CN106004881A - Road adhesion coefficient estimation method based on frequency domain fusion - Google Patents

Abstract

The invention relates to a road adhesion coefficient estimation method based on frequency domain fusion. The road adhesion coefficient estimation method is characterized in that an adhesion coefficient estimated value based on longitudinal resonance frequency of a vehicle and an adhesion coefficient estimated value based on resonance frequency of a steering system are subjected to frequency domain fusion to estimate the final adhesion coefficient. Frequency domain fusion refers to that the adhesion coefficient estimated value based on longitudinal resonance frequency of the vehicle is enabled to pass through a high-pass filter, the adhesion coefficient estimated value based on resonance frequency of the steering system is enabled to pass through a low-pass filter, and two results obtained after filtration are added together to serve as the final adhesion coefficient estimated result. The road adhesion coefficient estimation method not only eliminates influences of signal noise and error information on road adhesion estimation but also avoids the defect of slow adhesion estimation convergence caused by long dynamic delay of the steering system.

Description

The coefficient of road adhesion method of estimation merged based on frequency domain

Technical field

The present invention relates to the method for estimation of a kind of coefficient of road adhesion, kept straight on especially with regard to a kind of vehicle normal table The real-time estimation method of coefficient of road adhesion in journey.

Background technology

Modern vehicle control system includes multiple subsystem, and wagon control effect depends not only on entire car controller Controlling, but also need to rely on the vehicle parameter information gathered, each system of vehicle needs profit when carrying out parameter estimation By vehicle and environmental information, if the ambient parameter of some the unknowns can be estimated in real time, it is possible not only to improve vehicle The precision of Controlling model, and wagon control effect can be effectively improved.The wherein attachment coefficient letter of vehicle running surface Cease the brake hard for vehicle, active safety control and Anti-slip regulation to control to be all very important.

In existing leading technology the most, the attachment coefficient method of estimation to vehicle running surface includes based on longitudinal direction of car altogether The attachment coefficient method of estimation of vibration frequency and attachment coefficient method of estimation based on steering resonant frequency.Wherein, base In the attachment coefficient method of estimation of longitudinal direction of car resonant frequency due to by the static deviation of wheel speed sensors and signal noise shadow Ring bigger, it is impossible to obtain estimation difference at a stable estimated result, i.e. the method low frequency relatively big, but vehicle Longitudinal motion response is quick, and the method can accurately perceive the dynamic change of road surface attachment condition, i.e. captures attached The high-frequency information of coefficient；On the contrary, attachment coefficient method of estimation based on steering resonant frequency can reduce signal The noise impact on estimated result, i.e. can obtain relatively stable and that accuracy is high stable state estimated result, but the method Owing to Vehicular turn motion is relatively slow, causing the estimation time longer, attachment estimates that convergence is slow.

Summary of the invention

For the problems referred to above, it is an object of the invention to provide a kind of coefficient of road adhesion method of estimation merged based on frequency domain, This is also a kind of can accurately to estimate the real-time estimation method of road gradient in vehicle travel process.The method builds on car On the basis of the attachment coefficient of longitudinal resonance frequencies is estimated and the attachment coefficient of steering resonant frequency estimates, carry out frequency Territory fusion treatment, it is possible to obtain attachment coefficient estimated value the most quickly and accurately.

For achieving the above object, the present invention takes techniques below scheme: a kind of coefficient of road adhesion merged based on frequency domain Method of estimation, is attachment coefficient estimated value μ that will obtain based on longitudinal direction of car resonant frequency_max1With based on steering system altogether Attachment coefficient estimated value μ that vibration frequency obtains_max2, both are filtered processing, merge based on frequency domain obtain final attached Coefficient

Attachment coefficient μ based on longitudinal direction of car resonant frequency_max1Estimation procedure is:

1) attachment coefficient estimation module based on longitudinal direction of car resonant frequency obtains wheel speed signal ω and Real Time Drive in real time Torque T_dOn the basis of, utilize the Spectrum Analyzer module in MATLAB software, estimate longitudinal resonance frequencies f_0-x；

2) attachment coefficient estimated value μ it is then based on_max1With longitudinal resonance frequencies f_0-xBetween relation, estimate attachment Coefficient estimation value μ_max1:

$f_{0-x}=\frac{R}{2\mathrm{\π}}\sqrt{\frac{{\mathrm{a\μ}}_{\max 1}+b}{{\mathrm{Ir}}_x}}---\left(1\right)$

In formula, R is vehicle wheel roll radius, and I is vehicle wheel rotation inertia, r_xFor the longitudinal relaxation length of tire, it is logical Crossing the conventional method amount of would know that, a and b is two constants, is the empirical value determined according to test of many times matching.

Attachment coefficient μ based on steering resonant frequency_max2Estimation procedure is:

1) attachment coefficient estimation module based on steering resonant frequency obtains steering wheel rotational angular velocity signal in real time ω_sOn the basis of the power torque T of steering assist motor, utilize the Spectrum Analyzer in MATLAB software Module, estimates steering resonant frequency f_0-y；

2) attachment coefficient estimated value μ it is then based on_max2With steering resonant frequency f_0-yBetween relation, estimate Attachment coefficient estimated value μ_max2:

$f_{0-y}=\frac{1}{2{\mathrm{\πG}}_s}\sqrt{\frac{{\mathrm{c\μ}}_{max2}+d}{J_d}}---\left(2\right)$

G in formula_sFor steering gear ratio；J_dFor the rotary inertia of front-wheel and steering mechanism's equivalence to steering column, all For by the conventional method amount of would know that, c and d is two constants, is the empirical value determined according to test of many times matching..

The attachment coefficient merged based on frequency domainEstimation procedure is:

Frequency domain merges attachment estimation module attachment coefficient estimated value μ to obtaining based on longitudinal direction of car resonant frequency_max1With Attachment coefficient estimated value μ obtained based on steering resonant frequency_max2, it is filtered respectively processing, wherein to μ_max1 High pass filter is used to filter its low frequency part, reserved high-frequency part；To μ_max2Low pass filter is used to filter its high frequency Part, retains low frequency part；Then after filtering two, the result of output, utilizes following relational expression to obtain

${\widehat{\mathrm{\μ}}}_{max}=\frac{1}{\mathrm{\τ}s+1}{\mathrm{\μ}}_{max2}+\frac{\mathrm{\τ}s}{\mathrm{\τ}s+1}{\mathrm{\μ}}_{max1}---\left(3\right)$

In formula, τ is time constant, and s is Laplace operator,For low-pass filtering coefficient,Filter for high pass Wave system number.

Further, the described coefficient of road adhesion method of estimation merged based on frequency domain realizes based on a real-time estimating system, Described system includes:

The driving torque sensor that one is arranged on driver for vehicle, driving torque T of real-time reception vehicle_d；

One is arranged on the wheel speed sensors at wheel, the wheel speed signal ω of real-time reception vehicle；

One is arranged on the steering wheel angle sensor at steering column tube and steering assist motor, the direction of real-time reception vehicle Dish rotational angular velocity signal ω_sWith power torque T；

One attachment coefficient estimation module based on longitudinal direction of car resonant frequency, an attachment based on steering resonant frequency Coefficient estimation module and a frequency domain merge attachment estimation module, are all integrated in entire car controller, built-in MATLAB algorithm Program.

