Patent Publication Number: US-2022221271-A1

Title: Wheel alignment measurement system and method

Description:
The present application claims priority of U.S. provisional application Ser. No. 63/135,882 filed Jan. 11, 2021, which is hereby incorporated herein by reference in its entirety 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to a wheel alignment measurement system and method, and in particular to a system and method in which an optical gauge of known dimensions is affixed to a wheel assembly and imaged by a camera. 
     In the automotive industry, proper vehicle quality requires measurement and adjustment of wheel alignment settings, both during manufacture and subsequently during the useful life of the vehicle. Proper positioning and alignment of vehicle wheels, and especially steerable wheels such as the front wheels of a vehicle, requires the setting of toe, camber angle, and caster angle. Toe is the angle between the vehicle&#39;s longitudinal axis and a plane through the center of the wheel/tire and affects the straight-ahead running of the vehicle as well as steering. Camber angle is the inclination of the wheel axis toward the road surface in a vertical plane and is negative when the top of the wheel is inclined toward the center of the vehicle. Caster angle is the tilt of the steering axis parallel to the direction of the vehicle centerline. A tilt toward the rear of the vehicle results in a positive caster angle. During assembly and/or repair of vehicles, it is important to measure, adjust or audit, and set the toe as well as the camber and caster angles of vehicle wheels, and especially steerable wheels, so the vehicle will drive and steer properly 
     SUMMARY OF THE INVENTION 
     The present invention provides an efficient and cost effective way of determining wheel alignment characteristics of a wheel assembly on a vehicle. 
     According to an aspect of the present invention, a system for determining alignment characteristics of a wheel assembly mounted on a vehicle includes an optical gauge configured to be selectively attached to a wheel assembly, where the optical gauge includes a mounting base having an underside that is affixed to the wheel assembly and includes a gauge piece having a known dimension. The system further includes a light projector configured to project light that is directed onto the optical gauge when attached to the wheel assembly, a digital imager, and a controller. The digital imager is configured to image light from the light projector that is reflected from the optical gauge, with the controller being configured to calculate a distance from the optical gauge based on the imaged light that is reflected from the optical gauge and the known dimension of the gauge piece. 
     The system further includes a reflector, where the light projector is configured to project light at the reflector and the reflector is configured to direct light at the optical gauge at a known angle, with the controller configured to calculate the distance from the optical gauge further based on the known angle. In a particular embodiment the reflector comprises an adjustable reflector, such as a micro-electro-mechanical system (“MEMS”) whereby the known angle at which the reflector directs light at the optical gauge is changeable and known. In accordance with a further aspect of the present invention, the distance from the optical gauge calculated by the controller comprises a distance from the optical gauge to the digital imager. Still further, the controller is configured to calculate the distance from the optical gauge further based on a known distance from the digital imager to the reflector. 
     In an embodiment of the optical gauge, the underside of the mounting base may be adhesively mounted to the wheel assembly, where the mounting base may comprise a tape. The known dimension of the gauge piece of the optical gauge comprises a thickness of the gauge piece, and may further comprise a width and/or length of the gauge piece. Still further, the optical gauge may further include a substrate disposed between the gauge piece and the mounting base, where the known dimension of the gauge piece includes a thickness of the gauge piece from a surface of the substrate to an upper surface of the gauge piece. A surface of the gauge piece, such as the upper surface or another surface, may further include a computer readable code, and the digital imager may be configured to image the computer readable code to enable the controller to determine the distance from the optical gauge. 
     Multiple optical gauges disposed about a wheel assembly may be used to determine multiple distances, such as to one or more digital imagers that are located in a known orientation, whereby a plane may be defined based on the distances, with the plane representing the alignment of the wheel assembly. 
     A method of determining the alignment characteristics of a wheel assembly using such a system includes affixing one or more optical gauges to a wheel assembly, projecting light from a light projector at a reflector, directing light from the light projector with the reflector at the optical gauges, and imaging light reflected from the optical gauges with a digital imager. The method further includes calculating a distance from the optical gauges with a controller based on the imaged light that is reflected from the optical gauges and the known dimension of the gauge piece and the known angle of the reflector. 
     According to a further embodiment in accordance with the present invention, a system for determining alignment characteristics of a wheel assembly mounted on a vehicle includes a mounting sheet configured to be selectively attached to a wheel of a wheel assembly, with the mounting sheet including multiple optical gauges disposed thereon that each include a gauge piece comprising a known dimension. The system further includes a light projector configured to project light that is directed onto one or more of the optical gauges when the mounting sheet is attached to the wheel of the wheel assembly, a digital imager, and a controller. The digital imager is configured to image light from the light projector that is reflected from the optical gauge, with the controller configured to calculate a distance from the optical gauge based on the imaged light that is reflected from the optical gauge and the known dimension of the gauge piece. In a further aspect, the system includes a reflector with the light projector configured to project light at the reflector and the reflector is configured to direct light at the optical gauge at a known angle, where the controller is configured to calculate the distance from the optical gauge further based on the known angle. 
