CN102530055A - Electric power steering system with double-gradient smooth assist curves - Google Patents

Abstract

The invention discloses an electric power steering system with double-gradient smooth assist curves, which is characterized in that an electronic control unit is provided with double-gradient smooth assist curves. By means of the double-gradient smooth power-assist curves, the electric power steering system has completely smooth assistance characteristics, and curve parameters can be independently calibrated according to different touch requirements of a small assistance area and a large assistance area. The electric power steering system has the advantages of smooth assistance, independent parameter function and easiness in adjustment, and expectations of drivers on steering touch can be better satisfied.

Description

Electric boosting steering system with the level and smooth power-assisted curve of diclinic rate

Technical field

The present invention relates to automobile electric booster steering system (Electric Power Steering is called for short EPS), particularly relate to a kind of electric boosting steering system with the level and smooth power-assisted curve of diclinic rate.

Background technology

Prior electric servo steering system (EPS) is to install torque sensor additional by traditional mechanical steering system (mainly comprising steering handwheel, steering shaft, deflector, steering track rod mechanism, wheel flutter), electronic control unit, and power steering motor and speed reduction gearing thereof are formed.Wherein, torque sensor is installed on the steering shaft to detect pilot control moment; Assist motor can be installed in steering shaft or the deflector, to chaufeur assist torque is provided through speed reduction gearing; Torque sensor signal and car speed sensor signal are input to the basic power operated control module of electronic control unit, calculate corresponding assist torque, as the target torque command of assist motor output.The assist torque size can be provided with different power-assisted curves by the software setting when the different speed of a motor vehicle, promptly can obtain the desirable feel that turns to.

The assist torque Ta size of EPS system outlet is relevant with the steering handwheel input torque size Ts of chaufeur input redirect dish, and its relation is through the decision of power-assisted curve.Therefore power-assisted curve as shown in Figure 1, can only discuss the part of first quartile generally with the initial point odd symmetry.Early stage power-assisted curve is single linear pattern, mainly describes (like Fig. 1) by rate of curve G (being the power-assisted gain) and power-assisted dead band L.Linear parameter of curve is simple, is easy to debugging.But chaufeur hopes under different moment inputs, to have different power-assisted levels usually in practical application.Such as when little moment (steering handwheel midway location) is imported, chaufeur hopes that power-assisted is less, obtains more to turn to feel; And when big moment was imported, chaufeur hoped that power-assisted is bigger, makes steering procedure lighter.This has just caused the appearance (as shown in Figure 2) of broken line type power-assisted curve.The broken line type curve has two or more slopes (G1, G2 ...), different power-assisted levels can be provided.But broken line type slope of a curve (curve first derivative) can sudden change occur at the intersection point place of two sections straight lines, brings driver-operated irregularity sense, and the slope of this force curve of will seeking help need seamlessly transit.Therefore, also there is the power-assisted curve of smooth type to be applied at present.As shown in Figure 3, all through the quadratic curve smooth connection, guaranteed to turn to the ride comfort of feel between the different straight line portioies of smooth type curve.Its first quadratic curve section also can be used as little power-assisted part and partly distinguishes with the big power-assisted of linear portion, obtains and broken line type curve similar effects.But the quadratic curve section should be taken into account the function of mild transition, as little power-assisted district different power-assisted levels is provided again, is difficult in like this and obtains desirable effect in the actual calibration process.

Summary of the invention

The technical matters that the present invention will solve provides a kind of electric boosting steering system with the level and smooth power-assisted curve of diclinic rate, to improve the assist characteristic of existing electric boosting steering system.This system has level and smooth assist characteristic fully, and can require parameter of curve is carried out independent demarcation based on the different feels in little power-assisted district and big power-assisted district, has the advantage that power-assisted is smooth-going, parameter function independent, be easy to debug.

For solving the problems of the technologies described above; Electric boosting steering system with the level and smooth power-assisted curve of diclinic rate of the present invention; Be on prior electric servo steering system basis; Through changing the completion that is provided with of power-assisted curve, the electric boosting steering system with the level and smooth power-assisted curve of diclinic rate promptly of the present invention is the electric boosting steering system that electronic control unit is provided with the level and smooth power-assisted curve of diclinic rate.