Due to the fact that and take above technical scheme, it has the advantage that the present invention is to road surface in vehicle travel process When attachment coefficient is estimated in real time, by gathering driving force signal, wheel speed signal and steering assist motor torque, side To dish angular signal, initially with attachment coefficient method of estimation based on longitudinal direction of car resonant frequency with based on steering The estimation real-time to attachment coefficient respectively of the attachment coefficient method of estimation of resonant frequency, then by the attachment of above two method Coefficient estimation value is separately sent to frequency domain fusion attachment coefficient estimation module and carries out fusion treatment, obtains the most accurate quick Attachment estimated value.Compared with existing road pavement attachment coefficient method of estimation, not only eliminate signal noise and error The impact that the attachment of information road pavement is estimated, and it also avoid the attachment estimation convergence that the dynamic deferred length of steering causes Slow defect.

Accompanying drawing explanation

Fig. 1 is the system architecture schematic diagram realizing the inventive method.

Detailed description of the invention

With embodiment, the present invention is described in detail below in conjunction with the accompanying drawings.

As it is shown in figure 1, the coefficient of road adhesion method of estimation of the present invention realizes based on a set of real-time estimating system, this is System includes a driving torque sensor 1 being arranged on driver for vehicle, and one is arranged on the wheel speed sensors at wheel 2, one is arranged on the steering wheel angle sensor 3 at steering column tube and steering assist motor 4, and is arranged on car load control In device processed one attachment coefficient based on longitudinal direction of car resonant frequency estimation module 5, is based on steering resonant frequency Attachment coefficient estimation module 6 and a frequency domain merge attachment estimation module 7.

Use the real-time estimating system of the present invention to the real-time estimation method of coefficient of road adhesion in vehicle travel process, bag Include following steps:

1, in vehicle operation, entire car controller controls driving torque sensor 1 in a certain sampling instant and will receive Real Time Drive torque T to vehicle_dThe wheel speed signal ω receiving vehicle with wheel speed sensors 2 is sent to indulge based on vehicle To the attachment coefficient estimation module 5 of resonant frequency；Defeated by attachment coefficient estimation module based on longitudinal direction of car resonant frequency Go out attachment coefficient estimated result based on longitudinal direction of car resonant frequency；

2, the real-time steering wheel rotational angular velocity of the vehicle recorded is believed by vehicle control unit controls steering wheel angle sensor 3 Number ω_sIt is separately sent to attachment coefficient based on steering resonant frequency with the power torque T of steering assist motor 4 estimate Meter module 6, is exported based on steering resonance frequency by attachment coefficient estimation module 6 based on steering resonant frequency The attachment coefficient estimated result of rate；

3, entire car controller is by attachment coefficient estimation module 5 based on longitudinal direction of car resonant frequency and based on steering system altogether Two kinds of attachment coefficient estimated results of attachment coefficient estimation module 6 output of vibration frequency are sent to frequency domain and merge attachment estimation Module 7；Merged attachment estimation module 7 by frequency domain and export final attachment coefficient estimated result, make for other controllers With.

Attachment coefficient estimation procedure based on longitudinal direction of car resonant frequency in above step 1 is:

1) real-time wheel speed signal ω and Real Time Drive torque T is obtained at entire car controller_dOn the basis of, utilize MATLAB Spectrum Analyzer (spectrum analyzer) module (a known software for calculation) in (matrix labotstory), Estimate longitudinal resonance frequencies f_0-x；

2) relation (formula (1)) being then based between attachment coefficient and longitudinal resonance frequencies, estimates attachment coefficient μ_max1:

$f_{0-x}=\frac{R}{2\mathrm{\π}}\sqrt{\frac{{\mathrm{a\μ}}_{max1}+b}{{\mathrm{Ir}}_x}}---\left(1\right)$

In formula, R is vehicle wheel roll radius, and I is vehicle wheel rotation inertia, r_xFor the longitudinal relaxation length of tire, it is logical Crossing the conventional method amount of would know that, a and b is two constants, is the empirical value determined according to test of many times matching, μ_max1 For the attachment coefficient to be asked.

