RU2368883C2 - Method for adjustment of vehicle wheel alignment angle - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: invention is related to procedure of measurement and adjustment of vehicle wheels camber and toe. Method consists in the fact that optical target is made in the form of circular cylinder, an accidental image is applied on it. For each position of vehicle wheel they read images with the help of television chamber. Using computer, they calculate functions of mutual correlation of memorised video signals of extreme reading lines and extreme reading lines relative to central line, their extremes are defined, positions of which are used to identify appropriate shifts of optical target images. Shift of extreme reading lines images is identified. Ratio of extreme reading lines images shift to distance between extreme reading lines of television camera is identified, and its value is taken, when required, as wheel camber. Coefficient of television camera lens zoom is increased until this value of wheel camber is permanent to appropriate maximum value of television camera lens zoom coefficient. Shifts of extreme reading lines images are identified relative to central line, and camber is determined, steering wheel is installed in initial position, and wheel camber is adjusted.

EFFECT: simplified process of obtainment and application of information about shifts of optical target images.

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Description

The method relates to techniques for testing wheeled vehicles, in particular measuring and adjusting the camber and toe angles of automobile wheels.

Known devices for adjusting the angles of installation of a car wheel that implement the corresponding methods (see, for example, stands of the American company "HUNTER" with measuring systems DSP250, DSP300. Website www.hunter.com). The measuring systems of these stands, which use capacitive angle sensors, built-in specialized digital processors, infrared equipment, cable or ether channels for communication with computers, etc., require manual installation on the vehicle’s wheels, frequent calibration and adjustment, and to perform a number of operations - to hang out a car.

With the known advantages of these methods, implemented using appropriate devices, it should be noted their complexity, including in operation, and a low degree of automation.

The closest in technical essence and the achieved results is the method of adjusting the angles of installation of the wheel of the car, implemented using the American stand "Hunter 811" (see website www.hunter.com., CD). This method is adopted as a prototype.

The method is based on the modern technology Three Dimensions (3D), through which, in particular, spatial measurements are realized, for example, using optoelectronic devices.

When implementing this method of adjusting the angles of installation of a car’s wheel, the car is mounted with a longitudinal plane parallel to the optical axis of the television camera, an optical target with a flat one-sided practically isotropic deterministic contrast image is mounted on the wheel (light triangles on a dark background, arranged in rows). First, a car is rolled, for example, one turn of the wheel in the direction of the television camera. In this process, the images of the optical target are read by a television camera, the video signals of which are stored in a computer, the displacements of the images of the optical target are determined from them, by which the angles of the car wheel are calculated. In particular, the radial and axial runout of a wheel can be measured in this way. Then the car wheel is stopped at a predetermined distance from the television camera, the images of the optical target are read out again by the television camera, the video signals of which are stored in a computer, the displacements of the images of the optical target are determined from them, by which the angles of the car wheel are calculated and additional adjustments are made.

With all the advantages of this method of adjusting the angles of installation of a car’s wheel, the processes for determining the displacements of images of an optical target are clearly complicated, because require the use of complex algorithms and significant computing power, for example, due to the fact that in the process of rolling a car the image of an optical target in the field of view of a television camera undergoes cardinal changes.

The technical result of creating the proposed method for adjusting the angles of installation of a car’s wheel is to eliminate this disadvantage of the prototype, in particular, the fact that the optical target is made in the form of a round cylinder, onto which a random image with orthogonal isotropy is applied. This embodiment of the optical target, in particular, simplifies the processes of obtaining and using information about the displacements of the images of the optical target, for example, within certain limits, regardless of the gauge of the car and the diameter of its wheel.

