Method for detecting fluid leakages of a vehicle braking system

Abstract

The invention relates to a method (700) for detecting fluid leakages of a vehicle braking system (100; 200; 300; 400). The braking system includes: - at least one hydraulic or electro-hydraulic actuator (1) of a disc brake (2), at least one electronic processing unit (10, 10', 20, 20' ) connected to the at least one hydraulic or electro-hydraulic actuator for receiving data, representative of a hydraulic pressure measurement (P) of the actuator and a stroke measurement (x) of an actuator piston, associated with one or more braking events during a braking detection time interval. The method includes the following steps: - enabling (701), by at least one electronic processing unit, a fluid leakage monitoring block (3) following the detection of at least one braking event in the braking detection time interval; the fluid leakage monitoring block includes a supervisory block (31), an average stiffness monitoring block (32) of the braking system and a monitoring block of a working area (33) of the braking system; - receiving (702), by the fluid leakage monitoring block, at least a first hydraulic pressure measurement of the actuator (Ps) and at least a first measurement of the stroke (xs) of the actuator piston relating to one of these one or more braking events and a required pressure value (Pv) from the at least one electronic processing unit; - enabling (703), by the supervisory block, the average stiffness monitoring and working area monitoring blocks when the required pressure value is greater than or equal to a first predetermined enabling pressure value (Pl); - validating (704), by the supervisory block, this braking event of the one or more braking events if the required pressure value is greater than a second predetermined enabling pressure value (P2) during at least one predetermined enabling time interval (T2); - identifying (705), by the average stiffness monitoring block, a linear function (f (x) ) suitable for defining a relationship between the at least one first hydraulic pressure measurement of the actuator as a function of the at least one first measurement of the stroke of the actuator piston; an angular coefficient of the identified linear function (f (x) ) represents the average stiffness of the braking system; - generating (706), by the average stiffness monitoring block, a first parameter (STIFFNESS) based on a comparison between the angular coefficient of tthhee identified linear function with a predetermined threshold stiffness value (Kth); - generating ( 707 ), by the working area monitoring block, a second parameter (AREA_FLAG) representative of actuator pressure and actuator piston stroke values not allowed when the at least a first hydraulic pressure measurement of the actuator is less than or equal to a predetermined threshold pressure value ( Pth) and the at least a first piston stroke measurement is greater than or equal to a predetermined threshold position value (xth); - processing ( 708 ), by a counter block ( 34 ) of the leakage monitoring block, the first and second parameters to generate a numerical counter value ( Ilk) suitable to be compared with a numerical threshold value (Nth) to generate information (LI ) representative of a presence or absence of fluid leakage from the vehicle braking system.

Description

DESCRIPTION"METHOD FOR DETECTING FLUID LEAKAGES OF A VEHICLE BRAKING SYSTEM"

[0001] . FIELD OF THE INVENTION

[0002] . The present invention relates to the field of vehicle braking systems. In particular, the invention relates to a method for detecting fluid leakages of a braking system of a vehicle, of the type employing, for example, electro-hydraulic actuators of a disc brake, in accordance with brake-by-wire (BBW) technology.

[0003] . STATE OF THE ART

[0004] . Today, there are several known systems and methods that allow for the detection of fluid leakages of a vehicle braking system.

[0005] . For example, document US9522668B2 describes a braking apparatus configured to identify a fluid leakage point while generating a braking force. The braking apparatus is configured to operate a pump to supply a brake fluid to a first fluid passage and a second fluid passage, to switch valves communicating alternately between the open and closed positions more than once, and to detect a brake fluid leakage in the first or second fluid passage based on the magnitude of the detected values by hydraulic pressure sensors during the open-close switching.

[0006] . In addition, document US10315639B2 describes a method of inspecting the leakages of an electric braking system, which includes a brake pump connected to a tank, a simulation device having one side connected to the brake pump to provide a reactionforce based on the ef fort of the brake pedal , a simulation valve provided in a flow path connected to the brake pump or in a flow path connected to the tank, a hydraulic pressure supply device actuated by an electrical signal from a pedal displacement sensor that detects a displacement of the brake pedal and configured to generate hydraulic pressure , and a hydraulic pressure control unit .

[0007] . Document US 11279337B2 describes a diagnostic method, in particular for determining the seal of at least one gasket and / or valve , for at least one component of a vehicle , in which a cylinder-piston unit , whose piston is driven by an electromotor drive , forms a pressure supply unit , in which a control unit identi fies the position of the piston and / or the movement of the piston by means of at least one sensor and the pressure generated by the pressure supply unit or the motor current flowing through the drive by means of at least one sensor .

[0008] . The methods and systems for detecting fluid leakages of a vehicle braking system of a known type are not without defects and have some drawbacks .

[0009] . In fact , these known methods only work for commercial vehicles (with ABS and ESP ) , so the related detection system involves the use of numerous hydraulic valves to open and close and, in general , the use of additional hydraulic components . Furthermore , the known leakage detection methods can only be activated when the vehicle is stationary and in the absence of abraking action by the driver.

[0010] . In addition, during the detection of leakages in the hydraulic system, the known solutions described above may return one or more erroneous or false positive detections, each representative of a potential fluid leakage information in the braking system. It should be noted that, in general, following the detection of one of these false positives, the vehicle control system can generate an alarm for the user to induce him to stop the vehicle and verify the actual functionality of the braking system.