     According to a particular aspect of the embodiment, the mounting sheet includes an underside that is adhesively mounted to the wheel of the wheel assembly, and the mounting sheet may further include a computer readable code. Still further, an applicator machine may be used to apply the mounting sheet to the wheel of a wheel assembly. 
     A method of determining the alignment characteristics of a wheel assembly using such a system thus comprises affixing a mounting sheet having a plurality of optical gauges to a wheel assembly, projecting light from a light projector at a reflector, directing light from the light projector with the reflector at the optical gauges, imaging light reflected from the optical gauges with a digital imager, and calculating a distance from the optical gauges with a controller based on the imaged light that is reflected from said optical gauge and the known dimension of the gauge piece. 
     The present invention thus provides a cost effective and efficient system and method for determining the alignment of a wheel assembly mounted to a vehicle. These and other objects, advantages, purposes and features of this invention will become apparent upon review of the following specification in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a system in accordance with the present invention for determining the alignment of a wheel assembly of a vehicle; 
         FIG. 2  is an illustration of the toe angle of a tire and wheel assembly; 
         FIG. 3  is an illustration of the camber angle of a tire and wheel assembly; 
         FIG. 4  is a front elevation view of the tire and wheel assembly of the vehicle of  FIG. 1  to which optical gauges are affixed; 
         FIG. 5  is a top plan view of an optical gauge of  FIGS. 1 and 4  removed from the tire and wheel assembly; 
         FIG. 6  is a side elevation view of the optical gauge of  FIG. 5 ; 
         FIG. 7  is a top plan view of the system shown in relation to the wheel assembly; and 
         FIG. 8  is a perspective view of a system for determining the alignment of a wheel assembly of a vehicle in accordance with another aspect of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described with reference to the accompanying figures, wherein the numbered elements in the following written description correspond to like-numbered elements in the figures. A wheel alignment measurement system  20 , as shown in the illustrated embodiment of  FIG. 1 , is used for measuring and/or determining the alignment of a wheel assembly  22  of a vehicle  24 , where system  20  includes multiple optical gauges  26  affixed to the wheel assembly  22 , a light projector  28  that projects light  30  ( FIG. 7 ) at an adjustable reflector  32  to direct the projected light  30  onto the wheel assembly  22 , and a camera or digital imager  34  that images the light  35  reflected off the optical gauges  26  from the projected light  30 . In the illustrated embodiment, as discussed in more detail below, the optical gauges  26  have accurately known dimensions and the reflector  32  is configured as a micro-electro-mechanical system (“MEMS”) reflector or mirror such as to enable scanning of the optical gauge  26  on the tire and wheel assembly  22 . Based on the known dimensions of the optical gauges  26 , as well as the known orientations of the light projector  28  and camera  34  to the reflector  32 , and the known angular orientation of the reflector  32 , the distance from the tire and wheel assembly  22  to the camera  34  based on the optical gauge  26  can be accurately determined. By determining the distance to multiple optical gauges  26  on the tire and wheel assembly  22 , a plane can be determined that represents the three-dimensional orientation of the wheel assembly  22  and thus the alignment of the wheel assembly  22 . Moreover, in the illustrated embodiment optical gauges  26  are removably adhesively affixed to each of the tire and wheel assemblies  22  of the vehicle  24 , whereby system  20  provides an accurate, efficient and cost effective system for determining the alignment of the wheel assemblies  22 . 
     Although system  20  is illustrated in connection with only one wheel assembly  22  in  FIG. 1 , it should be understood that the system  20  may be used with each of the wheel assemblies  22  of vehicle  24  to which optical gauges  26  are affixed, and that a separate light projector  28 , deflector  32  and camera  34  may be used with each wheel assembly  22 , and/or that multiple light projectors  28 , deflectors  32  and/or cameras  34  may be used at one or all of the wheel assemblies  22  of the vehicle  24 . Still further, the light projectors  28 , deflectors  32  and cameras  34  may be held together in a known orientation by a frame or fixture  33 . As further understood from  FIG. 1 , system  20  may additionally include one or more computers or controllers  36  for processing of data from the one or more cameras  34  to determine alignment characteristics for the wheel assemblies  22 , including, for example, alignment characteristics such as toe angle  38  and camber angle  40 , as illustrated in  FIGS. 2 and 3 , as well as the center of the wheel assembly  22 . Still further, determining a plane for each wheel assembly  22  on either side of a vehicle  22  for a given axis may additionally include determining the vehicle centerline or axis of symmetry. For example, employing separate light projectors  28 , deflectors  32  and cameras  34  for the wheel assemblies  22  on either side of vehicle  24  may further enable the vehicle centerline or axis of symmetry to be determined. 
