How to obtain information about the wear condition of a vehicle's brake system.
The method estimates brake system wear using brake master cylinder measurements to provide a wear index and control adaptation, addressing the need for reliable and cost-effective wear assessment in brake systems, ensuring consistent performance.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- FRENI BREMBO S P A O PIU BREVEMENTE BREMBO
- Filing Date
- 2024-05-13
- Publication Date
- 2026-05-27
AI Technical Summary
Existing methods for obtaining wear information on vehicle brake systems, particularly those using brake-by-wire technology, are expensive and require dedicated sensors, lacking a reliable and cost-effective indirect method for assessing wear on friction materials.
A method that estimates fluctuations in the brake system's plant model using measurements of brake master cylinder pressure, stroke, and temperature to update the model without special braking operations, providing a wear index and control adaptation, suitable for both hydraulic and electro-hydraulic actuators.
Enables accurate wear state estimation without dedicated sensors, maintaining consistent brake performance by adapting control parameters, suitable for endurance races.
Smart Images
Figure 2026517013000001_ABST
Abstract
Description
Technical Field
[0001] Field of the Invention
[0002] The present invention belongs to the field related to vehicle braking systems. In particular, the present invention relates to a method for obtaining information on the wear state of a vehicle braking system based on brake-by-wire (BBW) technology of disc brakes, which employs, for example, a hydraulic actuator or an electro-hydraulic actuator, and is based on the estimation of changes received by a mathematical plant model representing the braking system.
Background Art
[0003] Background Art
[0004] As is well known, the mathematical model or plant model of a braking system can be defined by a parametric function f that describes the relationship between the stroke x of the brake master cylinder and the brake pressure p applied by the master cylinder itself as a function of a group of coefficients. In some cases, the brake fluid temperature T may also be used as an input variable to the brake plant model. Therefore, the aforementioned parametric function f satisfies the following relationship.
Equation
[0005] One possible embodiment of the parametric function of the plant model is parabolic, for example, as follows.
Equation
Equation
[0006] The plant model of a brake system can change significantly during endurance races due to wear on friction materials, i.e., wear on disc brake pads and discs. The main effects of this wear are as follows:
[0007] Increased idle stroke of the brake master cylinder,
[0008] This is a change in stiffness due to an increase in the amount of fluid inside the caliper.
[0009] Such degradation reduces the performance of the braking system, especially in systems employing brake-by-wire (BBW) technology, particularly when using electronically actuated brake master cylinders that primarily rely on this information.
[0010] However, the aforementioned changes in the characteristics of the plant model can be used as a means to provide indirect information about the wear condition of the brake system itself.
[0011] Known solutions for obtaining wear information on the friction material of a vehicle's brake system include the use of specific sensors, such as linear variable displacement transducer (LVDT) sensors. These are typically mounted on the caliper.
[0012] These sensors have the disadvantage of being particularly expensive and require a dedicated interface on the caliper to be operational.
[0013] To the best of the applicant's knowledge, there is currently no method to obtain information indicating the wear state of friction materials indirectly, with high accuracy and reliability. This is true for both brake systems employing hydraulic actuators, where the brake master cylinder is operated by the brake pedal, and brake systems employing electronically operated hydraulic actuators. In other words, the same applies to BBW type systems (where the brake master cylinder is electronically operated). [Overview of the Initiative]
[0014] solution
[0015] The object of the present invention is to devise and provide a method for obtaining information on the wear state of a vehicle brake system by estimating fluctuations in the plant model of the brake system that may occur, particularly during endurance races. This can at least partially overcome the limitations and shortcomings of known solutions.
[0016] This objective is achieved by a method for obtaining information regarding the wear condition of the vehicle brake system as described in claim 1.
[0017] The proposed method allows for the estimation of a plant model of a vehicle's brake system based on available measurements within the system, such as the pressure p of the brake master cylinder, the stroke x of the brake master cylinder, and, in some cases, the temperature T of the brake fluid.
[0018] In particular, the proposed method is configured to update the plant model of the brake system during normal braking without requiring any special braking operation. Therefore, it is suitable for long-distance endurance races.
[0019] In other words, the proposed method allows updating the plant model representing the brake system based on measurements of pressure, brake master cylinder stroke, and, in some cases, temperature. Referring to an exemplary illustration of a parabolic plant model, this means that, starting from an initial parabola characterized by given coefficients geometrically corresponding to a parabola with a given opening, it is possible to associate a new parabola with the brake system having new coefficients geometrically corresponding to parabolas with different openings.