[0011] . As far as the Applicant is aware, there are currently no methods that allow for the detection, with high accuracy and reliability, in order to reduce false positives, fluid leakages of a braking system of a vehicle using, for example, electro-hydraulic actuators, i.e. of the BBW type in which the brake pump is electronically actuated.

[0012] . SUMMARY

[0013] . One purpose of the present invention is to devise and make available a method for detecting fluid leakages of a braking system of a vehicle which involves, for example, electro-hydraulic actuators of a disc brake, in accordance with brake-by-wire (BBW) technology, which allows to overcome, at least partially, the limits and drawbacks of known solutions.

[0014] . This purpose is achieved by a method for detecting fluid leakages of a vehicle braking system in accordance with claim 1.

[0015] . The proposed methodology involves the acquisition of a first quantity, representative of the stroke of an actuator piston, and a second quantity, representative of the hydraulic pressure of the actuator, during the normal operation of the braking system, i . e . when the vehicle is in motion .

[0016] . The detection method of the invention is suitable to combine the aforementioned two quantities to calculate and control two parameters representative of the operating state of the braking system . Speci fically, by relating the hydraulic pressure of the actuator to the stroke of the actuator piston, the proposed method is suitable to calculate and control the average sti f fness of the system and the working area of the system .

[0017] . It should be noted that in a Cartesian plane having, as the axis of the abscissa, the set of stroke values of the actuator piston and, as the axis of the ordinate , the set of actuator pressure values , the points of the plane represented by a pair of stroke-pressure values acquired during the normal operation of the braking system, are substantially attributable to a linear function of a real variable defined by a polynomial of degree one , that is , which is in the form : f (x ) = ax+b ( 1 ) where a, b are real numbers and a is di f ferent from zero .

[0018] . The angular coef ficient a, or slope with respect to the axis of the abscissa, of this linear function f (x ) , or straight line , obtained by interpolating the aforementioned points of theplane, constitutes a first parameter representative of the state of the system, also called the average stiffness of the braking system.

[0019] . A region of the aforementioned Cartesian plane comprising all the points having respective stroke and pressure values included within a first and a second range of predetermined values constitutes a second parameter representative of the state of the system, also called the working area of braking system.

[0020] . In particular, contrary to the known solutions described above, the method of the invention provides for an initial phase of evaluation of each braking event, i.e. the execution of a selection of braking data.In this initial phase, a pressure value required by an electronic vehicle control unit (Vehicle Control Unit or VCU) is evaluated in order to discriminate conditions that lead one to assume that the two parameters mentioned above can undertake significant values. This initial evaluation phase is performed to minimize the detection of false positives, which would lead to a vehicle stop not justified by real safety requirements.

[0021] . In greater detail, to evaluate the reliability of each braking event, the method of the invention provides for verifying that the pressure value required by said electronic vehicle control unit (VCU) is greater than a predetermined reference value (target) , for example equal to 30 bar, for a time interval greater than a predetermined reference time interval, for example equal to100 ms. If these conditions are met, the braking event is considered reliable and the first quantity, representative of the stroke of an actuator piston, and the second quantity, representative of the hydraulic pressure of the actuator, are processed in order to calculate and control the above-mentioned parameters, average stiffness and working area of the system, to provide an indication of the operating status of the braking system.

[0022] . In addition, the method of the invention provides, for each reliable braking event, to calculate the aforementioned parameters to determine whether there is a real probability of fluid leakage from the vehicle braking system or not.

[0023] . More specifically, the acquired hydraulic pressure data of the actuator are reported as a function of the stroke of the actuator piston for the evaluation of the average stiffness of the system, represented by the angular coefficient of the above- mentioned linear function (straight line) of the Cartesian plane that best approximates the data trend, and the working area of the system.

[0024] . Specifically, the evaluation of the working area involves the step of verifying that the pressure and stroke values of the piston measured for each braking event fall or not within the range of pressure values (on the ordinate) and piston stroke (on the abscissa) not allowed.

[0025] . For example, such not allowed ranges of pressure andpiston stroke values are characteri zed by high values of piston stroke of the actuator, for example piston stroke values greater than 10 mm, and low hydraulic pres sure values of the actuator, for example , pressure values of less than 40 bar, which can be quanti fied from time to time according to the specific characteristics of the braking system .

[0026] . Generally, the fact that the aforementioned points of the Cartesian plane , each representing a pair of stroke-pressure values acquired during the normal operation of the braking system, fall within these ranges of pressure and stroke values not allowed, alone is not necessarily indicative of the presence of a fluid leakage from the braking system .

[0027] . In order to be able to discriminate whether the fact that the above-mentioned points of the Cartesian plane fall within these ranges of not allowed pressure and stroke values is indicative of the presence of a fluid leakage in the braking system, it is also necessary to evaluate the average sti f fness of the system, i . e . the angular coef ficient of the above-mentioned linear function ( straight line ) of the Cartesian plane that best approximates the trend of the acquired hydraulic pressure data of the actuator .

[0028] . Some advantageous embodiments are the subj ect o f the dependent claims .

