Method and apparatus for estimating vehicle speed

Abstract

A method for estimating the speed of a wheeled vehicle provided with at least one brake (1) comprising at least one braking element (3, 3 ') and a braked element (2) wherein the braking element (3, 3') comprises at least one force sensor (6), the method comprising the following steps:-acquiring a force signal (F, F ') generated by the at least one force sensor (6); -analysing the force signal (F, F ') in the time or frequency domain and calculating at least one parameter of the force signal (F, F'); and-calculating a vehicle speed estimate (vest), wherein the calculated value of the parameter is input into an estimation algorithm (Ap) for estimating the speed of the vehicle.

Description

[0001] The present invention relates to a device and a method for estimating the speed of a wheeled vehicle. SUMMARY OF THE INVENTION

[0002] As is well known in the art, road vehicles are generally equipped with sensors for detecting various parameters related to their state, including their speed.

[0003] Among the most widely used speed sensors, a tachometer or a tone wheel can detect the angular velocity of a wheel, and then, once the geometry of the wheel, and in particular its radius, is known, this angular velocity can be converted into the linear speed of the vehicle's forward movement.

[0004] The task of the present invention is to provide an additional method for estimating the vehicle speed in real time, which can be implemented as a supplement or an alternative to existing methods.

[0005] In this technical task, an object of the present invention is to provide a real-time estimate of the vehicle speed by enhancing the functions of the technology already installed in the vehicle. Last but not least, an object of the present invention is to design a device and a method for estimating the vehicle speed that allow for the use of components compatible with on-vehicle installation and applications.

[0006] Last but not least, an object of the present invention is to design a device and a method for estimating the vehicle speed by using components compatible with on-vehicle installation and applications that are connected to a remote-location recording and processing medium.

[0007] This task and these and other objects are achieved by a method for estimating the speed of a wheeled vehicle provided with at least one brake, said at least one brake comprising at least one braking element and a braked element, wherein said braking element comprises at least one force sensor, characterized in that the method comprises the following steps:

[0008] - Acquiring a force signal generated by said at least one force sensor;

[0009] - Analyzing said force signal in the time domain or the frequency domain and calculating at least one parameter of said force signal; and

[0010] - Calculating an estimated value of the vehicle speed, wherein the calculated value of said parameter is input into an estimation algorithm for estimating the speed of the vehicle.

[0011] In an embodiment of the present invention, the brake has an activated state, a deactivated state, and a transition state between the activated state and the deactivated state and between the deactivated state and the activated state, and the calculation of the estimated speed value is enabled or verified only when the brake is not in said transition state.

[0012] In a preferred embodiment of the present invention, in the analysis in the time domain, the parameter of the force signal includes the time distance between the peaks of the force signal, and in the analysis in the frequency domain, the parameter of the force signal includes the first harmonic or fundamental frequency of the spectrum of the force signal.

[0013] In a preferred embodiment of the present invention, the speed estimation algorithm provides an analysis function that is associated with the inverse proportional relationship between the parameter of the force signal and the estimated value in the analysis in the time domain, and is associated with the direct proportional relationship between the parameter of the force signal and the estimated value in the analysis in the frequency domain.

[0014] The present invention also discloses a device for estimating the speed of a vehicle, the vehicle being provided with at least one brake, the at least one brake including a braked element and at least one braking element provided with at least one force sensor;

[0015] Characterized in that the device includes:

[0016] - a component for monitoring the activation / deactivation state of the brake; and

[0017] - an electronic controller of the brake, the electronic controller being connected to the at least one force sensor;

[0018] Wherein the electronic controller of the brake has at least one sliding memory buffer and a calculation algorithm for the vehicle speed estimated value, and is configured to perform the following operations:

[0019] - Acquire the force signal generated by the at least one force sensor during the activation or deactivation state of the brake on the sliding memory buffer;

[0020] - Analyze the force signal in the time domain or frequency domain and calculate at least one parameter of the force signal; and

[0021] - Calculate the vehicle speed estimated value, wherein the calculated value of the parameter is input into the speed estimation algorithm.

[0022] The present invention stems from the following intuition: Useful information for estimating the speed of a vehicle can in principle be obtained by analyzing the signals generated by a sensor-equipped brake having at least one force sensor during non-braking or braking periods.

[0023] This causes the sensor brake to have micro-surfaces and / or geometric irregularities, which, however, are very common in both new and commercial brakes.

