CN104494577A - Brake-by-wire system pedal force estimation and control method - Google Patents

Abstract

Disclosed is a brake-by-wire system pedal force estimation and control method. The brake-by-wire system pedal force estimation and control method comprises the following steps that initialization is conducted; pressure P1 is collected; displacement x is collected; filtering is conducted on the x; a differential term of the x is calculated; pedal force F is calculated. The brake-by-wire system pedal force estimation and control method achieves estimation of the pedal force under the condition that only a displacement sensor and a main cylinder pressure sensor are arranged, and therefore dynamic pedal force control can be achieved in a control process, and a more comfortable pedal feeling is obtained; pedal feedback force is calculated in real time through a system dynamics model in a dynamic process; inequality of pressure of two cavities of a main cylinder is taken into consideration through a hydraulic model in the dynamic process; a pedal feedback force control item is added in the control process, and a dynamic pedal feeling is optimized.

Description

A kind of line control brake system treadle effort estimation and control method

Technical field

The invention belongs to automotive field, be specifically related to the estimation of a kind of line control brake system treadle effort and control method.

Background technology

In Automotive Electronics Parking Brake System of the prior art, due to cannot the actual value of perception treadle effort, so only control master cylinder pressure, brake system treadle effort do not estimated or control.

Although in the design of current WBS line control brake system, master cylinder pressure and treadle effort under quiescent conditions, can be considered as meeting the proportionate relationship determined by master cylinder two sides product moment; But in dynamic pressure control process, treadle effort is also relevant with pedal speed, master cylinder pressure at both sides difference.This causes in existing control method, and dynamic pedal power there will be abnormal human discomfort, comprises the problems such as top strength of one's legs is excessively strong, the weak or pedal shake of mistake.

Summary of the invention

The object of the invention is to solve treadle effort estimation problem when only having displacement pickup and master cylinder pressure sensor, thus the control of dynamic pedal power can be realized in the controlling, obtain more comfortable pedal sense.

The technical solution used in the present invention is: a kind of line control brake system treadle effort estimation and control method,

Comprise the following steps:

S1, initialization;

S2, gathers pressure P 1;

S3, gathers displacement x;

S4, carries out filtering to x;

S5, calculates the differential term of x;

S6, calculates treadle effort F.

Further, in described step S6, treadle effort F computing formula is:

F＝F _z+ΔP/i

Wherein F _zact on the power on plunger for brake pedal, Δ P is pressure reduction, and i is the transmitting ratio of pedal.

Further, described brake pedal acts on the power F on plunger _zcomputing formula is:

$F_z=P_1{S}_1-P_2{S}_2+m\stackrel{\·\·}{x}+c\stackrel{\·}{x}$

Wherein, P ₁, P ₂for left and right sides pressure, S ₁, S2 be left and right sides pressure application surface amass, m is heavy moving parts, and c is viscous damping coefficient, and x is pedal displacement.

Further, described pressure differential deltap P computing formula is:

$\mathrm{\ΔP}=\frac{\mathrm{\ρ}}{2}{\left(\frac{q}{c_{d}A}\right)}^2\mathrm{Sgn}(q>0)$

Wherein, ρ is braking liquid density, and q is joint mouth flow, c _dfor valve port flow coefficient, A is open area, and symbolic function Sgn (q > 0) is that check valve causes.

Further, described joint mouth flow q computing formula is:

$q=S_2\stackrel{\·}{x}.$

Further, described treadle effort F is specially:

$F=\frac{m\stackrel{\·\·}{x}}{i}+\frac{\mathrm{\ρ}{S}_2}{2i}{\left(\frac{s_2\stackrel{\·}{x}}{c_{d}A}\right)}^2\mathrm{Sgn}(\stackrel{\·}{x}>0)+\frac{c}{i}\stackrel{\·}{x}+\frac{P_1(S_1-S_2)}{i}.$

Further, described treadle effort F computing formula, in the static case,

$F=\frac{m\stackrel{\·\·}{x}}{i}+\frac{\mathrm{\ρ}{S}_2}{2i}{\left(\frac{s_2\stackrel{\·}{x}}{c_{d}A}\right)}^2\mathrm{Sgn}(\stackrel{\·}{x}>0)+\frac{c}{i}\stackrel{\·}{x}+\frac{P_1(S_1-S_2)}{i}$ Be reduced to:

$F=\frac{P_1(S_1-S_2)}{i};$

The two is fixed proportion relation, and now, treadle effort control objectives is consistent with Stress control target.