The level and smooth power-assisted curve of said diclinic rate is arranged at the basic power operated control module of electronic control unit.

Wherein, the level and smooth assist characteristic curve of diclinic rate is according to the different speed of a motor vehicle, and different power-assisted curves is set; And the third quadrant of the level and smooth assist characteristic curve of this diclinic rate and the curve odd symmetry of first quartile; The power-assisted curve of first quartile begins to be divided into successively 7 sections from initial point: dead section, first segment of curve, first linear portion, second segment of curve, second linear portion, the 3rd segment of curve, saturated section (because the curve odd symmetry of third quadrant and first quartile, the power-assisted curve segmentation of first quartile is as first quartile); Wherein, this power-assisted curve can all be realized through parametrization, make things convenient for staking-out work.

Beneficial effect of the present invention;

(1) but two linear portions of slope independent regulation can provide different power-assisted levels, help that overall balance is small to be turned to and the power-assisted demand of wide-angle between turning to;

(2) between dead section, first linear portion, second linear portion and saturated section, all there is quadratic curve to carry out transition, guaranteed that the power-assisted curve is level and smooth fully, and conversion is level and smooth when power-assisted is switched, and turns to feel smooth-going between varying level;

(3) because power-assisted curve of the present invention can all pass through parametrization; Therefore; Guaranteed that the demarcation personnel only need change correlation parameter, can realize the independent regulation of following target: power-assisted dead band size, the power-assisted level in each power-assisted district, the transition speed degree of each section quadratic curve etc.

Description of drawings

Below in conjunction with the accompanying drawing and the specific embodiment the present invention is done further detailed explanation:

Fig. 1 is a linear pattern power-assisted curve;

Fig. 2 is a broken line type power-assisted curve;

Fig. 3 is a smooth type power-assisted curve;

Fig. 4 is the control flow chart of system of the present invention;

Fig. 5 is the scheme drawing of the single curve first quartile of the level and smooth power-assisted curve of diclinic rate of the present invention;

Fig. 6 is the full vehicle speed range assist characteristic scheme drawing of the level and smooth power-assisted curve of diclinic rate of the present invention.

The specific embodiment

Electric boosting steering system with the level and smooth power-assisted curve of diclinic rate of the present invention is the electric boosting steering system that electronic control unit is provided with the level and smooth power-assisted curve of diclinic rate.

This electric boosting steering system comprises: mechanical steering system, torque sensor, electronic control unit, power steering motor and speed reduction gearing thereof.Wherein, said torque sensor is installed on the steering shaft of said mechanical steering system to detect pilot control moment; Electronic control unit calculates the driving current value that needs provide for the power steering motor according to current vehicles travel conditions and operating torque size; The power steering motor can be installed on the steering shaft or deflector of mechanical steering system, to chaufeur assist torque is provided through speed reduction gearing.The control flow chart of this system is as shown in Figure 4.

Above-mentioned electronic control unit comprises Torque Control module, current of electric control module and fault diagnosis module; The Torque Control module comprises basic power operated control module, initiatively returns the positive control module, damping control module.

Wherein, Basic power operated control module comprises one makes electric boosting steering system under any operating mode, all can obtain desired power steering performance; And can require according to the different feels in little power-assisted district and big power-assisted district the power-assisted parameter of curve is carried out independent demarcation, setting has the level and smooth assist characteristic curve of diclinic rate that power-assisted is smooth-going, parameter function independent, be easy to advantages such as debugging.

The level and smooth power-assisted curve of diclinic rate of the present invention is divided into 7 sections, wherein, and the power-assisted curve of first quartile, as shown in Figure 5:

The 1-dead section

2-first segment of curve

3-first linear portion

4-second segment of curve

5-second linear portion

6-the 3rd segment of curve

Saturated section of 7-

8 key parameters of every power-assisted curve negotiating are represented (as shown in table 1), change curve shape through adjusting these 8 key parameter values, thereby realize different power-assisted effects, make electric boosting steering system can obtain the best turning efficiency of chaufeur expectation.

