CN113525393B - Vehicle longitudinal acceleration estimation method and system and computer equipment thereof - Google Patents

Abstract

The invention relates to a vehicle longitudinal acceleration estimation method, a system and computer equipment thereof, wherein the method comprises the following steps: acquiring a measured value of longitudinal acceleration measured by a vehicle inertial sensor at the current moment, and correcting the measured value of the longitudinal acceleration to obtain a first longitudinal acceleration; acquiring measured values of the wheel speeds of the first rear wheel and the second rear wheel, which are measured by the vehicle sensing unit at the current moment, and judging the reliability of the measured values of the wheel speeds of the first rear wheel and the second rear wheel; if at least one of the measured values of the first rear wheel speed and the second rear wheel speed is reliable, calculating a longitudinal acceleration estimated value at the current moment according to the measured value of the corresponding reliable rear wheel speed, and correcting the longitudinal acceleration estimated value to obtain second longitudinal acceleration; and determining the longitudinal acceleration at the current moment according to the first longitudinal acceleration and the second longitudinal acceleration. The invention can improve the accuracy of vehicle longitudinal acceleration estimation.

Description

Vehicle longitudinal acceleration estimation method and system, and computer equipment

Technical Field

The present invention relates to the technical field of vehicle state estimation, and in particular to a vehicle longitudinal acceleration estimation method and system, and computer equipment.

Background technique

The longitudinal acceleration of a vehicle is a very important state quantity of the vehicle. Some control systems of the vehicle require more accurate longitudinal acceleration. At present, wheel speed sensors are generally installed on passenger cars. The acceleration can be obtained by speed derivation, but the speed measurement noise is large. After derivation, the noise will be significantly amplified, reducing the accuracy of acceleration. Usually, the longitudinal acceleration can be obtained by low-pass filtering the speed and then derivation. However, due to the strong noise signal of the vehicle speed, a low cutoff frequency filter has to be used, and the delay is serious. In addition, this method of estimating longitudinal acceleration has a large error when the vehicle slips. Although most passenger cars are equipped with inertial sensors to measure longitudinal acceleration, the inertial sensors will be offset due to the slope and vehicle posture. Therefore, the method of measuring longitudinal acceleration using inertial sensors requires ramp and vehicle body posture correction, and accurate ramp estimation is currently difficult to achieve. The kinematic method can also be used to estimate the longitudinal acceleration. It is generally combined with Kalman filtering, but it fails to solve the problem of correcting the measurement information based on the inertial sensor, because the acceleration is generally not modeled in the Kalman filter estimation, and the change of acceleration is regarded as white noise, which has low accuracy.

Summary of the invention

The present invention aims to provide a vehicle longitudinal acceleration estimation method and system, and a computer device to improve the accuracy of vehicle longitudinal acceleration estimation.

In a first aspect, an embodiment of the present invention provides a method for estimating longitudinal acceleration of a vehicle, comprising:

Obtaining a measurement value of the longitudinal acceleration measured by the vehicle inertial sensor at a current moment, and correcting the measurement value of the longitudinal acceleration to obtain a first longitudinal acceleration;

Obtaining the measured values of the first rear wheel speed and the second rear wheel speed measured by the vehicle sensor unit at the current moment, and determining the reliability of the measured values of the first rear wheel speed and the second rear wheel speed;

If at least one of the measured values of the first rear wheel speed and the second rear wheel speed is reliable, the estimated longitudinal acceleration at the current moment is calculated according to the measured value of the corresponding reliable rear wheel speed, and the estimated longitudinal acceleration is corrected to obtain the second longitudinal acceleration; and the reliability of the first longitudinal acceleration and the second longitudinal acceleration is determined, and the longitudinal acceleration at the current moment is determined according to the first longitudinal acceleration, the second longitudinal acceleration and their reliability.

In a second aspect, an embodiment of the present invention further provides a vehicle longitudinal acceleration estimation system, comprising:

a first calculation unit, configured to obtain a measurement value of the longitudinal acceleration measured by the vehicle inertial sensor at a current moment, and to correct the measurement value of the longitudinal acceleration to obtain a first longitudinal acceleration;

a determination unit, configured to obtain the measured values of the first rear wheel speed and the second rear wheel speed measured by the vehicle sensing unit at a current moment, and determine the reliability of the measured values of the first rear wheel speed and the second rear wheel speed; and

The second calculation unit is used to calculate the second longitudinal acceleration at a current moment according to the measurement value of the corresponding reliable rear wheel speed if at least one of the measurement values of the first rear wheel speed and the second rear wheel speed is reliable, and determine the longitudinal acceleration at a current moment according to the first longitudinal acceleration, the second longitudinal acceleration and their reliability.

In a third aspect, an embodiment of the present invention further proposes a computer device, comprising: a vehicle longitudinal acceleration estimation system proposed according to an embodiment of the first aspect; or, a memory and a processor, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the processor executes the vehicle longitudinal acceleration estimation method proposed according to the embodiment of the second aspect.