Further, described line control brake system treadle effort estimation and control method, also comprise master control

The calculating of amount processed, the computing formula of described overhead control amount is:

u＝u _p(1-α)+u _Fα

Wherein, u _pfor Stress control amount, u _ffor controlling quantity, α is treadle effort control weight, meets 0 < α < 1, in dynamic adjustment process, according to Actual Control Effect of Strong adjustment α, to realize rational dynamic pressure and treadle effort.

Further, described controlling quantity u _ffor to deviation e _fadoption rate differential regulates, that is:

$u_F=K_p[e_F+T_d\frac{{\mathrm{de}}_F}{\mathrm{dt}}].$

Further, described deviation e _ffor:

e _F＝F-F ₀

Wherein, F is treadle effort, F ₀for target treadle effort during different pedal displacement.

Advantage of the present invention:

The invention solves treadle effort estimation problem when only having displacement pickup and master cylinder pressure sensor, thus the control of dynamic pedal power can be realized in the controlling, obtain more comfortable pedal sense.

The present invention, by system dynamics model, calculates pedal feedback force in real time in dynamic process; The present invention passes through fluid-percussion model of isolated, in dynamic process, and the master cylinder two cavity pressure inequality of consideration; The present invention, in control process, adds pedal feedback force control item, optimizes dynamic pedal sensation.

Except object described above, feature and advantage, the present invention also has other object, feature and advantage.Below with reference to figure, the present invention is further detailed explanation.

Accompanying drawing explanation

The accompanying drawing forming a application's part is used to provide a further understanding of the present invention, and schematic description and description of the present invention, for explaining the present invention, does not form inappropriate limitation of the present invention.

This method mainly uses pedal displacement and master cylinder forefront pressure two parameters, and main innovate point is to introduce clear and definite brake pedal force control object, because brake pedal force does not have actual sensor to gather this data, needs to estimate this parameter.As previously mentioned, estimation equation considers the factor such as difference of pressure, phylogenetic relationship, system damping of master brake cylinder front and back end.Because pedal displacement signal jitter is comparatively large, and in actual computation process, also use the difference of displacement signal, therefore need the filtering processing pedal displacement, have employed FIR filter herein, and by Matlab software, this filter is designed; For the filtering of pressure signal, then smothing filtering is directly adopted to meet the demands.After data processing completes, adopt formula $F=\frac{m\stackrel{\&CenterDot;\&CenterDot;}{x}}{i}+\frac{\mathrm{\&rho;}{S}_2}{\mathrm{zi}}{\left(\frac{s_2\stackrel{\&CenterDot;}{x}}{c_{d}A}\right)}^2\mathrm{Sgn}(\stackrel{\&CenterDot;}{x}>0)+\frac{c}{i}\stackrel{\&CenterDot;}{x}+\frac{P_1(S_1-S_2)}{i}.$

Brake pedal force can be calculated.

Fig. 1 is a kind of line control brake system treadle effort estimation of the present invention and control method diagram of circuit.

Detailed description of the invention

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

Fig. 1 shows a kind of line control brake system treadle effort estimation of the present invention and control method diagram of circuit.

With reference to figure 1, a kind of line control brake system treadle effort estimation as shown in Figure 1 and control method,

Comprise the following steps:

S1, initialization;

S2, gathers pressure P 1;

S3, gathers displacement x;

S4, carries out filtering to x;

S5, calculates the differential term of x;

S6, calculates treadle effort F.