[0024] For speed estimation, it is required that outside braking, there is a residual torque on the braked element when the vehicle is in motion, and within braking, there is contact between the braking element and the braked element when the vehicle is in motion. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Various implementations are depicted in the drawings for illustrative purposes and should in no way be construed as limiting the scope of the description.

[0026] Various features of the different disclosed implementations may be combined to form additional implementations that are part of this description.

[0027] Figure 1 schematically illustrates a corner of a vehicle suitably configured to estimate vehicle speed;

[0028] Figure 2 shows the architecture of an apparatus for estimating vehicle speed according to a first embodiment of the present invention;

[0029] Figure 3 shows the architecture of an apparatus for estimating vehicle speed according to a second embodiment of the present invention;

[0030] Figure 4 shows the architecture of an apparatus for estimating vehicle speed according to a third embodiment of the present invention;

[0031] Figure 5 The time course of the force signal in the outer braking field, in the inner braking field and in the transition field between the outer braking field and the inner braking field is shown;

[0032] Figure 6 A computational model for velocity estimation by force signal analysis in the time domain is shown;

[0033] Figure 7 A computational model for velocity estimation using force signal analysis in the frequency domain is shown;

[0034] Figure 8 shows the consistency of the estimate obtained by the method according to the invention compared to a direct measurement of the speed obtained using a speed sensor;

[0035] Figure 9 A plan view of a sensor-mounted brake pad is shown, in which the method of the present invention may be implemented. DETAILED DESCRIPTION

[0036] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof.

[0037] In the drawings, similar symbols typically identify similar components, unless context dictates otherwise.

[0038] The specific embodiments and the preferred forms of implementation described in the drawings are not intended to be limiting.

[0039] Generally, only the components related to one corner of the vehicle are shown.

[0040] Without departing from the essence or scope of the subject matter presented herein, other implementations may be used and other modifications may be made.

[0041] As generally described herein and as shown in the drawings, aspects of the present description can be arranged, replaced, combined, separated, and designed into various different configurations, all of which are clearly contemplated and presented in this description. According to the present invention, as Figure 1 schematically shown, the corner of the vehicle is suitably equipped with a brake 1, which includes a braking element 2 and at least one braking element 3, 3', in particular two braking elements 3, 3'.

[0042] Each braking element 3, 3' includes a wear-resistant friction material block 4 and a rear support plate 5 (usually metal), and at least one force sensor 6 (such as a force sensor of piezoelectric ceramic type) is inserted between them.

[0043] A buffer layer 7 may be provided between the rear support plate 5 and the friction material block 4.

[0044] The brake 1 can be a drum brake or a disc brake.

[0045] In the case shown below, we will refer to the disc brake 1, where the braking element 2 is a disc, and the two braking elements 3, 3' operate on opposite sides of the disc and consist of a right-hand piece and a left-hand piece, and at least one of the right-hand piece and the left-hand piece is sensed by at least one force sensor.

[0046] In the case of a drum brake, there will be a drum as the braking element and two brake shoes as the braking elements, and at least one of the two brake shoes will be sensed by at least one force sensor.

[0047] Preferably, the braking elements 3, 3' include more than one force sensor 6, in particular at least one normal force sensor and / or at least one shear force sensor.

[0048] 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.

[0049] The braking elements 3, 3' may advantageously also include at least one temperature sensor 9 connected to the circuit 8.

[0050] The temperature sensor 9 is configured and positioned to preferably collect the temperature of the rear support plate 5.

[0051] The electrical circuit 8 has 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 .

[0052] As we will see, the electronic control unit 11 of the brake 1 can interact with an electronic control unit 12 with which the vehicle is usually equipped.

[0053] Furthermore, as we will see, the electronic control unit 11 of the brake 1 may interact with other sensors installed in the vehicle, either directly or via an electronic control unit 12 of the vehicle.

[0054] The sensors may include, for example, a vehicle brake on / off state sensor 13 , a vehicle speed sensor 14 , a vehicle acceleration sensor 15 , a vehicle external environment temperature sensor 16 , a braked element 2 temperature sensor 17 , and a wheel speed and / or angular acceleration sensor 18 .

[0055] The method for estimating vehicle speed comprises the following steps.

[0056] The electronic control unit 11 of the brake 1 monitors the activation / deactivation state of the brake 1 via special monitoring components.