The technical result is achieved by the fact that:

1. In the method of adjusting the mounting angles of the car wheel, in which the car is mounted with a longitudinal plane parallel to the optical axis of the television camera, an optical target with a contrast image is mounted on its wheel, the car is rolled, for example, one turn of the wheel in the direction of the television camera, the car wheel is stopped by a predetermined distance from the television camera, for each position of the wheel of the car, images of the optical target are read by a television camera, the video signals of which are recorded are mined in the computer, they determine the displacements of the images of the optical target, with which they calculate and adjust the angles of the car’s wheels — the optical target is made in the form of a round cylinder, a random image with orthogonal isotropy is applied to it, for each position of the car’s wheel, images are read with using a television camera, for example, with three equally spaced lines, using a computer, the cross-correlation functions of the stored video signals of the extreme reading lines and the extreme reading lines relative to the center line, determine their extrema, the positions of which determine the corresponding displacements of the images of the optical target, while rolling the car at each value of the angle of rotation of the wheel, minimize the sum of the displacements of the images of the extreme reading lines relative to the central line by moving the television camera, determine the image offset of the extreme reading lines and in relation to the distance between the extreme reading lines of the television camera, the sum of for the camber of the wheel and the angle of the axial runout of the wheel as a function of the angle of rotation of the wheel, the angle of the axial runout of the wheel is determined by the variable component, and the angle of the camber of the wheel is determined by the constant component, the radial runout of the wheel is determined by the displacement of the television camera, at a given distance from the television camera, the wheel is minimized the sum of the displacements of the images of the extreme reading lines relative to the center line by moving the television camera, determine the ratio of the displacement of the images of the extreme reading lines ok to the distance between the extreme reading lines of the television camera and take its value, if necessary, as the angle of the camber of the wheel, increase the zoom factor of the lens of the television camera until this value of the angle of the camber of the wheel is constant, to the corresponding maximum magnification factor of the lens of the television camera, determine the offset image of the extreme reading lines relative to the center line, and the convergence angle is determined as the ratio of the sum of these offsets to the size between to the extreme lines of the television camera, set the steering wheel to its original position and adjust the angle of convergence of the wheel.

2. In the method according to claim 1, at a predetermined distance from the television camera, the wheels minimize the amount of displacement of the images of the extreme reading lines relative to the center line by moving the television camera, determine the ratio of the displacement of the images of the extreme reading lines to the distance between the extreme reading lines of the television camera and take its value, if necessary, for the angle of the camber of the wheel, determine the offset image of the extreme reading lines relative to the center line and determine the angle of convergence to ratio to half the amount of displacement to the distance between the projections of these lines on the optical target along the optical axis of the television camera, mounted steering wheel to the initial position and adjust the toe angle of the wheel.

The implementation of the method is illustrated in figure 1 and figure 2. The measured angles are small (their values usually do not exceed 2 angular degrees).

Figure 1 shows the principle of measuring the relative movements of the corresponding images when measuring the installation angles of the wheel of the car.

We take the right coordinate system 0XYZ, the beginning of which coincides with the axis AA of the vehicle’s wheel and its conditional axis of rotation relative to the suspension, for example, the left front wheel of the vehicle. We are interested in the relative installation parameters of the car wheel by rotating the axis of the AA wheel around the 0Z axis (camber angle α of the car wheel) and around the Y axis (convergence angle γ of the car wheel). The relative radius (R-M) and the axis of the AA wheel are perpendicular.

When the wheel is rotated through the camber angle α, its plane will become parallel to the line

CC ₁ . We assume that for a given K, it is possible to measure relative displacements b along the 0X axis and, accordingly, it is possible to determine the camber angle α as α≈tgα = b / К.

An additional rotation of the axis AA relative to the axis 0Y will cause a corresponding rotation of the plane of the wheel by the angle of convergence γ, which at a relative radius (R-M) will create a relative displacement g along the axis 0X. Similarly, we will assume that with the known (R-M), it is possible to measure the relative displacements g along the 0X axis and, accordingly, we can determine the convergence angle γ as γ≈sinγ = g / (R-M).

A television camera (TC) is installed so that its optical axis (OTC) crosses the 0X axis and is perpendicular to the 0XY plane. Using the TC, the corresponding images (not shown) associated with the axis AA of the wheel are read, which allow the relative displacements of these images to be determined directly in the TC focal plane. The TC has the ability to move along the Y axis. The video signals of the corresponding images are stored in a computer (not shown).

