Optics: measuring and testing – Angle measuring or angular axial alignment – Wheel alignment with photodetection
Reexamination Certificate
2001-08-31
2004-02-10
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Angle measuring or angular axial alignment
Wheel alignment with photodetection
C033S203180
Reexamination Certificate
active
06690456
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a wheel alignment apparatus having measurement heads for determining wheel positions of wheels of a motor vehicle wherein each measurement head comprises at least one camera which is the direct to a measurement target arranged in the field of view of the camera and positioned in a well defined relationship to the wheel of the motor vehicle, and wherein pictures taken by the camera are evaluated by an evaluation unit in order to determine the spatial position of the measurement target and, thereby, of the wheel with respect to the position of the camera and the measurement head respectively.
Such so called contact free wheel alignment apparatus are for example known from EP 0895056, EP 0943890 and DE 19757763 A1. In such wheel alignment apparatus, the measuring heads which serve for determining the wheel positions of the wheels of the motor vehicle on a measurement site, have to be adjusted with respect to each other prior to the actual measurement, and this imposes problems in practice.
In the wheel alignment apparatus known form EP 0895056, the adjustment of the measuring heads with respect to each other is carried out in that the measurement heads are arranged on a common frame on the measuring site such that the relative position of the measurement heads with respect to each other is known. The measurement heads are, however, moveably guided such that accuracy problems arise at the guiding means. Such an arrangement has the deficiency that the distances from the measurement heads to the measurement targets are quite wide such that the resolution of the camera imposes a problem.
In the wheel alignment apparatus known from EP 0943890, the positioning of the measurement heads with respect to each other is carried out in that reference targets are arranged on the measurement site by means of which reference targets the measurement heads are adjusted or positioned with respect to each other. Since the reference targets are arranged on the measurement site in front of the vehicle, the distances from the reference targets to the measurement heads at the real wheels is quite long so that it is difficult to a achieve the required accuracy in calibrating the measurement heads.
In the wheel alignment apparatus known from DE 19757763 A1, the positioning of the measurement heads with respect to each other is carried out in that a separate frame with reference targets is arranged between the measurement heads and the vehicle, where the calibration of the measurement heads is carried out with the aid of the reference targets. In this case, the frame with the reference targets interferes with the installation of the apparatus and during the measurement procedure.
It has already been tried to use the measurement cameras themselves for calibrating the measurement heads, and to arrange reference targets on the measurement heads positioned obliquely opposite to each other with respect to the driving direction of the vehicle. In this case, there is the problem that the camera which serves for carrying out the measurement with respect to the position of the wheel opposite to the camera as well as for calibrating the relative position of the two measurement heads opposite to each other, has to be calibrated twice during each measurement run because of the required changes in the focal length of the camera. If such a camera is also used to provide the relationship to the diagonally opposite measurement head, three calibrations of the camera are necessary, and such calibrations are cumbersome.
SUMMARY OF THE INVENTION
In view of there both, it is an object of the invention to provide a wheel alignment apparatus which is designed to operate without a locally fixed reference system and in which the calibration maybe carried out with as few calibration works and hardware components as possible.
For achieving this object, the wheel alignment apparatus of the invention comprises an optical reference system integrated into the measurement heads for calibrating the measurement heads of the wheel alignment apparatus as to the position of the measurement heads with respect to each other. By means of such a references system it is possible in an advantageous way to use mobile measurement heads which are calibrated with respect to the positions to each other prior to the actual measurement.
According to an advantageous embodiment the invention provides a wheel alignment apparatus wherein the references system comprises a reference camera on one of the measurement heads on one side of the motor vehicle and a reference target which is arranged on the opposite measurement head on the same side of the vehicle as well as reference targets on the inside of a forward and a backward measurement head which reference targets are within the fields of view of the measurement cameras of the opposite measurement heads. This arrangement has the advantage that the measurement heads may be freely positioned according to the wheel distance (in driving direction) and the wheel distance transverse to the driving direction, where the measurement targets are positioned in the fields of view of the measurement cameras during the measurement procedure and the measurement and reference targets respectively are positioned in the fields of view of the measurement and reference cameras respectively when no vehicle is present on the measurement site. As compared to a system consisting of the measurement cameras and the measurement targets, only two additional cameras and four reference targets are required. The measurement heads are diagonally exchangeable, and a serf control can be carried out by means of a measurement on the bases of the measurement heads reaching completely around the vehicle. For calibrating purposes, the vehicle has to be removed from the measurement site.
According to an advantageous embodiment the invention provides a wheel alignment apparatus wherein the references system comprises a reference camera on one of the forward measurement heads and a reference target on the opposite measurement head, where the reference camera and the reference target are arranged in front of the vehicle, and wherein the references system further comprises a reference camera on one of the side measurement heads and a reference target on the opposite measurement head on the same side of the vehicle. Hereby, the advantage is achieved that the measurement heads may be position freely according to the wheel distance in the driving direction of the vehicle and to the wheel distance transversely to the driving direction of the vehicle as long as they my detect each other within their respective fields of view. Only three references cameras and targets are required in order to put up the reference system.
According to an advantageous embodiment the invention provides a wheel alignment apparatus wherein, furthermore, a reference camera is arranged on one of the back measurement heads and a reference target is arranged on the opposite measurement head. Herein, it is advantagoues that the measurement heads may be freely positioned according to the wheel distance in driving direction of the vehicle and the wheel distance transverse to the driving direction of the vehicle as long as they may detect each other within their respective fields of view. The measurement heads are diagonally exchangeable, and self-control of the wheel alignment apparatus is possible by means of the references system which completely surrounding the vehicle as it is the case with the so called eight-sensor wheel alignment apparatus.
According to an advantageous embodiment the invention provides a wheel alignment apparatus comprising an optical beam splitter or mirror system which is arranged between a reference target each and a measurement camera each such alive the reference targets are with in the field of side of the measurement camera. Since, by means of this arrangement, reference cameras are replaced by an optical beam splitter or mirror system, this arrangement has the advantage that a reference camera is save
Bux Herrmann
Käfer Stefan
Schommer Stefan
Beissbarth GmbH
Buczinski Stephen C.
LandOfFree
Wheel alignment apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wheel alignment apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wheel alignment apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3285880