Method and device for estimating residual torque between at least one braking element and one braked element of a vehicle brake

Abstract

1. A method for estimating a residual torque between at least one braking element (3, 3') of a brake (1) of a vehicle and a braked element (2), the braking element (3, 3') comprising at least one force sensor (6), the method comprising the steps of: monitoring the actuated / deactuated state of the brake (1); - temporary acquisition of force signals generated by the force sensor (6); - calculating a fluctuation field (Cv, C'v) of the force signals; - calculating a primary indicator of the residual torque (Ip), wherein the calculated value of said fluctuation field of the force signals (Cv, C'v) is input into a primary calculation algorithm (Ap), wherein the primary indicator of the residual torque (Ip) is calculated and the calculated value of said primary indicator of the residual torque (Ip) is verified only if the temporary acquisition of force signals was performed when the brake was in a deactuated state.

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for estimating residual brake torque in a vehicle. Summary of the Invention

[0002] As is known, residual braking torque is a very limited amount of braking torque present in a vehicle, which is the result of inadvertent interactions that occur between the brake pads and discs when the vehicle is not braking.

[0003] This condition, which is very common in practice, is due to the abnormal operation of the brake caliper, which maintains residual contact between the disc and the pads after braking.

[0004] This persistence of contact maintains a small but nearly constant residual brake torque, which over the long term has a significant impact on fuel consumption and brake pad wear.

[0005] The new EU 6715 / 2007 / EC standard on CO2 sets significantly stricter limits on emissions and forces vehicle manufacturers to be vigilant in finding innovative solutions to reduce emissions.

[0006] In this case, control of possible performance losses in the braking system and the ability to limit and prevent the increase of residual braking torque becomes increasingly important in order to limit consumption and therefore the resulting emissions of the vehicle.

[0007] To date, there are few systems available for measuring residual brake torque.

[0008] This type of measurement can typically be performed on a laboratory dynamometer, which is typically used to test and evaluate residual brake torque during the development of a braking system.

[0009] An equivalent in-vehicle system for automobiles is shown in commonly owned WO 2018019438(A1).

[0010] For heavy vehicle applications, commercially available sensors are available to measure caliper clearance, however, these sensors can only measure the total clearance across the caliper, i.e., the sum of the clearances of the two brake pads and the distance of the brake pads from the disc.

[0011] Such known sensors, which are only available for truck applications, are unable to distinguish between the two brake pads and only measure the geometric distance, without performing an actual measurement of the residual drag.

[0012] The problem proposed by the present invention is to overcome the above-mentioned limitations of the known technology.

[0013] As part of this task, it is an object of the present invention to devise an apparatus and method for estimating, at each brake pad, the residual braking torque of a vehicle due to undesired interactions between the brake pad and the disc.

[0014] It is a further object of the present invention to devise an apparatus and method that allows real-time estimation of residual brake torque.

[0015] A further object of the present invention is to devise a device and method for estimating residual brake torque that makes it possible to detect the minimum clearance between the brake pads and the disc in order to reduce braking delay.

[0016] Finally, the object of the invention is to devise a device and a method that allow the estimation of the residual brake torque using means that are compatible with on-board equipment and applications.

[0017] Finally, it is an object of the present invention to devise an apparatus and method for estimating residual brake torque using means compatible with on-board installations and applications connected to remotely located recording and processing means.

[0018] This object and these and other objects are achieved by a method for estimating a residual torque between at least one braking element and a braked element of a brake of a vehicle, the braking element including at least one force sensor, the method comprising: - monitoring the brake activation / deactivation state; - performing a temporary acquisition of the force signal generated by said at least one force sensor; - calculating a fluctuation field of the force signal; - calculating a primary indicator of the residual torque, in which the calculated values ​​of said fluctuation field of force signals are input into a primary calculation algorithm, This is achieved by a method in which a primary indicator of residual torque is calculated, and the calculated value of said primary indicator of residual torque is verified only if a temporary acquisition of the force signal is performed when the brake is in a non-actuated state.

