CN112660112B - Vehicle side-tipping state and side-tipping prediction method and system - Google Patents
Vehicle side-tipping state and side-tipping prediction method and system Download PDFInfo
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Abstract
The invention relates to a method and a system for predicting a vehicle roll state and rollover. According to the vehicle roll state and rollover prediction method and system, the 1/4 suspension model and the roll dynamics model are adopted to respectively determine the lateral load transfer rate, so that not only can the current vehicle roll state be judged, but also the vehicle rollover trend can be predicted. In the practical application process, the suspension height value can be measured by adopting a vehicle height sensor (a suspension displacement sensor), and the 1/4 suspension model is utilized to estimate the vertical load of the vehicle tire, so that the estimation precision of the vertical load of the tire is obviously improved, the calculated lateral load transfer rate value is more accurate, and the vehicle roll state can be accurately judged and the vehicle roll tendency can be accurately predicted.
Description
Technical Field
The invention relates to the technical field of vehicle rollover detection, in particular to a method and a system for predicting a vehicle roll state and rollover.
Background
In the prior art, the methods for predicting the roll state and the rollover of the vehicle mainly comprise the following steps:
(1) determining based on the roll angle and the lateral acceleration threshold:
patent document CN104296722A first acquires lateral acceleration and vertical acceleration of a vehicle, then obtains a vehicle roll angle and lateral acceleration of the vehicle relative to a geodetic coordinate system, and compares and determines the obtained vehicle roll angle with a set roll range to obtain a vehicle roll state.
Patent documents CN1576068A disclose sensors 1, 2, and 3 for detecting lateral acceleration, vertical acceleration, and roll angular velocity of a vehicle; a device for calculating the vehicle roll angle by integrating the roll angle speed; means for correcting a zero point of a rollover angle of the vehicle using the lateral acceleration and the roll angular velocity; a device for judging the side-turning form according to the composite acceleration of the lateral acceleration and the vertical acceleration; a map for determining a rollover determination threshold value of the vehicle according to the rollover form; a device for determining the degree of rollover according to the combined acceleration of the lateral acceleration and the vertical acceleration; and a threshold value device for correcting the rollover judging threshold value map according to the occurrence degree.
Patent document CN110371068A discloses a vehicle rollover warning system. It is composed of information acquisition portion, CPU portion and man-machine interaction portion. The human-computer interaction part comprises a display module and an alarm module. The information acquisition module transmits the acquired vehicle speed information, steering angle information and roll angle information to the CPU module in a wired mode, and the CPU calculates the balance state of the vehicle at the moment, displays the balance state through the display module and judges whether to give an alarm or not.
(2) A method based on a side-tipping phase plane:
patent document CN101336183A determines the roll risk of the vehicle state by establishing a roll angle velocity and roll angle phase plane and calculating the distances from the roll stability boundary line to the roll angle and roll angle velocity coordinate axes.
Patent document CN108680364A discloses an automobile rollover evaluation index and an evaluation method. And converting the roll angle, the roll angle acceleration and the lateral acceleration measured in real time in the running process of the automobile into a roll angle and roll angle acceleration phase diagram, a roll angle and lateral acceleration phase diagram and a lateral acceleration and roll angle acceleration phase diagram, and comparing the phase diagrams with the corresponding rollover threshold conditions to judge whether the automobile has rollover risks.
(3) Based on the side load transfer rate:
patent document CN108099919A provides a vehicle rollover prevention warning method and device, a storage medium, and a vehicle. The vehicle rollover prevention early warning method comprises the following steps: collecting the roll state parameters of the vehicle body, calculating the lateral axle load transfer rate of the vehicle according to the collected vehicle state parameters and the roll load transfer model, and judging whether the vehicle has the risk of rollover according to the calculated lateral load transfer rate and a preset threshold value.
Patent document CN111391595A discloses a vehicle rollover prevention active tilt model prediction control method, which establishes a lateral load transfer expression capable of fully expressing rollover transient characteristics, and establishes an expected tilt angle of active tilt control and a design model prediction controller; which gives a lateral load transfer expression including a roll angle acceleration, and thus can more accurately evaluate the transient characteristics of the vehicle in an emergency.
Patent document CN110239462A discloses a method and a system for warning of vehicle rollover. The method comprises the following steps: acquiring the roll angle speed and the lateral acceleration of the vehicle body acquired by the smart phone; estimating the roll angle speed and the roll angle by adopting a Kalman filtering state observer to obtain a roll angle speed estimation value and a roll angle estimation value; correcting the lateral acceleration according to the lateral inclination angle and the installation vertical deviation to obtain a lateral acceleration correction value; calculating the vertical load transfer rate of the vehicle according to the estimated value of the roll angle, the estimated value of the roll angle speed and the corrected value of the lateral acceleration; and triggering an alarm action corresponding to the grade according to the grade of the vertical load transfer rate of the vehicle.