     As understood from  FIGS. 5-7 , the optical gauges  26  in the illustrated embodiment include a gauge piece  42 , a substrate  44  and a mounting base or strip that is configured as an adhesive tape  46  having a mastic underside for removably adhering or sticking to the wheel assembly  22 . The gauge piece  42  is constructed to have accurately known dimensions for its height or thickness, where the height or thickness is designated by reference letter “A” in  FIGS. 6 and 7 , as well as may include accurately known dimensions for its width W and/or length L. Gauge piece  42  additionally includes a code  48  imprinted or affixed to the top surface  50  of gauge piece  42 , such as a computer readable code, such as a bar code. As discussed in more detail below, system  20  is able to determine the distance from the wheel assembly  22  to the camera  34  based on the accurately known dimensions of gauge piece  42 . Substrate  44  provides a surface for supporting gauge piece  42  and establishing the height A from the top surface  50  of gauge piece  42  to the surface  52  of substrate  44 . Tape  46  in turn has an adhesive or mastic underside  54  that is used to secure optical gauge  26  to wheel assembly  22 . It should be appreciated that the illustrated embodiments of  FIGS. 5 and 6  may not be to scale. That is, for example, the gauge piece  42  may be constructed as a thinner component that is itself a tape like member, or even an alternative member having a different profile. Likewise, substrate  44  may be thinner. 
     As understood from  FIGS. 1 and 4 , optical gauges  26  are affixed at various positions about wheel assembly  22 , with wheel assembly  22  including both a wheel  56  and tire  58 . In the illustrated embodiment three optical gauges  26  are shown affixed about portions of tire  58 . Three or more optical gauges  26  may be used in order to define a plane. Placement of the optical gauges  26  is preferably done at or on a common aspect or feature of the wheel assembly  22 . For example, as understood from  FIGS. 4 and 7 , optical gauges  26  are positioned so as to all be disposed at the bulge area of the tire  58 . Alternatively, however, the optical gauges  26  may be placed at different locations on the wheel  56  and/or tire  58 , such as at a rim feature or otherwise. 
     The operation of system  20  will now be discussed in more detail with reference to  FIG. 7 . As there shown, light projector  28 , which in the illustrated embodiment is constructed as a laser projector, projects light  30  at reflector  32 . Reflector  32  is configured as a MEMS mirror or reflector whereby the angle is adjustably controllable and precisely known. Reflector  32  is thereby able to direct the light onto the wheel assembly  22 , and in particular onto the optical gauges  26 . In one embodiment, the reflector  32  is operated to adjust the angle of reflection in a raster pattern over the optical gauge  26 , such as to thereby scan the optical gauge  26 . The reflected light  35  from the optical gauge  26  is then captured by camera  34 , which is configured in the illustrated embodiment as an imaging sensor, such as a digital CMOS photosensor array, or the like. The scanning of the optical gauge  26  may be used to form a three dimensional model of the optical gauge  26 , and in particular of the gauge piece  42 . 
     Based on the known dimensions of the optical gauges  26 , and in particular of the gauge piece  42 , as well as the known orientations of the light projector  28  and camera  34  to the reflector  32 , and the known angular orientation of the reflector  32 , the distance from the tire and wheel assembly  22  to the camera  34  based on the optical gauge  26  can be accurately determined. In particular, as previously noted, the dimension A of the gauge piece  42  of the optical gauge  26  is known very accurately, and the distance B of  FIG. 7  from the camera  34  to the reflector  32  is likewise known very accurately, including for temperature changes. As noted, the angle C is adjustable to allow for scanning, with the angle being known very accurately. The distance D is then solved for based on real time observations of A captured by camera  34  to confirm D, which is from the top surface  50  of gauge piece  42 . In particular, the distance D is solved for based on trigonometric relationships of the light source  28 , camera  34 , reflector  32  and optical gauges  26  on wheel assembly  22 , along with the known dimension of the optical gauge  26 . The distance D is thus the distance from the optical gauge  26 , such as from the top surface  50  of gauge piece  42 , to the camera  34 , and thus represents the distance to the wheel assembly  22 . 
     It should be further appreciated that the real time observations captured by camera  34  may be provided to computer  36  for determination of the distance D, including for each optical gauge located on wheel assembly  22  to thereby determine a plane that represents the three-dimensional orientation of the wheel assembly  22  and thus the alignment of the wheel assembly  22 . Moreover, computer  36  may receive the real time observations captured by other cameras  34  at each of the wheel assemblies  22  of vehicle  24 . It should be appreciated that for each wheel assembly  22  there may be a single light source  28 , reflector  32  and camera  34 , or there may be multiple of one or more of these components at each wheel assembly  22 . 
