WO2024141266A1

WO2024141266A1 - Method and device for estimating the residual torque between at least one braking element and one braked element of a vehicle brake

Info

Publication number: WO2024141266A1
Application number: PCT/EP2023/085582
Authority: WO
Inventors: Pietro Macchi; Stefano Serra; Umberto VIGNOLO
Original assignee: Itt Italia S.R.L.
Priority date: 2022-12-30
Filing date: 2023-12-13
Publication date: 2024-07-04
Also published as: IT202200027324A1

Abstract

The method for estimating the residual torque between at least one braking element (3, 3') and a braked element (2) of a brake (1) of a vehicle, in which the braking element (3, 3 ') includes at least one force sensor (6), comprises the steps of: - monitoring the activated/deactivated status of the brake (1); - temporal acquisition of a force signal generated by the force sensor (6); - calculation of the variation field (Cv, C'v) of the force signal; - calculation of a primary indicator (Ip) of residual torque in which the calculated value of said variation field (Cv, C'v) of the force signal is inputted into a primary calculation algorithm (Ap); wherein the primary indicator of residual torque (Ip) is calculated and the calculated value of said primary indicator of residual torque (Ip) is validated only if the temporal acquisition of the force signal occurred when the brake was in deactivated status.

Description

METHOD AND DEVICE FOR ESTIMATING THE RESIDUAL TORQUE BETWEEN AT LEAST ONE BRAKING ELEMENT AND ONE BRAKED ELEMENT OF A VEHICLE BRAKE

DESCRIPTION

The following invention relates to a device and method for estimating the residual braking torque in a vehicle.

SUMMARY

As is well known, residual braking torque is the very low braking torque found in a vehicle as a result of unintentional interaction between the brake pad and disc when the vehicle itself is not braking.

This condition, which is actually very common, is due to abnormal operation of the brake caliper, which maintains residual contact between the disc and pad after braking.

The persistence of this contact condition, although small, maintains an almost constant residual braking torque, which in the long term has a considerable influence on fuel consumption and brake pad wear.

The new EU6715/2007/EC standard on CO2 sets significantly stricter limits for emissions, forcing vehicle manufacturers not to neglect innovative solutions to reduce them.

In this scenario, the control of any possible loss of performance in the braking system and the ability to limit and prevent an increase in residual braking torque becomes increasingly important in order to contain consumption and thus the resulting emissions of a vehicle.

To date, few systems are available to measure residual braking torque.

This type of measurement can usually be carried out on a laboratory dynamometer, which is normally used to test and evaluate the residual braking torque during the development of a brake system.

Equivalent on-board systems for motor vehicles are shown in WO2018019438A1 owned by this applicant.

For heavy vehicle applications, commercial sensors are available to measure the caliper clearance. These sensors, however, can only measure the total clearance of the entire caliper, i.e. the sum of the clearance of the two brake pads, and their distance from the disc.

Such known sensors, only available for truck applications, cannot distinguish between the two brake pads, only measure geometric distances and do not perform a real measurement of residual drag.

The task proposed by the present invention is to overcome the above-mentioned limitations of the known technique.

As part of this task, it is an aim of the invention to devise a device and a method for estimating the residual braking torque in a vehicle due to the unwanted interaction between the brake pad and the disc at each brake pad.

It is still the aim of the invention to devise a device and method that allows real-time estimation of residual braking torque.

It is still the aim of the invention to devise a device and method to estimate the residual braking torque, which allows the detection of the minimum clearance between the brake pads and the disc for a reduction in brake delay.

Last but not least, the aim of the invention is to devise a device and method that allow an estimate of residual braking torque, with means compatible with on-board installations and applications.

Last but not least, the aim of the invention is to devise a device and method for estimating residual braking torque, with means compatible with on-board installations and applications connected to remotely located recording and processing means.

