DE102004008383A1 - Method and system for compensating for a change in the transmission behavior of an electronic brake system - Google Patents

Abstract

The method of compensating for variation of transmission characteristics in a brake system involves determining the brake position characteristic value in a first operating condition of the braking system and determining the brake operation characteristics in this condition. It involves determining similar values in a second operating condition of the brake . The alteration of the operating parameters under feedback of the collected values from the first and second braking conditions are then compensated for.

Description

The The present invention relates to a method for compensating a by a change at least one operating parameter, in particular friction coefficient and / or Contact position and / or stiffness, induced change the transmission behavior an electromechanical brake system, in particular an electromechanical Braking system with self-reinforcement, as well as a corresponding brake system.

From the US 4,995,483 a method is known and is used in the operation of a designed as a disc brake electromechanical brake application, in which a friction member by means of an electric motor and a gear assembly is electromechanically pressed on a trained as a brake disc rotating, braked component. In the method, it is provided for controlling the brake to detect the position of the friction member during a feed operation on the brake disk, in which the friction member is pressed against the brake disk with a certain Mindestruspannkraft. For detecting the minimum restraint force, a force sensor is arranged close to the friction member such that the application force with which the friction member is pressed against the brake disk can be measured. When the predetermined Mindestruspannkraft is exceeded, the force sensor outputs a signal. This signal serves as an indicator that the friction member engages the brake disc and causes a braking effect. The friction member position at which the force sensor outputs the signal is defined as the zero position or friction member contact position. Starting from this friction member contact position then a clearance is set. This solution has, on the one hand, the disadvantage of a relatively high equipment outlay, since it is necessary to arrange the force sensor together with the supply lines near the moving friction member. Moreover, this solution does not determine the actual contact position at which the friction member is in contact with the brake disk, but a position is detected and used as a friction member contact position for adjusting the brake, in which already occurred a non-negligible braking effect is.

From the EP 0 853 572 B1 Another method for determining a contact position in an electromechanical brake is known. In this method, the provided for the feed movement of the friction member to the brake disc towards Elek tromotor is controlled such that it performs a slightly accelerated motor movement as long as the friction member does not yet come into contact with the component to be braked. However, as soon as there is contact between the friction member and component to be braked, the motor acceleration decreases due to the contact-related counterforce and finally reaches the value zero. This zero crossing of the motor acceleration is detected and serves as a contact signal for the application of the friction member to the surface of the component to be braked. The corresponding motor angle at the time of zero crossing gives the zero position of the motor. Also in this method, it is necessary to determine the friction member contact position to press the friction member with little force against the friction surface of the component to be braked. Only when this has been done, the brake can be adjusted taking into account the clearance. Furthermore, this prior art proposes to provide a contact pin which enables electrical detection of a contact between another passive friction element and the brake disk.

The solutions known from the prior art described above are not suitable for electromechanical brakes, which are formed with a self-reinforcing arrangement. Such an electromechanical brake is for example from the DE 198 19 564 C2 and the corresponding one US 6,318,513 known. In the case of such electromechanical brakes with self-amplification, due to the self-boosting effect, there may be no measurable force reaction to the electric motor when the friction member and the component to be braked contact one another. Such an effect arises, for example, when in the brake according to the DE 198 19 564 C2 the coefficient of friction μ is equal to the tangent of the pitch angle α, so that a state can be set in which temporarily no power supply from the electric motor is required in order to achieve a braking effect.

An alternative method for determining the contact position in a brake is from DE 100 05 758 A1 known. In this system, the total elasticity of the brake system is detected, ie the elasticity, which is composed of partial elasticities of friction member or friction members and brake disc and the housing. With progressive wear of the friction linings formed on the friction elements, the overall elasticity decreases due to the reduced thickness of the friction linings. The measured total elasticity serves as a measure of the current state of wear and as a basis for setting the current zero position. However, the method presented in this document has the disadvantage that the elasticity of the overall system also changes depending on parameters of the current operating state such as brake temperature, outside temperature, etc., so that the detection is relatively inaccurate and unreliable.

As a further prior art to electromechanical brakes, in which, however, is not discussed in more detail on the problem of contact position determination, in addition to the DE 195 39 012 A1 , the DE 195 43 098 C2 and WO 96/03301.

One Another problem of the above-described prior art lies in the fact that no precautions are taken, which is a change consider an operating parameter of the brake system, such as a change the coefficient of friction and / or the contact position and / or the stiffness the brake unit due to an increase in the operating temperature of the brake system. However, it has been shown that the coefficient of friction and / or the contact position and / or the stiffness of the brake unit can change significantly during braking, so that the transmission behavior of the brake system change greatly can and thus control and displacement of the friction member in dependence from the change is required. For example, measurements have shown that Coefficient of friction within a range of 0.15 to 0.6 can fluctuate. This makes it difficult to adequately adjust the brake system regulate.

It Object of the present invention, a method of the initially designated type with which it under relatively low technical equipment Effort in electromechanical brakes, especially with self-boosting effect, possible is a business change the transmission behavior of the braking system, in which a change of an operating parameter of the braking system is caused to detect and compensate so the control quality of the overall system.

• a) Erfassen einer die Betriebsstellung des Bremssystems bestimmenden Betriebsstellungs-Kenngröße in einer ersten Betriebsstellung des Bremssystems,
• b) Erfassen einer die Bremswirkung des Bremssystems charakterisierenden Bremswirkungs-Kenngröße in der ersten Betriebsstellung des Bremssystems,
• c) Erfassen einer die Betriebsstellung des Bremssystems bestimmenden Betriebsstellungs-Kenngröße in wenigstens einer weiteren Betriebsstellung des Bremssystems,
• d) Erfassen einer die Bremswirkung des Bremssystems charakterisierenden Bremswirkungs-Kenngröße in der wenigstens einen weiteren Betriebsstellung des Bremssystems und
• e) Kompensieren einer Änderung des wenigstens einen Betriebsparameters unter Berücksichtigung der erfassten Betriebsstellungs-Kenngrößen und Bremswirkungs-Kenngrößen der ersten und der wenigstens einen weiteren Betriebsstellung.

This object is achieved by a method of the type described above, the method comprising the steps:

• a) detecting an operating position parameter determining the operating position of the brake system in a first operating position of the brake system,
• b) detecting a braking effect characteristic variable characterizing the braking effect of the brake system in the first operating position of the brake system,
• c) detecting an operating position parameter determining the operating position of the brake system in at least one further operating position of the brake system,
• d) detecting a braking effect of the braking system characterizing the braking effect characteristic in the at least one further operating position of the brake system and
• e) compensating for a change in the at least one operating parameter taking into account the detected operating position characteristics and braking performance characteristics of the first and the at least one further operating position.