     In a further aspect of the present invention, the noted computer readable code  48  may be used for various aspects related to the process and method for determining alignment. For example, the code  48  may be read, such as via camera  34  and by computer  36 , such as via reflected light  35 , where the code  48  must first be read prior to enabling the distance D to be solved, where the code  48  may provide confirmation that it is an authentic optical gauge  26  provided for use in connection with system  20 , such as provided by the manufacturer of system  20 . The code  48  may thus serve as a tool or code to unlock or enable use of the software within computer  36 , such as the trigonometric based software code used to solve for D and/or determine the alignment of the wheel assembly  22 . Moreover, each optical gauge  26  may have its own unique code that is configured to enable a single use of the optical gauge  26 . In this way, for example, a vehicle  22  having four wheel assemblies  22  and utilizing three optical gauges  26  per wheel assembly  22  would use twelve individual optical gauges  26  for use in determining the alignment of each of the wheel assemblies  22  of the vehicle  22 . The single use may include, for example, determinations of alignment during an alignment setting process at a vehicle repair shop. Subsequent alignment determinations, such as for another vehicle, may then require the use of new optical gauges  26 . 
     Referring now to  FIG. 8 , another embodiment of a system  120  for measuring and/or determining the alignment of a wheel assembly  22  of a vehicle  24  is disclosed, where system  120  shares similarities with system  20  with similar features being identified with similar reference numerals, but with “100” added to the reference numerals of system  120 . Due to the similarities, not all of the features and functions of system  120  will be discussed herein. 
     System  120  includes multiple optical gauges  126  supported on a mounting base or sheet  146  that is applied to and over the outer face of the wheel  56  of the wheel assembly  22 , where in the illustrated embodiment the mounting base  146  is configured as a larger mastic tape sheet that can be affixed to the wheel  56 . In like manner to system  20 , a light projector  28  projects light  30  at an adjustable reflector  32  to direct the projected light  30  onto the optical gauges  126 , and a camera or digital imager  34  images the light  35  reflected off the optical gauges  26  from the projected light  30  (see  FIG. 1 ). The adhesive mounting sheet  146  thereby functions as both a protective layer to inhibit damage to the wheel  56  of the wheel assembly  22 , which is advantageous in that vehicles  24  may often be provided with expensive wheels  56  that are desirably to be protected from damage during repair and/or maintenance operations, as well as functions to place the optical gauges  126  into a controlled orientation for use in determining the alignment orientation of the wheel assembly  22 . 
     In the illustrated embodiment, optical gauges  126  have accurately known dimensions and the reflector  32  is configured as a micro-electro-mechanical system (“MEMS”) reflector or mirror such as to enable scanning of the optical gauges  126  on the wheel  56  of the tire and wheel assembly  22 . Optical gauges  126  include a substrate  144  and a gauge piece  142 . As with optical gauges  26 , based on the known dimensions of the gauge piece  142 , as well as the known orientations of the light projector  28  and camera  34  to the reflector  32 , and the known angular orientation of the reflector  32 , the distance from the tire and wheel assembly  22 , and in particular the wheel  56 , to the camera  34  based on the optical gauges  126  can be accurately determined. In the illustrated embodiment three optical gauges  126  are disposed on the mounting sheet  146  such that by determining the distance to the multiple optical gauges  126  thereon a plane can be determined that represents the three-dimensional orientation of the wheel  56  and thus the wheel assembly  22 , which in turn corresponds to the alignment of the wheel assembly  22 . It should be appreciated that an adhesive mounting sheet  146  may be applied to each wheel  56  of the tire and wheel assemblies  22  of vehicle  24 , and that more than three optical gauges  126  may be disposed on a given mounting sheet  146 . Still further, mounting sheet  146  may include a computer readable code  148  that is imaged by camera  34  and/or read by controller  36  to enable use of the alignment determination software, such as to enable for a single use of the alignment determination software, whereby a new mounting sheet  146  supporting new optical gauges must be used for each wheel assembly  22 . 
     In a particular embodiment a machine or assembly  160  is provided for applying the mounting sheet  146  to the wheel  56  of the wheel assembly  22 . In such an embodiment the machine  160  is configured to apply mounting sheets  146  to each wheel  56 , where the mounting sheets  146  may be individual mounting sheets  146  or may be a roll of multiple mounting sheets  146 . The mounting sheets  146  may include mastic or an adhesive over an entire undersurface or just on portions, such as at or on an outer perimeter portion of the undersurface of mounting sheet  146 . 
     Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the present invention which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.