CN110920625B - Decoupling and continuous estimation method for whole vehicle mass and road resistance of electric vehicle - Google Patents

Decoupling and continuous estimation method for whole vehicle mass and road resistance of electric vehicle Download PDF

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CN110920625B
CN110920625B CN201911180656.5A CN201911180656A CN110920625B CN 110920625 B CN110920625 B CN 110920625B CN 201911180656 A CN201911180656 A CN 201911180656A CN 110920625 B CN110920625 B CN 110920625B
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mass
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road resistance
whole vehicle
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CN110920625A (en
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陈宏伟
耿聪
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Beijing Jiaotong University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/02—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to ambient conditions
    • B60W40/06—Road conditions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/12—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to parameters of the vehicle itself, e.g. tyre models
    • B60W40/13—Load or weight
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/11—Complex mathematical operations for solving equations, e.g. nonlinear equations, general mathematical optimization problems
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/16—Matrix or vector computation, e.g. matrix-matrix or matrix-vector multiplication, matrix factorization

Abstract

The embodiment of the invention provides a decoupling estimation method for the whole vehicle mass and the road resistance of an electric vehicle, which comprises the following steps: decoupling and estimating the whole vehicle mass and the road resistance in the starting process, and acquiring a whole vehicle mass estimation mean value and a road resistance coefficient; and based on the estimated average value of the whole vehicle mass, a linear full-dimensional state observer is adopted to continuously estimate the road resistance coefficient in the vehicle running process. The invention also provides a continuous estimation method of the whole vehicle quality and the road resistance under the running cycle working condition. The embodiment of the invention is suitable for: the electric automobile which can accurately obtain the driving force of the power system and the braking torque of the braking system comprises a pure electric automobile, a hybrid electric automobile with pure electric starting capability and the like; an electric vehicle in which there is no mass change during driving; the estimated road resistance coefficient is the resultant of the grade and rolling resistances, and does not require a separate estimation of either grade or rolling resistance.

Description

Decoupling and continuous estimation method for whole vehicle mass and road resistance of electric vehicle
Technical Field
The invention relates to the technical field of traffic, in particular to a decoupling and continuous estimation method for the whole vehicle mass and the road resistance of an electric vehicle.
Background
For electric vehicles (pure electric vehicles or hybrid electric vehicles), energy management is an important content of vehicle control. The whole vehicle quality and the road resistance are important parameters influencing the energy management and the dynamic control of the electric vehicle. Only by accurately acquiring the mass of the whole vehicle and the road surface resistance parameters, the instantaneous energy consumption of the whole vehicle can be accurately calculated, which is one of the basic conditions for energy management optimization control.
Because the mass of the whole vehicle and the road resistance cannot be directly measured, various methods and algorithms are used for parameter estimation, and the method is a main means adopted in the industry at present. For example, a method of estimating mass and gradient simultaneously using a least square method; or the quality and the gradient are simultaneously observed by adopting the self-adaptive observer, the self-adaptive law is designed by applying the Lyapunov method, the observation stability is ensured, and the observation effect is better when the gradient of the road surface has severe fluctuation behaviors such as step change and the like; or a method in which the mass and the gradient are jointly estimated using a Kalman filter.
The method for estimating the whole vehicle mass and the road resistance is carried out on the basis of coupled dynamic analysis of the whole vehicle mass and the road resistance. In the longitudinal dynamics equation of the whole vehicle, the parameter estimation of the longitudinal dynamics equation and the parameter estimation of the longitudinal dynamics equation are mutually influenced by the coupling problem, and the difficulty and the calculated amount of an algorithm are increased.
Disclosure of Invention
The embodiment of the invention provides a decoupling and continuous estimation method for the whole vehicle mass and the road resistance of an electric vehicle, which overcomes the defects of the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme.
