# US 11,299,198 B2 · Method for determining the track rod force modeling the torsional elastic release of the tyre in order to manage transitions between park and drive > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,299,198 B2 - Document ID: US11299198B2 - Status: Granted - Kind: B2 - Application number: 16/611,736 - Filed: 2018-05-15 - Published: 2020-04-02 - Granted: 2022-04-12 - Earliest claimed: 2017-05-23 - Assignees: Jtekt Europe - Applicants: Jtekt Europe - Inventors: Sébastien Bourdrez; Pierre Dupraz; Serge Gaudin; Pascal Moulaire; Kazusa Yamamoto - Web page: https://patentgrep.com/patent/US11299198B2 ## CPC - B62D 6/008: {Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications} - B62D 5/0463: {calculating assisting torque from the motor based on driver input} - B62D 5/0472: {for damping vibrations} - B60T 2260/02: Active Steering, Steer-by-Wire - B60W 2510/20: Steering systems - B60W 2520/14: Yaw - B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M) - 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 ## Abstract A method estimates a track rod force which is exerted, in a power steering system with which a vehicle is equipped, on a track rod belonging to a steering mechanism which connects an actuator to a steered wheel which is orientable in the yaw direction and which bears a tyre of which the tread is in contact with the ground, the value of the estimated track rod force being corrected as a function of the longitudinal speed of the vehicle by a force component that models the release of the elastic torsion of the tyre so as to reduce, the estimated track rod force according to the longitudinal speed of the vehicle, when the vehicle transitions from a park situation in which the longitudinal speed of the vehicle is zero to a drive situation in which the longitudinal speed of the vehicle is non-zero. ## Claims ### Claim 1 A method of evaluating an actuation force on a transmission member that is called force at tie rods when a vehicle transitions from a parking situation to a running situation, comprising: transitioning the vehicle from the parking situation to the running situation; and evaluating the force at the tie rods by a process comprising: initially estimating a value for the force at the tie rods to obtain an estimated value for the force at the tie rods; and correcting the estimated value for the force at the tie rods by reducing said estimated value, in absolute value, according to a longitudinal velocity of the vehicle (V_vehic) when the vehicle transitions from the parking situation, in which the longitudinal velocity of the vehicle (V_vehic) is zero, to the running situation, in which the longitudinal velocity of the vehicle (V_vehic) is non-zero, wherein: the vehicle is equipped with a power steering system comprising a steering mechanism that connects an actuator to a steered wheel that is orientable in yaw; the steered wheel carries a tire with a tread that is in contact with a ground; and the steering mechanism comprises the transmission member on which the actuation force is evaluated. ### Claim 2 (depends on 1) The method according to claim 1, wherein the force at the tie rods is evaluated from a model using: a first force component (F1) that is representative of a yaw elastic torsion of the tire corresponding to a position deviation (Δx) between on the one hand a position (XCR) imparted to the transmission member by the power steering system and on the other hand a position (XBR) of the tread of the tire which is retained, against displacements of the transmission member, by a friction resistant force (Frot, kc) that the ground exerts on the tread of the tire, and a second force component (F2) that attenuates the first force component (F1), according to the longitudinal velocity of the vehicle (V_vehic), as soon as the vehicle adopts a non-zero longitudinal speed, so as to take into consideration a progressive release of the yaw elastic torsion of the tire during the transition between the parking situation, where the longitudinal velocity of the vehicle is zero, and the running situation, where the longitudinal velocity of the vehicle is non-zero. ### Claim 3 (depends on 2) The method according to claim 2, wherein the first force component (F1) is modeled by means of a first stiffness coefficient (kt), representative of a torsional stiffness of the tire, which is multiplied by the position deviation (Δx) between the transmission member and the tread of the tire: F1=kt*Δx. ### Claim 4 (depends on 2) The method according to claim 2, wherein the second force component (F2) is modeled by means of a second coefficient (kd) multiplied by the longitudinal velocity of the vehicle (V_vehic) and by the position deviation (Δx) between the transmission member and the tread of the tire: F2=kd*V_vehic*Δx. ### Claim 5 (depends on 4) The method according to claim 4, wherein the second force component (F2) is calculated from the longitudinal velocity of the vehicle (V_vehic) and from a static friction value (Frot) that is representative of a friction force between the tread and the ground, in slip limit, which must be overcome by an action of the transmission member to cause, when the vehicle is stopped, a yaw displacement of the tread of the tire on the ground. ### Claim 6 (depends on 5) The method according to claim 5, wherein the force at the tie rods is calculated from a first-order term relative to the longitudinal velocity of the vehicle (V_vehic) and equal to Frot 1 + K d · V_vehic k t . ### Claim 7 (depends on 5) The method according to claim 5, wherein the second coefficient (kd) is adjusted according to the static friction value (Frot). ### Claim 8 (depends on 5) The method according to claim 5, wherein the static friction value (Frot) is adjusted according to parameters specific to the vehicle or to an environment of the vehicle and which modify an adhesion of the tire on the ground. ### Claim 9 (depends on 4) The method according to claim 4, wherein the second coefficient (kd) is adjusted according to the longitudinal velocity of the vehicle (V_vehic). ### Claim 10 (depends on 2) The method according to claim 2, wherein the model allowing evaluation of the force at the tie rods additionally uses a third force component (F3), which depends on the position (XCR) of the transmission member, in order to model effects of lift-up of the vehicle during yaw steering of the steered wheel. ### Claim 11 (depends on 10) The method according to claim 10, wherein the third force component (F3) is calculated from a second-degree polynomial comprising a linear term and a quadratic term relative to the position (XCR) of the transmission member: F3=kf1*XCR+kf2*XCR2. ### Claim 12 (depends on 11) The method according to claim 11, wherein the coefficients (kf1, kf2) of the second-degree polynomial are adjusted according to the longitudinal velocity of the vehicle (V_vehic). ### Claim 13 (depends on 1) The method according to claim 1, wherein the force at the tie rods is representative of a force exerted by the transmission member formed by a steering tie rod on one end of a rack that is movably mounted relative to a frame of the vehicle, and the steering tie rod connects to the steered wheel, and the force at the tie rods is evaluated from the longitudinal velocity of the vehicle (V_vehic) and the position of the rack (XCR) considered as a representative position of the transmission member.