[0019] The present invention also provides an apparatus for estimating a residual torque of a brake of a vehicle, the apparatus comprising: a braked element; at least one braking element equipped with at least one force sensor; -Means for monitoring the brake application / de-application status; an electronic controller for the brake connected to the at least one force sensor, said electronic controller of the brake having at least one sliding memory buffer and a primary calculation algorithm of a primary indicator of residual torque; - acquiring on a sliding memory buffer the force signals generated by said at least one force sensor; - calculating the fluctuation field of the acquired force signals; - calculating said primary indicator of residual torque by inputting the calculated values ​​of said fluctuation field of force signals into said primary calculation algorithm, and an electronic controller of the brake configured to calculate the primary indicator of residual torque and to verify the calculated value of the primary indicator of residual torque only if acquisition of a force signal on a sliding memory buffer occurred when the brake was in a deactivated state. [Brief explanation of the drawings]

[0020] Various implementations are illustrated in the accompanying drawings for illustrative purposes and should not be construed as limiting the scope of the present disclosure in any way. Various features of different disclosed embodiments may be combined to form additional embodiments that are part of this disclosure. [Figure 1] 2 shows a schematic representation of a corner of a vehicle suitably configured to estimate residual torque according to a first embodiment of the present invention; [Figure 2] 1 shows the architecture of a device for estimating residual torque according to a first embodiment of the invention; [Figure 3] 3 shows a block diagram of an estimation method that can be implemented in the device of FIG. 2. [Figure 4] 4 shows the architecture of a device for estimating residual torque according to a second embodiment of the invention; [Figure 5] 4 shows the architecture of a device for estimating residual torque according to a third embodiment of the present invention; [Figure 6] A block diagram shows an estimation method that can be implemented in the devices of FIGS. [Figure 7] 1 shows a planar layout of a possible way to realize a brake pad with a sensor that can be used for residual torque estimation, with blocks of wear material and a possible shock absorbing sub-layer removed for clarity. [Figure 8]1 shows an experimental calibration curve relating the quadratic non-dimensional residual torque indicator Is to the dimensional residual torque indicator Ic obtained through dynamometer testing for two different ranges of residual torque values. [Figure 9] We demonstrate the agreement of experimental results obtained with the time-based estimation method and subject matter of the present invention with another frequency-based estimation method and subject matter of patent application WO 2018019438 by the same applicant. [Figure 10] We show agreement between the time-based estimation method and subject matter of the present invention, another frequency-based estimation method and subject matter of patent application WO2018019438 by the same applicant, and experimental results obtained using an external residual torque sensor. DETAILED DESCRIPTION OF THE INVENTION

[0021] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof.

[0022] In the drawings, like reference numerals generally identify like elements, unless the context requires otherwise.

[0023] The illustrative embodiments described in the detailed description and drawings are not meant to be limiting.

[0024] Typically, components are shown that relate to only one corner of the vehicle, but the characteristics are intended to extend to all corners.

[0025] Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here.

[0026] The aspects of the present disclosure, as generally described herein and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are expressly contemplated and make part of this disclosure.

[0027] According to the invention, as shown diagrammatically in FIG. 1, the corners of the vehicle are suitably equipped with brakes 1 comprising a braked element 2 and at least one braking element 3, 3', in particular two braking elements 3, 3'.

[0028] Each braking element 3, 3' comprises a wearable block 4 of friction material and a rear support plate 5, typically metallic, between which is interposed at least one force sensor 6, for example of the piezoceramic type.

[0029] Between the rear support plate 5 and the friction material block 4, a cushioning layer 7 may be provided.

[0030] The brake 1 may be of the drum or pad type.

[0031] In the cases described below, reference is made to a pad brake 1 in which the braked element 2 is a disc and two braking elements 3, 3' are operable on either side of the disc, consisting of a right-hand pad and a left-hand pad, at least one of which is sensed by at least one force sensor.

[0032] In the case of a drum brake, there is a drum as the braked element and two brake shoes as the braking elements, at least one of the brake shoes being sensed by at least one force sensor.

[0033] Preferably, the braking element 3, 3' comprises two or more force sensors 6, in particular at least one normal force sensor and / or at least one shear force sensor.

[0034] The force sensor 6 is connected to an electrically isolated circuit 8 located on the side of the rear support plate 5 facing the friction material block 4 .

[0035] Advantageously, the braking element 3 , 3 ′ can also include at least one temperature sensor 9 connected to the electric circuit 8 .

[0036] The temperature sensor 9 is preferably configured and positioned to acquire the temperature of the rear support plate 5 .