A decoupling estimation method for the whole vehicle mass and the road resistance of an electric vehicle comprises the following steps: decoupling and estimating the whole vehicle mass and the road resistance in the starting process, and acquiring a whole vehicle mass estimation mean value and a road resistance coefficient;
and continuously estimating the road resistance coefficient in the vehicle running process by adopting a linear full-dimensional state observer based on the whole vehicle mass estimation mean value.
Preferably, the decoupling estimation of the whole vehicle mass and the road resistance in the starting process is carried out to obtain the whole vehicle mass estimation mean value and the road resistance coefficient, and the method specifically comprises the following steps:
defining the road resistance coefficient as:
μ＝sinθ+fcosθ (1)
wherein f is a road surface rolling resistance coefficient, theta is a road surface slope angle, and the formula (1) shows that the road resistance coefficient is determined by the rolling resistance coefficient and the slope angle, and the road resistance is the sum of the rolling resistance and the slope resistance;
defining the driving torque coefficient as:
Figure GDA0002932045600000021
wherein igTo the speed ratio of the gearbox, i0The speed ratio of the main speed reducer, eta transmission efficiency and r are the rolling radius of the wheel;
when an automobile starts an electric control unit to initialize, setting the initial value of the mass of the whole automobile as follows:
Figure GDA0002932045600000022
wherein m is0For preparing the mass, mtSetting the initial value of the vehicle mass as the average value of the full-load mass and the full-load mass for the full-load mass, connecting the longitudinal kinetic equations of the vehicle at two sampling moments by assuming that the road resistance coefficients at the k-1 moment and the k moment of two adjacent sampling moments are not changed, and obtaining the vehicle mass at the k moment by adopting a null method
Figure GDA0002932045600000023
The estimated values of (c) are:
Figure GDA0002932045600000031
wherein M (k) is a motor drive torque at time k,
Figure GDA0002932045600000032
the longitudinal acceleration of the whole vehicle at the moment k, a is a driving torque coefficient and is defined by a formula (2), and delta is a rotating mass equivalent coefficient;
mean value of quality estimation of n sampling points
Figure GDA0002932045600000033
And normalized variance σmComprises the following steps:
Figure GDA0002932045600000034
Figure GDA0002932045600000035
angelicae sinensis for normalizing variance σmIs less than a set threshold value sigmam0When the mass estimation value is stable, the estimation is stopped, and the mean value of the mass estimation value of the whole vehicle at the moment is used
Figure GDA0002932045600000036
As a final result of the estimated quality, corresponding to the estimated quality
Figure GDA0002932045600000037
The road resistance coefficient of (a) is:
Figure GDA0002932045600000038
wherein n is the sampling frequency when stopping mass estimation, and g is the gravity acceleration.
Preferably, the continuously estimating the road resistance coefficient in the vehicle running process by using a linear full-dimensional state observer based on the vehicle mass estimation mean value comprises:
taking the finished automobile mass estimation value obtained in the formula (5) as an optimal value of finished automobile mass estimation, and keeping the finished automobile mass as a constant in the driving process;
defining equivalent driving/braking force Feq：
Figure GDA0002932045600000039
Wherein, M is the driving torque of the driving motor or the power assembly, M is a positive value during driving, and M is a negative value during braking if a feedback braking function exists; v is vehicle speed, ρ is air density, CdIs the wind resistance coefficient, AvIs the frontal area, Tb(i) The braking torque of each wheel brake, r is the rolling radius of the wheel;
setting a system state vector X as a two-dimensional column vector consisting of a longitudinal speed v and a road resistance coefficient mu, and setting an input quantity U as an equivalent driving/braking force FeqAnd a two-dimensional column vector formed by 0, wherein the system output Y is a longitudinal speed v:
Figure GDA0002932045600000041
the system state space model is as follows:
Figure GDA0002932045600000042
in equation (10), the matrices A, B, C are:
Figure GDA0002932045600000043
the system observation feedback matrix is set as follows:
Figure GDA0002932045600000044
λ in formula (12)1、λ2Are closed-loop system characteristic values, which are negative real numbers;
a linear full-dimensional state observer is designed by utilizing the system input quantity U, the output quantity Y and the observation feedback matrix G to realize the estimation of a system state vector X, and the closed-loop system state equation of the linear full-dimensional state observer can be expressed as follows:
Figure GDA0002932045600000045
discretizing the matrix differential equation (13) into a differential equation and solving the differential equation to obtain a real-time estimation of a system state vector X, namely a road resistance coefficient mu, and after the system constant matrix A, B, C, G is determined, carrying out the road resistance coefficient estimation according to the equation (13) in real time and continuously in the driving process after the vehicle starts so as to estimate the road resistance condition which is possibly and continuously changed;
when the road surface rolling resistance coefficient f is known, according to the estimated value of the road resistance coefficient mu, the road slope angle is obtained as follows:
Figure GDA0002932045600000051
a continuous estimation method for the whole vehicle mass and the road resistance under the running cycle working condition comprises the following specific steps:
1) VCU initialization: when the starting switch is turned ON to the ON position, the VCU sequentially realizes electrification, self-inspection and initialization, and assigns values to parameter variables required by the estimation of the whole vehicle mass and the road resistance;
2) estimating the vehicle mass for the first time of vehicle starting: the initial value of the automobile mass is the average value of the entire mass and the full load mass, the first mass estimation is carried out according to the formulas (1) to (7), and the average value of the mass estimation values is used as the optimal value of the whole automobile mass estimation after convergence;
3) different road resistance estimations are performed depending on the vehicle acceleration: after the estimation of the mass of the whole vehicle is converged for the first time, the mass of the whole vehicle is considered as a constant;
when the acceleration is larger than or equal to zero, the whole vehicle is in the acceleration or uniform speed driving stage, and F is calculated according to the equivalent driving force formula of the formula (8)eqSolving a differential equation (13) to estimate the road resistance in the driving process;
when the acceleration is less than zero, the whole vehicle is in the deceleration braking driving stage, and F is calculated according to the formula (8) of the equivalent braking forceeqSolving a differential equation (13) to estimate the road resistance in the braking process;
when the vehicle speed is not zero, continuously estimating the road resistance in the driving and braking processes through the positive and negative of the acceleration;
4) judging and deciding the parking state: when the vehicle speed is zero, the vehicle stops, and the driving intention of a driver is judged through a starting switch at the moment;
if the starting switch is in the OFF position, the driving intention is to stop the vehicle for a long time, and the program operation is ended;
if the starting switch is still in the ON position, the temporary stop is indicated, and the driver is waited to start again;
5) estimating the mass of the whole vehicle after temporary parking again: when the vehicle is started again after being stopped, the vehicle gets on/off passengers or loads and unloads goods, the mass of the whole vehicle is changed, and the mass estimation is carried out again; and at the moment, the finished automobile mass estimation convergence value before parking is used as an initial value of the next round of mass estimation, and the mass estimation module is returned to perform mass estimation again.
According to the technical scheme provided by the embodiment of the invention, the embodiment of the invention provides a decoupling and continuous estimation method for the whole vehicle mass and the road resistance of the electric vehicle, which is applicable to the following ranges:
(1) the electric automobile with accurately obtained driving force of a power system and braking torque of a braking system comprises a pure electric automobile, a hybrid electric automobile with pure electric starting capability and the like.
(2) The electric automobile has no mass change in the driving process.
(3) The estimated road resistance coefficient is the resultant of the grade and rolling resistances, and does not require a separate estimation of either grade or rolling resistance.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced 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 based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a decoupling estimation process of the whole vehicle mass and the road surface resistance in a starting process;
FIG. 2 is a schematic diagram of a continuous estimation process of vehicle mass and road resistance under a driving cycle condition.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.