To measure the indicated displacements, they must have the corresponding features that allow them to be determined. Such features are inherent in the original random image having orthogonal isotropy and associated with the axis AA of the wheel. The proposed image (not shown in FIG. 1) is relatively simple to execute in the form of wheels perpendicular to the axis AA of randomly arranged parallel lines, the width of which is also random. Strict isotropy of the image along these lines allows you to find the relative displacements of the images (which are represented in the computer by the corresponding video signals) along the X axis by calculating these displacements from the extremum position of the cross-correlation function (PCF) of the corresponding video signals. In turn, isotropy in the orthogonal direction eliminates the ambiguity of calculating the position of the extremum of the FVC. In general, relative image offsets can be found for any points in the original random image. In this case, the necessary condition for obtaining measurement information is the reading of the video signals of the specified image, and the presence of a distinguishable extremum of the FVC is sufficient. As is known from the theory of optimal reception of messages, the accuracy of determining such an offset is proportional to the amount of information contained in the signal (video signal). We note an important feature of the chosen method of measuring the relative displacements b and g - it eliminates measurement errors due to parallax.

Figure 2 shows a view of the wheel 1 of a car (not shown). For her, γ = 0. The plane 0XZ is located at a distance d and is parallel to the horizontal rigid base 2 on which the equipment (for example, a shopping mall) and the car are installed. Wheel 1 is in the field of view of the lens TC (figure 2 is not shown). When the axial runout of the wheel 1, its instantaneous axis of rotation forms with the axis AA the angle of the axial runout β (not shown). When the wheel beats radially, its axis AA moves along the Y axis when rolling the car (size d changes).

The optical axis of the TC passes through the axis of the quick-detachable technological optical target (OM) 3 mounted on the wheel 1, made in the form of a round cylinder having a radius R. A random image with orthogonal isotropy is plotted on it (not shown in FIG. 2). The axis ОМ 3 coincides with the axis АА of the wheel 1. The execution of ОМ 3 in the form of a cylinder allows one to obtain relative displacements g determined by the angle of convergence γ. The TC generates a reading raster on OM 3, for example, from three lines 4, 5 and 6 (shown conditionally), which are parallel to the 0X axis and are located at fixed distances K. With lines 4, 5 and 6 of the TC raster, the corresponding images of OM 3 can be read and stored, for example, in a computer (not shown). Moreover, as follows from figure 2, the video signal, for example, line 4 is ahead of the video signal of line 5 in phase, and line 6 is behind. The values of segments b ₄₅ and b _{65 are} directly proportional to such phase offsets, and segment b ₄₆ (not shown) is the phase shift of the video signal of line 4 relative to line 6, and from figure 2 it follows: b ₄₆ = 2 b ₄₅ = 2b ₆₅ . From the presented figures it also follows that the relative displacements of images b ₄₅ and b ₆₅ have opposite signs, ag ₄₅ and g ₆₅ are the same.

The car can be rolled along a horizontal rigid base 2 along the axis 0Z in the process. Moreover, the image will always form a camber angle α with the Y axis, if there is no axial runout of the wheel 1 relative to the axis AA of the car. Otherwise, the beat angle β will be a variable component of the camber angle α (when the wheel rotates through the angle ω). Similarly, a variable component of size d will determine the radial runout of wheel 1.

A noticeable axial runout of the wheel 1 virtually eliminates the advisability of adjusting its installation angles, i.e. such a wheel must be rejected.

The cross section along the BB allows one to find the relative radius (R-M) necessary for determining the relative displacements of images g at γ ≠ 0. The relative displacements g ₄₅ and g ₆₅ (not shown in FIG. 2) of images of lines 4 and 6 relative to line 5 of the image OM 3 are determined by turning this radius around the Y axis by an angle γ (in accordance with FIG. 1). Therefore: g ₄₅ / (R-M) = sinγ, g ₆₅ / (R-M) = sinγ. The values of the relative displacements g ₄₅ , g _{65 of the} video signals are determined by the convergence angle γ of the wheel, the position of the TCI in the vertical plane relative to its position in FIG. 2 (for example, due to the radial run-out of the wheel 1) and the distance M, determined using the radius R and the auxiliary angle ε .

If M → 0 and the TCI passes through the axis AA of wheel 1 (as in FIG. 2), then the expression for sinγ is significantly simplified: g ₄₅ / K = sinγ≈γ (at K = R). Obviously, the last equality allows all computational operations to be carried out through quantities determined only in the focal plane of the TC. In order to ensure the fulfillment of this equality (or K≈R), it is possible to increase the coefficient of magnification of the TK lens, and use the extremum value of the FVK as a criterion for the limiting value of increasing this parameter of the TC. Its value will fall to the noise value of the FVC signal (that is, it will become impossible to correctly determine the image offsets) if lines 4 and 6 "crawl out" beyond the boundaries of the OM 3 image (K> R).

