A method for managing intervention events of an antiaquaplaning system

Abstract

Method for managing intervention events of an anti-aquaplaning system (1; 100) for a vehicle, comprising at least a first and a second injector (2, 4) configured to inject liquid towards the ground (G) in a forward position, respectively, to a right tread (RT) and to a left tread (LT) of a right wheel (R) and a left wheel (L) of an axle of the vehicle, the method comprising: • - acquiring a signal representative of the need for intervention of the system, • - identifying a plurality of risk factors relevant to the possibility of a collision following loss of vehicle control during an aquaplaning event, • - acquiring signals representative of each risk factor, • - defining a collision risk indicator (CR) and determining a value of said risk indicator, • - confirming the need for intervention of the anti-aquaplaning system and control the intervention if the value of said risk indicator is higher than a threshold.

Description

[0001] "A method for managing intervention events of an anti- aquaplaning system"

[0002] TEXT OF THE DESCRIPTION

[0003] Field of the Invention

[0004] The present invention refers to anti-aquaplaning systems for motor vehicles . Speci fically, the invention has been developed with reference to the antiaquaplaning systems based on the inj ection of liquid in a forward position to the tread .

[0005] Prior Art

[0006] The Applicant has already developed and proposed anti-aquaplaning systems for vehicles , based on the inj ection of liquid in a forward position to the tread of the front wheels of a motor vehicle , the inj ected liquid being drawn from the tank of the windshield washer fluid of the motor vehicle . An example of such systems is described in the Italian Industrial Invention Patent Application n . 102014902296915 .

[0007] Subsequently, the Applicant has developed methods for determining the interface conditions between the tyre and the ground, speci fically for determining the occurrence of aquaplaning events , described in the Patent Applications 102021000017588 and 102022000021216 .

[0008] All the research carried out by the Applicant , as well as the general research carried out in the field, are based on the assumption of the availability of an anti-aquaplaning system with l iquid inj ection which draws liquid from a tank having a substantially endless availability with respect to the frequency of the intervention events . In other words , the deductive logic leading to the determination of the need for an intervention event - both as developed by the Applicant and as possibly implemented on third-party known systems - have never taken into account a possible limited-use pattern of the availability of liquid for the antiaquaplaning system .

[0009] It shall be noted that the limited use is not a need in itsel f . On the contrary, the limited use derives from the goal of reducing as much as possible the functional dependence of the aquaplaning system on the equipment on board the vehicle , such as e . g . the container of the windshield washer fluid (which is also typically the tank wherefrom the system draws liquid for the inj ection) . Moreover, the limited use enables avoiding the installation of a pump for the liquid of the anti-aquaplaning system on board the vehicle .

[0010] With a reduced or totally eliminated dependence , it is possible to implement the anti-aquaplaning system as a totally sel f-contained unit ( a sort of "plug-and-play" unit ) while reducing its complexity, its costs ( thanks to the absence of the pump ) , its encumbrance and the possible di f ficulties of an integration into manufactured vehicles ( for example , the need is avoided for a di f ferent container of windshield washer fluid) .

[0011] However, as stated in the foregoing, the known solutions operate without taking into account a pos sible limited use , and therefore control the interventions of the accumulation system simply on the basis of determinations concerning the travelling conditions of the vehicle . This inevitably leads to a number of intervention events which is excessive in comparison to the actual safety needs of the travelling vehicle .

[0012] Obj ect of the Invention

[0013] The invention aims at solving the technical problems outlined in the foregoing . Speci fically, the invention aims at providing a method for controlling an anti-aquaplaning system which has functional features speci fically concerning the needs of systems with limited resources , and which maintains the same safety level as the known methods .

[0014] Summary of the Invention

[0015] The obj ect of the invention is achieved by means of a method having the features set forth in the claims that follow, which form an integral part of the technical disclosure provided herein with relation to the invention .

[0016] Brief Description of the Figures

[0017] The invention will now be described with reference to the annexed Figures , which are provided by way of non-limiting example only and wherein :

[0018] - Figure 1 is a schematic representation of an antiaquaplaning system according to a first embodiment of the invention,

[0019] - Figures 2 and 3 are representations of operating configurations of a component of the system of Figure 1 , while Figure 4 corresponds to a cross-section view along the line IV- IV of Figure 3 , and

[0020] - Figure 5 is a schematic representation of an antiaquaplaning system according to a second embodiment of the invention .

[0021] Detailed Description

[0022] Reference 1 in Figure 1 generally denotes an anti aquaplaning system for a motor vehicle according to a first embodiment of the invention .

[0023] The system 1 comprises at least a first and a second inj ector 2 , 4 configured to inj ect liquid towards the ground G in a forward position, respectively, to a left tread LT and to a right tread RT of a left wheel L and a right wheel R of an axle of the motor vehicle . The system 1 moreover comprises at least one fluid accumulator 6 , configured to store pressuri zed liquid (preferably water ) and being in fluid communication with the first inj ector 2 and the second inj ector 4 .