This task as well as these and other purposes are achieved by a method for estimating the residual torque between at least one braking element and a braked element of a brake of a vehicle, in which the braking element includes at least one force sensor, characterized in that it comprises the steps of:

- monitoring the activated/deactivated status of the brake;

- temporal acquisition of a force signal generated by said at least one force sensor;

- calculation of the variation field of the force signal;

- calculation of a primary indicator of residual torque in which the calculated value of said variation field of the force signal is inputted into a primary calculation algorithm; wherein the primary indicator of residual torque is calculated and the calculated value of said primary indicator of residual torque is validated only if the temporal acquisition of the force signal occurred when the brake was in deactivated status.

The present invention also discloses a device for estimating the residual torque of a brake of a vehicle comprising:

- a braked element;

- at least one braking element provided with at least one force sensor;

- means for monitoring the activated/deactivated status of the brake; and

- an electronic controller of the brake connected to said at least one force sensor; wherein said electronic controller of the brake has at least one sliding memory buffer and a primary calculation algorithm of a primary indicator of residual torque and is configured to perform the following operations:

- acquisition on the sliding memory buffer of a force signal generated by said at least one force sensor

- calculation of the variation field of the acquired force signal;

- calculation of said primary indicator of residual torque by inputting the calculated value of said variation field of the force signal into said primary calculation algorithm; and said electronic controller of the brake being configured to calculate said primary indicator of residual torque and to validate the calculated value of said primary indicator of residual torque only if the acquisition on the sliding memory buffer of the force signal occurred when the brake was in deactivated status.

BRIEF DESCRIPTION OF THE DRAWINGS

Various forms of implementation are depicted in the attached drawings for illustrative purposes and should in no way be construed as limiting the scope of this illustration.

Various characteristics of different disclosed forms of realisation can be combined to form additional forms of realisation, which are part of this illustration.

Figure 1 shows schematically a comer of a vehicle properly configured to estimate residual torque in accordance with a first embodiment of the invention;

Figure 2 shows an architecture of a device for estimating the residual torque, in accordance with a first embodiment of the invention;

Figure 3 shows with a block diagram the estimation method that can be performed with the device in figure 2;

Figure 4 shows an architecture of a device for estimating residual torque, in accordance with a second embodiment of the invention;

Figure 5 shows an architecture of a device for estimating the residual torque, in accordance with a third embodiment of the invention;

Figure 6 shows with a block diagram the estimation method that can be performed with the devices in figures 4 and 5;

Figure 7 shows a plan layout of a possible way of realising a sensorised brake pad that can be used for residual torque estimation, where the block of wear material and the possible shock-absorbing sub-layer have been removed for clarity; Figure 8 shows an experimental calibration curve associating the secondary dimensionless residual torque indicator Is with a dimensional residual torque indicator Ic, obtained through dynamometer tests for two different ranges of residual torque values;

Figure 9 shows the congruence 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 WO2018019438 by the same applicant;

Figure 10 shows the congruence between 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 WO2018019438 by the same applicant, and with an external residual torque sensor.

DETAILED DESCRIPTION OF SOME FORMS OF REALISATION

In the following detailed description, reference is made to the attached drawings, which form a part of this description.

In drawings, similar reference numbers typically identify similar components, unless the context dictates otherwise.

The preferred forms of execution described in the detailed description and drawings are not intended to be limiting.

Typically, components relating to only one comer of the vehicle are illustrated, the characteristics of which are intended to extend to all comers.

Other forms of realisation can be used and other modifications can be made without departing from the spirit or scope of the topic presented here.

The aspects of this illustration, as described in a general manner herein and illustrated in the figures, can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are explicitly contemplated and present in this illustration. According to the present invention, as illustrated schematically in Figure 1, the comer of the vehicle is duly equipped with a brake 1 comprising a braked element 2 and at least one braking element 3, 3', particularly two braking elements 3, 3'.

Each braking element 3, 3' includes a wearable block of friction material 4 and a rear support plate 5, typically metal, between which is interposed at least one force sensor 6, e.g. of the piezoceramic type.

A cushioning layer 7 can be provided between the rear support plate 5 and the friction material block 4.