Note that a certain change in the scale of images read, for example, by lines 4 and 5, 6 and 5 of the TC (they are spaced along the 0Z axis - see Fig. 2) affects only the extremum of the CVF and does not introduce errors in determining the displacements of the OM 3 images .

The method according to claim 1 is as follows. When it is implemented based on the principle of superposition, both angles (α and γ) of the installation of wheel 1 are taken into account.

The process 1.1.

1.1.1. An optical target is made in the form of a round cylinder and a random image with orthogonal isotropy is applied to it.

1.1.2. The car is started on a rigid base 2 and set so that its longitudinal plane is parallel to the plane 0YZ. They are mounted on wheel 1 of OM 3 and fixed so that its axis coincides with the axis AA of wheel 1, and OM 3 itself is in the field of view of the camera.

1.1.3. The OM 3 images are read in lines 4, 5, 6 of the TC raster and the video signals are stored, for example, in a computer. Then, using the computer, calculating the cross-correlation function (FVC) of the video signals of lines 4 and 5, 6 and 5, determine the positions of the extrema of the FVC on lines 4 and 6, i.e. determine the sizes (g ₄₅ + b ₄₅ ) and (g ₆₅ -b ₆₅ ). Find the sum of (g ₄₅ + b ₄₅ ) + (g ₆₅ -b ₆₅ ). From figure 2 it is seen, and from an example of the execution of fragments of the method (see below) it follows that this amount has a minimum if the quality control crosses the axis AA of the wheel 1. In the same position | b ₄₅ | = | -b ₆₅ |, g ₄₅ = g ₆₅ or (g ₄₅ + b ₄₅ ) + (g ₆₅ -b ₆₅ ) = (g ₄₅ + g ₆₅ ). Therefore, change the size d (TC position) so as to minimize the amount to the value (g ₄₅ + g ₆₅ ) = 2g ₄₅ = 2g ₆₅ .

1.1.4. Using the FVC extremum, the offset b _{46 of the} image of row 4 relative to row 6 is calculated.

1.1.5. Remember the values of b ₄₆ and the position of the TC.

1.1.6. A car is rolled, for example, in the direction of the shopping mall (turn the wheel 1 by incrementing the angle ω).

1.1.7. Repeat steps 1.1.3, 1.1.4, 1.1.5, 1.1.6 the required number of times in order to obtain and remember the dependences of b ₄₆ (ω) and the position of the TCM d (ω) on the angle of rotation ω of the wheel, for example, by one its turnover.

1.1.8. The variable components of the dependencies obtained in operations 1.1.3, 1.1.4, 1.1.5, 1.1.6, 1.1.7 are determined and the presence of axial and radial runout of the wheel is judged by them. The variable component b _β (ω) of the dependence b ₄₆ (ω) determines the axial runout angle β (ω) = b _β (ω) / 2К, and the variable component d (ω) determines the radial runout of wheel 1.

1.1.9. Determine the constant components of the dependences d (ω) and b ₄₆ (ω) of the wheel 1. From the constant component b _{α of the} process b ₄₆ (ω) find α≈tgα = b _α / 2K, and the constant component d (ω) determines the position of the axis AA of the wheel relatively tight base 2.

According to the results of measuring the beating of the wheel, if necessary, a decision is made to replace the wheel 1 with a conditional one.

Process 1.2.

1.2.1. Fix the position of the wheel 1 at a given distance from the TC.

1.2.2. Perform clause 1.1.3.

1.2.3. Calculate with the help of the extremum FVK b ₄₆ and find α≈tgα = b ₄₆ / 2K, take, if necessary, this value as the angle of the camber of the wheel.

1.2.4. Change the coefficient of magnification of the lens of the TC upwards and perform items 1.2.3, 1.2.4 to the boundary of the stable determination of the ratio of clause 1.2.3.