The above technical solution has at least the following advantages: the longitudinal acceleration detected by the inertial sensor at the current moment is periodically obtained and corrected to obtain the first longitudinal acceleration, the longitudinal speed of the vehicle is periodically estimated using the rear wheel speed at the current moment, and a longitudinal acceleration is calculated based on the longitudinal speed estimate and corrected to obtain the second longitudinal acceleration, and finally the longitudinal acceleration of the vehicle at the current moment is obtained by analyzing the first longitudinal acceleration, the second longitudinal acceleration and their reliability at the current moment. The above technical solution can improve the estimation accuracy of the longitudinal rapid speed of the vehicle, which estimates the longitudinal acceleration by combining the wheel speed and the inertial sensor, and corrects the longitudinal acceleration obtained by the wheel speed and the inertial sensor respectively, and finally performs a comprehensive analysis based on the first longitudinal acceleration, the second longitudinal acceleration and their reliability, thereby improving the parameter estimation accuracy.

Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be embodied by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the description, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG. 1 is a flow chart of a method for estimating longitudinal acceleration of a vehicle according to an embodiment of the present invention.

FIG. 2 is a flow chart of a method for estimating vehicle longitudinal acceleration according to another embodiment of the present invention.

FIG3 is a schematic diagram showing the relationship between the longitudinal force and the slip rate of the tire under different vertical loads.

FIG. 4 is a schematic diagram of a specific flow chart of step S103 in FIG. 1-2 .

Detailed ways

Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

In addition, in order to better illustrate the present invention, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present invention can also be implemented without certain specific details. In some examples, means well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

As shown in FIG1 , an embodiment of the present invention provides a method for estimating longitudinal acceleration of a vehicle, comprising the following steps S101-S103:

Step S101, obtaining a measurement value of the longitudinal acceleration measured by the vehicle inertial sensor at the current moment, and correcting the measurement value of the longitudinal acceleration to obtain a first longitudinal acceleration;

Generally speaking, a vehicle inertial sensor includes an acceleration sensor and an angular velocity sensor. Therefore, a longitudinal acceleration can be obtained according to the vehicle inertial sensor signal. Since the longitudinal acceleration measured by the inertial sensor has a certain deviation, it needs to be properly corrected. There are many ways to correct it, which are not specifically limited in this embodiment.

Preferably, before the measured value of the longitudinal acceleration is corrected to obtain the first longitudinal acceleration, the measured value of the longitudinal acceleration is low-pass filtered to reduce noise.

Step S102, obtaining the measured values of the first rear wheel speed and the second rear wheel speed measured by the vehicle sensor unit at the current moment, and determining the reliability of the measured values of the first rear wheel speed and the second rear wheel speed;

Generally speaking, wheel speed sensors are installed on all four wheels of a passenger car, which can obtain wheel speed signals in real time and estimate the vehicle speed through the wheel speed. However, the driving wheel slips more than the non-driving wheel due to the driving force, and passenger cars are generally front-wheel drive, so the rear wheel speed is used here to estimate the vehicle speed. Among them, the reliability of the measured values of the first rear wheel speed and the second rear wheel speed is determined to eliminate the influence of accidental wheel slip and bounce on the acceleration estimation.

Preferably, before calculating the estimated value of the longitudinal acceleration at the current moment based on the corresponding reliable measured values of the rear wheel speeds, the measured values of the rear wheel speeds are low-pass filtered to reduce noise.

Step S103: If at least one of the measured values of the first rear wheel speed and the second rear wheel speed is reliable, the estimated value of the longitudinal acceleration at the current moment is calculated according to the measured value of the corresponding reliable rear wheel speed, and the estimated value of the longitudinal acceleration is corrected to obtain the second longitudinal acceleration; and the reliability of the first longitudinal acceleration and the second longitudinal acceleration is determined, and the longitudinal acceleration at the current moment is determined according to the first longitudinal acceleration, the second longitudinal acceleration and their reliability.

Specifically, determining the reliability of the first longitudinal acceleration and the second longitudinal acceleration is to reduce acceleration estimation noise and improve estimation accuracy.

The method of this embodiment estimates the longitudinal acceleration by combining the wheel speed and the inertial sensor, and makes corresponding corrections to the longitudinal acceleration obtained by the wheel speed and the inertial sensor, and finally performs a comprehensive analysis based on the first longitudinal acceleration, the second longitudinal acceleration and their reliability, thereby improving the parameter estimation accuracy.

In a specific embodiment, as shown in FIG2 , the method further includes:

Step S104: if the measured values of the first rear wheel speed and the second rear wheel speed are both unreliable, outputting the first longitudinal acceleration as the longitudinal acceleration at the current moment.

Specifically, when the measured values of the two rear wheel speeds are unreliable, it means that unexpected slip may have occurred, and the probability of this is very low. At this time, the first longitudinal acceleration after correction of the longitudinal acceleration measured by the inertial sensor is used as the vehicle longitudinal acceleration at the current moment.

In a specific embodiment, the step S102 of correcting the longitudinal acceleration estimate to obtain the second longitudinal acceleration specifically includes:

The vertical load and tire longitudinal force of the current vehicle are obtained, a corresponding slip ratio is obtained according to the vertical load and tire longitudinal force, and the longitudinal acceleration estimation value is corrected according to the slip ratio to obtain a second longitudinal acceleration.