By estimate the braking effect characteristic and by Compensate the change the operating parameter, for example, the coefficient of friction and / or the Contact position and / or the stiffness of the brake unit, let operational changes compensate the operating parameter and the control quality accordingly improve or at least maintain it at a constant level.

According to one variant The invention provides that the operating position characteristic is the friction lining position or a characterizing this characteristic Is worth. It can be provided that the vehicle brake with a friction actuator displacing the electric actuator is executed, wherein the operating position characteristic is the actuator position of the electric actuator or a value characterizing this characteristic is.

Further provides a development of the invention, that the braking effect characteristic of the braking torque, the braking delay, the wheel slip or the clamping force or a characterizing these characteristics Is worth. The following is intended in particular to the case of use the braking torque are received as a braking effect characteristic, wherein the braking torque by means of appropriate elasto-kinematic effects, For example, by means of known torque sensors detected becomes. The braking effect characteristic serves for the present invention as a controlled variable in the regulation of as electromechanical brake system executed controlled system.

wobei die Größen

M_B

das gegenwärtige Bremsmoment,

μ_B

der Reibwert zwischen Bremsbelag und Bremsscheibe des Bremssystems,

r_B

der effektive Radius der Bremse,

k*

die Steifigkeit des Bremssystems,

α

der Keilwinkel,

L

die Spindelsteigung des Aktuators,

θ_M

die gegenwärtige Aktuatorstellung und

θ₀

die Aktuatorstellung an der Kontaktposition des Bremssystems sind.

In a particular embodiment of the invention, it is provided that the brake system is designed as a floating caliper brake with self-reinforcing effect, which has a wedge arrangement and whose actuator is formed with screw drive. Assuming this embodiment variant of the invention, the invention provides that the changing operating parameter is determined on the basis of the assumption of a linear relationship between actuator position and braking torque according to the equation:

the sizes

M _B

the current braking torque,

μ _B

the coefficient of friction between the brake lining and the brake disk of the brake system,

r _B

the effective radius of the brake,

k *

the rigidity of the braking system,

α

the wedge angle,

L

the spindle pitch of the actuator,

θ _M

the current actuator position and

θ ₀

the actuator position are at the contact position of the brake system.

wobei die Größe M_Störungen denjenigen Anteil des gemessenen Bremsmoments repräsentiert, der beispielsweise auf Messfehler oder auf Abweichungen durch Fertigungstoleranzen bei der Herstellung und bei der Montage des Bremssystems auftritt und nicht unmittelbar auf eine Bremsung zurückgeht. Beispielsweise kann die Bremsscheibe Asymmetrien aufweisen, die die Rundlauf-Eigenschaften der Bremsscheibe beeinträchtigen.In fact, this equation would have to read:

wherein the size M _{interference represents} that portion of the measured braking torque, which occurs, for example, to measurement errors or deviations due to manufacturing tolerances in the manufacture and assembly of the brake system and does not directly go back to braking. For example, the brake disc may have asymmetries that affect the concentricity properties of the brake disc.

It It should be noted that the overall stiffness k * of the braking system is not linear is that, however, with small changes in the brake system acting clamping forces a linearization of the rigidity at most too small tolerable Deviations leads. But it is also possible according to the invention, the Calculation of nonlinear stiffness models. So For example, the Applicant has recognized that the overall rigidity k * of the brake system increases sharply with increasing wear. This is because the lining material is relatively soft. Takes due to wear the thickness of the friction lining, the overall system is accordingly stiffer. As with the brake system according to the invention but the wear detectable is, as explained below can be the calculations carried out in the context of the invention one to the present Wear condition corresponding Stiffness be assigned. This allows a change in stiffness also computationally compensate.

wobei die Größen

ĝ

eine Schätzung des Ausdrucks

wiedergibt,

ΔM_B

die Differenz der erfassten Bremsmomentwerte,

Δθ_M

die Differenz der erfassten Aktuatorstellungen,

μ_B

der Reibwert zwischen Bremsbelag und Bremsscheibe des Bremssystems,

r_B

der effektive Radius der Bremse,

k*

die Steifigkeit des Bremssystems,

α

der Keilwinkel und

L

die Spindelsteigung des Aktuators sind.

In principle, a distinction must be made between two applications of the method according to the invention. Thus, in the first case it is assumed that both the position of the friction lining and the braking torque change significantly during a braking operation within a relatively short time. If the observed period is small enough so that all other parameters remain constant, it is possible according to the invention to proceed such that for determining a change in the operating parameter of the brake system, for example the coefficient of friction μ _B or / and the contact position and / or the stiffness, and for the subsequent Compensate for this change in the operating parameter by changing the gain of the control, the braking torque M _B at the first actuator position θ _M corresponding to the contact position or a predetermined operating position deviating from the contact position of the brake system, and at least one further from the contact position or the predetermined operating position different operating position is detected in each case that the difference DM _B of the detected braking torque values and the detected actuator positions Δθ _M is calculated and that the calculated differences Δθ .DELTA.M _B and _M based on the changing operational parameters, especially Specifically, the coefficient of friction and / or the contact position and / or the stiffness, is determined according to the equation

the sizes

G

an estimate of the term

reproduces,

ΔM _B

the difference between the recorded brake torque values,

Δθ _M

the difference between the detected actuator positions,

μ _B

the coefficient of friction between the brake lining and the brake disk of the brake system,

r _B

the effective radius of the brake,

k *

the rigidity of the braking system,

α

the wedge angle and

L

the spindle pitch of the actuator are.

These Approach comes however then to their limits, if over a longer one Period provided a constant braking torque from the brake system shall be. Especially in such a case, the above specified requirement for a significant change in brake torque not fulfilled, so that the above-mentioned approach is not sufficient gives good results.

verglichen wird. Dieser Vergleich führt zu einem angepassten Wert für ĝ gemäß folgender Gleichung:

wobei

ĝ_neu

einen aktuellen Wert des Ausdrucks

wiedergibt,

ĝ_alt

ein bekannter vorangehender Wert von ĝ ist,

M_B

das erfasste Bremsmoment ist,

θ_M

die korrespondierende Aktuatorstellung ist,

θ₀

die Aktuatorstellung an der Kontaktposition oder einer von der Kontaktposition abweichenden vorbestimmten Betriebsstellung des Bremssystems ist,

M₀

das Bremsmoment an der Bezugsposition θ₀ ist (M₀=0, wenn θ₀ die Kontaktposition ist),

K_est

der Verstärkungsfaktor der Schätzung ist,

μ_B

der Reibwert zwischen Bremsbelag und Bremsscheibe des Bremssystemsist,

r_B

der effektive Radius der Bremse ist,

k*

die Steifigkeit des Bremssystems ist,

α

der Keilwinkel ist und

L

die Spindelsteigung des Aktuators ist.