[0029] . DESCRIPTION OF THE FIGURES

[0030] . Further features and advantages of the method fordetecting fluid leakages in a vehicle braking system will appear from the following description of its preferred embodiments , given by way of non-limiting example , with reference to the accompanying figures in which :

[0031] . - figure 1 schematically illustrates a first embodiment of a vehicle braking system, which employs , for example , an electro-hydraulic actuator, configured to implement the method for detecting fluid leakages according to the present invention;

[0032] . - figure 2 schematically illustrates a second embodiment of a vehicle braking system, which employs , for example , an electro-hydraulic actuator, configured to implement the method for detecting fluid leakages according to the present invention;

[0033] . - figure 3 schematically illustrates a third embodiment of a vehicle braking system, which employs , for example , an electro-hydraulic actuator, configured to implement the method for detecting fluid leakages according to the present invention;

[0034] . - figure 4 schematically illustrates a fourth embodiment of a vehicle braking system, which employs , for example , an electro-hydraulic actuator, configured to implement the method for detecting fluid leakages according to the present invention;

[0035] . - figure 5 illustrates , with a block diagram, the functions implemented by an electronic control unit of the braking system or by a vehicle control unit of figures 1-4 for the detection of fluid leakages ;

[0036] . - figure 6 illustrates , with a functional block diagram,an embodiment of a fluid leakage monitoring algorithm of figure 5;

[0037] . - figure 7 illustrates, with a flow chart, the operating steps of the general method for detecting fluid leakages of a braking system of a vehicle of the invention;

[0038] . - figures 8A-8B illustrate in a Cartesian plane having, as the axis of the abscissa, values of piston stroke of the actuator and, as the axis of the ordinate, the set of actuator pressure values, diagrams relating to two braking events comprising a plurality of points of the plane each represented by a pair of acquired stroke-pressure values, and a linear function adapted to define a relationship between each pair of strokepressure values and a region of the plane comprising the points having stroke-pressure values included within a first and a second range of not allowed values or prohibited area.

[0039] . In the above figures, the same or similar elements are indicated with the same numerical references.

[0040] . DETAILED DESCRIPTION

[0041] . With reference to figures 1-4, the numerical references 100, 200, 300, 400 indicate, in total, four examples of a vehicle braking system that implements the method 700 for detecting fluid leakages of the braking system according to the present invention.

[0042] . Fo r the purposes of this description, "vehicle" means any motor vehicle or motorcycle, including commercial vehicles, having two, three, four or more wheels. For example, a vehicle is a car, a motorcycle, a light commercial vehicle, a heavy industrialvehicle, or any other vehicle that requires a braking system to reduce the speed of moving parts.

[0043] . In addition, "braking system" means a set of all components (from mechanical and / or electrical or electronic to braking fluid) that contribute to the generation of a service braking of a vehicle.

[0044] . In more detail, the braking system 100, 200, 300, 400 of figures 1-4 employs an electro-hydraulic actuator 1 of the disc brake 2. In this case, a brake pump is driven by the electro- hydraulic actuator 1 in accordance with the brake-by-wire (BBW) technology .

[0045] . Although in the figures and examples described below, explicit reference is made to braking systems employing electro- hydraulic actuators 1, the present invention is also advantageously applicable to a braking system employing a simple hydraulic actuator, i.e. the brake pump driven by the brake pedal.

[0046] . Referring to the example of figure 1, the braking system 100 comprises a vehicle control unit 10 (VCU) , connected to the electro-hydraulic actuator 1 of the disc brake 2, and an electronic control unit 20 (ECU) of the braking system. In particular, this electronic control unit 20, of BBW-type, is configured to perform the processing that implements the method of the invention, in particular through a leakage monitoring algorithm 3 (LEAKAGE MONITORING or LM) , and is provided with both a communication interface and a sensor interface.

[0047] . As is known, the electronic control unit 20 (ECU) is a dedicated controller (microcomputer ) for automobiles comprising a microprocessor ( CPU) , memory (ROM, RAM) , input / output interface ( I / O) , and an analog-to-digital converter (A / D) . In addition, the vehicle control unit 10 VCU is the main electronic control unit of the vehicle responsible for the management and coordination of various subsystems within the vehicle . For this coordination, the VCU interacts with one or more electronic control units (ECUs ) present in the vehicle .

[0048] . In particular, the electro-hydraulic actuator 1 is configured to send to this electronic control unit 20 , through the aforementioned sensor interface , data representative of a stroke measurement x of the actuator piston and a hydraulic pressure measurement P of the actuator . These data are provided directly by the sensors associated with the electro-hydraulic actuator 1 of the disc brake 2 .

[0049] . The vehicle control unit 10 is configured to send to both the electronic control unit 20 and the electro-hydraulic actuator 1 , for example through a CAN-type communication interface , a pressure value Pv required by the electronic vehicle control unit to be compared with a reference pressure value ( target ) .

[0050] . Following the processing performed by the leakage monitoring algorithm 3 , the electronic control unit 20 is configured to send to the vehicle control unit 10 , again via theCAN-type communication interface, information LI representative of a possible fluid leakage of the vehicle's braking system 100.

[0051] . Referring to the example of figure 2, the braking system 200 comprises a first vehicle control unit 10' and a first electronic control unit 20' of the braking system different from the electronic control unit 20 of the system 100 of figure 1. In particular, this first electronic control unit 20' is devoid of a direct connection with the electro-hydraulic actuator 1 of the disc brake 2 and is provided only with communication interfaces. This first electronic control unit 20' is configured to perform the processing that implements the method of the invention, through the aforementioned leakage monitoring algorithm 3 (LM) .

[0052] . In this second example, the first vehicle control unit 10' includes both a communication interface and a sensor interface. In particular, this first vehicle control unit 10' is configured to receive data representative of a stroke measurement x of the actuator piston and a hydraulic pressure measurement P of the actuator. These data are provided directly by the sensors associated with the electro-hydraulic actuator 1 of the disc brake 2.

