Method and apparatus for estimating vehicle speed

Abstract

1. A method for estimating the speed of a wheeled vehicle equipped with at least one brake (1) comprising at least one braking element (3, 3') and a braked element (2), the braking element (3, 3') comprising at least one force sensor (6), the method comprising the steps of: - 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'); - calculating a vehicle speed estimate (vest) in which the calculated value of the parameter is input into an estimation algorithm (Ap) for estimating the speed of the vehicle.

Description

[Technical Field]

[0001] The following invention relates to an apparatus and method for estimating the speed of a wheeled vehicle. Summary of the Invention

[0002] As is well known, road vehicles are generally equipped with sensors for detecting various parameters relating to their condition, including their speed.

[0003] Among the most widely used speed sensors, tachometers or phonic wheels can detect the angular velocity of a vehicle wheel, which can be converted into the linear velocity of the vehicle's travel once the shape of the vehicle wheel, in particular the radius, is known.

[0004] It is an object of the present invention to provide an additional method for real-time estimation of vehicle speed, which can be implemented in addition to or instead of existing methods.

[0005] Within this technical problem, one object of the present invention is to provide a real-time estimation of the speed of a vehicle by enhancing the capabilities of the technology already installed in the vehicle.Finally, it is an object of the present invention to devise an apparatus and a method that allow the estimation of the speed of a vehicle using means that are compatible with the on-board equipment and application.

[0006] Finally, it is an object of the present invention to devise an apparatus and method for estimating the speed of a vehicle by means compatible with on-board equipment and applications connected to remotely located recording and processing means.

[0007] This object and these and other objects are achieved by a method for estimating the speed of a wheeled vehicle equipped with at least one brake comprising at least one braking element and a braked element, the braking element comprising at least one force sensor, the method comprising: - performing an acquisition of a force signal generated by said at least one force sensor; - analyzing the force signal in the time domain or the frequency domain and calculating at least one parameter of said force signal; - calculating a vehicle speed estimate, in which the calculated value of said parameter is input into an estimation algorithm for estimating the speed of the vehicle.

[0008] In a mode of the present embodiment, the brakes have an applied state, an inapplied state, and a temporary state between the applied and inapplied states, and vice versa, and the calculation of the speed estimate is only enabled or verified when the brakes are not in the temporary state.

[0009] In a preferred embodiment of the present invention, in the analysis in the time domain, the parameter of the force signal comprises the time distance between peaks of the force signal, and in the analysis in the frequency domain, the parameter of the force signal comprises the first harmonic or fundamental frequency of the frequency spectrum of the force signal.

[0010] In a preferred embodiment of the present invention, the velocity estimation algorithm provides an analytical function that inversely links the parameters of the force signal to the estimated values ​​in the analysis in the time domain and that directly links the parameters of the force signal to the estimated values ​​in the analysis in the frequency domain.

[0011] The present invention relates to a brake system comprising at least one brake with a braked element and at least one braking element with at least one force sensor, -Means for monitoring the brake application / de-application status; an electronic controller of the brake connected to said at least one force sensor, said electronic controller of the brakes having at least one sliding memory buffer and a calculation algorithm for a vehicle speed estimate; - acquiring on a sliding memory buffer the force signals generated by said at least one force sensor during an applied or a non-applied state of the brake; - analyzing the force signal in the time domain or the frequency domain and calculating at least one parameter of said force signal; - calculating the vehicle speed estimate, in which the calculated values ​​of the parameters are input to the speed estimation algorithm.

[0012] The invention arises from the intuition that useful information for estimating vehicle speed can in principle be obtained by analyzing signals generated during braking or outside braking by a sensored brake having at least one force sensor.

[0013] This provides that the sensor brakes have micro-surface and / or geometric irregularities, which are very common in both new and off-the-shelf brakes.

[0014] Speed ​​estimation requires that outside the brake there is residual torque on the braked element with the vehicle moving, and inside the brake there is contact between the braking element and the braked element with the vehicle moving. [Brief explanation of the drawings]

[0015] 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.

