Method for estimating the brake torque and / or pressure applied to a brake system using a friction map - Patents.com

Abstract

A method for estimating a brake torque of a brake system and / or a pressure applied to the brake system using a friction map. A method for estimating a brake torque of a brake system of a vehicle during a driving condition is described. The method includes a step (a) of detecting or calculating a first input quantity and a second input quantity representative of an operating condition of the brake system. The detected or calculated first input quantity includes a temperature T of a brake disc of the brake system. The detected or calculated second input quantity comprises a quantity dependent on a pressure P of the brake system or a contact pressure PC between friction surfaces of the brake system. The method then includes a step (b) of determining, based on the detected or calculated first input quantity and the second input quantity, a brake friction coefficient μ representative of expected brake friction or efficiency under conditions defined by the detected or calculated values ​​of the first input quantity and the second input quantity. The determining step (b) is performed by electronic processing by referring to a digitally stored predefined friction map or a corresponding predefined friction map table. The method finally includes a step (c) of estimating a brake torque C based on the determined brake friction coefficient μ and geometrical and / or structural and / or operating parameters of the brake system. Additionally, a similar method for estimating the pressure to be applied to a vehicle's braking system to obtain a target brake torque value, and a method for actuating a brake-by-wire (BBW) braking system are described.

Description

[Technical field]

[0001] The present invention relates to a method for estimating the braking torque of a braking system using a friction map.

[0002] The present invention also relates to a similar method for estimating the pressure applied to a braking system using a friction map.

[0003] The general technical field of the invention is therefore that of estimating, by electronic processing, quantities related to the operation of a braking system on the basis of measured or detected operating parameters. [Background technology]

[0004] Until relatively recently, characterization of the friction occurring on vehicle brake discs during braking was performed exclusively by experimental test cycles, each of which was referenced to specific operating conditions and / or situations, or as a function of disc temperature.

[0005] Such methodologies suffered from the obvious and important drawback of not providing estimates of friction for all possible operating conditions different from those experimentally tested, which implied the further drawback of having to carry out specific characteristic tests for each operating condition of interest.

[0006] To partially solve this problem, more general models have been introduced, from which meaningful estimates of friction can be obtained for a wide range of possible operating conditions, each associated with specific critical values ​​of the variables of interest (e.g. the temperature of the brake disc and the pressure applied to the brake disc).

[0007] The results of these models are typically reported in the form of tables (or "friction maps") that can be referenced to make estimates of brake disc friction under different operating conditions.

[0008] This friction estimate is useful for estimating other important operating quantities of the braking system, such as the braking torque, or the pressure that must be applied to the brake discs to obtain a certain braking torque.

[0009] In this regard, the prior art does not provide an automatic solution that is adaptable to multiple driving conditions (ideally usable under any driving conditions), usable in real time while the brake system is operating, and provides reliable results.

[0010] As such, there remain many unmet needs in these areas, needs for which the currently known solutions do not provide a sufficiently effective solution. Summary of the Invention

[0011] The object of the present invention is to provide a method for estimating the braking torque of a braking system, which makes it possible to at least partially avoid the above-mentioned drawbacks with reference to the prior art and to meet the aforementioned needs which are particularly felt in the technical field considered. Such an object is achieved by a method according to claim 1.

[0012] Further embodiments of such a method are defined in claims 2-15.

[0013] It is also an object of the present invention to provide a method for estimating a quantity related to the operation of a vehicle brake system. Said object is achieved by a method according to claim 16.

[0014] Further embodiments of such a method are defined in claims 17-18.

[0015] It is also an object of the present invention to provide a method for estimating the pressure applied to a brake system of a vehicle. Such an object is achieved by a method according to claim 19 and by a method according to claim 26.

[0016] Further embodiments of such a method are defined in claims 20-25 and 27.

[0017] Finally, it is also an object of the present invention to provide a method for actuating a braking system installed in a vehicle equipped with brake-by-wire, using the method described above. Said object is achieved by a method according to claim 28. [Brief description of the drawings]

[0018] Further characteristics and advantages of the method according to the invention will become apparent from the following description of preferred embodiments, given in a non-limiting manner with reference to the attached drawings, in which:

[0019] [Figure 1] FIG. 1 is a simplified flow diagram of the steps involved in an embodiment of a method for estimating braking torque of a braking system encompassed by the present invention.

[0020] [Diagram 2] FIG. 2 is a simplified flow diagram of steps included in an embodiment of a method for estimating quantities related to the operation of a braking system for a vehicle, as encompassed by the present invention.

[0021] [Diagram 3] FIG. 3 is a simplified flow diagram of steps involved in an embodiment of a method encompassed by the present invention for estimating pressure to be applied to a vehicle's braking system to obtain a target brake torque value CT.

[0022] [Figure 4] FIG. 4 is a simplified flow diagram of the steps involved in another embodiment of a method for estimating the pressure to be applied to a vehicle's braking system to obtain a target brake torque value CT.

[0023] [Diagram 5]FIG. 5 is a simplified flow diagram of the steps involved in another embodiment of a method for actuating a vehicle's brake-by-wire braking system using the methods described above.