Generally speaking, the rear two wheels of a passenger car are non-driving wheels. In most working conditions, their slip rate is low, and there is no need to consider the impact of tire slip on vehicle speed estimation. However, when the vehicle has strong braking, the tire has obvious slip and needs to be corrected. The tire slip rate estimation is obtained through the relationship between slip rate and longitudinal force. The relationship between slip rate and longitudinal force is different under different adhesion road surfaces and different vertical loads. Here, the high adhesion coefficient road surface is mainly considered.

Assume that the vehicle is running on a slope with a slope angle of θ, the longitudinal acceleration is a _x , the forward direction is positive, and the rear axle vertical force F _zr is:

F _zr = (mgL _f cosθ±mghsinθ-ma _x h)/L (1)

Where m is the vehicle mass, h is the height of the center of mass, L is the wheelbase, and L _f is the distance from the center of mass to the front axle. For passenger cars, these parameters can be considered as constants. The positive and negative signs in the formula are positive for uphill and negative for downhill.

In formula (1), the slope angle θ needs to be known, which can be obtained by the longitudinal acceleration obtained by the wheel speed and the longitudinal acceleration offset of the inertial acceleration sensor.

The relationship between the longitudinal acceleration a _xs measured by inertial acceleration and the actual longitudinal acceleration a _x of the vehicle is shown in formula (2):

Where L _cs is the lateral offset of the inertial sensor from the vehicle's rotation center when turning, Point is the yaw angular acceleration, is the pitch angle.

The unknown quantities in equation (2) are V _y and the pitch angle because

Where _ay is the lateral acceleration of the center of mass. By integrating equation (3), we can get the lateral velocity _{Vy. ay} can be measured by a sensor, and we have

Where L _ds is the longitudinal offset of the sensor, and the γ angle is the roll angle. Here, the roll gradient and lateral acceleration are used for approximation, namely:

γ＝ _{kcay (} 5)

Where _kc is the roll gradient, which can be obtained through testing.

For the pitch angle, we have:

Where m′ is the sprung mass, I′ _y =I _y +m′h ² , I _y is the moment of inertia of the sprung mass around the y-axis, _My is the y-axis torque, and the vertical displacement caused by pitch is ignored, and we have:

Where _Kf and _Kr are the spring stiffnesses used for the front and rear axle suspensions, respectively; _Rf and _Rr are the front and rear axle shock absorber characteristics, respectively.

Therefore, the above V _y and the estimated pitch angle Substituting into equation (2), the slope estimation can be obtained. After low-pass filtering, the slope estimation result is input into equation (1) for vertical force estimation.

When the vehicle brakes on a slope, the vehicle braking force _Fb is:

F _br ＝±mgsinθ-F _r -δmga _x (8)

Wherein, ± is positive when going downhill and negative when going uphill. δ is the rotational mass conversion coefficient, which can be calibrated based on different gears and can be approximately regarded as 1.03. F _r is the vehicle resistance when driving on flat ground, which can generally be obtained through coasting test. Usually, the acceleration caused by this item is small and will not cause large errors.

Among them, when the braking force is too large, the ABS will act. At this time, the front and rear wheel braking forces are related to the slip rate. However, in most cases, the vehicle braking ABS does not act, and the brake cylinder pressures of the front and rear wheels are consistent. The front and rear braking force distribution only depends on the structural parameters of the brake disc and the brake caliper, which can be obtained based on the pre-calibration test. Assuming that the rear wheel braking force accounts for the proportion of the total braking force is K _b , the rear wheel braking force is as shown in formula (9):

F _br ＝K _b F _b ＝K _b (±mgsinθ-F _r -δmga _x ) (9)

Through testing, the relationship between vertical force, longitudinal force and slip rate can be obtained, as shown in Figure 3. According to the two-dimensional pulse spectrum in Figure 3, the tire slip rate s can be obtained. The different curves in Figure 3 represent the relationship between the tire longitudinal force and slip rate under different vertical loads. Therefore, the corrected longitudinal acceleration is a _x /(1+s).

Therefore, based on the above, when the method of this embodiment uses the longitudinal vehicle speed to obtain a longitudinal acceleration _a2 , the corresponding tire slip rate s is obtained, and the longitudinal acceleration is corrected according to the above analysis content. The corrected second longitudinal acceleration is equal to _a2 /(1+s).

Since the above acceleration estimation method only considers kinematic factors, the vibration source of the tire is higher than that of the vehicle body, and its speed uncertainty is relatively large, dynamic compensation is introduced here to correct the estimated acceleration.

In a specific embodiment, the step S101 specifically includes:

Correcting the measured value of the longitudinal acceleration based on the slope and pitch angle at the current moment to obtain a first longitudinal acceleration;

Specifically, the longitudinal acceleration measured by the inertial sensor has a certain offset, and the offset is greatly affected by the slope of the road where the vehicle is located and the body posture. Therefore, in this embodiment, the longitudinal acceleration is corrected according to the slope and pitch angle. The relationship between the longitudinal acceleration measured by the inertial sensor and the actual vehicle longitudinal acceleration is shown in formula (2).

The first longitudinal acceleration should be equal to the actual longitudinal acceleration _ax . Therefore, after estimating the slope and pitch angle, the actual longitudinal acceleration can be calculated based on the yaw angular velocity using the longitudinal acceleration _axs measured by the inertial sensor and formula (2), and is used as the first longitudinal acceleration.