[0020] Depending on the type of brake system, two different pieces of information can be obtained using the method of the present invention: namely, the wear index of the system and the control adaptation.
[0021] The first information, i.e., the wear index, represents percentage information regarding the wear state of the friction material based on the change in the estimated plant model during a race. This wear index is composed of a map that associates the change in the rigidity of the plant (as a function of the parabola coefficient) with the wear level. Specifically, when there is no wear, the rigidity of the plant is at its maximum, and when the wear is at its maximum, the rigidity is at its minimum.
[0022] This first information is suitable for both a braking system employing a hydraulic actuator and a braking system employing an electro-hydraulic actuator (i.e., one based on BBW technology).
[0023] The second information or control adaptation of the estimated plant model is used to adapt the parameters or structure of a closed-loop pressure / torque controller.
[0024] In particular, the control adaptation consists of changing some parameters of the electronic control unit (ECU) of an electronic control actuator based on these updated coefficients of the plant model.
[0025] Such second information is suitable only for a CAN-type braking system and is closely related to the specific control architecture implemented.
[0026] The advantage of obtaining the wear index is that the braking system does not require an expensive dedicated sensor (such as an LVDT sensor, etc.) attached to the caliper. Furthermore, there is no need to set up an interface between such a sensor and the caliper.
[0027] Furthermore, in the case of a braking system that already employs a caliper-mounted sensor, the proposed method enables the use of an additional wear estimation mode, i.e., a redundant mode, that operates in parallel with the sensor itself. This can improve the quality of the information provided by the aforementioned sensor.
[0028] The advantage of acquiring control adaptive information is that wear can significantly affect the performance of the controlled actuator, so it helps to maintain that performance consistently throughout the entire endurance race.
[0029] Some of the advantageous embodiments are subject to dependent claims. [Brief explanation of the drawing]
[0030] drawing
[0031] Further features and advantages of a system for acquiring information on the wear condition of a vehicle brake system will become apparent from the description of preferred embodiments shown below, with reference to the attached drawings and as non-limiting examples.
[0032] [Figure 1] Figure 1 illustrates a first embodiment of a vehicle brake system employing a hydraulic actuator configured to carry out the method of the present invention.
[0033] [Figure 2] Figure 2 illustrates a second embodiment of a vehicle brake system employing a hydraulic actuator configured to carry out the method of the present invention.
[0034] [Figure 3] Figure 3 schematically shows a third embodiment of a vehicle brake system employing a hydraulic actuator configured to carry out the method of the present invention.
[0035] [Figure 4] Figure 4 schematically shows a fourth embodiment of a vehicle brake system employing an electrohydraulic actuator configured to carry out the method of the present invention.
[0036] [Figure 5] Figure 5 shows, using a block diagram, the functions implemented by the electronic control unit of the brake system shown in Figure 4.
[0037] [Figure 6] Figure 6 shows the operational steps of a general method for obtaining information regarding the wear state of the vehicle brake system of the present invention, using a flowchart.
[0038] [Figure 6A] Figure 6A shows an example of an adaptable control structure based on the output of the control adaptation block in Figure 5, using a block diagram.
[0039] [Figure 7] Figure 7 shows a detailed example of the method in Figure 6 when the coefficient estimation is recursive during vehicle operation, using the first flowchart.
[0040] [Figure 8] Figure 8 shows a detailed embodiment of the method in Figure 6 when the coefficient estimation performed during vehicle operation is non-recursive, using a second flowchart. [Modes for carrying out the invention]
[0041] Description of some preferred embodiments
[0042] Referring to Figures 1-4, reference numerals 100, 200, 300, and 400 together represent four examples of vehicle brake systems that implement a method 500 for obtaining information regarding the wear condition of a brake system according to the present invention.
[0043] In this specification, “vehicle” means any automobile or motorcycle having two, three, four or more wheels, including commercial vehicles. For example, “vehicle” means automobiles, motorcycles, light commercial vehicles, heavy industrial vehicles, or any other vehicle that requires a braking system to reduce the speed of moving parts.
[0044] Furthermore, the term "brake system" refers to the entire set of components (from mechanical and / or electrical / electronic components to brake fluid) that contribute to the generation of the vehicle's service brakes.
[0045] More specifically, the brake systems 100, 200, and 300 shown in Figures 1, 2, and 3 employ a hydraulic actuator 1 for the brake disc 2. This hydraulic actuator is a brake master cylinder 1 that is actuated by the brake pedal 3.