[0037] The electrical circuit 8 comprises an electrical interface connector 10 for transmitting the electrical signals generated by the sensors 6, 9 to an electronic control unit 11 of the brake 1, and electrical tracks 10' connecting the sensors 6, 9 to the electrical connector 10.

[0038] As will be explained below, the electronic control unit 11 of the brake 1 is able to interact with an electronic control unit 12 normally provided in the vehicle.

[0039] Furthermore, as will be explained below, the electronic control unit 11 of the brake 1 can interact with other sensors installed in the vehicle, either directly or via the vehicle's electronic control unit 12 .

[0040] The sensors may include, for example, a vehicle brake application / non-application status sensor 13, a vehicle speed sensor 14, a vehicle acceleration sensor 15, a temperature sensor 16 for the environment outside the vehicle, a temperature sensor 17 for the braked element 2, and a vehicle wheel speed and / or angular acceleration sensor 18.

[0041] The method for estimating the residual torque between each sensed braking element 3, 3' and the braked element 2 of the brake 1 at a corner of the vehicle comprises the following steps:

[0042] The electronic brake control unit 11 monitors the activated / deactivated state of the brake 1 via special monitoring means.

[0043] This monitoring can be performed by the electronic control unit 11 of the brake 1 via a direct connection to the brake application / deactivation state sensor 13 or via a connection to the vehicle's electronic control unit 12 which is connected to the brake application / deactivation state sensor 13.

[0044] Instead of checking the actuation / inactivation state of the brake 1 via interrogation of the sensor 13, it is also possible to use a suitable algorithm for estimating the actuation / inactivation state of the brake 1 as a monitoring means.

[0045] The electronic control unit 11 of the brake 1 temporarily acquires the force signals F, F' generated by the force sensors 6 of each sensored braking element 3, 3'.

[0046] The electronic control unit 11 of the brake 1 calculates for each sensed brake element 3, 3' a variation field Cv, C'v of the force signals F, F'.

[0047] Before the changes can be calculated, the force signal must be appropriately filtered.

[0048] In particular, a low-pass filter can be used for this purpose.

[0049] For example, but not necessarily, a third order low pass filter with a cutoff frequency of 35 Hz can be used.

[0050] If the braking elements 3, 3' have several force sensors 6, the electronic control unit 11 of the brake 1 obtains the force signals F, F' as the average of the signals Fa, Fb, Fc, Fd and respectively F'a, F'b, F'c, F'd from the different force sensors 6 and calculates the fluctuation fields Cv and C'v respectively based on the force signals F, F' thus obtained.

[0051] The mean values ​​of the force signals are calculated by the calculation nodes M, M′ of the electronic control unit 11 of the brake 1 .

[0052] The calculation of the fluctuation fields Cv, C'v is advantageously carried out using a sliding memory buffer provided in the electronic control unit 11 of the brake 1.

[0053] At this point, the electronic control unit 11 of the brake 1 calculates a primary indicator Ip of the residual torque, and to do this, the calculated values ​​of the fluctuation field Cv of the force signal F and the values ​​of the fluctuation field C'v of the force signal F' are given as inputs to a special primary calculation algorithm Ap.

[0054] Obviously, if only one braking element 3, 3' is sensed, only the values ​​of the variation field Cv, C'v of the force signal F, F' associated therewith are given as input to the primary calculation algorithm Ap.

[0055] The electronic control unit 11 of the brake 1 calculates the primary residual torque indicator Ip and verifies the calculated value of the primary residual torque indicator Ip only if the time acquisition of the force signals F, F' has taken place during the inactive state of the brake 1.

[0056] The electronic control unit 11 of the brake 1 is in fact able to monitor the actuation / inactuation state of the brake 1 as described above.

[0057] The method for estimating the residual torque further comprises the step of calculating a secondary indicator of the residual torque Is.

[0058] To do this, the electronic control unit 11 of the brake 1 inputs the calculated value of the primary indicator Ip of the residual torque into a secondary calculation algorithm As together with the obtained measurements and / or obtained estimates of physical parameters representative of the state of the brake 1 and / or the vehicle.

[0059] The value and / or estimate of the at least one physical parameter is preferably obtained during the acquisition of the force signals F, F'.