[0024] Referring to the preferred embodiment of Figure 1 , the system 1 comprises a single accumulator 6, being in fluid communication with both injectors 2, 4. The fluid communication is implemented by way of a three-way connection 8 comprising two outlets 10, 12 towards the injectors 2 and an inlet 14 from the accumulator 6. Of course, embodiments are possible with one accumulator for each injector 2, 4. According to the invention, each accumulator 6 comprises a recharge port, configured to restore the amount of liquid within the accumulator. The recharge port is configured in different ways, according to the considered embodiment of the invention.

[0025] The system 1 comprises at least one flow control element, including a first operating condition, wherein it is configured to enable a flow of liquid in the fluid communication between the fluid accumulator 6 and the injectors 2, 4, on the occurrence of an intervention of the anti-aquaplaning system 1 comprising the injection of liquid by means of the injectors 2, 4, and a second operating condition, wherein it is configured to disable a flow of liquid in the fluid communication between said fluid accumulator 6 and the injectors 2, 4 when an intervention of the anti-aquaplaning system is not required. In the case of a single accumulator 6, it is possible to envisage a single flow control element at the inlet 14, but preferably there are envisaged a first flow control element 16 and a second flow control element 18 which are operationally associated, respectively, to the injectors 2, 4. The association may comprise either a functional integration only, or both a functional and a structural integration with the corresponding injector 2, 4. Preferably the flow control elements 16, 18 are implemented as two-way, two-position (open / closed) electrically driven valves.

[0026] The electric driving of the valves 16, 18 takes place by means of an (electronic) control unit CU, configured to enable the first operating condition and the second operating condition of the at least one flow element based on the need for an intervention of the anti-aquaplaning system . The unit CU sends output ( driving) signal s S 16 , S 18 to the valves 16 , 18 , while the unit CU receives a signal AS corresponding to an activation signal of the intervention of system 1 .

[0027] In the embodiment of Figure 1 and, generally speaking, in the first embodiments of the invention, the inlet 14 is implemented by means of a series connection of a recharge valve 20 and a sensori zed hydraulic connection port 22 , preferably with a quick release coupling to the connection 8 , whereon there is fixed the valve 20 and whereat there is installed a pressure sensor 24 , configured to detect the pressure o f the liquid at the inlet 14 and, consequently, at the outlets 10 , 12 . In this regard, reference S24 denotes an operative connection - speci fically a signal connection - between the sensor 24 and the unit CU ( the signal S24 is input into the unit CU) .

[0028] On a practical level , the recharge port comprises the assembly of valve 20 and connection port 22 , although from a functional point of view the entry of the liquid into the accumulator 6 takes place through valve 22 , as will be described in the following .

[0029] In other words , in the present embodiments the recharge port comprises a hydraulic connection port - provided on the valve 20 - through which the fluid connection is established between ( each) accumulator 6 and the inj ectors 10 , 12 (which are associated based on the number of accumulators 6 ) .

[0030] Referring to Figures 2 and 3 , the valve 20 comprises a casing 26 extending along a valve axis X22 and comprising a valve seat V26 at a first end thereof . In this regard, it shall be borne in mind that the presence of the connection port 22 is not strictly mandatory, since both the quick release coupling at the connection 8 and the provision of the pressure sensor 24 may easily be implemented directly on the casing 26 .

[0031] The valve 20 moreover includes a plug 28 , which is movable within the casing 26 along the valve axis X22 . The plug 28 is maintained in contact with the valve seat V26 by means of an elastic element 30 provided between a shoulder 32 of the plug 28 and a shoulder 34 of the casing 26 , arranged at a second end of the casing 26 opposite the first end .

[0032] At the valve seat V26 there is provided a through hole 36 which establishes a fluid communication between the interior of the casing 26 and the connection 8 ( through the connection port 22 ) : in this way, the recharge port is structurally implemented on the connection port 22 , but functionally at the seat V26 , speci fically with the hole 36 conveying the liquid towards the valve seat V26 , wherefrom the liquid may enter the accumulator 6 . I f the connection port 22 is not provided, the recharge port is practically implemented, structurally and functionally, on the casing 26 .

[0033] The contact between the plug 28 and the valve seat V26 may be separated by means of a pressure action against an influence surface S28 of the plug at the valve seat V26 , wherein the pressure action may be exerted by a liquid pressing onto the recharge port 36.

[0034] The valve 20 moreover comprises a manoeuvering element of the plug, denoted by reference number 38 and configured to separate the contact between the plug 28 and the valve seat V26 regardless of the presence of a pressure action on the influence surface S28 of the plug at the valve seat V26 .

[0035] The valve 20 includes an operating condition, wherein it is configured to enable a flow of liquid exiting the accumulator 6 , and a recharge condition, wherein it is configured to enable a flow of liquid entering the accumulator 6 and to disable a flow of liquid exiting the accumulator 6 . The manoeuvering element 38 is used to maintain the valve 20 in the operating condition, while it is substantially deactivated when the valve 20 is required to operate in the recharge condition .

