DE102015219554B4 - Method and control device for determining a braking force or a variable corresponding to the braking force - Google Patents

Abstract

Method for determining a braking force or a variable of a motor vehicle corresponding to the braking force, with the following steps: a first gradient of the motor vehicle or a first variable corresponding to the first gradient is determined from a calculation model of a motor vehicle; a second variable is determined depending on a measured value of an acceleration sensor of the motor vehicle The gradient of the motor vehicle or a second variable corresponding to the second gradient is determined; a difference between the first gradient and the second gradient or between the first variable and the second variable is determined; depending on this difference between the first gradient and the second gradient or between the braking force or the variable corresponding to the braking force is determined from the first variable and the second variable.

Description

The invention relates to a method for determining a braking force or a variable corresponding to the braking force. The invention also relates to a control device for determining a braking force or a variable corresponding to the braking force.

In order to be able to precisely control or regulate the operation of a motor vehicle, it is important to precisely determine the braking force or a variable corresponding to the braking force during operation.

From the DE 103 15 889 B4 a method for increasing the quality of a braking force estimate is known. According to this method, a correction value for the estimated braking force value is determined during braking as a function of forces acting on the motor vehicle, an original estimated braking force value being corrected with the correction value. The correction value is determined with the aid of an equilibrium of forces in the longitudinal direction of the vehicle from a driving force, driving resistance forces counteracting the driving force and a current estimated braking force value.

There is a need to determine the braking force or a variable corresponding to the braking force more simply and more precisely.

Proceeding from this, the invention is based on the object of creating a novel method for determining a braking force or a variable of a motor vehicle corresponding to the braking force and a control device for determining a braking force or a variable of a motor vehicle corresponding to the braking force.

This object is achieved by a method for determining a braking force or a variable of a motor vehicle that corresponds to the braking force.

According to the invention, a first gradient of the motor vehicle or a first variable corresponding to the first gradient is determined from a computation model of a motor vehicle; Depending on a measured value of an acceleration sensor of the motor vehicle, a second gradient of the motor vehicle or a second variable corresponding to the second gradient is determined; Furthermore, a difference between the first slope and the second slope or between the first variable and the second variable is determined; The braking force or the variable corresponding to the braking force is determined as a function of this difference between the first slope and the second slope or between the first variable and the second variable.

The invention allows a simple and precise determination of a braking force or a variable corresponding to the braking force. For this purpose, gradient values are determined in two different ways, namely on the one hand based on a calculation model of the motor vehicle and on the other hand based on a measured value from an acceleration sensor of the motor vehicle, the difference between the determined gradient values being used to assign the braking force or the variable corresponding to the braking force determine.

The first gradient of the motor vehicle or the first variable corresponding to the first gradient is preferably calculated from an acceleration model of the motor vehicle. In this way, the first slope value can be determined particularly advantageously.

The braking force or the variable corresponding to the braking force is preferably only determined when the motor vehicle is being driven straight ahead and / or when the drive wheels of the motor vehicle are free of slip and / or when the drive wheels of the motor vehicle are unblocked and / or when a mass of the motor vehicle is valid or is validly known and / or if a speed of the motor vehicle is greater than a limit value and / or if an anti-lock braking system of the motor vehicle is inactive and / or if a primary brake of the motor vehicle is active and / or a secondary brake of the motor vehicle is active during braking of the motor vehicle is inactive.

Only when preferably all of the above conditions are cumulatively met is the braking force or the variable corresponding to the braking force determined with the aid of the method according to the invention.

The control device according to the invention for determining a braking force or a variable corresponding to the braking force is defined in claim 7.

• 1 eine Antriebstrangschema eines Kraftfahrzeugs; und
• 2 ein Signalflussdiagramm zur Verdeutlichung des erfindungsgemäßen Verfahrens zur Bestimmung einer Bremskraft oder einer der Bremskraft entsprechenden Größe.

Preferred developments emerge from the subclaims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being restricted thereto. It shows:

• 1 a powertrain diagram of a motor vehicle; and
• 2 a signal flow diagram to illustrate the method according to the invention for determining a braking force or a variable corresponding to the braking force.

The invention relates to a method and a control device for determining a braking force of a motor vehicle or a variable corresponding to the braking force.

1 shows a powertrain scheme 1 of a motor vehicle, which is a drive unit 2 , a transmission 3 and a downforce 4th includes. The gear 3 is between the drive unit 2 and the downforce 4th switched. The gear 3 converts speeds and torques and thus sets the tractive power of the drive unit 2 at the output 4th ready.