[0016] Various features of different disclosed embodiments may be combined to form additional embodiments that are part of this disclosure. [Figure 1] 1 shows a schematic representation of a corner of a vehicle suitably configured to estimate vehicle speed; [Figure 2] 1 shows the architecture of a device for estimating vehicle speed according to a first embodiment of the present invention; [Figure 3] 4 shows the architecture of a device for estimating vehicle speed according to a second embodiment of the present invention; [Figure 4] 4 shows the architecture of a device for estimating vehicle speed according to a third embodiment of the present invention; [Figure 5] 1 shows the time course of the force signal in the outer field of the brake, the inner field of the brake, and the transition field between the outer field of the brake and the inner field of the brake. [Figure 6] 1 shows a computational model for velocity estimation by force signal analysis in the time domain. [Figure 7] 1 presents a computational model for velocity estimation using force signal analysis in the frequency domain. [Figure 8] 1 shows the agreement of the estimates obtained by the method according to the invention compared with direct measurements of the velocity obtained with a velocity sensor. [Figure 9] 1 shows a plan view of a brake pad with a sensor on which the method of the present invention can be implemented; DETAILED DESCRIPTION OF THE INVENTION

[0017] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof.

[0018] In the drawings, like reference numerals generally identify like elements, unless the context requires otherwise.

[0019] The illustrative embodiments described in the detailed description and drawings are not meant to be limiting.

[0020] Typically, components associated with only one corner of the vehicle are shown.

[0021] Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here.

[0022] The aspects of the present disclosure as generally described herein and illustrated in the Figures may be arranged, substituted, combined and designed in a wide variety of different configurations, all of which are expressly contemplated and form part of this disclosure. In accordance with the present invention, as shown schematically in Figure 1, a corner of a vehicle is suitably equipped with a brake 1 comprising a braked element 2 and at least one braking element 3, 3', in particular two braking elements 3, 3'.

[0023] 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.

[0024] Between the rear support plate 5 and the friction material block 4, a cushioning layer 7 may be provided.

[0025] The brake 1 may be of the drum or pad type.

[0026] In the following description, 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.

[0027] 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.

[0028] 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.

[0029] 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 .

[0030] Advantageously, the braking element 3 , 3 ′ can also include at least one temperature sensor 9 connected to the electric circuit 8 .

[0031] The temperature sensor 9 is preferably configured and positioned to acquire the temperature of the rear support plate 5 .

[0032] 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.

[0033] 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 present in the vehicle.

[0034] 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 .

[0035] The sensors may include, for example, a vehicle brake on / off 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.

[0036] The method for estimating vehicle speed includes the following steps.

[0037] The electronic control unit 11 of the brake 1 monitors the activated / deactivated state of the brake 1 via special monitoring means.

[0038] 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.

[0039] Instead of checking the actuation / inactivation state of the brakes 1 via the sensor interrogation 13, it is also possible to use a suitable algorithm for estimating the actuation / inactivation state of the brakes 1 as a monitoring means.

[0040] The electronic control unit 11 of the brake 1 temporarily acquires the force signals F, F' generated during the actuated or inactuated state of the brake 1 from the force sensors 6 in each sensored braking element 3, 3' of the brake 1.

[0041] FIG. 5 shows a graph of a typical time course of the raw signal S generated by the force sensor 6, where the time field α is associated with the inactive state of the brake 1, the time field γ is associated with the active state of the brake 1, and the time field β is associated with the temporary state between the inactive and active states of the brake 1, and vice versa.

[0042] The force signals F, F' are defined by the portion of the signal S in the time field γ or in the time field α. The electronic control unit 11 of the brake 1 analyzes the force signals F, F' in the time domain or in the frequency domain and calculates at least one parameter of the force signals F, F'.

[0043] The electronic control unit 11 finally calculates an estimate of the vehicle speed v est and to do this, the calculated value of at least one parameter is provided as input to a velocity estimation algorithm Ap.

[0044] The nature of the parameters used depends on the type of analysis performed on the force signals F, F', whether in the time domain or the frequency domain.

[0045] FIG. 6 shows an example of an analysis performed in the time domain.

[0046] The raw signals of the forces F, F' are subjected to a pre-processing stage 101, ie, subjected to a pseudo-integration over time, without dispersing their information content, in order to reduce data distortion due to the impulsive nature of the data.

[0047] The time course of the force signals F, F' preprocessed in this way is shown by the graph in FIG. 6 below the box which diagrams the preprocessing stage 101.

[0048] At this point, the pre-processed force signals F, F' are acquired by a sliding memory buffer 21 provided in the electronic control unit 11.

[0049] The width of the sliding memory buffer 21 is preferably 0.2 s to 1 s.

[0050] 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'.

[0051] More precisely, the temporal distance between successive homologous peaks, ie peaks of essentially equal intensity, is calculated.