Patent document CN110626353A discloses a vehicle dangerous state early warning method based on a roll risk indicator, which provides a roll risk indicator for calculating a ratio between a difference of vertical loads of vehicle tires and a sum of vertical loads; establishing a vehicle state parameter error identification model related to the change of the vehicle roll height, the roll center moment of inertia, the equivalent roll stiffness of the suspension and the equivalent damping coefficient of the suspension; calculating real-time roll height, roll center moment of inertia, suspension equivalent roll stiffness and suspension equivalent damping coefficient change through a minimum recursion quadratic multiple algorithm; establishing an improved roll index model based on real-time correction of roll height; and establishing vehicle roll risk early warning based on a reasonable RI threshold.
Patent document CN108909704A discloses a vehicle rollover prevention control method based on internet of vehicles, which includes the following steps: A. performing attitude integration on the yaw angular velocity, the roll angular velocity and the pitch angular velocity of the vehicle during the running of the vehicle to obtain a real-time roll angle; B. acquiring a real-time roll angle, and performing data fusion processing on the signal by adopting a Kalman filter to obtain a real-time optimal value of the vehicle roll angle; C. calculating a rollover judging characteristic value by using lateral acceleration and a roll angle through a lateral load transfer rate LTR calculation formula after obtaining an optimal vehicle attitude value; D. and then, judging whether the rollover danger exists or not, if not, predicting the rollover judging characteristic value for 1 to 2 seconds by a multi-layer hierarchical modeling prediction method to obtain a predicted value of the rollover judging characteristic value for 1 to 2 seconds, and further judging whether the rollover danger exists in the future or not.
Patent document CN107195025A discloses a vehicle rollover index prediction method based on-line estimation of the height of the center of gravity. Establishing a vehicle roll dynamic model according to a basic dynamic theory; then, obtaining a parameter identification model related to the height of the gravity center by using an adaptive filtering theory, wherein the parameter identification model only needs lateral acceleration and opposite-side tilt angle sensor signals as input; aiming at the parameter identification model, a self-adaptive rate driven by parameter error information is provided by designing a filter matrix, and the online real-time self-adaptive estimation of the gravity center height is realized; and finally, obtaining a rollover index prediction method based on gravity height online estimation according to a basic formula of the lateral load transfer rate.
(4) An energy-based method:
patent document CN101025387A relates to a system and method for providing a vehicle roll stability indicator that estimates the likelihood of a vehicle rollover. The system determines kinematic parameters of the vehicle by means of vehicle sensors, from which it estimates the roll angle and the bank angle of the vehicle; based on the estimated bank angle, the system provides a corrected roll angle; based on the corrected roll angle, the system determines a roll energy and a roll energy rate of the vehicle; based on the roll energy and roll energy rate, the system calculates a roll stability indicator.
Based on the above technical solutions disclosed in the prior art, the above solutions mainly have the following disadvantages:
in the scheme (1), although the vehicle rollover judgment can be directly carried out through the state parameters of the vehicle, the selection of the rollover threshold value needs to depend on a large amount of off-line simulation and real vehicle tests, and the rollover trend of the vehicle cannot be predicted.
The determination of the lateral phase plane of the solution (2) also needs to rely on a large number of off-line simulations and real-vehicle tests. And the rollover tendency of the vehicle cannot be predicted.
The scheme (3) can only estimate the current roll state of the vehicle, and cannot warn the rollover trend of the vehicle.
The scheme (4) is based on an energy method, the roll energy and the roll energy rate of the vehicle are calculated through state parameters such as the height of the center of mass of the vehicle, the roll angle of the vehicle and the like, only the current roll state of the vehicle can be estimated, and the rollover trend of the vehicle cannot be pre-warned.
Therefore, the method or the system for accurately judging the vehicle roll state and accurately predicting the vehicle rollover trend is a technical problem to be solved urgently in the field.
Disclosure of Invention
The invention aims to provide a vehicle roll state and rollover prediction method and system, which can accurately judge the vehicle roll state and accurately predict the vehicle rollover trend.