Equilibrium equation:

Main consideration hydraulic coupling and pedal equilibrium of forces, in dynamic process, consider the impact of movable parts inertia and viscosity damping, the equilibrium equation of plunger is simultaneously:

$F_z=P_1{S}_1-P_2{S}_2+m\stackrel{\&CenterDot;\&CenterDot;}{x}+c\stackrel{\&CenterDot;}{x}$

In formula, F _zthe power on plunger is acted on, P for brake pedal ₁, P ₂for left and right sides pressure, S ₁, S ₂for left and right sides pressure application surface amasss, m is heavy moving parts, and c is viscous damping coefficient, and x is pedal displacement.

If the transmitting ratio of brake pedal is i, then treadle effort is:

F＝F _z/i

Restriction flow characteristic:

Left and right sides difference of pressure mainly produces due to the Pressure Drop of restriction, can be expressed as:

$\mathrm{\&Delta;P}=\frac{\mathrm{\&rho;}}{2}{\left(\frac{q}{c_{d}A}\right)}^2\mathrm{Sgn}(q>0)$

In formula, Δ P is pressure reduction, i.e. Δ P=P ₁-P ₂, ρ is braking liquid density, and q is flow, c _dfor valve port flow coefficient, A is open area, and symbolic function Sgn (q > 0) is that check valve causes.

Restriction flow:

Restriction flow can be expressed as:

$q=S_2\stackrel{\&CenterDot;}{x}$

The calculating of treadle effort:

By above-mentioned various, can treadle effort be obtained:

$F=\frac{m\stackrel{\&CenterDot;\&CenterDot;}{x}}{i}+\frac{\mathrm{\&rho;}{S}_2}{2i}{\left(\frac{s_2\stackrel{\&CenterDot;}{x}}{c_{d}A}\right)}^2\mathrm{Sgn}(\stackrel{\&CenterDot;}{x}>0)+\frac{c}{i}\stackrel{\&CenterDot;}{x}+\frac{P_1(S_1-S_2)}{i}$

Treadle effort controls:

Target treadle effort according to general brake system pedal feedback force as a reference, adopt similar parabolical curve.

Data in accompanying drawing are deposited the code space of WBS software, and target treadle effort F when using lookup table mode to obtain different pedal displacement ₀.

Then deviation is:

e _F＝F-F ₀

To e _fadoption rate differential regulates, and can realize treadle effort and control, be i.e. controlling quantity

$u_F=K_p[e_F+T_d\frac{{\mathrm{de}}_F}{\mathrm{dt}}]$

The calculating of overhead control amount:

In original design, calculate Stress control amount u according to goal pressure _p, total controlling quantity has the two weighting process.

u＝u _p(1-α)+u _Fα

In formula, α is treadle effort control weight, meets 0 < α < 1, in dynamic adjustment process, according to Actual Control Effect of Strong adjustment α, to realize rational dynamic pressure and treadle effort.

For quiescent conditions, have therefore, formula

$F=\frac{m\stackrel{\&CenterDot;\&CenterDot;}{x}}{i}+\frac{\mathrm{\&rho;}{S}_2}{2i}{\left(\frac{s_2\stackrel{\&CenterDot;}{x}}{c_{d}A}\right)}^2\mathrm{Sgn}(\stackrel{\&CenterDot;}{x}>0)+\frac{c}{i}\stackrel{\&CenterDot;}{x}+\frac{P_1(S_1-S_2)}{i}$ To be reduced to:

the two is fixed proportion relation, and now, treadle effort control objectives is consistent with Stress control target, and the object that this also illustrates the treadle effort control policy of this patent feels in order to the treadle effort improved in dynamic process.The invention solves treadle effort estimation problem when only having displacement pickup and master cylinder pressure sensor, thus the control of dynamic pedal power can be realized in the controlling, obtain more comfortable pedal sense.