The embodiment of the invention provides a decoupling estimation method for the whole vehicle mass and the road resistance of an electric vehicle, which specifically comprises the following steps:
1. decoupling estimation is carried out on the whole vehicle mass and the road resistance in the starting process, and a whole vehicle mass estimation mean value and a road resistance coefficient are obtained, as shown in fig. 1, the method comprises the following steps:
the electric automobile and the hybrid electric automobile are both started electrically, the motor driving torque can be accurately obtained, and the mass of the whole automobile can be considered as a constant in the driving process. In consideration of the characteristics, based on the analysis of the longitudinal dynamics of the automobile, the following decoupling estimation algorithm is provided.
Defining the road resistance coefficient as:
μ＝sinθ+fcosθ (1)
wherein f is the road surface rolling resistance coefficient, and theta is the road surface slope angle. From the equation (1), the road resistance coefficient is determined by the rolling resistance coefficient and the slope angle. Road resistance, as defined herein, is the sum of rolling resistance and grade resistance.
Defining the driving torque coefficient as:
Figure GDA0002932045600000081
wherein igTo the speed ratio of the gearbox, i0The speed ratio of the main speed reducer, eta transmission efficiency and r are the rolling radius of the wheel.
When an automobile starts an electric control unit to initialize, setting the initial value of the mass of the whole automobile as follows:
Figure GDA0002932045600000082
wherein m is0For preparing mass mtIs the full load mass. Namely, the initial value of the mass of the whole vehicle is set as the average value of the service mass and the full load mass. Assuming that the road resistance coefficients of two adjacent sampling moments (k-1 moment and k moment) are not changed, connecting the automobile longitudinal dynamics equations of the two sampling moments, and obtaining the automobile mass at the k moment by adopting an elimination method
Figure GDA0002932045600000083
The estimated values of (c) are:
Figure GDA0002932045600000084
where M (k) is the motor drive torque at time k,
Figure GDA0002932045600000091
the longitudinal acceleration of the whole vehicle at the moment k, a is a driving torque coefficient and is defined by an equation (2), and delta is a rotating mass equivalent coefficient.
Mean value of quality estimation of n sampling points
Figure GDA0002932045600000092
And normalized variance σmComprises the following steps:
Figure GDA0002932045600000093
Figure GDA0002932045600000094
angelicae sinensis for normalizing variance σmIs less than a set threshold value sigmam0Considering the mass estimation value to be stable, stopping estimation, and taking the mean value of the mass estimation value of the whole vehicle at the moment
Figure GDA0002932045600000095
As a final result of estimating the quality. Corresponding to the estimated quality
Figure GDA0002932045600000096
The road resistance coefficient of (a) is:
Figure GDA0002932045600000097
where n is the sampling time when stopping the quality estimation.
The method for estimating the decoupling of the vehicle mass and the road resistance, which is composed of the formulas (1) to (7), is shown in a program block diagram of fig. 1.
2. And (3) continuously estimating the road resistance coefficient in the vehicle running process by adopting a linear full-dimensional state observer based on the whole vehicle mass estimation mean value:
after the estimated value of the whole vehicle mass given by the formula (5) is obtained, the best estimation result of the whole vehicle mass is considered, and the whole vehicle mass is kept constant in the driving process. On the basis, a linear full-dimensional state observer for estimating the road resistance coefficient is provided, and the road resistance coefficient estimation of the vehicle in the running process is continuously carried out.
Defining equivalent driving/braking force Feq：
Figure GDA0002932045600000101
Wherein, M is the driving torque of the driving motor or the power assembly, and M is a positive value during driving, and if a feedback braking function exists, M is a negative value during braking. v is vehicle speed, ρ is air density, CdIs the wind resistance coefficient, AvIs the frontal area, Tb(i) R is the wheel rolling radius, which is the braking torque of each wheel brake.
Setting a system state vector X as a two-dimensional column vector consisting of a longitudinal speed v and a road resistance coefficient mu, and setting an input quantity U as an equivalent driving/braking force FeqAnd a two-dimensional column vector formed by 0, wherein the system output Y is a longitudinal speed v:
Figure GDA0002932045600000102
the system state space model is as follows:
Figure GDA0002932045600000103
Y＝CX (10)
in equation (10), the matrices A, B, C are:
Figure GDA0002932045600000104
the system observation feedback matrix is set as follows:
Figure GDA0002932045600000105
λ in formula (12)1、λ2The characteristic values of the closed-loop system are negative real numbers.