[0053] . In addition, the first vehicle control unit 10' is configured to send to the electro-hydraulic actuator 1, for example through a CAN-type communication interface, a pressure value Pv required by the vehicle's electronic control unit to be compared with a reference pressure value (target) .

[0054] . In addition, the first vehicle control unit 10' is configured to send, for example through a CAN-type communication interface, the aforementioned pressure value Pv required by the vehicle's electronic control unit.

[0055] . In addition, still the first vehicle control unit 10' is configured to send to the first electronic control unit 20', for example through a CAN-type communication interface, both the data representative of the stroke measurement x of the actuator piston and the hydraulic pressure measurement P of the actuator, and the aforementioned pressure value Pv required by the vehicle's electronic control unit.

[0056] . Following the processing performed through the leakage monitoring algorithm 3, the first electronic control unit 20' is configured to send to the first vehicle control unit 10', again through the CAN-type communication interface, a LI information representative of a possible fluid leakage of the vehicle braking system 200.

[0057] . With reference to the example of figure 3, the braking system 300 comprises only a first vehicle control unit 10', analogous to the unit 10' of the system 200, connected to the electro-hydraulic actuator 1 of the disc brake 2 and provided with communication and sensor interfaces.

[0058] . This first vehicle control unit 10' is configured to perform the processing that implements the method of the invention.In other words, the functions that in the braking systems 100, 200are delegated to the dedicated electronic control unit 20, 20', in the braking system 300 are carried out, autonomously, by the first vehicle control unit 10' .

[0059] . This first vehicle control unit 10' is configured to send, for example, through a CAN-type communication interface, a pressure value Pv required by the vehicle's electronic control unit to the electro-hydraulic actuator 1.

[0060] . In this third example, this first vehicle control unit 10' is configured to receive the data representative of a stroke measurement x of the actuator piston and a pressure measurement P of the actuator directly from the sensors associated with the electro-hydraulic actuator 1 of the brake to generate information LI representative of a possible fluid leakage of the vehicle braking system 300. This information LI is generated internally to the VCU 10 ' .

[0061] . Referring to the example of figure 4, the system 400 comprises only one electronic control unit 20 of the BBW braking system, similar to that described with reference to the system 100, connected to the electro-hydraulic actuator 1 of the disc brake 2. In particular, this electronic control unit 20 BBW is configured to perform the processing that implements the method of the invention, through the aforementioned leakage monitoring algorithm 3 (LM) , and is provided with both communication interfaces and sensor interfaces.

[0062] . In this fourth example, this electronic control unit 20BBW is configured to receive the data representative of a stroke measurement x of the actuator piston and a pressure measurement P of the actuator directly from the sensors associated with the electro-hydraulic actuator 1 of the brake to generate information LI representative of a possible fluid leakage of the vehicle braking system 400 .

[0063] . In addition, the electronic control unit 20 BBW is configured to receive from the outside , for example from a pedal , the aforementioned required pressure value Pv to be compared with a reference pressure value ( target ) , always through the CAN-type communication interface . This required pressure value Pv is also made available to the electro-hydraulic actuator 1 of the disc brake 2 .

[0064] . A particular embodiment of the functionalities of the invention implemented by the electronic control unit 20 , for example , of the braking system 100 of a vehicle in figure 1 , which employs electro-hydraulic actuators (BBW) , is described with reference to the block diagram of figure 5 .

[0065] . In particular, this electronic control unit 20 comprises a block 3 representative of the leakage monitoring algorithm ( LEAKAGE MONITORING or LM) configured to receive as input : data, representative of one or more stroke measurements xs of the actuator piston and one or more pressure measurements Ps of the actuator, relating to a current braking maneuver and, in addition, the aforementioned pressure value Pv required by thevehicle's electronic control unit to be compared with a reference pressure value (target) .

[0066] . In a non-limiting embodiment, the leakage monitoring block 3 is also configured to receive as input an enable signal (enable) En that starts processing.

[0067] . Following the aforementioned processing, the leakage monitoring block 3 is configured to return a counter Ilk representative of the number of events that may indicate the occurrence of a fluid leakage in the braking system 100. Note that the electronic control unit 20 also includes a comparison block 4.

[0068] . The proposed algorithm provides for comparing this counter Ilk with a numerical threshold value Nth through the comparison block 4 to generate the above-mentioned information LI representative of a possible fluid leakage of the vehicle's braking system 100. Note that this information is binary, that is, it can only have two values: value 1 (1 logical) or 0 (0 logical) .

[0069] . In a preferred embodiment, the aforementioned numerical threshold value Nth is equal to two.

[0070] . The refore, following the comparison performed by block 4, the algorithm implemented by the electronic control unit 20 returns an alarm signal if the counter Ilk is greater than or equal to two. This alarm signal corresponds to the information LI generated by the comparison block 4 equal to 1 logical. Instead, in the case where the counter Ilk is less than two, the comparison block 4 generates an LI information equal to 0 logical, that is,no alarm.

[0071] . A particular embodiment of the aforementioned fluid leakage monitoring functional block 3 is described with reference to the functional block diagram of figure 6.

[0072] . In particular, the fluid leakage monitoring block 3 comprises a plurality of functional blocks, specifically a supervisory block 31 (SUPERVISOR) , a average stiffness monitoring block 32 of the braking system (STIFFNESS MONITORING) , a monitoring block of a working area of braking system 33 (X VS P MONITORING) .

