the bending stage 1 ',y 1 ') angle alpha between the central axis of the center of mass and the x-axis 0 (in this case, only the equation of the curve and the point (x) are known 1 ',y 1 ') and curve end point coordinates M 1 (x 1 ,y 1 ))：
Since alpha is known 2max Is also known
Ramp, thus, there are:
due to alpha 0 And alpha 2 Varying simultaneously during the in-bending phase, and alpha is known 0max Thus, there are:
step 1.2.9, then position according to FIG. 3In relation, the coordinates of the rear wheel of the automobile in the bending stage are (x) 1 '-(a+b)cosα 0 ,y 1 '-(a+b)sinα 0 ) And is used as a theoretical model of the dangerous area in the bending stage; taking a running track of coordinates of a rear wheel of the automobile in the bending stage as a dangerous area of the automobile in the bending stage; belt-in (10), equation (11), and, in summary, it can be calculated that, in the danger zone of the bend-in phase: as shown in stage I of FIG. 1;
step 1.3, establishing a dangerous area theoretical model in a stable stage and calculating a dangerous area in the stable stage:
in the stabilization phase, it is assumed that:
1. with relatively constant front-wheel angle alpha 2max (there is no large change in the steering wheel);
2. a constant vehicle speed u (uniform turning);
3. with stable yaw rate omega r (smooth turning);
4. radius of road surface r is known (road surface condition)
Thus, the front wheel in the stable stage can be obtained as r 1 Make uniform circular motion with radius, the rear wheel takes r 2 The radius of the wheel is uniform circular motion, and the circle centers of the running tracks of the front wheel and the rear wheel are the same.
Obtaining the turning radius r of the front wheel in the stable stage by using the formula (12) 1 And the turning radius r of the rear wheel in the stationary phase 2 And according to the turning radius r of the rear wheel in the stable stage 2 Obtaining a running track of the coordinates of the rear wheels of the automobile and using the running track as a dangerous area theoretical model in a stable stage, and using the running track of the coordinates of the rear wheels of the automobile in the stable stage as a dangerous area in a bending stage of the automobile; and, from this, it is possible to obtain, in the stabilization phase, a dangerous area of the vehicle: as shown in FIG. 1 II, it is known that the turn that the algorithm dwells at this stage is not fixed, so the algorithm can turn for different angles of the vehicle.
Step 1.4, establishing a return-to-normal stage dangerous area theoretical model and calculating a dangerous area in a return-to-normal stage:
in the return phase, assume that:
1. the turning speed u of the vehicle is constant (uniform turning) in this stage;
2. rate of change of front wheel angle of vehicle turning in this phase
Constant (smooth turns);
3. the road surface turning radius r is known (natural condition of the road surface);
4. the instantaneous yaw rate omega of the vehicle in this stage r Constancy (discomfort to persons in the vehicle due to excessive angular velocity variation)
Similar to the cornering phase, the essence of the return phase is the process of increasing the instantaneous turning radius ρ of the front wheels of the vehicle from the road radius r to infinity, adjusted by the driver.
At this time, the positions of the rear wheels and the positions of the front wheels are shifted by a phase difference due to the length of the vehicle as shown in fig. 1 iii, and the front wheel turning angle α is obtained at the moment when the vehicle turns out of a curve 2 =0 rear wheel side slip angle α 1 =0, the trajectory equation for the front wheel uses a quadratic curve y = a for this algorithm, since the angle of rotation is small at this stage 2 x 2 And (4) simulating.
Step 1.4.1, establishing a turning model coordinate system o '-x' y 'by taking the position of a front wheel when a vehicle bends as an origin o', taking the bending instantaneous speed direction of the front wheel as an x 'axis and taking the bending instantaneous speed direction vertical to the front wheel as a y' axis;
the same way as the bending stage, an equation set shown in the formula (13) is established, and the coordinates M of the initial point of the front wheel track in the return stage are obtained 2 (x 2 ,y 2 ) Distance c between the center of the road surface circle and the x' axis 2 And front wheel track curve parameter A 2 ：
Step 1.4.2, set into the front wheel of returning to the front section carThe coordinate is (x' 2 ,y′ 2 ) And in the same manner as in the bending-in stage, the coordinates of the rear wheel of the automobile in the return stage are (x' 2 +(a+b)cosα 0 ,y′ 2 +(a+b)sinα 0 ) And is used as a dangerous area theoretical model of the correcting stage; taking the running track of the coordinates of the rear wheels of the automobile in the aligning stage as a dangerous area of the automobile in the bending stage;
in summary, the danger zone in the correction phase can be calculated: as shown in stage III of FIG. 1;
as can be seen from fig. 1, in the return phase, the danger zone decreases rapidly and even a reverse danger zone occurs, so that in the system design, the danger zones are mainly in the bending-in phase and the stable phase.