In order to achieve the purpose, the invention provides the following scheme:
a vehicle roll state and rollover prediction method includes:
acquiring 1/4 suspension models of the vehicle and roll dynamics models of the vehicle;
determining the vertical load of the vehicle tyre according to the 1/4 suspension model;
determining a first lateral load transfer rate in the current control period of the vehicle according to the vertical load;
acquiring a first preset transfer rate threshold;
judging whether the lateral load transfer rate is smaller than a first preset transfer rate threshold value or not to obtain a first judgment result;
if the first judgment result is less than the first judgment result, returning to the step of determining the vertical load of the vehicle tire according to the 1/4 suspension model so as to determine the vertical load of the vehicle tire in the next control cycle;
if the first judgment result is greater than or equal to the first judgment result, determining a second lateral load transfer rate in the current control period of the vehicle according to the roll dynamic model of the vehicle;
acquiring a second preset transfer rate threshold;
judging whether the second lateral load transfer rate is smaller than or equal to a second preset transfer rate threshold value or not to obtain a second judgment result;
if the second judgment result is less than or equal to the second judgment result, acquiring a lateral acceleration and rollover prediction model, and determining the rollover time of the vehicle according to the lateral acceleration and the rollover prediction model;
acquiring a preset time threshold, and judging whether the vehicle rollover time is greater than or equal to the preset time threshold to obtain a third judgment result;
if the third judgment result is greater than or equal to the third judgment result, returning to the step of determining the vertical load of the vehicle tire according to the 1/4 suspension model so as to determine the vertical load of the vehicle tire in the next control cycle;
if the third judgment result is less than the second preset transfer rate threshold, returning to the step of judging whether the second lateral load transfer rate is less than or equal to the second preset transfer rate threshold;
and if the second judgment result is greater than the first judgment result, sending a rollover alarm.
Preferably, the 1/4 suspension model is:
wherein Δ z is the vertical relative displacement between the sprung and unsprung masses,
is the acceleration of the sprung mass,
is the vertical relative velocity between sprung and unsprung massesDegree, msIs sprung mass, ksAs stiffness of the suspension, csFor damping of the suspension, i e [ L1, R1, L2, R2]L1 represents the left front wheel, R1 represents the right front wheel, L2 represents the left rear wheel, and R2 represents the right rear wheel.
Preferably, the roll dynamics model of the vehicle is:
in the formula (I), the compound is shown in the specification,
in order to set the roll angle of the vehicle,
in order to accelerate the roll angle of the vehicle,
is the vehicle roll angle velocity, msIs a sprung mass, ayAs lateral acceleration of the vehicle, hrcDistance of centre of mass to centre of roll on spring, IxIs the moment of inertia of the sprung mass about the x-axis of the vehicle coordinate system, g is the gravitational acceleration,
for the roll stiffness of the suspension system,
damping the roll angle of the suspension system.
Preferably, according to the 1/4 suspension model, a formula is adopted
Determining the vertical load of the vehicle tyre;
in the formula, FzFor vertical load, msIs the sprung mass, g is the gravitational acceleration, Δ z is the vertical relative displacement between the sprung and unsprung masses, muIs the unsprung mass of the spring,
is the vertical relative velocity between sprung and unsprung masses, zoFor the suspension height of the vehicle under static load, ksAs stiffness of the suspension, csFor damping of the suspension, i e [ L1, R1, L2, R2]L1 represents the left front wheel, R1 represents the right front wheel, L2 represents the left rear wheel, and R2 represents the right rear wheel.
Preferably, the determining the vehicle rollover time according to the lateral acceleration and the rollover prediction model specifically includes:
and after the lateral acceleration passes through a Kalman filter and is input into the rollover prediction model, outputting the rollover time of the vehicle.
Corresponding to the vehicle roll state and rollover predicting method, the invention also provides a vehicle roll state and rollover predicting system, which comprises the following specific steps:
a vehicle roll condition and rollover prediction system, comprising:
a model acquisition module for acquiring 1/4 a suspension model of the vehicle and a roll dynamics model of the vehicle;
a vertical load determination module for determining the vertical load of a vehicle tyre from said 1/4 suspension model;
the first lateral load transfer rate determining module is used for determining a first lateral load transfer rate in the current control period of the vehicle according to the vertical load;
the first preset transfer rate threshold acquisition module is used for acquiring a first preset transfer rate threshold;
the first judgment module is used for judging whether the lateral load transfer rate is smaller than the first preset transfer rate threshold value or not to obtain a first judgment result;
a first returning module for returning to the step of "determining the vertical load of the vehicle tire according to the 1/4 suspension model" to determine the vertical load of the vehicle tire in the next control cycle when the first judgment result is less than;
a second lateral load transfer rate determining module, configured to determine, according to the roll dynamics model of the vehicle, a second lateral load transfer rate in a current control cycle of the vehicle when the first determination result is greater than or equal to the first determination result;
the second preset transfer rate threshold acquisition module is used for acquiring a second preset transfer rate threshold;
the second judgment module is used for judging whether the second lateral load transfer rate is smaller than or equal to a second preset transfer rate threshold value or not to obtain a second judgment result;
the vehicle rollover time determining module is used for acquiring a lateral acceleration and a rollover prediction model when the second judgment result is less than or equal to the second judgment result, and determining the vehicle rollover time according to the lateral acceleration and the rollover prediction model;
the third judging module is used for acquiring a preset time threshold value, judging whether the vehicle rollover time is greater than or equal to the preset time threshold value or not, and obtaining a third judging result;
a second returning module, configured to, when the third determination result is greater than or equal to the third determination result, return to the step of determining the vertical load of the vehicle tire according to the 1/4 suspension model, so as to determine the vertical load of the vehicle tire in the next control cycle;
a third returning module, configured to, when the third determination result is less than the second predetermined threshold, return to the step of "determining whether the second lateral load transfer rate is less than or equal to a second predetermined transfer rate threshold";
and the rollover alarm module is used for sending a rollover alarm when the second judgment result is greater than the second judgment result.