[0024] [Figure 6A] FIG. 6A shows an example of a direct friction map used in an embodiment of the method according to the invention. [Figure 6B] FIG. 6B shows an example of a direct friction map used in an embodiment of the method according to the invention.

[0025] [Figure 7] FIG. 7 shows an example of a look-up table that corresponds to a direct friction map.

[0026] [Figure 8] FIG. 8 shows an example of a friction map used in an embodiment of the method according to the invention.

[0027] [Figure 9] FIG. 9 shows an example of the calculation of an inverse friction map from a direct friction map.

[0028] [Figure 10] FIG. 10 shows an example of a look-up table that corresponds to an inverse friction map.

[0029] [Figure 11A] FIG. 11A is a diagram of a "brake-by-wire" braking system in which the method of FIG. 5 can be applied. [Figure 11B] FIG. 11B is a diagram of a "brake-by-wire" braking system in which the method of FIG. 5 can be applied. [Figure 11C] 11C is a diagram of a "brake-by-wire" brake system to which the method of FIG. 5 can be applied.

[0030] [Figure 12] FIG. 12 illustrates the use of a friction map in the context illustrated by FIGS. 11A-11C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] A method for estimating the brake torque of a vehicle brake system in a driving state will be described with reference to Figs.

[0032] The method includes the step (a) of sensing or calculating first and second input quantities representative of operating conditions of the brake system.

[0033] A first sensed or calculated input quantity comprises the temperature T of the brake disc of the braking system.

[0034] A second sensed or calculated input quantity includes a quantity dependent on the pressure P of the braking system or on the contact pressure PC between the friction surfaces of the braking system.

[0035] The method then includes the step (b) of determining, based on the detected or calculated first and second input quantities, a brake friction coefficient μ representative of expected brake friction or efficiency under conditions defined by the detected or calculated values ​​of the first and second input quantities.

[0036] Such determining step (b) is performed by electronic processing by referencing a digitally stored predefined friction map, or a corresponding predefined friction map table.

[0037] The method finally comprises a step (c) of estimating the braking torque C on the basis of said determined braking friction coefficient μ and on geometrical and / or structural and / or operational parameters of the braking system.

[0038] According to different possible embodiments of the method, said second input quantity is any one of the following quantities: Brake system pressure P; Contact pressure PC between the friction surfaces of the brake system; the pressure P of the braking system multiplied by the rotational speed v of the wheel on which the braking system acts; or The product of the contact pressure PC between the friction surfaces of a braking system and the rotational speed vr of the wheel on which the braking system acts.

[0039] According to an embodiment, the method is performed with reference to a brake system including at least one brake caliper and at least one brake disc, said friction surfaces of the brake system being a surface of the disc of the brake system and a surface of a pad of the brake caliper, configured to come into contact with each other during a braking event.

[0040] In this case, the aforementioned rotational speed vr is the rotational speed of the wheel on which the brake disc and brake caliper of the brake system act.

[0041] According to an embodiment of the method, the detecting or calculating step (a) includes detecting the first input quantity and the second input quantity based on real-time acquisition of said quantities during operating conditions of the braking system.

[0042] According to another embodiment, the detecting or calculating step (a) includes calculating the first and second input quantities offline based on remotely acquired data related to operating conditions of the brake system.

[0043] According to an embodiment of the method, the friction map table comprises a predefined look-up type table indicating a brake friction coefficient μ as a function of the first input quantity and the second input quantity.

[0044] In that case, the determining step (b) comprises determining the brake coefficient of friction μ based on readings and / or interpolations performed on said look-up table by electronic processing.

[0045] According to an embodiment, said friction map comprises a predefined color friction map illustrating by color graphics the brake friction coefficient μ as a function of the first and second input quantities.

[0046] In that case, the determining step (b) includes determining the braking coefficient of friction μ based on reading such a color map.

[0047] According to an embodiment, the aforementioned geometric and / or structural and / or operational parameters of the brake system used in the method of estimating step (c) include geometric parameters related to the pistons of the brake caliper and operational parameters of the brake caliper.

[0048] According to the embodiment, the brake torque C is determined by the friction coefficient μ and the area A of the piston of the brake caliper. PisT (both sides) and the effective radius R of the brake caliper eff and the brake caliper system pressure P imP It is calculated as the product of multiplication by

[0049] C = μ A PisT ·R eff P imP

[0050] According to an embodiment of the method, one or more friction maps constructed based on empirical evaluation, or one or more corresponding friction map tables, are stored in a control unit of the vehicle or vehicle brake system.

[0051] Each such friction map or maps, or corresponding friction map tables or tables, is characterized by respective specific first and second input quantities, each expressed in respective units of measurement.

[0052] According to an alternative embodiment, the method further comprises the step of preparing the first and second input quantities based on the particular first and second input quantities provided by the particular friction map or corresponding friction map table among those stored and the detected and / or measured quantities provided to the control unit as a function of the respective units of measurement, which are used in the determining step (b).