To address this problem, the invention provides for a second application that for the correction of G is the current measured with the M _B on the basis of the present value of G _old estimated value

is compared. This comparison leads to an adjusted value for ĝ according to the following equation:

in which

ĝ _new

a current value of the expression

reproduces,

ĝ _old

is a known previous value of ĝ,

M _B

the detected braking torque is,

θ _M

the corresponding actuator position is,

θ ₀

the actuator position is at the contact position or a predetermined operating position of the brake system deviating from the contact position,

M ₀

the braking torque at the reference position θ ₀ is (M ₀ = 0 when θ _{0 is} the contact position),

K _est

the gain of the estimate is

μ _B

the coefficient of friction between the brake pad and the brake disk of the brake system is

r _B

the effective radius of the brake is,

k *

the stiffness of the braking system is

α

the wedge angle is and

L

the spindle pitch of the actuator is.

As a reference position θ ₀ , for example, the contact positions determined in the initialization described below or another operating position may be used. Since ĝ contains the coefficient of friction, a change in the coefficient of friction is reflected in a correction of ĝ.

For initialization of the method according to the invention can be provided that is assumed for a first estimate of the braking torque of a predetermined coefficient of friction, for example, of μ _B = 0.5, and.

According to the invention is at a first-time braking operation after startup of the brake - for example after starting a equipped with a brake according to the invention Vehicle - the at least one friction member with a force against the braked Component, such as the rotating brake disc, pressed, so that a small fraction of a nominal braking torque is generated. In this state, the position of the friction member and the current braking torque detected. As a result, the friction member is further on the braked Component to move, i. the braking torque is increased, while still the braking torque and the Reibgliedposition detected and formed pairs of values become. These value pairs are evaluated and it becomes a regression line determines which relationship between the braking torque and the Reibgliedposition describes. From the regression line is then the theoretical friction member contact position is determined, in which the at least one friction member with the at least one braked component just comes into contact. The determined theoretical Frictional member contact position then serves for further braking operations as Starting point on which the entire brake is adjusted. This theoretically determined friction member contact position may be referred to as Reference point for the clearance setting be used. In a plurality of friction members is the theoretical But friction member contact position preferably chosen so that all friction members in contact with the braked assigned to this Components are located.

For example the fraction at which a first value pair is detected may be included in the Range between 1-10%, preferably at 3% of the nominal braking torque lie. Furthermore, with regard to the assessment of the recording period be provided that the at least one further value pair after Expiration of a predetermined period of time after determination of the preceding Value pairs is detected. An appropriate value for this period of time is, for example ranging from a few milliseconds to a second. Captured corresponding value pairs in such short time periods one after the other, this ensures that the state of the brake changes only slightly and thus the above explained Adopting a quasi-stationary State of the brake is sufficiently accurate.

M_B

das Bremsmoment bezeichnet,

θ

die gegenwärtige Aktuatorstellung bezeichnet,

C₁, C₂

Konstanten bezeichnet.

The determination of the regression line can be done according to the equation: M B = C 1 · Θ + C 2 (7) in which

M _B

denotes the braking torque,

θ

designates the current actuator position,

C ₁ , C ₂

Constants.

According to one Development of the invention, the theoretical friction member contact position, in which the at least one friction member with the at least one braked component just comes into contact, from the regression line on the assumption that at the theoretical friction member contact position, the Braking torque is zero.

Basically it is possible at each braking operation, the method of determination described above to perform the theoretical friction member contact position. It but it is also possible perform this method only at predetermined intervals, for example in a vehicle always after every vehicle start, after elapse a predetermined accumulated operating time or a predetermined one covered Driving distance. In this case, it can be provided according to the invention that the determined theoretical friction member contact position, in which the at least one friction member with the at least one braked Component just comes into contact while caching until the theoretical friction member contact position is determined again becomes.

The according to the above Description determined friction member contact position can also do so serve, to the present wear state to close the brake. In In this context, it can be provided that from the determined theoretical friction member contact position, wherein the at least a friction member with the at least one component to be braked straight comes into contact, and from a stored friction member contact position, in which in the first operation of the brake, the at least one friction member with the at least one component to be braked just in contact occurs, the present one wear state the brake is calculated.

In continuation of this idea, a further development of the invention envisages that a predetermined value for a limit friction element position is stored and that, if the currently determined theories table friction member contact position, in which the at least one friction member with the at least one component to be braked just comes into contact with the limit Reibgliedposition coincides, a warning signal is issued. If this method is applied to a brake which has an adjusting mechanism, a signal for actuating the adjustment can be generated in this case.

It It should be noted that in the context of this description of the invention often the Term "contact position" is used. in principle is thus meant that friction member position at which the at least a friction member and - im Trap of several friction members - all Friction members come into contact with the component to be braked. There However, this contact position can not be measured accurately and rather than a clear graspable position in reality rather a contact area is set in the context of this invention in usually a theoretical contact position used in the Contact area is located and the fictitious as that Reibgliedposition is considered, in which the at least one friction member and - in the case several friction members - all friction members frictionally contact the component to be braked.

The explained above Approach resulting from the determination of a regression line rests but bumps then to their limits, if over a longer one Period provided a constant braking torque from the brake system shall be. Especially in such a case, the above specified requirement for a significant change in brake torque not fulfilled, so that the above-mentioned approach is not sufficient gives good results. About that In addition, just over at one a longer one Period held constant braking torque the problem of a temperature increase and with this along with a change the coefficient of friction as well as a thermal dimensional changes conditional contact position shift. It is therefore necessary in determining the braking effect characteristic in the at least one further operating position the change to consider this operating parameter. A major problem of operational changes in operating parameters in braking systems is that due to the changes can also shift the contact position, and generally speaking, that causes the transmission behavior of the brake system can. The following are measures explained who take the problem into account.