Preferably, the vertical load module includes:
a vertical load cell for applying a formula based on said 1/4 suspension model
Determining the vertical load of the vehicle tyre;
in the formula, FzFor vertical load, msIs the sprung mass, g is the gravitational acceleration, Δ z is the vertical relative displacement between the sprung and unsprung masses, muIs the unsprung mass of the spring,
is the vertical relative velocity between sprung and unsprung masses, zoFor the suspension height of the vehicle under static load, ksAs stiffness of the suspension, csFor damping of the suspension, i e [ L1, R1, L2, R2]L1 represents the left front wheel, R1 represents the right front wheel, L2 represents the left rear wheel, and R2 represents the right rear wheel.
Preferably, the vehicle rollover time determining module specifically includes:
and the lateral acceleration passes through the Kalman filter, is input into the rollover prediction model, and then is output to the vehicle rollover time.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
according to the vehicle roll state and rollover prediction method and system provided by the invention, the 1/4 suspension model and the roll dynamics model are adopted to respectively determine the lateral load transfer rate, so that not only can the current vehicle roll state be judged, but also the vehicle rollover trend can be predicted. In the practical application process, the suspension height value can be measured by adopting a vehicle height sensor (a suspension displacement sensor), and the 1/4 suspension model is utilized to estimate the vertical load of the vehicle tire, so that the estimation precision of the vertical load of the tire is obviously improved, the calculated lateral load transfer rate value is more accurate, and the vehicle roll state can be accurately judged and the vehicle roll tendency can be accurately predicted.
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 first flowchart of a method for predicting a roll state and a rollover of a vehicle according to the present invention;
FIG. 2 is a second flowchart of a vehicle roll state and rollover prediction method provided by the present invention;
FIG. 3 is a schematic diagram of a vehicle roll dynamics model provided in an embodiment of the present invention;
FIG. 4 is a schematic view of an 1/4 suspension model provided in an embodiment of the invention;
fig. 5 is a schematic structural diagram of a vehicle roll state and rollover prediction 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 vehicle roll state and rollover prediction method and system, which can accurately judge the vehicle roll state and accurately predict the vehicle rollover trend.
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.
Fig. 1 is a first flowchart of a method for predicting a roll state and a rollover of a vehicle according to the present invention. Fig. 2 is a second flowchart of a vehicle roll state and rollover prediction method provided by the present invention. As shown in fig. 1 and 2, the method for predicting a roll state and a rollover of a vehicle according to the present invention includes:
step 100: an 1/4 suspension model of the vehicle and a roll dynamics model of the vehicle are obtained.
Step 101: the vertical load of the vehicle tires was determined from the 1/4 suspension model.
Step 102: and determining a first lateral load transfer rate in the current control period of the vehicle according to the vertical load.
The lateral load transfer rate utilizes the vertical load change of the left wheel and the right wheel to quantitatively evaluate the rollover trend of the vehicle in real time. Wherein the lateral load transfer rate is defined as LTR:
in the formula: fzFor the vertical load of the tire, superscripts L1, L2, R1, R2 respectively denote the left front wheel, the left rear wheel, the right front wheel and the right rear wheel. LTR varies in the range of [ -1,1 []And-1 means that the right tire is completely off the ground, and 1 means that the left tire is completely off the ground. 0 means that the vertical loads of the left and right wheels are the same, i.e. there is no tendency to roll. The lateral load transfer rate LTR can only reflect the current roll state of the vehicle, and the future rollover trend of the vehicle cannot be predicted.
Step 103: a first preset transfer rate threshold is obtained.
Step 104: and judging whether the lateral load transfer rate is smaller than a first preset transfer rate threshold value or not to obtain a first judgment result.
Step 105: if the first judgment result is less than the first judgment result, the step of determining the vertical load of the vehicle tire according to the 1/4 suspension model is returned to determine the vertical load of the vehicle tire in the next control cycle.
Step 106: and if the first judgment result is greater than or equal to the second judgment result, determining a second lateral load transfer rate in the current control period of the vehicle according to the roll dynamic model of the vehicle.
Step 107: and acquiring a second preset transfer rate threshold value.
Step 108: and judging whether the second lateral load transfer rate is less than or equal to a second preset transfer rate threshold value or not to obtain a second judgment result.
Step 109: and if the second judgment result is less than or equal to the second judgment result, acquiring a lateral acceleration and rollover prediction model, and determining the rollover time of the vehicle according to the lateral acceleration and the rollover prediction model.
Step 110: and acquiring a preset time threshold, and judging whether the vehicle rollover time is greater than or equal to the preset time threshold to obtain a third judgment result.
