Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
1999-12-28
2001-04-17
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S042000, C180S422000, C180S443000, C180S446000
Reexamination Certificate
active
06219604
ABSTRACT:
STATE OF THE ART
The invention is based on a steer-by-wire steering system for motorized vehicles having an electronically controlled steering positioner mounted to the steering gear of the front axle or to both of the steerable front wheels, a steering wheel sensor which picks up the desired driving direction at the steering wheel and transmits the road feel to the driver via the steering wheel by means of a feedback actuator unit.
Such a steer-by-wire steering system for motorized vehicles is known from DE 195 40 956 C1. This well-known steering system allows the driver to open the otherwise rigid mechanical drive connection between the steering wheel and a drive gear assembly on the vehicle's drive-controlled wheels by means of a clutch. This steering system thus is a steer-by-wire steering system where the steering wheel is only indirectly coupled to the drive gear assembly. To convey the road feel to the driver through the steering wheel, this solution provides for a manual positioner in the form of an anti-lock electric motor which, controlled by an electronic steering device on the steering wheel, effects a controllable actuation resistance.
A further steer-by-wire steering system, known from U.S. Pat. No. 5,347,458, utilizes a steering wheel positioner, which engages the steering wheel shaft, to imprint a reaction energy on the steering wheel which can be expressed as a mathematical function containing an acceleration term that is proportional to the angular acceleration of the steering wheel, a speed term proportional to the angular speed of the steering wheel, a proportional term proportional to the deflection angle of the steering wheel, and a constant term whose value is constant, but whose sign is dependent upon the direction of the deflection of the steering wheel from a neutral position. This reaction energy, which exerts a force on the steering wheel, is designed to provide the driver of the vehicle with an opposing force on the steering wheel, as he is accustomed to experience it from conventional steering systems, but is also intended to increase maneuverability and stability by transmitting information about the operational status of the vehicle to the driver via the steering wheel, allowing the driver to perform the appropriate steering maneuvers. By changing the coefficient—based on the various operational conditions of the vehicle, such as the vehicle speed—of at least one of the above-listed terms with regard to the mathematical function that is representative of the reaction energy, a reaction energy can be produced that is optimum in each special case of application.
OBJECT AND ADVANTAGES OF THE INVENTION
It is the object of the invention to provide a vehicle steering system that no longer features a mechanical or hydraulic coupling between the steering wheel and the steerable vehicle axle, but rather a steer-by-wire steering system capable not only of modifying the driver's desired direction as recorded by the steering wheel sensor while taking the data from the moving vehicle's handling dynamics into account, but which also improves the transverse dynamics by modifying the driver's desired direction, while simultaneously allowing for an individual response to a range of driver demands by adaptively recreating the manual torque relayed by the feedback actuator, thus generating adaptive nominal values for the steering wheel regulator.
The object of the invention is attained as stated in the patent claims. Based on the characteristics listed in the patent claims, the invention creates a steer-by-wire steering system for motorized vehicles which with regard to its functional realization has a flexible structure, is able to increase the steering comfort by a variable, speed-dependent steering angle transmission ratio and improve the transverse dynamics by means of modifications of the driver's desired direction depending on the vehicle's operational conditions, and to make it possible, by the adaptive recreation of the manual torque exerted on the steering wheel via the feedback actuator, to individually adapt to a range of different drivers' requirements, thus obtaining adaptive nominal values for the steering wheel regulator. The steer-by-wire steering system described in this invention makes it possible, for instance, to throttle engine power on poor road surfaces by monitoring the steering positioners' performance, and to provide haptic feedbacks to the driver through the steering wheel when the steering positioner is overloaded, including for instance the following cases:
Changes in the steering counterforce in the presence of slippery road conditions, such as in hydroplaning, icy road surfaces, etc., or dependent on the friction coefficient of the road surface (determined, for example, by the control unit of the antilock brake system);
Changes in the steering counterforce in the presence of skidding or rollover hazards (this data can for instance be relayed by the ESP control unit);
An altered steering counterforce which may be encountered on poor roadways (the signal indicating a poor roadway can for instance be transmitted by the control unit of the antilock brake system);
An alert by a quick jerking of the steering wheel, generated when the vehicle is operated in a faulty manner, such as when the maximum RPM's or the maximum vehicle speed are exceeded.
The above, as well as additional advantageous characteristics described in this invention, will be more closely discussed based on the preferred embodiments of the steer-by-wire steering system described in this invention in the explanatory description supported by drawings.
REFERENCES:
patent: 5247441 (1993-09-01), Serizawa et al.
patent: 5347458 (1994-09-01), Serizawa et al.
patent: 6097286 (2000-08-01), Discenzo
patent: 195 40 956 C1 (1995-11-01), None
Ahner Peter
Allgeier Thorsten
Blessing Peter
Cao Chi-Thuan
Dilger Elmar
Baker & Daniels
Cuchlinski Jr. William A.
Marc-Coleman Marthe Y.
Robert & Bosch GmbH
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