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US-12617408-B2 - Motor vehicle and method to detect a parameter associated with a superficial condition of the road surface

US12617408B2US 12617408 B2US12617408 B2US 12617408B2US-12617408-B2

Abstract

A motor vehicle comprising a body defining a passenger compartment, a plurality of wheels; and a sensor designed to detect a parameter associated with a superficial condition of a road surface; the sensor comprises, in turn, an emitter configured to emit a first laser signal towards a road surface; and one or more single-photon avalanche diodes configured to detect a second laser signal corresponding to the reflection of the first laser signal against said road surface.

Inventors

  • Giovanni Sartoni
  • Matteo MONTIROSI
  • Ugo Sitta

Assignees

  • FERRARI S.P.A.

Dates

Publication Date
20260505
Application Date
20231024
Priority Date
20221031

Claims (11)

  1. 1 . A motor vehicle ( 1 ) comprising: a body ( 2 ) defining a passenger compartment ( 3 ); a plurality of wheels ( 4 , 5 ); and a sensor ( 10 ) designed to detect a parameter associated with a superficial condition of a road surface ( 16 ); said sensor ( 10 ) comprising, in turn: an emitter ( 15 ) configured to emit a first laser signal (R) towards the road surface ( 16 ); a plurality of single-photon avalanche diodes (SPADs) ( 11 a , 11 b , 11 c ) configured to detect second laser signals (S, T, U) corresponding, in use, to a reflections of the first laser signal (R) against said road surface ( 16 ), wherein said second laser signals (S, T, U) comprise both a specularly reflected component and a diffusely reflected component from the road surface ( 16 ); and a control unit ( 20 ) comprising a microprocessor programmed to process the parameter (PC) indicative of the superficial condition of said road surface ( 16 ), based on an intensities of said second laser signals (S, T, U), said intensities being determined by a number of photons detected, in use, by said plurality of SPADs ( 11 a , 11 b , 11 c ); said parameter being indicative of the superficial condition selected from a group consisting of a dry, a partially wet, a completely wet, or an icy road surface ( 16 ); wherein said sensor ( 10 ) further comprises: a plurality of polariser filters ( 25 a , 25 b ) configured to be hit by selected ones of the second laser signals (S, T, U) determined by the reflections of said first laser signal (R) on said road surface ( 16 ), each of the reflections are optically aligned with a respective one of the plurality of SPADs ( 11 a , 11 b ), configured to receive the second laser signals (S, T, U) reflected from the road surface ( 16 ); wherein said second laser signals (S, T, U) comprise a first component polarised in a first plane (P) and a second component polarised in a second plane (Q); and wherein the plurality of SPADs ( 11 a , 11 b , 11 c ) comprise a plurality of first SPADs ( 11 a , 11 b ) arranged in sequence relative to said polariser filters ( 25 a , 25 b ) and associated with respective polariser filters of said plurality of polarizer filters ( 25 a , 25 b ), so as to detect said first or second polarised component; and a second SPAD ( 11 c ) not associated with any polariser filter and arranged with an optical axis substantially coincident with a normal (N) direction to said road surface ( 16 ), said second SPAD ( 11 c ) being configured to detect a third, non-polarised component of said second laser signals (S, T, U) generated, in use, through the diffuse reflection of said first laser signal (R) on said road surface ( 16 ); wherein said control unit ( 20 ) is programmed to process said parameter (PC) indicative of said superficial condition of said road surface ( 16 ), based on a first intensity (ITM) of said first component and on a second intensity (ITE) of said second component, wherein said first intensity (ITM) and said second intensity (ITE) are determined by photon-counting measurements performed by a respective one of the plurality of first SPADs ( 11 a , 11 b ); said first plane (P) being, in use, parallel to said road surface ( 16 ) and said second plane (Q) being, in use, orthogonal to said road surface ( 16 ).
  2. 2 . The motor vehicle according to claim 1 , wherein the emitter ( 16 ) is configured to emit said first laser signal (R) along a direction defining, in use, an angle (θ) with the normal (N) direction to said road surface ( 16 ) in a point of incidence (H) of said first laser signal (R) on said road surface ( 16 ).
  3. 3 . The motor vehicle according to claim 2 , wherein the plurality of first SPADs ( 11 a , 11 b ) are configured to detect said second signals(S) along a direction defining, in use, the same angle (θ) with said normal (N) direction; said emitter ( 16 ) and said plurality of first SPADs ( 11 a , 11 b ) being symmetrically arranged on opposite sides of said normal (N); said second signals(S) being generated, in use, through the specular reflection of said first signal (R) on said road surface ( 16 ).
  4. 4 . The motor vehicle according to claim 2 , wherein said emitter ( 16 ) and said plurality of first SPADs ( 11 a , 11 b ) are arranged on the same side of said normal (N) direction; said selected ones of the second laser signals (S, T, U) being generated, in use, by the diffuse reflection of said first signal (R) on said road surface ( 16 ).