[0046] The brake system 400 in Figure 4 employs an electro-hydraulic actuator 4 for the disc brake 2. In this system 400, the brake master cylinder is actuated by the electro-hydraulic actuator 4 based on brake-by-wire (BBW) technology.
[0047] Referring to the example in Figure 1, the system 100 includes a vehicle control unit 10 (VCU) connected to the hydraulic actuator 1 of the disc brake 2, and an electronic control unit 20 (ECU) of the brake system. In particular, such an electronic control unit 20 is configured to perform processes that carry out the method of the present invention and is provided only with a communication interface.
[0048] The vehicle control unit 10 is configured to transmit data representing the measured pressure p of the brake master cylinder, the measured stroke x of the brake master cylinder, and optionally the measured brake fluid temperature T to the aforementioned electronic control unit 20, for example, via a CAN type communication interface.
[0049] Such data p, x, and T are provided to the vehicle control unit 10 from the associated sensors of the brake master cylinder 1, which is actuated by the brake pedal 3.
[0050] Furthermore, the vehicle control unit 10 is configured to transmit an activation signal E to the aforementioned electronic control unit 20 again via a communication interface such as a CAN type. This initiates the aforementioned processing by the control unit 20.
[0051] After the above processing, the vehicle control unit 10 is configured to receive, again via the CAN type communication interface, first information or wear index WI representing the wear state of the friction material 100 of the brake system from the electronic control unit 20.
[0052] Referring to the example in Figure 2, the system 200 includes a vehicle control unit 10 and a first electronic control unit 20' of the brake system, which is different from the electronic control unit 20 of the system 100. In particular, this first electronic control unit 20' is connected to the hydraulic actuator 1 of the disc brake 2 and includes both a communication interface and a sensor interface. The first electronic control unit 20' is configured to perform processes that carry out the method of the present invention.
[0053] In this second example, the vehicle control unit 10 is configured to transmit only a single activation signal E to the first electronic control unit 20', for example via a CAN-type communication interface, in order to initiate the processing by the first electronic control unit 20'.
[0054] The first electronic control unit 20' is configured to directly receive data from associated sensors of the brake master cylinder 1, which are actuated by the brake pedal 3, representing measured values of the brake master cylinder pressure p, the brake master cylinder stroke x, and optionally, the brake fluid temperature T.
[0055] After the above processing, the vehicle control unit 10 is configured to receive, again via the CAN type communication interface, first information WI or wear index representing the wear state of the friction material of the brake system 200 from the first electronic control unit 20.
[0056] Referring to the example in Figure 3, system 300 consists only of a first vehicle control unit 10' connected to the hydraulic actuator 1 of the disc brake 2 and equipped with a sensor interface. Such a first vehicle control unit 10' is configured to perform processes that implement the method of the present invention. In other words, functions that were delegated to dedicated electronic control units 20, 20' in systems 100, 200 are autonomously performed by the first vehicle control unit 10' in system 300.
[0057] In this third embodiment, such a first vehicle control unit 10' receives measurements of the brake master cylinder pressure p, the brake master cylinder stroke x, and optionally the brake fluid temperature T directly from the associated sensor of the brake master cylinder 1, which is actuated by the brake pedal 3, and generates first information WI representing the wear state of the friction material of the brake system 300, or first information WI representing a wear index representing the wear state of the friction material of the brake system 300.
[0058] Referring to the example in Figure 4, system 400 includes a vehicle control unit 10 similar to those described with respect to systems 100 and 200, and a corresponding electronic control unit 20a for a BBW-type brake system connected to an electrohydraulic actuator 4 of the disc brake 2. In particular, such a BBW electronic control unit 20a is configured to perform processes that carry out the method of the present invention and includes both a communication interface and a sensor interface.
[0059] In particular, the vehicle control unit 10 is configured to send only one activation signal E to the BBW type electronic control unit 20a via, for example, a CAN type communication interface, in order to initiate the aforementioned processing by the BBW type electronic control unit 20a.
[0060] In one embodiment, the activation signal E from unit 10 can be considered equivalent to the brake signal provided as an input to the electrohydraulic actuator 4. In other words, the processing steps by the BBW-type electronic control unit 20a can be initiated independently of the vehicle control unit 10.
[0061] Such a BBW-type electronic control unit 20a is configured to directly receive measurements of the brake master cylinder pressure p, the brake master cylinder stroke x, and optionally the brake fluid temperature T from sensors associated with the electrohydraulic actuator 4 of the disc brake 2.
[0062] After the aforementioned processing, the vehicle control unit 10 is configured to receive, again via the CAN type communication interface, first information indicating the wear state of the friction material of the brake system 400, i.e., the wear index WI, from the BBW type electronic control unit 20a.