Step 111: if the third determination result is equal to or greater than the third determination result, the routine returns to the step of determining the vertical load of the vehicle tire from the 1/4 suspension model to determine the vertical load of the vehicle tire in the next control cycle.
Step 112: and if the third judgment result is less than the second preset transfer rate threshold, returning to the step of judging whether the second lateral load transfer rate is less than or equal to the second preset transfer rate threshold.
Step 113: and if the second judgment result is greater than the first judgment result, sending a rollover alarm.
Preferably, the 1/4 suspension model used in the present invention is:
wherein Δ z is the vertical relative displacement between the sprung and unsprung masses,
is the acceleration of the sprung mass,
is the vertical relative velocity between sprung and unsprung masses, msIs sprung mass, ksAs stiffness of the suspension, csFor damping of the suspension, i e [ L1, R1, L2, R2]L1 represents the left front wheel, R1 represents the right front wheel, L2 represents the left rear wheel, and R2 represents the right rear wheel.
The specific construction process of the 1/4 suspension model adopted by the invention comprises the following steps:
as shown in fig. 4, the 1/4 suspension dynamics model can be expressed as:
in the formula: z is a radical ofbAnd zwVertical displacements of the sprung and unsprung masses, respectively. For active suspension systems, the vertical relative displacement between sprung and unsprung masses may be accommodated by the height of the vehicle bodyAnd measuring by a degree sensor. Thus, the above formula can be simplified as:
in the formula: deltaz is the vertical relative displacement between the sprung and unsprung masses,
is the vertical relative velocity between the sprung and unsprung masses,
is the sprung mass acceleration.
Preferably, the roll dynamics model of the vehicle is:
in the formula (I), the compound is shown in the specification,
in order to set the roll angle of the vehicle,
in order to accelerate the roll angle of the vehicle,
is the vehicle roll angle velocity, msIs a sprung mass, ayAs lateral acceleration of the vehicle, hrcDistance of centre of mass to centre of roll on spring, IxIs the moment of inertia of the sprung mass about the x-axis of the vehicle coordinate system, g is the gravitational acceleration,
for the roll stiffness of the suspension system,
damping the roll angle of the suspension system.
The concrete construction process of the roll dynamics model of the vehicle adopted by the invention comprises the following steps:
as shown in FIG. 3, the roll dynamics equation for a vehicle may be expressed as:
in the formula:
in order to set the roll angle of the vehicle,
in order to accelerate the roll angle of the vehicle,
is the vehicle roll angle velocity, msIs a sprung mass, ayAs lateral acceleration of the vehicle, hrcDistance of centre of mass to centre of roll on spring, IxIs the moment of inertia of the sprung mass about the x-axis of the vehicle coordinate system, g is the gravitational acceleration,
for the roll stiffness of the suspension system,
damping the roll angle of the suspension system. Roll stiffness
And lateral angular damping
Can be approximately calculated as:
in the formula: l is a left and right suspension systemThe mounting point spacing of (a). k is a radical ofsAnd csStiffness and damping of the suspension, i e [ L1, R1, L2, R2, respectively]L1, R1, L2 and R2 represent the left front wheel, right front wheel, left rear wheel and right rear wheel, respectively.
The vehicle roll angle is small in the whole operation condition, so that
The roll dynamics equation can be simplified as:
wherein, in fig. 3: CG is the sprung mass centre of mass, L is the track, and L is the left and right side suspension mounting spacing.
Preferably, according to 1/4 suspension model, formula is adopted
The vertical load of the vehicle tires is determined.
In the formula, FzFor vertical load, msIs the sprung mass, g is the gravitational acceleration, Δ z is the vertical relative displacement between the sprung and unsprung masses, muIs the unsprung mass of the spring,
is the vertical relative velocity between sprung and unsprung masses, zoFor the suspension height of the vehicle under static load, ksAs stiffness of the suspension, csFor damping of the suspension, i e [ L1, R1, L2, R2]L1 represents the left front wheel, R1 represents the right front wheel, L2 represents the left rear wheel, and R2 represents the right rear wheel.
Vertical load of tyre
Can be driven by static load
And dynamic load
Two parts are formed. Where the static load is related to the mass of the vehicle itself and the distribution of the center of mass, and the dynamic load is related to the load transfer due to the motion of the vehicle. Thus, the vertical load of a tire can be expressed as:
in the formula:
and
representing the mass of the sprung and unsprung masses, respectively, distributed over each wheel, zoRepresenting the suspension height of the vehicle under static load, zoCan be calculated by the following formula
Based on the content provided by the invention, the whole vehicle rollover prediction process can be simplified as follows:
step 1: in each control cycle, tire vertical loads and LTR values were calculated based on the 1/4 suspension model, based on suspension height.
Step 2: and judging whether the LTR value is larger than a preset threshold value, if so, jumping to the step 3, and if not, jumping back to the step 1.
