Method and system for detecting and measuring the braking force of a vehicle's brake system using a photonic sensor integrated into the brake pad.

Abstract

A method and system for detecting and measuring the braking force of a vehicle's brake system using photonic sensors integrated into brake pads is described. A method for detecting and measuring the clamping force (CF) and / or brake torque (BT) resulting from the operation of a vehicle's friction brake system by detection performed in the brake pads (10) of the brake system is described. The method includes encapsulating at least one optical fiber strain sensor (2) in a casing (9) and incorporating the casing (9) into a respective portion of a friction-sensitive friction material (M) attached to a base plate or platform (11) of the brake pad (10). The shear strain (St-eff) of the casing (9) acting in a tangential reference direction (x) represents the tangential force (Ft) acting on the brake pad (10), and the normal force (Fn-eff) of the casing (9) acting in a normal reference direction (y) represents the normal force (Fn) acting on the brake pad (10). The method includes detecting, by the optical fiber strain sensor 2, a first strain S1 (present at a first location on the casing along a first spatial direction w1) based on both a normal force Fn-eff and a tangential strain St-eff acting on the casing 9 at the first location, and detecting, by the optical fiber strain sensor 2, a second strain (present at a second location on the casing along a second spatial direction w2) based on both the normal force Fn-eff and the tangential strain St-eff acting on the casing 9 at the second location. The method includes generating, by the optical fiber strain sensor 2, a first photonic signal L1 representative of the first detected strain S1 and a second photonic signal L2 representative of the second detected strain S2, and receiving, by an optical reading / interrogation unit 4 optically connected to the optical fiber strain sensor 2, the first photonic signal L1 and the second photonic signal L2. The method ultimately involves determining, by the optical reading / interrogation unit 4, a value of the first strain S1 and a value of the second strain S2, respectively, based on the first received optical signal L1 and the second received optical signal L2, and determining a measurement value of the clamping force CF and / or the brake torque BT based on the determined values ​​of the first strain S1 and the second strain S2.

Description

[Technical Field]

[0001] The present invention relates to a method and system for detecting and measuring the clamping force and / or braking force of a vehicle brake system using a photonic sensor (i.e., an optical fiber sensor) incorporated into a brake pad.

[0002] The present invention further relates to a brake pad equipped with a sensor to enable the implementation of the aforementioned method. [Background technology]

[0003] To control, monitor, and operate the brake system, it is extremely helpful for electronically controlled disc brake systems to know, in real time and as accurately as possible, the value of the clamping force or brake torque (and preferably both) applied by the brake calipers of the brake system during braking.

[0004] However, it is difficult to directly, accurately, and reliably measure the clamping force and / or braking torque applied by the brake calipers of the brake system.

[0005] An indirect but potentially effective option for measuring clamping force and / or brake torque is to measure the force or other related quantity acting within the brake pads belonging to the brake caliper, generated by the brake caliper during a braking event.

[0006] For this purpose, it is desirable to incorporate force sensors and / or other sensors of other force-related quantities (e.g., strain) that can detect and provide such information in the brake pad itself.

[0007] However, force and / or strain sensors made available by known technologies are not suitable for integration into brake pad bodies because they are not small enough and compact, or they cannot be easily connected externally for operation, or they are too sensitive to readings or temperature changes, or they are not robust enough to operate at high temperatures, and furthermore, they are unsuitable for operation in environments exposed to considerable temperature fluctuations, such as brake pads.

[0008] At least some of the aforementioned drawbacks apply, for example, to known force and / or strain sensors based on piezoelectric or piezoelectric resistance phenomena.

[0009] Given this, it is possible to attempt to indirectly estimate and / or calculate the values ​​of clamping force and / or brake torque based on the detection of other quantities, or based on the detection of forces performed outside the brake pads or caliper itself. However, this introduces further drawbacks stemming from the fact that such estimations or calculations do not fully meet the required accuracy.

[0010] While the field of sensor technology offers a wide range of solutions, known solutions provide sensors that cannot be easily integrated into brake pads from a practical standpoint (due to being not compact enough, too complex and invasive, or not robust enough to temperature), or sensors that provide indirect measurements that cannot obtain clamping force and / or brake torque values ​​with sufficient accuracy.

[0011] Therefore, there is a need for a force sensor or a sensor of other quantities (e.g., strain) related to clamping force and / or brake torque, which is compact, miniaturized, easy to operate / read, suitable for actual integration into the brake pad body, and capable of determining the clamping force and / or brake torque (and / or both) applied by the brake caliper with high accuracy, high reliability, and in real time, in all environments and operating conditions, without affecting performance in any way.

[0012] As described above, such requirements are not fully met by conventional technologies or currently available solutions. [Overview of the project]

[0013] The object of the present invention is to provide a method for detecting and measuring clamping force and / or brake torque resulting from the operation of a vehicle-specific friction brake system by detection performed on the brake pads of the brake system. This makes it possible to at least partially improve upon the aforementioned disadvantages described with reference to the prior art and to satisfy the aforementioned requirements that are particularly felt in the art.

[0014] This and other objectives are achieved by the method for detecting and measuring clamping force and / or brake torque as described in claim 1.

[0015] Some preferred embodiments of such a method are the subject of dependent claim 2-21.

[0016] A further object of the present invention is to provide a sensor-equipped brake pad for a brake caliper of a vehicle brake system, which is equipped to enable the aforementioned method for detecting and measuring clamping force and / or braking torque according to claims 1-21.

[0017] These and other objects are achieved by the brake pad with a sensor according to claim 22.

[0018] Some preferred embodiments of such pads are the subject of dependent claims 23 to 34.

[0019] A further object of the present invention is to provide a brake caliper for a brake system including at least one of the aforementioned pads with a sensor.

[0020] These and other objects are achieved by the brake caliper according to claim 35.

[0021] A further object of the present invention is to provide for detecting and measuring the clamping force and / or the braking torque by detection carried out on at least one brake pad of a brake system using at least one of the aforementioned pads with a sensor.

[0022] This object and other objects are achieved by a system for detecting and measuring the clamping force and / or the braking torque according to claim 36.

[0023] Some preferred embodiments of such a system are the subject of dependent claims 37 to 45.

[0024] A further object of the present invention is to provide a brake system that uses at least one of the aforementioned pads with a sensor or uses the aforementioned system to detect and measure the clamping force and / or the braking torque.

[0025] These and other objects are achieved by the brake system according to claim 46.

[0026] Further features and advantages of the method and system according to the present invention will become apparent from the following description of its preferred embodiments, given by way of non - limiting example, with reference to the accompanying drawings. [Brief explanation of the drawing]

[0027] [Figure 1] Figure 1 shows some simplified structural and functional aspects of a method and system for detecting and measuring clamping force and / or brake torque according to an embodiment of the present invention. [Figure 2] Figure 2 shows some simplified structural and functional aspects of a method and system for detecting and measuring clamping force and / or brake torque according to an embodiment of the present invention. [Figure 3] Figure 3, in a functional block diagram, shows different embodiments of the sensor-equipped brake pad according to the present invention and the system for detecting and measuring clamping force and / or brake torque. [Figure 4] Figure 4, in a functional block diagram, shows different embodiments of the sensor-equipped brake pad according to the present invention and the system for detecting and measuring clamping force and / or brake torque. [Figure 5] Figure 5, in a functional block diagram, shows different embodiments of the sensor-equipped brake pad according to the present invention and the system for detecting and measuring clamping force and / or brake torque. [Figure 6] Figure 6, in a functional block diagram, shows different embodiments of the sensor-equipped brake pad according to the present invention and the system for detecting and measuring clamping force and / or brake torque. [Figure 7A] Figure 7A shows details of each embodiment of a pre-formed casing including a sensor adapted to be incorporated into a sensor-equipped pad, according to a particular embodiment of the present invention. [Figure 7B] 7B details each embodiment of a pre-formed casing including a sensor adapted to be incorporated into a sensor-equipped pad, according to a particular embodiment of the present invention. [Figure 8A]Figure 8A shows details of each embodiment of a pre-formed casing containing a sensor adapted to be incorporated into a sensor-equipped pad, according to a particular embodiment of the present invention. [Figure 8B] Figure 8B shows details of each embodiment of a pre-formed casing containing a sensor adapted to be incorporated into a sensor-equipped pad, according to a particular embodiment of the present invention. [Figure 9] Figure 9 is a side view of a brake pad with a sensor according to an embodiment of the present invention. [Figure 10] Figure 10 shows further embodiments of the sensor-equipped brake pad, in particular showing possible positions of the sensor within the brake pad according to different embodiments. [Figure 11] Figure 11 shows further embodiments of the sensor-equipped brake pad, in particular showing possible positions of the sensor within the brake pad according to different embodiments. [Figure 12] Figure 12 shows further embodiments of the sensor-equipped brake pad, in particular showing possible positions of the sensor within the brake pad according to different embodiments. [Figure 13] Figure 13 shows further embodiments of the sensor-equipped brake pad, in particular showing possible positions of the sensor within the brake pad according to different embodiments. [Figure 14] Figure 14 shows further embodiments of the sensor-equipped brake pad, in particular showing possible positions of the sensor within the brake pad according to different embodiments. [Figure 15] Figure 15 is a functional block diagram of each embodiment of the optical reading / interrogation unit included in the aforementioned system for detecting and measuring clamping force and / or brake torque. [Figure 16] Figure 16 is a functional block diagram of each embodiment of the optical reading / interrogation unit included in the aforementioned system for detecting and measuring clamping force and / or brake torque. [Figure 17]Figure 17 is a functional block diagram of each embodiment of the optical reading / interrogation unit included in the aforementioned system for detecting and measuring clamping force and / or brake torque. [Figure 18] Figure 18 is a functional block diagram of each embodiment of the optical reading / interrogation unit included in the aforementioned system for detecting and measuring clamping force and / or brake torque. [Figure 19] Figure 19 shows an embodiment of the brake system according to the present invention, which includes multiple sensor-equipped brake pads belonging to multiple brake calipers of the brake system. [Modes for carrying out the invention]

[0028] The following describes a method for detecting and measuring the clamping force CF and / or brake torque BT originating from the operation of the vehicle's friction brake system by detection performed on the brake pads of the brake system 10.

[0029] Referring particularly to Figures 1 to 3, this method first includes the steps of encapsulating at least one optical fiber strain sensor 2 in a casing 9 and incorporating the aforementioned casing 9 into each portion of the friction material that adheres to the base plate or platform 11 of the brake pad 10.

[0030] Such portions of the friction material M are sensitive to friction, and as a result, the shear strain (i.e., tangential strain) St-eff that the casing 9 experiences in the tangential direction x represents the tangential force Ft acting on the brake pad, and as shown in Figure 10, the normal force Fn-eff that the casing 9 experiences in the normal direction y represents the normal force Fn acting on the brake pad 10.

[0031] The tangential and normal directions (x, y) refer to the direction of force acting on the brake pads.