[0063] It should be noted that in this embodiment, only the first information indicating the wear index WI is transmitted as output to the vehicle control unit 10. The second information related to control adaptation remains embedded within the BBW type electronic control unit 20a, which controls the actuator 4.
[0064] A specific embodiment of the function of the present invention, implemented by an electronic control unit 20a of a brake system 400 of a vehicle employing an electrohydraulic (BBW) actuator, will be described with reference to the block diagram in Figure 5.
[0065] In particular, such an electronic control unit 20a includes an estimation (online estimation) block 22. This estimation block receives as input, as representative data associated with the brake operation, measured values of the brake master cylinder pressure p, measured values of the brake master cylinder stroke x, and optionally measured values of the brake fluid temperature T related to the brake operation. This allows it to calculate the "optimal" coefficient of a specific function f (e.g., having a parabolic tendency) that characterizes the plant model of the brake system.
[0066] In particular, as will be described later, after the estimation block 22 receives the estimable signal E1 transmitted from the supervision block 21, it provides the estimated plant model coefficients θi0, ..., θin to the main block, i.e., the supervision block 21.
[0067] It should be noted that, based on a specific plant model and the minimized merit function for obtaining optimal coefficients, estimation using block 22 can be implemented in two ways: a recursive solution and a non-recursive solution.
[0068] In the recursive solution method, the coefficient values of the parabolic function f are updated at each sampling of pressure p, stroke x, and possibly temperature T within the brake detection time interval.
[0069] In the case of a non-recursive solution, the coefficient values of the parabolic function f are calculated at the end of the braking operation based on the recorded dataset.
[0070] The algorithms used in both the recursive and non-recursive solutions belong to prior art. Furthermore, in both cases, the observation window is the time range of the brake event, and in fact, in the recursive case, the coefficient value at the end of the brake operation is the same as the value obtained in the non-recursive case. The difference between the two solutions is that the recursive solution requires a predetermined size of memory resources from the processing unit 20a, while the non-recursive solution requires more memory because it requires saving and processing the entire brake event. This is because the duration of the brake event itself is not known in advance.
[0071] For example, by using the recursive least squares method, one possible embodiment of the plant model function f can be represented as a parabola:
number
[0072] Referring to Figure 5, the electronic control unit 20a further includes a filtering block 23. The filtering block 23 is configured to receive estimated coefficients θi0, ..., θin as input from the estimation block 22 and, after receiving the corresponding filtering enable signal FE, provide the filtering coefficients θ'0, ..., θ'n of the plant model to the supervision block 21.
[0073] The filtering block 23 is configured to allow the results of each brake operation to be averaged.
[0074] Furthermore, to obtain a smooth estimate of the plant model when wear is present, this block allows for the inclusion of temperature effects, which are not considered in the input data, and also the knock-off phenomenon.
[0075] As is well known, knock-off is a phenomenon in which the piston retracts from its "nominal" position due to vibrations, such as those caused by passing over a curb during a race. As a result, the actuator needs to use a greater stroke to bring the pads into contact with the disc during the next braking action, resulting in significantly different plant characteristics during that braking event.
[0076] In one embodiment, such a filtering block 23 is a low-pass filter in the brake operation region, for example, a first-order linear filter, which can be expressed by the following equation.
number
[0077] The supervisor block 21 is configured to manage the entire function. This supervisor block 21 is configured to receive the aforementioned activation signal E as input to initiate processing. Furthermore, specifically for the brake system 400, the supervisor block 21 is configured to receive an input signal AS representing the operating state of the actuator 4.
[0078] Furthermore, the supervisor block 21 receives representative data of the measured brake master cylinder pressure p as input and is configured to activate the estimation block 22 and the filtering block 23 with the estimation enable signal E1 and the filtering enable signal FE, respectively.
[0079] Furthermore, based on the processes performed, the supervisory block 21 is configured to generate verified coefficients VC0, ..., VCn and provide them as outputs to the wear estimation block 24 and the control adaptation block 25.
[0080] More specifically, the wear estimation block 24 is configured to receive verified coefficients VC0, ..., VCn from the supervision block 21 as input to calculate first information, namely the wear index WI, which takes into account the wear of the friction material.
[0081] The control adaptive block 25 takes verified coefficients VC0, ..., VCn as input and is configured to update the parameters / structure of the BBW electronic control unit 20a using second information or control adaptive CA in order to maintain constant performance of the brake system 400 despite wear.