In a specific embodiment, the reliability determination of the first rear wheel speed and the second rear wheel speed in step S102 specifically includes:

Step S201, respectively calculating estimated values of the first rear wheel speed and the second rear wheel speed according to the first formula;

In this embodiment, the first formula is:

v′ _xw (k)＝v _x (k-1)+a _x (k-1)×dt±d _r ×r/2

Wherein, v′ _xw is the estimated value of the rear wheel speed, v _x (k-1) is the longitudinal vehicle speed at the previous moment, a _x (k-1) is the longitudinal acceleration at the previous moment, d _r is the wheelbase between the first rear wheel and the second rear wheel, r is the yaw rate at the current moment, dt is the time step between the current moment and the previous moment, when the calculated rear wheel is the steering outer wheel, ± is +, when the calculated rear wheel is the steering inner wheel, ± is -;

Step S202: Determine whether the first rear wheel speed is reliable based on a comparison result of the absolute value of the difference between the first rear wheel speed estimate and the first rear wheel speed measurement with a corresponding preset threshold, and determine whether the second rear wheel speed is reliable based on a comparison result of the absolute value of the difference between the second rear wheel speed estimate and the second rear wheel speed measurement with a corresponding preset threshold.

Specifically, when |v′ _xw (k)-v _xw (k)|<threshold, v _xw (k) is the current wheel speed measurement value, then the wheel speed is reliable, otherwise it is unreliable.

In a specific embodiment, the step S102 calculates the longitudinal acceleration of the current cycle according to the corresponding reliable rear wheel speed, specifically including:

Step S301: if only one of the measured values of the first rear wheel speed and the second rear wheel speed is reliable, then the longitudinal speed of the vehicle at the current moment is calculated according to the corresponding reliable measured value of the rear wheel speed and the second formula;

In this embodiment, the second formula is:

v _x (k) = v _xw (k) ± d _r × r / 2

Wherein, v _x (k) is the longitudinal velocity, v _xw (k) is the measured value of the rear wheel speed, d _r is the wheelbase between the first rear wheel and the second rear wheel, r is the yaw rate at the current moment, dt is the time step between the current moment and the previous moment, when the calculated rear wheel is the steering outer wheel, ± is +, when the calculated rear wheel is the steering inner wheel, ± is -.

Step S302: if the reliability of the measured values of the first rear wheel speed and the second rear wheel speed are both reliable, then the corresponding first longitudinal speed is calculated according to the measured value of the first rear wheel speed and the second formula, and the corresponding second longitudinal speed is calculated according to the measured value of the second rear wheel speed and the second formula, and the average of the first longitudinal speed and the second longitudinal speed is taken as the longitudinal speed of the vehicle at the current moment;

Step S303: derive the calculated vehicle longitudinal velocity at the current moment to obtain an estimated longitudinal acceleration value at the current moment.

In a specific embodiment, as shown in FIG4 , the step S103 specifically includes:

Step S401, obtaining the master cylinder pressure value at the current moment, and determining whether the master cylinder pressure value at the current moment is greater than the corresponding preset threshold;

Step S402: If the master cylinder pressure value at the current moment is greater than the corresponding preset threshold, obtain the change amount delta( _ax1 ) of the first longitudinal acceleration, the change amount delta( _ax2 ) of the second longitudinal acceleration and the change amount delta(P) of the master cylinder pressure value within the most recent time step, and determine the reliability of the first longitudinal acceleration and the second longitudinal acceleration according to delta( _ax1 ), delta( _ax2 ) and delta(P), and determine the longitudinal acceleration _ax (k) at the current moment according to the first longitudinal acceleration, the second longitudinal acceleration and their reliabilities.

The reliability of the first longitudinal acceleration and the second longitudinal acceleration is determined according to delta( _ax1 ), delta( _ax2 ) and delta(P), specifically including:

If |K _p ×delta(P)-delta(a _x1 )| is less than the corresponding preset threshold, the first longitudinal acceleration is reliable; if |K _p ×delta(P)-delta(a _x1 )| is greater than or equal to the corresponding preset threshold, the first longitudinal acceleration is unreliable;

If |K _p ×delta(P)-delta(a _x2 )| is less than the corresponding preset threshold, the second longitudinal acceleration is reliable; if |K _p ×delta(P)-delta(a _x2 )| is greater than or equal to the corresponding preset threshold, the second longitudinal acceleration is unreliable;

Among them, _Kp is the relationship between the acceleration change and the master cylinder pressure change, which can be calibrated in advance or identified online.