The operation of the drive unit 2 is controlled by an engine control device 5 and the operation of the transmission 3 from a transmission control device 6th controlled and / or regulated. To do this, the engine control unit swaps 5 with the drive unit 2 and the transmission control unit 6th with the gearbox 3 Data from. Furthermore, replace the engine control unit 5 and the transmission control unit 6th data from each other.

Also shows 1 an accelerometer 7th of the motor vehicle. The accelerometer 7th provides a measured value of the longitudinal acceleration of the motor vehicle to the transmission control unit 6th to disposal.

In order to determine a braking force or a variable corresponding to the braking force during operation during a braking process of the motor vehicle, the control unit 6th a first gradient of the motor vehicle or a first gradient of a roadway on which the motor vehicle is traveling or a first variable corresponding to this first gradient is determined from a computation model of the motor vehicle.

Furthermore, preferably from the transmission control unit 6th depending on a measured value from the acceleration sensor 7th of the motor vehicle, a second gradient of the motor vehicle or a second gradient of the roadway of the motor vehicle or a second variable corresponding to the second gradient is determined.

Subsequently, a difference between the first slope and the second slope or between the first variable and the second variable is determined, the braking force or that of the braking force depending on this difference between the first slope and the second slope or between the first variable and the second variable Braking force corresponding size is determined, preferably in turn by the transmission control unit 6th .

Details of the method according to the invention, which is preferably carried out by the transmission control unit 6th are carried out below with reference to the flowchart 8th the 2 described.

In one step 9 During the process, the corresponding function of the transmission control device is called up on the control side 6th as well as an initialization.

The following are in one step 10 Conditions checked, which preferably all must be met cumulatively together so that the braking force or the variable corresponding to the braking force is determined in the sense of the present invention.

So is preferably done in step 10 checks whether the vehicle is being driven straight ahead during braking and whether there are drive wheels at the output during braking 4th of the motor vehicle are slip-free and / or whether the drive wheels of the motor vehicle are unblocked during the braking process and / or whether the mass of the motor vehicle is valid or valid with sufficient accuracy during the braking process and / or whether a speed of the motor vehicle is greater than is a limit value and / or whether an anti-lock braking system of the motor vehicle is inactive during the braking process and / or whether a primary brake of the motor vehicle is active and / or a secondary brake of the motor vehicle is inactive during the braking process. The primary brake of the motor vehicle is a foot brake. The secondary brake of the motor vehicle is any other braking function, for example an engine brake of the motor vehicle. Only if in step 10 it is established that all of these conditions are cumulatively met during the braking process, starting from step 10 on step 11 branched and the braking force or determines the size corresponding to the braking force. Then, however, if at least one of the conditions of the step 10 is not fulfilled, is in the sense of a loop on step 10 branched back.

In step 11 the determination of the braking force or the variable corresponding to the braking force takes place on the basis of the above-mentioned difference between the first slope and the second slope or on the basis of the difference between the first variable, which corresponds to the first slope, and the second variable, which is the second variable corresponds to.

This is done in step 12th the first gradient of the motor vehicle or the first variable corresponding to the first gradient is determined on the basis of a computation model of the motor vehicle, preferably on the basis of an acceleration model, namely a longitudinal acceleration model, of the motor vehicle.

wobei

• m die Masse des Kraftfahrzeugs ist,
• ν̇_FZG die Längsbeschleunigung des Kraftfahrzeugs ist,
• f_AN die Antriebskraft des Kraftfahrzeugs ist,
• f_R der Rollwiderstand des Kraftfahrzeugs ist,
• f_L der Luftwiderstand des Kraftfahrzeugs ist,
• g die Erdbeschleunigung ist,
• α1 die erste Steigung des Kraftfahrzeugs ist.

The first slope of the motor vehicle or the first variable corresponding to the first slope is preferably calculated according to the following equation: $$m\times {\dot{\nu }}_{\mathrm{F.}ZG}=f_{\mathrm{A.}N}-m\times G\times sin\left(\alpha 1\right)-f_{\mathrm{R.}}-f_{\mathrm{L.}}$$

in which

• m is the mass of the motor vehicle,
• ν̇ _{FZG is} the longitudinal acceleration of the motor vehicle,
• f _{AN is} the driving force of the motor vehicle,
• f _{R is} the rolling resistance of the motor vehicle,
• f _{L is} the air resistance of the motor vehicle,
• g is the acceleration due to gravity,
• α1 is the first slope of the motor vehicle.