[0082] Referring to Figure 6, reference numeral 500, as a whole, represents a general example of a method for obtaining information regarding the wear condition of the vehicle brake systems 100, 200, 300, and 400 according to the present invention.
[0083] The method shown in Figure 6 begins with a symbolic start step "STR" and ends with a symbolic end step "ED".
[0084] The brake systems 100, 200, 300, and 400 of the aforementioned vehicles include the following:
[0085] At least one hydraulic actuator 1, 3, or electro-hydraulic actuator 4 for disc brakes 2, 3, and 4;
[0086] At least one electronic processing unit 10, 10', 20, 20', 20a. The electronic processing unit is connected to at least one hydraulic actuator 1, 3 or electro-hydraulic actuator 4 and receives data representing a measured pressure p of the brake master cylinder actuated by the actuator and a measured stroke x of the brake master cylinder during the brake detection time interval associated with each brake event.
[0087] Method 500 includes step 501 of providing a parametric function f representing the current state of the vehicle's brake systems 100, 200, 300, 400 to at least one electronic processing unit 10, 10', 20, 20', 20a. Such a parametric function f is adapted to describe the relationship between the stroke x of the brake master cylinder and the brake pressure p applied by the brake master cylinder as a function of one or more coefficients θ0, θ1, ..., θn, as shown, for example, in equation (4).
[0088] Method 500 further includes step 502 in which a functional monitoring block 21 of at least one electronic processing unit 10, 10', 20, 20', 20a detects one or more brake samples in a brake detection time interval. This allows an estimation block 22 of at least one electronic processing unit 10, 10', 20, 20', 20a to be activated after the detection of each brake sample.
[0089] Method 500 also includes step 503 in which, for each of the one or more brake samples (where i indicates the i-th brake sample), the estimation block 22 receives a first pressure measurement pi of the brake master cylinder and a first stroke measurement xi of the brake master.
[0090] The method includes step 504 in which the estimation block 22 estimates a plurality of first coefficients θi0, ..., θin of a parametric function f associated with each brake sample, based on the first pressure measurement pi of the brake master cylinder and the first stroke measurement xi of the brake master cylinder.
[0091] Method 500 then includes step 505 in which the supervisory block 21 activates the filtering block 23 of at least one electronic processing unit 10, 10', 20, 20', 20a at the end of the brake detection time interval.
[0092] Furthermore, method 500 includes a filtering step 506 by a filtering block 23. In this step, a plurality of first filtering coefficients θi0, θi1, ..., θin associated with each brake sample are filtered to generate a plurality of second filtering coefficients θ'0, θ'1, ..., θ'n. The second filtering coefficients are provided to the supervision block 21.
[0093] Method 500 of the present invention includes a step 507 of verifying the filtered coefficients θ'0, ..., θ'n. In this step, the supervisor block 21 verifies the filtered coefficients θ'0, ..., θ'n and generates verified coefficients VC0, ..., VCn that define a first parametric f' representing the state of the brake systems 100, 200, 300, 400 after the brake detection time interval.
[0094] Method 500 includes step 408 of transmitting the verified coefficients VC0, ..., VCn to a wear estimation block 24 of at least one electronic processing unit 10, 10', 20, 20', 20a to generate first information WI representing the wear condition of the friction material of the brake systems 100, 200, 300, 400.
[0095] In one embodiment, the first information WI representing the wear state of the friction material of brake systems 100, 200, 300, and 400 is a predefined function g calculated by the formula WI=g(VC0, ..., VCn) based on the verified coefficients VC0, ..., VCn.
[0096] In a particular embodiment of method 500, the receiving step 503 further includes the step of having the estimation block 22 receive a measurement of the brake fluid temperature T. In this case, the parametric function f is adapted to describe the relationship between the stroke x of the brake master cylinder and the brake fluid temperature T in relation to the braking pressure p applied by the master cylinder.
[0097] In yet another embodiment, method 500 further includes the step of transmitting verified coefficients VC0, ..., VCn to a control adaptive block 25 of at least one electronic processing unit 20a. This generates a second information CA that at least one electronic processing unit 20a uses to modify one or more control parameters.
[0098] In particular, one or more such control parameters are configured to adjust the current pressure p of the brake master cylinder. For example, based on the control scheme 50 shown in Figure 6A, this pressure is changed to be equal to the value of the reference pressure p*. This control scheme 50 has a feedforward (FF) block 51 on the first open-loop branch and a proportional-integral-derivative (PID) block 52 on the second feedback branch. The FF block 51 is updated based on second information CA generated based on verified coefficients VC0, ..., VCn. The gain of the PID block 52 is programmed based on second information CA generated based on the aforementioned verified coefficients VC0, ..., VCn. Note that this second information CA represents the mode in which the parameters of the curve affect a particular control block, as a function of the contents of the adaptive control block 25.