[0032] Next, this method detects a first strain S1 present at a first position of the casing 9 along a predefined first spatial direction w1 using at least one optical fiber strain sensor 2, and further detects a second strain S2 present at a second position of the casing 9 along a predefined second spatial direction w2 using at least one optical fiber strain sensor 2.

[0033] At least one optical fiber strain sensor is configured such that the first strain S1 described above depends on both the normal force Fn-eff and the tangential strain St-eff acting on the casing 9, and the second strain S2 described above depends on both the normal force Fn and the tangential strain St-eff acting on the casing 9.

[0034] As described above, this method provides dual detection, each containing strain information representing both the normal and tangential force components acting at the respective location (these forces ultimately depend on the clamping force and / or brake torque applied by the brake caliper).

[0035] Next, the method includes the step of generating a first photonic signal L1 representing a first detected strain S1 and a second photonic signal L2 representing a second detected strain S2 using an optical fiber strain sensor 2. Then, the optical reading / interrogation unit 4, which is optically connected to the optical fiber strain sensor 2, receives the first photonic signal L1 and the second photonic signal L2.

[0036] This method ultimately determines the values ​​of the first strain S1 and the second strain S2, respectively, by the optical reading / interrogation unit 4 based on the aforementioned first received optical signal L1 and second received optical signal L2, and determines the measured values ​​of the clamping force CF and / or brake torque BT based on the determined values ​​of the first strain S1 and the second strain S2.

[0037] According to one embodiment of this method, the aforementioned optical fiber strain sensor 2 is a fiber Bragg grating type sensor, and the aforementioned predetermined first spatial direction w1 and second spatial direction w2 are directions different from the tangential direction x and the normal direction y.

[0038] According to a possible embodiment, the first spatial direction w1 and the second spatial direction w2 are symmetric with respect to the normal reference direction y, i.e., they form complementary angles with respect to the positive tangent reference direction x.

[0039] According to another embodiment (shown in Figures 2 and 3, and in particular the reference system shown in Figure 3 in the upper right), the angle β formed by the first spatial direction w1 and the positive direction of the tangent reference direction x is equal to the angle β formed by the second spatial direction w2 having a negative tangent reference direction x.

[0040] According to another embodiment of this method, the aforementioned optical fiber strain sensor 2 is a fiber Bragg grating type sensor placed on a birefringent fiber.

[0041] In this case, the predefined first spatial direction w1 coincides with the tangent reference direction x, and the aforementioned second spatial direction w2 is perpendicular to the tangent reference direction x.

[0042] According to an embodiment of this method (for example, shown in Figures 2 to 6), the optical fiber strain sensor 2 includes a first sensor element 21 and a second sensor element 22.

[0043] The first sensor element 21 includes a first fiber Bragg grating positioned at the first location described above within a first portion of an optical fiber that is arranged to align with the first spatial direction w1 described above.

[0044] The second sensor element 22 includes a second fiber Bragg grating positioned at the aforementioned second location within a second portion of an optical fiber that is arranged to align with a second spatial direction w2.

[0045] According to the embodiment (shown in Figures 5 and 6), the aforementioned first sensor element 21 and second sensor element 22 are contained within a single optical fiber 25.

[0046] According to another embodiment (shown in Figures 3 and 4), the aforementioned first sensor element 21 and second sensor element 22 are contained within two different optical fibers 25.

[0047] According to one embodiment of this method, the determination step involves the optical reading / questioning unit 4 generating a first electrical signal E1 representing a first photonic signal L1 and a second electrical signal E2 representing a second photonic signal L2, then transmitting the aforementioned first electrical signal E1 and second electrical signal E2 to the control unit 20, and finally, the processor of the control unit 20 calculating the clamping force CF and / or brake torque BT based on the aforementioned first electrical signal E1 and second electrical signal E2 by one or more algorithms executed by one or more software programs.

[0048] According to an embodiment of this method, the aforementioned calculation step includes calculating the brake torque BT based on a differential strain ΔS given by the difference between a first strain S1 and a determined value of a second strain S2, using a proportionality constant that depends on geometric parameters related to the arrangement of sensors in the reference directions x, y, geometric parameters related to the position of the pads and sensors within the pads, and parameters representing the coefficient of friction of the material from which the casing and friction material are made.

[0049] For example, the calculation steps described above can be based on the following ratio (Equation 1) between the derivative value ΔS and the brake torque BT.

[0050]

number

[0051] Here, β: angles w1, w2 relative to the sensor direction; ν: Poisson's ratio of the casing material; k geom : A constant that depends on the shape of the pad; r: Effective radius of the sensor position; E HM : Young's modulus of the casing material; E FM : Young's modulus of friction materials; TIFF0007857757000002.tif10129

[0052] According to one embodiment of this method, the calculation step includes calculating a clamping force CF, i.e., a normal force acting on the brake pad, based on a normal force or pressure (e.g., Fn-eff) acting on the casing incorporated into the brake pad.

[0053] The aforementioned normal force or pressure Fn-eff acting on the casing is calculated based on the detected first strain S1 and / or second strain S2, using geometric parameters relating to the arrangement in the reference directions x, y and a proportionality constant that depends on the Young's modulus of the friction material. For example, the calculation steps described above can be based on the following relationship (Equation 2) between the average of the calculated strains (S1 and S2) and the clamping torque CF.

[0054]

number

[0055] According to one embodiment (for example, shown in Figures 4 to 6), the method includes the steps of: encapsulating an optical fiber temperature sensor 5 in a casing 9 at a third position located near the aforementioned first and second positions; then, using the optical fiber temperature sensor 5 to detect the temperature present at the third position T and generating a third photonic signal LT representing the detected temperature; then, receiving the aforementioned detected third photonic signal LT by an optical reading / interrogation unit 4 optically connected to the optical fiber strain sensor 5; and finally, determining a temperature value T based on the third received photonic signal LT by the optical reading / interrogation unit 4.

[0056] In this case, the step of determining the measured values ​​of clamping force CF and / or brake torque BT includes determining the measured values ​​of clamping force CF and / or brake torque BT based on a first strain S1 and a second strain S2, and a determined temperature value T.

[0057] According to this embodiment, the optical fiber temperature sensor 5 is a fiber Bragg grating optical fiber temperature sensor.

[0058] According to a preferred embodiment, the aforementioned optical fiber strain sensor and temperature sensor are integrated with each other. More specifically, if the two FBG strain sensors are contained within the same optical fiber 25 (as shown in Figures 5, 6, and 7A), then the aforementioned temperature sensor is also contained within the same optical fiber 25.

[0059] For example, an optical fiber temperature sensor comprises a third sensor element 23, which includes a third fiber Bragg grating obtained in an optical fiber containing a first sensor element 21 and a second sensor element 22. Such a third Bragg grating in an optical fiber is assembled in a casing in a suitable cavity and / or capillary tube 71 so as not to be affected by thermal expansion and deformation of the material in which it is placed.

[0060] According to another embodiment, if the two strain sensor FBGs are composed of two different optical fibers, the temperature sensor includes a third fiber Bragg grating made on one of the two fibers, including the first or second fiber Bragg grating of the strain sensor, at a third position different from the first or second position, located in the friction material outside the casing, or at a third position located in the fiber stretch included in the casing (see Figure 4). In either case, such a third fiber Bragg grating is inserted into the cavity or capillary tube 71 of the casing to isolate it from possible thermal expansion and deformation phenomena of the material in which it is encapsulated.

[0061] According to another embodiment (not shown in the figure), the optical fiber temperature sensor includes, in addition to the optical fiber containing a first optical sensor element 21 and a second sensor element 22, a third sensor element 23, which includes a third fiber Bragg grating made of a dedicated optical fiber. Such a third Bragg grating in a dedicated optical fiber is assembled within a casing in a suitable cavity and / or capillary tube 71 so as not to be affected by thermal expansion and deformation of the material in which it is placed.

[0062] The aforementioned fiber Bragg grating optical sensor (hereinafter also referred to as "FBG sensor") is the type of sensor shown below.

[0063] FBG sensors are known to be highly sensitive and versatile optical devices for measuring various physical parameters such as strain and temperature. In its simplest form, an FBG sensor is obtained by spatially periodic modulation of the refractive index etched into the core of an optical fiber (which can be obtained, for example, using a photosensitive phenomenon or femtosecond optical pulses).

[0064] The FBG sensor is λ B =2n eff The so-called "Bragg wavelength" λ is defined as Λ. BUtilize the existence of resonance conditions for reflecting incident light. Here, n eff is the effective refractive index of the fundamental mode of the optical fiber, and Λ is the spatial pitch (periodicity) of the grating.

[0065] The operating principle of the FBG sensor is that changes in the effective refractive index or grating pitch caused by external influences such as strain and temperature result in respective shifts Δλ B of the operating wavelength (Bragg wavelength) derivable from Equation 3.

[0066]

Equation

[0067] Here, Δλ B =λ - λ B : Change in the Bragg wavelength with respect to the reference Bragg wavelength λ B ; k: Scale coefficient; α T : Is the thermo-optic coefficient.

[0068] The Bragg wavelength shift depends linearly on the longitudinal strain ε with a sensitivity value of approximately 1.2 pm / με and a temperature change with a sensitivity value of approximately 11 pm / °C for a silicon fiber in the range of 1550 nm.

[0069] As described above, it is appropriate to correct the strain results obtained by the FBG sensor with respect to temperature changes under the operating conditions of the FBG sensor (2) incorporated in the casing. Such compensation can be performed by expanding the aforementioned Equation 1 as shown in Equation 4 below.

[0070]

Equation

[0071] Here, ε = ε M + ε TThis includes two contributions: one from pure mechanical strain and the other from thermal expansion ε T This is the contribution caused by (α SP λ is the thermal expansion coefficient of the material. B The reference Bragg wavelength and reference temperature are shown in T0, and the real-time values ​​of wavelength and temperature can be expressed using equation 5, where λ and T are λ and T, respectively.

number

[0072] From this equation 5, we can see the pure mechanical influence ε M This is obtained using equation 6.

[0073]

number

[0074] Real-time temperature value (ε M The correction value (to be entered into the above formula) is obtained via an additional FBG sensor (i.e., temperature sensor 5) sealed in a loose tube located near FBG strain sensor 2.

[0075] In particular, according to an embodiment of this method, the step of determining the measured values ​​of clamping force CF and / or brake torque BT is to calculate the strain value due to thermal fluctuations based on the determined temperature, subtract the strain value due to thermal fluctuations from the overall measured value of the first strain to obtain a first effective strain value that depends solely on mechanical effects, subtract the strain value due to thermal fluctuations from the overall measured value of the second strain to obtain a second effective strain value that depends solely on mechanical effects, and determine the measured values ​​of brake force and / or brake torque based on the first effective strain and the second effective strain values.

[0076] An FBG sensor is a "passive" sensor. That is, it does not require power and is activated by illumination, which involves sending photoactive radiation at an appropriate wavelength (such as the Bragg wavelength) through the optical fiber to the portion of the optical fiber containing the sensor's grating. In response, the FBG sensor reflects or transmits an optical (i.e., photonic) signal. This depends not only on the incident radiation but also on the strain experienced by the grating itself. Such a photonic signal may be a transmitted optical signal (i.e., an optical spectrum) or a reflected optical signal (i.e., an optical spectrum) in different embodiments of the methods described below.