[0036] More speci fically, the manoeuvering element of the plug 38 comprises a pin 40 having an axis Y40 incident , preferably orthogonal , to the valve axis X26. The pin 40 in turn includes a first operating position, defining a first protrusion Pl inside the casing 26 , and a second operating position defining a second protrusion P2 inside the casing 26 , the second protrusion being greater than the first protrusion Pl . The protrusion Pl , P2 is measured between the inner wall of the casing 26 and a tip end of the manoeuvering element 38 , which may be identi fied as a (preferably conical ) free end 40T of the pin 40 .

[0037] The transition from the protrusion Pl to the protrusion P2 , and vice versa, is preferably obtained by providing the pin 40 with a thread on the outer surface , and by engaging the thread with a corresponding ( inner ) thread in the wall thickness of the casing 26 and / or on a threaded collar 42 fixed onto the outer surface of said casing 26 . Preferably, the actuation of the manoeuvering element 38 is implemented by means of a manoeuvering wheel 44 , which is connected in rotation to the pin 40 .

[0038] The plug 28 comprises a tang 46 , configured to contact the valve seat , and a land 48 adj acent to the tang 46 - preferably integral therewith - comprising a surface 50 tapered towards the valve seat V28 . The elastic element 30 is therefore located between the land 50 - which therefore acts as the shoulder 32 - and the shoulder 34 .

[0039] The land 48 moreover comprises a guide surface 52 , configured to guide the plug 28 in the movement along the valve axis X26 , particularly to of fer a guide along the inner walls of the casing 26. The guide surface 52 has a cylindrical shape , in the same way as the inner wall of the cas ing 26 , while the surfaces of mutual contact of the tang 46 and of the valve seat 28 are conical .

[0040] In order to enable operability in the operating and recharge conditions , the land 48 is grooved by through grooves 54 , which identi fy passageways for the liquid between the land 48 and the casing 26 , particularly between the guide surface 52 and the casing 26 . Figure 4 shows a section where it is possible to see the profiles of the grooves 54 , which impart - in the configuration of Figure 4 - a substantially cruci form outline to the land 48 , both at the guide surface 52 and at the tapered surface 50 .

[0041] In the second (working) operating position of the manoeuvering element 38 , which is visible in Figure 2 , the tip end 40T of the manoeuvering element contacts the tapered surface 50 of the plug 28 thus determining, by means of the second (positive ) protrusion P2 , a separation of the contact between the plug 28 and the valve seat V26 . In other words , the contact and the force exchange between the surface 50 and the tip end 40T leads the plug 28 to a new axial position - separated from the seat V26 - wherein the protrusion P2 may be accommodated without an interpenetration between the stem 40 and said surface 50 . In this regard, the contact preferably occurs in an area which has no grooves 54 . In such conditions , the volume of pressuri zed liquid within the accumulator 6 is constantly in fluid communication with the connection 8 , as far as upstream of the valves 16 , 18 . As a consequence , the sensor 24 detects the pressure of the liquid within the accumulator 6 . The flow of liquid from the accumulator 6 towards the inj ectors 2 , 4 is thus fully enabled, after opening the valves 16 , 18 by means of the signal S 16 , S 18 provided by the unit CU at the reception of the activation signal AS .

[0042] On the contrary, in the first ( recharge ) operating position of the manoeuvering element 38 , which is visible in Figure 3 , the first protrusion Pl (which in this case is negative ) is insuf ficient to determine a separation of the contact between the plug 28 and the valve seat V26 . This means that in the first operating position the protrusion Pl is insuf ficient to establish a contact between the end 40T and the tapered surface 50 , or that the condition of contact without interpenetration is compatible with a position of the plug 28 whereby the tang 46 contacts the valve seat V26 . In this condition, the flow of liquid from the accumulator 6 towards the connection 8 is prevented by the seal of the plug 28 against the seat V26 . However, the connection o f the valve 20 - at the hole 36 - to a supply of pressuri zed liquid acts on the influence surface S28 , thereby separating the contact of the plug 28 against the seat V26 and enabling recharging the accumulator 6 .

[0043] The system 1 in the embodiments of Figures 1 to 4 substantially corresponds to an anti-aquaplaning system with a limited-use volume of liquid, which is replaceable and isolated ( the recharge port ) from any fluidic circuit of the vehicle configured for a single use - or, depending on the volume of the accumulator and on the charge pressure of the gas , for a maximum of two uses - on the occurrence of an intervention of system 1 .

[0044] The recharge of the volume of liquid, which in this case corresponds to the replacement of the accumulator 6 as i f it were a cartridge of consumable material , is possible thanks to the quick release hydraulic connection between the sensori zed hydraulic connection port 22 and the valve 20 at the recharge port defined by the hole 36 and by the valve seat V26 .