[0099] In another embodiment, the filtering step 506 is performed in the brake operation region using a low-pass filter, particularly a first-order linear filter.
[0100] In another embodiment, the detection step 502 includes detecting the start and end times of the brake detection time interval. Step 504, which estimates a plurality of first coefficients θi0, …, θin, includes running a recursive estimation algorithm between the start and end times of the brake detection time interval.
[0101] In another embodiment, relating to the non-recursive case, detection step 502 still includes steps of detecting the start and end times of such brake detection time intervals and saving each time point of such brake detection time intervals. However, unlike the recursive case described above, step 504 for estimating a plurality of first coefficients θi0, ..., θin includes a step of running a non-recursive estimation algorithm after the end time of the brake detection time interval.
[0102] More specifically, the step of detecting the start of the brake detection time interval includes detecting that the brake pressure p applied by the brake master cylinder is greater than a preset value of the threshold pressure pa. The step of detecting the end of the brake detection time interval includes detecting that the brake pressure p applied by the brake master cylinder is less than or equal to a preset value of the threshold pressure pa.
[0103] Referring to Figures 7 and 8, details of one embodiment of the method 500 of the present invention shown in Figure 6 are described below using the first flowchart 500a and the second flowchart 500b. These flowcharts correspond to the cases where the coefficient estimation is performed recursively and non-recursively by the electronic processing units 10', 20, 20', and 20a while the vehicle is in motion, respectively.
[0104] In both embodiments, the system starts from an idle state and appropriately performs brake operation detection steps 502a (brake operation start / end detection) and 502b (brake operation detection) to select a dataset appropriate for the estimation problem.
[0105] In the case of recursive estimation 504a (recursive online estimation enabled) performed while the vehicle is in operation, detection step 502a ensures that the estimation algorithm operates between the detection of the start of a brake operation and the detection of the end of a brake operation.
[0106] In the case of non-recursive estimation 504b (non-recursive online estimation enablement) performed while the vehicle is in operation, such detection step 502b (brake operation detection) allows the entire brake operation to be detected and saved, along with the associated check (brake operation check) 509b, before coefficient estimation 504b.
[0107] In either case, as described above, the detection of the start moment of the brake detection time interval includes the step of detecting that the brake pressure p applied by the brake master cylinder exceeds a preset value of the threshold pressure pa. The detection of the end moment of the brake detection interval includes the step of detecting that the brake pressure p applied from the brake master cylinder is less than or equal to a preset value of the threshold pressure pa.
[0108] At the end of each detected braking operation, the appropriate function verifies the consistency of the operation (509a, 509b).
[0109] In the case of estimating recurrent coefficients, such consistency checks 509a are post-hoc checks to accept the estimation results 504a.
[0110] In the case of non-recurrent coefficient estimation, such consistent estimation 509b makes it possible to eliminate unnecessary braking operations before calculating the "optimal" coefficient 504b, which refers to the braking action itself.
[0111] In particular, in the case of recurrent estimation, supervisor block 21 collects input data, receives the estimated f-function parameters from estimation block 22, evaluates its reliability by eliminating less important brake events in block 509a and physically unacceptable parameters (consistency check of raw coefficients) in block 511a. In the case of non-recurrent estimation, supervisor block 21 receives the input data and evaluates significant brake events in block 509b. Possible f-function parameter estimates are received from estimation block 22 and their reliability is evaluated by excluding physically unacceptable parameters in block 511b (raw coefficient consistency check).
[0112] In one embodiment, such braking consistency verification steps 509a, 509b include the following checks:
[0113] Maximum pressure p applied by the brake master cylinder maxHowever, the pressure must be above a predetermined value;
[0114] The duration of the brake detection time interval is longer than the reference time interval.
[0115] In other words, this feature accepts only brake events where pressure exceeds a predetermined threshold, or brake events with a duration exceeding a predetermined threshold (brake operation checks), thus eliminating "false brake events" and unimportant brake events.
[0116] In the subsequent steps 504a and 504b of both the recursive and non-recursive estimation, the supervisory block 21 performs consistency checks 511a and 511b on the raw coefficient values and decides whether to accept those values.
[0117] If these consistency checks 511a and 511b are successful, the supervisor block 21 continues low-pass filtering 506a and 506b on the relevant raw coefficients (low-pass filtering enabled).