And step 3: LTR values are calculated based on the roll dynamics model and the predicted time is accumulated to determine whether the LTR value will exceed its threshold value for a limited time in each control cycle. If the LTR value exceeds its threshold within a defined time, a rollover warning is issued.
Based on this simple implementation step, the vehicle rollover tendency can be predicted based on current vehicle state inputs. With roll angular velocity and roll angular acceleration as state variables, expressed as
Thus, the simplified roll dynamics equation can be further expressed as:
using the above formula
Rewritten as a state space expression, there may be
Y＝CX
In the formula: a is a state transition matrix, B is an input matrix, C is an observation matrix, U is system input, and Y is observed quantity. The method comprises the following specific steps:
wherein, U ═ ayTaking the roll angle and the roll angle velocity as observed quantities, the output matrix C can be expressed as
Equation of continuous state
Discretizing to obtain:
and T in the matrix is a system calculation period, the smaller the calculation period is, the higher the accuracy of the prediction model is, and the calculation period is usually set to be 0.01s in consideration of the calculation performance of the controller.
Preferably, the determining the vehicle rollover time according to the lateral acceleration and the rollover prediction model specifically includes:
and after the lateral acceleration passes through the Kalman filter and is input into the rollover prediction model, outputting the rollover time of the vehicle.
Considering that the ideal prediction accuracy is difficult to obtain by simply using the lateral acceleration as the input of the rollover prediction system, the Kalman filtering estimator is introduced to improve the accuracy of the rollover prediction system. The state equation of the kalman filter estimator is:
wherein x is a state variable, A is a state transition matrix, B is an input matrix, y is an observed quantity, and H is an observation matrix.
The optimal kalman filter estimate is:
x(t)＝x(t,t-1)+K(t)(Z(t)-y(t))。
the kalman gain may be calculated as:
the covariance is updated as:
in the above formula, Q and R are process noise and observation noise.
After passing through a Kalman filtering estimator, the accuracy of the rollover prediction system is further improved, and the lateral load transfer rate LTR can be calculated as follows:
LTR(t)＝Gx(t)。
the output matrix G can be expressed as:
and B in the matrix is the track width of the vehicle.
In addition, corresponding to the above-mentioned roll state and rollover predicting method for the vehicle, the present invention further provides a roll state and rollover predicting system for the vehicle, as shown in fig. 5, the roll state and rollover predicting system for the vehicle includes:
a model acquisition module 1 for acquiring 1/4 a suspension model of a vehicle and a roll dynamics model of the vehicle.
And a vertical load determination module 2 for determining the vertical load of the vehicle tyre according to the 1/4 suspension model.
And the first lateral load transfer rate determining module 3 is used for determining a first lateral load transfer rate in the current control period of the vehicle according to the vertical load.
The first preset transfer rate threshold obtaining module 4 is configured to obtain a first preset transfer rate threshold.
And the first judging module 5 is used for judging whether the lateral load transfer rate is smaller than a first preset transfer rate threshold value to obtain a first judging result.
And a first returning module 6 for returning to the step "determining the vertical load of the vehicle tire according to the 1/4 suspension model" to determine the vertical load of the vehicle tire in the next control cycle when the first judgment result is less.
And a second lateral load transfer rate determining module 7, configured to determine a second lateral load transfer rate in the current control cycle of the vehicle according to the roll dynamics model of the vehicle when the first determination result is equal to or greater than the first determination result.
And a second preset transfer rate threshold obtaining module 8, configured to obtain a second preset transfer rate threshold.
And the second judging module 9 is configured to judge whether the second lateral load transfer rate is less than or equal to a second preset transfer rate threshold value, so as to obtain a second judgment result.
And the vehicle rollover time determining module 10 is configured to, when the second determination result is less than or equal to the second determination result, acquire the lateral acceleration and the rollover prediction model, and determine the vehicle rollover time according to the lateral acceleration and the rollover prediction model.
The third judging module 11 is configured to obtain a preset time threshold, and judge whether the vehicle rollover time is greater than or equal to the preset time threshold, so as to obtain a third judgment result.
And a second returning module 12 for returning to the step of determining the vertical load of the vehicle tire according to the 1/4 suspension model to determine the vertical load of the vehicle tire in the next control cycle when the third judgment result is equal to or greater than.
And a third returning module 13, configured to, when the third determination result is less than the second predetermined threshold, return to the step "determine whether the second lateral load transfer rate is less than or equal to the second predetermined transfer rate threshold".
And the rollover alarm module 14 is used for sending a rollover alarm when the second judgment result is greater than the first judgment result.
Preferably, the vertical load module 2 comprises:
a vertical load cell for applying a formula based on the 1/4 suspension model
The vertical load of the vehicle tires is determined.