[0053] According to an embodiment, the aforementioned step of preparing the input quantity comprises adapting the measurement units of the detected quantity to the measurement units provided in the friction map used, or in a corresponding friction map table.

[0054] According to certain embodiments, the step of preparing the input quantities further comprises calculating the first and / or second input quantities based on the obtained quantities in a manner consistent with the provisions of the friction map used, or a corresponding friction map table.

[0055] In other words, if, for the particular friction map used, there is no immediate consistency between the obtained quantities and the provided quantities, or between the units of measurement of the obtained quantities and the units of measurement for which the map was constructed, the method includes a step of pre-processing the input quantities to determine such consistency.

[0056] Those skilled in the art will readily appreciate that such steps may be applied in many different instances.

[0057] For example, if the speed is obtained in Km / h but the map is built based on rotational speed or wheel revolutions, the method includes a step of preparing an input quantity used to refer to a map consisting of a transformation in which linear speed in Km / h is converted to rotational speed taking into account the rolling radius.

[0058] Or, again by way of example, if the obtained quantity is the brake pressure of a braking system and the friction map has been built based on the pressure on the brake pads, the method includes a step of preparing an input quantity used to refer to a map consisting of a transformation that multiplies the system pressure by the area of ​​the piston of the brake caliper supporting the brake pads and divides by the area of ​​said pads to obtain the associated contact pressure.

[0059] According to another embodiment, also in a different way, in order to ensure consistency between the obtained quantities and the quantities used to refer to the friction map, the method comprises providing, by the control unit, a friction map or a corresponding modified friction map table based on the actually obtained quantities and their respective units of measurement.

[0060] For example, according to a possible embodiment, if different units of measurement are used, various friction maps are constructed by changing the units of measurement (eg, on both the x-axis and the y-axis).

[0061] According to an embodiment, the method is performed on a brake system including a plurality of brake calipers and respective brake discs, and steps (a), (b) and (c) of the method are performed for each of the plurality of brake calipers and respective brake discs.

[0062] According to an embodiment, the brake friction coefficient μ is determined for each axle of the braking system, i.e. a single brake friction coefficient value μ is determined for both the brake caliper and the respective brake disc of an axle.

[0063] According to an embodiment, the brake friction coefficient μ is determined for each brake caliper and each brake disc of an axle.

[0064] In other words, in different possible embodiments, the coefficient of friction can be calculated based on available inputs at both the axle level (a single value for both the front or rear brakes) and at the corner level (so the coefficient of friction value for the right brake may also be different from the coefficient of friction value for the left brake on the same axle).

[0065] According to an embodiment, all steps of the above-mentioned embodiment of the method for estimating the brake torque are performed by electronic processing means.

[0066] A method for estimating quantities related to the operation of a vehicle's braking system is described below.

[0067] Such a method includes performing a method for estimating a braking torque of a braking system according to any one of the previously described exemplary embodiments, and then estimating at least one further quantity related to the operation of the braking system based on the estimated braking torque and further detected or measured operating parameters.

[0068] According to different embodiments of such a method, said at least one further quantity related to the operation of the brake system comprises: The power or energy dissipated during braking, and / or aerodynamics or other parameters related to vehicle dynamics; and / or Brake temperature, and / or Adjustment parameters for brake-by-wire (BBW) type brake systems.

[0069] According to an embodiment, the power dissipated during braking is estimated by multiplying the estimated brake torque by the wheel speed.

[0070] According to an embodiment, the aforementioned estimated power dissipated during braking is used in conjunction with a thermal model to estimate the temperature of the brakes or other components of the wheel braking system.

[0071] According to another embodiment, aerodynamic drag or other parameters related to the vehicle dynamics are estimated based on the estimated braking torque and the detected or calculated traction torque of the vehicle.

[0072] According to another embodiment, based on an estimated brake torque of an axle that is directly controlled by a driver in a brake-by-wire (BBW) actuation system, at least one brake torque target for at least one respective other axle of the brake-by-wire actuation system is estimated.

[0073] According to an embodiment, all the steps of the above-mentioned embodiment of the method for estimating quantities related to the operation of a braking system are executed by electronic processing means.

[0074] A method, also encompassed by the present invention, for estimating the application pressure P to be applied to the vehicle's brake system in order to obtain a target brake torque value CT will now be described.

[0075] Such a method includes the steps of (i) detecting or calculating a temperature T of a disc brake of a brake system, and (ii) determining a pressure P to be applied to the brake system based on said temperature T of the brake disc and said target brake torque value CT.

[0076] The determining step (ii) is performed by electronic processing, by reference to a digitally stored predefined inverse friction map, or a corresponding predefined inverse friction map table.

[0077] According to an embodiment, said inverse friction map or a corresponding inverse friction map table is calculated from the friction map or the corresponding friction map table and stored prior to carrying out the steps of the method.

[0078] According to an embodiment of the method, the inverse friction map table comprises a predefined look-up inverse table indicating the pressure P applied to the brake system as a function of the temperature T of the brake disc and the brake torque C.

[0079] The determining step (ii) then consists of determining the pressure P to be applied to the brake system based on readings and / or interpolations carried out by electronic processing against said look-up inverse table.