zu ermitteln. Dies kann insbesondere dann der Fall sein, wenn das Bremsmoment konstant gehalten werden soll. Um jedoch die Bremswirkung durch derartige Bremsbetätigungen nicht zu beeinträchtigen, sieht eine Weiterbildung der Erfindung vor, dass radweise das Bremsmoment M_{B Rad} und die Aktuatorstellung θ_{M Rad} verändert werden, wobei das Gesamtbremsmoment über alle Räder des Kraftfahrzeugs konstant gehalten wird. Eine weitere Möglichkeit zur Verbesserung der Genauigkeit des erfindungsgemäßen Verfahrens besteht darin, die Bremse zu betätigen, um dadurch die Parameter zu verifizieren und gegebenenfalls zu korrigieren.In order to improve the accuracy of the method according to the invention, a development of the invention provides that a plurality of value pairs of braking torque M _B and actuator position θ _M are detected and taken into account as reference points for estimating the coefficient of friction μ _B. If necessary, small brake actuations can be performed to

to investigate. This may be the case in particular if the braking torque is to be kept constant. However, in order not to adversely affect the braking effect by such brake actuations, a development of the invention that radweise the braking torque M _{B wheel} and the actuator position θ _{M wheel are} changed, the total braking torque over all wheels of the motor vehicle is kept constant. Another way to improve the accuracy of the method according to the invention is to operate the brake, thereby to verify the parameters and correct if necessary.

Further can be provided in this context, that in one of the Components of the braking system during the operating temperature gradient, the braking behavior influenced, as well as a resulting dimensional change the component is considered becomes. For example, it is possible based on the recorded speed profile and the detected Braking torque curve to determine the required braking energy and on the basis of the released thermal energy shut down. This is a measure of thermal conditional dimensional changes of brake components, such as the floating caliper.

If, in a first approximation, it is again assumed that a linear characteristic curve is present, an embodiment of the method according to the invention provides that the ratio is monitored from a determined coefficient of friction μ _B and the independently estimated expression ĝ, which represents the slope of the braking torque curve and the ratio is used to check the plausibility of the determination of the expression ĝ.

For a linear characteristic, the ratio should remain approximately the same. In other words, the approximately determined expression ĝ and the independently estimated friction coefficient μ _B are compared with one another in the context of a plausibility check.

wobei

F_B

die sich aus dem aktuellen Bremsmoment ergebende Bremskraft,

F_A

die über den Aktuator ausgeübte Antriebskraft und

α

der Keilwinkel sind.

In this context, it may be provided that the coefficient of friction μ _{B is} determined on the basis of the equation

in which

F _B

the braking force resulting from the current braking torque,

F _A

the force exerted on the actuator driving force and

α

the wedge angle are.

berechnet wird und mit dem Ausdruck ĝ, vorzugsweise unter Verwendung der Methode der kleinsten Quadrate, verglichen wird. Dadurch kann die Kennlinie (Steigung und Bezugspunkt) korrigiert werden.Additionally or alternatively, it may be provided according to the invention that when changing the braking torque M _B and actuator position θ _M, the ratio

is calculated and compared with the expression ĝ, preferably using the method of least squares. As a result, the characteristic curve (slope and reference point) can be corrected.

to Control of the braking system can also be provided that a model ideal course of the controlled variable with the indeed measured course of the controlled variable, for example the braking torque is compared and depending on the deviation between ideal and actual measured course of expression ĝ is changed or a targeted brake is made to correct the estimate of ĝ.

The The invention further relates to a braking system for controlling a Brake, in particular for performing the method according to any one of the preceding claims, wherein the brake at least one friction member and at least one rotating, braked component includes, further to achieve a braking effect the at least one friction member against the at least one rotating, pressed braked component and wherein an operating position characteristic acquisition means, in particular a position detecting means for detecting a current one Friction position characterizing operating position characteristic of the brake system, a braking action detecting means for detecting the current braking torque or another braking effect characteristic and a control unit are.

The invention is further provided that the operating position characteristic detecting means in a first and in at least one further operating position of the brake system a recorded the operating position of the brake system determining operating position characteristic, that the braking effect detecting means in the first operating position of the brake system is a characterizing the braking effect of the brake system Recorded brake performance characteristic, that the control unit based on the detected values of the operating position characteristic and the Brake effect characteristic one Value for the braking effect of the braking system characterizing braking effect characteristic in the detected at least one other operating position of the brake system and that the control unit makes a change an operating parameter, in particular the friction coefficient and / or the Contact position and / or stiffness, taking into account the recorded operating position characteristics and Brake effect characteristics of the first and the at least one other operating position compensated.

According to one embodiment invention, the brake is designed as an electromechanical brake, in which the at least one friction member by means of an electromechanical Drive can be pressed against the at least one component to be braked. In a particular application of the invention, the electromechanical Brake a self-energizing arrangement of the electromechanical Drive on the at least one friction member exerted friction force. It can be provided that the control unit to determine the current Friction member position the drive movement of the electromechanical drive detected. It also suggests that the brake action detection means is designed to determine the current braking torque.

The inventive method is particularly suitable for use in electromechanical brakes, ie in brakes, in which the at least one friction member is pressed by means of an electromechanical drive against the at least one component to be braked. If you pay attention Such brakes, it should be noted that the inventive method is not only suitable for electromechanical brakes, in which the electromechanical drive alone, ie without reinforcing mechanism, is responsible for the frictional force. Rather, the inventive method is also suitable for electromechanical cal brakes with self-boosting, as described for example in the beginning already mentioned DE 198 19 564 C2 and the corresponding one US 6,318,513 B1 are described. In order to avoid repetition, reference should be made to the content of these documents with regard to the operation of such electromechanical brakes with self-boosting, which should be included by this reference in the disclosure of this description.

in the The following is an embodiment of the present invention with reference to the accompanying figures. It represent:

1 a designed as a disc brake electro-mechanical brake with self-energizing mechanism in a spatial representation to explain the basic principle of the system according to the invention;

2 a diagram for explaining a possible temperature-induced change in the coefficient of friction;

3 a diagram accordingly 2 in the case of "fading",

4 a diagram showing the influence of interference on comparable measurements,

5 a diagram that provides information about the points to use in a current estimate,

6 a diagram for explaining the situation with a constant braking torque,

7 a schematic flow diagram for explaining the method according to the invention and

8th a schematic flow diagram for explaining the application of the method of least squares in the selection of measured values.

In 1 is a brake system according to the invention in general 10 designated. This is as a disc brake with an internally ventilated brake disc 12 executed, which is rotatable about an axis A.