[0118] After the low-pass filtering blocks 506a and 506b, the supervisor block 21 performs consistency verification or validity check 507a and 507b (consistency check of filtered coefficients) on the filtered coefficient values to determine whether to accept them or not.
[0119] In the recursive solution, the first check 507a is performed simultaneously with the check of the first brake operation 502a.
[0120] In one embodiment, for a plant model using a parabola represented by equation (4), this check includes the following: - Convexity of the parabola:
number
number
[0121] Next, in both the recursive and non-recursive cases, it is possible to define a first parametric function f' updated based on the verified coefficients VC0, ..., VCn (with output coefficients 510a and 510b updated).
[0122] The present invention also relates to vehicle brake systems 100, 200, 300, and 400, and includes the following:
[0123] At least one hydraulic actuator 1, 3, or electro-hydraulic actuator 4 of the disc brake 2.
[0124] At least one electronic processing unit 10, 10', 20, 20' connected to the at least one hydraulic 1, 3 or electro-hydraulic 4 actuator receives data representing measured values of pressure p and stroke x of the brake master cylinder actuated by the actuator during the brake detection time interval associated with each brake event. Here, at least one electronic processing unit 10, 10', 20, 20', 20a is configured to carry out the method of the present invention.
[0125] The present invention also implements a method of the present invention with respect to a computer program which includes application code loaded into memory and is executable by at least one electronic processing unit 10, 10', 20, 20', 20a of a vehicle brake system 100, 200, 300, 400.
[0126] Although this invention explicitly refers to vehicle braking systems employing hydraulic or electro-hydraulic actuators, similar solutions are applicable to pneumatic or electro-pneumatic braking systems. Furthermore, similar solutions can be applied to electromechanical systems in which pressure is converted into force.
[0127] To address incidental needs, those skilled in the art can modify or adapt the embodiments of the methods described above, or substitute elements with 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 described embodiments.
Claims
1. A method (500) for obtaining information regarding the wear state of friction material in a vehicle brake system (100; 200; 300; 400), wherein the brake system is At least one hydraulic (1, 3) or electro-hydraulic (4) actuator of the disc brake (2), - At least one electronic processing unit (10, 10', 20, 20', 20a) connected to the at least one hydraulic (1, 3) or electro-hydraulic (4) actuator, Includes at least one electronic processing unit (10, 10', 20, 20', 20a) connected to the hydraulic (1, 3) or electro-hydraulic (4) actuators, which receives data representing measured values of the pressure (p) of the brake master cylinder (2) actuated by the actuator and measured values of the stroke (x) of the brake master cylinder during the brake detection time interval associated with each brake event, The aforementioned method, Providing step (501) to provide at least one electronic processing unit (10, 10', 20, 20', 20a) a parametric function (f) representing the current state of the brake system (100; 200; 300; 400) of the vehicle, wherein the parametric function (f) is adapted as a function of one or more coefficients (θ0, ..., θn) to describe the relationship between the stroke (x) of the brake master cylinder and the brake pressure (p) applied by the brake master cylinder, providing step (501), After each brake sample is detected, a detection step (502) is performed in which the supervisor block (21) of the at least one electronic processing unit (10, 10', 20, 20', 20a) detects one or more brake samples during the brake detection time interval in order to activate the estimation block (22) of the at least one electronic processing unit (10, 10', 20, 20', 20a), The estimation block (22) receives a receiving step (503) in which, during the brake sampling period for each of the one or more brake samples, a first pressure measurement value (pi) of the brake master cylinder and a first stroke measurement value (xi) of the brake master cylinder, The estimation step (504) involves using the estimation block (22) to estimate a plurality of first coefficients (θi0, ..., θin) of the parametric function (f) associated with each brake sample based on the first pressure measurement (pi) of the brake master cylinder and the first stroke measurement (xi) of the brake master cylinder, The supervisory block (21) enables the filtering block (23) of at least one electronic processing unit (10, 10', 20, 20', 20a) at the end of the brake detection time interval in an activation step (505), The filtering step (506) involves filtering the plurality of first coefficients (θi0, ..., θin) associated with each brake sample using the filtering block (23) to generate a plurality of second filter coefficients (θ'0, ..., θ'n) provided to the supervisor block (21), The supervisor block (21) enables the plurality of second filter coefficients (θ'0, ..., θ'n) and generates an activation coefficient (VC0, ..., VCn) that defines a first parametric function (f') indicating the state of the brake system (100; 200; 300; 400) after the brake detection time interval, and A method (500) comprising: a first information generation step (508) of transmitting the activation coefficients (VC0, ..., VCn) to a wear estimation block (24) of the at least one electronic processing unit (10, 10', 20, 20', 20a) to generate first information (WI) representing the wear state of the friction material of the brake system (100; 200; 300; 400).
