METHOD FOR DETERMINING PARAMETERS OF THE VEHICLE GEOMETRY OF WHEELS OF A NON-ARTICULATED AXIS, USE OF THE METHOD, TEST STAND FOR A VEHICLE AND MEASURING UNIT

Abstract

The present invention relates to a method for determining parameters of the chassis geometry of wheels of a non steered axle, amuse of the method, a test bench for a vehicle, and a measuring unit. The method relates to determining the parameters of the chassis geometry of the Wheels of the rear axle of a vehicle from measurements of the toe angle in two measuring positions of the vehicle in the test bench, which positions are mutually offset in the x-direction. Wheel runout compensation is achieved thereby. The geometric driving axle thus determined can be used for setting driver assistance systems and for setting the parameters of the chassis geometry of the steered wheels of the front axle. A measuring unit can be designed such that a plurality of parallel lines for generating a planar pattern are generated by means of a parallel displacement of a sensor in the x-direction, which sensor emits linear light having one line. A linear sensor of this kind can in turn be replaced by a sensor comprising a point light source by means of which a line is scanned.

Claims

1. Method for determining parameters of the chassis geometry of wheels of a non-steered axle of a vehicle in a test bench, wherein the parameters of the chassis geometry of the wheels of the non-steered axle are ascertained in that, on the non-steered axle, the wheel of each side of the vehicle is associated with one measuring unit, respectively, which measuring unit acquires at least one parameter of the orientation of the relevant wheel plane based on a test bench frame of reference, characterized in that, for a first position of the vehicle in the test bench, at least one parameter (1) of the orientation of a vehicle-related frame of reference relative to the test bench frame of reference is determined in said first position, and in that, in said first position, the measuring units that are assigned to the wheels of the non-steered axle acquire measured values for determining at least one parameter of the orientation of the relevant wheel planes and/or ascertain from said measured values the at least one parameter of the orientation of the relevant wheel planes and/or a value derived therefrom, in that the vehicle is moved into a second position of the vehicle in the test bench, which position is offset, in the longitudinal direction of the vehicle in the test bench, relative to the first position, in that, for the second position of the vehicle in the test bench, the at least one parameter (2) of the orientation of the vehicle-related frame of reference relative to the test bench frame of reference is determined in said second position, and in that, in the second position, the measuring units that are assigned to the wheels of the non-steered axle in said second position acquire measured values for determining the at least one parameter of the orientation of the relevant wheel planes in said second position and/or ascertain the at least one parameter of the orientation of the relevant wheel plane and/or a value derived therefrom, in that the measured values for determining the at least one parameter of the orientation of the relevant wheel planes and/or the at least one parameter of the orientation of the relevant wheel planes that was ascertained from the acquired measured values, and/or the value derived therefrom in the first position and in the second position are converted, taking account of the at least one parameter (1, 2) of the orientation of the vehicle-related frame of reference relative to the test bench frame of reference in the first position and in the second position, such that the converted measured values for determining the at least one parameter of the orientation of the relevant wheel planes and/or the converted at least one parameter of the orientation of the relevant wheel planes that was ascertained from the acquired measured values, and/or the converted value derived therefrom in the first position and in the second position are provided on the basis of a common frame of reference, and in that wheel runout-compensated converted measured values for determining at least one parameter of the orientation of the relevant wheel planes and/or at least one wheel runout-compensated converted parameter of the orientation of the relevant wheel planes and/or a wheel runout-compensated converted value derived therefrom are ascertained, based on the common frame of reference in each case, from the converted measured values for determining at least one parameter of the orientation of the relevant wheel planes and/or the converted at least one parameter of the orientation of the relevant wheel planes and/or the converted value derived therefrom in the first position and in the second position, in the common frame of reference in each case, taking account of the spacing of the first position from the second position in the x-direction and the diameter of the wheels of the non-steered axle.

2. Use of the method according to claim 1 in a vehicle setting bench for measuring and setting driver assistance systems, wherein the driver assistance systems are adjusted to the geometric driving axle of the vehicle setting bench that was ascertained using the method according to claim 1.