[0073] . In addition, the fluid leakage monitoring block 3 includes a counter computation block 34 (COUNTER COMPUTATION) .

[0074] . In greater detail, the supervisory block 31 is configured to receive the enable signal (enable) En that starts the processing and the aforementioned pressure value Pv required by the vehicle's electronic control unit.

[0075] . The supervisory block 31 is configured to enable, through a respective first enable signal Enl, the monitoring blocks 32 and 33 mentioned above when the required pressure value Pv is greater than or equal to a first predetermined enable pressure value Pl. For example, this first enable pressure value Pl is equal to 10 bar. If this condition occurs, the supervisory block 31 is configured to make this first enable signal (enable) Enl available.

[0076] . In addition, the supervisory block 31 considers a braking event to be valid if the pressure value Pv required by the vehicle's electronic control unit is maintained greater than asecond predetermined enable pressure value P2, consecutively during at least one predetermined enable time interval T2. For example, this second enable pressure value P2 is equal to 30 bar and the enable time interval T2 is equal to 100msec.

[0077] . The refore, the method of the invention provides two different thresholds: a first threshold to start saving data relating to a braking event that will be used for processing (Pv> = lObar) ; a second threshold to start processing the aforementioned data (Pv> = 30bar for t> 100ms) . If the first condition occurs, the data is saved; if also the second condition occurs, the saved data is used by algorithm 3 for processing, otherwise it is discarded .

[0078] . The supervision block 31 is configured to generate a binary command brake_acc: if the supervision block 31 considers a braking event to be valid, that is, the required pressure value Pv is greater than or equal to the second enable pressure value P2 (e.g. 30 bar) during at least the enabling time interval T2 (e.g. 100 msec) , i.e. for a time greater than this enabling time T2, this command brake_acc assumes a logical value of 1, i.e. the braking event meets the validity requirements. Otherwise, the command brake_acc assumes a logical 0 value.

[0079] . It should be noted that this command brake_acc is made available both to the average stiffness monitoring block 32 of the braking system and to the working area monitoring block 33 of the braking system. These monitoring blocks 32 and 33 are configuredto output respective parameters , STI FFNESS and AREA_FLAG, associated with the braking system, only after the receipt of the command brake_acc equal to a logic 1 .

[0080] . In addition, both the average sti f fness monitoring block 32 of the system and the working area monitoring block 33 are configured to receive as input :- the first enable signal Enl generated by the supervisory block 31 ;- the command brake_acc generated by the supervision block 31 ;- one or more measurements of the current pressure Ps of the actuator and one or more measurements of the current position xs of the actuator piston .

[0081] . With reference to the diagrams of figures 8A and 8B, it should be noted that the average sti f fness monitoring block 32 , when enabled, is configured to execute a respective algorithm, in particular a recursive least squares (RLS ) algorithm to identi fy the linear function f (x ) expressible with the above-mentioned equation : f (x ) =ax+b able to interpolate the points of the Cartesian plane each having, as abscissa, one of the measured piston position values xs and, as ordinate , the corresponding measured value of the actuator pressure Ps . The aforementioned recursive least squares (RLS ) algorithm is of a type known to an expert in the field and will not be discussed in detail below .

[0082] . If the braking event is validated, the average stiffness monitoring block 32 is configured to output the STIFFNESS parameter, or first parameter, representative of the slope a of the straight line identified by the equation (1) , or the average stiffness of the braking system, otherwise a default value.

[0083] . In particular, the evaluation of the average stiffness parameter of the system provides for the verification that the angular coefficient a of the linear function of the equation (1) that best approximates the trend of the points of the Cartesian plane associated with the measured data xs, Ps is either above or below a predetermined threshold value. Therefore, the STIFFNESS parameter generated by the stiffness monitoring block 32 assumes a logical value of 0 if the angular coefficient of the straight line of the equation (1) is greater than a predetermined threshold stiffness value Kth and a logical value of 1 if this angular coefficient is less than this predetermined threshold stiffness value Kth.

[0084] . For example, this threshold stiffness value Kth is equal to 2 bar / mm.

[0085] . With reference to block 33, which monitors the working area of the braking system, when this block 33 is enabled by the supervisory block 31, it is checked whether the measurement of the current pressure Ps of the actuator is lower than a threshold pressure value Pth and if the measurement of the current position xs of the piston is greater than or equal to a threshold positionvalue xth . This threshold pressure value Pth delimits a range of pressure values not allowed below this threshold . This piston stroke threshold value xth delimits a range of stroke values not allowed greater than this threshold . These prohibited pressure and stroke intervals define a prohibited working area FA.

[0086] . For example , these pressure and stroke threshold values are equal to : Pth = 40 bar and xth = 10 mm .

[0087] . In particular, in case that the braking event is valid and the control performed by the monitoring block 33 detects pressure and stroke values that are not allowed, this block 33 that monitors the relationship piston stroke - actuator pressure is configured to generate a respective AREA_FLAG parameter or second parameter, adapted to assume a logic value 1 to indicate that the pressure and stroke values that are not allowed have been exceeded, otherwise a logic value 0 .

[0088] . Generally, the fact that the measured Cartesian plane points fall within the prohibited pressure and stroke value ranges or prohibited working area FA of system is not necessarily indicative of a possible fluid leakage from the braking system . It could also be due to the fact that the pistons have been moved back from their standard resting position during a previous mechanical intervention, so a longer stroke is detected that is not associated with a corresponding increase in pressure . To be sure that it is a leak, the average sti f fness of the system has to be also checked .