[0057] This monitoring may be performed by the electronic control unit 11 of the brake 1 via a direct connection to the brake activation / deactivation status sensor 13 or via a connection to the electronic control unit 12 of the vehicle which in turn is connected to the brake activation / deactivation status sensor 13 .

[0058] As an alternative to checking the activation / deactivation state of the brake 1 via the sensor interrogation 13 , it is also possible to use suitable algorithms for estimating the activation / deactivation state of the brake 1 as a monitoring measure.

[0059] The electronic control unit 11 of the brake 1 detects the force signals F, F′ generated during the activated or deactivated state of the brake 1 from the force sensor 6 in each sensor-equipped brake element 3 , 3 ′ of the brake 1 .

[0060] Figure 5 A diagram showing a typical time course of the raw signal S generated by the force sensor 6 is shown: the time field α is associated with the deactivated state of the brake 1, the time field γ is associated with the activated state of the brake 1, and the time field β is associated with the transition states of the brake 1, said transition states being between the deactivated state and the activated state and between the activated state and the deactivated state.

[0061] The force signals F, F' are defined by parts of the signal S in the time field γ or the time field α. The electronic control unit 11 of the brake 1 analyzes the force signals F, F' in the time domain or the frequency domain and calculates at least one parameter of the force signals F, F'.

[0062] The electronic control unit 11 finally calculates an estimated value v of the vehicle speed est , and for this purpose, it provides the calculated value of at least one parameter as an input to the speed estimation algorithm Ap.

[0063] The nature of the parameter used depends on the type of analysis performed on the force signals F, F', whether in the time domain or in the frequency domain.

[0064] Figure 6 An example of the analysis performed in the time domain is shown.

[0065] The original signals of the forces F, F' undergo a preprocessing stage 101, i.e., they undergo a pseudo-integration over time in order to reduce data distortion caused by the pulsed nature of the data, without, however, dispersing their information content.

[0066] The time course of the force signals F, F' preprocessed in this way is shown by Figure 6 the diagram located below the box 101 schematically showing the preprocessing stage in

[0067] At this time, the preprocessed force signals F, F' are acquired by the sliding memory buffer 21 equipped in the electronic control unit 11.

[0068] The width of the sliding memory buffer 21 is preferably between 0.2 s and 1 s.

[0069] The acquired force signals F, F' are analyzed using a known real-time peak detection algorithm 102. The calculated parameter is the time distance between the peaks of the acquired force signals F, F'.

[0070] More precisely, what is calculated is the time distance between consecutive homologous peaks (i.e., between peaks of substantially equal intensity).

[0071] Then the time distance d between consecutive homologous peaks of low intensity is calculated timemin and the time distance d between consecutive homologous peaks of high intensity timemax both, as shown in the diagram below the box 102 schematically showing the algorithm in Figure 6 The two parameters calculated in this way are provided as inputs to the speed estimation algorithm Ap.

[0072] The speed estimation algorithm Ap compares d

[0073] and d timemin and d timemaxThe larger of these two values is selected. eval .

[0074] At this point, the algorithm can calculate the estimated value v using the following formula est :

[0075] v est ＝ 2πR eff / T eval

[0076] where R eff is the effective radius of the wheel.

[0077] Estimated value of vehicle speed v est The calculation frequency of can be set equal to the inverse of the width of the slide memory buffer 21.

[0078] Figure 7 An example of analysis performed in the frequency domain is shown.

[0079] The raw force signals F, F′ (possibly pre-processed as described above) are acquired by a sliding memory buffer 21 equipped with the electronic control unit 11 .

[0080] The width of the sliding memory buffer 21 is preferably between 0.2 s and 1 s.

[0081] The acquired force signals F, F′ are windowed by a windowing stage 103 .

[0082] At the windowing stage 103, for example, a Gaussian window function or a Hamming or other type of window function may be used.

[0083] In the analysis phase 104 , the frequency spectrum of the windowed and generated periodic force signal F, F′ is calculated.

[0084] This can be accomplished by applying a known integral transform, such as, but not necessarily, a Fast Fourier Transform (FTT), to the windowed and periodic force signal.

[0085] In the analysis stage 104 , the amplitudes and frequencies of the harmonics contained in the force signal transform are calculated, the frequency f 0 associated with the continuous component of the force signal transform is removed to eliminate DC noise sources, and the frequency f 1 of the main harmonic of the force signal transform is identified using known peak detection techniques.