And designing a linear full-dimensional state observer by using the system input quantity U, the output quantity Y and the observation feedback matrix G to realize the estimation of the system state vector X. The linear full-dimensional state observer closed-loop system state equation can be expressed as:
Figure GDA0002932045600000111
and discretizing the matrix differential equation (13) into a differential equation and solving the differential equation to obtain the real-time estimation of a system state vector X, namely the road resistance coefficient mu. After the system constant matrix A, B, C, G is determined, road resistance coefficient estimation as per equation (13) is continued in real time during vehicle travel after vehicle launch to estimate road resistance conditions that may be constantly changing.
When the road surface rolling resistance coefficient f is known, according to the estimated value of the road resistance coefficient mu, the road slope angle is obtained as follows:
Figure GDA0002932045600000112
(8) a method for estimating a road drag coefficient by a linear full-dimensional state observer, which comprises the following expressions (14).
The invention also provides a continuous estimation method of the whole vehicle mass and the road resistance under the running cycle working condition, as shown in fig. 2, the specific steps are as follows:
in various driving cycles, the vehicle sequentially drives in the states of starting, accelerating, uniform speed, decelerating and braking, temporary stopping and the like. Different estimation strategies of the whole vehicle mass and the road resistance are put forward in a targeted manner at different stages of the driving cycle, and real-time continuous estimation of the two parameters is realized.
1) VCU initialization
When the starting switch is turned ON to the ON position, the VCU sequentially realizes electrification, self-checking and initialization, and assigns values to parameter variables required by the whole vehicle mass and the road resistance estimation.
2) First vehicle mass estimation for vehicle launch
And the initial value of the automobile mass is the average value of the entire mass and the full-load mass, the first mass estimation is carried out according to the formulas (1) to (7), and the average value of the mass estimation value is taken as the optimal value of the whole automobile mass estimation after convergence.
3) Implementing different road resistance estimations according to vehicle acceleration
After the first vehicle mass estimation converges, the mass is considered to be a constant.
When the acceleration is larger than or equal to zero, the whole vehicle is in the acceleration or constant speed driving stage, and F is calculated by the road resistance module in the constant speed/acceleration process according to the formula (8) equivalent driving force formulaeqAnd solving a differential equation (13) to estimate the road resistance in the driving process.
When the acceleration is less than zero, the whole vehicle is in the deceleration braking driving stage, and F is calculated by the road resistance module in the braking process according to the formula (8) equivalent braking force formulaeqAnd solving a differential equation (13) to estimate the road resistance in the braking process.
When the vehicle speed is not zero, the road resistance estimation in the driving and braking process is continuously carried out through the positive and negative of the acceleration.
4) Determination and decision of parking status
When the vehicle speed is zero, the vehicle is stopped, and the driving intention of the driver is judged through the starting switch.
If the start switch is in the OFF position, indicating that the driving intention is a long-time stop, the program operation is ended.
If the start switch is still in the ON position, indicating a temporary stop, the driver is waited to take off again.
5) Re-estimation of vehicle mass after temporary stop
When the vehicle is started again after being stopped, the vehicle is possible to get on/off passengers or load and unload goods, the mass of the whole vehicle is changed, and the mass estimation needs to be carried out again. And at the moment, the convergence value of the whole vehicle mass estimation before parking is used as an initial value of the next round of mass estimation, and the mass estimation is carried out again according to the formulas (1) to (7) by returning to the mass estimation calculation module.
The continuous estimation strategy of the whole vehicle mass and the road resistance under the driving cycle working condition is shown as a program block diagram shown in fig. 2.