At an axial distance from the brake disc 12 is parallel to it and coaxial to the axis A, a first carrier ring 14 arranged on which the brake disc 12 facing side several friction members 16 are attached. These friction members 16 are - as will be explained later - to the brake disc 12 Can be applied to the braking of the brake disc 12 generate required frictional force. On the opposite, from the brake disc 12 opposite side of the first carrier ring 14 are a series of wedges 18 firmly attached, each of which has a first surface 20 with a pitch angle α and a second area 22 defined with a pitch angle β. With respect to a plan view of the first carrier ring 14 Both surfaces extend 20 . 22 immediately adjacent to each other substantially in the circumferential direction of the carrier ring 14 ,

How out 1 apparent, are the two surfaces 20 . 22 inclined to each other, wherein the pitch angle β of the second surface 22 significantly larger than the pitch angle α of the first surface 20 is. The wedges 18 of which in 1 For better clarity, only a few are shown, follow in the circumferential direction of the carrier ring 14 contemplates each other directly so that the entire axial outer surface of the first carrier ring 14 with wedges 18 is covered. The wedges 18 can be integral with the first carrier ring 14 be educated.

Axially outside the first carrier ring 14 is an annular bolt carrier 26 arranged with approximately U-shaped cross-section, an annular and the carrier ring 14 open cavity 28 defines in which the wedges 18 protrude. In this annular cavity 28 is one of the number of wedges 18 corresponding number of bolts 30 rotatably mounted, of which in 1 only two are shown. The axes of rotation of the interaction with the wedges 18 provided bolt 30 are aligned orthogonal to the axis A in this embodiment. At the in 1 illustrated embodiment, each bolt 30 formed by a sleeve which is rotatably mounted on a rotationally fixed in Bolzenträger 26 arranged arranged axis is.

At the radially inner peripheral surface of the bolt carrier 26 is an electric motor 32 attached, as the electric actuator of the disc brake 10 serves and an output pinion 34 having, at a radially inner periphery of the first carrier ring 14 trained gearing 36 is engaged.

On the first carrier ring 14 opposite side of the brake disc 12 is at a axial distance to this a second carrier ring 38 also parallel to the brake disc and arranged coaxially to the axis A. This second carrier ring 38 is on his brake disc 12 facing side with friction members 16 ' provided with the friction members 16 at least substantially matching locations on the second carrier ring 38 are attached and also during braking to the brake disc 12 invest.

In a radially outer region of the disc brake 10 are several saddles 40 arranged, which the bolt carrier 26 , the first carrier ring 14 , the brake disc 12 and the second carrier ring 38 overlap and with radially inwardly projecting arms 42 on the one hand on the axially outer end face of the bolt carrier 26 and on the other hand on the axially outer end face of the second carrier 38 or support a connected member.

The electric motor 32 is via a connection line 44 with a control unit 46 connected, which is supplied in a manner not shown, as well as signals from the brake pedal of the driver receives an operation thereof and can output signals to the cockpit of the driver. The current braking torque M _B can be detected by means of a torque sensor, not shown. To determine the friction member position θ _M , the motor travel traveled from a starting position is monitored, for example in the form of the number of engine revolutions performed. The control unit 46 further comprises a memory for storing the detected values.

It will now be explained the function of the illustrated brake system, assuming that the brake disc 12 turns in the direction of the arrow ω. This direction of rotation corresponds to a disc brake installed in a vehicle 10 a forward drive. To initiate a braking process, the electric motor 32 energized and then drives the output pinion 34 such that the first carrier ring 14 by an angle φ in the direction of rotation ω relative to the rotationally fixed bolt carrier 26 twisted. This causes the first surfaces 20 the wedges 18 on the associated bolts 30 accumulate, causing the first carrier ring 14 axially to the brake disc 12 is shifted so that the friction members 16 to the brake disc 12 invest. In other words, the friction members shift 16 starting from a starting position on the brake disc 12 and engage with this. The friction member position resulting from such an axial displacement of the carrier ring 14 is determined by the formula: θ = φ / (2π × P) (8), where φ is the angle of rotation and P is the slope of the first surface resulting from the pitch angle α 20 is.

After the friction members 16 to the brake disc 12 created, causes the resulting reaction force on the friction members 16 , the first carrier ring 14 , the bolt carrier 26 and the saddles 40 also an axial displacement of the second carrier ring 38 to the brake disc 12 out, so that the friction members 16 ' with almost no delay also to the brake disc 12 create (floating saddle principle).

The with the bolt 30 interacting wedges 18 represent a self-reinforcing arrangement, ie that of the electric motor 32 over the output pinion 34 in the disc brake 10 introduced frictional force is amplified automatically and without further forces to be introduced from the outside.

For further operation of in 1 The disc brake shown is further to the detailed description of DE 198 19 564 C2 directed.

wobei

μ_B

der Reibwert zwischen Bremsbelag und Bremsscheibe des Bremssystems,

r_B

der effektive Radius der Bremse,

k*

die Steifigkeit des Bremssystems,

α

der Keilwinkel und

L

die Spindelsteigung des Aktuators sind.

If you look at 2 Thus, one recognizes a diagram representing the relationship between the braking torque M _B and the Reibgliedposition θ _M for different states of the brake. The curve 50 shows the course of the braking torque M _B over the current friction member position θ _M at cold brake and low friction coefficient μ _cold . After initially flat course, the curve increases 50 _cold with the slope g. The curve 52 on the other hand shows the course of the braking torque M _B over the current Reibgliedposition θ _M with warm brake and thus with increased coefficient of friction μ _warm . After also initially flat course, the curve increases 52 with respect to the slope of the curve 50 greater slope ĝ _warm . The gradients are generally calculated according to the formula:

in which

μ _B

the coefficient of friction between the brake lining and the brake disk of the brake system,

r _B

the effective radius of the brake,

k *

the rigidity of the braking system,

α

the wedge angle and

L

the spindle pitch of the actuator are.

Both curves 50 and 52 start from a respective contact position θ ₀ , in which the first mechanical contact between the friction members 16 and the brake disk, and extending to a state in which the friction members 16 strong on the brake disc 12 are pressed.

How out 2 shows that at a certain Reibgliedposition θ scored braking torque M _B in the case of a warm brake curve 52 significantly higher than that achieved at the same friction member position θ with cold brake braking torque. This must be taken into account when controlling the brake, in particular when controlling the braking effect in the context of an anti-lock braking system or stability program of a vehicle.

On the other hand, you look at it 3 , so you recognize again two curves, namely the curve 54 , which shows the course of the braking torque M _B over the friction member position θ _M when the brake is cold, and the curve 56 , which represents the course of the braking torque M _B over the friction member position θ _M with a warm brake. 3 shows the curves of the braking torque in the event that "fading" occurs during braking. "Fading" is generally used to describe the phenomenon in which outgassing occurs on the brake pad, in particular due to the heating of binding materials contained in the brake pad. These outgassing results in a "gasplaning effect" comparable to "aquaplaning", which ultimately results in a decrease in the coefficient of friction.

