# US 7,487,669 B2 · Method of estimating a risk of a lack of connecting with the ground for a motor vehicle > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,487,669 B2 - Document ID: US7487669B2 - Status: Granted - Kind: B2 - Application number: 12/002,203 - Filed: 2007-12-13 - Published: 2008-07-03 - Granted: 2009-02-10 - Earliest claimed: 2006-12-13 - Assignees: Michelin Recherche et Technique S.A. - Inventors: David Bertrand - Web page: https://patentgrep.com/patent/US7487669B2 ## CPC - B60T 8/172: Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters {(B60T8/17551 takes precedence)} - B60W 40/064: Degree of grip - B60W 40/068: Road friction coefficient - B60G 2400/8222: Hydroplaning - B60G 2600/02: Retarders, delaying means, dead zones, threshold values, cut-off frequency, timer interruption - B60G 2800/92: ABS - Brake Control - B60G 2800/94: Electronic Stability Program (ESP, i.e. ABS+ASC+EMS) - B60T 2210/13: Aquaplaning, hydroplaning - B60W 10/04: including control of propulsion units - B60W 10/18: including control of braking systems - B60W 30/18172: {Preventing, or responsive to skidding of wheels} - B60W 50/14: Means for informing the driver, warning the driver or prompting a driver intervention - B60W 2050/0071: {Controller overrides driver automatically} - B60W 2520/26: Wheel slip - B60T: VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL (electrodynamic brake systems for vehicle, in general B60L; brakes per se, i.e. devices where braking effect occurs, including ultimate brake actuators, F16D); ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES - 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 - B60G: VEHICLE SUSPENSION ARRANGEMENTS (air-cushion vehicles B60V; {cycle suspensions B62K25/00}) ## Abstract According to the method, the risk is estimated as a function of a maximum grip potential μmax of the tire, a utilization percentage Pu representative of the fraction of the maximum grip potential of the tire that is being used, and a magnitude Ps associated with a risk of the tire hydroplaning, in particular a loss of tire area. ## Claims ### Claim 1 A method of estimating a risk of a lack of connection with the ground for a motor vehicle, this lack being associated with the grip state of at least one tire of the vehicle, wherein the risk is estimated as a function of the following three parameters: a maximum grip potential μmax of the tire; a utilization percentage Pu of the maximum grip potential of the tire that is being used; and a magnitude Ps associated with a risk of the tire hydroplaning, in particular a loss of tire area. ### Claim 2 (depends on 1) The method according to claim 1, in which the risk of a lack of connection with the ground is estimated by comparing, for each parameter, a corresponding reference value Vr that is a function of at least one measurement of the parameter with at least one threshold Sn associated with the parameter and separating a range of values that are risky from a range of values without risk. ### Claim 3 (depends on 2) The method according to claim 2, in which the threshold Sn varies as a function of the running conditions of the vehicle, preferably as a function of the load of the vehicle and/or of its speed. ### Claim 4 (depends on 2) The method according to claim 2, in which, if for at least one parameter, the reference value Vr crosses the threshold Sn to reach the risky range, the driver of the motor vehicle is informed of the estimated risk of a lack of connection with the ground. ### Claim 5 (depends on 2) The method according to claim 2, in which, if for at least one parameter, the reference value Vr crosses the threshold Sn to reach the risky range, and if the reference value Vr remains in said risky range while the vehicle is running along a predetermined distance Ln measured from the time at which the threshold Sn was crossed, then the driver of the motor vehicle is informed of the estimated risk of a lack of connection with the ground. ### Claim 6 (depends on 2) The method according to claim 2, in which the reference value Vr of a parameter is defined as being equal to a single measurement of the parameter. ### Claim 7 (depends on 2) The method according to claim 2, in which, when the parameter P is the maximum grip potential μmax of the tire or the utilization percentage Pu of the maximum grip potential μmax of the tire, then the reference value Vr is defined by a linear combination of a plurality of measurements of the parameter, e.g. two or four measurements, the different measurements relating to different tires of the vehicle. ### Claim 8 (depends on 7) The method according to claim 7, in which the linear combination of measurements is selected from: an average of the measurements; and a center of gravity of the measurements such that each measurement is weighted by a value for the vertical load Fz supported by the tire corresponding to the measurement. ### Claim 9 (depends on 2) The method according to claim 2, in which, when the parameter P is associated with a loss of tire area Ps, the reference value Vr is defined as being the maximum value of a plurality of measurements of the parameter Ps, e.g. two or four measurements, the different measurements relating to different tires of the vehicle. ### Claim 10 (depends on 2) The method according to claim 2, in which each measurement is performed by a device selected from: a device provided with stationary means that are decoupled in rotation from the tire; and a device provided with on-board means in a member of a rotary assembly comprising a tire of the vehicle and/or a member coupled to rotate with the tire. ### Claim 11 (depends on 2) The method according to claim 2, in which a first level of risk of a lack of connection with the ground is estimated by comparing, for at least one parameter, the reference value Vr with a first threshold S1, and a second level of risk of a lack of connection with the ground is estimated by comparing the reference value Vr with a second threshold S2, the risk of the second level being higher than the risk of the first level.