In summary, the embodiments of the present invention provide a whole vehicle mass estimation method based on a decoupling algorithm, a road resistance estimation method using a full-dimensional state observer and considering driving and braking processes, and a control strategy for continuously estimating the whole vehicle mass and the road resistance at different stages of a driving cycle for the first time, aiming at the characteristics of an electric vehicle, and the calculation method is simple and practical, and can be used in a vehicle real-time control system requiring on-line estimation of the whole vehicle mass and the road resistance coefficient.
Those of ordinary skill in the art will understand that: the figures are merely schematic representations of one embodiment, and the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.
From the above description of the embodiments, it is clear to those skilled in the art that the present invention can be implemented by software plus necessary general hardware platform. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which may be stored in a storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method according to the embodiments or some parts of the embodiments.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (3)

1. A decoupling estimation method for the whole vehicle mass and the road resistance of an electric vehicle is characterized by comprising the following steps: decoupling and estimating the whole vehicle mass and the road resistance in the starting process, and acquiring a whole vehicle mass estimation mean value and a road resistance coefficient;
based on the whole vehicle mass estimation mean value, a linear full-dimensional state observer is adopted to continuously estimate the road resistance coefficient in the vehicle running process;
the method comprises the following steps of decoupling estimation of the whole vehicle mass and the road resistance in the starting process, obtaining a whole vehicle mass estimation mean value and a road resistance coefficient, and specifically comprises the following steps:
defining the road resistance coefficient as:
μ＝sinθ+f cosθ (1)
wherein f is a road surface rolling resistance coefficient, theta is a road surface slope angle, and the formula (1) shows that the road resistance coefficient is determined by the rolling resistance coefficient and the slope angle, and the road resistance is the sum of the rolling resistance and the slope resistance;
defining the driving torque coefficient as:
Figure FDA0002932045590000011
wherein igTo the speed ratio of the gearbox, i0The speed ratio of the main speed reducer, eta transmission efficiency and r are the rolling radius of the wheel;
when an automobile starts an electric control unit to initialize, setting the initial value of the mass of the whole automobile as follows:
Figure FDA0002932045590000012
wherein m is0For preparing the mass, mtSetting the initial value of the vehicle mass as the average value of the full-load mass and the full-load mass for the full-load mass, connecting the longitudinal kinetic equations of the vehicle at two sampling moments by assuming that the road resistance coefficients at the k-1 moment and the k moment of two adjacent sampling moments are not changed, and obtaining the vehicle mass at the k moment by adopting a null method
Figure FDA0002932045590000013
The estimated values of (c) are:
Figure FDA0002932045590000021
wherein M (k) is a motor drive torque at time k,
Figure FDA0002932045590000022
the longitudinal acceleration of the whole vehicle at the moment k, a is a driving torque coefficient and is defined by a formula (2), and delta is a rotating mass equivalent coefficient;
mean value of quality estimation of n sampling points
Figure FDA0002932045590000023
And normalized variance σmComprises the following steps:
Figure FDA0002932045590000024
Figure FDA0002932045590000025
angelicae sinensis for normalizing variance σmIs less than a set threshold value sigmam0When the mass estimation value is stable, the estimation is stopped, and the mean value of the mass estimation value of the whole vehicle at the moment is used
Figure FDA0002932045590000026
As a final result of the estimated quality, corresponding to the estimated quality
Figure FDA0002932045590000027
The road resistance coefficient of (a) is:
Figure FDA0002932045590000028
wherein n is the sampling frequency when stopping mass estimation, and g is the gravity acceleration.