[0080] According to an embodiment, the inverse friction map table comprises a predefined look-up inverse table that provides an output value PV equal to the product of the pressure P to be applied to the brake system multiplied by the speed of the wheels acting on the brake system as a function of the temperature T of the brake disc and the brake torque C.

[0081] In this case, the determining step (ii) comprises the following steps: - obtaining said output value equal to the product of the pressure P applied to the brake system and the wheel speed by reading and / or interpolating said look-up inverse table by electronic processing; Detecting or calculating the wheel speed in the current driving conditions; Calculating the pressure P to be applied to the brake system based on the output value PV obtained from the inverse table and on the detected or calculated wheel speeds.

[0082] Depending on the embodiment, the detected or calculated velocity of the wheel is the angular velocity ωr of the wheel.

[0083] In that case, the step of calculating the pressure P applied to the braking system involves dividing the output value PV by the angular velocity ωr of the wheels according to the following formula:

[0084] P=PV / ωr

[0085] According to an embodiment, the aforementioned steps of detecting or calculating the temperature T of the brake discs of the brake system and the wheel speed include detecting or calculating such quantities based on real-time acquisition of such quantities during operating conditions of the brake system.

[0086] According to another embodiment, the aforementioned steps of detecting or calculating the temperature T of the brake discs of the brake system and the wheel speed comprise detecting or calculating such quantities on the basis of offline calculations based on data obtained by telemetry related to the operating conditions of the brake system.

[0087] According to an embodiment of the method, one or more inverse friction maps, or one or more corresponding inverse friction maps, are constructed based on experimental evaluation or based on direct friction map re-refinement and stored in a vehicle control unit or in the vehicle's brake system.

[0088] Each such inverse friction map or maps, or corresponding inverse friction map tables or tables, is associated with a particular unit of measurement of the brake disc temperature T and the target brake torque CT.

[0089] According to an embodiment, the method comprises a further step of preparing the quantity for reference to the inverse friction map, or the corresponding inverse friction map table, by adapting the measurement units of the detected quantity to the measurement units provided by the inverse friction map, or the corresponding inverse friction map table.

[0090] A further method encompassed by the present invention for estimating the application pressure P to be applied to the vehicle's brake system to obtain a target brake torque value CT is described below.

[0091] Such a method includes the following steps.

[0092] (a) detecting or calculating a first input quantity and a second input quantity, the first detected or calculated input quantity comprising a temperature T of a brake disc of the braking system and the second detected or calculated input quantity comprising a quantity dependent on a desired target brake torque CT;

[0093] (b) calculating an estimated application pressure value Ps based on the first input quantity and the second input quantity, based on the first brake friction coefficient test value μ1, and based on geometrical and / or structural and / or operational parameters of the brake system;

[0094] (c) determining a second brake friction coefficient value μ2 based on said temperature T of the brake disc of the brake system and said estimated operating pressure value Ps; this step is performed by electronic processing with reference to a digitally stored predefined friction map or a corresponding predefined friction map table.

[0095] (d) calculating an estimated brake torque value C based on the second brake friction coefficient value μ2 and geometrical and / or structural and / or operational parameters of the brake system;

[0096] (e) comparing the estimated brake torque value Cs with a target brake torque value CT;

[0097] (f) if the difference between the estimated brake torque value Cs and the target brake torque value CT is less than a predefined threshold, said estimated application pressure value Ps calculated in step (b) is taken as the application pressure P to be applied to the vehicle's brake system;

[0098] Alternatively, if the difference between the estimated brake torque value Cs and the target brake torque value CT is greater than said predetermined threshold, the aforementioned steps (b), (c) and (d) are repeated and the estimated application pressure value Ps calculated in the iterative step (b) is taken as the application pressure P to be applied to the vehicle's brake system until the difference between the estimated brake torque value Cs and the target brake torque value CT is less than said predetermined threshold.

[0099] According to an embodiment, the aforementioned second sensed or calculated input quantity comprises the desired target brake torque CT or the product of the target brake torque CT multiplied by the speed of the wheels on which the brake system acts.

[0100] According to an embodiment, all the steps of the above-mentioned embodiment of the method for estimating the pressure applied to a brake system of a vehicle are performed by electronic processing means.

[0101] In the following, a method is described for actuating a vehicle's brake-by-wire (BBW) brake system mounted on a vehicle having a first brake axle directly controlled by a driver by applying a first axle actuation pressure Pa1 and a second axle controlled by a brake-by-wire control system configured to apply a second axle control pressure Pa2 to the second axle.

[0102] Such a method includes the following steps.

[0103] Executing a method for estimating a brake torque (according to any one of the embodiments of such a method described above) to obtain an estimated brake torque value C1, where the aforementioned second input quantity is the first axle actuation pressure Pa1 controlled by the driver.

[0104] Executing a method (according to any one of the embodiments of such a method described above) for estimating a pressure P applied to a braking system of a vehicle, wherein a target braking torque value CT2 is related to said estimated braking torque value (C1) in a predefined known relationship and / or is calculated from said estimated braking torque value C1.