Brake 1 can be of the drum or pad type.

In the case illustrated below, we will refer to a pad brake 1 in which the braked element 2 is a disc and the two braking elements 3, 3' are operational on opposite sides of the disc and consist of a right-hand and a left-hand pad of which at least one is sensed with at least one force sensor.

In the case of a drum brake, there will be a drum as the braked element and two brake shoes as the braking elements, at least one of which will be sensorised with at least one force sensor.

Preferably the braking element 3, 3' includes more than one force sensor 6, in particular at least one normal force sensor and/or at least one shear force sensor.

The force sensors 6 are connected to an electrically isolated circuit 8 located on the side of the rear support plate 5 facing the friction material block 4.

The braking element 3, 3' advantageously can also include at least one temperature sensor 9 connected to the electrical circuit 8.

Temperature sensor 9 is configured and positioned to preferably acquire the temperature of the rear support plate 5 .

The electrical circuit 8 has an electrical interface connector 10 for the transmission of electrical signals generated by sensors 6, 9 to an electronic control unit 11 of brake 1, and electrical tracks 10' connecting sensors 6, 9 to electrical connector 10. As we shall see, the electronic control unit 11 of brake 1 can interact with the electronic control unit 12 with which the vehicle is normally equipped.

Furthermore, as we shall see, the electronic control unit 11 of brake 1 can interact with other sensors installed in the vehicle directly or via the vehicle's electronic control unit 12.

Said sensors may include, for example, a vehicle brake activation/deactivation status sensor 13, a vehicle speed sensor 14, a vehicle acceleration sensor 15, a temperature sensor 16 of the environment outside the vehicle, a temperature sensor 17 of the braked element 2, and a vehicle wheel speed and/or angular acceleration sensor 18.

The method for estimating the residual torque between each sensed brake element 3, 3' and braked element 2 of a brake 1 at a vehicle comer comprises the following steps.

The electronic brake control unit 11 monitors the activated/deactivated status of brake 1 via special monitoring means.

This monitoring can be carried out by the electronic control unit 11 of brake 1 via a direct connection to brake activation/deactivation status sensor 13 or via a connection to the vehicle's electronic control unit 12, which in turn is connected to brake activation/deactivation status sensor 13.

As an alternative to checking the brake 1 activation/deactivation status via sensor 13 interrogation, it is also possible to use suitable algorithms for estimating the brake 1 activation/deactivation status as a means of monitoring.

The electronic control unit 11 of the brake 1 temporally acquires the force signal F, F' generated by the force sensors 6 in each sensorised braking element 3, 3'.

The electronic control unit 11 of brake 1 calculates, for each braking element 3, 3' sensed, the variation field Cv , C'v of the force signal F, F'.

Before calculating the variation, the force signal must be appropriately filtered.

In particular, a low-pass filter can be used for this purpose. For example, but not necessarily, a third-order low-pass filter with a cutoff frequency of 35 HZ can be used.

In the case where the braking element 3, 3' has several force sensors 6, the electronic control unit 11 of the brake 1 obtains the force signal 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 on the force signal F, F' thus obtained calculates the variation field Cv and respectively C'v.

The average of the force signals is calculated by a computational node M, M' of the electronic control unit 11 of brake 1.

The calculation of the variation field Cv, C'v advantageously is performed using sliding memory buffers, with which the electronic control unit 11 of brake 1 is equipped.

At this point, the electronic control unit 11 of brake 1 calculates a primary indicator Ip of residual torque; to do this, the calculated value of the variation field Cv of the force signal F, and the value of the variation field C'v of the force signal F', are given as input to a special primary calculation algorithm Ap.

Obviously if only one braking element 3, 3' is sensed, only the value of the variation field Cv, C'v of the force signal F, F' associated with it is given as input to the primary calculation algorithm Ap.

Electronic control unit 11 of brake 1 calculates the primary residual torque indicator Ip and validates the calculated value of the primary residual torque indicator Ip only if the time acquisition of the force signal F, F' occurred during a deactivated status of brake 1.

