# US 9,751,533 B2 · Road surface friction and surface type estimation system and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,751,533 B2 - Document ID: US9751533B2 - Status: Granted - Kind: B2 - Application number: 14/244,273 - Filed: 2014-04-03 - Published: 2015-10-08 - Granted: 2017-09-05 - Earliest claimed: 2014-04-03 - Assignees: The Goodyear Tire & Rubber Company - Applicants: The Goodyear Tire & Rubber Company - Inventors: Kanwar Bharat Singh - Web page: https://patentgrep.com/patent/US9751533B2 ## CPC - B60W 40/068: Road friction coefficient - B60C 23/02: Signalling devices actuated by tyre pressure {(hand-held tyre pressure gauges G01L17/00)} - B60C 23/20: Devices for measuring or signalling tyre temperature {only} - B60T 8/172: Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters {(B60T8/17551 takes precedence)} - G01M 17/02: Tyres - B60T 2210/12: Friction - B60T 2240/06: Wheel load; Wheel lift - B60T 2270/86: Optimizing braking by using ESP vehicle or tyre model - 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 - B60C: VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES - 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 - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## Abstract A tire-based system and method for estimating road surface friction includes a model-based longitudinal stiffness estimation generator using tire-based parameter inputs and vehicle-based parameter inputs; an actual longitudinal stiffness estimation generator using real-time vehicle-based parameter inputs; and a tire road friction estimation generator for deriving a tire road friction estimation from a comparative analysis between the actual longitudinal stiffness estimation and the model-based longitudinal stiffness estimation. A road surface classifier algorithm is employed to generate a road surface type analysis from the road friction estimation, an ambient air temperature measurement, and an ambient air moisture measurement. ## Claims ### Claim 1 A tire-based system for estimating road surface friction comprising: at least one tire mounted to a wheel hub and supporting a vehicle; at least one tire sensor mounted to the at least one tire; at least one vehicle sensor mounted to the vehicle; a model-based longitudinal stiffness estimator producing a model-based longitudinal stiffness estimation for the one tire from a set of tire-based inputs generated from the at least one tire sensor and a first set of vehicle-based inputs generated from the at least one vehicle sensor; an actual longitudinal stiffness estimator producing an actual longitudinal stiffness estimation from a second set of vehicle-based inputs generated from the at least one vehicle sensor; a tire road friction estimator deriving a road friction estimation from a comparative analysis between the actual longitudinal stiffness estimation and the model-based longitudinal stiffness estimation. ### Claim 2 (depends on 1) The system of claim 1, wherein the set of tire-based inputs include at least one input from the group: a measured air cavity pressure of the one tire; tire-specific construction characteristics of the one tire; and a measured temperature of the one tire. ### Claim 3 (depends on 1) The system of claim 1, wherein the second set of vehicle-based inputs include at least one input from the group: a measured wheel speed of the vehicle; a measured wheel torque; and a measured wheel slip ratio. ### Claim 4 (depends on 3) The system of claim 3, wherein the first set of vehicle-based inputs include a measured hub vertical acceleration, the system further comprising a tire wear state estimator for producing a wear state estimation for the one tire from the measured hub vertical acceleration. ### Claim 5 (depends on 4) The system of claim 4, wherein the tire wear state estimator operably produces the tire wear state estimation from a detected a shift in a vertical mode of the one tire. ### Claim 6 (depends on 3) The system of claim 3, wherein the model-based longitudinal stiffness estimator algorithmically calculates the longitudinal stiffness estimation from the first set of vehicle-based inputs and the set of tire based inputs including vehicle load, the measured air cavity pressure of the one tire and the measured temperature of the one tire compensated by the estimated tire wear state. ### Claim 7 (depends on 6) The system of claim 6, wherein the actual longitudinal stiffness estimator comprises a longitudinal force estimator for generating a longitudinal force estimation from the measured wheel speed and the measured wheel torque. ### Claim 8 (depends on 7) The system of claim 7, wherein the longitudinal force estimator comprises a sliding mode observer model. ### Claim 9 (depends on 8) The system of claim 8, wherein the actual longitudinal stiffness estimator calculates the actual longitudinal stiffness estimation from the longitudinal force estimation and the measured wheel slip ratio. ### Claim 10 (depends on 9) The system of claim 9, wherein the actual longitudinal stiffness estimator comprises a recursive least square algorithm with forgetting factor. ### Claim 11 (depends on 1) The system of claim 1, further comprising a road surface classifier algorithm operably conducting a road surface type analysis based on the road friction estimation, an ambient air temperature measurement, and an ambient air moisture measurement. ### Claim 12 (depends on 11) The system of claim 11, wherein the road surface classifier algorithm comprises a modified sensor fusion algorithm. ### Claim 13 A tire-based method of estimating road surface friction based on at least one tire mounted to a wheel hub and supporting a vehicle, comprising: generating a set of tire-based parameter inputs from at least one tire sensor mounted to the at least one tire; generating a first set and a second set of vehicle-based parameter inputs from at least one vehicle sensor mounted to the vehicle; generating a model-based longitudinal stiffness estimation from the set of tire-based parameter inputs and the first set of vehicle-based parameter inputs; generating an actual longitudinal stiffness estimation from the second set of vehicle-based parameter inputs; and deriving a tire road friction estimation from a comparative analysis between the actual longitudinal stiffness estimation and the model-based longitudinal stiffness estimation. ### Claim 14 (depends on 13) The method of claim 13, further comprising: using as the set of tire-based parameter inputs at least one parameter input from the group: measured air cavity pressure of the one tire; tire-specific construction specifications of the one tire; and temperature of the one tire. ### Claim 15 (depends on 14) The method of claim 14, further comprising: using as the second set of vehicle-based parameter inputs at least one input from the group: measured wheel speed of the vehicle; measured wheel torque; and measured wheel slip ratio. ### Claim 16 (depends on 15) The method of claim 15, wherein further comprising: using as one of the first set of vehicle-based inputs a measured hub vertical acceleration; and generating a tire wear state estimation of the one tire from the measured hub vertical acceleration by detecting a shift in a vertical mode of the one tire. ### Claim 17 (depends on 16) The method of claim 16, further comprising generating a longitudinal stiffness estimation from the first set of vehicle-based vehicle-based input parameters and the set of tire-based input parameters including a vehicle load estimation, the measured air cavity pressure of the one tire, and the measured temperature of the one tire compensated by the wear state estimation of the one tire. ### Claim 18 (depends on 17) The method of claim 17, wherein further comprising making a longitudinal force estimation from the measured wheel speed and the measured wheel torque. ### Claim 19 (depends on 18) The method of claim 18, wherein further comprising using a sliding mode observer model in making the longitudinal force estimation. ### Claim 20 (depends on 13) The method of claim 13, further comprising utilizing a modified sensor fusion algorithm to determine a road surface type analysis using as parameter inputs the road friction estimation, an ambient air temperature measurement, and an ambient air moisture measurement.