The step of obtaining the longitudinal acceleration a _x (k) at the current moment according to the first longitudinal acceleration, the second longitudinal acceleration and their reliability specifically includes:

If the first longitudinal acceleration and the second longitudinal acceleration are both reliable, and delta( _ax1 ) is less than delta( _ax2 ), the longitudinal acceleration _ax (k) at the current moment is calculated according to the longitudinal acceleration _ax (k-1) at the previous moment and delta( _ax1 ), that is, _ax (k)= _ax (k-1)+delta( _ax1 );

If the first longitudinal acceleration and the second longitudinal acceleration are both reliable, and delta( _ax2 ) is less than delta( _ax1 ), the longitudinal acceleration _ax (k) at the current moment is calculated according to the longitudinal acceleration _ax (k-1) at the previous moment and delta( _ax2 ), that is, _ax (k)= _ax (k-1)+delta( _ax2 );

If the first longitudinal acceleration is reliable and the second longitudinal acceleration is unreliable, the longitudinal acceleration _ax (k) at the current moment is calculated according to the longitudinal acceleration _ax (k-1) at the previous moment and delta( _ax1 ), that is, _ax (k)= _ax (k-1)+delta( _ax1 );

If the second longitudinal acceleration is reliable and the first longitudinal acceleration is unreliable, the longitudinal acceleration _ax (k) at the current moment is calculated according to the longitudinal acceleration _ax (k-1) at the previous moment and delta( _ax2 ), that is, _ax (k)= _ax (k-1)+delta( _ax2 );

If both the first longitudinal acceleration and the second longitudinal acceleration are unreliable, the longitudinal acceleration _ax (k) at the current moment is determined according to _ax (k-1), delta( _ax1 ), and delta( _ax2 ), and _ax1 and _ax2 are combined for estimation, i.e., _ax (k)= _ax (k-1)+k1×delta( _ax1 )+k2×delta( _ax2 ).

Among them, k1+k2=1 is a weighting coefficient, which gives k1 a larger weight when the vehicle does not have a large longitudinal and lateral acceleration and the inertial sensor signal fluctuation is small, otherwise it is given a smaller weight.

In a specific embodiment, as shown in FIG4 , the step S103 specifically includes:

Step S501, obtaining the master cylinder pressure value at the current moment, and determining whether the master cylinder pressure value at the current moment is greater than the corresponding preset threshold;

Step S502: if the master cylinder pressure value at the current moment is less than or equal to the corresponding preset threshold, the vehicle driving mode is obtained;

Step S503: If the vehicle driving mode is idle torque or in the gear shifting process, the longitudinal acceleration _ax (k-1) at the previous moment, as well as the change amount delta( _ax1 ) of the first longitudinal acceleration and the change amount delta( _ax2 ) of the second longitudinal acceleration in the most recent time step are obtained, and the longitudinal acceleration _ax (k) at the current moment is determined based on _ax (k-1), delta( _ax1 ) and delta( _ax2 ), and _ax1 and _ax2 are combined for estimation, that is, _ax (k)= _ax (k-1)+k1×delta( _ax1 )+k2×delta( _ax2 ).

Step S504: If the vehicle driving mode is in the driving condition, obtain the change amount delta( _ax1 ) of the first longitudinal acceleration, the change amount delta( _ax2 ) of the second longitudinal acceleration, and the change amount delta(T) of the engine torque in the most recent time step, and determine the reliability of the first longitudinal acceleration and the second longitudinal acceleration according to delta( _ax1 ), delta( _ax2 ), and delta(T), and determine the longitudinal acceleration _ax (k) at the current moment according to the first longitudinal acceleration, the second longitudinal acceleration, and their reliability.

The step of determining the reliability of the first longitudinal acceleration and the second longitudinal acceleration according to delta( _ax1 ), delta( _ax2 ) and delta(T) specifically includes:

If |K _t ×delta(T)-delta(a _x1 )| is less than the corresponding preset threshold, the first longitudinal acceleration is reliable; if |K _t ×delta(T)-delta(a _x1 )| is greater than or equal to the corresponding preset threshold, the first longitudinal acceleration is unreliable;

If |K _t ×delta(T)-delta(a _x2 )| is less than the corresponding preset threshold, the second longitudinal acceleration is reliable; if |K _t ×delta(T)-delta(a _x2 )| is greater than or equal to the corresponding preset threshold, the second longitudinal acceleration is unreliable;

Among them, _Kt is the engine torque change and acceleration change coefficient, which can be calibrated in advance or identified online.

The step of obtaining the longitudinal acceleration a _x (k) at the current moment according to the first longitudinal acceleration, the second longitudinal acceleration and their reliability specifically includes:

If the first longitudinal acceleration and the second longitudinal acceleration are both reliable, and delta( _ax1 ) is less than delta( _ax2 ), the longitudinal acceleration _ax (k) at the current moment is calculated according to the longitudinal acceleration _ax (k-1) at the previous moment and delta( _ax1 ), that is, _ax (k)= _ax (k-1)+delta( _ax1 );

If the first longitudinal acceleration and the second longitudinal acceleration are both reliable, and delta( _ax2 ) is less than delta( _ax1 ), the longitudinal acceleration _ax (k) at the current moment is calculated according to the longitudinal acceleration _ax (k-1) at the previous moment and delta( _ax2 ), that is, _ax (k)= _ax (k-1)+delta( _ax2 );

If the first longitudinal acceleration is reliable and the second longitudinal acceleration is unreliable, the longitudinal acceleration _ax (k) at the current moment is calculated according to the longitudinal acceleration _ax (k-1) at the previous moment and delta( _ax1 ), that is, _ax (k)= _ax (k-1)+delta( _ax1 );

If the second longitudinal acceleration is reliable and the first longitudinal acceleration is unreliable, the longitudinal acceleration _ax (k) at the current moment is calculated according to the longitudinal acceleration _ax (k-1) at the previous moment and delta( _ax2 ), that is, _ax (k)= _ax (k-1)+delta( _ax2 );

If both the first longitudinal acceleration and the second longitudinal acceleration are unreliable, the current longitudinal acceleration _ax (k) is determined according to _ax (k-1), delta( _ax1 ), and delta( _ax2 ), i.e., _ax (k)= _ax (k-1)+k1×delta( _ax1 )+k2×delta( _ax2 ).