In the above equation for determining the first gradient of the motor vehicle or the first variable corresponding to the first gradient, braking forces are specifically not taken into account. The longitudinal acceleration of the motor vehicle is preferably determined from a speed of the motor vehicle, which is known on the control side, with the aid of a derivation filter. The drive force is also known on the control side. Rolling resistance and air resistance are also known from the control side and are preferably assumed to be constant.

In step 13th of the flow chart 8th the 2 depends on the measured value of the acceleration sensor 7th of the motor vehicle determines the second gradient of the motor vehicle or the second variable corresponding to the second gradient, and the step 11 provided as an input variable.

wobei

• a_X-SENS der Messwert des Beschleunigungssensors ist,
• ν̇_FZG die Längsbeschleunigung des Kraftfahrzeugs ist,
• g die Erdbeschleunigung ist,
• α2 die zweite Steigung des Kraftfahrzeugs ist.

The second gradient of the motor vehicle or the second variable corresponding to the second gradient is preferably calculated as a function of the measured value of the acceleration sensor according to the following equation: $$a_{X-\mathrm{S.}\mathrm{E.}N\mathrm{S.}}={\dot{\nu }}_{\mathrm{F.}ZG}+G\times \text{sin}\left(\alpha 2\right)$$

in which

• a _{X-SENS is} the measured value of the acceleration sensor,
• ν̇ _{FZG is} the longitudinal acceleration of the motor vehicle,
• g is the acceleration due to gravity,
• α2 is the second slope of the motor vehicle.

The longitudinal acceleration of the motor vehicle is preferably determined in turn from the speed of the motor vehicle, which is known on the control side, with the aid of the derivation filter.

The above equation for determining the second gradient of the motor vehicle or the second variable corresponding to the second gradient is independent of braking forces.

In step 11 Then, as stated above, the determination of the braking force or the variable corresponding to the braking force takes place, with a braking force factor preferably being determined as the variable corresponding to the braking force, preferably on the basis of the difference between that in step 12th certain first slope and the in step 13th certain second slope.

wobei

• k_BR der Bremskraftfaktor ist,
• m die Masse des Kraftfahrzeugs ist,
• g die Erdbeschleunigung ist,
• Δα die Differenz zwischen der ersten Steigung und der zweiten Steigung ist,
• α1 die erste Steigung des Kraftfahrzeugs ist,
• α2 die zweite Steigung des Kraftfahrzeugs ist,
• p_BR ein Bremsdruck der Primärbremse ist.

The braking force factor is preferably calculated using the following equation: $$\begin{array}{l}{k}_{\mathrm{B.}\mathrm{R.}}=\frac{m\times G\times \Delta \alpha }{p_{\mathrm{B.}\mathrm{R.}}}\\ \Delta \alpha \text{=}\alpha \text{1}-\mathrm{<figure-callout\; id="2"\; label="\alpha "\; filenames="DE102015219554B4\_0017.png"\; state="\{\{state\}\}">\alpha </figure-callout>}2\end{array}$$

in which

• k _{BR is} the braking force factor,
• m is the mass of the motor vehicle,
• g is the acceleration due to gravity,
• Δα is the difference between the first slope and the second slope,
• α1 is the first slope of the motor vehicle,
• α2 is the second slope of the motor vehicle,
• p _{BR is} a brake pressure of the primary brake.

The brake pressure of the primary brake operated on the foot or driver side is known on the control side.

The control unit which carries out the method according to the invention is preferably the transmission control unit 6th .

$$\alpha 1_k=\alpha 1_{k-1}$$

wobei

• k, k-1 Abtastschritte sind,
• v die Geschwindigkeit des Kraftfahrzeugs ist,
• dT die Abtastzeit ist.

In a preferred embodiment of the method according to the invention it can be provided that in step 12th to replace the calculation model or acceleration model of the motor vehicle used to calculate the first slope a1, assuming a constant slope and small slope angles, by the following discrete, linear model: $$\begin{array}{l}{\nu }_k={\nu }_{k-1}+dT\times \frac{f_{\mathrm{A.}N}}{m}-dT\times G\times \alpha 1_{k-1}-dT\times \frac{f_{\mathrm{R.}}-f_{\mathrm{L.}}}{m}\\ \end{array}$$

$$\alpha 1_k=\alpha 1_{k-1}$$

in which

• k, k-1 are sampling steps,
• v is the speed of the motor vehicle,
• dT is the sampling time.

$$\alpha 1_{BOEB\_k}=\alpha 1_{BOEB\_k-1}+k_{\alpha }\times \left({\nu }_k-{\nu }_{BEOEB\_k-1}\right)$$