Electronic control unit 11 of brake 1 in fact, as specified above, is able to monitor the activated/deactivated status of brake 1.

The method for estimating residual torque further involves a step of calculating a secondary indicator Is of residual torque. To do this, the electronic control unit 11 of brake 1 inputs the calculated value of the primary indicator Ip of residual torque to a secondary calculation algorithm As, together with acquired measurement values and/or acquired estimates of physical parameters representative of the status of brake 1 and/or the vehicle.

The values and/or estimates of at least one physical parameter are preferably acquired during the acquisition of the force signal F, F'.

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

In the methodological approach illustrated in figure 3, referring to the basic architecture of the residual torque estimation device illustrated in figure 2, the electronic control unit 11 of the brake

I for all sensorised braking elements 3, 3' also equipped with a temperature sensor 9 also acquires the temperature measured by the temperature sensor 9 and uses the temperature signal T, T' detected by the temperature sensor 9 and the force signals Fa, Fb, Fc, Fd, F'a, F'b, F'c, F'd detected by the force sensors 6 to feed the secondary algorithm As for calculation.

In the methodological approach illustrated in Figure 6, referring to the more complex architecture of the residual torque estimation device illustrated in Figures 4 and 5 , the electronic control unit

I I of the brake 1 for all sensing braking elements 3, 3' also equipped with a temperature sensor 9 acquires the temperature measured by the temperature sensor 9 and uses the temperature signal T, T' detected by the temperature sensor 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 feed the secondary algorithm As for calculation.

If necessary, the wear degree estimated by a special algorithm or measured from material block 4 can also be used to feed the secondary As calculation algorithm. Advantageously, according to the present invention, residual torque can be estimated by a single supervisory and control electronic processing unit (ECU) or by individual electronic processing units (ECUs) 11 dedicated to each comer of the vehicle.

Advantageously, according to the present invention, the residual torque can be estimated in real time.

All acquisition and processing algorithms are independent of the type of vehicle and/or brake pad and/or driving style, thanks to a self-assessment of the calibration of the signal threshold: advantageously, no tuning operations are therefore required for different applications.

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

Residual torque estimation can be used for pure monitoring, e.g. for the vehicle information and entertainment system 19, but also in closed-loop feedback applications, e.g. applications 20 BBW (Brake By Wire) for electric brakes and EMB ( Electro Magnetic Brake or Electro Mechanic Brake) for electromagnetic or electromechanical brakes.

The signal acquisition strategy is time-based and the sampling frequency Fs is related to the maximum speed to be investigated, e.g. Fs=50Hz for a maximum speed limit of 130 km/h.

Sampling frequency Fs can vary between 40 Hz and 50 Hz, where the minimum sampling frequency Fs of 40 Hz corresponds to a maximum detectable speed of 100 km/h.

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

However, it is possible to calibrate the indicator Is, as can be seen in Figures 3 and 6, to create a dimensional indicator Ic of residual torque by experimentally associating actual values of residual torque with values of the secondary indicator Is.

Calibration C, as can also be seen in figure 8, can be done over different ranges of residual torque values, e.g. a first range between 0 Nm and 15 Nm and a second range between 0 Nm and 50 Nm. Calibration C can be single by using identical Pc calibration parameters for all braking elements 3, 3' or calibration C can be single by using dedicated Pc calibration parameters for each braking element 3, 3'.

In cases where a brake element is equipped with both at least one shear force sensor and at least one normal force sensor, the residual torque estimation may require only the measurement of the shear force sensor signals , only the measurement of the normal force sensor signals or both measurements.

In cases where a braking element is equipped with both at least one shear force sensor and at least one normal force sensor, the vehicle speed or the activated/deactivated status of the brake pedal can be estimated for the purpose of calculating the secondary indicator Is by using either only the measurement of the shear force sensor signals, only the measurement of the normal force sensor signals or both measurements.

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

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

In addition, all details can be replaced with other technically equivalent elements.