According to the in 3 In the illustrated case, the curve representing the state of the cold brake first runs 54 - similar to in 2 already shown - below the curve representing the state of the warm brake 56 However, due to the greater slope, it then approaches and finally crosses it at the friction member position θ _k . As a result, the curve representing the state of the cold brake runs 54 above and with a greater gradient in relation to the curve representing the state of the warm brake 56 ,

2 and 3 show that it is necessary due to the strong fluctuations of the coefficient of friction to get an idea about the size of the current coefficient of friction μ _B for controlling the brake with sufficient control quality.

If one starts by estimating the behavior of the brake initially from measured values for the braking torque and the corresponding friction element position, it is difficult to estimate the development of the braking torque from this. 4 shows a fundamental problem of a determination of value pairs of braking torque and Reibgliedposition. If one starts from a contact position (θ _0, M ₀₎ by the pair of values is given and recorded in the sequence in a relatively narrow area (θ ₁ ... θ _i) of various Reibgliedpositionen the corresponding braking torque, is obtained due to Disturbs a variety of relatively strongly scattered points in the area 58 are shown. The fluctuations can result, for example, from inaccuracies in the production and in the assembly of the brake but also from measurement errors. Due to the strong fluctuations, when using individual points for the determination of the braking torque curve, significant deviations from the actual braking torque curve can occur. It should be noted that the closer the pair of values (θ ₀ , M ₀ ) to the area, the larger the measured perturbations 58 lies. By temporal filtering, it is possible to reduce these disturbances and then use a value pair closer to this range. As a result, a better approximation of the nonlinear stiffness can be obtained.

To counter this problem shows 5 a possible approach. According to 5 For example, a plurality of value pairs are detected, each pair of values (θ _M , M _B ) being represented by a point P. is. The individual points are detected at a sufficiently large time interval and at sufficiently different friction element positions θ, in order to thus reduce the sensitivity to disturbances. One recognizes in 5 in that, first of all, by varying the friction member position θ in the course along the points P ₁ to P _7, the braking torque is greatly increased. The resulting curve 60 is due to the increasing heating of the brake and the associated increase in friction and contact position shift ever steeper. Finally, the braking torque along the curve 62 degraded relatively quickly according to points P ₇ 'to P ₃ '. In order now to determine the slope of the braking torque curve for the current point P _currently and thus to be able to estimate the current behavior of the brake, it is of considerable importance to use the correct points in the estimation. If one starts, for example, from the starting point P ₁ - for example, the contact position, one arrives at a slope corresponding to the straight line 66 , which obviously runs much steeper than the curve 62 , On the other hand, assuming the arbitrarily chosen point P ₅ , one arrives at a slope corresponding to the straight line 64 , which obviously runs much flatter than the curve 62 , For the estimation of the actual braking torque curve, therefore, those points should be used which were detected relatively soon before the point P _{currently to be determined} . In the case illustrated, these are the points P ₇ 'to P ₃ '.

Another application of the invention is in 6 shown. According to 6 The braking torque is built up relatively quickly - as by a curve 68 shown - and then held constant - as by curve 70 shown. While the braking torque is kept constant, increases the temperature of the friction lining and the overall arrangement by the applied friction energy, which on the one hand changes the coefficient of friction and on the other hand shifts the contact position by the thermal expansions occurring. To be able to keep the braking torque constant despite these changed operating parameters, it is necessary to change the friction lining position, as indicated by the arrow of the curve 70 shown. At the beginning of in 6 braking shown, the individual detected value pairs can still be used for the determination of the braking torque curve and thus the coefficient of friction. In order to take into account the problem of displacement of the contact position and friction coefficient increase, the new contact positions θ _{0 1} and θ _{0 2 are} estimated in an embodiment of the invention in the state of the holding constant braking torque based on the temperature changes of the friction members and the associated thermal dimensional changes. The temperature changes can be measured directly or determined from other measurable parameters, such as the braking torque and the delay achieved and the wheel speed. In the points Z ₁ and Z ₂ , the respective values of ĝ are then determined with the respective contact positions θ _{0 1} and θ _{0 2} .

7 shows in a simplified flowchart the individual steps of an embodiment of the method according to the invention. This example performs a plausibility test that compares the real system to a system model. It should be noted that such a plausibility test could also be performed by checking the expected relationship between ĝ and the coefficient of friction, or, for example, by evaluating the reliability of the estimate based on the estimated temperature difference set since the points P were detected Has.

In step S1, the individual points (value pairs) P (see FIG. 5 ) and stored - this can be done at any opportunity, eg when applying the brake. At each time step of the control loop, the braking torque and the operating position are now detected (step S2), and possibly other parameters that are needed for the different estimates. Thereafter, in step S3, a starting point P _{A is} selected, which serves as the basis for an estimation. The decision as to which point to use is made taking into account both the actual position and moment difference between the point and the detected operating point, as well as the timing of the points taken. Be on this 5 and referenced above.

In step S4, the results of the previous time step are integrated or calculated to determine new values based on the system model. In this step it is also possible to initialize the parameters. Thereafter, in step S5, parameter comparisons are made between the real system (s), and the ideal system, and possibly plausibility tests. If the results are within a selected tolerance, then a corresponding brake torque is estimated in step S6, which is used to calculate the derivatives of the parameters in step S7. Finally, in step S8, the controller is compensated according to the estimated gain factor ĝ _i .

If the comparison in step S5 leads to a negative result, ie if the comparison results are outside the selected tolerance, the estimation is corrected accordingly in step S9, and the starting point either corrected or newly selected. Optionally, a braking operation can be triggered in step S10, so that the points P (value pairs) can be re-detected.

The points P are thus constantly corrected or tracked, as already mentioned above and with reference to 8th will be explained below.

