Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/17—Using electrical or electronic regulation means to control braking
  • B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
  • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
  • B60W40/02—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to ambient conditions
  • B60W40/06—Road conditions
  • B60W40/064—Degree of grip
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T2210/00—Detection or estimation of road or environment conditions; Detection or estimation of road shapes
  • B60T2210/10—Detection or estimation of road conditions
  • B60T2210/12—Friction
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T2210/00—Detection or estimation of road or environment conditions; Detection or estimation of road shapes
  • B60T2210/10—Detection or estimation of road conditions
  • B60T2210/13—Aquaplaning, hydroplaning
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T2210/00—Detection or estimation of road or environment conditions; Detection or estimation of road shapes
  • B60T2210/30—Environment conditions or position therewithin
  • B60T2210/36—Global Positioning System [GPS]

Definitions

• the present invention is in the field of motor vehicles, and in particular in the field of systems and devices for assisting the driving of such vehicles.
• ABS brake assist systems
• ESP electronic trajectory correctors
• the adhesion margin information can also be transmitted to safety or steering systems present in the vehicle, such as a cruise control or braking devices.
• various solutions for estimating the potential for adhesion available between a tire and the road on which rolls the tire are based on the solicitation of the adhesion potential up to a certain level, for example half of the maximum potential, and propose to extrapolate the maximum potential available.
• these solutions require a maneuver close to the limit of adhesion, which does not allow to leave a sufficient safety margin for the driver of the vehicle, especially in conditions of low level of adhesion.
• none of these solutions offers an estimate of the potential available in real time.
• the present invention aims to remedy these drawbacks by proposing a solution for determining a margin of adhesion, and its use to provide a driver and / or a vehicle with relevant driving assistance information. .
• the invention relates to a method for determining an anticipated adhesion margin of a tire on a roadway, the method comprising the following steps in which:
• the potential for adhesion available at a given moment between a tire of the vehicle and the road surface on which the tire is rolled is estimated as a function of known and / or measured influencing parameters.
• a future adhesion requirement is determined in anticipation, as a function of parameters included in the group comprising: a current or future rolling situation of the vehicle, meteorological data, cartographic data, data relating to the driver, -
• a comparison criterion is applied between the adhesion potential and the need for adhesion to come, to determine a margin of adhesion.
• the estimate of an adhesion potential can be carried out in real time, that is to say, it estimates the potential of the ground on which the vehicle is rolling, at the moment when we estimate.
• the adhesion potential estimated at an instant n is considered to be identical at an instant n + 1 if the parameters having an influence on the adhesion have not changed between the instants n and n + 1 .
• the estimate can also be made in advance on a known future path, either because the trip was recorded in a vehicle navigator, or because it is possible, from a GPS position of the vehicle , to know the road on which the vehicle moves.
• a method according to the invention comprises an initial step of determining influential parameters on the adhesion potential, these parameters being included in the group comprising the grip number of the roadway, the height at road sand or average texture depth called PMT, the height of the water on the road surface, the surrounding air temperature, the running speed, and all the characteristics of the tire having an influence on the adhesion, in particular but not exclusively the tire pressure, its tread height, its load, and the type of tire.
• the grip number of the roadway can be provided by pre-existing maps.
• the temperature can be measured in real time, for example by sensors currently available on a vehicle.
• the parameters of the tire such as the pressure, the tread height, the load and the rolling speed can be determined by systems embedded in the vehicle or in the tires.
• the initial step of determining influential parameters comprises a step of measuring the sound power generated by the tire during taxiing, and a step of determining the height of water on the roadway. and the height of sculpture according to this sound power.
• the macro-texture of the road is also determined according to this sound power.
• the vehicle in which a method according to the invention is implemented must be provided with a microphone installed in the tires or in the front or rear bumpers of the vehicle.
• the number of parameters having a potential impact on the noise of the tire can be significant. However, it appears that certain parameters have a weak or second-order influence on the nature of the noise generated by the tire. This may be the case for example of the internal pressure of the tire or the load of the tire.
• the weather condition of the road characterized by a height of water on the roadway, seems to be a parameter of the first order. Its impact on the noise of the tire is very important and especially weakly dependent on all the other parameters such as the state of the road surface, the state of wear of the tire or the type of tire tread. These other parameters are also likely to a lesser extent to vary the rolling noise as far as it is known to discern their own acoustic signatures.
• this water level differentiates a dry road from a wet road, characterized by a height of water flush with the natural roughness of the road surface, or a wet road for which the height of water exceeds the level of natural roughness of the pavement of the road.