In the formula, FzFor vertical load, msIs the sprung mass, g is the gravitational acceleration, Δ z is the vertical relative displacement between the sprung and unsprung masses, muIs the unsprung mass of the spring,
is the vertical relative velocity between sprung and unsprung masses, zoFor the suspension height of the vehicle under static load, ksAs stiffness of the suspension, csFor damping of the suspension, i e [ L1, R1, L2, R2]L1 represents the left front wheel, R1 represents the right front wheel, L2 represents the left rear wheel, and R2 represents the right rear wheel.
Preferably, the vehicle rollover time determination module 10 specifically includes:
and the side acceleration passes through the Kalman filter, is input into the rollover prediction model, and then is output to the vehicle rollover time.
In summary, compared with the prior art, the above technical solutions provided by the present invention have the following advantages:
1. the technical scheme provided by the invention can not only judge the current vehicle side-tipping state, but also predict the vehicle side-tipping trend;
2. according to the technical scheme provided by the invention, the height measured by a vehicle height sensor (a suspension displacement sensor) is used as a measurement value of a system, and a Kalman filtering estimator is applied, so that the estimation and prediction precision of the roll state of the vehicle is obviously improved.
3. According to the technical scheme provided by the invention, the 1/4 suspension system is utilized to estimate the vertical force of the vehicle tire by using the height value measured by the vehicle height sensor (suspension displacement sensor), so that the estimation precision of the tire vertical force is obviously improved, and the calculated lateral load transfer rate LTR value is more accurate.
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 roll state and rollover prediction method is characterized by comprising the following steps:
acquiring 1/4 suspension models of the vehicle and roll dynamics models of the vehicle;
determining the vertical load of the vehicle tyre according to the 1/4 suspension model;
determining a first lateral load transfer rate in the current control period of the vehicle according to the vertical load;
acquiring a first preset transfer rate threshold;
judging whether the lateral load transfer rate is smaller than a first preset transfer rate threshold value or not to obtain a first judgment result;
if the first judgment result is less than the first judgment result, returning to the step of determining the vertical load of the vehicle tire according to the 1/4 suspension model so as to determine the vertical load of the vehicle tire in the next control cycle;
if the first judgment result is greater than or equal to the first judgment result, determining a second lateral load transfer rate in the current control period of the vehicle according to the roll dynamic model of the vehicle;
acquiring a second preset transfer rate threshold;
judging whether the second lateral load transfer rate is smaller than or equal to a second preset transfer rate threshold value or not to obtain a second judgment result;
if the second judgment result is less than or equal to the second judgment result, acquiring a lateral acceleration and rollover prediction model, and determining the rollover time of the vehicle according to the lateral acceleration and the rollover prediction model;
acquiring a preset time threshold, and judging whether the vehicle rollover time is greater than or equal to the preset time threshold to obtain a third judgment result;
if the third judgment result is greater than or equal to the third judgment result, returning to the step of determining the vertical load of the vehicle tire according to the 1/4 suspension model so as to determine the vertical load of the vehicle tire in the next control cycle;
if the third judgment result is less than the second preset transfer rate threshold, returning to the step of judging whether the second lateral load transfer rate is less than or equal to the second preset transfer rate threshold;
and if the second judgment result is greater than the first judgment result, sending a rollover alarm.
2. The method of predicting a roll state and a rollover of a vehicle as set forth in claim 1, wherein said 1/4 suspension model is:
wherein Δ z is the vertical relative displacement between the sprung and unsprung masses,
is sprung mass acceleration，
Is the vertical relative velocity between sprung and unsprung masses, msIs sprung mass, ksAs stiffness of the suspension, csFor damping of the suspension, i e [ L1, R1, L2, R2]L1 represents the left front wheel, R1 represents the right front wheel, L2 represents the left rear wheel, and R2 represents the right rear wheel.
3. The method of claim 1, wherein the roll dynamics model of the vehicle is:
in the formula (I), the compound is shown in the specification,
in order to set the roll angle of the vehicle,
in order to accelerate the roll angle of the vehicle,
is the vehicle roll angle velocity, msIs a sprung mass, ayAs lateral acceleration of the vehicle, hrcDistance of centre of mass to centre of roll on spring, IxIs the moment of inertia of the sprung mass about the x-axis of the vehicle coordinate system, g is the gravitational acceleration,
for the roll stiffness of the suspension system,
damping the roll angle of the suspension system.
4. According toThe method of predicting a roll state and a rollover of a vehicle of claim 1, wherein a formula is applied based on said 1/4 suspension model
Determining the vertical load of the vehicle tyre;
in the formula, FzFor vertical load, msIs the sprung mass, g is the gravitational acceleration, Δ z is the vertical relative displacement between the sprung and unsprung masses, muIs the unsprung mass of the spring,
is the vertical relative velocity between sprung and unsprung masses, zoFor the suspension height of the vehicle under static load, ksAs stiffness of the suspension, csFor damping of the suspension, i e [ L1, R1, L2, R2]L1 represents the left front wheel, R1 represents the right front wheel, L2 represents the left rear wheel, and R2 represents the right rear wheel.