[0105] applying, to the second axle, a pressure equal to the pressure P obtained from the brake pressure estimation method, as a second axle control pressure Pa2, by the brake-by-wire control system;

[0106] According to an embodiment, all steps of the aforementioned method for operating a brake-by-wire braking system are performed by electronic processing means.

[0107] It should be noted that in possible implementations of the method described above, all calculations can be performed in real time or offline after the fact.

[0108] Further details of the method are provided below, for illustrative and non-limiting purposes only, in accordance with certain embodiments of the present invention, and with reference again to FIGS. 1-12.

[0109] 1 is a simplified flow diagram of steps involved in an embodiment of a method for estimating the brake torque of a brake system. Such a process flow includes the following steps:

[0110] 1: Detect or calculate two input quantities, a first quantity and a second quantity. The first quantity comprises the temperature of the disc brake (detected or calculated and representative of the current state), the second quantity comprises a quantity dependent on the pressure (detected or calculated and representative of the current state), and the second quantity can be one of the following: i. Brake system pressure. ii. Contact pressure between the moving surfaces (disc and pad). iii. Stem pressure multiplied by wheel speed. iv. The product of contact pressure and wheel speed.

[0111] If the initially detected amount does not match the subsequent steps, calculations or transformations must be included to make it match the friction map used in the next 2.

[0112] The magnitude can be obtained and used in real time or after the fact offline.

[0113] 2: From these input quantities, the method determines the brake's friction coefficient (or efficiency) by interpolation of a look-up table known as the "direct friction map." This value represents the best estimate of the friction coefficient under the "current" conditions measured in 1 above.

[0114] Examples of direct friction maps are shown in FIG. 6A (with the above-mentioned quantity i. or ii. as the second input quantity) and FIG. 6B (with the above-mentioned quantity iii. or iv. as the second input quantity).

[0115] An example of a look-up table corresponding to a direct friction map is shown in FIG.

[0116] The coefficient of friction can be calculated both at the axle level (a single value for both front or rear brakes) and at the corner level (right brake different from left brake on the same axle) based on available inputs.

[0117] 3: Once the friction coefficient is estimated, this value can be used together with system data (fixed values ​​related to the geometry of the brake system) to calculate the wheel braking torque. The braking torque can be estimated in real time or after the fact in an offline routine.

[0118] FIG. 2 is a simplified flow diagram of steps included in an embodiment of a method for estimating a quantity related to the operation of a vehicle braking system.

[0119] With respect to FIG. 1, such a diagram illustrates the following further steps.

[0120] 4: The brake torque estimated with the method shown in FIG. 1 can be used for further calculations or estimation of secondary quantities from the original estimate combined with other parameters or models.

[0121] Different embodiments include the following. · Multiplying the torque by the wheel speed to estimate the power dissipated during braking; Combining different torques (e.g. braking torque and traction torque) to estimate aerodynamic resistance and other quantities related to vehicle dynamics; Using the power dissipated by the brakes in a thermal model to estimate the temperature of the brakes or other components at the wheel corners; Using the braking torque generated at the axle directly controlled by the driver as a target for the brake-by-wire actuation system of the other axle.

[0122] All the above calculations can be performed in real time or offline after the fact.

[0123] 3 is a simplified flow diagram of steps involved in an embodiment of a method for estimating pressure to be applied to a vehicle's braking system to obtain a target brake torque value CT. Such a process flow includes the following steps:

[0124] 1: Detecting or calculating two input quantities, a first quantity and a second quantity, the first quantity consisting of the temperature of the disc brake (detected or calculated and representative of its current state) and the second quantity consisting of a quantity dependent on the target torque (i.e. the braking torque to be applied by the brake).

[0125] The second amount is one of the following: i. Target brake torque ii. The product of the target torque and the current wheel speed

[0126] If the initially detected quantities do not match the subsequent steps, calculations or transformations must be included to match the friction map used in 2 below.

[0127] Such quantities can be obtained and used in real time or after the fact offline.

[0128] 2: From these input quantities, the method determines the target pressure by interpolation of a look-up table known as the "inverse friction map". This value represents the best estimate of the pressure to be applied under the "current" conditions measured in point 1 above to ensure the target torque at the wheel.

[0129] An example of an inverse friction map is shown in Figure 8.

[0130] An example of the calculation of the inverse friction map from the direct friction map is shown in FIG.

[0131] An example of a look-up table corresponding to the inverse friction map is shown in FIG.

[0132] The aforementioned target pressures can be calculated at both an axle level (a single value for both front or rear brakes) and a corner level (right brake different from left brake on the same axle) based on available inputs.

[0133] The output of the inverse friction map can be either the target pressure directly or the product of the target pressure multiplied by the current wheel speed, in which case an additional calculation step is required to extrapolate the target pressure alone.

[0134] All calculations can be done in real time or offline after the fact.

[0135] FIG. 4 is a simplified flow diagram of the steps involved in another embodiment of a method for estimating the pressure to be applied to a vehicle's braking system to obtain a target brake torque value CT.

[0136] In this case, the actuation pressure is estimated directly from the friction map rather than from the inverse friction map through the following process flow which involves iterations.