The tabulation of table 1 power-assisted parameter of curve

Parameter	Meaning of parameters
		L 1	Dead band length
L 2	The first segment of curve length
		L 3	The first linear portion end point
L 4	The second segment of curve length
		L 5	The 3rd segment of curve initial point
G 1	First linear portion gain (slope)
		G 2	Second linear portion gain (slope)
H 1	Power-assisted curve maxim (saturation value)

The computing formula of 7 sections curves among Fig. 5 (only to first quartile, the curve odd symmetry of third quadrant and first quartile is so no longer repeat) is as follows:

As Ts≤L ₁The time, the power-assisted curve is in the 1st section-dead section:

T _a＝0(1)

Work as L ₁＜Ts≤L ₁+ L ₂The time, the power-assisted curve is in the 2nd section-first segment of curve:

$T_a=\frac{G_1{(T_s-L_1)}^2}{2L_2}---\left(2\right)$

Work as L ₁+ L ₂＜Ts≤L ₃The time, the power-assisted curve is in the 3rd section-first linear portion:

$T_a=G_1(T_s-L_1-L_2)+\frac{G_1{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}{2}---\left(3\right)$

Work as L ₃＜Ts≤L ₃+ L ₄The time, the power-assisted curve is in the 4th section-second segment of curve:

$T_a=\frac{(G_2-G_1){(T_s-L_3)}^2}{2{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}+G_1(T_s-L_1-L_2)+\frac{G_1{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}{2}---\left(4\right)$

Work as L ₃+ L ₄＜Ts≤L ₅The time, the power-assisted curve is in the 5th section-second linear portion:

$T_a=G_2(T_s-L_3-L_4)+\frac{({\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_1+G_2){\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}{2}---\left(5\right)$

The derivation of equation of the 6th section the-the 3rd segment of curve need be introduced auxiliary parameter-Di three segment of curve height H ₂(the 3rd section curve is from initial point L ₅Height to end point).Can learn the 5th section and the 6th section intersection point, i.e. Ts=L according to the restriction relation between the curve ₅The power-assisted Ta size at place:

$T_a{|}_{T_s={\mathrm{<figure-callout\; id="5"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_5}=G_2(L_5-L_3-L_4)+\frac{({\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_1+G_2){\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}{2}---\left(6\right)$

And at the 6th section end point T _a=H ₁, can get thus:

$H_2=H_1-G_2(L_5-L_3-L_4)-\frac{({\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_1+G_2){\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}{2}---\left(7\right)$

It should be noted that auxiliary parameter H ₂Must be greater than 0, that is:

$H_2=H_1-G_2(L_5-L_3-L_4)-\frac{({\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_1+G_2){\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}{2}>0$

$\&RightArrow;{\mathrm{<figure-callout\; id="5"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_5<\frac{1}{G_2}[H_1-\frac{({\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_1+G_2){\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}{2}]+{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_3+L_4---\left(8\right)$

In the formula (8) to L ₅Constraint must when parameter calibration, confirm.

If the 6th section formula is:

T _a＝k(T _s-a) ²+b (9)

Then:

$a={\mathrm{<figure-callout\; id="5"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_5+\frac{2H_2}{G_2}---\left(10\right)$

b＝H ₁ (11)

$k=-\frac{{{\mathrm{<figure-callout\; id="2"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_2}^2}{{4H}_2}---\left(12\right)$

Wherein a is the 6th section a end point, promptly works as L ₅During＜Ts≤a, the power-assisted curve is in the 6th section:

$T_a=-\frac{{{\mathrm{<figure-callout\; id="2"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_2}^2}{4H_2}{[T_s-({\mathrm{<figure-callout\; id="5"\; label="L"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_5+\frac{{2H}_2}{G_2})]}^2+H_1---\left(13\right)$

When Ts＞a, the power-assisted curve is in the 7th section-saturated section:

T _a＝H ₁ (14)

Should calculate the absolute value abs (Ts) of Ts during actual computation earlier, calculate the absolute value abs (Ta) of Ta then according to formula (1)～(14).The absolute value that final Ta equals Ta multiply by the symbol of Ts, i.e. Ta=abs (Ta) * sign (Ts).