[0052] Next, the temporal distance d between successive homologous peaks of low intensity is calculated as shown in the graph of FIG. 6 under the box diagramming algorithm 102. timemin and the time distance d between successive homologous peaks of high intensity timemax Both are calculated.

[0053] The two parameters thus calculated are given as input to the speed estimation algorithm Ap.

[0054] The speed estimation algorithm Ap is timemin and d timemax The values ​​of T are compared and the larger value is eval Select .

[0055] At this point, the algorithm calculates the estimate v using the following formula: est can be calculated. v est =2πR eff / T eval In the formula, R eff is the effective radius of the vehicle wheels.

[0056] Estimated vehicle speed v est The frequency of the calculation of may be set equal to the inverse of the width of the sliding memory buffer 21.

[0057] FIG. 7 shows an example of an analysis performed in the frequency domain.

[0058] The raw force signals F, F', possibly pre-processed as described above, are acquired by a sliding memory buffer 21 provided in the electronic control unit 11.

[0059] The width of the sliding memory buffer 21 is preferably 0.2 s to 1 s.

[0060] The acquired force signals F, F′ are windowed by a windowing stage 103 .

[0061] The windowing step 103 may use, for example, a Gaussian window function or a Hamming or other type of window function.

[0062] In the analysis step 104, the frequency spectrum of the windowed generated periodic force signals F, F' is calculated.

[0063] This can be done by applying a known integral transform, such as, but not necessarily, the Fast Fourier Transform (FTT), to the windowed periodic force signal.

[0064] In the analysis stage 104, the amplitudes and frequencies of the harmonics contained in the force signal transform are calculated, the frequency f0 associated with the continuous component of the force signal transform is removed to remove DC noise sources, and the frequency f1 of the dominant harmonic of the force signal transform is identified using known peak detection techniques.

[0065] Estimated vehicle speed v est The algorithm Ap for calculating v est The frequency f1 of this dominant harmonic is used as a parameter for calculating

[0066] The algorithm Ap calculates the estimated value v using the following formula: est can be calculated. v est =2πf1R eff In the formula, R eff is the effective radius of the vehicle wheels.

[0067] Referring to all the above applications, if the braking elements 3, 3' have several force sensors 6, the electronic control unit 11 of the brake 1 obtains the force signal F, F' as an average of the signals from the force sensors 6.

[0068] The method for estimating vehicle speed can be further improved.

[0069] To do this, the electronic control unit 11 of the brake 1 inputs the calculated values ​​of the parameters into a calculation algorithm Ap together with the obtained measured values ​​and / or obtained estimated values ​​of physical parameters representative of the state of the brake 1 and / or the vehicle.

[0070] The value and / or estimate of the at least one physical parameter is preferably obtained during the acquisition of the force signals F, F'.

[0071] Where applicable, the obtained measurements and / or the obtained estimates of physical parameters representative of the state of the brake and / or vehicle are also used in the calculation of the force signal parameters F, F'.

[0072] In the basic architecture of the vehicle speed estimation device shown in Figure 2, the electronic control unit 11 of the brake 1 for all sensored brake elements 3, 3', which are also equipped with temperature sensors 9, also obtains the temperatures measured by the temperature sensors 9 and supplies them to a calculation algorithm Ap using the temperature signals T, T' detected by the temperature sensors 9 and the force signals detected by the force sensors 6.

[0073] In the architecture of the vehicle speed estimator shown in Figures 3 and 4, the electronic control unit 11 of the brake 1 for all sensored brake elements 3, 3', which are also equipped with a temperature sensor 9, obtains the temperatures measured by the temperature sensor 9 and supplies them to a calculation algorithm Ap using 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.

[0074] 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 algorithm Ap.

[0075] Advantageously, in accordance with the present invention, the speed of the vehicle 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.

[0076] Advantageously, the present invention allows for real-time estimation of the vehicle's speed.

[0077] 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.

[0078] According to the invention, the speed of the vehicle is estimated using direct measurements of the forces recorded by the braking elements 3, 3'.

[0079] Vehicle speed 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.

[0080] If the braking element comprises both at least one shear force sensor and at least one normal force sensor, the estimation of vehicle speed may require measuring only the shear force sensor signal, only the normal force sensor signal, or both.

[0081] Figure 8 shows the estimated speed v est and the actual speed v measured, for example, by a vehicle speedometer. The horizontal axis shows time in seconds, and the vertical axis shows v and v in revolutions per minute (rpm). est is shown.