3. Use of the method according to claim 1 in a chassis setting bench for measuring and setting parameters of the chassis geometry at wheels of a steered axle of the vehicle, wherein the vehicle further comprises at least one non-steered axle, wherein the chassis setting bench comprises one wheel fixture, respectively, for the wheels of the steered axle of the vehicle on the right-hand and on the left-hand side of the vehicle, wherein the wheel fixture in each case consists of a floating plate and a double roller, wherein at least one roller of the double rollers is drivable, wherein the geometric driving axle is ascertained using the method according to claim 1.

4. Measuring, test and/or setting bench for vehicles, wherein the vehicle comprises at least one non-steered axle, characterized in that, in order to measure the driving axle of the vehicle, the test bench has just two measuring positions in the x-direction, in each of which positions one measuring unit is provided for each wheel of a non-steered axle of the right-hand and left-hand side of the vehicle, wherein the measuring units acquire measured values for determining at least one parameter of the orientation of the wheel plane of the relevant wheel, wherein an evaluation unit is furthermore provided, to which evaluation unit the measured values of the measuring units are supplied and in which evaluation unit the geometric driving axle is ascertained.

5. Measuring, test and/or setting bench according to claim 4, characterized in that the measuring, test and/or setting bench is a chassis setting bench for measuring and setting parameters of the chassis geometry of wheels of the steered axle of the vehicle, wherein the measuring, test and/or setting bench comprises one Wheel fixture, respectively, for the wheels of the steered axle of the vehicle on the right-hand and on the left-hand side of the vehicle, wherein the wheel fixture consists in each case of a floating plate and a double roller, wherein at least one of the double rollers is assigned a drive element in each case, for transferring a driving or braking torque to the at least one roller, wherein the wheels of the steered axle are positioned on the relevant wheel fixture while the measuring, testing and or setting work is being carried out, characterized in that, in order to measure the driving axle of the vehicle, the test bench has two measuring positions in the x-direction, in each of which positions one measuring unit is provided for each wheel of a non-steered axle of the right-hand and left-hand side of the vehicle, wherein the measuring unit acquires measured values for determining at least one parameter of the orientation of the wheel plane of the relevant wheel, wherein an evaluation unit is furthermore provided, to which evaluation unit the measured values of the measuring units are supplied and in which evaluation unit at least the geometric driving axle is ascertained for the vehicle in the position, in the position of the vehicle in which the wheels of the steered axle of the vehicle are positioned, on the wheel fixtures, wherein a sensor unit is furthermore provided in this position in order to record changes in the orientation of the vehicle-related frame of reference.

6. Measuring unit, wherein the measuring unit evaluates the image of a planar pattern that is projected onto the surface of a wheel of a vehicle in order to determine the orientation of the wheel plane by means of the evaluation, wherein the planar pattern consists of a plurality of parallel lines, in particular for use in connection with one of the above-mentioned methods or one of the above-mentioned measuring, test and/or setting benches, characterized in that the planar pattern is generated by means of a sensor which emits light in a linear manner being oriented such that the line of said linearly emitted light is not oriented horizontally, in that the sensor can be displaced in the vehicle length direction (x-direction) in order to carry out a measurement of the orientation of the wheel plane, wherein the image of the line of said sensor is evaluated in a plurality of positions of the sensor in the x-direction, in order to compose therefrom an image of a planar pattern consisting of a plurality of parallel lines.

7. Measuring unit according to claim 6, characterized in that the line of sensor is generated in that the line is generated by a scanning process using a point light source.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] An embodiment of the invention is shown in the drawings. In said drawings:

[0062] FIG. 1: is a schematic view of a chassis bench,

[0063] FIG. 2: is a schematic view of a vehicle in the chassis bench in position A,

[0064] FIG. 3: is a schematic view of a vehicle in the chassis bench in position B,

[0065] FIG. 4-6: show wheels having lines projected thereon in each case.

DETAILED DESCRIPTION

[0066] FIG. 1 is a schematic view of a chassis bench 1 for determining and setting the chassis geometry of a vehicle. Said chassis bench 1 comprises two ruts 2 and 3. One wheel fixture 4 and 5, respectively, is located in each of the ruts 2 and 3.

