# US 11,027,773 B2 · Steer by wire system diagnostic > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,027,773 B2 - Document ID: US11027773B2 - Status: Granted - Kind: B2 - Application number: 16/134,126 - Filed: 2018-09-18 - Published: 2019-03-21 - Granted: 2021-06-08 - Earliest claimed: 2017-09-21 - Assignees: Steering Solutions IP Holding Corporation - Applicants: Steering Solutions IP Holding Corporation - Inventors: Steven D. Klein; Kai Zheng; Scott T. Sanford - Web page: https://patentgrep.com/patent/US11027773B2 ## CPC - B62D 5/0481: {monitoring the steering system, e.g. failures} - B62D 5/001: {Mechanical components or aspects of steer-by-wire systems, not otherwise provided for in this maingroup} - B62D 5/0421: {Electric motor acting on or near steering gear} - B62D 5/0442: {Conversion of rotational into longitudinal movement} - B62D 6/002: {computing target steering angles for front or rear wheels (B62D7/159 takes precedence)} - G07C 5/0808: {Diagnosing performance data (testing of vehicles G01M17/00; testing of electrical installation on vehicles G01R31/005)} - 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) - G07C: TIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE ## Abstract According to one or more embodiments a steer by wire steering system includes a handwheel actuator that provides a commanded position for a rack of a vehicle. The steer by wire steering system further includes a roadwheel actuator that moves the rack to a rack position based on the commanded position from the handwheel actuator. The steer by wire steering system further includes a diagnostic apparatus to compute a reference position based on the commanded position, and to compute a reference tracking error based on a difference between the reference position and the rack position. The diagnostic apparatus further determines a fault condition with the steer by wire system using the reference tracking error. ## Claims ### Claim 1 A steer by wire steering system comprising: a handwheel actuator that provides a commanded position for a rack of a vehicle; a roadwheel actuator that moves the rack to a rack position based on the commanded position from the handwheel actuator; and a processor configured to: compute a reference position based on the commanded position; compute a reference tracking error based on a difference between the reference position and the rack position; and determine a fault condition with the steer by wire system using the reference tracking error. ### Claim 2 (depends on 1) The steer by wire steering system of claim 1, wherein the processor computes the reference position by limiting the commanded position using a rack velocity capability. ### Claim 3 (depends on 2) The steer by wire steering system of claim 2, wherein the processor computes the rack velocity capability using a rack force. ### Claim 4 (depends on 2) The steer by wire steering system of claim 2, wherein the processor computes the rack velocity capability using a motor torque of a motor of the roadwheel actuator. ### Claim 5 (depends on 4) The steer by wire steering system of claim 4, wherein the rack velocity capability is computed using a non-linear relationship between the motor velocity and the motor torque. ### Claim 6 (depends on 4) The steer by wire steering system of claim 4, wherein the processor limits the commanded position to compute the reference position when the rack velocity caused by the commanded position exceeds the rack velocity capability. ### Claim 7 (depends on 1) The steer by wire steering system of claim 1, wherein the processor determines the fault condition in response to the reference tracking error exceeding a predetermined threshold. ### Claim 8 A method for performing a diagnostic for a steer by wire steering system, the method comprising: sending, by a handwheel actuator, a commanded position for receipt by a roadwheel actuator; positioning, by the roadwheel actuator, a rack to a rack position based on the commanded position; computing, by a processor, a reference position based on the commanded position; computing, by the processor, a reference tracking error based on a difference between the reference position and the rack position; and determining, by the processor, a fault condition with the steer by wire system using the reference tracking error. ### Claim 9 (depends on 8) The method of claim 8, wherein the processor computes the reference position by limiting the commanded position using a rack velocity capability. ### Claim 10 (depends on 9) The method of claim 9, wherein the processor computes the rack velocity capability using a rack force. ### Claim 11 (depends on 9) The method of claim 9, wherein the processor computes the rack velocity capability using a motor torque of a motor of the roadwheel actuator. ### Claim 12 (depends on 11) The method of claim 11, wherein the rack velocity capability is computed using a non-linear relationship between the motor velocity and the motor torque. ### Claim 13 (depends on 11) The method of claim 11, wherein the processor limits the commanded position to compute the reference position when the rack velocity caused by the commanded position exceeds the rack velocity capability. ### Claim 14 (depends on 8) The method of claim 8, wherein the processor determines the fault condition in response to the reference tracking error exceeding a predetermined threshold. ### Claim 15 A computer program product comprising a memory storage device having computer executable instructions stored therein, the computer executable instructions when executed by one or more processing units cause the processing units to perform diagnostic of a steer by wire steering system, performing the diagnostic comprising: positioning, by a roadwheel actuator, a rack to a rack position based on a commanded position from a handwheel actuator; computing a reference position based on the commanded position; computing a reference tracking error based on a difference between the reference position and the rack position; and determining a fault condition with the steer by wire system using the reference tracking error. ### Claim 16 (depends on 15) The computer program product of claim 15, wherein the reference position is computed by limiting the commanded position using a rack velocity capability. ### Claim 17 (depends on 16) The computer program product of claim 16, wherein the rack velocity capability is computed using a rack force. ### Claim 18 (depends on 16) The computer program product of claim 16, wherein the rack velocity capability is computed using a motor torque of a motor of the roadwheel actuator. ### Claim 19 (depends on 16) The computer program product of claim 16, wherein the commanded position is limited to compute the reference position when the rack velocity caused by the commanded position exceeds the rack velocity capability. ### Claim 20 (depends on 19) The computer program product of claim 19, wherein the fault condition is determined in response to the reference tracking error exceeding a predetermined threshold.