[0089] . With reference to figure 8B, for a braking event, some points of the diagram representing the acquired measurements fall within the prohibited area FA.

[0090] . In this case, the evaluation is performed as follows:

[0091] . - the AREA_FLAG parameter is assigned a logical 0 value if all the points measured and reported on the Cartesian plane are outside the prohibited working area FA;

[0092] . - the AREA_FLAG parameter is assigned a logical value of1 if at least one of the points falls within the prohibited working area FA.

[0093] . The counter calculation block 34 included in the leakage monitoring block 3 is configured to receive both the first parameter, STIFFNESS, and the second parameter AREA_FLAG mentioned above to generate the aforementioned counter Ilk.

[0094] . In particular, this counter calculation block 34 is configured to increase the value of the counter Ilk by one unit if the average stiffness of the braking system calculated by block 32 is less than the aforementioned predetermined threshold stiffness value Kth. This is, for example, the situation relating to the diagram of figure 8A.

[0095] . In addition or alternatively, this counter calculation block 34 is configured to increase the value of the counter Ilk by two units if the average stiffness of the braking system calculated by block 32 is less than the aforementioned predetermined threshold stiffness value Kth and, at the same time, the not allowed pressureand stroke values have been exceeded. This is, for example, the situation related to the diagram in figure 8B.

[0096] . In other words, by recursively adding and combining the values 0 and 1 of the first and second parameters of the braking system 100 in the calculation block of the counter 34, between one braking and the next, it is possible to obtain a numerical value that is indicative of a probable fluid leakage from the braking system.For example, by combining the data obtained from the evaluation of two successive braking actions, one can find the situations represented in Tables 1 and 2 below:Table 1Table 2

[0097] . In particular, in the event that the average stiffness of the system is assessed as not worrying (0 logic) , but the points of the Cartesian plane representative of the measured values of stroke-pressure fall within the prohibited working area (second row of Tables 1 and 2) is not necessarily indicative of an alarming case. In fact, it is likely that high values of the piston stroke of actuator corresponding to low hydraulic pressure values of the actuator acquired in parallel with acceptable values of average system stiffness are caused by an event external to the braking system, for example a previous maintenance intervention by mechanical technicians on the braking system, or an impact suffered by the vehicle, for example at a curb. In this case, the algorithm does not indicate any action to be taken.

[0098] . In general, when the overall evaluation of the two parameters of a single braking event, or when the overallevaluation of the two parameters of several successive braking events, is greater than or equal to 2 (third and fourth lines of Tables 1 and 2) , then the algorithm of the invention is led to believe that there is a high probability of fluid leakage in the braking system. Therefore, an alarm signal is sent to the user and an immediate stop of the vehicle is recommended.

[0099] . With reference to figure 7, the numerical reference 700 indicates, overall, a general example of the method for detecting fluid leakages of a braking system 100, 200, 300, 400 of a vehicle according to the invention.

[0100] . The method of Figure 7 begins with a symbolic start phase "STR" and ends with a symbolic end phase "ED".

[0101] . The aforementioned braking system 100, 200, 300, 400 of the vehicle includes: at least one hydraulic or electro-hydraulic actuator 1 of a disc brake 2, at least one electronic processing unit 10, 10', 20, 20' connected to said at least one hydraulic or electro-hydraulic actuator 1 for receiving data, representative of a hydraulic pressure P measurement of the actuator and a stroke measurement x of an actuator piston, associated with one or more braking events during a braking detection time interval.

[0102] . Method 700 comprises a step of enabling 701, by at least one electronic processing unit 10, 10', 20, 20', a fluid leakage monitoring block 3 following the detection of at least one brakingevent in the braking detection time interval. This fluid leakage monitoring block 3 includes a supervisory block 31, an average stiffness monitoring block 32 of the braking system, and a monitoring block of a working area 33 of the braking system.

[0103] . In addition, the method 700 comprises the step of receiving 702, by the fluid leakage monitoring block 3, at least a first hydraulic pressure measurement of the actuator Ps and at least a first measurement of the stroke xs of the actuator piston relative to one of the aforementioned one or more braking events and a required pressure value Pv from at least one electronic processing unit 10, 10', 20, 20' .

[0104] . Method 700 also provides for enabling 703, by the supervisory block 31, the aforementioned average stiffness monitoring 32 and working area monitoring 33 blocks when the required pressure value Pv from said at least one electronic processing unit 10, 10', 20, 20' is greater than or equal to a first predetermined enable pressure value Pl or target pressure value .

[0105] . The method of the invention, advantageously, provides for a validation phase 704, by the supervision block 31, of the braking event of said one or more braking events if the required pressure value Pv from the at least one electronic processing unit 10, 10', 20, 20' is greater than a second predetermined enabling pressure value P2 during at least a predetermined enabling time interval T2, i.e. for a time greater than the aforementionedenabling time T2.

[0106] . Furthermore, the method 700 comprises a step of identifying 705, by the average stiffness monitoring block 32, a linear function f (x) suitable for defining a relationship between the at least one first hydraulic pressure measurement of the actuator Ps as a function of said at least one first measurement of the stroke xs of the actuator piston. It should be noted that an angular coefficient of this identified linear function f (x) represents the average stiffness of the braking system.

[0107] . Furthermore, the method 700 provides for a phase of generating 706, by the average stiffness monitoring block 32, a first parameter, that is, the STIFFNESS parameter mentioned above, based on a comparison between the angular coefficient of the linear function f (x) identified with a predetermined threshold stiffness value Kth.