[0060] These values ​​and / or estimates of the at least one physical parameter are used to offset the primary indicator of residual torque Ip.

[0061] In the methodological approach shown in Figure 3, with reference to the basic architecture of the residual torque estimation device shown in Figure 2, the electronic control unit 11 of the brake 1 for all sensored brake elements 3, 3' that are also equipped with temperature sensors 9 also obtains the temperatures measured by the temperature sensors 9 and uses the temperature signals T, T' detected by the temperature sensors 9 and the force signals Fa, Fb, Fc, Fd, F'a, F'b, F'c, F'd detected by the force sensors 6 to provide a secondary algorithm As for calculation.

[0062] In the methodological approach shown in Figure 6, with reference to the more complex architecture of the residual torque estimation device shown in Figures 4 and 5, the electronic control unit 11 of the brake 1 for all sensitive brake elements 3, 3' which are also equipped with temperature sensors 9, obtains the temperatures measured by the temperature sensors 9 and uses the temperature signals T, T' detected by the temperature sensors 9, the force signals Fa, Fb, Fc, Fd, F'a, F'b, F'c, F'd detected by the force sensors 6 and the signals detected by one or more of the sensors 13, 14, 15, 16, 17, 18 to provide a secondary algorithm As for calculation.

[0063] If necessary, the degree of wear estimated by a special algorithm or measured from the material block 4 can also be used to feed the secondary As calculation algorithm.

[0064] Advantageously, according to the present invention, the residual torque can be estimated by a single supervisory control electronic processing unit (ECU) or by individual electronic processing units (ECUs) 11 dedicated to each corner of the vehicle.

[0065] Advantageously, the present invention allows for a real-time estimation of the residual torque.

[0066] All acquisition and processing algorithms are independent of vehicle type and / or brake pads and / or driving style thanks to the self-evaluation of the calibration of signal thresholds, and therefore advantageously no adjustment operations are required for different applications.

[0067] According to the invention, the residual torque is estimated using direct measurements of the forces recorded by the braking elements 3, 3'.

[0068] Residual torque estimation can be used for pure monitoring, e.g. for vehicle information and entertainment systems 19, but also in closed-loop feedback applications, e.g. applications 20BBW (Brake-by-Wire) for electric braking and EMB (Electromagnetic or Electromechanical Braking) for electromagnetic or electromechanical braking.

[0069] The signal acquisition strategy is time-based, with a sampling frequency Fs related to the maximum speed being investigated, for example Fs=50 Hz for a maximum speed limit of 130 km / h.

[0070] The sampling frequency Fs can vary between 40 Hz and 50 Hz, with a minimum sampling frequency Fs of 40 Hz corresponding to a maximum detectable speed of 100 km / h.

[0071] Estimating the residual torque results in a dimensionless primary indicator Ip and a secondary indicator Is.

[0072] However, as can be seen in Figures 3 and 6, it is possible to calibrate the indicator Is and experimentally relate the actual value of the residual torque to the value of the secondary indicator Is, thereby creating a dimensional indicator Ic of the residual torque.

[0073] As can also be seen in FIG. 8, calibration C can be performed over different ranges of residual torque values, for example a first range of 0 Nm to 15 Nm and a second range of 0 Nm to 50 Nm.

[0074] The calibration C may be single by using the same Pc calibration parameters for all brake elements 3, 3', or the calibration C may be single by using dedicated Pc calibration parameters for each brake element 3, 3'.

[0075] If the braking element comprises both at least one shear force sensor and at least one normal force sensor, the residual torque estimation may require measuring only the shear force sensor signal, only the normal force sensor signal, or both.

[0076] If the braking element is equipped with both at least one shear force sensor and at least one normal force sensor, the vehicle speed or the actuated / inactuated state of the brake pedal can be estimated for the purpose of calculating the secondary indicator Is by using only the measurements of the shear force sensor signal, only the measurements of the normal force sensor signal, or both measurements.

[0077] Modifications and variations to the method and apparatus for estimating the residual torque of an element of a vehicle brake beyond those described are of course possible.

[0078] The method for estimating the residual torque of an element of a vehicle brake designed in this way is subject to numerous modifications and variations, all of which fall within the scope of the inventive concept as defined in the claims.

[0079] Moreover, all the details may be substituted with other technically equivalent elements.