After designing wall scroll power-assisted curve according to said method, the EPS system also needs according to speed of a motor vehicle size different power-assisted curves is provided.In order to realize this target; At first need in full vehicle speed range, choose several speed of a motor vehicle points (like Okm/h, 20km/h, 40km/h ...) as the benchmark speed of a motor vehicle; According to real vehicle debugging and demarcation, the corresponding power-assisted parameter of curve of designing corresponding each benchmark speed of a motor vehicle point is as the assist characteristic curve under the benchmark speed of a motor vehicle then.

Wherein, the power-assisted curve of different speed of a motor vehicle points is realized based on following method in the full vehicle speed range:

(1) when actual vehicle speed just in time equals certain benchmark speed of a motor vehicle point, system of the present invention provides power-assisted according to the corresponding power-assisted curve of this benchmark speed of a motor vehicle;

(2) when actual vehicle speed is between two benchmark speed of a motor vehicle points, assist torque calculates according to the power-assisted parameter of curve then according to the power-assisted parameter of curve of approach based on linear interpolation (shown in formula 15) when calculating this actual vehicle speed in system.

For example hypothesis has two groups of parameters of corresponding 20km/h, the 40km/h speed of a motor vehicle now, when actual vehicle speed v=23km/h, and the first linear portion slope G1 of the actual employing of system:

${\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_1=\frac{40-23}{20}{\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_{1\_20}+\frac{23-20}{20}{\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="HDA0000039852740000031.png"\; state="\{\{state\}\}">G</figure-callout>}}_{1\_40}---\left(15\right)$

Wherein G1_20 is the cooresponding G1 of 20km/h, and G1_40 is the cooresponding G1 of 40km/h.

Assist characteristic in that the introducing speed of a motor vehicle obtains later on is as shown in Figure 6.Can be found out that by Fig. 6 when the speed of a motor vehicle was low, the assist torque that system provides under the identical steering handwheel input torque was bigger, the chaufeur turning rate is lighter; Otherwise when the speed of a motor vehicle was higher, assist torque was less, and it is more sedate to drive.

Because chaufeur hopes under different moment inputs, to have different power-assisted levels.Such as when little moment (steering handwheel midway location) is imported, chaufeur hopes that power-assisted is less, obtains more steering feel; And when big moment was imported, chaufeur hoped that power-assisted is bigger, makes steering procedure lighter.And through adopting the present invention, turn under the level and smooth prerequisite of feel guaranteeing, independent two sections adjustable power-assisted districts also are provided, can satisfy chaufeur better in the expectation that turns to aspect the feel.

Claims (7)

1. electric boosting steering system with the level and smooth power-assisted curve of diclinic rate, it is characterized in that: said electric boosting steering system is the electric boosting steering system that electronic control unit is provided with the level and smooth power-assisted curve of diclinic rate.

2. the electric boosting steering system with the level and smooth power-assisted curve of diclinic rate as claimed in claim 1 is characterized in that: the level and smooth power-assisted curve of said diclinic rate is arranged at the basic power operated control module of electronic control unit.

3. the electric boosting steering system with the level and smooth power-assisted curve of diclinic rate as claimed in claim 1 is characterized in that: said electric boosting steering system comprises the mechanical steering system, torque sensor, electronic control unit, power steering motor and speed reduction gearing thereof;

Wherein, torque sensor is installed on the steering shaft of mechanical steering system, to detect pilot control moment; Electronic control unit calculates the driving current value that needs provide for the power steering motor according to current vehicles travel conditions and operating torque size; The power steering motor is installed on the steering shaft or deflector of mechanical steering system, to chaufeur assist torque is provided through speed reduction gearing.