[0108] . In addition, it is expected to generate 707, by the working area monitoring block 32, a second parameter, that is, the AREA_FLAG parameter mentioned above, representative of not allowed values of actuator pressure and piston stroke of the actuator when the first hydraulic pressure measurement of the actuator Ps is less than or equal to a predetermined threshold pressure value Pth and the at least a first measurement of the stroke xs of the actuator piston is greater than or equal to a predetermined threshold position value xth.

[0109] . The method 700 of the invention provides for theprocessing 708, by a counter block 34 of the leakage monitoring block 3, the first STIFFNESS and the second AREA_FLAG parameters to generate a numerical value of the counter Ilk suitable to be compared with a numerical value of threshold Nth to generate an information LI representative of a presence or absence of fluid leakage from the braking system of the vehicle.

[0110] . According to an embodiment, the aforementioned processing step 708 of the method includes the steps of:

[0111] . - increasing, by the counter calculation block 34, the value of said counter Ilk of a unit if the angular coefficient of the identified linear function f (x) is less than the aforementioned predetermined threshold stiffness value Kth, and / or

[0112] . - increase, by the calculation block of the counter 34, the value of this counter Ilk by two units if the angular coefficient of the linear function f (x) identified is less than the aforementioned predetermined threshold stiffness value Kth and at the same time the at least a first hydraulic pressure measurement of the actuator Ps is less than or equal to a predetermined threshold pressure value Pth and the at least a first measurement of the stroke xs of the actuator piston is greater than or equal to a predetermined threshold position value xth.

[0113] . According to a further embodiment, this numerical threshold value Nth is equal to two and the method further comprises a step of generating an alarm signal if the value of this counter Ilk is greater than or equal to two.

[0114] . According to a further embodiment, this step of enabling 701 the fluid leakage monitoring block 3 comprises a step of making an enable signal En available to the fluid leakage monitoring block 3 which starts the processing.

[0115] . According to a further embodiment, this step of enabling 703 the average stiffness monitoring blocks 32 and monitoring said working area 33 further comprises the step of making available, by the supervisory block 31, a first enabling signal (Enl) to these monitoring blocks.

[0116] . According to a further embodiment, this linear function f (x) is identified by a recursive least squares (RLS) algorithm; the linear function f (x) can be expressed by the equation:

[0117] . f (x)=ax+b

[0118] . whe re a, b are real numbers and a is not zero.

[0119] . According to a further embodiment, the first enabling pressure value Pl is equal to 10 bar.

[0120] . According to a further embodiment, this second enablement pressure value P2 is equal to 30 bar and the enablement time interval T2 is equal to 100msec.

[0121] . According to a further embodiment, this threshold stiffness value Kth is equal to 2 bar / mm.

[0122] . According to a further embodiment, this threshold pressure value Pth is equal to 40 bar and this threshold position value xth is equal to 10 mm.

[0123] . The present invention also relates to a braking system100, 200, 300, 400 of a vehicle comprising:

[0124] . - at 1 east one hydraulic or electro-hydraulic actuator 1 of a disc brake 2,

[0125] . - at least one electronic processing unit 10, 10', 20, 20' connected to at least one hydraulic or electro-hydraulic actuator 1 for receiving data representative of a hydraulic pressure measurement P of the actuator and a stroke measurement x of an actuator piston, associated with one or more braking events during a braking detection time interval, wherein at least one electronic processing unit 10, 10', 20, 20' is configured to perform the method in accordance with the present invention.

[0126] . The present invention also relates to a computer program comprising an application code loaded on a memory and executable by at least one electronic processing unit 10, 10', 20, 20' of a braking system 100, 200, 300, 400 of a vehicle, to implement the method of the present invention.

[0127] . Compared to known solutions, the method 700 of the invention has the advantage of allowing to detect any leakages in the hydraulic line of a vehicle braking system more efficiently, monitoring and measuring the stroke of the actuator piston and the hydraulic pressure of the actuator, reducing the number of false positives .

[0128] . In fact, the aforementioned validation step of the braking event allows for the preliminary evaluation of the two measured quantities mentioned above, so as to select only theconditions that make it possible to assume that these quantities can assume values indicative of a fluid leakage in the system, discarding the others. This initial evaluation step allows, in this way, to minimize the detection of false positives that lead to a vehicle stop not justified by real safety needs.

[0129] . Moreover, unlike the solutions known today, the monitoring strategy proposed with the invention works in parallel with the normal operation of the system, i.e. with the vehicle in motion while the driver is braking, and does not require any additional hydraulic components.

[0130] . In the embodiments of the method described above, a technician in the field, in order to meet contingent needs, may make modifications, adaptations and substitutions of elements with other functionally equivalent ones, without departing from the scope of the following claims. Each of the features described as belonging to a possible embodiment can be realized independently of the other embodiments described.