A discrete observer BEOB can be used for the above discrete model, the observer equations for speed v _BEOB and first slope α1 _{BEOB being} as follows: $${\nu }_{\mathrm{B.}O\mathrm{E.}\mathrm{B.}\_k}={\nu }_{\mathrm{B.}\mathrm{E.}O\mathrm{B.}\_k-1}+dT\times \frac{f_{\mathrm{A.}N}}{m}-dT\times G\times \alpha 1_{\mathrm{B.}\mathrm{E.}O\mathrm{B.}\_k-1}+k_{\nu }\times \left({\nu }_k-{\nu }_{\mathrm{B.}O\mathrm{E.}\mathrm{B.}\_k-1}\right)$$

$$\mathrm{<figure-callout\; id="1"\; label="\alpha "\; filenames="DE102015219554B4\_0017.png"\; state="\{\{state\}\}">\alpha </figure-callout>}{1}_{\mathrm{B.}O\mathrm{E.}\mathrm{B.}\_k}=\mathrm{<figure-callout\; id="1"\; label="\alpha "\; filenames="DE102015219554B4\_0017.png"\; state="\{\{state\}\}">\alpha </figure-callout>}{1}_{\mathrm{B.}O\mathrm{E.}\mathrm{B.}\_k-1}+k_{\alpha }\times \left({\nu }_k-{\nu }_{\mathrm{B.}\mathrm{E.}O\mathrm{E.}\mathrm{B.}\_k-1}\right)$$

$$k_{\alpha }=-\frac{\lambda 1+\lambda 2}{g\times dT}$$

wobei die Pole λ1 und λ2 des Beobachters innerhalb des sogenannten Einheitskreises liegen müssen.The gain factors k _v and k _{α of} the above observer equations are calculated with a so-called pole specification, $$k_{\nu }=1-\left(\mathrm{<figure-callout\; id="1"\; label="\lambda "\; filenames="DE102015219554B4\_0017.png"\; state="\{\{state\}\}">\lambda </figure-callout>}1+\lambda 2\right)$$

$$k_{\alpha }=-\frac{\mathrm{<figure-callout\; id="1"\; label="\lambda "\; filenames="DE102015219554B4\_0017.png"\; state="\{\{state\}\}">\lambda </figure-callout>}1+\lambda 2}{G\times dT}$$

where the poles λ1 and λ2 of the observer must lie within the so-called unit circle.

$$\alpha 2_{KALM\_k}=\alpha 2_{KALM\_k-1}+k_{KALM\_\alpha }\times \left({\nu }_k-{\nu }_{KALM\_k-1}\right)$$

The in step 13th The equation used to calculate the second slope a2 can also be replaced by a discrete equation, with the help of a so-called Kalman filter KALM. The following equations then preferably apply for speed v _KALM and second slope α2 _KALM . $${\nu }_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}\_k}={\nu }_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}\_k-1}+dT\times a_{X-\mathrm{S.}\mathrm{E.}N\mathrm{S.}}-dT\times G\times \alpha 2_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}\_k-1}+k_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}\_\nu }\times \left({\nu }_k-{\nu }_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}\_k-1}\right)$$

$$\alpha 2_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}\_k}=\alpha 2_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}\_k-1}+k_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}\_\alpha }\times \left({\nu }_k-{\nu }_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}\_k-1}\right)$$

The gain _factors k KALM_v and k _{KALM_α of} the above Kalman filter equations are adapted.

$$\Delta \alpha =\alpha 1_{BEOB}-\alpha 2_{KALM}$$

On the basis of the first slope determined on the basis of the above discrete observer equations and the second slope determined on the basis of the above discrete Kalman filter model, a difference and, depending on this difference, the braking force or the variable corresponding to the braking force can in turn be calculated. The following equations then preferably apply: $$k_{\mathrm{B.}\mathrm{R.}}=\frac{m\times G\times \Delta \alpha }{p_{\mathrm{B.}\mathrm{R.}}}$$

$$\Delta \alpha =\mathrm{<figure-callout\; id="1"\; label="\alpha "\; filenames="DE102015219554B4\_0017.png"\; state="\{\{state\}\}">\alpha </figure-callout>}{1}_{\mathrm{B.}\mathrm{E.}O\mathrm{B.}}-\alpha 2_{K\mathrm{A.}\mathrm{L.}\mathrm{M.}}$$

As explained above, the brake pressure p _{BR of} the primary brake is known on the control side.