1.2.5. The image offsets (g ₄₅ + b ₄₅ ) and (g ₆₅ -b ₆₅ ) are determined. Moreover, g ₄₅ = g ₆₅ .

1.2.6. Calculate γ≈sinγ = [(g ₄₅ + b ₄₅ ) + (g ₆₅ -b ₆₅ )] / 2K.

1.2.7. If necessary, establish the initial position of the steering wheel; adjust the angle of convergence γ so as to obtain g ₄₅ or g ₆₅ corresponding to the desired angle of convergence γ.

The method according to claim 2 is as follows. When it is implemented based on the principle of superposition, both angles (α and γ) of the installation of wheel 1 are taken into account.

The process 2.1.

2.1.1. Perform operations 1.1.1 ... 1.1.8, 1.2.1 ... 1.2.5 of the process of the method according to claim 1.

The process 2.2.

2.2.1. Find g ₄₅ = g ₆₅ = 0.5 [(g ₄₅ + b ₄₅ ) + (g ₆₅ -b ₆₅ )].

2.2.2. Γ≈sinγ = g ₄₅ / R {1-cos [arcsin (K / R cosα)]} or γ≈sinγ = g ₆₅ / R {1-cos [arcsin (K / R cosα)]} is calculated.

2.2.3. If necessary, establish the initial position of the steering wheel; adjust the angle of convergence γ so as to obtain g ₄₅ or g ₆₅ corresponding to the desired angle of convergence γ.

Operations can be carried out for all four wheels of the car, using four shopping malls and making the necessary corrections. They are determined by the position of the TCI d relative to the horizontal rigid base 2 (for example, if the TC for the rear wheels are located above the TC of the front wheels) and the geometric parameters of the car, for example, the distance between its front and rear axles. As follows from the above, the angular displacement of the TC under certain conditions is equivalent to its linear displacement.

An example of the execution of fragments of the method

Let R = 150 mm or 1050 pixels (in the dimension of the focal plane of the TC), α = γ = 2 °. The TK uses a solid-state photosensitive matrix with a size of 2048 × 2048 pixels (4 megapixels), the optics of the TK provide the required resolution. Each pixel has dimensions δ × δ = 0.003 × 0.003 mm. We organize the reading raster on the matrix with lines No. 1 (for example, line 4), 1024 (line 5) and No. 2047 (line 6), i.e. size 2 · K = 2046 pixels (on the matrix). Obviously, the matrix used is redundant and it is desirable to use a special matrix, for example, with the characteristics stated above.

1. We define g ₄₅ and g ₆₅ at γ = 2 ° (operation 1.1.3).

The ratio (for α = 0) is obtained for the sizes:

g ₄₅ = R sinγ {cos [arcsin (Δ / R)] - cos [arcsin ((K / cosα + Δ) / R)]};

g ₆₅ = R sinγ {cos [arcsin (Δ / R)] - cos [arcsin ((K / cosα-Δ) / R)]}.

Here Δ is the value of the possible offset of the reading raster TC along the Y axis relative to the position shown in figure 2. The calculated values of these values are shown in table 1.

Table 1 Δ g ₄₅ g ₆₅ g ₄₅ + g ₆₅ -twenty 25.8 32.41 58.21 -fifteen 26.38 31.12 57.5 -10 27 30.07 57.08 -5 27.67 29.18 56.85 0 28.39 28.39 56.78 5 29.18 27.67 56.85 10 30.07 27 57.08 fifteen 31.12 26.38 57.5 twenty 32.41 25.8 58.21

After that, to determine the angle (α + β), it is necessary to find the leg b _{46 of the} right triangle, i.e.: b ₄₆ = 2K tg (α + β). For α = 2 ° and β = 0 we get: b ₄₆ = 2K tgα = 2046 · tg 2 ° = 2046 · 0.035 = 71.61 pixels or: 71.61 pixels / 120` = 0.6 pixels per 1 minute of angle camber α (tgα≈α for small angles).

2. Define the image displacement at γ = 2 ° (operation 2.2.2).

A relation is obtained (for α = 0) for the size g ₄₅ = R sinγ {1-cos [arcsin (K / R)]}. We find g ₄₅ = 1050 sin 2 ° {1-cos [arcsin (1023/1050)]} = 20.39 pixels. Or: 20.39 pixels / 120` = 0.2366 pixels per 1 arc minute of the convergence angle γ. The value of the parameter g ₄₅ , as well as the parameters b (for the angle α), is in the processes of the method (see above) and does not require calculation according to the formula given in the example.