[0067] Said wheel fixtures are constructed such that they are mounted by means of a floating plate and comprise a double roller system on which the relevant wheel is positioned. In turn, at least one of the rollers of said double roller system is driven. As a result, each of the positioned wheels can be rotated uniformly by means of a rotation of the driven roller(s), without introducing mechanical stresses into the corresponding axle.

[0068] The positioned wheels are the wheels of the steered axle of the vehicle. This is the front axle in conventional vehicles.

[0069] One measuring unit 6 and 7, respectively, is assigned to each of said wheel fixtures 4 and 5, respectively. The fixed measuring units 6 and 7 for the front axle each have at least two triangulation sensors which illuminate the lateral face of the tire using at least one laser line, and thus measure the chassis geometry parameters. In this respect, reference is made for example to patent application EP 0 280 941 A1.

[0070] Said measuring units 6 and 7, respectively, acquire the parameters of the chassis geometry of wheels that are positioned on the relevant wheel fixtures 4 and 5, respectively.

[0071] Two further measuring probes 8 and 9 for measuring the rear axle are also visible, which measuring probes are located at a spacing x.sub.1 in the longitudinal direction of a vehicle from the measuring probes 6 and 7. Said measuring probes 8 and 9 are displaceable over the entire vehicle length, from the fixed measuring units 6 and 7. This is indicated by the arrow x.sub.1. The position of the measuring units 8 and 9 in the longitudinal direction (x-direction) is acquired in each case using a length measuring system.

[0072] It can furthermore be seen that said measuring probes 8 and 9 have a range x.sub.V in which said measuring probes 8 and 9 are displaceable. While the measuring probes 8 and 9 are displaced in said range x.sub.V, the measuring probes 8 and 9 carry out a plurality of measurements of parameters of the chassis geometry of wheels that are in each case located in the measuring range of the measuring probes 8 and 9.

[0073] Each of said measuring units 8 and 9 comprises two triangulation sensors which are arranged in a V-shape, such that the at least one laser line per triangulation probe radially illuminates the lateral face of the tire when the displaceable measuring units 8 and 9 are centered with respect to one of the rear wheels. Said radial illumination is advantageous in that in the process the image of the lines appears on the tires such that the bead of the tire is illuminated. As a result, the image of the line extends in a characteristic manner, and therefore changes are easy to identify.

[0074] The chassis parameters to be determined for each wheel are at least the toe angle and the coordinates of the wheel center in the horizontal (x,y plane).

[0075] The chassis bench comprises a calibration gauge which defines a base coordinate system when inserted into the bench, into which base coordinate system the coordinate systems of the four measuring units are transferred by measuring the inserted calibration gauge. This is the frame of reference assigned to the test bench.

[0076] The following method steps are carried out:

[0077] Moving the vehicle into a position A (FIG. 2) which is spaced apart from a position B (FIG. 3) such that the spacing between said two positions corresponds to half the circumference of a rear wheel of the vehicle. In this case, position B is defined in that the front wheels of the vehicle are positioned in the wheel fixtures 4, 5 so as to be at the front, between the rollers of the relevant double roller system.

[0078] Measuring the parameters of the rear wheels in position A of the vehicle in that a measurement is made on each side of the vehicle, such that in each case one measuring unit 8, 9 on each side of the vehicle is displaced in the vehicle length direction. This is a displacement of the measuring units 8 and 9, which is denoted in FIG. 2 (and in FIG. 3) by the arrow x.sub.V. In this case, each of the two measuring units 8, 9, when displaced in the vehicle length direction (x.sub.V), scans the contour of the lateral face of the tire of each of the rear wheels. The toe values of the rear wheels are ascertained from said contour measurement of the lateral face of the tire of the rear wheels.

[0079] For example the orientation of the perpendicular of the rear axle in the x,y plane with respect to the base coordinate system of the calibration gauge (test bench frame of reference) can be correlated with position A via the wheel centers. This is the determination of the at least one parameter of the orientation of the vehicle-related frame of reference (example: orientation of the perpendicular of the rear axle) relative to the test bench frame of reference (defined by the calibration gauge).