By integrating the three dangerous areas, the calculated dangerous area is shown in figure 1;
step 2, judging the turning stage according to the change value of the front wheel steering angle and the change rate of the front wheel steering angle:
step 2.1, when Δ α 2 ＞k 1 Is greater than 0 and
when the automobile enters the bending stage, the automobile enters the bending stage;
when the temperature is higher than the set temperature
And-k 3 ＜Δα 2 ＜k 3 When, it means the vehicle enters a stable phase;
when in use
And Δ α 2 ＜k 5 If the value is less than 0, the automobile enters a stable stage; wherein, k 1 ，k 2 ，k 3 ，k 4 ，k 5 For adjustable sensitivity parameters, Δ α 2 Is the variation of the front wheel corner;
step 2.2, predicting the dangerous area in the bending stage:
step 2.2.1, obtaining automobile parameters in a bending stage, including: automobile instantTime velocity u 1 Yaw angular velocity ω r1 The wheelbase a of the front wheel of the automobile, the wheelbase b of the rear wheel of the automobile, the distance d between the center of mass of the automobile and the center line of the front wheel and the center line of the rear wheel, and the corner alpha of the front wheel' 2 Rate of change of instantaneous turning angle of front wheel of automobile
Step 2.2.2, obtaining the simulation time t' of the automobile in the curve by using the formula (14):
step 2.2.3, obtaining an included angle alpha between the central axis of the mass center and the x axis of the automobile in the bending stage by using the formula (15) 0 ′：
α′ 0 ＝ω r1 t′ (15)
Step 2.2.4, obtaining an included angle beta' between the track of the front wheel of the automobile and the x axis according to the formula (16):
β′＝α′ 0 +α′ 2 (16)
step 2.2.5, obtaining the average speed u 'of the front wheel of the automobile in the bending stage according to the formula (17)' L ；
In the formula (17), α is a segment [0, α' 2 ]An integration section of (1);
step 2.2.6, obtaining the distance s 'of the front wheel of the automobile under the simulation time t' according to the formula (18):
s′＝u′ L t′ (18)
step 2.2.7, setting the coordinate of the front wheel of the vehicle in a turning model coordinate system o ' -x ' y ' as Q (x ″) 1 ,y″ 1 ) (ii) a And establishing an equation set shown in the formula (17) to obtain a front wheel track curve parameter A 1 ', to obtain the trajectory profile of the front wheel during the approach bending stage:
in formula (17), x' is the interval [0,x 2 ]An integration section of (1);
step 2.2.8, according to the coordinate Q (x ″) of the front wheel of the vehicle 1 ,y″ 1 ) Obtaining the coordinates of the rear wheel as (x ″) 1 -(a+b)cosα 0 ′,y″ 1 -(a+b)sinα′ 0 )；
2.2.9, assuming that the front wheels move according to the track curve of the bending stage in the time period after the automobile parameters of the bending stage are obtained, obtaining a rear wheel predicted track curve according to the track curve of the front wheels in the bending stage, and accordingly predicting the dangerous area in the bending stage;
step 2.3, prediction of dangerous areas in a stable stage:
step 2.3.1, obtaining the automobile parameters in a stable stage, comprising: instantaneous speed u of a motor vehicle 2 Yaw angular velocity ω r2 The wheel base a of the front wheel of the automobile, the wheel base b of the rear wheel of the automobile, the distance d between the center of mass of the automobile and the center line of the front wheel and the center line of the rear wheel of the automobile, and the corner alpha' of the front wheel 2 ；
The turning radius r' of the front wheel at the stable stage is obtained by the formula (20) 1 And the turning radius r' of the rear wheel in the stabilization phase 2 And according to the turning radius r' of the rear wheel in the stable stage 2 Obtaining a driving track of the coordinates of the rear wheel of the automobile;
in the formula (20), v 2 At a vertical vehicle speed u 2 Speed of direction, α ″) 1 The rear wheel side deflection angle in the stabilization stage;
step 2.3.2, assuming that the front wheels move according to the track curve of the stable stage in the time period after the automobile parameters of the stable stage are obtained, the turning radius r' of the rear wheels is used 2 Obtaining a rear wheel predicted track curve so as to realize the prediction of a dangerous area in a stable stage;
step 2.4, forecasting the dangerous area in the correction stage:
since the dangerous area in the stage is small and even an inverse dangerous area appears, the stage adopts a stable stage model to simulate the dangerous area in the stage in order to simplify the algorithm, and in order to ensure safety and avoid ambiguity, as proposed in the preceding model establishment.