[0137] 1: Detecting or calculating two input quantities, a first quantity and a second quantity, where the first quantity consists of the temperature of the disc brake (detected or calculated and representative of its current state) and the second quantity consists of a quantity dependent on the target torque (i.e. the braking torque applied by the brake).

[0138] The second amount can be one of the following: i. Target brake torque ii. The product of the target torque and the current wheel speed.

[0139] If the initially detected quantity is not consistent with the subsequent steps, calculations or transformations must be included to make it consistent with the friction map used in point 3 below.

[0140] The quantities can be obtained and used in real time or after the fact offline.

[0141] 2: Starting from such input quantities and a first (brake) friction coefficient value, the method determines a first target pressure estimate by direct calculation (dividing the target torque by the friction value and other geometric parameters of the brake system).

[0142] 3: Using the target pressure estimate, calculate a new "current" friction coefficient by interpolating a lookup table corresponding to the "direct friction map".

[0143] 4: Calculate the estimated torque from the target pressure estimate, the new friction coefficient and the geometric parameters of the brake system. If such estimated torque is close enough to the target torque (input in point 1 above), the estimate can be considered correct and the target pressure can therefore be used as output. If not, we need to go back to 2 and calculate a new target pressure estimate, this time using the friction coefficient calculated in 3 instead of the originally assumed value.

[0144] 5 is a simplified flow diagram of steps involved in another embodiment of a method for operating a vehicle brake-by-wire braking system using the methods described above, in which a vehicle equipped with a brake-by-wire braking system uses a combination of direct and inverse friction maps.

[0145] In particular, brake torque estimation via (direct) friction maps and target pressure calculation can be used in combination on vehicles with two braked axles, where the first braked axle is under direct control of the driver (the driver applies brake pressure directly to the brakes) and the second braked axle is under control of the BBW system, which must apply brake pressure based on the driver's actions on the first axle and other logic in the vehicle control unit (VCU).

[0146] FIG. 5 shows an example of the process flow when the working axle is the front axle and the axle under BBW is the rear axle, but those skilled in the art can easily understand the teachings provided by applying them to the reverse case.

[0147] The brake system referred to is that shown in Figures 11A-11C.

[0148] Figure 11A: The driver operates the brakes using the brake master cylinder, but only the front axle pressure is applied to the brake calipers.

[0149] FIG. 11B: The Vehicle Control Unit (VCU) processes the demands of the front and rear axles and targets for the KERS and BBW actuators.

[0150] FIG. 11C: The BBW actuator sets the pressure in the rear axle brake calipers.

[0151] The use of the friction map in this context is illustrated in FIG. A direct friction map converts front actuation pressure into estimated brake torque, which is useful for estimating actual braking effort at the front axle, rather than just the associated command effort. The inverse friction map converts the rear torque demand (calculated from the estimated front torque) into an equivalent brake pressure applied to the BBW axle.

[0152] As can be seen, the object of the invention as set out above is fully achieved by the method described above, thanks to the features disclosed in detail above. The advantages and technical problems solved by the method according to the invention have already been described above with reference to various features and aspects of the method.

[0153] In particular, the method disclosed above allows for an automatic and reliable estimation of important operating quantities of the braking system, such as the braking torque and the pressure that must be applied to the brake discs to obtain a certain braking torque, applicable to each operating condition of the braking system associated with a braking event and usable even in real time.

[0154] To meet foreseeable needs, those skilled in the art can make modifications and adaptations to the above-described method embodiments or substitute other functionally equivalent elements without departing from the scope of the following claims. Each feature described above as belonging to a possible embodiment can be implemented independently of the other embodiments described above.

Claims

1. 1. A method for estimating brake torque in a vehicle brake system under operating conditions, comprising: (a) detecting or calculating a first input quantity and a second input quantity representative of operating conditions of the brake system, the first input quantity comprises a temperature (T) of a brake disc of the brake system; a step (a) of detecting or calculating the second input quantity, the second input quantity comprising a quantity dependent on the pressure (P) of the brake system or the contact pressure (PC) between friction surfaces of the brake system; (b) determining a brake friction coefficient (μ) based on the first input quantity and the second input quantity, which is representative of expected brake friction or efficiency under conditions defined by the detected or calculated values ​​of the first input quantity and the second input quantity; a determining step (b), wherein said determining step (b) is performed by electronic processing by referencing a digitally stored predefined friction map or a corresponding predefined friction map table; (c) estimating the braking torque (C) based on the determined brake friction coefficient (μ) and geometrical and / or structural and / or operational parameters of the braking system.

2. The second input amount is the pressure (P) of the braking system, or the contact pressure (PC) between the friction surfaces of the brake system; or the pressure (P) of the braking system multiplied by the rotational speed (vr) of the wheel on which the braking system acts, or the product of the contact pressure (PC) between the friction surfaces of the brake system multiplied by the rotational speed (vr) of the wheel on which the brake system acts.