  5. 5 . The motor vehicle according to claim 1 , wherein said control unit ( 20 ) is programmed to process a polarisation contrast value (PC) equal to ITE - ITM ITE + ITM , wherein ITE is the intensity of said second component (ITE) and ITM is the intensity of said first component (ITM); said control unit ( 20 ) being programmed to: acquire a first value of said angle (θ) and/or a second value associated with the sum of said first and second component (ITE, ITM) and/or a third value associated with said intensity (SC) of said third non-polarised laser signal (T); compare said value of said polarisation contrast (PC) with at least one or a range of said first, second and third value; and process said parameter based on said comparison.
  6. 6 . The motor vehicle according to claim 1 , wherein the motor vehicle comprises: a sprung mass comprising said body ( 2 ); and an unsprung mass comprising said wheels ( 4 , 5 ) and elastically connected to said sprung mass.
  7. 7 . A method to detect a parameter associated with a superficial condition of a road surface ( 16 ), comprising: detecting the parameter associated with the superficial condition of the road surface ( 16 ) with a sensor ( 10 ) by; i) emitting a first laser signal (R); ii) reflecting said first laser signal (R) onto said road surface ( 16 ) to generate second laser signals (S, T, U), wherein said second laser signals (S, T, U) comprise both a specularly reflected component and a diffusely reflected component from the road surface ( 16 ), and wherein said second laser signals (S, T, U) comprise a first component polarised in a first plane (P), a second component polarised in a second plane (Q), and a third non-polarized component; iii) detecting said second laser signals (S, T, U) by means of a plurality of single-photon avalanche diodes (SPADs) ( 11 a , 11 b , 11 c ) configured to detect the second laser signals (S, T, U); iv) processing the parameter (SC) associated with the superficial condition of said road surface ( 16 ), based on intensities of said second laser signals (S, T, U); said intensities being associated with a number of photons detected, in use, by said plurality of SPADs ( 11 a , 11 b , 11 c ), wherein the plurality of SPADs comprises a plurality of first SPADs ( 11 a , 11 b ) and a second SPAD ( 11 c ), wherein the plurality of first SPADs are arranged in sequence relative to polariser filters ( 25 a , 25 b ) for detecting the first component polarised in the first plane (P) and the second component polarised in the second plane (Q), and wherein the second SPAD ( 11 c ) is not associated with any polariser filter and is arranged with an optical axis substantially coincident with a normal (N) direction to said road surface ( 16 ) for detecting the third non-polarized component; said parameter being associated with said superficial condition selected from a group consisting of a dry, a partially wet, a completely wet, or an icy road surface ( 16 ); v) filtering, by means of a plurality of polariser filters ( 25 a , 25 b ), said second laser signals (S, T, U) determined by the reflection of said first laser signal (R) on said road surface ( 16 ); said reflected second laser signals (S, T, U) comprising the first component polarised in a first plane (P), the second component polarised in a second plane (Q), and the third non-polarised component; and vi) detecting, by means of the plurality of first SPADs ( 11 a , 11 b ) said first or second polarised component and/or detecting by means of the plurality of second SPAD ( 11 c ) the third, non-polarised component; and vii) processing said parameter associated with said superficial condition of said road surface ( 16 ), based on a first intensity (ITM) of said first component and on a second intensity (ITE) of said second component, and/or by an intensity of the third, non-polarised component; said first plane (P) being, in use, parallel to said road surface ( 16 ), said second plane (Q) being, in use, orthogonal to said road surface ( 16 ), and said third non-polarised component being at the normal (N) direction to the road surface ( 16 ).
  8. 8 . The method according to claim 7 , wherein detecting said second laser signals (S, T, U) comprises detecting specular reflection from said road surface ( 16 ); and/or through diffuse radiation returning from said road surface ( 16 ).
  9. 9 . The method according to claim 8 , wherein detecting the third, non-polarised component comprises detecting an intensity (SC) of a third non-polarised laser signal (T) generated, in use, through the diffuse radiation of said first laser signal (R) on said road surface ( 16 ).
  10. 10 . The method according to claim 9 , further comprising processing a polarisation contrast value (PC) equal to ITE - ITM ITE + ITM , wherein ITE is the intensity of said second component (ITE) and ITM is the intensity of said first component (ITM); acquiring a first value of an angle (θ) of incidence of said first laser signal (R) on said road surface ( 16 ) and/or a second value associated with the sum of said first and second component (ITE, ITM) and/or a third value associated with said intensity (SC) of said third non-polarised laser signal (T); comparing said value of said polarisation contrast (PC) with at least one or a range of said first, second and third value; and processing said parameter based on said comparison.