[0082] Of course, modifications and variations of the method and apparatus for estimating vehicle speed beyond those described are possible.

[0083] The method for estimating vehicle speed thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept as defined in the claims.

[0084] Moreover, all the details may be substituted with other technically equivalent elements.

[0085] 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 the speed of a wheeled vehicle comprising at least one brake (1) comprising at least one braking element (3, 3') and a braked element (2), said braking element (3, 3') comprising at least one force sensor (6), said method comprising: - performing an acquisition of the force signals (F, F') generated by said at least one force sensor (6); - analyzing said force signals (F, F') in the time domain or in the frequency domain and calculating at least one parameter of said force signals (F, F'); a step (v) of calculating a vehicle speed estimate in which the calculated values ​​of said parameters are input to an estimation algorithm (Ap) for estimating the speed of said vehicle; ｅｓｔ ) and

2. 2. A method for estimating the speed of a vehicle according to claim 1, characterized in that the brake (1) can be in an activated state, an inactivated state or a temporary state from the activated state to the inactivated state and vice versa, and the method comprises monitoring the state of the brake (1) and validating or verifying the calculation of the speed estimate when the brake (1) is not in the temporary state.

3. 3. The method for estimating the speed of a vehicle according to claim 1 or 2, characterized in that in the analysis in the time domain, the parameters of the force signal (F, F') comprise the time distance between peaks of the force signal, and in the analysis in the frequency domain, the parameters of the force signal (F, F') comprise the first harmonic or fundamental frequency of the frequency spectrum of the force signal (F, F').

4. 4. A method for estimating the speed of a vehicle according to any one of claims 1 to 3, characterized in that the speed estimation algorithm (Ap) provides an analytical function that in the analysis in the time domain links the parameters of the force signals (F, F') to the estimated values ​​in an inversely proportional relationship and that in the analysis in the frequency domain links the parameters of the force signals (F, F') to the estimated values ​​in a directly proportional relationship.

5. 5. The method for estimating the speed of a vehicle according to any one of claims 1 to 4, characterized in that the braking element (3, 3') comprises a plurality of force sensors (6), and the force signal (F, F') is obtained as an average of the force signals (F, F') generated by the plurality of force sensors (6).

6. Method for estimating the speed of a vehicle according to any one of claims 1 to 5, characterized in that the force signals (F, F') are obtained by means of a sliding buffer memory (21).

7. The vehicle speed estimate (v ｅｓｔ 7. A method for estimating the speed of a vehicle according to claim 1, wherein the frequency of calculation of (i) is proportional to the inverse of the size of the sliding memory buffer (21).

8. Method for estimating the speed of a vehicle according to any one of claims 1 to 7, characterized in that the size of the sliding memory buffer (21) is between 0.2s and 1s.

9. 9. A method for estimating the speed of a vehicle according to any one of claims 1 to 8, characterized in that the calculated parameters of the force signals (F, F') are input to the speed estimation algorithm (Ap) together with obtained measurements and / or obtained estimates of physical parameters representative of the state of the brake and / or the vehicle.

10. 10. A method for estimating the speed of a vehicle according to any one of claims 1 to 9, characterized in that for the calculation of the parameters of the force signal (F, F') the obtained measured values ​​and / or obtained estimated values ​​of physical parameters representative of the state of the brake and / or the vehicle are used.

11. 11. A method for estimating the speed of a vehicle according to claim 9 or 10, 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.

12. Method for estimating the speed of a vehicle according to claims 9 to 11, characterized in that the value and / or estimate of at least one physical parameter is obtained during the acquisition of the force signals (F, F').

13. 13. A method for estimating the speed of a vehicle according to any one of claims 1 to 12, 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.

14. A device for estimating the speed of a vehicle equipped with at least one brake (1) including a braked element (2) and at least one braking element (3, 3') equipped with at least one force sensor (6), comprising: - 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 (21) and a vehicle speed estimate (v ｅｓｔ ) and a calculation algorithm (Ap) for - acquiring on said sliding memory buffer (21) the force signals (F, F') generated by said at least one force sensor (6) during an applied or inactivated state of said brake (1); - analyzing said force signals (F, F') in the time domain or in the frequency domain and calculating at least one parameter of said force signals (F, F'); the calculated values ​​of the parameters are input to the speed estimation algorithm (Ap), ｅｓｔ and an electronic controller (11) configured to perform the steps of:

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