Thus, the proposed "Method of adjusting the angles of installation of the wheel of a car" is quite feasible, does not have significant sources of measurement errors, provides minimal labor and high quality of work due to the high degree of automation of measurements. Potentially, the method can be quite simply interfaced with a human operator using a special interactive program implemented, for example, on a computer serving it. The prototype works with a similar program.

After analyzing the prior art on scientific and technical sources of information, the applicant did not find an analogue with features identical to the features of the present invention "Method of adjusting the installation angles of the wheel of a car".

The selected prototype made it possible to identify in the claimed method a combination of essential and clearly not following from the prior art in relation to the perceived technical result of the distinguishing features set forth in the formula of the invention. Therefore, the claimed invention, the "Method of adjusting the angles of installation of the wheels of the car" meets the criteria of novelty and inventive step.

The criterion of industrial applicability of the proposed "Method of adjusting the angles of installation of the wheels of the car" is confirmed by its potential effectiveness.

Claims (3)

1. A method of adjusting the angles of installation of a car wheel, in which a car is mounted with a longitudinal plane parallel to the optical axis of the television camera, an optical target with a contrast image is mounted on its wheel, a car is rolled, for example, one turn of the wheel in the direction of the television camera, the car wheel is stopped at a predetermined the distance from the television camera, for each position of the car’s wheel, images of the optical target are read by a television camera, the video signals of which are placed in a computer, they determine the displacements of the images of the optical target, with which they calculate and adjust the angles of the car wheel, characterized in that the optical target is made in the form of a round cylinder, a random image with orthogonal isotropy is applied to it for each position of the car wheel images are read using a television camera, for example, in three equally spaced lines, the cross-correlation functions of the stored video signals of the extreme reading lines are calculated using a computer the extreme reading lines relative to the center line, determine their extrema, the positions of which determine the corresponding displacements of the images of the optical target, while rolling the car at each value of the angle of rotation of the wheel, minimize the sum of the displacements of the images of the extreme reading lines relative to the central line by moving the television camera, determine the image offset of the extreme reading lines and in relation to the distance between the extreme reading lines of the television camera about the sum of the angle of the camber of the wheel and the angle of the axial runout of the wheel is divided as a function of the angle of rotation of the wheel, the angle of the axial runout of the wheel is determined by the variable component, and the angle of the collapse of the wheel is determined by the constant component, the radial runout of the wheel is determined by the displacement of the television camera, at a given distance from the television cameras minimize the sum of the displacements of the images of the extreme reading lines relative to the center line by moving the television camera, determine the ratio of the displacement of the images of the extreme their reading lines to the distance between the extreme reading lines of the television camera and take its value, if necessary, for the angle of the camber of the wheel, increase the magnification factor of the lens of the television camera until this value of the angle of the camber of the wheel is constantly up to the corresponding maximum magnification factor of the lens of the television camera , determine the offset image of the extreme reading lines relative to the center line and determine the angle of convergence, set the steering wheel to the starting position and adjust the angle of convergence of the wheel. 2. The method according to claim 1, characterized in that at a predetermined distance of the wheel from the television camera, the sum of the displacements of the images of the extreme reading lines relative to the center line is minimized by moving the television camera, the ratio of the displacement of the images of the extreme reading lines to the distance between the extreme reading lines of the television camera is determined and received its value, if necessary, over the angle of the camber of the wheel, determine the displacement of the images of the extreme reading lines relative to the center line and determine t the convergence angle as the ratio of half the sum of these displacements to the distance between the projections of these lines on the optical target along the optical axis of the television camera, set the steering wheel to its original position and adjust the angle of convergence of the wheel. 3. The method according to claim 1, characterized in that at a predetermined distance of the wheel from the television camera, the sum of the displacements of the images of the extreme reading lines relative to the center line is minimized by moving the television camera, the ratio of the displacement of the images of the extreme reading lines to the distance between the extreme reading lines of the television camera is determined and received its value, if necessary, over the angle of the camber of the wheel, determine the displacement of the images of the extreme reading lines relative to the center line and determine t the convergence angle as the ratio of the sum of these displacements to the size between the extreme rows of the television camera, set the steering wheel to its original position and adjust the angle of convergence of the wheel.

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