[0077] According to one embodiment of this method, the optical fiber strain sensor 2 and / or optical fiber temperature sensor 5 are connected to the optical reading / interrogation unit 4 by the connecting optical interface 3.

[0078] According to the embodiment, each connection between each fiber from which a fiber Bragg grating type sensor is obtained and the respective connecting optical fiber to the optical reading / interrogation unit is made by a fiber splice or a removable photonic connecting element (optical connector).

[0079] According to the embodiment, the aforementioned first photonic signal L1 includes a first optical spectrum reflected or transmitted by the first sensor element 21, which reaches the optical reading / interrogation unit 4 via the connected optical interface 3.

[0080] According to the embodiment, the aforementioned second photonic signal L2 includes a second optical spectrum reflected or transmitted by the second sensor element 22, which reaches the optical reading / interrogation unit 4 via the connected optical interface 3.

[0081] According to the embodiment, the aforementioned third photonic LT signal includes a third optical spectrum reflected or transmitted by the third sensor element 23, which reaches the optical reading / interrogation unit 4 via the optical connection interface 3. (In the embodiment, the optical connection interface is the same optical fiber in which the optical fiber temperature sensor is located, and can be identified together with one or both FBG optical fiber strain sensors, extending outward to form the optical interface. Or, in another embodiment, it is an optical fiber connected to the aforementioned optical fiber containing the sensors.)

[0082] According to one embodiment of this method, the optical reading / questioning unit 4 is configured to activate the first sensor element 21 and / or the second sensor element 22 and / or the third sensor element 23 by sending photoactive radiation OA or the respective photoactive radiation OA1, OA2, OAT) via the connected optical interface 3.

[0083] According to one embodiment (for example, shown in Figures 5 and 6) applicable when multiple sensor elements 21, 22 are fabricated on the same fiber and each of the respective fiber Bragg gratings is associated with its respective different central operating wavelengths (λ1, λ2), the optical reading / interrogation unit element 4 includes the further step of transmitting its respective photoactive radiations OA1, OA2 at central operating wavelengths λ1, λ2 to the multiple sensor elements 21, 22 via the connecting optical interface 3 using wavelength division multiplexing (WDM) transmission technology. The method also includes a first step of distinguishing the respective optical spectra received via the connecting optical interface 3 and reflected or transmitted by each of the multiple sensor elements 21, 22 by demultiplexing using wavelength division multiplexing (WDM). According to an embodiment of this method (for example, shown in Figure 3), when multiple sensor elements are made in the same optical fiber and the photonic signals emitted by the sensors include transmitted light spectra, the connecting optical interface 3 includes an input connecting optical fiber 32 shared by wavelength-multiplexed first OA1 and / or second OA2 photoactive radiation, and an output connecting optical fiber 33 shared by transmitted light spectra forming wavelength-multiplexed first photonic signal L1 and / or second photonic signal L2 and / or third photonic signal.

[0084] Applicable when multiple sensor elements 21, 22, and 23 are made of the same optical fiber 25, and each of the respective fiber Bragg gratings is associated with a different central operating wavelength (λ1, λ2, λT), according to one embodiment (for example, shown in Figures 5 and 6), the method includes the further step of transmitting each of the photoactive radiations OA1, OA2, OAT by optical reading / interrogation unit element 4 via the connected optical interface 3 using wavelength division multiplexing (WDM) transmission technology. The method includes the further step of distinguishing the respective optical spectra received via the connected optical interface 3 and reflected or transmitted by each of the multiple sensor elements 21, 22, and 23 by demultiplexing using wavelength division multiplexing (WDM) technology.

[0085] According to an implementation of a method applicable when multiple sensor elements are made from the same fiber and the photonic signals emitted by the sensors include reflected light spectra (for example, the method shown in Figure 6), the connected optical interface 3 is shared by wavelength-multiplexed first photoactive radiation OA1 and / or second photoactive radiation OA2 and third OAT photoactive radiation, and by the reflected spectra that form wavelength-multiplexed first photonic signal L1, second photonic signal L2 and third LT photonic signal.

[0086] According to another embodiment of this method (not shown in the figure), the connecting optical interface 3 comprises one or more connecting optical fibers (31, 34) dedicated to the reflected optical spectra that form the photonic signals between the respective photoactive radiations between the first photoactive radiation OA1, the second photoactive radiation OA2, and / or the third OAT photoactive radiation, and the first photonic signal L1 and / or the second photonic signal L2 and / or the third photonic signal LT.

[0087] According to a particular modification of the embodiment, each connection between the fiber from which the fiber Bragg grating is obtained and the respective connecting optical fibers to the optical read / question unit is made by a fiber splice or a removable photonic connection element.

[0088] In the implementation of this method, the casing 9 is made of a polymer or mineral material and, unlike the brake pad 10, can be fixed therein and / or incorporated therein, has a predetermined shape and dimensions, and is adapted to accommodate at least one optical fiber strain sensor 2 and an optical fiber temperature sensor 5, as well as at least a portion of the optical connection interface 3.

[0089] In this case, the encapsulation step includes embedding at least one optical fiber strain sensor 2 in the casing 9 at a predefined position fixed to the aforementioned portion of the friction material M during the manufacture of the brake pad, further incorporating the casing 9 into the brake pad 10 and / or fixing it to the brake pad 10.

[0090] According to one embodiment, the step of embedding at least one optical fiber strain sensor 2 in the casing 9 includes incorporating one or more optical fibers 25, 26, including the optical fiber sensors 2, 5, into a given portion 71 of the casing 9 configured to orient and route the optical fibers in the correct position using an adhesive 7.

[0091] Next, the method includes the step of embedding one or more connecting fibers of the optical interface 3 in a capillary connecting tube 73, which is configured to be routed onto the brake pad toward a collector 74, into a specific casing portion 71 of the casing 9 using adhesive 7. The collector 74 is fixed to the brake pad and connectable to a protective output tube of the optical connecting interface 30 which is connectable to a read / question unit 4 outside the brake caliper.

[0092] Figures 7A and 8A (and enlarged details of Figures 7B and 8B respectively) show two possible embodiments of incorporating the strain sensor 2 within the casing 9 by adhesive 7, and also within the casing 9 and the capillary connecting tube 73.

[0093] In the embodiment described above, the casing 9 and capillary connecting tube 73, which include the aforementioned at least one optical fiber strain sensor 2 fixed to the inside of a suitable portion 71 by adhesive 7, form a detection element 90 (shown in Figure 9).

[0094] In Figures 10 to 13, the detection element 90, collector 74, and frame 75 are shown in several examples of brake pads with sensors. Figures 11 to 13 show embodiments of brake pads incorporating one, two, and three detection elements 90 (each having its own frame 75), respectively.

[0095] Figure 14 shows a structural configuration of the detection element 90 in an embodiment equipped with a birefringent fiber fb.

[0096] According to different possible embodiments, the casing 9 is made of mineral and / or plastic and / or polymer material and / or resin compound.

[0097] According to a possible embodiment, the casing (or housing) 9 has a substantially parallelepiped shape and dimensions of several tens of millimeters or several millimeters.

[0098] According to a particular embodiment, the casing 9 has dimensions of 20 mm base width, 12 mm base height, and a thickness of 4 mm or more.

[0099] According to the embodiment, the aforementioned step of encapsulation includes incorporating at least one optical fiber strain sensor 2 by either assembly with an adhesive or direct integral molding of the casing 9.

[0100] According to an embodiment (for example, shown in Figure 9), this method provides for incorporating the aforementioned sensing element 90, together with the aforementioned collector 74 and frame 75, into the friction material of the brake pad 12, between the base platform 11 and the casing 9, by shape coupling or mechanical coupling, at a fixed, predetermined position on the base platform (or plate) 11 of the brake pad, for fixing to and / or integration into the brake pad 10. As a result, at least one optical fiber strain sensor 2 is fully integrated at the desired position in the friction material.

[0101] According to one embodiment, the steps of the method are performed on one or both pads 10 of a disc brake caliper, each pad 10 comprising its respective optical reading / questioning unit 4 associated with and / or bound to it.

[0102] According to another embodiment, the steps of this method are performed on both pads 10 of the disc brake caliper, and the aforementioned steps of receiving and generating are performed operationally by a single optical reading / questioning unit 4 associated with the brake caliper and operationally coupled to both pads by a single optical interface 3 or two separate optical interfaces 3.

[0103] According to another embodiment (for example, shown in Figure 19), the steps of this method are performed on both brake pads of multiple disc brake calipers of the vehicle brake system. The aforementioned receiving and generating steps are also performed by one or more optical reading / questioning unit units 4 which are operably connected to the brake pads of all brake calipers of the aforementioned multiple disc brake calipers of the vehicle brake system.

[0104] According to different embodiments, this method includes one or more of the further steps listed below. Based on the time evolution of the measured first strain S1 and second strain S2, measure the real-time trends of the clamping force CF and / or brake torque BT in dynamic measurements, and / or • To detect a failure in the optical fiber sensors 2,5; and / or Based on the detection performed by the optical fiber sensors 2 and 5, the pad wear level 10 is reduced, and / or Based on detection performed by optical fiber sensors 2 and 5, estimate the level of foreign matter released by brake friction, and / or During a braking event, based on measurements taken by optical fiber sensors 21, 22 on both pads of the brake caliper, the brake pressure is measured, the effective friction coefficient of the brake is calculated, the actual clamping force of the brake caliper is calculated, and / or • During a braking event, measure the brake pressure imbalance of a brake caliper or the pads of one or more brake calipers based on measurements taken on the pads of one or more brake calipers by optical fiber sensors 2,5, and / or - During a braking event, the system detects malfunctions of one or more brake caliper pads based on detections made by optical fiber sensors 2 and 5 on one or more pads of one or more brake calipers.

[0105] Next, with reference again to Figures 1 to 19, a sensor-equipped brake pad 10 (or sensor-equipped pad 10) for a friction brake caliper of a vehicle brake system according to the present invention will be described.

[0106] Such a sensor-equipped pad 10 (for example, shown in Figure 3 or Figure 10) comprises a brake pad 1 made of a material adapted to generate brake friction when it comes into contact with a friction brake disc by a brake caliper during a braking event. Furthermore, the pad 10 comprises a casing 9 containing at least one optical fiber strain sensor 2 incorporated into a portion of the friction material M of the brake pad 10, which is bonded to a base plate or platform 11 of the brake pad 10, and a connecting optical interface.

[0107] Since the friction material M is sensitive to friction, the shear strain St-eff acting on the casing 9 from the tangential reference direction x (i.e., the tangential direction) represents the tangential force Ft acting on the sensor-equipped brake pad 10. The normal force Fn-eff acting on the casing 9 from the normal reference direction y represents the normal force Fn acting on the sensor-equipped brake pad 10, and represents the clamping force CF and / or brake torque Bt applied to the brake disc.