Attachment coefficient estimation procedure based on steering resonant frequency in step 2 is:

1) real-time steering wheel rotational angular velocity signal ω is obtained at entire car controller_sPower-assisted with steering assist motor 4 On the basis of torque T, utilize the Spectrum Analyzer module in MATLAB, estimate steering resonant frequency f_0-y；

2) relation (formula (2)) being then based between attachment coefficient and steering resonant frequency, estimates attachment system Number μ_max2:

$f_{0-y}=\frac{1}{2{\mathrm{\πG}}_s}\sqrt{\frac{{\mathrm{c\μ}}_{max2}+d}{J_d}}---\left(2\right)$

G in formula_sFor steering gear ratio；J_dFor the rotary inertia of front-wheel and steering mechanism's equivalence to steering column, all For by the conventional method amount of would know that, c and d is two constants, and in like manner, c and d is true according to test of many times matching Fixed empirical value, μ_max2For the attachment coefficient to be asked.

The attachment coefficient estimation procedure merged based on frequency domain in step 3 is:

Frequency domain merges the attachment estimation module 7 two coefficient of road adhesion estimated values μ to receiving_max1And μ_max2Respectively It is filtered processing, merges and obtain the most accurately estimated value of coefficient of road adhesion in vehicle travel process

Owing to attachment coefficient method of estimation based on longitudinal direction of car resonant frequency is by the static deviation of wheel speed sensors and signal Influence of noise is bigger, it is impossible to obtain estimation difference at a stable estimated result, i.e. the method low frequency relatively big, but The longitudinal motion response of vehicle is quick, and the method can accurately perceive the dynamic change of road surface attachment condition, i.e. catches Arrive the high-frequency information of attachment coefficient；And contrary, attachment coefficient method of estimation based on steering resonant frequency due to Vehicular turn motion is relatively slow, causes the estimation time longer, but the method can reduce signal noise to estimated result Impact, i.e. can obtain relatively stable and that accuracy is high stable state estimated result.In view of two above estimated result The feature of mutual supplement with each other's advantages, the frequency domain of the present invention merges attachment coefficient estimation module 7 when road pavement attachment coefficient is estimated, To μ_max2Use low pass filter to filter its HFS, retain the relatively stable of its low frequency and the high stable state of accuracy is estimated Meter result；To μ_max1Use high pass filter to filter its low frequency part, retain its medium-high frequency dynamic-change information；Finally By the results added of two wave filter outputs, the real-time estimated value of the coefficient of road adhesion more accurately finally givenFor:

${\widehat{\mathrm{\μ}}}_{max}=\frac{1}{\mathrm{\τ}s+1}{\mathrm{\μ}}_{max2}+\frac{\mathrm{\τ}s}{\mathrm{\τ}s+1}{\mathrm{\μ}}_{max1}---\left(3\right)$

In formula, τ is time constant, is the empirical value obtained according to filtering situation by repeatedly simulation test, and s is for drawing General Laplacian operater,For low-pass filtering coefficient,For high-pass filtering coefficient.

What deserves to be explained is, the implementation of above-mentioned each process is not unique, for example with the Spectrum in MATLAB The resonant frequency that this method of Analyzer is estimated, it would however also be possible to employ any other mode is estimated, embodiment is only used for The bright present invention, step therein etc. all can be varied from, and every carries out on the basis of technical solution of the present invention Equivalents and improvement, the most should not get rid of outside protection scope of the present invention.

Claims (5)

1. the coefficient of road adhesion method of estimation merged based on frequency domain, it is characterised in that: it is by based on longitudinal direction of car Attachment coefficient estimated value μ that resonant frequency obtains_max1Estimate with the attachment coefficient obtained based on steering resonant frequency Value μ_max2, both are filtered processing, and merge based on frequency domain and obtain final attachment coefficient

The coefficient of road adhesion method of estimation merged based on frequency domain the most according to claim 1, it is characterised in that:

Attachment coefficient μ based on longitudinal direction of car resonant frequency_max1Estimation procedure is:

1) attachment coefficient estimation module based on longitudinal direction of car resonant frequency obtains wheel speed signal ω and Real Time Drive in real time Torque T_dOn the basis of, utilize the Spectrum Analyzer module in MATLAB software, estimate longitudinal resonance frequencies f_0-x；

2) attachment coefficient estimated value μ it is then based on_max1With longitudinal resonance frequencies f_0-xBetween relation, estimate attachment Coefficient estimation value μ_max1:

$f_{0-x}=\frac{R}{2\mathrm{\π}}\sqrt{\frac{{\mathrm{a\μ}}_{max1}+b}{{\mathrm{Ir}}_x}}---\left(1\right)$

In formula, R is vehicle wheel roll radius, and I is vehicle wheel rotation inertia, r_xFor the longitudinal relaxation length of tire, it is logical Crossing the conventional method amount of would know that, a and b is two constants, is the empirical value determined according to test of many times matching.

The coefficient of road adhesion method of estimation merged based on frequency domain the most according to claim 1, it is characterised in that:

Attachment coefficient μ based on steering resonant frequency_max2Estimation procedure is:

1) attachment coefficient estimation module based on steering resonant frequency obtains steering wheel rotational angular velocity signal in real time ω_sOn the basis of the power torque T of steering assist motor, utilize the Spectrum Analyzer in MATLAB software Module, estimates steering resonant frequency f_0-y；

2) attachment coefficient estimated value μ it is then based on_max2With steering resonant frequency f_0-yBetween relation, estimate Attachment coefficient estimated value μ_max2:

$f_{0-y}=\frac{1}{2{\mathrm{\πG}}_s}\sqrt{\frac{{\mathrm{c\μ}}_{max2}+d}{J_d}}---\left(2\right)$

G in formula_sFor steering gear ratio；J_dFor the rotary inertia of front-wheel and steering mechanism's equivalence to steering column, all For by the conventional method amount of would know that, c and d is two constants, is the empirical value determined according to test of many times matching.

4., according to the coefficient of road adhesion method of estimation merged based on frequency domain described in claim 1 or 2 or 3, it is special Levy and be:

The attachment coefficient merged based on frequency domainEstimation procedure is:

Frequency domain merges attachment estimation module attachment coefficient estimated value μ to obtaining based on longitudinal direction of car resonant frequency_max1With Attachment coefficient estimated value μ obtained based on steering resonant frequency_max2, it is filtered respectively processing, wherein to μ_max1 High pass filter is used to filter its low frequency part, reserved high-frequency part；To μ_max2Low pass filter is used to filter its high frequency Part, retains low frequency part；Then after filtering two, the result of output, utilizes following relational expression to obtain

${\widehat{\mathrm{\μ}}}_{max}=\frac{1}{\mathrm{\τ}s+1}{\mathrm{\μ}}_{max2}+\frac{\mathrm{\τ}s}{\mathrm{\τ}s+1}{\mathrm{\μ}}_{max1}---\left(3\right)$

In formula, τ is time constant, and s is Laplace operator,For low-pass filtering coefficient,Filter for high pass Wave system number.

5. according to the coefficient of road adhesion method of estimation merged based on frequency domain one of claim 1-4 Suo Shu, its feature It is: the described coefficient of road adhesion method of estimation merged based on frequency domain realizes based on a real-time estimating system, described system System includes:

The driving torque sensor that one is arranged on driver for vehicle, driving torque T of real-time reception vehicle_d；

One is arranged on the wheel speed sensors at wheel, the wheel speed signal ω of real-time reception vehicle；

One is arranged on the steering wheel angle sensor at steering column tube and steering assist motor, the direction of real-time reception vehicle Dish rotational angular velocity signal ω_sWith power torque T；

One attachment coefficient estimation module based on longitudinal direction of car resonant frequency, an attachment based on steering resonant frequency Coefficient estimation module and a frequency domain merge attachment estimation module, are all integrated in entire car controller, built-in MATLAB algorithm Program.