The embodiment of the present invention further provides a vehicle longitudinal acceleration estimation system, which is used to implement the method of the above embodiment. The system of this embodiment includes:

a first calculation unit, configured to obtain a measurement value of the longitudinal acceleration measured by the vehicle inertial sensor at a current moment, and to correct the measurement value of the longitudinal acceleration to obtain a first longitudinal acceleration;

a determination unit, configured to obtain the measured values of the first rear wheel speed and the second rear wheel speed measured by the vehicle sensing unit at the current moment, and determine the reliability of the measured values of the first rear wheel speed and the second rear wheel speed;

The second calculation unit is used to calculate the second longitudinal acceleration at a current moment according to the measurement value of the corresponding reliable rear wheel speed if at least one of the measurement values of the first rear wheel speed and the second rear wheel speed is reliable, and determine the longitudinal acceleration at a current moment according to the first longitudinal acceleration, the second longitudinal acceleration and their reliability; if the measurement values of the first rear wheel speed and the second rear wheel speed are both unreliable, output the first longitudinal acceleration as the longitudinal acceleration at a current moment.

The system embodiment described above is merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

It should be noted that the system of the above embodiment corresponds to the method of the above embodiment. Therefore, the undescribed part of the system of the above embodiment can be obtained by referring to the content of the method of the above embodiment. The method steps of the above embodiment can be understood as the functionality/use limitation of the embodiment system and will not be repeated here.

Furthermore, if the vehicle longitudinal acceleration estimation system of the above embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium.

An embodiment of the present invention further provides a computer device, including a memory and a processor, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the processor executes the steps of the vehicle longitudinal acceleration estimation method described in the above embodiment.

Of course, the computer device may also have components such as a wired or wireless network interface, a keyboard, and an input/output interface for input and output. The computer device may also include other components for realizing the functions of the device, which will not be described in detail here.

Exemplarily, the computer program may be divided into one or more units, which are stored in the memory and executed by the processor to implement the present invention. The one or more units may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program in the computer device.

The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the computer device, and uses various interfaces and lines to connect various parts of the entire computer device.

The memory can be used to store the computer program and/or unit, and the processor realizes various functions of the computer device by running or executing the computer program and/or unit stored in the memory, and calling the data stored in the memory. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims (15)

1. A vehicle longitudinal acceleration estimation method, characterized by comprising:

acquiring a measured value of longitudinal acceleration measured by a vehicle inertial sensor at the current moment, and correcting the measured value of the longitudinal acceleration to obtain a first longitudinal acceleration;

acquiring measured values of a first rear wheel speed and a second rear wheel speed measured by a vehicle sensing unit at the current moment, and judging the reliability of the measured values of the first rear wheel speed and the second rear wheel speed;

If at least one of the measured values of the first rear wheel speed and the second rear wheel speed is reliable, calculating a longitudinal acceleration estimated value at the current moment according to the measured value of the corresponding reliable rear wheel speed, and correcting the longitudinal acceleration estimated value to obtain second longitudinal acceleration; the reliability of the first longitudinal acceleration and the second longitudinal acceleration is judged, and the longitudinal acceleration at the current moment is determined according to the first longitudinal acceleration, the second longitudinal acceleration and the reliability of the first longitudinal acceleration and the second longitudinal acceleration;

the determining of the reliability of the measured values of the first rear wheel speed and the second rear wheel speed specifically includes:

respectively calculating estimated values of the wheel speed of the first rear wheel and the wheel speed of the second rear wheel;

And judging whether the first rear wheel speed is reliable or not according to a comparison result of the absolute value of the difference between the first rear wheel speed estimated value and the first rear wheel speed measured value and a corresponding preset threshold value, and judging whether the second rear wheel speed is reliable or not according to a comparison result of the absolute value of the difference between the second rear wheel speed estimated value and the second rear wheel speed measured value and the corresponding preset threshold value.

2. The vehicle longitudinal acceleration estimation method according to claim 1, characterized in that the method includes:

And if the measured values of the wheel speeds of the first rear wheel and the second rear wheel are unreliable, outputting the first longitudinal acceleration as the longitudinal acceleration at the current moment.

3. The vehicle longitudinal acceleration estimation method according to claim 1, characterized in that the correcting the measured value of the longitudinal acceleration results in a first longitudinal acceleration, specifically:

And correcting the measured value of the longitudinal acceleration based on the gradient and the pitch angle at the current moment to obtain a first longitudinal acceleration.

4. The vehicle longitudinal acceleration estimation method according to claim 1, characterized in that the correcting the longitudinal acceleration estimation value to obtain a second longitudinal acceleration specifically includes:

and obtaining the vertical load and the tire longitudinal force of the current vehicle, obtaining the corresponding slip rate according to the vertical load and the tire longitudinal force, and correcting the longitudinal acceleration estimated value according to the slip rate to obtain the second longitudinal acceleration.