P₁ → P_N

Punkte (Wertepaare) 1-N, z.B.: (θ_i, M_i) oder (θ_i, dv_i/dt) oder (θ_i, dV_Fzg/dt) Oder (θ_i, F_Zuspann)

θ_i

gemessene Position, Zeitschritt i

M_i

gemessenes Moment, Zeitschritt i

Ṁ_i

gemessene Ableitung des Moments, Zeitschritt i

T_i

gemessene Bremstemperatur, Zeitschritt i

i_i

gemessener Motorstrom, Zeitschritt i

ω_i

gemessene Radgeschwindigkeit, Zeitschritt i

P_A

Ausgangspunkt für die Schätzung (ein Punkt von P₁ → P_N)

ĝ_i

geschätzter Verstärkungsfaktor, Zeitschritt i

μ ^_i

geschätzter Reibungskoeffizient, Zeitschritt i geschätzte Temperaturen (1 → M) diskreter Bremsenbauteile, Zeitschritt

T ^_(1:M)i

i

θ_0i

geschätzter Kontaktpunkt, Zeitschritt i

berechnete Momentenunterschiede für einen Bremsvorgang zur Ermittlung des Verstärkungsfaktors und der Verschiebung des Kontaktpunkts, Räder (1 → J)

In the 7 mentioned parameters are defined as follows:

P ₁ → P _N

Points (value pairs) 1-N, eg: (θ _i , M _i ) or (θ _i , dv _i / dt) or (θ _i , dV _Fzg / dt) Or (θ _i , F _Zuspann )

θ _i

measured position, time step i

M _i

measured moment, time step i

_I

measured derivative of the moment, time step i

T _i

measured brake temperature, time step i

i _i

measured motor current, time step i

ω _i

measured wheel speed, time step i

P _A

Starting point for the estimate (a point from P ₁ → P _N )

_i

estimated gain factor, time step i

μ ^ _i

estimated friction coefficient, time step i estimated temperatures (1 → M) of discrete brake components, time step

T ^ _{(1: M) i}

i

θ _0i

estimated contact point, time step i

calculated torque differences for a braking process to determine the gain factor and the displacement of the contact point, wheels (1 → J)

8th FIG. 12 is a flowchart for determining the correction points to be used for estimation using the least squares method. In step S12, the individual points (value pairs) P (see FIG. 5 ) and stored - this can be done at any opportunity, eg when applying the brake. At each time step of the control loop, the braking torque M _i and the operating position θ _i are detected according to step S13. Subsequently, the detected values are used in step S14 in the well-known least squares algorithm. It is also possible to use only every second or fourth point, for example. Furthermore, it may be advantageous to multiply the stored data with a weighting factor, in order to weight values whose detection has been in use for a relatively long time less than values recently acquired. This allows a less sluggish estimate to be achieved.

The algorithm calculates an approximation and other factors such as the variance of the data and the "statistical confidence." The latter factors are used in step S15 to decide if the approximation is reliable Correspondingly corrected points in step S16 and the method according to 7 made available. If the approximation is incorrect, more data will be collected and the steps according to 8th repeated until a sufficient approximation has been achieved.

The in 8th The process shown may run permanently in the background in order to set the value pairs for the compensation ( 7 ) to correct.

Claims (25)

Method for compensating a change in the transmission behavior of an electromechanical brake system caused by a change in at least one operating parameter, in particular friction coefficient (μ _B ) or / and contact position (θ ₀ ) or / and stiffness (k *) ( 10 ), in particular an electromechanical brake system with self-boosting, comprising the steps of: a) detecting (S1, S2, S3) the operating position of the brake system determining operating position characteristic (θ ₀ ) in a first operating position of the brake system, b) detecting (S1, S2 , S3) of the braking effect of the brake system characterizing braking effect characteristic (M ₀ ) in the first operating position of the brake system, c) detecting (S1, S2, S3) of the operating position of the brake system determining operating position characteristic (θ _M ) in at least one other Operating position of the brake system; d) detecting (S6) a braking effect characteristic (M _B ) characterizing the braking effect of the brake system in the at least one further operating position of the brake system and e) compensating (S8) a change of the at least one operating parameter taking into account recorded operating position characteristics (θ ₀ , θ _M ) and braking performance characteristics (M ₀ , M _B ) of the first and the at least one other operating position. Method according to claim 1, characterized in that that the operating position characteristic, the friction lining position (θ) or a characterizing this parameter Is worth. Method according to claim 2, characterized in that the braking system ( 10 ) with a friction pad displacing the electric actuator ( 32 ), wherein the operating position characteristic (θ) is the actuator position of the electric actuator ( 32 ) or a value characterizing this characteristic. Method according to one of the preceding claims, characterized in that the braking effect characteristic is the braking torque (M _B ), the braking deceleration or the wheel slip or the clamping force or a value characterizing these characteristics. Method according to one of the preceding claims, characterized in that the brake system ( 10 ) is designed as a floating caliper brake with self-boosting effect, the a wedge assembly ( 18 ) and / or its actuator ( 32 ) is formed with screw drive. A method according to claim 5, characterized in that the changing operating parameter based on the assumption of a linear relationship of actuator position (Θ) and braking torque (M _B ) is determined according to the equation:

where the variables M _{B are} the actual braking torque, μ _{B is} the coefficient of friction between the brake lining ( 16 ) and brake disc ( 12 ) of the braking system ( 10 ), r _{B is} the effective radius of the brake, k * the stiffness of the brake system, α the wedge angle, L the spindle pitch of the actuator, θ _M the current actuator position, and θ ₀ the actuator position at the contact position of the brake system. A method according to claim 6, characterized in that for determining the changing operating parameter, in particular the coefficient of friction (μ _B ) and / or the contact position (θ ₀ ) and / or the stiffness (k *), the braking torque M _B at the first actuator position θ _M , the contact position or a different from the contact position predetermined operating position of the brake system ( 10 ), and at the at least one further operating position deviating from the contact position or the predetermined operating position, it is detected that the difference ΔM _{B of} the detected braking torque values and the detected actuator positions Δθ _{M is} calculated in each case and that the calculated differences .DELTA.M _B and .DELTA..theta. _M changing operating parameters, in particular the coefficient of friction (μ _B ) or / and the contact position (θ ₀ ) or / and the stiffness (k *), is determined according to the equation

wherein the sizes .DELTA.M _B the difference between the detected braking torque values, Δθ _M, the difference of the detected actuator positions, μ _B of the coefficient of friction between the brake lining and the brake disc of the brake system, r _B, the effective radius of the brake, k *, the rigidity of the brake system α, the wedge angle and L the spindle pitch of the actuator are. A method according to claim 6, characterized in that for determining the changing operating parameter, in particular the coefficient of friction (μ _B ) and / or the contact position (θ ₀ ) and / or the stiffness (k *), the braking torque M _B and the corresponding actuator position θ _M , which deviates from the contact position, that, furthermore, when determining the changing operating parameter, an actuator position θ _{0 of} the Brake system is taken into account, which corresponds to the contact position or a deviating from the contact position predetermined operating position of the brake system, and that on the basis of the variables considered the changing operating parameters, in particular the coefficient of friction (μ _B ) and / or the contact position (θ ₀ ) and / or Stiffness (k *) is determined according to the equation