Step 2.4.1, obtaining automobile parameters in a correction stage, including: instantaneous speed u of a motor vehicle 3 Yaw angular velocity ω r3 A vehicle front wheel wheelbase a, a vehicle rear wheel wheelbase b, a vehicle center of mass distance d from a front wheel centerline and a front wheel corner α ″. 2 ；
The turning radius r 'of the front wheel in the return stage is obtained by the formula (19)' 1 And a turning radius r 'of the rear wheel in the return stage' 2 And according to the turning radius r 'of the rear wheel in the return phase' 2 Obtaining a driving track of the coordinates of the rear wheel of the automobile;
in the formula (21), v 3 At a vertical vehicle speed u 3 Speed of direction, α' 1 The rear wheel side deflection angle in the return-to-positive stage;
step 2.4.2, assuming that the front wheels move according to the track curve of the positive returning phase in the time period after the automobile parameters of the positive returning phase are obtained, the turning radius r 'of the rear wheels is determined' 2 And obtaining a rear wheel predicted track curve, thereby realizing the prediction of the return-to-normal stage dangerous area.
Claims (1)
1. A method for predicting a dangerous area with poor turning inner wheel of a large vehicle is characterized by comprising the following steps:
step 1, establishing a dangerous area theoretical model of the wheel difference in turning of the large vehicle:
1.1, dividing a vehicle turning process into three stages, including a bending stage, a stabilizing stage and a correcting stage;
the bending stage is as follows: rate of change of front wheel steering angle
Constant and positive, constant vehicle speed u, yaw rate omega r Constant;
the stabilization phase is as follows: front wheel corner alpha 2 Constant, constant vehicle speed u, yaw angular velocity omega r Constant;
the correcting stage is as follows: rate of change of front wheel steering angle
Constant and negative, constant vehicle speed u, yaw rate omega r Constant;
step 1.2, establishing a theoretical model of the dangerous area in the bending stage and calculating the dangerous area in the bending stage:
step 1.2.1, obtaining the instantaneous turning radius rho of the automobile by using the formula (1):
in the formula (1), a is the wheel base of the front wheel of the automobile, b is the wheel base of the rear wheel of the automobile, and alpha 1 Is a rear wheel side slip angle, α 2 Is the corner of the front wheel; and has the following components:
tanα 2 ＝(v+ω r a)/(u-ω r d) (2)
tanα 1 ＝(v-ω r b)/(u-ω r d) (3)
in the formulas (2) and (3), v is the speed perpendicular to the direction of the vehicle speed u, and d is the length between the center of mass of the vehicle and a connecting line between the centers of the front wheel and the rear wheel;
step 1.2.2, obtaining the average speed u of the front wheel of the automobile in the bending stage by using the formula (4) L ：
In the formula (4), alpha is the instantaneous turning angle of the front wheel of the automobile;
and 1.2.3. The front wheel turning angle alpha is obtained by using the formula (5) 2 From initial zero degree to alpha 2max Time t of (c):
in the formula (5), α 2max The maximum rotation angle of the front wheel and the maximum radius rho according to the instantaneous rotation of the automobile max Is equal to the turning radius r of the road surface;
step 1.2.4, obtaining the running distance s of the front wheel of the automobile within the time t by using the formula (6):
s＝u L t (6)
step 1.2.5, establishing a turning model coordinate system o-xy by taking the position of a front wheel when a vehicle turns into a curve as an origin o, taking the instantaneous speed direction of the front wheel turning into the curve as an x axis and taking the instantaneous speed direction vertical to the turning into the curve of the front wheel as a y axis; and the maximum included angle alpha between the central axis of the mass center and the x axis of the automobile in the bending stage is obtained by using the formula (7) 0max ：
α 0max ＝tω r (7)
Step 1.2.6, obtaining the maximum included angle beta between the track of the front wheel of the automobile and the x axis by using the formula (8) max ：