[0108] At least one optical fiber strain sensor 2 is configured to perform the following operations: to detect a first strain S1 present at a first position of the casing 9 along a predefined first spatial direction w1, where such first strain S1 depends on a normal force Fn-eff and a tangential force St-eff acting on the casing 9; and to detect a second strain S2 present at a second position of the casing 9 along a predefined second spatial direction w2, where such second strain S2 depends on a normal force Fn-eff and a tangential force St-eff acting on the casing 9; and further, to generate a first photonic signal L1 representing the first detected strain S1 and a second photonic signal L2 representing the second detected strain S2.

[0109] The optical connection interface 3 is connected to the optical fiber strain sensor 2 and to the optical reading / interrogation unit 4, and is configured to transmit the aforementioned first photonic signal L1 and second photonic signal L2.

[0110] According to the embodiment of the sensor-equipped pad 10, the optical fiber strain sensor 2 is a fiber Bragg grating type sensor, and the aforementioned predetermined first spatial direction w1 and second spatial direction w2 are different directions from the aforementioned tangential reference direction x and normal reference direction y.

[0111] According to an embodiment of the sensor-equipped pad 10, the first spatial direction w1 and the second spatial direction w2 are symmetric with respect to the normal reference direction y.

[0112] According to another embodiment of the sensor-equipped pad 10, the first spatial direction w1 and the second spatial direction w2 form angles complementary to the positive direction of the reference direction x.

[0113] According to another embodiment of the sensor-equipped pad 10, the angle β formed by the positive direction of the tangential reference direction x and the first spatial direction w1 is equal to the angle β formed by the negative tangential reference direction x and the second spatial direction w2.

[0114] According to another embodiment of the sensor-equipped pad 10, the aforementioned optical fiber strain sensor 2 is a fiber Bragg grating type sensor placed on a birefringent fiber.

[0115] In this case, the predefined first spatial direction w1 coincides with the tangent reference direction x, and the aforementioned second spatial direction w2 is perpendicular to the tangent reference direction x.

[0116] According to an embodiment of the sensor-equipped pad 10 (for example, shown in Figures 3 to 6), the optical fiber strain sensor 2 includes a first sensor element 21 comprising a first fiber Bragg grating positioned at a first location in a first portion of an optical fiber arranged to align with the aforementioned first spatial direction w1, and a second sensor element 22 comprising a second fiber Bragg grating positioned at a second location in a second portion of an optical fiber arranged to align with the second spatial direction w2.

[0117] According to one embodiment, the first sensor element 21 and the second sensor element 22 are contained within a single optical fiber 25.

[0118] According to another embodiment, the first sensor element 21 and the second sensor element 22 are contained in two different optical fibers 25 and 26, respectively.

[0119] According to other possible embodiments, the sensor elements included in the optical fiber strain sensor (i.e., strain sensor assembly) include any number of sensor elements, more than two.

[0120] According to one embodiment (for example, shown in Figures 4 to 6), the sensor-equipped pad 10 further comprises at least one optical fiber temperature sensor 5 encapsulated in the casing 9 at a third position close to the first and second positions described above.

[0121] At least one optical fiber temperature sensor 5 is configured to detect the temperature present at a third location and generate a third photonic signal LT representing the detected temperature.

[0122] In this case, the connected optical interface 3 is further connected to the optical fiber strain sensor 5 and to the optical reading / interrogation unit 4, and is configured to also transmit a third photonic signal LT.

[0123] According to one embodiment, the optical fiber temperature sensor is a fiber Bragg grating optical fiber temperature sensor.

[0124] According to the embodiment, the aforementioned optical fiber strain sensor and temperature sensor are integrated with each other.

[0125] According to one embodiment, the optical fiber temperature sensor 5 is an optical fiber temperature sensor of the fiber Bragg grating type and includes a third sensor element 23 consisting of a third fiber Bragg grating obtained in an optical fiber 25, which includes the aforementioned first sensor element 21 and second sensor element 22. Such a third Bragg grating in a dedicated optical fiber is assembled in a suitable cavity and / or capillary tube 71 within a casing so as not to be affected by thermal expansion and deformation of the material in which it is placed.

[0126] According to another embodiment, the optical fiber temperature sensor 5 is a fiber Bragg grating type optical fiber temperature sensor, which is one of an optical fiber (25, 26) including a first or second strain sensor of the fiber Bragg grating type, obtained at a third position, different from the first or second position, located outside the casing and positioned in the friction material or fiber portion inside the casing, and includes a third sensor element 23 consisting of a third fiber Bragg grating. In either case, the third fiber Bragg grating is inserted into the cavity of the casing or into the capillary tube 71 and is isolated from the possible thermal expansion and deformation phenomena of the material it encapsulates.

[0127] According to one embodiment, the sensor-equipped pad 10 further comprises an optical reading / questioning unit 4 which can be connected to an external remote control unit 20.

[0128] The optical reading / questioning unit 4 is optically connected to the optical interface and is configured to receive the aforementioned first photonic signal L1 and second photonic signal L2, and to generate at least one or more electrical signals E1, E2 that represent the first photonic signal L1 and second photonic signal L2 and indicate the detected first strain S1 and second strain S2. The aforementioned one or more electrical signals E1, E2 are configured to be transmitted to the remote control unit 20.

[0129] According to an embodiment of the sensor-equipped pad 10 (for example, shown in Figure 3), the connecting optical interface 3 includes one or more connecting optical fibers 31, each configured to send its respective photoactive radiation OA1, OA2 to the sensor elements 21, 22 and to send its respective optical reflection spectra that form the respective photonic signals between the first photonic signal L1 and / or the second photonic signal L2.

[0130] According to another embodiment of the sensor-equipped pad 10 (for example, shown in Figure 4), one of the connecting optical fibers 31 is further configured to carry the respective photoactive radiation OAT of the temperature sensor 23 (in addition to the photonic signals reflected by the strain sensor FBG contained in the same optical fiber 25, which also includes the temperature sensor 23) and the respective optical reflection spectra that form a third photonic signal LT.

[0131] According to another embodiment of the sensor-equipped pad 10 (shown, for example, in Figure 5), the optional connection interface 3 includes an input connection optical fiber 32 shared by wavelength-multiplexed first OA1 and / or second OA2 photoactive radiation, and an output connection optical fiber 33 shared by the transmitted optical spectrum forming wavelength-multiplexed first photonic signal (L1) and / or second photonic signal (L2), wherein multiple sensor elements are obtained on the same fiber, and the photonic signals emitted by the sensors include the transmitted optical spectrum.

[0132] According to another embodiment of the sensor-equipped pad 10 (for example, shown in Figure 6), if multiple sensor elements are obtained on the same fiber and the photonic signals emitted by the sensors include the transmitted optical spectrum, the optical connection interface 3 includes a connecting optical fiber shared by wavelength-multiplexed first photoactive radiation OA1 and / or second photoactive radiation OA2 and / or third photoactive radiation OAT, and by the reflection spectra that form wavelength-multiplexed first photonic signal L1 and / or second photonic signal L2 and / or third photonic signal LT.

[0133] In another embodiment (not shown in the figure), a third photoactive emission OAT is transmitted to a temperature sensor 5 via a dedicated connecting optical fiber 34, and a third photonic signal LT, including an optical reflection spectrum LT, is transmitted to an optical reading / questioning unit 4 via the same dedicated connecting optical fiber 34.

[0134] According to the embodiment, each connection between the fiber from which the fiber Bragg grating type sensor is obtained and the optical fiber connecting to the optical reading / interrogation unit is made by a removable fiber splice or photonic connection element.

[0135] According to one embodiment (for example, shown in Figures 10 to 13), the sensor-equipped brake pad 10 includes a brake pad base platform (or plate) 11 within the brake pad friction material 12.

[0136] The sensor pad 10 further includes at least one detection element 90, which has a casing including at least one optical fiber strain sensor 2 (fixed by adhesive 7 within a suitable cavity 71) and at least one capillary connection tube 73.

[0137] The casing 9 is made of mineral and / or plastic and / or polymer material and / or resin compound and, unlike the brake pad 10, can be fixed within and / or incorporated into the brake pad 10. The casing 9 is configured to house (and house under operating conditions) at least one optical fiber strain sensor 2, an optical fiber temperature sensor 5, and at least a portion of the connecting optical interface 3.

[0138] At least one capillary connection tube 73 extending from the casing 9 is configured to surround one or more connection fibers of the optical interface 3.

[0139] In this case, the sensor-equipped pad 10 is fixed to the brake pad and connectable to a protective output tube of a connecting optical interface 30 located outside the brake caliper, and further comprises a collector 74 connectable to a reading / questioning unit 4. One capillary connecting tube 73 is wired toward and connected to the collector 74.

[0140] According to one embodiment, the casing 9 is fixed to the sensor pad 10 by adhesive 7, which fixes one or more optical fibers 25, 26, including optical fiber sensors 2, 5, to a predetermined position 71 in the casing 9 configured to route the optical fibers in the correct position. Such a fixing structure 7 is used in two embodiments of the casing 9 (shown in Figures 7A and 8A).

[0141] In a more specific embodiment, the aforementioned casing 9 is made of a mineral and / or plastic and / or polymer material and / or resin compound, and at least one optical fiber strain sensor 2 is embedded therein by being assembled with adhesive or integral molding.

[0142] In such cases, the aforementioned detection element 90 is fixed to and / or incorporated into the brake pad 10 in the friction material 12 of the brake pad at a fixed, predetermined position on the base plate or plate 11 by shape coupling or mechanical coupling between the base plate 11 and the casing 9. This ensures that at least one optical fiber strain sensor 2 is fully incorporated into the desired portion of the friction material M.

[0143] Figures 7A and 8A (and enlarged details in Figures 7B and 8B, respectively) show two embodiments of incorporating the strain sensor 2 within the casing 9 by adhesive 7, and inside the capillary connecting tube 73 inside a specific cavity 71 within the casing 9.

[0144] According to one embodiment, the sensor-equipped pad 10 includes a plurality of detection elements 90. The detection elements are fixed to a portion of the friction material M and include a casing 9, each incorporating at least one optical fiber strain sensor 2, an adhesive 7, and a suitable cavity 71 in the casing 9.

[0145] Figures 11, 12, and 13 show three different embodiments of the sensor-equipped pad 10, each containing one, two, and three detection elements 90, respectively.

[0146] Due to the aforementioned features, the sensor-equipped pad 10 has great flexibility in selecting the position for which the detection elements 90 are placed. In fact, many different embodiments are possible with respect to the number and position of the detection elements 90, including the optical fiber strain sensor 2.

[0147] Next, a brake caliper for a vehicle's disc brake system will be described. Such a brake caliper comprises one or two sensor-equipped brake pads 10 according to any one of the embodiments described above.

[0148] Referring to Figures 1 to 6 and 15-19, a system 100 for detecting and measuring clamping force and / or brake torque resulting from the operation of a vehicle friction brake system by at least one sensor-equipped brake pad 10 of the brake system will be described below by the detection performed.

