Source: http://www.google.com/patents/US7725227?dq=No.+6,411,949
Timestamp: 2014-10-20 05:28:37
Document Index: 613683498

Matched Legal Cases: ['art 1', 'Application No. 09003760', 'Application No. 07121593', 'Application No. 07075579', 'Application No. 07075577', 'art 1']

Patent US7725227 - Method, system, and apparatus for providing enhanced steering pull compensation - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA method, system, and apparatus for providing enhanced steering pull compensation are provided. The method compensates for steering pull in a vehicle steering system that includes a handwheel. The method includes monitoring the vehicle to determine whether the vehicle is heading forward along a substantially...http://www.google.com/patents/US7725227?utm_source=gb-gplus-sharePatent US7725227 - Method, system, and apparatus for providing enhanced steering pull compensationAdvanced Patent SearchPublication numberUS7725227 B2Publication typeGrantApplication numberUS 11/611,406Publication dateMay 25, 2010Filing dateDec 15, 2006Priority dateDec 15, 2006Fee statusPaidAlso published asEP1932745A2, EP1932745A3, EP1932745B1, EP2070803A1, EP2070803B1, EP2070803B8, US20080147276, US20090030575Publication number11611406, 611406, US 7725227 B2, US 7725227B2, US-B2-7725227, US7725227 B2, US7725227B2InventorsKathryn L. Pattok, Terrence D. Smith, Ashok Chandy, Julie A. Kleinau, Jeff Zuraski, Mark P. Colosky, Troy P. StrieterOriginal AssigneeGm Global Technology Operations, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (118), Non-Patent Citations (22), Referenced by (14), Classifications (13), Legal Events (7) External Links: USPTO, USPTO Assignment, EspacenetMethod, system, and apparatus for providing enhanced steering pull compensationUS 7725227 B2Abstract A method, system, and apparatus for providing enhanced steering pull compensation are provided. The method compensates for steering pull in a vehicle steering system that includes a handwheel. The method includes monitoring the vehicle to determine whether the vehicle is heading forward along a substantially linear straight-ahead path and, if so, measuring handwheel torque, as a sensed torque signal, to determine an amount of steering pull existing at the handwheel. The method also includes generating a torque assist signal in response to the sensed torque signal and calculating an offset signal for reducing the amount of steering pull to substantially zero. The method further includes producing a modified torque assist signal by adding the offset signal to the torque assist signal, and applying the modified torque assist signal to the vehicle steering system.
BACKGROUND In a vehicle equipped with an electric power steering (�EPS�) system, steering assist torque is provided by an electric motor coupled to a steering column or shaft. A steering wheel or handwheel is also typically coupled to the steering column or shaft in order for a driver to steer the vehicle. When the driver wants to travel substantially straight ahead along a linear path, the handwheel is rotated to a generally centered neutral position which does not cause a change in the direction of travel. However, due to mechanical tolerances and other factors, the handwheel may need to be rotated somewhat away from center to maintain the vehicle's heading along a substantially linear, straight-ahead path.
Under such off-center conditions, the driver may or may not need to provide any input torque in order to keep the hand-wheel at a neutral position which provides a straight direction of travel, depending on whether there is any torque coming from the steering system that tends to rotate the hand-wheel clockwise or counterclockwise. In situations where the hand-wheel must be pulled slightly in one direction to maintain a substantially straight course, the driver must exert some force to prevent the vehicle from deviating from the intended path. This phenomenon, commonly known as �steering pull�, can be caused by many factors such as, for example, camber or caster misalignment at the front end, tire properties of ply steer or conicity, air pressure differentials between left and right tires, road surfaces that are not level, crowned pavement, and prevailing wind.
SUMMARY The above described and other features are exemplified by the following Figures and Description in which a method is provided to compensation for steering pull in a vehicle steering system that includes a handwheel. The method includes monitoring the vehicle to determine whether the vehicle is heading forward along a substantially linear straight-ahead path and, if so, measuring handwheel torque, as a sensed torque signal, to determine an amount of steering pull existing at the handwheel. The method also includes generating a torque assist signal in response to the sensed torque signal and calculating an offset signal for reducing the amount of steering pull to substantially zero. The method further includes producing a modified torque assist signal by adding the offset signal to the torque assist signal, and applying the modified torque assist signal to the vehicle steering system.
DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral 10 generally designates an electric power steering (�EPS�) system for a motor vehicle. A steering mechanism 12 is a rack-and-pinion type mechanism that includes a toothed rack (not shown) and a pinion gear (also not shown) located under a gear housing 14. A handwheel 16 is coupled to an upper steering shaft 18. As handwheel 16 is turned, upper steering shaft 18, which is connected to a lower steering shaft 20 through a universal joint 22, turns the pinion gear. Rotation of the pinion gear moves the toothed rack, which moves tie-rods 24 (only one shown) that, in turn, move steering knuckles 26 (only one shown), which turn wheels 28 (only one shown).
As shown in FIG. 2, an EPS control algorithm is indicated generally by the reference numeral 50, which algorithm is implemented by the controller 32 of FIG. 1. The EPS control algorithm 50 includes a steering pull compensator 52. The EPS control algorithm 50 receives a signal indicative of the torque applied to the pinion gear at a non-inverting input of a summing function 54, which generates an applied torque signal indicative of the torque applied to handwheel 16 (FIG. 1) by a vehicle operator. A torque assist function 56 depicted as �electronic power steering� as known to those of ordinary skill in the pertinent art, receives the applied torque signal and produces a signal indicative of the desired assist torque. A summing function 58 receives the assist torque signal at a non-inverting input, and generates a signal to be subtracted from the pinion torque at an inverting input of summing function 54.
If the straight ahead conditions are not met, then the output of first conditional lowpass filter 121, also termed �short term bias�, is held to its previous value.
The system of FIG. 10 does not require any �learning� of a steering pull condition. This system may be advantageously exploited in situations where it is desired to null out an existing steering pull condition. This might be diagnosed and compensated for during vehicle assembly or service, via vehicle evaluation or rolling alignment. The correction could be scaled with vehicle speed, as is shown in the illustrative example of FIG. 10, but scaling the correction with vehicle speed is not necessary.
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Classification701/41, 180/443International ClassificationA01B69/00, B62D6/00, B62D5/04, B63G8/20, B62D11/00, G05D1/00, B62D12/00Cooperative ClassificationB62D6/04, B62D5/0472European ClassificationB62D6/04, B62D5/04P2HLegal EventsDateCodeEventDescriptionNov 25, 2013FPAYFee paymentYear of fee payment: 4Mar 15, 2012ASAssignmentFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:PACIFIC CENTURY MOTORS, INC.;NEXTEER (BEIJING) TECHNOLOGY CO., LTD.;REEL/FRAME:027870/0666Effective date: 20120126Owner name: STEERING SOLUTIONS IP HOLDING CORPORATION, MICHIGAJan 10, 2012ASAssignmentFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GM GLOBAL TECHNOLOGY OPERATIONS, INC.;REEL/FRAME:027842/0918Owner name: PACIFIC CENTURY MOTORS, INC., CHINAEffective date: 20101130Owner name: GM GLOBAL TECHNOLOGY OPERATIONS, INC., MICHIGANNov 22, 2010ASAssignmentFree format text: RELEASE BY SECURED PARTY;ASSIGNOR:UAW RETIREE MEDICAL BENEFITS TRUST;REEL/FRAME:025386/0503Effective date: 20101026Owner 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