[0086] Used to calculate the estimated value v of the vehicle speed est The algorithm Ap can use the frequency f1 of the main harmonic as the frequency for calculating v est Parameters.

[0087] Algorithm Ap can calculate the estimated v using the following formulaest :

[0088] v est =2πf1 R eff

[0089] where R eff is the effective radius of the wheel.

[0090] With reference to all the applications described above, in case the brake 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 value of the signals from the force sensors 6 .

[0091] The method for estimating vehicle speed can be further improved.

[0092] To this end, the electronic control unit 11 of the brake 1 inputs the calculated values of the parameters to a calculation algorithm Ap together with acquired measured values and / or acquired estimated values of physical parameters representative of the state of the brake 1 and / or the vehicle.

[0093] The value and / or estimated value of the at least one physical parameter is preferably acquired during the acquisition of the force signal F, F′.

[0094] Where applicable, values of acquired measurements and / or acquired estimates of physical parameters representative of the state of the brake and / or vehicle are also used for calculating the force signal parameters F, F'.

[0095] use Figure 2 The basic architecture of the vehicle speed estimation device shown is that for all sensor-equipped brake elements 3, 3' (also equipped with temperature sensors 9), the electronic control unit 11 of the brake 1 also collects the temperature measured by the temperature sensor 9, and uses the temperature signals T, T' detected by the temperature sensor 9 and the force signal detected by the force sensor 6 to feed the calculation algorithm Ap.

[0096] use Figure 3 and Figure 4 In the architecture of the vehicle speed estimation device shown, for all sensor-mounted brake elements 3, 3' (also equipped with a temperature sensor 9), the electronic control unit 11 of the brake 1 collects the temperature measured by the temperature sensor 9, and uses the temperature signals T, T' detected by the temperature sensor 9, the force signal detected by the force sensor 6, and the signals detected by one or more of the sensors 13, 14, 15, 16, 17, 18 to feed the calculation algorithm Ap.

[0097] If necessary, the algorithm Ap can also be fed with the degree of wear estimated by a special algorithm or measured from the material block 4 .

[0098] Advantageously, according to the present invention, the speed of the vehicle can be estimated by a single supervisory and control electronic processing unit (ECU) or by separate electronic processing units (ECUs) 11 dedicated to each corner of the vehicle.

[0099] Advantageously, according to the present invention, the speed of the vehicle can be estimated in real time.

[0100] Due to the self - evaluation of the calibration of the signal thresholds, all acquisition and processing algorithms are independent of the vehicle type and / or brake pads and / or driving style: thus, advantageously, no tuning operations are required for different applications.

[0101] According to the present invention, the direct measurement of the forces recorded by the braking elements 3, 3' is used to estimate the speed of the vehicle.

[0102] The vehicle speed estimation can be used for pure monitoring, for example, for the vehicle infotainment system 19, but can also be used for closed - loop feedback applications, for example, application 20 - for BBW (brake - by - wire) of electric brakes and for EMB (electromagnetic brake or electro - mechanical brake) of electromagnetic or electro - mechanical brakes.

[0103] If the braking elements are equipped with both at least one shear - force sensor and at least one normal - force sensor, the estimation of the vehicle speed may require measuring only the shear - force sensor signal, only the normal - force sensor signal, or both.

[0104] Figure 8 A graph showing the comparison between the estimated speed v est and the speed v actually measured, for example, by a vehicle speedometer. The abscissa represents time in seconds, and the ordinate represents v and v in revolutions per minute (rpm). est .

[0105] Of course, modifications and variations to the methods and devices for estimating the vehicle speed are possible in addition to those described.

[0106] The method for estimating the vehicle speed conceived in this way can be subject to many modifications and variations, all of which fall within the scope of the inventive concept defined by the claims.

[0107] Furthermore, all details can be replaced by other technically equivalent elements.

[0108] In practice, depending on requirements and the state of the art, the materials used as well as the systems can be of any type.

Claims

1. A method for estimating the speed of a wheeled vehicle, said wheeled vehicle being provided with at least one brake (1), said at least one brake comprising at least one braking element (3, 3') and a braked element (2), wherein said braking element (3, 3') comprises at least one force sensor (6), characterized in that, The method comprises the following steps: - Acquiring force signals (F, F') generated by the at least one force sensor (6); - Analyzing the force signals (F, F') in the time domain or the frequency domain and calculating at least one parameter of the force signals (F, F'); and - Calculate the estimated vehicle speed (v est ), where the calculated value of the parameter is input into the estimation algorithm (Ap) for estimating the speed of the vehicle.