In practice, the materials used, as well as the systems, can be of any type according to requirements and the state of the art.

Claims

1. A method for estimating the residual torque between at least one braking element (3, 3’) and a braked element (2) of a brake (1) of a vehicle, in which the braking element (3, 3’) includes at least one force sensor (6), characterized in that it comprises the steps of:

- monitoring the activated/deactivated status of the brake (1);

- temporal acquisition of a force signal generated by said at least one force sensor (6);

- calculation of the variation field (Cv, C’v) of the force signal;

- calculation of a primary indicator (Ip) of residual torque in which the calculated value of said variation field (Cv, C’v) of the force signal is inputted into a primary calculation algorithm (Ap); wherein the primary indicator of residual torque (Ip) is calculated and the calculated value of said primary indicator of residual torque (Ip) is validated only if the temporal acquisition of the force signal occurred when the brake was in deactivated status.

2. The method for estimating the residual torque according to the preceding claim, characterized in that the braking element (3, 3’) includes a plurality of force sensors (6), and in that said force signal is acquired as the average of the force signals generated by said plurality of force sensors (6).

3. The method for estimating the residual torque according to any preceding claim, characterized in that said force signal of said at least one force sensor (6) is acquired with a sliding memory buffer.

4. The method for estimating the residual torque according to any preceding claim, characterized by further providing for a step of calculating a secondary indicator of residual torque (Is) in which the calculated value of said primary indicator of residual torque (Ip) is inputted into a secondary calculation algorithm (As), together with acquired measurement values and/or acquired estimates of physical parameters representing the status of the brake and/or of the vehicle.

5. The method for estimating the residual torque according to the preceding claim, characterized by acquiring values and/or estimates of at least one physical parameter chosen between brake temperature, brake wear, speed/acceleration of the vehicle, angular speed/acceleration of the wheel of the vehicle, ambient temperature.

6. The method for estimating the residual torque according to any one of claims 4 and 5, characterized in that said values and/or estimates of at least one physical parameter are acquired during the acquisition of said force signal.

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

8. The method for estimating the residual torque according to any preceding claim, characterized in that said value of said primary indicator of residual torque (Ip) is calculated by inputting into said primary calculation algorithm (Ap) the calculated value of the variation field (Cv, C’v) of the force signal generated by said at least one force sensor (6) of said two braking elements (3, 3’).

9. A device for estimating the residual torque of a brake (1) of a vehicle comprising:

- a braked element (2);

- at least one braking element (3, 3’) provided with at least one force sensor (6);

- means for monitoring the activated/deactivated status of the brake (1); and

- an electronic controller (11) of the brake (1) connected to said at least one force sensor (6); wherein said electronic controller (11) of the brake (1) has at least one sliding memory buffer and a primary calculation algorithm (Ap) of a primary indicator of residual torque (Ip) and is configured to perform the following operations:

- acquisition on the sliding memory buffer of a force signal generated by said at least one force sensor (6);

- calculation of the variation field (Cv, C’v) of the acquired force signal;

- calculation of said primary indicator of residual torque (Ip) by inputting the calculated value of said variation field (Cv, C’v) of the force signal into said primary calculation algorithm (Ap); and said electronic controller (11) of the brake (1) being configured to calculate said primary indicator of residual torque (Ip) and to validate the calculated value of said primary indicator of residual torque (Ip) only if the acquisition on the sliding memory buffer of the force signal occurred when the brake was in deactivated status.

10. The device for estimating the residual torque of a brake according to the preceding claim, characterized in that it includes means for measuring and/or estimating physical parameters representing the status of the brake and/or of the vehicle, and in that said electronic controller (11) of the brake (1) has a secondary calculation algorithm (As) of a secondary indicator of residual torque (Is) and is configured to calculate the value of said secondary indicator of residual torque (Is) by inputting into said secondary calculation algorithm (As) said calculated value of said primary indicator (Ip) together with acquired measurement values and/or acquired estimates of physical parameters representing the status of the brake and/or of the vehicle.