[0045] At an operational level , the system 1 may be installed on board a vehicle already during manufacturing, because it does not need to be integrated with the other systems of the vehicle , with the exception of a prior preparation for the accommodation and a data access on the CAN network for the unit CU .

[0046] Each accumulator 6 is filled with liquid at a pressure of about 150 Bar, and with pressuri zed gas (preferably nitrogen) through port 6R . The charge pressure of the gas is about 60 bar . The charge pressure of the gas may anyway vary depending on the si ze and / or the volume of the accumulators .

[0047] At an operational level , in the manufacturing site of the vehicle and / or in the manufacturing site of the system 1 the gas charge is performed through port 6R by means of pressuri zed nitrogen cylinders commonly available on the market . Subsequently, the necessary amount of liquid is charged (which varies depending on the envisaged global performances of the system and on the number of allowable uses ) , which may be comprised between 1 . 3 and approximately 2 litres for an average application .

[0048] The charging of the liquid takes place by means of a high-pressure pump through the valve 20 in the position of Figure 3 , wherein it operates as a one-way valve : the pressure of the liquid separates the contact between the plug 28 and the seat V26 , thereby enabling the flow of liquid towards the volume of the accumulator 6 . The flow is moreover enabled by the grooves 54 , which substantially bridge the gap between the surface 52 and the inner surface of the casing 26 . The charging takes place with the connection port 22 connected to the valve 20 , because it provides a quick release hydraulic coupling both to the connection 8 and to the recharge plant .

[0049] Once the charge of the accumulator 6 is completed, the latter is removed from the recharge plant by separating the connection port 22 ( or the valve 22 , in the absence of the connection port 22 ) while maintaining the valve 20 in the recharge position . In this case , the pressure of the liquid within the accumulator restores the contact between the plug 28 and the seat V26, thus preventing the liquid from leaking out .

[0050] Next , the accumulator 6 is installed into the system 1 on board the vehicle, again by means of the quick release coupling provided by the connection port 22 , the valve 20 always remaining in the recharge position . Once it has been ascertained that the valves 16 , 18 are in the closed position, the valve 20 may be brought to the operating configuration ( Figure 2 ) by acting on the manoeuvering element 38 .

[0051] In the operating position, the plug 28 is kept separated from the seat V26 , and therefore nothing prevents the exit of the liquid from the accumulator 6 except for the valves 16 and 18 . Only when the unit CU transmits the signals S 16 and S 18 , which control the opening of the valves 16 and 18 , can the liquid flow forward and be inj ected towards the ground by the inj ectors 16 , 18 .

[0052] In any case , it is possible to provide monitoring and safety systems , in order to ensure that the described operations are consistent with the state of the various valves , and in order to avoid potentially dangerous actions . At the end of the charging and installation operations , the vehicle is ready for delivery . It is to be noted that a depleted accumulator 6 may be immediately replaced with a full accumulator already available at the recharge plant , and the removed depleted accumulator 6 may subsequently be recharged and sent to a store of full accumulators at the recharge plant .

[0053] Referring to Figure 5 , reference number 100 generally denotes an anti-aquaplaning system according to second embodiments of the invention . The same reference numbers as previously adopted denote the same components , whereas only the di f ferent reference numbers (with the addition of one hundred) denote the parts which are modi fied with respect to system 1 .

[0054] The system 100 and the system 1 are the same from the point of view of structure and circuitry; the only di f ference concerns the inlet to the connection 8 , which is here denoted by reference 114 . In this embodiment , the passageway 114 is a single hydraulic element , which is part of the fluid communication between the accumulator 6 and the inj ectors 2 , 4 and comprises a recharge port 136 - preferably provided with a quick release hydraulic connection - corresponding to a hydraulic connection port arranged branch-wise with respect to the fluid communication between the accumulator 6 ( each accumulator, i f more than one are present ) and the inj ectors 2 , 4 . At the port 136 there is arranged a one-way valve 138 (which replaces the valve 20 ) configured to enable only the entry of the liquid towards the accumulator 6 . A pressure sensor 124 is moreover arranged on the passageway 114 , and it is operationally connected to the unit CU .

[0055] Unlike system 1 , the system 100 is always of a single activation type (possibly with the option of a double activation, i f the conditions of the remaining liquid allow it ) , but the recharge of the liquid takes place without removing the accumulator 6 and by means of the port 136 , which is accessible by a fixed recharge plant , present in a servicing workshop .

[0056] In greater detail , in the system 100 the recharge operations envisage connecting the port 136 - acces sible from the engine compartment - to the external recharge plant , and activating the latter until the charge pressure of the liquid is attained ( the gas is previously charged at the manufacturing site , during the production of the accumulator ) . Once the recharge is completed, the pressure of the liquid in the system 100 is checked by means of the sensor 124 and the access to the unit CU . I f necessary, the unit CU is reset, and the system 1 is ready for another activation . The latter two operations may be automated by using information from the pressure sensor 124 . At the end of such operations , the fixed recharge plant is then disconnected from the port 136 .