[0149] Such a system for detecting and measuring braking force and / or braking torque 100 comprises at least one sensor-equipped pad 10 according to any one of the embodiments described above, and further comprises an optical reading / questioning unit 4 and a remote control unit 20.

[0150] The optical reading / questioning unit 4 is optically connected to the optical connection interface 3 of at least one sensor-equipped pad 10 and receives the aforementioned at least one first photonic signal L1 and at least one second photonic signal L2.

[0151] The optical reading / interrogation unit 4 is configured to generate one or more electrical signals E1, E2 representing the first detected strain S1 and the second detected strain S2, based on the first photonic signal L1 and the second photonic signal L2 received as described above.

[0152] A remote control unit 20 located outside the sensor-equipped pad is connected to an optical reading / interrogation unit 4 to receive one or more electrical signals E1, E2, and to process such one or more electrical signals E1, E2 to provide a measurement of clamping force CF and / or brake torque BT.

[0153] According to an embodiment of system 100, the optical reading / interrogation unit 4 is further configured to activate each fiber Bragg grating included in the sensor elements 21, 22, and 23 incorporated into the sensor pad 10 by transmitting a first optical activation radiation OA1 and / or a second photoactivation radiation OA2 and / or a third photoactivation radiation OAT.

[0154] Different embodiments of System 100 are described above in conjunction with the method and correspond to different arrangements of strain sensors (and possible additional temperature sensors) shown in Figures 4 to 6.

[0155] In particular, the embodiment of system 100 (shown in Figures 5 and 6) is noted in which multiple sensor elements 21, 22, and 23 are made from the same optical fiber, and each fiber Bragg grating is associated with its respective different central operating wavelengths λ1, λ2, and λT.

[0156] In this case, the optical reading / interrogation unit element 4 is further configured to transmit its respective photoactive radiation OA1, OA2, and OAT to multiple sensor elements 21, 22, and 23, each centered on their respective operating wavelengths λ1 and λ2, via the connected optical interface 3 using wavelength division multiplexing (WDM) transmission technology.

[0157] Furthermore, the optical reading / questioning unit 4 is configured to receive, via the optical connection interface 3, the respective optical spectra reflected or transmitted by each of the multiplexed sensor elements 21, 22, and 23 by demultiplexing using wavelength division multiplexing (WDM) technology.

[0158] Further details about the optical reading / questioning unit 4 are provided below.

[0159] According to an embodiment of system 100 (shown in Figure 15), the optical reading / interrogation unit 4 comprises a broadband light source 40, an optical circulator 46, and a photoelectron spectrometer receiver 41.

[0160] The broadband light source 40 is configured to transmit the aforementioned first photoactive radiation OA1 and / or the second photoactive radiation OA2 and / or the third photoactive radiation OAT if a temperature sensor is present.

[0161] The emitted light radiation illuminates the optical fiber containing the fiber Bragg grating (FBG) sensor (through the input and through ports of the optical circulator 46), triggering a response from the FBG sensor that generates its respective retroreflective photonic signals (L1, L2, L3). These signals are coupled to the photoelectron receiver to the spectrometer 41 via the output port of the optical circulator 46.

[0162] The photoelectron spectrometer receiver 41 is configured to select a wavelength and / or multiple wavelengths to be received, and is further configured to receive each of the aforementioned at least one first photonic signal L1 and / or at least one second photonic signal L2 and convert them into each of the aforementioned at least one first electrical signal E1 and / or second electrical signal E2, and / or receive the aforementioned third photon signal LT and convert it into the aforementioned third electrical signal ET.

[0163] According to another embodiment of the system 100 (shown in Figure 16), the optical reading / questioning unit 4 comprises an adjustable light source 42, an optical circulator 46, and a photodiode photoelectron receiver 43.

[0164] The adjustable light source 42 is configured to transmit, at a given timing, a desired light emission (OA1 in the example in Figure 13) from among the first photoactive radiation OA1 and / or the second photoactive radiation OA2 and / or the third photoactive radiation OAT described above. Each radiation is at its respective desired wavelength.

[0165] The emitted light radiation illuminates an optical fiber containing a fiber Bragg grating (FBG) sensor (through the input and through ports of the optical circulator 46), determining the response of the wavelength (e.g., λ1) sensitive FBG sensor and generating a retroreflective photonic signal (e.g., L1). This signal is coupled to a photodiode receiver 43 via the output port of the optical circulator 46.

[0166] The photodiode photoelectron receiver 43 is configured to receive the aforementioned retroreflective photonic signals and convert them into corresponding electrical signals. For example, the photodiode photoelectron receiver 43 then receives the aforementioned first photonic signal L1 and converts it into a first electrical signal E1, then receives a second photonic signal L2 and converts it into a second electrical signal E2, then receives a third photonic signal LT and converts it into a third electrical signal ET.

[0167] According to another embodiment of system 100 (shown in Figure 17), the optical reading / questioning unit 4 is entirely constructed from a single photonic integrated circuit using PIC (photonic integrated circuit) technology. In this case, such a single integrated photonic circuit includes a block of broadband light emission source 40, at least one wavelength light filtering element 44, and an optoelectronic photodiode receiver 43.

[0168] The broadband light source 40 is configured to transmit a first photoactive radiation OA1 and / or a second photoactive radiation OA2 and / or a third photoactive radiation OAT.

[0169] The light radiation emitted through the input and through ports of the optical circulator 46 (including light radiation OA1, OA2, and OAT in the example of Figure 17) irradiates the optical fiber containing the FBG sensor. Each sensor reflects its respective photonic signals L1, L2, and LT. The photonic signal WDM, given by the sum of signals L1, L2, and LT, is transmitted to the input of the filter optical element 44 via the output port of the optical circulator 46, each at its own different wavelength.

[0170] The photodiode photoelectron receiver 43 is configured to receive the aforementioned first photonic signal L1 and second photonic signal L2 via a selected optical filtering element 44, and convert them into the first electrical signal E1 or the second electrical signal E2, and / or, if selected, receive the third photon signal LT and convert it into the third electrical signal ET.

[0171] According to a further embodiment of system 100 (for example, shown in Figure 18), the sensor-equipped pad 10 includes a fiber Bragg grating sensor 2 positioned on a birefringent fiber fb. The optical reading / interrogation unit 4 includes an adjustable light source 42, a polarizing beam splitter 45, a first photoelectron photodiode receiver 43a, and a second photoelectron photodiode receiver 43b.

[0172] The adjustable light source 42 is configured to transmit a first photoactive radiation OA1 and / or a second photoactive radiation OA2 and / or a third photoactive radiation OAT at predetermined timings.

[0173] The light radiation emitted from the input and through ports of the optical circulator 46 (including light radiation OA1 in the example of Figure 18) irradiates a birefringent optical fiber containing an FBG sensor. The sensor reflects each photonic signal. The photonic signals reflected or transmitted by the birefringent fiber Bragg grating consist of two components having different first and second birefringent polarizations (in fact, in the example of Figure 18, two photonic signals are obtained - the first two photonic signals L1a, L1b).

[0174] Overall, the photonic signal WDM (shown in Figure 15 as the sum of signals L1a and L1b) is transmitted to the input of the polarizing beam splitter 45 via the output port of the optical circulator 46.

[0175] The polarizing beam splitter 45 receives the aforementioned photonic signal, which is reflected or transmitted by a birefringent fiber Bragg grating and consists of two components having different first and second birefringent polarizations, and generates a first optical beam L1 corresponding to the element having the first polarization and a second optical beam L1b corresponding to the element having the second polarization.

[0176] The first photodiode photoelectron receiver 43a is configured to receive the first light beam L1a and generate a corresponding first electrical signal E1a.

[0177] The second photodiode photoelectron receiver 43b is configured to receive the second light beam L1b and generate the corresponding second electrical signal E1b.

[0178] Regarding the details of receiving and processing photonic signals generated by birefringent optical fiber sensors, known techniques for receiving and processing photonic signals generated by birefringent optical fiber sensors can be used (e.g., Singh P., Julich F., Roths J. "Dependence of strain sensitivity of fiber Bragg gratings imprinted on high birefringent optical fibers" - Optical Sensing and Detection II, 2012 - doi10.1117.922733).

[0179] According to the system embodiment (already described when describing the sensor-equipped pad), the optical reading / questioning unit 4 is integrated and / or housed in the sensor-equipped pad 10. In this case, the electrical signal E is output from the sensor-equipped pad and directed to the remote control unit.

[0180] According to another preferred embodiment of the system (different modifications are shown in Figures 3 to 6), the optical reading / questioning unit 4 is located outside the sensored pad 10. In this case, the photonic signal L is emitted from the sensored pad on the fiber (in the manner already described above) and directed towards the optical reading / questioning unit 4.

[0181] Referring to Figure 19, further embodiments of the system 100 for detecting and measuring clamping force CF and / or brake torque BT are described herein.

[0182] In this case, the system 100 comprises a plurality of sensored pads 101, 102, 103, 104 belonging to one or more brake calipers 200, 300 of the vehicle's brake system, and a single optical reading / questioning unit 4. The reading / questioning unit 4 is operably connected to each of the aforementioned sensored pads 101, 102, 103, 104.

[0183] The optical reading / questioning unit 4 transmits each pair of photoactive radiation (OA11, OA12; OA21, OA22; OA31, OA32; OA41 to OA42) to each of the optical fiber strain sensors on the sensor brake pads 101 to 104, and receives each pair of reflected or transmitted photonic signals (L11, L12; L21, L22; L31, L32; L41, L42) from each of these optical fiber strain sensors according to the selected configuration. The optical reading / questioning unit 4 is also configured to generate a plurality of corresponding electrical signals (E11, E12; E21, E22; E31, E32; E41, E42) based on the photonic signals (L11, L12; L21, L22; L31, L32; L41, L42) received from the plurality of sensor brake pads 101 to 104.

[0184] In the example shown in Figure 19, there are two brake calipers connected to the optical reading / questioning unit 4. In other embodiments, such a number may differ from two (e.g., four).

[0185] Furthermore, in other possible embodiments, each sensored pad includes multiple detection elements, each detection element is illuminated by the optical reading / questioning unit 4, providing its respective pair of photonic signals. In this case, the number of photonic signals received by the optical reading / questioning unit and converted into electrical signals is 2 x N x K, where N is the number of detection elements in each sensored pad and K is the number of sensored pads connected to the optical reading / questioning unit 4.

[0186] Furthermore, in other possible embodiments, the sensor-equipped pad also transmits each third photonic signal LT obtained from the temperature sensor 5 to the optical reading / interrogation unit 4 which generates the respective electrical signals ET.

[0187] In various possible cases, all the aforementioned electrical signals generated by the optical reading / questioning unit are sent to a remote control unit 20, which can determine the clamping force CF and / or brake torque BT based on the multiple electrical signals received.

[0188] According to one embodiment of the system 100, the remote control unit 20 includes at least one processor, which stores one or more software programs and is configured to execute an algorithm configured to calculate a clamping force CF and / or brake torque BT based on a determined first strain S1 and a second strain S2, and / or based on a determined first strain S1, a second strain S2, and temperature.