where ĝ new an estimate of the expression

represents, ĝ old is a known previously detected value of ĝ, M _{B is} the detected brake torque, θ _{M is} the corresponding actuator position, θ _{0 is} the actuator position at the contact position or a predetermined operating position of the brake system deviating from the contact position, K _{est is} the gain factor Estimate is, μ _{B is} the coefficient of friction between the brake pad and brake disc of the brake system, r _{B is} the effective radius of the brake, k * is the rigidity of the brake system, α is the wedge angle and L is the spindle pitch of the actuator. A method according to claim 7 or 8, characterized in that a plurality of pairs of values (M _Bi , θ _Mi ) from braking torque M _B and actuator position θ _M are detected and for estimating the changing operating parameter, in particular the coefficient of friction μ _B or / and the contact position (θ ₀ ) and / or stiffness (k *). Method according to one of claims 7 to 9, characterized that in one of the components of the braking system during its Operating temperature gradient that affects the braking behavior, and a resulting dimensional change of the component in the Estimate considered becomes. Method according to one of claims 7 to 10, characterized in that for a first estimate of the braking effect of the brake system characterizing braking effect characteristic for the operating parameter of a predetermined coefficient of friction, for example, from μ _B = 0.5, is assumed. Method according to one of claims 7 to 11, characterized in that the ratio of a determined coefficient of friction μ _B and the independently estimated expression ĝ is monitored and the ratio of the plausibility of the estimate of the expression ĝ is checked. A method according to claim 12, characterized in that the coefficient of friction μ _{B is} determined based on the relationship

where F _{B is} the braking force resulting from the current braking torque, F _{A is} the driving force exerted on the actuator, and α is the wedge angle. Method according to one of claims 7 to 13, characterized in that when changing the braking torque M _B and actuator position θ _M, the ratio

is calculated and compared with the expression ĝ, preferably using the method of least squares for the correction of detected reference points, in particular detected values of braking torque M _B and actuator position θ _M. Method according to one of Claims 7 to 14, characterized in that the braking torque M _{B wheel} and the actuator position θ _{M wheel are} changed by _wheel , the total braking torque being kept constant over all the wheels of the motor vehicle. Method according to one of claims 7 to 15, characterized in that a friction member contact position (θ ₀ ) of the brake system based on pairs of values of the braking action characterizing size, in particular the current braking torque (M _B ) or the braking torque (M _B ) determining size , and a size characterizing the operating position, in particular the current actuator position (θ _M ), is determined. Method according to claim 16, characterized in that that - one first value pair upon reaching a predetermined fraction of a Nominal value of a characterizing the braking effect, in particular a nominal braking torque, is detected, - at least a further value pair which differs from the first value pair is detected, - out the determined value pairs a regression line is determined, the one connection between the braking effect characterizing Size, in particular the braking torque or the braking torque determining size, and the the braking effect characterizing size, in particular the actuator position, describes, and - out the regression line is a theoretical friction member contact position is determined, wherein the at least one friction member with the at least one component to be braked just comes into contact. A method according to claim 17, characterized in that the theoretical friction member contact position (θ ₀ ), wherein the at least one friction member with the at least one component to be braked ( 12 ), it is determined from the regression line on the assumption that at the theoretical friction member contact position (θ ₀ ), the braking torque (M _B ) is zero. Method according to one of the preceding claims, characterized in that the braking system is controlled as a controlled system via a controller, wherein in step e) an amplification factor of the controlled system for compensating (S8) a change in the operating parameter, in particular the coefficient of friction (μ _B ) and / or the contact position (θ ₀ ) and / or the stiffness (k *), taking into account the detected operating position characteristics (θ ₀ , θ _M ) and braking performance characteristics (M ₀ , M _B ) of the first and the at least one other operating position changed becomes. Method according to one of the preceding claims, characterized characterized in that the state of wear of the brake system, in particular of the at least one friction lining, in the determination the stiffness (k *) taken into account becomes Brake system for controlling / regulating a brake ( 10 ), in particular for carrying out the method according to one of the preceding claims, wherein the brake ( 10 ) at least one friction member ( 16 ) and at least one rotating component to be braked ( 12 ), wherein further to achieve a braking effect, the at least one friction member ( 16 ) against the at least one rotating, braked component ( 12 ), and wherein an operating position characteristic detecting means, in particular a position detecting means, for detecting a current friction member position characteristic operating position characteristic (θ ₀ ) of the brake system, a braking effect detecting means for detecting the current braking torque (M _B ) or the current braking torque (M _B ) determining braking effect characteristic and a control unit ( 46 are provided, characterized in that the operating position characteristics detecting means in a first and in at least one further operating position of the brake system detects an operating position of the brake system determining operating position characteristic (θ ₀ , θ _M ) that the braking effect detecting means in the In the first operating position of the brake system, a brake action characteristic (M ₀ ) characterizing the braking effect of the brake system detects that the control unit based on the detected values of the operating position characteristic (θ ₀ , θ _M ) and the braking effect characteristic (M _B ) has a value the braking effect characteristic variable (M _B ) characterizing the braking effect of the brake system is detected in the at least one further operating position (θ _M ) of the brake system and in that the control unit effects a change in the transmission behavior of the brake caused by a change in an operating parameter, in particular the coefficient of friction (μ _B ) or / and the contact position (θ ₀ ) or / and the stiffness (k *), taking into account the acquired operating position characteristics ( θ ₀ , θ _M ) and brake performance characteristics (M ₀ , M _B ) of the first and the at least one further operating position compensated. Braking system according to claim 21, characterized in that the brake ( 10 ) is designed as an electromechanical brake, wherein the at least one friction member ( 16 ) by means of an electromechanical drive ( 32 . 34 . 36 ) against the at least one component to be braked ( 12 ) is depressible. Braking system according to claim 22, characterized in that the electromechanical brake ( 10 ) an arrangement ( 18 . 30 ) for self-amplification of the electromechanical drive ( 32 . 34 . 36 ) on the at least one friction member ( 16 ) has exerted frictional force. Braking system according to one of claims 21 to 23, characterized in that the control unit ( 46 ) for determining the current friction member position (θ) the drive movement of the electromechanical drive ( 32 . 34 . 36 ) detected. Brake system according to one of claims 21 to 24, characterized in that the braking effect detecting means for determining the current braking torque (M _B ) is formed.