• this height of water on the road is estimated using one of the means included in the group comprising:
• fixed weather stations installed along the road, and including means of communicating to vehicles traveling on the road the water level during their passage, - optical sensors embedded on the vehicle,
• a coating is called a closed coating when it takes a smooth appearance and without macro-roughness, such as a bitumen having sown after having undergone high temperatures.
• a coating will be considered open, when macro-roughness is important like that of a coating used or that of a country road repaired quickly using a superficial coating made by projecting pebbles on bitumen.
• a medium coating describes all the coatings in an intermediate state between the two preceding states and more particularly qualifies the new coatings.
• the different macro-textures can thus be categorized as follows: a closed macro-texture coating has a PMT between 0 and 0.4 millimeters.
• a medium macro-texture coating has a PMT between 0.4 and 1.1 millimeters, and an open macro-texture coating has a PMT greater than 1.1 millimeters. It is known that the macro-roughness of a coating strongly influences the noise generated by the tire. In particular, the phenomenon of pumping air trapped between the ground and the sculpture of the tire is all the more pronounced that the road surface is closed. Real-time knowledge of the condition of a road can be useful if, for example, this information is returned by a large number of vehicles or a dedicated fleet of vehicles, to a centralized tracking and monitoring system. maintenance of the road network.
• the tire tread height which characterizes its state of wear, one distinguishes the new state, the worn state, and an intermediate state considered here as the state of the tire with mid-wear.
• Information about the evolution of the wear characteristic over time is useful, especially if it is coupled with the information of the weather condition of the road. Indeed, it is known that a vehicle equipped with worn tires which rolls on a wet coating is more likely to lose its grip than if it had new tires.
• the estimate of a remaining sculpture height is given in real time by one of the means included in the group comprising:
• Optical sensors evaluating the evolution of the height of sculpture, these sensors being on board the vehicle or installed on the ground,
• the type of sculpture of the tire is, for example, a summer type sculpture or a winter type sculpture.
• These two types of tires are essentially distinguished by treads with different, more directional, heavily cut and laminated tread patterns in the case of winter sculptures, less directional and less notched in the case of summer sculptures, as well as by the nature of the tread patterns. materials forming the tread, softer in the case of winter tires, and harder in the case of summer tires. These characteristics are not without influence on the behavior and handling of the vehicle, and therefore on its adherence.
• the step of determining an adhesion potential as a function of the speed is performed by the implementation of predetermined adhesion level abacuses.
• steps are implemented, will be subsequently described in detail using figures:
• Adhesion level plots are constructed according to influential parameters. - The values of these parameters are measured in real time.
• the abacus corresponding to the values of the parameters is selected, and
• the estimated value of the adhesion potential is read on the chart for the actual speed of travel. 1-4 - Rolling radius method
• the step of determining an available adhesion potential comprises the following steps:
• a model for estimating the adhesion potential is established by determining a function connecting the rolling friction potential and the vehicle parameters,
• the rolling radius is determined and, by applying said model, and depending on the vehicle parameters, the adhesion potential of said tire is evaluated.
• a method according to the invention provides for determining a need for anticipated adhesion, a function of one or more sets of parameters included in the group comprising: a running situation in progress or future vehicle, weather data, map data, driver data.
• the estimate of a need for adhesion can be performed using accelerations determined in real time.
• it is sufficient to consider the global acceleration ⁇ experienced by the vehicle in relation to a need for adhesion which is also global, then there exists between the adhesion and the acceleration a simple mathematical relation g- ⁇ ⁇ , where g is the gravitational constant.
• g- ⁇ ⁇
• g is the gravitational constant.
• the vehicle accelerations are, in one embodiment, measured by accelerometer type devices embedded directly on the vehicle, or installed in external devices present inside the vehicle, such as a smartphone or tablet. . Acceleration can also be measured on the CAN bus of the vehicle.
• the CAN bus of the vehicle also provides information such as speed V and ⁇ ⁇
• speed V and ⁇ ⁇ the speed of curvature
• the need for adhesion is determined by estimating, according to a future rolling maneuver, the forces that will be transmitted to the ground.
• the axis OX will designate the axis representing the circumferential direction of the tire, OY the axis parallel to the axis of rotation of the tire or transverse axis, and OZ 1 axis normal to the axis of rotation of the tire, or radial axis.
• a first simplifying hypothesis will be used which makes it possible to obtain a need for adhesion with a precision of order 0.
• the next event is a curve
• y (V) V 2 / R, in the absence of slope and tilt.
• predetermined driver categories are used.
• the principle of this classification is, using a concept of adequate distance, to group the users in classes, each as homogeneous as possible and, between them, as distinct as possible.
• the classes are such that the intra-class variance is minimized, while the intergroup variance is maximized.