[0057] Similarly to the known anti-aquaplaning system, the systems 1 , 100 operate - by using the unit CU as an interface - on the basis of an activation signal generated by an electronic system for the detection of an aquaplaning condition, for example of the type described in the Patent Applications 102021000017588 and 102022000021216 , mentioned at the beginning of the present description .

[0058] According to the invention, because of the limited use of the liquid in the systems 1 , 100 - due to the isolation from the fluidic circuitry of the vehicle - the determination of the activation signal AS takes advantage of a further deduction level which benefits from the integration with driving assistance systems (ADAS ) in order to identi fy the really dangerous aquaplaning conditions in combination with provided risk factors . This leads to a reduction of the intervention events of the systems 1 , 100 to the minimum number from the safety point of view, considering the reduced availability of liquid for the interventions .

[0059] More speci fically, research on the performances of an anti-aquaplaning system in the normal use of a vehicle shows the importance of considering the risk factors regarding the conditions of the surrounding area on the occurrence of an aquaplaning event .

[0060] Considering the vehicle in a condition of beginning or actual loss of control ( due to an aquaplaning event ) , the risk of such grip loss leading to an actual collision depends on a few factors which are not strictly related with the aquaplaning event itsel f . Some of said factors are summari zed in the following Table 1 : Most such factors are evaluated ( or may be evaluated) and are trans formed (or may be trans formed) into signals available on the CAN network of the vehicle by the ADAS systems on board the vehicle , as indicated by the following Table 2 :

[0061] A global evaluation of the level of collision risk due to grip loss in a given situation is then performed by combining all the risk factors which are present at the same time , for example by assigning weights (which may be either fixed or connected to each of the levels of the other parameters ) to each of them . It is therefore possible to define a collision risk indicator CR as a weighed linear combination of the signals obtained from the CAN network :

[0062] CR = Z [ a ( Tr, Tc, 0, LC, OA, OV, DR, R, TW) • V + b (V, Tc, 0, LC, OA, OV, DR, R, TW) • Tr + c (V, Tr, 0, LC, OA, OV, DR, R, TW) • Tc + d (V, Tr, Tc, LC, OA, OV, DR, R, TW) • 0 + e (V, Tr, Tc, 0, OA, OV, DR, R, TW) • LC + f ( Tr, Tc, 0, LC, OV, DR, R, TW) • OA + g ( Tr, Tc, 0, LC, OA, DR, R, TW) • OV + h ( Tr, Tc, 0, LC, OA, OV, R, TW) • DR + i ( Tr , Tc, 0, LC, OA, OV, DR, TW) • R + 1 (V, Tr, Tc, LC, OA, OV, DR, R) • TW] wherein a, b, c, d, e , f , g, h, i , 1 represent weight parameters as a function of the various risk factors (with the exception of one of them, the one by which they are multiplied) .

[0063] Generally speaking, each weight parameter a, b, c, d, e , f , g, h, i , 1 is a function of at least one of the signals representative of each ris k factor and obtained from the CAN network .

[0064] Substantially, the collision risk indicator CR represents a weighed sum of the various risk factors , wherein the weight of each factor may be a function of the other risk factors . When the algorithm for the detection of the aquaplaning condition, which is implemented on board the vehicle ( regardless of its type , not necessarily as described in the Patent Applications 102021000017588 and 102022000021216 , mentioned at the beginning of the present description - although they represent preferred solutions ) determines an intervention condition of the systems 1 , 100 , the actual activation of the system ( i . e . the signal AS ) depends on a further check based on the indicator CR . In other words, the activation of the anti-aquaplaning system is always mediated by the indicator CR.

[0065] More precisely, the invention envisages enabling the intervention of the systems 1, 100 - but this may be extended to any known anti-aquaplaning system based on the injection of liquid, even if the amount of its use is not limited - if the value of the indicator CR is higher than a threshold level which is deemed critical as regards safety. In other words, the anti-aquaplaning system is activated if the determination of an aquaplaning condition is positive, with the related intervention request, and (logic AND) if the value of CR is higher than the threshold value.

[0066] In order to exemplify such activation logic, suppose a vehicle is travelling along a straight line (Tr - low level) on a motorway, in rainy weather conditions, at a speed of 110 Km / h. Suppose that the vehicle meets an area of such water build-up as to determine an aquaplaning condition. If the vehicle keeps on advancing at a constant speed (V - medium risk) , if the driver does not request a change of trajectory (LC = 0, DR = 0) , if there are no other vehicles in the vicinity (OV = 0) , if there are no obstacles in the trajectory (0 = 0) , if the road surface is even (OA = 0) , if the road is straight and very wide (and in this case it is, therefore R = 0, TW = 0) , then - especially if all the previous conditions are true at the same time - although the algorithm for the detection of aquaplaning conditions indicates an absence of control, the real risk is very low and in itself it is insufficient to determine the need for activating the anti-aquaplaning system. This corresponds to a value of the collision risk indicator CR which is lower than the threshold value .