Claims

CLAIMS1. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) of a vehicle, said braking system comprising : at least one hydraulic or electro-hydraulic actuator (1) of a disc brake ( 2 ) , at least one electronic processing unit (10, 10', 20, 20' ) connected to said at least one hydraulic or electro-hydraulic actuator (1) for receiving data, representative of a hydraulic pressure measurement (P) of the actuator and a stroke measurement (x) of an actuator piston, associated with one or more braking events during a braking detection time interval; the method (700) comprising the steps of: enabling (701) , by said at least one electronic processing unit (10, 10', 20, 20' ) , a fluid leakage monitoring block (3) following the detection of said at least one braking event in said braking detection time interval, said fluid leakage monitoring block (3) comprising a supervisory block (31) , an average stiffness monitoring block (32) of the braking system and a working area monitoring block (33) of the braking system; - receiving (702) , by said fluid leakage monitoring block (3) , at least a first hydraulic pressure measurement (Ps) of the actuator and at least a first stroke measurement (xs) of the actuator piston related to one of said one or more braking events and a required pressure value (Pv) from said at least oneelectronic processing unit (10, 10', 20, 20' ) ;- enabling (703) , by said supervisory block (31) , said average stiffness monitoring (32) and working area monitoring (33) blocks when the required pressure value (Pv) from said at least one electronic processing unit (10, 10', 20, 20') is greater than or equal to a first predetermined enabling pressure value (Pl) ;- validating (704) , by the supervisory block (31) , said braking event of said one or more braking events if said required pressure value (Pv) from said at least one electronic processing unit (10, 10', 20, 20' ) is greater than a second predetermined enabling pressure value (P2) during at least one predetermined enabling time interval (T2) ;- identifying (705) , by said average stiffness monitoring block (32) , a linear function (f (x) ) suitable for defining a relationship between the at least a first hydraulic pressure measurement of the actuator (Ps) as a function of said at least a first stroke measurement (xs) of the actuator piston, an angular coefficient of said identified linear function (f (x) ) representing the average stiffness of the braking system;- generating (706) , by said average stiffness monitoring block (32) , a first parameter (STIFFNESS) based on a comparison between the angular coefficient of said identified linear function (f (x) ) with a predetermined threshold stiffness value (Kth) ;- generating (707) , by said working area monitoring block (32) ,a second parameter (AREA_FLAG) representative of actuator pressure and actuator piston stroke values not allowed when the at least a first hydraulic pressure measurement of the actuator (Ps) is less than or equal to a predetermined threshold pressure value (Pth) and said at least a first stroke measurement (xs) of the actuator piston is greater than or equal to a predetermined threshold position value (xth) ;- processing (708) , by a counter block (34) of said leakage monitoring block (3) , the first (STIFFNESS) and the second (AREA_FLAG) parameter to generate a numerical counter value (Ilk) suitable to be compared with a numerical threshold value (Nth) to generate information (LI) representative of a presence or absence of fluid leakage from the vehicle braking system.

2. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) according to claim 1, wherein said processing step (708) comprises the steps of:- increasing, by the counter calculation block (34) , the value of said counter (Ilk) by one unit if the angular coefficient of said identified linear function (f (x) ) is less than the said predetermined threshold stiffness value (Kth) ; and / or- increasing, by the counter calculation block (34) , the value of said counter (Ilk) by two units if the angular coefficient of said identified linear function (f (x) ) is less than the said predetermined threshold stiffness value (Kth) and at the same time the at least a first hydraulic pressure measurement of the actuator(Ps) is less than or equal to a predetermined threshold pressure value (Pth) and said at least a first measurement of the stroke (xs) of the actuator piston is greater than or equal to a predetermined threshold position value (xth) .

3. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) according to claim 1 or 2, wherein said numerical threshold value (Nth) is equal to two, the method further comprising a step of generating an alarm signal if the value of said counter (Ilk) is greater than or equal to two.

4. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) according to any one of the preceding claims, wherein said step of enabling (701) the fluid leakage monitoring block (3) comprises a step of making available to the fluid leakage monitoring block (3) an enabling signal (En) that starts the processing .

5. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) according to any one of the preceding claims, wherein said step of enabling (703) the average stiffness monitoring (32) and said working area monitoring (33) blocks further comprises the step of making available, by the supervisory block (31) , a first enabling signal (Enl) .

6. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) according to any one of the preceding claims, wherein said linear function (f (x) ) is identified by a Recursive Least Squares (RLS) algorithm, said linear function (f (x) ) being expressible by the equation:f (x) =ax+b where a, b are real numbers and a is different from zero.

7. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) according to any one of the preceding claims, wherein said first enabling pressure value (Pl) is equal to 10 bar.

8. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) according to any one of the preceding claims, wherein said second enabling pressure value (P2) is equal to 30 bar and the enabling time interval (T2) is equal to 100msec .

9. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) according to any one of the preceding claims, wherein said threshold stiffness value (Kth) is equal to 2 bar / mm.

10. Method (700) for detecting fluid leakages of a braking system (100; 200; 300; 400) according to any one of the preceding claims, wherein said threshold pressure value (Pth) is equal to 40 bar and said threshold position value (xth) is equal to 10 mm.

11. Braking system (100; 200; 300; 400) of a vehicle comprising: at least one hydraulic or electro-hydraulic actuator (1) of a disc brake ( 2 ) , at least one electronic processing unit (10, 10', 20, 20' ) connected to said at least one hydraulic or electro-hydraulic actuator (1) for receiving data representative of a hydraulicpressure measurement (P) of the actuator and a stroke measurement(x) of an actuator piston, associated with one or more braking events during a braking detection time interval, said at least one electronic processing unit (10, 10', 20, 20' ) being configured to perform the method according to one or more of claims 1-10.

12. Computer program comprising an application code loaded into a memory and executable by at least one electronic processing unit (10, 10', 20, 20' ) of a braking system (100; 200; 300; 400) of a vehicle, for implementing the method according to claims 1-10.

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