[0189] In a more specific embodiment, the calculation step includes calculating the clamping force CF and / or brake torque BT by a predefined nonlinear ratio between the clamping force CF and / or brake torque BT and the strain detected by strain sensors FBG located at each position incorporated in the brake pad (as described many times above, the strain is detected by representative values ​​of both the normal force and the tangential component of the force that generates them).

[0190] Such predetermined nonlinear ratios are represented, for example, by a computerized model or lookup table stored in a manner accessible by the processor of the control unit 20.

[0191] The aforementioned predetermined nonlinear ratio is determined, for example, by experiments and / or characterization and / or calibration performed after at least one strain sensor 2 is incorporated into the brake caliper 10 and before the brake caliper 10 is put into use.

[0192] According to the implementation example, the aforementioned steps of testing and / or characterization and / or calibration may include functional and / or structural simulations, such as calculations based on the finite element method (FEM).

[0193] The above calculations and refinements make it possible to define a nonlinear ratio between strain measurements at one or more points on the pad and the clamping force and / or brake torque, and to estimate the clamping force and / or brake torque based on the strain measurements.

[0194] Next, a disc brake system for vehicles included in the present invention will be described.

[0195] According to one embodiment, the brake system includes a brake system with friction brakes, which includes a plurality of brake pads according to one of the embodiments described above.

[0196] According to another embodiment, the brake system includes a brake system with friction brakes and further includes a system 100 for detecting and measuring clamping force and / or brake torque resulting from the embodiment of the brake system according to the above embodiment.

[0197] The object of the present invention is fully achieved by the method, the brake pad with sensor, and the system described above, due to their functional and structural features.

[0198] In fact, the technical solution described here provides one or more photonic sensors that can be easily and effectively integrated and / or fixed and / or incorporated into the brake pads of a friction brake caliper, enabling indirect, accurate, and reliable measurement of the clamping force, which is the result of the torque generated by the brakes acting or the clamping force of the brake caliper on the brake disc.

[0199] The optical fiber sensor consists of several strain sensor elements based on fiber Bragg grating (FBG) technology.

[0200] The sensor element is configured and / or positioned to detect strain at at least two different locations, and to detect each strain that represents both the normal and tangential force components acting at each location.

[0201] Next, the normal and tangential forces acting locally at each detection position are closely related, and therefore accurately represent the forces acting on the brake pads due to the clamping force and brake torque.

[0202] Furthermore, such quantities can be effectively defined by the simultaneous detection of normal and tangential strains at at least two clearly defined locations.

[0203] Advantageously, the technical solution according to the present invention makes it possible to detect and / or determine both clamping force and braking torque (as shown above).

[0204] Advantageously, the FBG technology also provides at least one additional temperature sensor, which allows for more accurate, temperature-compensated estimates.

[0205] Advantageously, in some embodiments, the strain sensor is incorporated into a polymer or mineral material casing that can be fixed and / or integrated into the brake pad at a desired position.

[0206] Advantageously, one or more fibers containing optical fiber sensor elements can be attached to the aforementioned casing in precise orientation by adhesive.

[0207] The aforementioned function ensures the correct position and orientation of the strain sensor at the desired point on the brake pad.

[0208] The aforementioned function ensures the correct position and orientation of the strain sensor at the desired point on the brake pad.

[0209] Advantageously, the possibility of detecting strain at several locations on the brake pads, albeit indirectly, helps to more accurately determine the clamping force and / or brake torque.

[0210] Thanks to the aforementioned features, the sensor-equipped pad offers great flexibility in terms of the number and location of sensors to be placed.

[0211] This system consists of the aforementioned sensor-equipped brake pad. The brake pad includes an optical fiber sensor optically connected to a reading / interrogation unit. The reading / interrogation unit may be separate from the brake pad or integrated with the brake pad, and performs the conversion of strain information between light and electricity based on WDM technology.

[0212] Reading / questioning units can be manufactured based on various electro-optical technologies.

[0213] Advantageously, such reading / querying units can be achieved using silicon-based photonic technology (e.g., PIC: photonic integrated circuit), which also makes it possible to create such units by integrating them into a sensor-equipped brake caliper or electronic control unit.

[0214] Therefore, the system's control unit can determine the clamping force and / or braking torque with great precision over a wide operating range, using temperature compensation.

[0215] Furthermore, advantageously, multiple sensor-equipped pads (each containing two or more sensors) can be connected to a single reading / interrogation unit to provide numerous valuable signals, which, if necessary, allow for precise determination of clamping force and / or brake torque.

[0216] Those skilled in the art can make numerous modifications and adaptations to the embodiments described above, or substitute other functionally equivalent elements to meet incidental needs without departing from the scope of the appended claims. All features described above as belonging to one possible embodiment can be carried out independently of other described embodiments.

Claims

1. A method for detecting and measuring clamping force (CF) and / or brake torque (BT) originating from the operation of a vehicle's friction brake system by detection performed on the brake pads (10) of the brake system, wherein the method is: The step of encapsulating at least one optical fiber strain sensor (2) in a casing (9), and incorporating the casing (9) into a portion of the friction material (M) that adheres to the base platform (11) of the brake pad (10), The aforementioned portion of the friction material (M) is sensitive to friction, and as a result, the tangential strain (St-eff) that the casing (9) receives in the tangential reference direction (x) represents the tangential force (Ft) acting on the brake pad (10), and the normal force (Fn-eff) that the casing (9) receives in the normal reference direction (y) represents the normal force (Fn) acting on the brake pad (10), and The steps include detecting a first strain (S1) that is located at a first position on the casing (9) along a predefined first spatial direction (w1) and acting on the casing (9) by at least one optical fiber strain sensor (2), and which depends on the normal force (Fn-eff) and the tangential strain (St-eff), The steps include detecting a second strain (S2) that is located at a second position on the casing (9) along a predefined second spatial direction (w2) and depends on the normal force (Fn-eff) and the tangential strain (St-eff) acting on the casing (9) using at least one optical fiber strain sensor (2), The steps include generating a first photonic signal (L1) representing the first strain (S1) detected by at least one optical fiber strain sensor (2), and a second photonic signal (L2) representing the second strain (S2) detected by the sensor, The steps include receiving the first photonic signal (L1) and the second photonic signal (L2) by an optical reading / interrogation unit (4) optically connected to at least one optical fiber strain sensor (2), The steps include determining the value of the first strain (S1) and the value of the second strain (S2) by the optical reading / questioning unit (4) based on the first photonic signal (L1) and the second photonic signal (L2), A method comprising the step of determining a measured value of the clamping force (CF) and / or brake torque (BT) based on the value of the first strain (S1) and the value of the second strain (S2).

2. The at least one optical fiber strain sensor (2) is a fiber Bragg grating type sensor, The method according to claim 1, wherein the first spatial direction (w1) and the second spatial direction (w2) are directions different from the tangent reference direction (x) and the normal reference direction (y).

3. The first spatial direction (w1) and the second spatial direction (w2) are symmetric with respect to the normal reference direction (y). Alternatively, the first spatial direction (w1) and the second spatial direction (w2) form complementary angles with respect to the positive tangent reference direction (x), Alternatively, the method according to claim 2, wherein the angle (β) formed by the first spatial direction (w1) and the positive tangent reference direction (x) is equal to the angle (β) formed by the tangent reference direction (x) and the second spatial direction (w2).

4. The at least one optical fiber strain sensor (2) is a fiber Bragg grating type sensor placed on a birefringent fiber, The method according to claim 1, wherein the first spatial direction (w1) coincides with the tangent reference direction (x), and the second spatial direction (w2) is perpendicular to the tangent reference direction (x).

5. The at least one optical fiber strain sensor (2) is A first sensor element (21) includes a first fiber Bragg grating positioned at a first location within a first portion of an optical fiber arranged to align with the first spatial direction (w1), The method according to any one of claims 1 to 4, further comprising a second sensor element (22) including a second fiber Bragg grating positioned at the second location within a second portion of an optical fiber arranged to align with the second spatial direction (w2).

6. The first sensor element (21) and the second sensor element (22) are contained in a single optical fiber (25). or The method according to claim 5, wherein the first sensor element (21) and the second sensor element (22) are contained in two different optical fibers (25, 26).

7. The aforementioned decision-making step is: The optical reading / questioning unit (4) generates a first electrical signal (E1) representing the first photonic signal (L1) and a second electrical signal (E2) representing the second photonic signal (L2). Sending the first electrical signal (E1) and the second electrical signal (E2) to the control unit (20), The method according to claim 5 or 6, comprising calculating the clamping force (CF) and / or brake torque (BT) by a processor of a control unit (20) using one or more algorithms executed by one or more software programs based on the first electrical signal (E1) and the second electrical signal (E2).

8. The method according to claim 7, wherein the calculation step includes calculating a measured value of the brake torque (BT) based on a differential strain (ΔS) given by the difference between a determined value of the first strain (S1) and a determined value of the second strain (S2), using geometric parameters relating to the arrangement of the sensor with respect to the tangential reference direction (x) and the normal reference direction (y), geometric parameters relating to the brake pad and the position of the sensor on the brake pad, and a proportionality constant that depends on a parameter indicating the coefficient of friction of the material from which the casing and the friction material are made.

9. The calculation step includes calculating the clamping force (CF) or normal pressure acting on the brake pad (10) based on the normal force or pressure acting on the portion of the friction material (M) incorporated into the brake pad, The method according to claim 5, wherein the normal pressure acting on the friction material is calculated based on the detected first strain (S1) and / or the detected second strain (S2) using a geometric parameter relating to the arrangement of the first sensor element (21) and the second sensor element (22) in the tangential reference direction (x) and the normal reference direction (y), and a proportionality coefficient that depends on the Young's modulus of the friction material.

10. The steps include encapsulating the optical fiber temperature sensor (5) at a third position near the first and second positions of the casing (9), The steps include: using the optical fiber temperature sensor (5), detecting the temperature present at the third position and generating a third photonic signal (LT) representing the detected temperature; The steps include receiving the third photonic signal (LT) detected by the optical reading / interrogation unit (4) optically connected to the optical fiber temperature sensor (5), The steps include determining a temperature value (T) by the optical reading / interrogation unit (4) based on the received third photonic signal (LT), The step of determining the measured values ​​of the clamping force (CF) and / or brake torque (BT) includes the step of determining the measured values ​​of the clamping force (CF) and / or brake torque (BT) based on the value of the first strain (S1) and the value of the second strain (S2) and the value of the temperature (T) obtained, The optical fiber temperature sensor (5) is a fiber Bragg grating type optical fiber temperature sensor and includes a third sensor element (23). The method according to any one of claims 5 to 9, wherein the third sensor element (23) includes a third fiber Bragg grating obtained at a third position different from the first and second positions in the optical fiber (25, 26) which includes the first fiber Bragg grating and / or the second fiber Bragg grating of the at least one optical fiber strain sensor (2), the method according to any one of claims 5 to 9.