  11. 11 . A computer product including a non-transitory readable medium loaded onto and executed by a control unit ( 20 ) and designed, when the computer product is executed, to implement the steps of the method according to claim 7 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority from Italian patent application no. 102022000022356 filed on Oct. 31, 2022, the entire disclosure of which is incorporated herein by reference. TECHNICAL FIELD The invention relates to a motor vehicle and to a method to detect a parameter associated with a superficial condition of the road surface. More in particular, the superficial conditions of the road surface, for instance the presence of ice or of partially or completely wet asphalt, determine the grip of the tyres on the road surface and significantly affect driving safety. BACKGROUND Motor vehicles are known, which comprise systems capable of estimating the grip of the tyres on the road surface. Said systems comprise, in a known manner: one or more capacitive, piezoelectric or optical sensors capable of adopting temperature and/or humidity measures in an area surrounding the road surface on which the motor vehicle travels; anda control unit programmed to process said measures, to estimate a value of the coefficient of grip of the tyres on the road surface and to identify the consequent condition of potential danger based on the signals. In known solutions, the grip coefficient is estimated only at particularly high travel speeds of the motor vehicle, close to the grip limit. Consequently, when the travel speed is low, the aforesaid systems risk detecting the condition of potential danger too late or in a way that is not consistent with the actual grip conditions of the road surface. In the automotive industry, the conditions of the road surface need to be detected in a correct and prompt manner even when the motor vehicle travels at low speeds or when the motor vehicle is parked, so as to increase the degree of safety of the motor vehicle. SUMMARY The aforesaid object is reached by the invention, as it relates to a motor vehicle as defined in claim 1. The invention also relates to a method to detect a parameter associated with a superficial condition of the road surface as set forth in claim 8. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be best understood upon perusal of the following detailed description of a preferred embodiment, which is provided by way of non-limiting example, with reference to the accompanying drawings, wherein: FIG. 1 is a perspective view of a motor vehicle according to the invention; FIG. 2 is a functional diagram of a sensor and of a control unit incorporated in the motor vehicle 1, with parts removed for greater clarity; FIG. 3 schematically shows a first embodiment of the sensor of FIG. 1, with parts removed for greater clarity; FIG. 4 schematically shows a second embodiment of the sensor of FIG. 1, with parts removed for greater clarity; FIGS. 5 and 6 graphically show the values of respective tables stored in the control unit of the sensor of FIGS. 1 to 4; and FIG. 7 schematically shows, on a much larger scale, further components of the sensor of FIGS. 2 to 6. DESCRIPTION OF EMBODIMENTS With reference to the accompanying Figures, number 1 indicates a motor vehicle comprising a body 2 defining a passenger compartment 3 and a plurality of wheels 4, 5. In particular, the motor vehicle 1 comprises, in a known manner, a sprung mass comprising the body 2 and an unsprung mass comprising the wheels 4, 5 and elastically connected to the sprung mass through the suspensions. Hereinafter, expressions such as “at the top”, “at the bottom”, “at the front”, “at the back” and others similar to them are used with reference to normal travel conditions of the motor vehicle 1. Furthermore, it is possible to define: a longitudinal axis X integral to the motor vehicle 1, which, in use, is horizontal and parallel to a normal driving direction of the motor vehicle 1;a transverse axis X integral to the vehicle 1, which, in use, is horizontal and orthogonal to the axis X; andan axis Z integral to the vehicle 1, which, in use, is vertical and orthogonal to the axes X, Y. The motor vehicle 1 further comprises a sensor 10 designed to detect a parameter associated with an operating condition of the motor vehicle 1. In the specific case shown herein, the sensor 10 is an optical sensor. The operating condition is a condition representative of the condition of a road surface 16 and/or the individual travel speed of each wheel 4, 5. In particular, the expression “condition representative of the condition of the road surface” indicates, for example, a condition of partially wet, completely wet, snow-covered or icy road surface 16. The sensor 10 advantageously comprises: an emitter 15 configured to emit a laser signal R; andone or more single-photon avalanche diodes 11a, 11b; 11c (also known as SPADs) configured to receive a laser signal S, T; U reflected by the road surface 16 through mirror-like reflection or through diffuse radiation. More in detail, the sensor 10 and the emitter 15 are both mounted on the body 3. The emitter 15 is configured so as to emit a laser