Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2001-03-13
2002-12-24
Cuchlinski, Jr., William A. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S042000, C180S193000, C340S008100
Reexamination Certificate
active
06498971
ABSTRACT:
TECHNICAL FIELD
The technical field of this invention is the determination of a steer angle of a motor vehicle with a steer angle sensor.
BACKGROUND OF THE INVENTION
The use of steer angle sensors on motor vehicles is increasing due to their use in vehicle dynamic stability systems, steering control systems and other systems requiring a knowledge of vehicle steer angle. Most practical high resolution steer angle sensors are incorporated on the vehicle steer column to detect rotation of the column.
One such sensor is a digital pulse generator such as that described in U.S. Pat. No. 5,857,160 to Dickinson et al, issued Jan. 5, 1999, as well as many other patents and published documents. This type of sensor outputs pulses corresponding to rotations of the shaft through predetermined angles, with some method of determining the direction of the rotation. These pulses are used to increment a counter in a first direction for one rotational direction and a second and opposite direction for the opposite rotational direction. Such sensors generally provide a relative rotational position only, with no inherent absolute rotational position of the shaft; and they do not generally inherently provide a roll-over signal for multiple rotations. Although the counter contents of a sensor that has been initialized and synchronized may be saved in a non-volatile memory for use when the vehicle is next started, this value is not fully trustworthy due to the fact that the steer angle could have been changed between periods of vehicle use when the change was not detected. Thus, such a sensor must generally be recalibrated at the beginning of each vehicle driving cycle before it will indicate true steer angle. The aforementioned U.S. Pat. No. 5,857,160 describes a method incorporating such a recalibrating or centering function responsive to vehicle yaw rate. But the centering methods described in this patent and others require time to complete, during which systems dependent on a steer angle sensor output are generally not activated.
Another type of steer angle sensor in use on motor vehicles provides an indicated position output. An example is a dual track, resistive sensor. It includes two brushes maintaining a fixed 90 degree separation as they rotate in contact with and relative to a circular, electrically resistive track provided with a fixed DC voltage across opposite diagonal points on the track. The output signals from the sensor are two voltages varying with shaft rotational position but maintaining a fixed 90 degree relationship with each other. Such signals provide an indicated rotational position of the shaft within a range of 360 rotational degrees, as well as rotational direction, that offers the opportunity to modify the method described in the aforementioned U.S. Pat. No. 5, 857,160 to provide quicker centering of the sensor, in most cases without full recalibration.
SUMMARY OF THE INVENTION
The apparatus of the invention provides an accurate centered steering angle signal from a steering angle sensor providing an output signal indicating relative position within a full rotation, such as a relative dual track steering sensor. The apparatus performs a two step process in which the sensor output signal is initialized in the first step and verified in the second step.
The apparatus includes a non-volatile memory for storing retained values of a centered vehicle steer angle, a rotation count and a mounting bias angle and digital and digital processing means responsive to an activating signal to perform the following steps:
(a) deriving three test steer angle values as the sum of the retained value of a mounting bias angle, a value derived from the steer angle signal and a rotation angle derived from, respectively for the three test steer angle values, (1) the retained rotation count, (2) one greater than the retained rotation count and (3) one less than the retained rotation count;
(b) choosing as an initialized steer angle one of the three test steer angles that differs from the retained value of a centered vehicle steer angle by less than a first calibration value; and
(c) verifying that the initialized steer angle chosen in step (b) differs from an estimated steer angle derived in response to signals from the vehicle yaw rate sensor and lateral acceleration sensor in a first process by less than a second calibration value less than the first calibration value and, if so, accepting the verified initialized steer angle as the centered vehicle steer angle.
Preferably, the first calibrated value is 180 rotational degrees, so that the initialized steering angle value may be assumed to be within the same rotation as the centered angle. The second step is thus only a verification of the initialization results and thus provides the benefits of quicker centering of the sensor as compared with the full recalibration process, which does not use the retained values from the non-volatile memory. The recalibration process is preferably retained as a backup in case an initialized and verified steer angle is not found in steps (a) through (c).
REFERENCES:
patent: 4633214 (1986-12-01), Miyata et al.
patent: 4856607 (1989-08-01), Sueshige et al.
patent: 5790966 (1998-08-01), Madau et al.
patent: 5857160 (1999-01-01), Dickenson et al.
Delphi Technologies Inc.
Donnelly Arthur D.
Sigler Robert M.
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