List of reference symbols

1

Powertrain

2

Drive unit

3

transmission

4th

Downforce

5

Engine control unit

6th

Transmission control unit

7th

Accelerometer

8th

Flowchart

9

step

10

step

11

step

12th

step

13th

step

Claims (9)

Method for determining a braking force or a variable of a motor vehicle corresponding to the braking force, with the following steps: A first gradient of the motor vehicle or a first variable corresponding to the first gradient is determined from a calculation model of a motor vehicle; Depending on a measured value of an acceleration sensor of the motor vehicle, a second gradient of the motor vehicle or a second variable corresponding to the second gradient is determined; a difference is determined between the first slope and the second slope or between the first variable and the second variable; The braking force or the variable corresponding to the braking force is determined as a function of this difference between the first slope and the second slope or between the first variable and the second variable. Procedure according to Claim 1 , characterized in that the first gradient of the motor vehicle or the first variable corresponding to the first gradient is calculated from an acceleration model of the motor vehicle. Procedure according to Claim 2 , characterized in that the first slope of the motor vehicle or the first variable corresponding to the first slope is calculated according to the following equation: $$m\times {\dot{\nu }}_{\mathrm{F.}ZG}=f_{\mathrm{A.}N}-m\times G\times \text{sin}\left(\alpha 1\right)-f_{\mathrm{R.}}-f_{\mathrm{L.}}$$

where m is the mass of the motor vehicle, where ν̇ _{FZG is} the longitudinal acceleration of the motor vehicle, where f _{AN is} the driving force of the motor vehicle, where f _{R is} the rolling resistance of the motor vehicle, where f _{L is} the air resistance of the motor vehicle, where g is the acceleration due to gravity, and where a1 is the first grade of the motor vehicle. Method according to one of the Claims 1 to 3 , characterized in that the second slope of the motor vehicle or the second variable corresponding to the second slope is calculated as a function of the measured value of the acceleration sensor according to the following equation: $$a_{X-\mathrm{S.}\mathrm{E.}N\mathrm{S.}}={\dot{\nu }}_{\mathrm{F.}ZG}+G\times \text{sin}\left(\alpha 2\right)$$

where a _{X-SENS is} the measured value of the acceleration sensor, where ν̇ _{FZG is} the longitudinal acceleration of the motor vehicle, where g is the acceleration due to gravity, and where a2 is the second gradient of the motor vehicle. Method according to one of the Claims 1 to 4th , characterized in that a braking force factor is calculated according to the following equation as the variable corresponding to the braking force: $$k_{\mathrm{B.}\mathrm{R.}}=\frac{m\times G\times \Delta \alpha }{p_{\mathrm{B.}\mathrm{R.}}}$$

where k _{BR is} the braking force factor, where m is the mass of the motor vehicle, where g is the acceleration due to gravity, where Δα is the difference between the first slope and the second slope, and where p _{BR is} a brake pressure. Method according to one of the Claims 1 to 5 , characterized in that the braking force or the value corresponding to the braking force is only determined when the vehicle is being driven straight ahead and / or when the drive wheels of the motor vehicle are free of slip and / or when the drive wheels of the motor vehicle are unblocked and / or when a The mass of the motor vehicle is known and / or if a speed of the motor vehicle is greater than a limit value and / or if an anti-lock braking system of the motor vehicle is inactive and / or if a primary brake of the motor vehicle is active and / or if a secondary brake of the motor vehicle is inactive. Control device for determining a braking force or a variable of a motor vehicle that corresponds to the braking force, wherein: the control device determines a first gradient of the motor vehicle or a first variable corresponding to the first gradient from a calculation model of a motor vehicle; the control device determines a second gradient of the motor vehicle or a second variable corresponding to the second gradient as a function of a measured value of an acceleration sensor of the motor vehicle; the control unit determines a difference between the first gradient and the second gradient or between the first variable and the second variable; the control unit determines the braking force or the variable corresponding to the braking force as a function of this difference between the first gradient and the second gradient or between the first variable and the second variable. Control unit after Claim 7 , characterized in that the control device follows the first slope of the motor vehicle or the first variable corresponding to the first slope Claim 2 or 3 calculated; and / or the control unit follows the second gradient of the motor vehicle or the second variable corresponding to the second gradient Claim 4 calculated; and / or the control unit according to a braking force factor as a variable corresponding to the braking force Claim 5 calculated. Control unit after Claim 7 or 8th , characterized in that the control unit determines the braking force or the variable corresponding to the braking force only when the vehicle is driven straight ahead and / or when the drive wheels of the motor vehicle are free of slippage and / or when the drive wheels of the motor vehicle are unblocked and / or when a mass of the motor vehicle is known and / or if a speed of the motor vehicle is greater than a limit value and / or if an anti-lock braking system of the motor vehicle is inactive and / or if a primary brake of the motor vehicle is active and / or if a secondary brake of the motor vehicle is inactive.

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