3. the braking system comprises at least one brake caliper and at least one brake disc; the friction surfaces of the brake system being a surface of the at least one brake disc and a surface of the at least one brake caliper; a surface of the at least one brake disc and a surface of the at least one brake caliper are configured to contact each other during a braking event; 3. The method of claim 2, wherein the rotational speed (vr) is the rotational speed of a wheel acted upon by the at least one brake disc and the at least one brake caliper of the braking system.

4. 2. The method of claim 1, wherein the detecting or calculating step (a) comprises detecting the first input quantity and the second input quantity based on real-time acquisition of the first input quantity and the second input quantity during an operating condition of the brake system.

5. 2. The method of claim 1, wherein the detecting or calculating step (a) comprises calculating the first input quantity and the second input quantity offline based on telemetry-obtained data related to an operating state of the brake system.

6. the friction map table comprises a predefined look-up table that provides the brake coefficient of friction (μ) as a function of the first input quantity and the second input quantity.

2. The method of claim 1, wherein the determining step (b) includes determining the brake coefficient of friction (μ) based on reading and / or interpolation performed on the lookup table by electronic processing.

7. 4. The method of claim 3, wherein the geometric and / or structural and / or operational parameters of the brake system used in estimating step (c) comprise geometric parameters associated with a piston of the at least one brake caliper and operational parameters of the at least one brake caliper.

8. The brake torque (C) is the brake friction coefficient (μ) multiplied by the area (A) of the piston of the at least one brake caliper. ＰｉｓＴ ) and the effective radius (R ｅｆｆ ) and the system pressure (P ｉｍＰ 8. The method of claim 7, wherein the value is calculated as a product of multiplication by

9. one or more friction maps constructed based on experimental evaluation, or one or more corresponding friction map tables, are stored in a control unit of the vehicle or in the brake system of the vehicle; 2. The method of claim 1, wherein each of the one or more friction maps, or each of the one or more corresponding friction map tables, is characterized by a particular first input quantity and a second input quantity expressed in respective units of measurement.

10. preparing the first input quantity and the second input quantity based on detected and / or measured quantities provided to the control unit; 10. The method of claim 9, wherein the first and second input quantities correspond to the specific first and second input quantities and the units of measure defined by a specific friction map or corresponding friction map table from among those stored and used in step (b).

11. 11. The method of claim 10, wherein the step of preparing the first input quantity and the second input quantity comprises adapting measurement units of the detected quantities to measurement units provided in the friction map or corresponding friction map table used.

12. 12. The method of claim 11, wherein the step of preparing the first input quantity and the second input quantity further comprises calculating the first input quantity and / or the second input quantity based on the obtained quantities in a manner consistent with a definition of the friction map or a corresponding friction map table used.

13. 10. The method of claim 9, further comprising the step of preparing, by the control unit, a modified friction map or a corresponding modified friction map table based on the actually obtained quantities and the quantities in the respective units of measurement.

14. the brake system, wherein the at least one brake caliper comprises a plurality of brake calipers and the at least one brake disc comprises a plurality of brake discs; 2. The method of claim 1, wherein steps (a), (b), and (c) are performed for each of the plurality of brake calipers and the plurality of brake discs.

15. The brake coefficient of friction (μ) is determined for each axle of the braking system, with a single brake coefficient of friction value (μ) being determined for both the brake calipers and the brake discs of an axle; or 15. The method of claim 14, wherein the brake coefficient of friction (μ) is determined for each of the plurality of brake calipers and the plurality of brake discs of an axle.

16. 1. A method for estimating a quantity related to operation of a braking system of a vehicle, comprising: Implementing a method for estimating a braking torque of a braking system according to any one of claims 1 to 15, and estimating at least one further quantity related to operation of the brake system based on the estimated brake torque and further detected or measured operating parameters; The at least one further quantity related to operation of the brake system is the power or energy consumed during braking, and / or other parameters related to aerodynamics or vehicle dynamics, and / or Brake temperature, and / or A method comprising: adjusting parameters in a brake-by-wire type actuation system.

17. the estimated braking torque is multiplied by the wheel speed to estimate the power dissipated during the braking operation; and / or and / or - estimating air resistance or other parameters related to vehicle dynamics based on the estimated braking torque and the detected or calculated traction torque of the vehicle; 17. The method of claim 16, wherein at least one brake torque target is estimated for at least one other respective axle of a brake-by-wire (BBW) actuation system based on the estimated brake torque of an axle directly controlled by a driver in the BBW actuation system.

18. 18. The method of claim 17, wherein the estimated power dissipated during braking is used in conjunction with a thermal model to estimate the temperature of a wheel brake disc or other component of the braking system.

19. 1. A method for estimating pressure (P) to be applied to a braking system of a vehicle to obtain a target brake torque value (Ct), comprising: i) detecting or calculating the temperature (T) of the brake discs of said braking system; ii) determining a pressure (P) to be applied to the brake system based on the temperature (T) of the brake disc of the brake system and the target brake torque value (Ct); A method wherein said determining step ii) is performed by electronic processing by referencing a digitally stored predefined inverse friction map or a corresponding predefined inverse friction map table.