4. the electric boosting steering system with the level and smooth power-assisted curve of diclinic rate as claimed in claim 1 is characterized in that: the level and smooth power-assisted curve of said diclinic rate is according to the different speed of a motor vehicle, and different power-assisted curves is set;

The third quadrant of the level and smooth power-assisted curve of this diclinic rate and the curve odd symmetry of first quartile, the power-assisted curve of first quartile begins to be divided into successively 7 sections from initial point: dead section, first segment of curve, first linear portion, second segment of curve, second linear portion, the 3rd segment of curve, saturated section; Wherein, this power-assisted curve is all realized through parametrization.

5. the electric boosting steering system with the level and smooth power-assisted curve of diclinic rate as claimed in claim 4 is characterized in that: the parameter of the level and smooth power-assisted curve of said diclinic rate is: the dead band length L ₁, the first segment of curve length L ₂, the first linear portion end point L ₃, the second segment of curve length L ₄, the 3rd segment of curve initial point L ₅, the first linear portion slope G ₁, the second linear portion slope G ₂, power-assisted curve maxim H ₁, the 3rd segment of curve height H ₂, the 3rd segment of curve end point a;

The assist torque Ta computing formula of 7 sections power-assisted curves is following:

As Ts≤L ₁The time, the power-assisted curve is in dead section:

T _a＝0

Work as L ₁＜Ts≤L ₁+ L ₂The time, the power-assisted curve is in first segment of curve:

$T_a=\frac{G_1{(T_s-L_1)}^2}{2L_2}$

Work as L ₁+ L ₂＜Ts≤L ₃The time, the power-assisted curve is in first linear portion:

$T_a=G_1(T_s-L_1-L_2)+\frac{G_1{L}_2}{2}$

Work as L ₃＜Ts≤L ₃+ L ₄The time, the power-assisted curve is in second segment of curve:

$T_a=\frac{(G_2-G_1){(T_s-L_3)}^2}{2L_4}+G_1(T_s-L_1-L_2)+\frac{G_1{L}_2}{2}$

Work as L ₃+ L ₄＜Ts≤L ₅The time, the power-assisted curve is in second linear portion:

$T_a=G_2(T_s-L_3-L_4)+\frac{(G_1+G_2)L_4}{2}$

Work as L ₅During＜Ts≤a, the power-assisted curve is in the 3rd segment of curve:

$T_a=-\frac{{G_2}^2}{4H_2}{[T_s-(L_5+\frac{{2H}_2}{G_2})]}^2+H_1$

When Ts＞a, the power-assisted curve is in saturated section:

T _a＝H ₁

Wherein, Ts is a steering handwheel input torque size.

6. the electric boosting steering system with the level and smooth power-assisted curve of diclinic rate as claimed in claim 5; It is characterized in that: in the said Ta computing formula; When actual computation, calculate the absolute value abs (Ts) of Ts earlier, and then utilize computing formula to calculate the absolute value abs (Ta) of Ta; The absolute value that final Ta equals Ta multiply by the symbol of Ts, Ta=abs (Ta) * sign (Ts).

7. the electric boosting steering system with the level and smooth power-assisted curve of diclinic rate as claimed in claim 4 is characterized in that: the level and smooth power-assisted curve of said diclinic rate, and under the different speed of a motor vehicle, the method that different power-assisted curves are set is following:

At first in full vehicle speed range, choose several speed of a motor vehicle points as the benchmark speed of a motor vehicle, according to real vehicle debugging and demarcation, the cooresponding power-assisted parameter of curve of designing corresponding each benchmark speed of a motor vehicle point is as the assist characteristic curve under the benchmark speed of a motor vehicle then;

Wherein, the power-assisted curve of different speed of a motor vehicle points is realized according to following method in the full vehicle speed range;

1) when actual vehicle speed just in time equals certain benchmark speed of a motor vehicle point, power-assisted is provided according to the corresponding power-assisted curve of this benchmark speed of a motor vehicle;

2) when actual vehicle speed is between two benchmark speed of a motor vehicle points, the power-assisted parameter of curve when calculating this actual vehicle speed according to approach based on linear interpolation is calculated assist torque according to the power-assisted parameter of curve then.

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