β max ＝α 0max +α 2max (8)
Step 1.2.7, establishing an equation set shown as a formula (9), and obtaining a terminal point seat M of the front wheel track in the bending stage 1 (x 1 ,y 1 ) Distance c between the center of the road surface circle and the x-axis 1 And front wheel track curve parameter A 1 ：
Step 1.2.8, setting the coordinates of the front wheel of the automobile in the bending stage as (x) 1 ',y 1 ') the coordinates of the rear wheel of the car in the bending stage are (x) 1 '-(a+b)cosα 0 ,y 1 '+(a+b)sinα 0 ) And as a bending-in stageA dangerous area theoretical model; taking a running track of coordinates of a rear wheel of the automobile in the bending stage as a dangerous area of the automobile in the bending stage; wherein alpha is 0 The included angle between the central axis of the mass center and the x axis when the automobile is in a bending stage;
step 1.3, establishing a dangerous area theoretical model in a stable stage and calculating a dangerous area in the stable stage:
obtaining the turning radius r of the front wheel in the stable stage by using the formula (10) 1 And the turning radius r of the rear wheel in the stationary phase 2 And according to the turning radius r of the rear wheel in the stable stage 2 Obtaining the running track of the coordinates of the rear wheel of the automobile and using the running track of the coordinates of the rear wheel of the automobile in the stable stage as a dangerous area of the automobile in the bending stage;
step 1.4, establishing a return-to-normal stage dangerous area theoretical model and calculating a dangerous area in a return-to-normal stage:
step 1.4.1, establishing a turning model coordinate system o '-x' y 'by taking the position of a front wheel when a vehicle bends as an origin o', taking the bending-out instantaneous speed direction of the front wheel as an x 'axis and taking the bending-out instantaneous speed direction vertical to the front wheel as a y' axis;
establishing an equation set shown in the formula (11), and obtaining the coordinates M of the starting point of the front wheel track in the return-to-normal stage 2 (x 2 ,y 2 ) Distance c between the center of the road surface circle and the x' axis 2 And front wheel track curve parameter A 2 ：
Step 1.4.2, setting the coordinates of the front wheel of the automobile in the return-to-front section as (x' 2 ,y′ 2 ) Then the coordinates of the rear wheel of the vehicle in the return-to-normal phase are (x' 2 +(a+b)cosα 0 ,y′ 2 +(a+b)sinα 0 ) And makeA dangerous area theoretical model in a correcting stage; taking the running track of the coordinates of the rear wheels of the automobile in the aligning stage as a dangerous area of the automobile in the bending stage;
step 2, judging the turning stage according to the change value of the front wheel steering angle and the change rate of the front wheel steering angle:
step 2.1, when Δ α 2 ＞k 1 Is greater than 0 and
when the automobile enters the bending stage, the automobile enters the bending stage;
when in use
And-k 3 ＜Δα 2 ＜k 3 When, it means the vehicle enters a stable phase;
when in use
And Δ α 2 ＜k 5 If the value is less than 0, the automobile enters a stable stage; wherein, k 1 ，k 2 ，k 3 ，k 4 ，k 5 For adjustable sensitivity parameters, Δ α 2 Is the variation of the front wheel corner;
step 2.2, predicting the dangerous area in the bending stage:
step 2.2.1, obtaining automobile parameters in the bending stage, including: instantaneous speed u of a motor vehicle 1 Yaw angular velocity ω r1 The wheel base a of the front wheel of the automobile, the wheel base b of the rear wheel of the automobile, the distance d between the mass center of the automobile and the central line of the front wheel and the rear wheel, and the corner alpha of the front wheel 2 ', rate of change of instantaneous turning angle of front wheel of automobile
Step 2.2.2, obtaining the simulation time t' of the bending of the automobile by using the formula (12):
step 2.2.3, obtaining an included angle alpha between a center axis of a mass center and an x axis of the automobile in a bending stage by using the formula (13) 0 ′：