20. the inverse friction map table comprises a predefined look-up inverse table indicating the pressure (P) to be applied to the brake system as a function of the temperature (T) of the brake disc and the brake torque value (Ct); 20. The method of claim 19, wherein the determining step ii) comprises determining the pressure (P) applied to the brake system based on reading and / or interpolation performed on the look-up inverse table by electronic processing.

21. the inverse friction map table comprises a predefined look-up inverse table that provides an output value (PV) equal to the product of the pressure (P) to be applied to the brake system multiplied by the speed of the wheel acting on the brake system as a function of the temperature (T) of the brake disc and the brake torque value (Ct); The determining step ii) comprises: reading and / or interpolating said look-up inverse table by electronic processing to obtain said output value equal to the pressure (P) applied to said brake system multiplied by the wheel speed; detecting or calculating the speed of said wheels under current driving conditions; 20. The method of claim 19, further comprising the step of calculating a pressure (P) to be applied to the brake system based on the output value (PV) obtained from the inverse friction map table and the detected or calculated wheel speed.

22. the detected or calculated velocity of the wheel is the angular velocity of the wheel (ωr); 22. The method of claim 21, wherein the step of calculating the pressure (P) to be applied to the brake system comprises dividing the output value (PV) by the angular velocity (ωr) of the wheel according to the formula [P=PV / ωr].

23. 20. The method of claim 19, wherein the step of detecting or calculating the temperature (T) of the brake disc and the wheel speed of the brake system comprises detecting or calculating the first input quantity and the second input quantity based on real-time acquisition of the first input quantity and the second input quantity during an operating state of the brake system or based on offline calculation based on data acquired by telemetry related to an operating state of the brake system.

24. one or more inverse friction maps, or one or more corresponding inverse friction map tables, are constructed based on experimental evaluation or based on direct friction map reprocessing and stored in a control unit of the vehicle or a control unit of a braking system of the vehicle; 20. The method of claim 19, wherein each of the one or more inverse friction maps or the one or more corresponding inverse friction map tables is associated with a particular unit of measure of brake disc temperature (T) and target brake torque (CT).

25. 25. The method of claim 24, further comprising preparing the quantity for reference to the inverse friction map or the corresponding inverse friction map table by adapting the unit of measure of the detected quantity to a unit of measure provided by the inverse friction map or the corresponding inverse friction map table.

26. 1. A method for estimating an application pressure (P) to be applied to a brake system of a vehicle to obtain a target brake torque value (CT), comprising: (A) detecting or calculating a first input quantity and a second input quantity, the first detected or calculated input quantity comprising a temperature (T) of a brake disc of the brake system, and the second detected or calculated input quantity comprising a quantity corresponding to a desired target brake torque (CT); (B) calculating an estimated actuation pressure value (Ps) based on the first input quantity and the second input quantity, based on a first brake friction coefficient test value (μ1), and based on geometric and / or structural and / or operational parameters of the brake system; (C) determining a second brake friction coefficient value (μ) based on the temperature (T) and the estimated actuation pressure value (Ps) of a brake disc of the brake system, wherein the determining step is performed by electronic processing with reference to a digitally stored predefined friction map or a corresponding predefined friction map table; (D) calculating an estimated brake torque value (Cs) based on the second brake friction coefficient value (μ2) and geometric and / or structural and / or operational parameters of the brake system; (E) comparing the estimated brake torque value (Cs) with the target brake torque value (CT); (F) if the difference between the estimated brake torque value (Cs) and the target brake torque value (CT) is less than a predetermined threshold, consider the estimated actuation pressure value (Ps) calculated in the calculating step (B) as the actuation pressure (P) applied to the brake system; If the difference between the estimated brake torque value (Cs) and the target brake torque value (CT) is greater than the predetermined threshold, steps (B), (C), and (D) are repeated until the difference between the estimated brake torque value (Cs) and the target brake torque value (CT) becomes smaller than the predetermined threshold, and the estimated operating pressure value (Ps) calculated in the final calculating step (B) is regarded as the operating pressure (P) to be applied to the brake system.

27. 27. The method of claim 26, wherein the second sensed or calculated input quantity comprises the target brake torque (CT) or the product of the target brake torque (CT) multiplied by the speed of the wheel being acted upon by the braking system.

28. 1. A method for actuating a brake-by-wire (BBW) braking system for a vehicle comprising a first brake axle directly controlled by a driver by applying a first axle actuation pressure (Pa1) and a second axle controlled by a brake-by-wire control system configured to apply a second axle control pressure (Pa2), comprising:

16. A step of performing a brake torque estimation method according to any one of claims 1 to 15 to obtain an estimated brake torque value (C1), wherein the second input quantity is a first axle operating pressure (Pa1) controlled by a driver; - executing an estimation method for obtaining a pressure (P) to be applied to the brake system according to any one of claims 19 to 27, wherein the target brake torque value (CT2) is related to the estimated brake torque value (C1) in a predefined known relationship and / or is calculated from the estimated brake torque value (C1); applying, to the second axle, as the second axle control pressure (Pa2), a pressure equal to the pressure (P) obtained by the brake pressure estimation method, by the brake-by-wire control system.

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