2. The method for estimating the vehicle speed according to the preceding claim, wherein the brake can adopt an activated state, a deactivated state, or a transition state from the activated state to the deactivated state and from the deactivated state to the activated state, characterized in that, Monitoring the state of the brake (1), and enabling or validating the calculation of the speed estimate when the brake (1) is not in the transition state.

3. A method for estimating vehicle speed according to any preceding claim, characterized in that In the analysis in the time domain, the parameter of the force signal (F, F') comprises the time distance between the peaks of the force signal, and in the analysis in the frequency domain, the parameter of the force signal (F, F') comprises the first harmonic or fundamental frequency of the spectrum of the force signal (F, F').

4. Method for estimating vehicle speed according to the preceding claim, characterized in that The speed estimation algorithm (Ap) provides an analysis function which is associated with the inverse proportional relationship between the parameter of the force signal (F, F') and the estimate in the analysis in the time domain, and is associated with the direct proportional relationship between the parameter of the force signal (F, F') and the estimate in the analysis in the frequency domain.

5. The method for estimating a vehicle speed according to the previous claim, characterized in that, The braking elements (3, 3') comprise a plurality of force sensors (6), and the force signals (F, F') are acquired as the average value of the force signals (F, F') generated by the plurality of force sensors (6).

6. The method for estimating the vehicle speed according to any one of the preceding claims, characterized in that, The force signals (F, F') are acquired by using a sliding buffer memory (21).

7. The method for estimating a vehicle speed according to the previous claim, characterized in that, The calculation frequency of the estimated vehicle speed value (v est ) is proportional to the reciprocal of the size of the sliding memory buffer (21).

8. The method for estimating the vehicle speed according to the previous claim, characterized in that, The size of the sliding memory buffer (21) ranges between 0.2 s and 1 s.

9. The method for estimating the vehicle speed according to any one of the preceding claims, characterized in that, The calculated parameters of the force signals (F, F') are input into the speed estimation algorithm (Ap) together with the acquired measurement values and / or acquired estimated values of the physical parameters representing the state of the brake and / or the vehicle.

10. The method for estimating the vehicle speed according to the previous claim, characterized in that, To calculate the parameters of the force signals (F, F'), the acquired measurement values and / or acquired estimated values of the physical parameters representing the state of the brake and / or the vehicle are used.

11. The method for estimating the vehicle speed according to any one of claims 9 and 10, characterized in that, Acquiring the value and / or estimated value of at least one physical parameter selected from among brake temperature, brake wear, the speed / acceleration of the vehicle, the angular velocity / acceleration of the wheels of the vehicle, and ambient temperature.

12. The method for estimating the vehicle speed according to any one of claims 9 to 11, characterized in that, Acquiring the value and / or estimated value of at least one physical parameter during the acquisition of the force signals (F, F').

13. The method for estimating the vehicle speed according to any one of the preceding claims, characterized in that, The brake (1) comprises two braking elements, each braking element being formed by a wear-resistant friction material block (4) and a rear support plate (5), and the at least one force sensor (6) is inserted between the wear-resistant friction material block and the rear support plate.

14. A device for estimating the speed of a vehicle, the vehicle being provided with at least one brake (1), the at least one brake comprising a braked element (2) and at least one braking element (3, 3') provided with at least one force sensor (6); It is characterized in that The device comprises: - Components for monitoring the activation / deactivation state of the brake (1); and - The electronic controller (11) of the brake (1), the electronic controller being connected to the at least one force sensor (6); wherein the electronic controller (11) of the brake (1) has at least one sliding memory buffer (21) and a calculation algorithm (Ap) for the estimated vehicle speed (v est ) and is configured to perform the following operations: - Acquire, on the sliding memory buffer (21), the force signals (F, F') generated by the at least one force sensor (6) during the activation or deactivation state of the brake (1); - Analyze the force signals (F, F') in the time domain or the frequency domain and calculate at least one parameter of the force signals (F, F'); and - Calculate the estimated vehicle speed value (v est ), where the calculated value of the parameter is input into the speed estimation algorithm (Ap).

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