[0080] In fact, the materials and systems used can be of any type according to the needs and the state of the art.

Claims

1. A method for estimating a residual torque between at least one braking element (3, 3') of a brake (1) of a vehicle and a braked element (2), said braking element (3, 3') comprising at least one force sensor (6), said method comprising the steps of: - monitoring the activation / deactivation state of said brake (1); - temporary acquisition of the force signal generated by said at least one force sensor (6); - calculating the fluctuation field (Cv, C'v) of the force signals; - calculating a primary indicator of residual torque (Ip) in which the calculated values ​​of said fluctuation field (Cv, C'v) of said force signals are input to a primary calculation algorithm (Ap), a primary indicator of residual torque (Ip) is calculated and the calculated value of the primary indicator of residual torque (Ip) is verified only if the temporary acquisition of the force signal occurred when the brake was in an inactive state.

2. 2. The method for estimating residual torque according to claim 1, characterized in that the braking element (3, 3') comprises a plurality of force sensors (6), and the force signal is obtained as an average of the force signals generated by the plurality of force sensors (6).

3. 3. A method for estimating residual torque according to claim 1 or 2, characterized in that the force signals of the at least one force sensor (6) are acquired by means of a sliding memory buffer.

4. 4. A method for estimating residual torque according to any one of claims 1 to 3, further comprising the step of calculating a secondary indicator of residual torque (Is), wherein the calculated value of the primary indicator of residual torque (Ip) is input to a secondary calculation algorithm (As) together with the obtained measurements and / or estimated values ​​of physical parameters representative of the state of the brake and / or the vehicle.

5. 5. A method for estimating residual torque according to any one of claims 1 to 4, characterized in that values ​​and / or estimates of at least one physical parameter selected from among brake temperature, brake wear, speed / acceleration of the vehicle, angular speed / acceleration of the wheels of the vehicle, ambient temperature are obtained.

6. Method for estimating residual torque according to claim 4 or 5, characterized in that the value and / or estimate of at least one physical parameter is obtained during acquisition of the force signal.

7. 7. A method for estimating residual torque according to any one of claims 1 to 6, characterized in that the brake (1) comprises two brake elements, each of which is formed by an abradable block (4) of friction material and a rear support plate (5) between which the at least force sensor (6) is interposed.

8. 8. A method for estimating residual torque according to any one of claims 1 to 7, characterized in that the value of the primary indicator (Ip) of residual torque is calculated by inputting calculated values ​​of the fluctuation fields (Cv, C'v) of force signals generated by the at least one force sensor (6) of the two braking elements (3, 3') into the primary calculation algorithm (Ap).

9. A device for estimating residual torque of a brake (1) of a vehicle, comprising: - the braked element (2), at least one braking element (3, 3') equipped with at least one force sensor (6), - means for monitoring the activation / deactivation state of said brake (1); an electronic controller (11) of the brake (1) connected to the at least one force sensor (6), the electronic controller (11) of the brake (1) comprising at least one sliding memory buffer and a primary calculation algorithm (Ap) of a primary indicator of the residual torque (Ip); - acquiring on said sliding memory buffer the force signals generated by said at least one force sensor (6); - calculating the fluctuation field (Cv, C'v) of the acquired force signals; - calculating a primary indicator (Ip) of the residual torque by inputting the calculated values ​​of the fluctuation field (Cv, C'v) of the force signals into the primary calculation algorithm (Ap), and an electronic controller (11) of the brake (1) configured to calculate the primary indicator of residual torque (Ip) and to verify the calculated value of the primary indicator of residual torque (Ip) only if the acquisition of the force signal on the sliding memory buffer occurred when the brake was in an inactive state.

10. 10. A device for estimating the residual torque of a brake according to any one of claims 1 to 9, characterized in that it comprises means for measuring and / or estimating physical parameters representative of the state of the brake and / or the vehicle, and the electronic controller (11) of the brake (1) has a secondary calculation algorithm (As) of a secondary indicator of the residual torque (Is) and is configured to calculate the value of the secondary indicator of the residual torque (Is) by inputting the calculated value of the primary indicator (Ip) together with the obtained measured values ​​and / or obtained estimated values ​​of the physical parameters representative of the state of the brake and / or the vehicle into the secondary calculation algorithm (As).

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