11. The step of determining the measured values ​​of the clamping force (CF) and / or brake torque (BT) is: A step of calculating the strain value due to thermal fluctuations based on the determined temperature value, The steps include: subtracting the strain value due to thermal change from the measured value of the first strain to obtain a first effective strain value that depends solely on mechanical influence; The steps include: subtracting the strain value due to thermal change from the second strain measurement value to obtain a second effective strain value that depends solely on mechanical influences; The method according to claim 10, comprising the step of determining a measured value of the clamping force (CF) and / or brake torque (BT) based on the first effective strain value and the second effective strain value.

12. The at least one optical fiber strain sensor (2) and / or the optical fiber temperature sensor (5) are connected to the optical reading / questioning unit by an optical connection interface (3), The first photonic signal (L1) includes a first optical spectrum reflected or transmitted by the first sensor element (21). The first optical spectrum reaches the optical reading / questioning unit (4) via the optical connection interface (3), and / or The second photonic signal (L2) includes a second optical spectrum reflected or transmitted by the second sensor element (22). The second optical spectrum reaches the optical reading / questioning unit (4) via the optical connection interface (3), and / or The third photonic signal (LT) includes a third optical spectrum reflected or transmitted by the third sensor element (23). The third optical spectrum reaches the optical reading / questioning unit (4) via the optical connection interface (3), The method according to claim 10 or 11, wherein the optical reading / questioning unit (4) is configured to activate each of the first sensor element (21) and / or the second sensor element (22) and / or the third sensor element (23) by transmitting photoactive radiation (OA) or the respective photoactive radiations (OA1, OA2, OAT) via the optical connection interface (3).

13. When the first sensor element (21) and the second sensor element (22) are made on the same fiber, the first fiber Bragg grating and the second fiber Bragg grating are associated with their respective different central operating wavelengths (λ1, λ2). The above method further, The optical reading / interrogation unit element (4) transmits its respective photoactive radiation (OA1, OA2) at its respective central operating wavelength (λ1, λ2) to a plurality of sensor elements (21, 22) via the optical connection interface (3) using long-division multiplexing (WDM) transmission technology. The method according to claim 12, further comprising the step of distinguishing the respective optical spectra reflected or transmitted by each of the plurality of sensor elements (21, 22) by receiving via the optical connection interface (3) and demultiplexing using wavelength division multiplexing (WDM) technology.

14. If the plurality of sensor elements are made on the same fiber and the photonic signals emitted by the sensors include the transmitted optical spectrum, the optical connection interface (3) includes an input connection optical fiber (32) shared to wavelength-multiplexed first photoactive radiation (OA1) and / or second photoactive radiation (OA2) and / or third photoactive radiation (OAT), and an output connection optical fiber (33) shared to wavelength-multiplexed first photonic signal (L1) and / or second photonic signal (L2) and / or third photonic signal (LT), or The method according to claim 13, wherein, if the plurality of sensor elements are made on the same fiber and the photonic signals emitted by the sensors include reflected light spectra, the optical connection interface (3) includes wavelength-multiplexed first photoactive radiation (OA1) and / or second photoactive radiation (OA2) and / or third photoactive radiation (OAT) and the reflected spectra that form the wavelength-multiplexed first photonic signal (L1) and / or second photonic signal (L2) and / or third photonic signal (LT).

15. The casing (9) is Made of polymer or mineral material, unlike the brake pad (10), Having a predetermined shape and dimensions, it can be fixed to and / or incorporated into the brake pad (10). The casing (9) is configured to house at least one optical fiber strain sensor (2), the optical fiber temperature sensor (5), and at least a portion of the optical connection interface (3). The aforementioned encapsulation step is, Embedding at least one optical fiber strain sensor (2) within the casing (9), The method according to claim 13 or 14, comprising incorporating the casing (9) into the brake pad (10) and / or fixing the portion of the friction material (M) to the brake pad (10) at a predetermined position during the manufacture of the brake pad.

16. The step of embedding the at least one optical fiber strain sensor (2) in the casing (9) is: The steps include: incorporating one or more optical fibers (25, 26) including at least one optical fiber strain sensor (2) and the optical fiber temperature sensor (5), and / or one or more connecting fibers (3) of the optical connection interface (3), into a given portion (71) of the casing (9) using adhesive (7) so that the one or more optical fibers (25, 26) are routed to the correct position; The step of using adhesive (7) to incorporate one or more connecting fibers of the optical connection interface (3) into a capillary connecting tube (73) inside the portion (71) of the casing (9), wherein the capillary connecting tube (73) exits the casing (9) and is routed onto the brake pad by a capillary tube or frame structure (75) toward a collector (74), the collector (74) being fixed to the brake pad and connectable to a protective output tube of the optical connection interface (30) which is connectable to the optical reading / interrogation unit element (4) outside the disc brake caliper, The casing (9) and the capillary connecting tube (73), which include the at least one optical fiber strain sensor (2) fixed to the inside of the portion (71) of the casing (9) by adhesive (7), form a detection element (90). The method according to claim 15.

17. The casing (9) is made of a mineral and / or plastic and / or polymer material and / or resin compound. The aforementioned encapsulation step is The steps include: incorporating the at least one optical fiber strain sensor (2) by either assembly using an adhesive or integral molding with the casing (9); The method according to claim 16, comprising the step of fixing and / or incorporating the sensing element (90), including the casing (9), the collector (74), the capillary tube or frame structure (75), to the brake pad (10) and / or incorporating it to the brake pad (10) at a predefined position on the base platform (11) of the brake pad (10) inside the friction material (M) of the brake pad (10) by shape coupling or mechanical coupling between the base platform (11) and the casing (9), so that the at least one optical fiber strain sensor (2) is fully incorporated into a desired portion of the friction material (M).

18. The steps of the method are performed on one of the two brake pads (10) of the disc brake caliper or on both brake pads (10), The method according to claim 16 or 17, wherein the brake pad (10) includes the optical reading / questioning unit (4) associated with and / or coupled to the brake pad (10).

19. The steps of the above method are performed on both of the brake pads (10) of the disc brake caliper, The method according to claim 16, wherein the receiving step and the generating step are performed by a single optical reading / questioning unit (4) which is associated with the disc brake caliper and is operationally connected to both of the brake pads (10) by one optical interface (3) or two different optical interfaces (3).

20. The steps of the above method are performed on both of the brake pads (10) of the multiple disc brake calipers of the vehicle's brake system. The method according to claim 16, wherein the receiving step and the generating step are performed by one or more optical reading / questioning units (4) operably connected to all of the brake pads of the plurality of disc brake calipers of the vehicle's brake system.

21. A step of obtaining real-time dynamic measurements of the clamping force (CF) and / or brake torque (BT) based on the time variation of the measured first strain (S1) and second strain (S2), and / or A step of detecting the possibility of malfunction of at least one optical fiber strain sensor (2) and / or the optical fiber temperature sensor (5), and / or A step of estimating the pad wear level (10) based on detection by at least one optical fiber strain sensor (2) and / or the optical fiber temperature sensor (5), and / or A step of estimating the level of particles released by brake friction based on detection by at least one optical fiber strain sensor (2) and / or the optical fiber temperature sensor (5), and / or During a braking event, the brake pressure is measured based on measurements performed by the optical fiber sensors (21, 22) on both of the brake pads of the disc brake caliper, the effective friction coefficient of the brake is calculated, and the actual clamping force of the disc brake caliper is calculated. Steps to determine the possibility of an imbalance between the brake pressures of the brake pads of one or more disc brake calipers, based on measurements taken by at least one optical fiber strain sensor (2) and / or the optical fiber temperature sensor (5) on the brake pads of one or more disc brake calipers during a braking event, The method according to any one of claims 18 to 20, comprising one or more steps of detecting a malfunction of the brake pads of one or more disc brake calipers based on detections performed by at least one optical fiber strain sensor (2) and / or the optical fiber temperature sensor (5) on one or more pads of one or more disc brake calipers during a braking event.

22. A brake pad (10) with a sensor for a brake caliper of a vehicle friction brake system, wherein the brake pad (10) with a sensor is A brake pad (10) with a sensor, made of a material configured to generate brake friction when brought into contact with a friction brake disc by the brake caliper during a braking event, A casing (9) including at least one optical fiber strain sensor (2) incorporated into a portion of the friction material (M) of the sensor-equipped brake pad (10) that adheres to the base platform (11) of the sensor-equipped brake pad (10), wherein the portion of the friction material (M) is friction-sensitive, and the tangential shear strain (St-eff) experienced by the casing (9) with respect to a reference tangential direction (x) represents a tangential force (Ft) acting on the sensor-equipped brake pad (10), and the normal force (Fn-eff) experienced by the casing (9) with respect to a reference normal direction (y) represents a normal position (Fn) acting on the sensor-equipped brake pad (10), and also represents the clamping force (CF) and / or brake torque (BT) applied to the friction brake disc, wherein the casing (9) includes The at least one optical fiber strain sensor (2) is A first strain (S1) is detected at a first position of the casing (9) along a predefined first spatial direction (w1), and the first strain (S1) depends on both the normal force (Fn-eff) and the tangential force (St-eff) acting on the casing (9). A second strain (S2) is detected at a second position of the casing (9) along a predefined second spatial direction (w2), and the second strain (S2) depends on both the normal force (Fn-eff) and the tangential force (St-eff) acting on the casing (9). A first photonic signal (L1) representing the detected first strain (S1) and a second photonic signal (L2) representing the detected second strain (S2) are generated. The brake pad further includes a sensor-equipped brake pad (10) which is connected to at least one optical fiber strain sensor (2) and an optical connection interface (3) configured to be connected to an optical reading / interrogation unit (4) to transmit the first photonic signal (L1) and the second photonic signal (L2).

23. The at least one optical fiber strain sensor (2) is a fiber Bragg grating type sensor, The sensor-equipped brake pad (10) according to claim 22, wherein the first spatial direction (w1) and the second spatial direction (w2) are different directions from the reference tangential direction (x) and the reference normal direction (y).

24. The first spatial direction (w1) and the second spatial direction (w2) are symmetric with respect to the reference normal direction (y), or The first spatial direction (w1) and the second spatial direction (w2) form a complementary angle with respect to the positive direction of the reference tangent direction (x), or The sensor-equipped brake pad (10) according to claim 23, wherein the angle (β) formed by the positive direction of the reference tangential direction (x) and the first spatial direction (w1) is equal to the angle (β) formed by the negative direction of the reference tangential direction (x) and the second spatial direction (w2).

25. The at least one optical fiber strain sensor (2) is a fiber Bragg grating type sensor placed on a birefringent fiber, The first spatial direction (w1) coincides with the reference tangential direction (x), The second spatial direction (w2) is perpendicular to the reference tangential direction (x). Brake pad with sensor (10) according to claim 22.

26. The at least one optical fiber strain sensor (2) is A first sensor element (21) includes a first fiber Bragg grating positioned at a first location within a first portion of an optical fiber arranged to align with the first spatial direction (w1), A sensor-equipped brake pad (10) according to any one of claims 22 to 25, comprising a second sensor element (22) including a second fiber Bragg grating positioned at the second location within a second portion of an optical fiber arranged to align with the second spatial direction (w2).