[0080] Moving the vehicle into position B (FIG. 3).

[0081] Measuring the chassis parameters of the rear wheels in position B of the vehicle in the say way as in position A. The toe values of the rear wheels are ascertained from the contour measurement of the lateral face of the tire of the rear wheels.

[0082] The orientation of the perpendicular of the rear axle in the x,y plane with respect to the base coordinate system of the calibration gauge (test bench frame of reference) measured in position B via the wheel centers. In this case it should be noted that said orientation of the perpendicular of the rear axle relative to the base coordinate system of the calibration gauge can change between positions A and B if the vehicle is not moved exactly in the longitudinal direction of the test bench. When being moved from position A into position B. This is the determination of the at least one parameter of the orientation of the vehicle-related frame of reference (in this example: orientation of the perpendicular of the rear axle) relative to the test bench frame of reference (defined by the calibration gauge) in position B.

[0083] Measuring the parameters of the front wheels in position B of the vehicle in that a measurement is made on each side of the vehicle such that a wheel runout measurement is made when the front wheels rotate, in order to compensate for the wheel runout. This measurement is carried out taking account of the steer angle.

[0084] Carrying out the wheel runout compensation of the rear wheels by means of averaging the toe angles with respect to the direction of the axle direction of the rear axle in position A and B.

[0085] Calculating the toe angle of the front and rear wheels in position B, based on the test bench frame of reference.

[0086] Ascertaining the direction of the axis of symmetry of the vehicle in position B of the vehicle.

[0087] Calculating the toe angle of the front axle with respect to the geometric driving axle and steering wheel position, and the toe angle of the rear axle with respect to the axis of symmetry in position B.

[0088] In this method, it has been found to be advantageous that just two wheel fixtures for rotating the front wheels are required in the chassis bench, but that the parameters of the chassis geometry can still be ascertained in a manner that takes full account of the wheel runout compensation, i.e. at the front and rear axle.

[0089] Displacing the measuring units and 9 causes the relevant wheel to be covered by the projected pattern.

[0090] The Wheel runout compensation for the rear wheels is achieved by moving the vehicle from position A into position B. This is described in patent application WO 2010/025723 A1. The parameters of the front wheels are ascertained by means of the wheel fixtures 4, 5 and the associated measuring units 6, 7, in a manner known per se, by means of the front wheels being rotated while the measurement is being carried out. As a result, a plurality of measurements are made at different angular positions by means of rotating the wheels. The steer angle can be taken into account by means of using a steering wheel balance.

[0091] FIG. 4 is a schematic view of a rear wheel 401. It can be seen that the measuring probe is moved relative to the rear wheel. The measuring probe is represented by the projected lines 402 and 403. The center line 404 of the measuring probe is also shown. It can be seen in particular from the position of the center line 404 in the three views in FIG. 4 that the measuring probe is moved forwards, past the rear wheel 401, in the vehicle length direction of the vehicle. In the process, the lines 402 and 403 meet different points of the rear wheel 401.

[0092] It can be seen in this case that one of the lines 402, 403 would be sufficient for the scanning process for simulating the multiline sensor. The measuring unit is nonetheless depicted in the V-shape shown because it is thus possible to continuously determine the location of the plane of symmetry of the vehicle when the vehicle is stationary in position B, even without displacing the measuring units 8 and 9. It is not necessary to fully acquire the orientation of the wheel plane for this purpose. All that is important is the location of the wheel center, the changes of which can be acquired using the two V-shaped lines.

[0093] FIG. 5 shows the wheel 401 comprising a plurality of the projected lines 402 and 403, which lines were recorded at different time points during the displacement of the measuring probe relative to the rear wheel 401.

[0094] FIG. 6 shows that the lines can be evaluated such that the measuring points are separated in accordance with the z-coordinates thereof (i.e. with respect to the vertical position), and arranged into bands of measured values having similar z-coordinates. Said bands can be treated in the following as lines.

[0095] The present invention can be used for logging the measurements. Likewise, deviations from target values can be indicated, such that the parameters of the chassis geometry can be corrected by means of corresponding setting work.