[0067] If, on the contrary, the vehicle is in the identical conditions as in the previous case, but if it meets a water build-up in the track having an asymmetrical distribution with respect to the vehicle axis (a pool of water only on one side of the vehicle) , the consequences are the appearance of a yaw moment on the vehicle (which may or may not be countered by the driver' s reaction) or a lack of grip uniformity, with an increase of the risk factors DR and OA up to a point which may exceed the threshold value for CR, and which may determine the need for an intervention of the anti-aquaplaning system, with the consequent delivery of the liquid jet, in order to restore the attitude of the vehicle and avoid a tailspin.

[0068] It shall be noted that the set of risk factors listed in the foregoing is very well adapted, due to the intrinsic characteristics of these factors, to obtain estimates of a collision risk which are reformulated in a simplified way on the basis of the risk factors Tc (curved trajectory) and 0 (obstacles) . These two risk factors, as can also be inferred from the representative signals available on the CAN network, practically summarize the majority of the other listed risk factors, and therefore they may be used as a primary reference for the calculation. For example, the risk factor Tc includes at least the risk factors V, LC, OA, DR, R, in the same way as the risk factor 0 includes at least the risk factors OV, TW, R.

[0069] The consequence is that, in preferred embodiments, it is possible to operate on the basis of a criterion which divides the risk factors into risk factors due to the trajectory travelled by the vehicle (TR) and into risk factors due to possible obstacles (e.g. vehicles, objects, people, etc.) which are present on said traj ectory (CT) .

[0070] In such embodiments, therefore, a decision sequence is implemented having the features provided in the following .

[0071] In a first step, a determination is made of an actual / current grip coefficient: based on the digital systems on board the vehicle and / or on the basis of additional sensors connected to the autonomous driving functions, such as cameras or LiDARs, it is possible to determine the grip coefficient of the vehicle. Specifically, it is possible to determine whether a partial or total aquaplaning event is taking place and to determine the coefficient of friction associated with the rear axle and the front axle, and the variation thereof due to aquaplaning.

[0072] In a second step, a determination is made of a trajectory (TR) and a surrounding environment (CT) for the vehicle.

[0073] When the vehicle is travelling, two criteria based on said indicators (TR, CT) shall always be met. The first criterion (TR) corresponds to the ability of the vehicle to follow the desired trajectory while remaining within the track, i.e. without leaving the roadway. This is verified when a given trajectory is travelled at a speed which is correct for the current grip coefficient.

[0074] The second criterion (CT) corresponds to the need of avoiding an impact against other vehicles or generally against obstacles. In other words, it corresponds to a contact exclusion area between the vehicle and the surrounding objects (including vehicles) . As for driving, the vehicle is regulated in speed and position based on a safety distance, which takes into account the grip coefficient and the driver's reaction time. If the safety coefficient decreases, the safety distance shall be increased.

[0075] The trajectory and the surroundings of the vehicle may be calculated by using the same systems used for autonomous driving, which actually shall always respect the two criteria mentioned in the foregoing . For example , it is possible to use the cameras to detect the presence of other vehicles or other obstacles , or to define the traj ectory that the vehicle shall follow in order to remain on the roadway . Distance sensors may help determine the space between the vehicle itsel f and the preceding vehicle . By also using the data from sensors of the steering angle ( e . g . the angle of the steering wheel ) , of the gas pedal , of the brake , it is also possible to determine the traj ectory that the driver requests .

[0076] In a third step, a determination is made on whether the traj ectory and the surrounding area are correct for the current grip coef ficient . This steps also takes into account elements of the vehicle dynamics which may be complicated at will , in order to increase the level of detail of the mathematical modelling . To clari fy, consider the following simpli fication, based on three equations : gx = gy wherein :

[0077] Fx is a resultant of the longitudinal forces on the vehicle

[0078] Fy is a resultant of the transverse forces on the vehicle gx is a longitudinal grip coef ficient of the vehicle gy is a transverse grip coef ficient of the vehicle g is the gravitational acceleration of the Earth m is the mass o f the vehicle

[0079] Ax is a longitudinal acceleration of the vehicle

[0080] Ay is a transverse acceleration of the vehicle Moreover, it is possible to write an equation which defines the narrowest trajectory (i.e. the trajectory having the minimum radius of curvature R) that the vehicle may travel as a function of the exclusion area (CT) and on the basis of a total grip coefficient p calculated as the square root of the sum (px2+ py2)

[0081] V2 / R = pg

[0082] Once the current coefficient of friction has been calculated as defined in the first step (therefore the grip coefficients px, py, p are known) , also the maximum accelerations are known which the vehicle is able to withstand depending on the friction against the ground.

[0083] In the second step, a calculation is made of the surrounding area CT and the trajectory TR which the vehicle shall face. From these values, it is possible to define the longitudinal acceleration Ax(TR, CT) and transverse acceleration Ay(TR, CT) which the vehicle shall respect in order to follow the trajectory TR and respect the surrounding area CT.