α′ 0 ＝ω r1 t′ (13)
Step 2.2.4, obtaining an included angle beta' between the track of the front wheel of the automobile and the x axis according to the formula (14):
β′＝α′ 0 +α′ 2 (14)
step 2.2.5, obtaining the average speed u 'of the front wheel of the automobile in the bending stage according to the formula (16)' L ；
In the formula (15), α is a segment [0, α' 2 ]An integration section of (1);
step 2.2.6, obtaining the distance s 'of the front wheel of the automobile under the simulation time t' according to the formula (16):
s′＝u′ L t′ (16)
step 2.2.7, setting the coordinates of the front wheels of the vehicle in the turning model coordinate system o ' -x ' y ' as Q (x ″) 1 ,y″ 1 ) (ii) a And establishing an equation set shown as the formula (17) to obtain a front wheel track curve parameter A 1 ', to obtain the trajectory profile of the front wheel during the approach bending stage:
in formula (17), x' is the interval [0,x 2 ]The integration section of (2);
step 2.2.8, according to the coordinate Q (x ″) of the front wheel of the vehicle 1 ,y″ 1 ) Obtaining the coordinates of the rear wheel as (x ″) 1 -(a+b)cosα′ 0 ,y″ 1 -(a+b)sinα′ 0 )；
2.2.9, assuming that the front wheels move according to the track curve of the bending stage in the time period after the automobile parameters of the bending stage are obtained, obtaining a rear wheel predicted track curve according to the track curve of the front wheels in the bending stage, and accordingly predicting the dangerous area in the bending stage;
step 2.3, dangerous area prediction in the stable stage:
step 2.3.1, obtaining automobile parameters in the stable stage, including: instantaneous speed u of automobile 2 Yaw angular velocity ω r2 The wheel base a of the front wheel of the automobile, the wheel base b of the rear wheel of the automobile, the distance d between the mass center of the automobile and the central line of the front wheel and the rear wheel, and the corner alpha' of the front wheel 2 ；
The turning radius r' of the front wheel at the stable stage is obtained by the formula (18) 1 And the turning radius r' of the rear wheel in the stabilization phase 2 And according to the turning radius r' of the rear wheel in the stable stage 2 Obtaining a running track of the coordinates of the rear wheel of the automobile;
in the formula (18), v 2 At a vertical vehicle speed u 2 Speed of direction, alpha ″) 1 The rear wheel side deflection angle in the stabilization stage;
step 2.3.2, assuming that the front wheels move according to the track curve of the stable stage in the time period after the automobile parameters of the stable stage are obtained, and then according to the turning radius r' of the rear wheels 2 Obtaining a rear wheel predicted track curve so as to realize the prediction of a dangerous area in a stable stage;
step 2.4, forecasting the dangerous area in the correction stage:
step 2.4.1, obtaining the automobile parameters in the correcting stage, including: instantaneous speed u of a motor vehicle 3 Yaw angular velocity ω r3 A wheel base a of a front wheel of the vehicle, a wheel base b of a rear wheel of the vehicle, a distance d of a centroid of the vehicle from a centerline of the front wheel and the rear wheel, and a front wheel rotation angle α' 2 ；
The turning radius r 'of the front wheel in the return stage is obtained by the formula (19)' 1 And a turning radius r 'of the rear wheel in the return stage' 2 And according to the turning radius r 'of the rear wheel in the return stage' 2 Obtaining a running track of the coordinates of the rear wheel of the automobile;
in the formula (19), v 3 At a vertical vehicle speed u 3 Speed of direction, α' 1 The rear wheel side deflection angle in the return-to-positive stage;
step 2.4.2, assuming that the front wheels move according to the track curve of the return-to-positive stage in the time period after the automobile parameters of the return-to-positive stage are obtained, according to the turning radius r 'of the rear wheels' 2 And obtaining a rear wheel predicted track curve, thereby realizing the prediction of the return-to-normal stage dangerous area.
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