Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-01-14
2001-10-16
Lee, Benjamin C. (Department: 2736)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S686100, C340S671000, C340S672000, C250S231180, C250S23700G, C702S151000
Reexamination Certificate
active
06304190
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to optoelectronic steering angle detection methods and systems. The present invention particularly relates to a method of determining the angular position of the steering wheel of a motor vehicle using an optoelectronic steering angle sensor in which a transparent code trace of a code transmitter images light traces of a light source onto the photosensitive surface of a line sensor such that bright-dark light transitions of the light traces extend over image points of the line sensor for enabling the determination of the angular position of the steering wheel as a function of the bright-dark light transitions.
Furthermore, the present invention particularly relates to an optoelectronic steering angle sensor for determining the angular position of the steering wheel of a motor vehicle having a code transmitter operable to be moved relative to a line sensor by the rotational movement of the steering wheel in which a code trace of the code transmitter images light traces of a light source onto the line sensor for enabling the determination of the angular position of the steering wheel as a function of the light traces imaged onto the line sensor.
BACKGROUND ART
The steering angle or steering angle lock values in motor vehicles influences a driving dynamics control system. In addition to the steering angle values, a driving dynamics control system obtains further measurement data such as the wheel rotational speed or the rotation of the motor vehicle about its vertical axis. The absolute steering angle lock and the steering rate are required so that these values can be evaluated together with the other detected data by the driving dynamics control system. All the data can then be converted for controlling actuators such as brakes and for managing the engine.
An optoelectronic steering angle sensor is disclosed, for example, in DE 40 22 837 A1. The disclosed steering angle sensor includes a light source and a line sensor arranged in parallel and spaced apart from each other and an encoder disc (code transmitter) disposed between the light source and the line sensor. The encoder disc is non-rotatable connected to the steering spindle. The line sensor is a CCD-sensor line. The code transmitter is a light slit disc and includes as a code trace a spiral which increases in size from the inside outwards. From the exposure of the image points of the line sensor in the case of a specific steering lock it is possible to obtain information regarding the actual steering angle lock.
In order that the steering angle data obtained can be used for further processing as an input variable of a driving dynamics control system the data must be highly accurate and have the highest possible resolution. These desired requirements cannot be met by the steering angle sensor or the method which are disclosed in DE 40 22 837 A1. Because the encoder disc is non-rotatable disposed on the steering spindle and the line sensor is fixed in position with respect to the rotational movement of the encoder disc and is thus not attached to the steering spindle, any movements of the steering spindle causing it to move in directions perpendicular to the longitudinal axis are detected as a change in the steering angle lock by the corresponding movement of the encoder disc and the associated movement of the code trace imaged on the line sensor. Accordingly, the driving dynamics control system is also influenced with this type of incorrect information.
The measurement accuracy of the previously known steering angle sensor is determined by the accuracy and the fineness of the code trace and by the imaging sharpness of the light trace of the encoder disc on the line sensor. In order to achieve the most effective imaging sharpness the previously known steering angle sensor uses an elongated light source such as a line-source LED or a longitudinal light source. The length of these light sources corresponds to the length of the sensor line. The emitted light beams impinge upon the surface of the code transmitter at right angles where possible. This feature is intended to achieve the most discrete bright-dark light transition possible in order to be able to exactly determine the light trace on the line sensor. These demands require the encoder disc to be assembled and adjusted precisely with respect to the light source and the line sensor. The resolution which can be achieved even when using a highly accurate code trace corresponds to the physical resolution of the line sensor. Consequently, the resolution of this type of steering angle sensor can be increased merely by using a line sensor with an extremely high number of image points and a code trace having an extremely precise line. However, these features require considerable outlay and place high demands upon the tolerances which are to be maintained.
SUMMARY OF THE INVENTION
On the basis of this discussed prior art, it is therefore an object of the present invention to provide a method of determining the absolute angle position of the steering wheel of a motor vehicle within a segment of 360° precisely and with high resolution. Furthermore, it is the object of the present invention to provide an optoelectronic steering angle sensor which uses common components configured to meet strict resolution requirements.
The method related object is achieved because a scanning line and a reference line are radiated as the code trace by a light source and the scanning line and the reference line light traces are imaged on the photosensitive surface of the line sensor such that bright-dark light transitions extend over image points (pixels) of the line sensor to enable the determination of the angular position of the steering wheel. The angular position is determined by ascertaining accurately in subpixels the distance between corresponding characteristics of the signal clusters of the scanning light trace and the reference light trace as detected by the line sensor. The distance is used as a measure of the absolute angle position of the steering wheel.
The device related object is achieved because the code trace of the code transmitter includes a scanning line and a reference line and the scanning line and the reference line light traces as produced by exposing the code transmitter to light include when imaged on the line sensor a lack of sharpness extending over image points (pixels) in the bright-dark light transition between the bright regions of the light traces and the adjacent dark regions to enable an evaluating unit to ascertain in subpixels the distance between corresponding characteristics of the signal clusters of the scanning light trace and the reference light trace as detected by the line sensor. The distance is used as a measure of the absolute angle position of the steering wheel.
In contrast to the prior art, the steering angle sensor in accordance with the present invention uses the lack of sharpness of the bright-dark light transitions extending over several image points (pixels) of the detected code traces for determining the actual or approximate position of edges of the light traces. This feature has the advantage that only small demands are placed upon the component arrangement and upon the light source. It is prudent to provide a bright-dark light transition region extending over a plurality of image points in order for the discrete signals of the image points radiated by the code trace and designated hereinunder as the signal cluster to use a specific characteristic for determining the steering angle.
In accordance with the present invention, the code transmitter has a scanning line and a reference line. The distance between the scanning line and the reference line is different in each point in the 360° segment for detecting the steering angle. Therefore, the distance at each point between identical characteristics of the signal clusters of the scanning light trace and the reference light trace can be used for determining the absolute steering angle. By determining the distance the steering angle is deter
Brooks & Kushman P.C.
Lee Benjamin C.
Leopold Kostal GmbH & Co. KG
LandOfFree
Method for determining the absolute angular position of the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for determining the absolute angular position of the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for determining the absolute angular position of the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2612245