Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
1999-01-05
2001-01-09
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C180S422000
Reexamination Certificate
active
06173223
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to power steering for motor vehicles, and, more particularly, to steering control systems for varying the amount of steering assist provided.
BACKGROUND OF THE INVENTION
The amount of force output required by a steering system is proportional to the lateral load on the front axle. At speed, the lateral load is generated primarily by the lateral acceleration of the vehicle. The force output of the power steering system is generated by the assist pressure and force input by the driver. The type of steering maneuver a vehicle is performing can be determined by observing the assist pressure, its change with time, the rate at which the steering wheel is being turned and the vehicle speed. With this information a variable assist power steering system can provide the optimum input force to output force relationship for a given steering maneuver. Unfortunately, conventional variable assist power steering systems do not take full advantage of this information as input to the electronic control module. The result has been power steering systems that are slow to provide adequate flow during certain steering maneuvers, resulting in a perceptable increase in effort for a short period of time. For instance, to avoid this, some steering systems provide surplus flow at the pump and then limit the hydraulic flow at the valve. This results in greater parasitic losses of the vehicles engine possibly leading to a decrease in potential fuel economy. Accordingly, it will be appreciated that it would be highly desirable to have a power steering system that more efficiently uses the available control inputs to more optimally deliver variable power steering assist while maintaining smooth steering assist, even during dynamic steering actuation.
SUMMARY OF THE INVENTION
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a method for providing variable assist power steering by controlling a flow control valve actuator for varying steering assist fluid flow in a power steering system for a vehicle, comprises the steps of: sensing vehicle speed; sensing steering wheel rate; sensing actual actuator current; setting up a first calibration table containing entries representing base actuator current values for given vehicle speeds; setting up a second calibration table containing entries representing evasive actuator current values for given vehicle speeds; selecting a base actuator current from said first calibration table as a function of vehicle speed and producing a base desired current value; selecting an evasive actuator current from said second calibration table as a function of vehicle speed and producing an evasive desired current value; defining a plurality of steering wheel rate ranges; selecting a steering wheel rate range as a function of steering wheel rate; selecting a formula from a plurality of formulas for calculating a final desired current value as a function of steering wheel rate range; calculating said final desired current value using said selected formula; computing flow control valve actuator commands using said final desired current value and generating an output PWM voltage signal; and outputting said PWM voltage signal to said flow control valve actuator to vary steering assist.
These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.
REFERENCES:
patent: 4621833 (1986-11-01), Soltis
patent: 4666011 (1987-05-01), Ohe et al.
patent: 4715461 (1987-12-01), Shimizu
patent: 4715463 (1987-12-01), Shimizu
patent: 4800974 (1989-01-01), Wand et al.
patent: 4819170 (1989-04-01), Shimizu et al.
patent: 4828065 (1989-05-01), Ishihara et al.
patent: 5029660 (1991-07-01), Raad et al.
patent: 5201818 (1993-04-01), Nishimoto
patent: 5257828 (1993-11-01), Miller et al.
patent: 5265019 (1993-11-01), Hararra et al.
patent: 5475289 (1995-12-01), McLaughlin et al.
patent: 5513720 (1996-05-01), Yamamoto et al.
patent: 5528497 (1996-06-01), Yamamoto et al.
patent: 5553683 (1996-09-01), Wenzel et al.
patent: 5568389 (1996-10-01), McLaughlin et al.
patent: 5623409 (1997-04-01), Miller
patent: 5709281 (1998-01-01), Sherwin et al.
patent: 5711394 (1998-01-01), Fujii et al.
patent: 5743351 (1998-04-01), McLaughlin
patent: 5749431 (1998-05-01), Peterson
Baraszu Robert Charles
Collins Ronald Joseph
Liubakka Michael Kenneth
Brown Gregory P.
Cuchlinski Jr. William A.
Ford Global Technologies Inc.
Pipala Edward
LandOfFree
Steering control method for providing variable assist power... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Steering control method for providing variable assist power..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Steering control method for providing variable assist power... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2445360