[0084] If at the same time both conditions p > Ax(TR, CT) / g and (logic AND) p > Ay(TR, CT) / g are met, no need for action is determined, and therefore no intervention is defined for the anti-aquaplaning system.

[0085] As a matter of fact, in these conditions the grip coefficient is higher than any other action taken by the vehicle .

[0086] If at least one (logic OR) of the conditions p < Ax(TR, CT) / g and p < Ay(TR, CT) / g is met, the current grip coefficient is insufficient to tackle with the possible actions taken by the vehicle, and therefore it is insufficient to assist possible emergency tra j ectories / braking . As a consequence, corrective actions are taken which may include, i.a., the activation of the anti-aquaplaning system 1, 100. A fourth step corresponds to the definition of the corrective actions . Once ascertained that the avai lable grip is insuf ficient to support possible emergency manoeuvres or manoeuvres which are feasible by the vehicle , a further di f ference is defined to avoid unnecessary activations of the system 1 , 100 . For example , consider the case of a vehicle following another vehicle at a distance which is correct for a total grip coef ficient of p=0 . 8 (wet tarmac ) and wherein the sensor network on board the vehicle detects said value of the grip coef ficient .

[0087] I f the vehicle maintains the same safety distance from the preceding vehicle , this implies a possible risk, since the preceding vehicle may need to brake , and therefore the following vehicle would be too close to avoid an impact , due to the decrease in the coefficient of friction . On the contrary, i f the preceding vehicle does not brake but advances at constant speed or even accelerates , the following vehicle is not in a condition of direct and imminent danger . In this case , a possibility would consist in taking advantage of the instants during which the preceding vehicle advances at a constant speed for decelerating the following vehicle and creating a safety condition, thereby increasing the grip coef ficient .

[0088] On the other hand, i f the preceding vehicle brakes , the current grip coef ficient may not be suf ficient to avoid impact . In this case , it is useful to increase the grip coef ficient during braking, in order to help avoid the impact . The analysis provided in the foregoing may be performed individually for the longitudinal and the transverse movements of the vehicle , or for the movements having a mixed longitudinal and transverse composition .

[0089] In the case of a braking of the preceding vehicle , the condition constitutes a possible danger . In the other instances - with the preceding vehicle advancing at constant speed or accelerating - the condition constitutes an actual danger, and it is generally associated with an activation of the anti-aquaplaning system 1 , 100 .

[0090] In order to minimi ze the activations and the consumption of the system, it is preferable to act in the following fashion .

[0091] In the case of possible danger, as long as the activation of the anti-aquaplaning system does not appear as being strictly necessary, it is possible to act by means of autonomous driving systems or by issuing a warning to the driver, so that the vehicle may decelerate and restore the safety conditions .

[0092] In the case of actual danger, the activation of the anti-aquaplaning system 1 , 100 is resorted to when such intervention is able to actually improve the grip coef ficient p and consequently to help the vehicle avoid an impact with the preceding vehicle ( or generally with an obstacle ) . It shall be noted that the conditions of possible danger and the conditions of actual danger correspond to the collision risk indicator CR, more precisely to a condition below the intervention threshold (possible danger ) and respectively to a condition above the intervention threshold ( actual danger ) .

[0093] When the logic of detection of the aquaplaning condition (whatever it may be ) determines the occurrence of such a condition, the activation of the liquid j et depends on a further check of the presence of actual danger . I f an actual danger is detected, the antiaquaplaning system is activated in the described fashion .

[0094] Generally speaking, the invention therefore defines a method for managing intervention events of an anti- aquaplaning system 1, 100 for a vehicle, comprising at least a first and a second injector 2, 4 configured to inject liquid towards the ground G in a forward position, respectively, to the right tread RT and the left tread LT of a right wheel R and a left wheel L of an axle of the vehicle, the method comprising:

[0095] - acquiring a signal representative of the need for intervention of the anti-aquaplaning system 1, 100,

[0096] - identifying a plurality of risk factors V, Tr, Tc, 0, LC, OA, OV, DR, R, TW (see Table 1) relevant to the possibility of a collision following loss of vehicle control during an aquaplaning event,

[0097] - acquiring, from an in-vehicle data network (for example a CAN network) , signals representative of each risk factor (see Table 2 - in the example described in the foregoing such signals comprise, i.a., the accelerations Ax and Ay) ,

[0098] - defining the collision risk indicator CR based on a combination of the signals representative of each risk factor, and determining a value of the risk indicator CR (conditions of actual or possible danger, and / or position of p with respect to the ratios Ax(TR, CT) / g and Ay (TR, CT) / g) ,

[0099] - confirming the need for intervention of the antiaquaplaning system 1, 100 and control the intervention if the value of the risk indicator CR is higher than a threshold value.

[0100] As described in the foregoing, the method also comprises denying the need for intervention of the antiaquaplaning system and preventing the intervention if the value of the risk indicator CR is below said threshold value.