2. The method according to claim 1, wherein the continuous estimation of the road resistance coefficient during the vehicle driving process by adopting a linear full-dimensional state observer based on the vehicle mass estimation mean value comprises the following steps:
taking the finished automobile mass estimation value obtained in the formula (5) as an optimal value of finished automobile mass estimation, and keeping the finished automobile mass as a constant in the driving process;
defining equivalent driving/braking force Feq：
Figure FDA0002932045590000031
Wherein M is a driving motor or a power assembly driving rotorMoment, M is a positive value when driving, and M is a negative value when braking if a feedback braking function exists; v is vehicle speed, ρ is air density, CdIs the wind resistance coefficient, AvIs the frontal area, Tb(i) The braking torque of each wheel brake, r is the rolling radius of the wheel;
setting a system state vector X as a two-dimensional column vector consisting of a longitudinal speed v and a road resistance coefficient mu, and setting an input quantity U as an equivalent driving/braking force FeqAnd a two-dimensional column vector formed by 0, wherein the system output Y is a longitudinal speed v:
Figure FDA0002932045590000032
the system state space model is as follows:
Figure FDA0002932045590000033
in equation (10), the matrices A, B, C are:
Figure FDA0002932045590000034
the system observation feedback matrix is set as follows:
Figure FDA0002932045590000035
λ in formula (12)1、λ2Are closed-loop system characteristic values, which are negative real numbers;
a linear full-dimensional state observer is designed by utilizing the system input quantity U, the output quantity Y and the observation feedback matrix G to realize the estimation of a system state vector X, and the closed-loop system state equation of the linear full-dimensional state observer can be expressed as follows:
Figure FDA0002932045590000041
discretizing the matrix differential equation (13) into a differential equation and solving the differential equation to obtain a real-time estimation of a system state vector X, namely a road resistance coefficient mu, and after the system constant matrix A, B, C, G is determined, carrying out the road resistance coefficient estimation according to the equation (13) in real time and continuously in the driving process after the vehicle starts so as to estimate the road resistance condition which is possibly and continuously changed;
when the road surface rolling resistance coefficient f is known, according to the estimated value of the road resistance coefficient mu, the road slope angle is obtained as follows:
Figure FDA0002932045590000042
3. a continuous estimation method for the whole vehicle mass and the road resistance under the running cycle working condition is characterized in that the decoupling estimation method for the whole vehicle mass and the road resistance of the electric vehicle in claim 2 is utilized, and the specific steps comprise:
1) VCU initialization: when the starting switch is turned ON to the ON position, the VCU sequentially realizes electrification, self-inspection and initialization, and assigns values to parameter variables required by the estimation of the whole vehicle mass and the road resistance;
2) estimating the vehicle mass for the first time of vehicle starting: the initial value of the automobile mass is the average value of the entire mass and the full load mass, the first mass estimation is carried out according to the formulas (1) to (7), and the average value of the mass estimation values is used as the optimal value of the whole automobile mass estimation after convergence;
3) different road resistance estimations are performed depending on the vehicle acceleration: after the estimation of the mass of the whole vehicle is converged for the first time, the mass of the whole vehicle is considered as a constant;
when the acceleration is larger than or equal to zero, the whole vehicle is in the acceleration or uniform speed driving stage, and F is calculated according to the equivalent driving force formula of the formula (8)eqSolving a differential equation (13) to estimate the road resistance in the driving process;
when the acceleration is less than zero, the whole vehicle is in the deceleration braking driving stage(8) Equation of equivalent braking force calculation FeqSolving a differential equation (13) to estimate the road resistance in the braking process;
when the vehicle speed is not zero, continuously estimating the road resistance in the driving and braking processes through the positive and negative of the acceleration;
4) judging and deciding the parking state: when the vehicle speed is zero, the vehicle stops, and the driving intention of a driver is judged through a starting switch at the moment;
if the starting switch is in the OFF position, the driving intention is to stop the vehicle for a long time, and the program operation is ended;
if the starting switch is still in the ON position, the temporary stop is indicated, and the driver is waited to start again;
5) estimating the mass of the whole vehicle after temporary parking again: when the vehicle is started again after being stopped, the vehicle gets on/off passengers or loads and unloads goods, the mass of the whole vehicle is changed, and the mass estimation is carried out again; and at the moment, the finished automobile mass estimation convergence value before parking is used as an initial value of the next round of mass estimation, and the mass estimation module is returned to perform mass estimation again.
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