5. The vehicle longitudinal acceleration estimation method according to claim 4, wherein the estimated value calculation process of the first rear wheel speed and the second rear wheel speed is as follows:

wherein, As the wheel speed estimation value of the rear wheel,As the longitudinal vehicle speed at the previous time,For the longitudinal acceleration at the previous moment,For the tread between the first rear wheel and the second rear wheel,For the yaw rate at the present moment,For the time step between the current time and the last time, when the calculated rear wheel is the steering outside wheel,For +, when the calculated rear wheel is the steering inboard wheel,Is-.

6. The vehicle longitudinal acceleration estimation method according to claim 1, characterized in that the calculating the longitudinal acceleration estimation value at the current time from the measured value of the corresponding reliable rear wheel speed specifically includes:

if the reliability of one of the measured values of the first rear wheel speed and the second rear wheel speed is reliable, calculating the longitudinal speed of the vehicle at the current moment according to the measured value of the corresponding reliable rear wheel speed;

If the reliability of the measured values of the first rear wheel speed and the second rear wheel speed is reliable, calculating according to the measured value of the first rear wheel speed to obtain a corresponding first longitudinal speed, calculating according to the measured value of the second rear wheel speed to obtain a corresponding second longitudinal speed, and taking the average value of the first longitudinal speed and the second longitudinal speed as the longitudinal speed of the vehicle at the current moment;

And deriving the calculated longitudinal speed of the vehicle at the current moment to obtain a longitudinal acceleration estimated value at the current moment.

7. The vehicle longitudinal acceleration estimation method according to claim 6, wherein the calculation of the corresponding longitudinal speed from the measured value of the rear wheel speed is shown by the following expression:

wherein, In order to be a longitudinal velocity,As a measure of the wheel speed of the rear wheel,For the tread between the first rear wheel and the second rear wheel,For the yaw rate at the present moment,For the time step between the current time and the last time, when the calculated rear wheel is the steering outside wheel,For +, when the calculated rear wheel is the steering inboard wheel,Is-.

8. The vehicle longitudinal acceleration estimation method according to claim 1, characterized in that the determining the longitudinal acceleration at the current time based on the first and second longitudinal accelerations and the reliability thereof specifically includes:

Acquiring a master cylinder pressure value at the current moment, and judging whether the master cylinder pressure value at the current moment is larger than a corresponding preset threshold value or not;

If the master cylinder pressure value at the current moment is greater than the corresponding preset threshold value, the variation delta (a _x1) of the first longitudinal acceleration, the variation delta (a _x2) of the second longitudinal acceleration and the variation delta (P) of the master cylinder pressure value in the last time step are obtained, the reliability of the first longitudinal acceleration and the second longitudinal acceleration is judged according to the delta (a _x1) 、delta(a_x2) and the delta (P), and the longitudinal acceleration a _x (k) at the current moment is determined according to the first longitudinal acceleration, the second longitudinal acceleration and the reliability thereof.

9. The vehicle longitudinal acceleration estimation method according to claim 8, characterized in that the determining the first longitudinal acceleration and the second longitudinal acceleration reliability based on delta (a _x1) 、delta(a_x2) and delta (P) specifically includes:

if |K _p×delta(P)-delta(a_x1) | is smaller than the corresponding preset threshold, the first longitudinal acceleration is reliable, and if |K _p×delta(P)-delta(a_x1) | is larger than or equal to the corresponding preset threshold, the first longitudinal acceleration is unreliable;

If |K _p×delta(P)-delta(a_x2) | is smaller than the corresponding preset threshold, the second longitudinal acceleration is reliable, and |K _p×delta(P)-delta(a_x2) | is larger than or equal to the corresponding preset threshold, and the second longitudinal acceleration is unreliable;

Wherein K _p is a pre-calibrated parameter value.

10. The vehicle longitudinal acceleration estimation method according to claim 8, characterized in that the obtaining the longitudinal acceleration a _x (k) at the current time based on the first longitudinal acceleration and the second longitudinal acceleration and the reliability thereof, specifically includes:

If the first longitudinal acceleration and the second longitudinal acceleration are reliable and delta (a _x1) is smaller than delta (a _x2), calculating the longitudinal acceleration a _x (k) at the current moment according to the longitudinal acceleration a _x (k-1) and delta (a _x1) at the previous moment;

If the first longitudinal acceleration and the second longitudinal acceleration are reliable and delta (a _x2) is smaller than delta (a _x1), calculating the longitudinal acceleration a _x (k) at the current moment according to the longitudinal acceleration a _x (k-1) and delta (a _x2) at the previous moment;

If the first longitudinal acceleration is reliable and the second longitudinal acceleration is unreliable, calculating the longitudinal acceleration a _x (k) at the current moment according to the longitudinal acceleration a _x (k-1) and delta (a _x1) at the previous moment;

If the second longitudinal acceleration is reliable and the first longitudinal acceleration is unreliable, the longitudinal acceleration a _x (k) at the current time is calculated according to the longitudinal acceleration a _x (k-1) at the previous time and delta (a _x2).