[0101] As observed in the foregoing, this applies both to the anti-aquaplaning systems 1, 100 and to other known anti-aquaplaning systems based on the injection of liquid in a forward position to the tread . In the case of the systems 1 , 100 , such a logic maximi zes the extension of the intervals between recharges of the accumulators 6 , since it enables an activation of the systems 1 , 100 only when it is strictly neces sary .

[0102] According to the duration of the j et and / or of the pressure detected by the sensors 24 , 124 , the unit CU may decide whether to allow a further use of the system 1 , 100 ( i f the remaining pressure is suf ficient for a second activation) , or to warn the driver, by means of a warning light on the dashboard, that the system 1 , 100 shall be restored, suggesting that it is necessary to reach a workshop while adopting a cautious driving style .

[0103] The following procedure for replacing the accumulator ( s ) 6 at the workshop is similar to what has been described in the foregoing with respect to the recharge method . It is to be noted that the servicing workshops may be equipped with accumulators 6 already charged with gas and liquid, in such a way as to speed up the replacement operation and to provide for a subsequent recharge the accumulator 6 disassembled from the vehicle , to check it and to make it available for a later use on another vehicle .

[0104] In this way, the cost of the replacement for the customer will not include the whole cost of the accumulator 6 , but only of the recharge and check operations .

[0105] With anti-aquaplaning systems for which the availability of liquid does not constitute a problem, the method according to the invention enables in any case to optimi ze the liquid consumption, especially when the latter is shared with other systems of the vehicle , such as e . g . the windshield washer system or the cleaning system for the sensors which support the driving assistance systems . Of course , the implementation details and the embodiments may amply vary from what has been described and illustrated herein, without departing from the scope of the present invention as defined in the annexed claims .

Claims

CLAIMS1. A method for handling intervention events of an anti-aquaplaning system (1; 100) for a vehicle comprising at least a first and a second injector (2, 4) configured to inject fluid towards the ground (G) in a forward position, respectively, to a right tread (RT) of a right wheel (R) and a left tread (LT) of a left wheel (L) of an axle of the vehicle, the method comprising:- acquiring a signal representative of the need for intervention of the anti-aquaplaning system (1; 100) ,- identifying a plurality of risk factors (V, Tr, Tc, 0, LC, OA, OV, DR, R, TW) relevant to the possibility of a collision following loss of vehicle control during an aquaplaning event, acquiring, from an in-vehicle data network, signals representative of each risk factor,- defining a collision risk indicator (CR) based on a combination of said signals representative of each risk factor, and determining a value for said risk indicator (CR) ,- confirming the need for intervention of the antiaquaplaning system and control an intervention if the value of said risk indicator (CR) is higher than a threshold value.

2. The method according to claim 1, comprising denying the need for intervention of the antiaquaplaning system and preventing the intervention if the value of said risk indicator (CR) is below said threshold value.

3. The method according to claim 1 or claim 2, wherein said combination comprises a linear combination of weight parameters (a, b, c, d, e, f, g, h, i, 1) and signals representative of each risk factor, wherein each signal is assigned a corresponding weight parameter (a, b, c, d, e, f, g, h, i, 1) .

4. The method according to claim 3, wherein each weight parameter is a function of at least one of said signals representative of each risk factor.

5. The method according to claim 4, wherein each weight parameter is not a function of the signal representative of the risk factor to which it is assigned .

6. The method according to any one of the preceding claims, wherein the risk factors comprise:- a speed of the vehicle- the negotiation of a straight line trajectory- the negotiation of a curved trajectory- the presence of obstacles along the trajectory- a change of trajectory- a homogeneity of grip- presence of other vehicles in a row- driver reactions and / or the existence of a vehicle yaw moment- type of road travelled- width of the roadway.

7. The method according to claim 6, wherein the signals representative of each risk factor comprise:- Vehicle speed- Steering angle- Signals from cameras and / or radar and / or LiDAR- Yaw rate- Lateral acceleration- Wheel slip- GPS signal- a composition of a plurality of the above listed signals .

8. The method according to claim 1, wherein said risk factors comprise a vehicle trajectory (tr) and a contact exclusion area between the vehicle and surrounding objects (cr) ,wherein said acquiring, from an in-vehicle data network, signals representative of each risk factor comprises : determining a minimum radius of curvature traj ectory that the vehicle can travel as a function of said exclusion area, and a longitudinal acceleration (Ax ( tr, cr ) ) and a transverse acceleration (Ay ( tr, cr ) ) of the vehicle along said minimum radius of curvature tra ectory determining a current value of the overall coef ficient of friction of the vehicle and wherein said defining a collision risk indicator ( CR) on the basis of a combination of said signals representative of each risk factor, and determining a value of said risk indicator ( CR) comprise comparing said current value of the overall coef ficient of friction of the vehicle with said longitudinal acceleration (Ax ( tr, cr ) ) and transverse acceleration (Ay ( tr, cr ) ) of the vehicle along said minimum radius of curvature traj ectory .

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