• the number of classes used is chosen a posteriori, and is considered adequate if the interclass variance does not decrease significantly by adding a class.
• the categories are determined using not all the available observations, but only part of these observations. For example, observations on relevant driving areas, such as turns or areas of high acceleration, will be chosen.
• the relevant driving zones are for example determined by mapping the driving area, or by a vehicle behavior during a passage on these areas, the behavior being for example analyzed in view of a speed and / or a vehicle acceleration on these areas. It is then possible to store in the vehicle the different driver categories and their associated speed profiles. Thus, in this embodiment, knowing the category in which the vehicle is located, and knowing the path taken by the vehicle, it is possible to determine the acceleration that will undergo the vehicle, and therefore the need for adhesion .
• ABS driver and driver assistance systems
• a division is made between the necessary acceleration, determined in the context of the estimate of the anticipated adhesion requirement, and the determined adhesion potential, possibly multiplied by the constant g .
• This gives a value that corresponds to a percentage of consumed margin.
• a percentage of the remaining or available margin could also be determined by subtracting the margin percentage consumed from 100.
• a subtraction is performed between the same two values as above, and a residual acceleration potential is thus obtained.
• the adhesion margin thus determined can be used to create alerts, for example to the driver, so that he can adapt his driving in the case where the margin of adhesion would become too low.
• the determination of an alert threshold takes into account a reserve of margin or acceleration which incorporates a consumption of adhesion necessary for the efforts to be transmitted to the ground, even at constant speed. .
• elements such as the resistance to the progress, the aerodynamic forces, the slope, induce a consumption of adhesion which is not taken into account by the preceding computations.
• it is useful to permanently maintain a sufficient margin of adhesion for example, to allow to pass a braking force.
• an alert threshold is set at 25% margin reserve and / or 0.2 acceleration reserve points.
• alert thresholds are set which change according to the speed.
• a method according to the invention further comprises a step of informing the driver of the adhesion margin consumed and / or available.
• This display can take different forms which will be further detailed with the aid of the figures. One can thus consider displaying a percentage of adhesion consumed or available in real time. One can also consider using colors corresponding to different alert thresholds as explained above.
• the margin of adhesion that will be communicated to the driver of a vehicle, or to a system installed in the vehicle will be the margin directly resulting from the comparison between the need for adhesion and the potential. adherence, or a corrected margin, taking into account the uncertainties of determination, and a reserve braking or acceleration, previously mentioned.
• margin of adhesion can be displayed as a color on the map of a browser
• FIG. 1 shows an example of abacuses that can be used in a method according to the invention, for determining an adhesion potential
• FIG. 2 shows graphs representing a need for anticipated adhesion as a function of a rolling speed and an available grip potential as a function of a rolling speed
• FIG. 3 shows predetermined curves of adhesion potential as a function of a weather condition of the road and a state of the tire associated with anticipated adhesion requirements for different types of drivers on a given turn of the path,
• FIGS. 4a and 4b show examples of conductive alert display implemented in a method according to the invention.
• FIGS. 5a and 5b show examples of implementation of a method according to the invention in a vehicle. DESCRIPTION OF THE BEST MODE OF CARRYING OUT THE INVENTION
• FIG. 1 shows an example of abacuses that can be used in a method according to the invention, for determining an adhesion potential.
• the charts are parameterized according to the influential parameters that are available during an implementation of the invention, for example the water height and the sculpture height, and are plotted as a function of the running speed.
• the number of charts to be created is therefore a function of the number of values of these quantities that we will measure. Typically if it is known to measure 2 levels of wear (new / worn) and 2 levels of humidity (dry / wet), we will create 4 charts corresponding to the possible combinations of these two states. If certain combinations lead to very close adhesion results, the number of abacus can be reduced.
• the charts are constructed in several stages:
• a statistical distribution of each of the inputs of the model is determined. As many abacuses are computed as there will be a combination of these parameters but each is calculated with a very small standard deviation around the value of the parameter measured. Typically, the identification of a worn tire reduces the distribution to 2mm ⁇ 1.5mm instead of 5mm ⁇ 4mm in the absence of this information. The accuracy of the adhesion estimation is greatly improved.
• N variants of ⁇ are calculated with these N combinations for P speed cases (typically 11 cases of speeds ranging from 30 to 130 km / h in steps of 10 km / h)
• FIG. 1 shows four curves on which:
• - S4 is the grip available for a worn tire, on a wet road.
• FIG. 2 shows the preferential mode of determining this speed.
• Curve 20 represents the need for adhesion of a vehicle as a function of the rolling speed. This need is for example determined in real time according to a running maneuver in progress, or even in advance depending on a future driving maneuver, or predetermined information depending on the category of the driver and the driver. journey to come.