27. The first sensor element (21) and the second sensor element (22) are contained in a single optical fiber, or The sensor-equipped brake pad (10) according to claim 26, wherein the first sensor element (21) and the second sensor element (22) are contained in two different optical fibers.

28. A third position near the first and second positions includes an encapsulated optical fiber temperature sensor (5) in the casing (9), The optical fiber temperature sensor (5) is configured to detect the temperature present at the third position and to generate a third photonic signal (LT) representing the detected temperature. The sensor-equipped brake pad (10) according to claim 26 or 27, wherein the optical connection interface (3) is further connected to the optical fiber temperature sensor (5) and connected to the optical reading / questioning unit (4) to transmit the third photonic signal (LT).

29. The optical fiber temperature sensor (5) is a fiber Bragg grating type optical fiber temperature sensor and includes a third sensor element (23) which includes a third fiber Bragg grating obtained from an optical fiber (25) including the first sensor element (21) and the second sensor element (22), or The sensor-equipped brake pad (10) according to claim 28, wherein the optical fiber temperature sensor (5) is a fiber Bragg grating type optical fiber temperature sensor and includes a third sensor element (23) which includes a third fiber Bragg grating made of one of the optical fibers (25, 26) which includes a first strain sensor or a second strain sensor of the fiber Bragg grating type, positioned outside the casing at a third position different from the first or second position, within the friction material or along the stretch of the optical fiber.

30. The sensor-equipped brake pad (10) according to claim 29, wherein the third fiber Bragg grating (23) is inserted into the cavity or capillary tube (71) of the casing (9) and is isolated from thermal expansion and deformation phenomena of the encapsulated material.

31. The optical connection interface (3) One or more connecting optical fibers, each configured to carry photoactive radiation (OA1, OA2, OAT) for sensor elements (21, 22, 23) and to carry reflected light spectra that form the respective first photonic signal (L1) and / or the second photonic signal (L2) and / or the third photonic signal (LT), and / or An input connection optical fiber (32) shared by wavelength-multiplexed first photoactive radiation (OA1) and / or second photoactive radiation (OA2) and / or third photoactive radiation (OAT), and an output connection optical fiber (33) sharing the transmitted optical spectrum constituting the wavelength-multiplexed first photonic signal (L1) and / or second photonic signal (L2) and / or third photonic signal (LT), wherein multiple sensor elements are made in the same fiber, and the photonic signals emitted by the sensors include the transmitted optical spectrum, the input connection optical fiber (32) and the output connection optical fiber (33), and / or A sensor-equipped brake pad (10) according to any one of claims 28 to 30, wherein a connecting optical fiber (35) shared by the wavelength-multiplexed first photoactive radiation (OA1) and / or the second photoactive radiation (OA2) and / or the third photoactive radiation (OAT), and shared by the reflected spectra forming the wavelength-multiplexed first photonic signal (L1) and / or the second photonic signal (L2) and / or the third photonic signal (LT), wherein multiple sensor elements are made in the same fiber, and the photonic signals emitted by the sensors include the reflected light spectra.

32. The base platform (11) of the sensor-equipped brake pad (10) is included within the friction material (M) of the sensor-equipped brake pad (10). Furthermore, it includes at least one detection element (90), The at least one detection element is, A casing (9) made of a polymer or mineral material different from the sensor-equipped brake pad (10), the casing being fixed and / or incorporated within the brake pad, the casing being configured to house at least one optical fiber strain sensor (2) fixed with adhesive (7) within a suitable portion (71) of the casing (9), the optical fiber temperature sensor (5), and at least a portion of the optical connection interface (3), It includes at least one capillary connection tube (73) that extends from the casing (9) and is configured to surround one or more connection fibers of the optical connection interface (3), The sensor-equipped brake pad (10) includes a collector (74) fixed to the brake pad, which can be connected to a protective output tube of the optical connection interface (30) that can be connected to the optical reading / questioning unit (4) outside the brake caliper, The brake pad with sensor (10) according to any one of claims 22 to 30, further comprising a capillary tube or frame structure (75) configured to connect the at least one capillary connecting tube (73) to the collector (74).

33. The casing (9) is made of an organic material and / or a plastic material and / or a polymer material and / or a resin compound, and incorporates the at least one optical fiber strain sensor (2) by adhesive or integral molding. The sensing element (90) is fixed to the base platform (11) of the friction material (M) of the sensor brake pad (10) together with the collector (74) and the frame structure (75) by shape coupling or mechanical coupling (6) between the base platform (11) and the casing (9) and / or incorporated into the sensor brake pad (10), thereby fully incorporating the at least one optical fiber strain sensor (2) at a desired position in the friction material, according to claim 32.

34. It includes multiple detection elements (90), A sensor-equipped brake pad (10) according to any one of claims 22 to 30, 32 to 33, wherein each of the plurality of detection elements includes the casing (9) and the at least one optical fiber strain sensor (2) incorporated within the casing (9).

35. A brake caliper for a vehicle disc brake system, comprising a sensor-equipped brake pad (10) according to any one of claims 32 to 34.

36. A system (100) for detecting and measuring clamping force (CF) and / or brake torque (BT) originating from the operation of the vehicle's friction brake system, by detection performed by a sensor-equipped brake pad (10) of the brake system, A brake pad (10) with at least one sensor according to any one of claims 32 to 34, An optical reading / interrogation unit (4) is optically connected to the optical connection interface (3) of the sensor-equipped brake pad (10) in order to receive a first photonic signal (L1) and a second photonic signal (L2), The optical reading / questioning unit (4) is configured to generate a first electrical signal (E1) and a second electrical signal (E2) representing a first detected strain (S1) and a second detected strain (S2), respectively, based on the received first photonic signal (L1) and second photonic signal (L2). A remote control unit (20) located outside the sensor-equipped pad is connected to the optical reading / questioning unit (4) to receive the first electrical signal (E1) and the second electrical signal (E2), The remote control unit (20) is configured to process the first electrical signal (E1) and the second electrical signal (E2) to obtain and supply measured values ​​of the clamping force (CF) and / or brake torque (BT) of the system (100).

37. The system (100) according to claim 36, wherein the optical reading / questioning unit (4) is configured to activate each fiber Bragg grating included in the sensor elements (21, 22, 23) incorporated into the sensor-equipped brake pad (10) by transmitting a first photoactive emission (OA1) and / or a second photoactive emission (OA2) and / or a third photoactive emission (OAT).

38. When multiple sensor elements (21, 22) are manufactured within the same fiber, each of the fiber Bragg gratings is associated with a different central operating wavelength (λ1, λ2). The optical reading / questioning unit (4) is configured to transmit the photoactive radiation (OA1, OA2) to the plurality of sensor elements (21, 22) via the optical connection interface (3) using wavelength division multiplexing (WDM) transmission technology at their respective central operating wavelengths (λ1, λ2). The system (100) according to claim 37, wherein the optical reading / questioning unit (4) is further configured to receive via the optical connection interface (3) and distinguish each optical spectrum reflected or transmitted by each of the plurality of sensor elements (21, 22) by demultiplexing using wavelength division multiplexing (WDM) technology.

39. The aforementioned optical reading / questioning unit (4) A broadband light source (40) configured to transmit the first photoactive radiation (OA1) and / or the second photoactive radiation (OA2) and / or the third photoactive radiation (OAT) if a temperature sensor is present, The system (100) according to any one of claims 36 to 38, further comprising a photoelectron spectrometer receiver (41) configured to select a wavelength and / or a plurality of wavelengths to be received, and further configured to receive the first photonic signal (L1) and / or the second photonic signal (L2) and convert them to the first electrical signal (E1) and / or the second electrical signal (E2), respectively, and / or receive the third photonic signal (LT) and convert it to the third electrical signal (ET).

40. The aforementioned optical reading / questioning unit (4) A tunable photon emission source (42) configured to transmit the first photoactive emission (OA1) and / or the second photoactive emission (OA2) and / or the third photoactive emission (OAT), A system (100) according to any one of claims 36 to 38, comprising a photodiode photoelectron receiver (43) configured to receive the first photonic signal (L1) and convert it to the first electrical signal (E1), receive the second photonic signal (L2) and convert it to the second electrical signal, and / or receive the third photonic signal (LT) and convert it to the third electrical signal (ET).

41. The aforementioned optical reading / questioning unit (4) is made by a single integrated photonic circuit that implements PIC (photonic integrated circuit) technology. The aforementioned single integrated photonic circuit is A broadband light source (40) configured to transmit the first photoactive radiation (OA1) and / or the second photoactive radiation (OA2) and / or the third photoactive radiation (OAT), To select each photonic signal, at least one optical wavelength filtering element (44) that can be tuned to the wavelength of the queried fiber Bragg grating, A system (100) according to any one of claims 36 to 38, comprising a photodiode photoelectron receiver that receives a photonic signal selected from the first photonic signal (L1) and the second photonic signal (L2), and converts it to the first electrical signal (E1) or the second electrical signal (E2), and / or, if selected, receives the third photonic signal (LT) and converts it to the third electrical signal (ET).

42. The sensor-equipped pad is the sensor-equipped pad according to claim 25, and includes a fiber Bragg grating type sensor (2) arranged on a birefringent fiber (fb), The aforementioned optical reading / questioning unit (4) A tunable photon emission source (42) configured to transmit the first photoactive emission (OA1) and / or the second photoactive emission (OA2) and / or the third photoactive emission (OAT), A polarization beam splitter (45) is configured to receive a photonic signal reflected or transmitted by a birefringent fiber Bragg grating and generate a first light beam (L1a) corresponding to the component with the first polarization and a second light beam (L1b) corresponding to the component with the second polarization, comprising two components having different first and second birefringent polarizations, A first photodiode photoelectron receiver (43a) is configured to receive a first photodiode (L1a) and generate a corresponding first electrical signal (E1a), A system (100) according to any one of claims 36 to 38, comprising a second photodiode photoelectron receiver (43b) configured to receive a second light beam (L1b) and generate a corresponding second electrical signal (E1b).

43. The system according to any one of claims 36 to 42, wherein the optical reading / questioning unit (4) is integrated and / or housed in a sensor-equipped pad (10).

44. A system (100) according to any one of claims 36 to 43, comprising a plurality of sensored pads (101, 102, 103, 104) belonging to one or more brake calipers (200, 300), and a single optical reading / questioning unit (4) operably connected to each of the plurality of sensored pads.

45. The system (100) according to any one of claims 36 to 44, wherein the remote control unit (20) includes at least one processor storing one or more software programs configured to execute an algorithm adapted to calculate a clamping force (CF) and / or brake torque (BT) based on the determined first strain (S1) and second strain (S2), and / or based on the determined first strain (S1), second strain (S2) and temperature.

46. A plurality of brake pads as described in claim 35, and / or A disc brake system for a vehicle, comprising a system (100) for detecting and measuring the braking force and / or braking torque resulting from the operation of the brake system according to claim 36.

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