5. The method according to claim 1, wherein determining the vehicle rollover time based on the lateral acceleration and the rollover prediction model comprises:
and after the lateral acceleration passes through a Kalman filter and is input into the rollover prediction model, outputting the rollover time of the vehicle.
6. A vehicle roll condition and rollover prediction system, comprising:
a model acquisition module for acquiring 1/4 a suspension model of the vehicle and a roll dynamics model of the vehicle;
a vertical load determination module for determining the vertical load of a vehicle tyre from said 1/4 suspension model;
the first lateral load transfer rate determining module is used for determining a first lateral load transfer rate in the current control period of the vehicle according to the vertical load;
the first preset transfer rate threshold acquisition module is used for acquiring a first preset transfer rate threshold;
the first judgment module is used for judging whether the lateral load transfer rate is smaller than the first preset transfer rate threshold value or not to obtain a first judgment result;
a first returning module for returning to the step of "determining the vertical load of the vehicle tire according to the 1/4 suspension model" to determine the vertical load of the vehicle tire in the next control cycle when the first judgment result is less than;
a second lateral load transfer rate determining module, configured to determine, according to the roll dynamics model of the vehicle, a second lateral load transfer rate in a current control cycle of the vehicle when the first determination result is greater than or equal to the first determination result;
the second preset transfer rate threshold acquisition module is used for acquiring a second preset transfer rate threshold;
the second judgment module is used for judging whether the second lateral load transfer rate is smaller than or equal to a second preset transfer rate threshold value or not to obtain a second judgment result;
the vehicle rollover time determining module is used for acquiring a lateral acceleration and a rollover prediction model when the second judgment result is less than or equal to the second judgment result, and determining the vehicle rollover time according to the lateral acceleration and the rollover prediction model;
the third judging module is used for acquiring a preset time threshold value, judging whether the vehicle rollover time is greater than or equal to the preset time threshold value or not, and obtaining a third judging result;
a second returning module, configured to, when the third determination result is greater than or equal to the third determination result, return to the step of determining the vertical load of the vehicle tire according to the 1/4 suspension model, so as to determine the vertical load of the vehicle tire in the next control cycle;
a third returning module, configured to, when the third determination result is less than the second predetermined threshold, return to the step of "determining whether the second lateral load transfer rate is less than or equal to a second predetermined transfer rate threshold";
and the rollover alarm module is used for sending a rollover alarm when the second judgment result is greater than the second judgment result.
7. The vehicle roll state and rollover prediction system according to claim 6, wherein the vertical load determination module includes:
a vertical load cell for applying a formula based on said 1/4 suspension model
Determining the vertical load of the vehicle tyre;
in the formula, FzFor vertical load, msIs the sprung mass, g is the gravitational acceleration, Δ z is the vertical relative displacement between the sprung and unsprung masses, muIs the unsprung mass of the spring,
is the vertical relative velocity between sprung and unsprung masses, zoFor the suspension height of the vehicle under static load, ksAs stiffness of the suspension, csFor damping of the suspension, i e [ L1, R1, L2, R2]L1 represents the left front wheel, R1 represents the right front wheel, L2 represents the left rear wheel, and R2 represents the right rear wheel.
8. The vehicle roll state and rollover prediction system according to claim 6, wherein the vehicle rollover time determination module specifically comprises:
and the lateral acceleration passes through the Kalman filter, is input into the rollover prediction model, and then is output to the vehicle rollover time.
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| CN113460107B (en) * | 2021-06-08 | 2022-06-24 | 合肥工业大学 | Anti-roll hydraulic interconnection system for railway vehicle |
| CN113449378B (en) * | 2021-06-23 | 2023-09-08 | 中国人民解放***箭军工程大学 | Transverse load transfer rate calculation method based on deformation of vehicle suspension |
| CN113635728B (en) * | 2021-08-18 | 2024-03-19 | 浙江吉利控股集团有限公司 | Vehicle roll stiffness adjustment method, apparatus, device, medium, and program product |
| CN113806958A (en) * | 2021-09-26 | 2021-12-17 | 上汽通用五菱汽车股份有限公司 | Anti-roll control method, device and storage medium based on MPC algorithm |
| CN113879282A (en) * | 2021-11-09 | 2022-01-04 | 杭州云栖智能汽车创新中心 | Automatic-driving vehicle rollover prevention control method |
| CN114312199B (en) * | 2022-01-10 | 2023-11-28 | 中国第一汽车股份有限公司 | Vehicle roll state determination method, device, equipment and medium |
| CN115946679B (en) * | 2023-03-15 | 2023-06-06 | 北京理工大学 | Vehicle stability judging method and system |
| CN116394691B (en) * | 2023-04-23 | 2024-02-06 | 小米汽车科技有限公司 | Trailer control method and device and vehicle |
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