The present invention, by system dynamics model, calculates pedal feedback force in real time in dynamic process; The present invention passes through fluid-percussion model of isolated, in dynamic process, and the master cylinder two cavity pressure inequality of consideration; The present invention, in control process, adds pedal feedback force control item, optimizes dynamic pedal sensation.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (10)

1. the estimation of line control brake system treadle effort and a control method, is characterized in that, comprise the following steps:

S1, initialization;

S2, gathers pressure P 1;

S3, gathers displacement x;

S4, carries out filtering to x;

S5, calculates the differential term of x;

S6, calculates treadle effort F.

2. line control brake system treadle effort estimation according to claim 1 and control method, it is characterized in that, in described step S6, treadle effort F computing formula is:

F＝F _z+ΔP/i

Wherein F _zact on the power on plunger for brake pedal, Δ P is pressure reduction, and i is the transmitting ratio of pedal.

3. line control brake system treadle effort estimation according to claim 2 and control method, it is characterized in that, described brake pedal acts on the power F on plunger _zcomputing formula is:

$F_z=P_1{S}_1-P_2{S}_2+m\stackrel{..}{x}+c\stackrel{.}{x}$

Wherein, P ₁, P ₂for left and right sides pressure, S ₁, S ₂for left and right sides pressure application surface amasss, m is heavy moving parts, and c is viscous damping coefficient, and x is pedal displacement.

4. line control brake system treadle effort estimation according to claim 2 and control method, it is characterized in that, described pressure differential deltap P computing formula is:

$\mathrm{\&Delta;P}=\frac{\mathrm{\&rho;}}{2}{\left(\frac{q}{c_{d}A}\right)}^2\mathrm{Sgn}(q>0)$

Wherein, ρ is braking liquid density, and q is joint mouth flow, c _dfor valve port flow coefficient, A is open area, and symbolic function Sgn (q > 0) is that check valve causes.

5. line control brake system treadle effort estimation according to claim 4 and control method, it is characterized in that, described joint mouth flow q computing formula is:

$q=S_2\stackrel{.}{x}.$

6. line control brake system treadle effort estimation according to claim 2 and control method, it is characterized in that, described treadle effort is specially:

$F=\frac{m\stackrel{..}{x}}{i}+\frac{\mathrm{\&rho;}{S}_2}{2i}{\left(\frac{s_2\stackrel{.}{x}}{c_{d}A}\right)}^2\mathrm{Sgn}(\stackrel{.}{x}>0)+\frac{c}{i}\stackrel{.}{x}+\frac{P_1(S_1-S_2)}{i}.$

7. line control brake system treadle effort estimation according to claim 2 and control method, is characterized in that, described treadle effort F computing formula, in the static case,

$F=\frac{m\stackrel{..}{x}}{i}+\frac{\mathrm{\&rho;}{S}_2}{2i}{\left(\frac{s_2\stackrel{.}{x}}{c_{d}A}\right)}^2\mathrm{Sgn}(\stackrel{.}{x}>0)+\frac{c}{i}\stackrel{.}{x}+\frac{P_1(S_1-S_2)}{i}$ Be reduced to:

$F=\frac{P_1(S_1-S_2)}{i};$

The two is fixed proportion relation, and now, treadle effort control objectives is consistent with Stress control target.

8. line control brake system treadle effort estimation according to claim 1 and control method, it is characterized in that, also comprise the calculating of overhead control amount, the computing formula of described overhead control amount is:

u＝u _P(1-α)+u _Fα

Wherein, u _pfor Stress control amount, u _ffor controlling quantity, α is treadle effort control weight, meets 0 < α < 1, in dynamic adjustment process, according to Actual Control Effect of Strong adjustment α, to realize rational dynamic pressure and treadle effort.

9. line control brake system treadle effort estimation according to claim 8 and control method, is characterized in that, described controlling quantity u _ffor to deviation e _fadoption rate differential regulates, that is:

$u_F=K_p[e_F+T_d\frac{{\mathrm{de}}_F}{\mathrm{dt}}].$

10. line control brake system treadle effort estimation according to claim 9 and control method, is characterized in that, described deviation e _ffor:

e _F＝F-F ₀

Wherein, F is treadle effort, F ₀for target treadle effort during different pedal displacement.