11. The vehicle longitudinal acceleration estimation method according to claim 1, characterized in that the determining the longitudinal acceleration at the current time based on the first and second longitudinal accelerations and the reliability thereof specifically includes:

Acquiring a master cylinder pressure value at the current moment, and judging whether the master cylinder pressure value at the current moment is larger than a corresponding preset threshold value or not;

if the master cylinder pressure value at the current moment is smaller than or equal to a corresponding preset threshold value, acquiring a vehicle driving mode;

If the vehicle driving mode is idle torque or is in a gear shifting process, the longitudinal acceleration a _x (k-1) at the previous moment, the variation delta (a _x1) of the first longitudinal acceleration and the variation delta (a _x2) of the second longitudinal acceleration in the last time step are obtained, and the longitudinal acceleration a _x (k) at the current moment is determined according to the a _x(k-1)、delta(a_x1)、delta(a_x2;

If the vehicle driving mode is under the driving working condition, the variation delta (a _x1) of the first longitudinal acceleration, the variation delta (a _x2) of the second longitudinal acceleration and the variation delta (T) of the engine torque in the last time step are obtained, the reliability of the first longitudinal acceleration and the second longitudinal acceleration is judged according to the delta (a _x1) 、delta(a_x2) and the delta (T), and the longitudinal acceleration a _x (k) at the current moment is determined according to the first longitudinal acceleration and the second longitudinal acceleration and the reliability thereof.

12. The vehicle longitudinal acceleration estimation method according to claim 11, characterized in that the determining the first longitudinal acceleration and the second longitudinal acceleration reliability based on delta (a _x1) 、delta(a_x2) and delta (T) specifically includes:

If |K _t×delta(T)-delta(a_x1) | is smaller than the corresponding preset threshold, the first longitudinal acceleration is reliable, and if |K _t×delta(T)-delta(a_x1) | is larger than or equal to the corresponding preset threshold, the first longitudinal acceleration is unreliable;

If |K _t×delta(T)-delta(a_x2) | is smaller than the corresponding preset threshold, the second longitudinal acceleration is reliable, and |K _t×delta(T)-delta(a_x2) | is larger than or equal to the corresponding preset threshold, and the second longitudinal acceleration is unreliable;

Wherein K _t is a pre-calibrated parameter value.

13. The vehicle longitudinal acceleration estimation method according to claim 11, characterized in that the obtaining the longitudinal acceleration a _x (k) at the current time based on the first longitudinal acceleration and the second longitudinal acceleration and the reliability thereof, specifically includes:

If the first longitudinal acceleration and the second longitudinal acceleration are reliable and delta (a _x1) is smaller than delta (a _x2), calculating the longitudinal acceleration a _x (k) at the current moment according to the longitudinal acceleration a _x (k-1) and delta (a _x1) at the previous moment;

If the first longitudinal acceleration and the second longitudinal acceleration are reliable and delta (a _x2) is smaller than delta (a _x1), calculating the longitudinal acceleration a _x (k) at the current moment according to the longitudinal acceleration a _x (k-1) and delta (a _x2) at the previous moment;

If the first longitudinal acceleration is reliable and the second longitudinal acceleration is unreliable, calculating the longitudinal acceleration a _x (k) at the current moment according to the longitudinal acceleration a _x (k-1) and delta (a _x1) at the previous moment;

If the second longitudinal acceleration is reliable and the first longitudinal acceleration is unreliable, calculating the longitudinal acceleration a _x (k) at the current moment according to the longitudinal acceleration a _x (k-1) and delta (a _x2) at the previous moment;

If neither the first longitudinal acceleration nor the second longitudinal acceleration is reliable, the longitudinal acceleration a _x (k) at the current time is determined from a _x(k-1)、delta(a_x1)、delta(a_x2).

14. A vehicle longitudinal acceleration estimation system for implementing the method of any one of claims 1-13, comprising:

the first computing unit is used for acquiring a measured value of the longitudinal acceleration measured by the vehicle inertial sensor at the current moment and correcting the measured value of the longitudinal acceleration to obtain a first longitudinal acceleration;

A judging unit for acquiring the measured values of the first rear wheel speed and the second rear wheel speed measured by the vehicle sensing unit at the current moment and judging the reliability of the measured values of the first rear wheel speed and the second rear wheel speed; and

The second calculating unit is used for calculating the second longitudinal acceleration at the current moment according to the measured value of the corresponding reliable rear wheel speed and determining the longitudinal acceleration at the current moment according to the first longitudinal acceleration, the second longitudinal acceleration and the reliability of the second longitudinal acceleration if at least one of the measured values of the first rear wheel speed and the second rear wheel speed is reliable;

The determination unit is further configured to:

respectively calculating estimated values of the wheel speed of the first rear wheel and the wheel speed of the second rear wheel;

And judging whether the first rear wheel speed is reliable or not according to a comparison result of the absolute value of the difference between the first rear wheel speed estimated value and the first rear wheel speed measured value and a corresponding preset threshold value, and judging whether the second rear wheel speed is reliable or not according to a comparison result of the absolute value of the difference between the second rear wheel speed estimated value and the second rear wheel speed measured value and the corresponding preset threshold value.

15. A computer device, comprising: the vehicle longitudinal acceleration estimation system of claim 14; or a memory and a processor, the memory having stored therein computer readable instructions that, when executed by the processor, cause the processor to perform the vehicle longitudinal acceleration estimation method according to any one of claims 1-13.