2. The method according to claim 1 (500), wherein the first information (WI) representing the wear state of the friction material of the brake system (100; 200; 300; 400) is a predefined function (g) calculated based on the activation coefficients (VC0, ..., VCn).
3. The receiving step (503) further includes the step of receiving a measured value of the brake fluid temperature (T) by the estimation block (22), The method according to claim 1 or 2 (500), wherein the parametric function (f) is adapted to describe the relationship between the stroke (x) of the brake master cylinder and the temperature of the brake fluid, together with the brake pressure (p) applied to the brake master cylinder.
4. The method (500) of any one of claims 1-3, comprising the step of transmitting the activation coefficients (VC0, ..., VCn) to a control adaptive block (25) of the at least one electronic processing unit (20a) to generate second information (CA) used by the at least one electronic processing unit (20a) to change one or more parameters controlled by the electronic processing unit (20a).
5. The parameter controlled by the at least one electronic processing unit (20a) is the value of the current pressure (p) of the brake master cylinder. The current pressure (p) is updated to equal the value of the reference pressure (p*) based on the control scheme (50). The control scheme (50) includes a feedforward FF block (51) in the first open-loop branch of the control scheme (50) and a proportional-integral-derivative (PID) block (52) in the second feedback branch of the control scheme (50). The feedforward FF block (51) is updated based on the second information (CA) generated according to the activation coefficients (VC0, ..., VCn), The method according to any one of claims 1-4 (500), wherein the gain of the proportional-integral-derivative (PID) block (52) is programmed based on the second information (CA) generated according to the activation coefficients (VC0, ..., VCn).
6. The method according to any one of claims 1 to 5 (500), wherein the filtering step (506) is performed in the brake operation region using a low-pass filter, in particular a first-order linear filter.
7. The detection step (502) includes a step of detecting the disclosure time and the end time of the brake detection time interval, The method (500) according to any one of claims 1 to 6, wherein the estimation step (504) includes the step of estimating a plurality of first coefficients (θi0, ..., θin), and the step of executing a recursive estimation algorithm between the start and end times of the brake detection time interval.
8. The detection step (502) includes detecting the start and end times of the brake detection time interval and storing the start and end times of the brake detection time interval, respectively. The method (500) according to any one of claims 1 to 7, wherein the estimation step (504) includes the step of estimating a plurality of first coefficients (θi0, ..., θin), and the step of executing a non-recursive estimation algorithm after the end of the brake detection time interval.
9. The step of detecting the start time of the brake detection time interval includes the step of detecting that the brake pressure (p) applied by the brake master cylinder is greater than a preset pressure value (pa), The method according to claim 7 or 8 (500), wherein the step of detecting the end moment of the brake detection time interval includes the step of detecting that the brake pressure (p) applied from the brake master cylinder is less than or equal to the preset pressure value (pa).
10. Furthermore, it includes verification steps (509a, 509b) to verify the consistency of braking, The aforementioned verification step is, The maximum pressure applied by the brake master cylinder is equal to or greater than a preset threshold pressure value. The method according to any one of claims 1 to 9 (500), comprising the step of verifying that the duration of the brake detection time interval is longer than a reference time interval.
11. The parametric function (f) and the first parametric function (f') have a parabolic pattern. The method according to any one of claims 1 to 10.
12. A vehicle brake system (100; 200; 300; 400), A disc brake (2) includes at least one hydraulic actuator (1, 3) or an electro-hydraulic actuator (4), The system includes at least one electronic processing unit (10, 10', 20, 20', 20a) connected to the at least one hydraulic actuator (1, 3) or electrohydraulic actuator (4), which receives data indicating a measured value (p) of the pressure of the brake master cylinder and a measured value (x) of the stroke of the brake master cylinder actuated by the at least one hydraulic actuator (1, 3) or electrohydraulic actuator (4) during a brake detection time interval associated with each brake event, The at least one electronic processing unit (10, 10', 20, 20', 20a) is configured to perform a method according to one or more of claims 1-11, in a vehicle brake system (100; 200; 300; 400),
13. A computer program that includes application code stored in memory and executable by electronic control units (10, 10', 20, 20', 20a) of a vehicle's brake system (100; 200; 300; 400), and implements the method according to claim 1-11.