• Curve 21 represents the available adhesion potential as a function of the rolling speed. This adhesion potential being determined by one of the methods described in the present application.
• the rolling limit speed corresponds to the speed 22 at the intersection of curves 20 and 21.
• the grip potential ⁇ is available February 3 ⁇ , and adhesion is consumed ⁇ 2 3 ⁇ ⁇ Therefore, the adhesion margin at this speed 23 is the difference between ⁇ 3 ⁇ 4 ⁇ and ⁇ 2 3 ⁇ ⁇
• the speed margin speed 22 - speed 23
• FIG. 3 shows an optimal use in terms of resources of a method according to the invention for determining the curve 20 described in FIG. 2.
• the graph shows four groups of points, called K1, K2, K3 and K4, corresponding to the need for adhesion called by different drivers in the different driving categories, and observed, in the graph shown, at a given position d a driving maneuver.
• the points VK1, VK2, VK3 and VK4 represent the speeds obtained by statistical processing, stored in the vehicle for this position on the path, and synthesize respectively the four categories of predetermined driver.
• SI is the available grip for a new tire, on a wet road
• Figures 4a and 4b show examples of display, for a driver of the vehicle, information concerning a margin of adhesion.
• a display in the form of a target having three concentric circles.
• the central circle for example displayed with a green color, represents indicates that the adhesion consumed is between 0 and 60% of the available adhesion.
• the intermediate circle for example displayed with an orange color, indicates that the adhesion consumed is between 60%> and 80%> of the available adhesion, and the outer circle, for example displayed with a red color, indicates that the adhesion consumed is between 80%) and 100%) of the available adhesion.
• a color gradation will preferably be chosen to alert the driver to the risk gradation of his driving.
• the adhesion is shown in two dimensions, respectively corresponding to the transverse and longitudinal components of the stresses.
• FIG. 4b it is chosen to display the information only in one dimension, and therefore the standard of adhesion is used rather than the two components.
• the display of Figure 4b there are three areas, displayed with three different colors, and has thresholds similar to those of Figure 4b.
• the same type of display could be obtained to show not a history of adhesions consumed, but instead an anticipated margin of adhesion on a path to come.
• the invention makes it possible to determine a need for adhesion in anticipation, as a function of map data, and thus to deduce an anticipated margin of adhesion at different points of a future path.
• This display could be performed according to the two transverse and longitudinal dimensions, according to the estimate as previously described in Part II-4.
• Figures 5a and 5b show examples of implementation of a method according to the invention in a vehicle.
• Figure 5a shows more particularly an implementation using a connected device not integrated in the vehicle, type Smartphone or tablet.
• the device 100 includes GSM communications means for receiving external data such as maps or traffic information or the like.
• the device 100 comprises means for receiving information enabling the GPS location of the vehicle or a determination of the vehicle speed.
• the vehicle also comprises a computer 101a installed in the vehicle, and connected to different sensors such as microphones 102 and 103.
• This computer 101a comprises signal processing means from the sensors 102 and 103 to obtain information. concerning a height of water on the road, a texture depth of the road, a state of wear or pressure of the tire.
• the vehicle further comprises other sensors, such as temperature sensors, wear sensors, pressure sensors installed directly on the vehicle and / or on the tires.
• the computer 101a comprises signal processing means from all the sensors.
• the information is sent from the computer 101a to the device 100, which implements a method according to the invention to determine a margin of adhesion, and display it on a screen integrated in the device 100.
• a method according to the invention is implemented directly in the computer 101b of the vehicle.
• this computer is connected to sensors 102 and 103 which have the same functions as in the example of FIG. 3a.
• the computer 101b is connected to the CAN bus of the vehicle, in order to read information such as the speeds and / or accelerations of the vehicle.
• the display and control module 200 integrated in the vehicle comprises GSM communication means for receiving external data such as maps or traffic information or other information and means for receiving GPS geolocation information. of the vehicle. It can make this information available to the computer 101b on the CAN communication bus.
• This module 200 is also provided with display means for displaying the adhesion margin, to inform the driver.
• the characteristics of the tire are taken into account for the implementation of the method.
• these characteristics are stored in a vehicle memory, and / or an identifier of the tire is read by an RFID type reading, and associated with characteristics stored in a database, and / or the adhesion model.
• implemented in the computer 101b or in the device 100 is chosen from a set of adhesion models as a function of an identifier of the tire.

Landscapes

• Engineering & Computer Science (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Automation & Control Theory (AREA)
• Mathematical Physics (AREA)
• Control Of Driving Devices And Active Controlling Of Vehicle (AREA)
• Traffic Control Systems (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=57136973

Family Applications (1)

Country Status (3)

Families Citing this family (3)

Family Cites Families (7)

• 2016
  • 2016-05-20 FR FR1654540A patent/FR3051422A1/fr active Pending
• 2017
  • 2017-05-22 EP EP17730866.5A patent/EP3458317A1/de not_active Withdrawn
  • 2017-05-22 WO PCT/FR2017/051245 patent/WO2017198972A1/fr unknown

Also Published As

Similar Documents

Legal Events