Patent Publication Number: US-2022237821-A1

Title: Method and Apparatus For Placement of ADAS Fixtures During Vehicle Inspection and Service

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of, and claims priority from, co-pending U.S. patent application Ser. No. 17/147,896 filed on Jan. 13, 2021, which in turn is a divisional of U.S. patent application Ser. No. 16/538,245 filed on Aug. 12, 2019, now U.S. Pat. No. 11,145,084 B2, which in turn claimed priority to U.S. Provisional Patent Application Ser. No. 62/725,023 filed on Aug. 30, 2018. Each of the aforementioned applications and patent are herein incorporated by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present application is related to a fixture for facilitating the calibration and alignment of vehicle safety system sensors, and in particular, to a movable fixture supporting vehicle wheel alignment system imaging sensors and for facilitating proper placement of at least one calibration or alignment target associated with a vehicle safety system sensor in operative proximity to a vehicle undergoing a service or inspection. 
     Vehicle wheel measurement systems, such as wheel alignment or inspection systems employing machine vision technology, such as cameras observing optical targets mounted on various surfaces within associated fields of view are well known in the vehicle measurement, alignment, and inspection industry. Typically, these types of systems employ multiple cameras, mounted to a crossbeam member on a fixture or structure located in front of a vehicle service area. The cameras are oriented such that each wheel of a vehicle to be inspected (or target mounted thereon) within the service area is visible to at least one of the cameras. The structure supporting the camera crossbeam may be fixed in place, or may be mobile, configured to be moved from one service area to another as needed. The camera crossbeam itself may be vertically (and/or rotationally) adjustable to accommodate vehicles at different elevations of a lift rack within the vehicle service. Images acquired by the cameras are conveyed to a wheel alignment processing system configured with suitable software instructions for image evaluation, determining various spatial measurements associated with the observed surfaces, and ultimately for identifying vehicle wheel alignment angles from associated spatial measurements. 
     When it is necessary to realign or recalibrate various vehicle safety system sensors, such as radar units or optical sensors typically utilized in forward collision avoidance systems or adaptive cruise control systems, specialized structures are precisely positioned in proximity to the vehicle, often with the aid of a vehicle measurement system such as a wheel alignment or inspection system. For example, U.S. Pat. No. 7,382,913 B2 to Dorrance describes a method and apparatus for guiding placement of a vehicle service apparatus relative to a vehicle, based on measurements acquired by a separate vehicle wheel alignment measurement system. Other techniques for guiding placement of a specialized structure relative to a vehicle undergoing a realignment or recalibration of a vehicle safety system sensor include the use of laser emitters and leveling devices, such as shown in U.S. Pat. No. 6,583,868 B2 to Hopfenmuller. 
     Positionable fixtures or support structures capable of supporting both the cameras associated with a vehicle measurement system as well as specialized structures required for realignment or recalibration of onboard vehicle safety system sensor, such as shown in Published International Patent Application No. WO 2018/067354 A1 to  Hunter Engineering Company  have been developed, thereby reducing the total number of fixtures required to complete a vehicle onboard sensor realignment or recalibration, and eliminating potential spatial conflicts between support structures and specialized structures. 
     However, some specialized structures or optical targets used in the alignment or calibration of onboard vehicle safety system sensors cannot be secured to the positionable fixture or support structure. Accordingly, there is a need to provide a system to guide an operator in the proper placement of those specialized support structures or optical targets relative to either the vehicle undergoing service or to the positionable fixture or support structure itself. In some cases, the operator may require guidance as to the proper placement of the positionable fixture or support structure itself. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly stated, the present disclosure sets forth a fixture or support structure having a vertical element supporting a set of cameras associated with a vehicle measurement system, together with at least one gimbaled guidance system disposed to project visible indicia onto surfaces in proximity to the fixture or support structure for guiding relative placement of vehicle service components. A camera crossbeam carried by the fixture or support structure locates the set of cameras in a laterally spaced arrangement, as required to view wheels on each side of a vehicle undergoing measurement, wheel alignment, or inspection, and is optionally vertically (and/or rotationally) adjustable to accommodate the vehicle disposed at different elevations on an adjustable lift rack. The gimbaled guidance system is carried by the camera crossbeam structure, and is operatively coupled to a processing system configured with software instructions to selectively control an orientation of the gimbaled guidance system about one or more axis of rotation, enabling projection of visible indicia onto surfaces at selected locations relative to the vehicle or the support structure. 
     In a further embodiment, the present disclosure sets forth a fixture or support structure having a vertical element supporting a set of cameras associated with a vehicle measurement system, together with at least one gimbaled measurement system disposed to acquire data associated with surfaces in proximity to the fixture or support structure for guiding relative placement of vehicle service components. A camera crossbeam carried by the fixture or support structure locates the set of cameras in a laterally spaced arrangement, as required to view wheels on each side of a vehicle undergoing measurement, wheel alignment, or inspection, and is optionally vertically (and/or rotationally) adjustable to accommodate the vehicle disposed at different elevations on an adjustable lift rack. The gimbaled measurement system is carried by the camera crossbeam structure, and is operatively coupled to a processing system configured with software instructions to selectively control an orientation of the gimbaled measurement system about one or more axis of rotation, enabling acquisition of images from either a camera having a field of view oriented parallel to one of the axis of rotation, or distance measurements along a measurement axis aligned with one of the axis of rotation to surfaces at selected locations relative to the vehicle or the support structure. 
     In a method of the present disclosure, proper placement of vehicle service fixtures relative to a vehicle undergoing service or inspection can be verified by: (1) establishing a location of the vehicle within a vehicle reference frame; (2) identifying a placement location for the vehicle service fixture relative to the vehicle within the vehicle frame of reference; (3) directing an operator to position the vehicle service fixture at the identified placement location; (4) orienting a field of view of a movable camera to acquire an image of the identified placement location, where the camera has a known position and orientation within the vehicle frame of reference; and (5) evaluating the acquired image to identify a presence or an absence of the vehicle service fixture. 
     In an alternative method, proper placement of vehicle service fixtures relative to a vehicle undergoing service or inspection can be verified after placement of the fixture by an operator by: (1) orienting a measurement axis of a movable range sensor towards an expected location of a surface on the vehicle service fixture, wherein the movable range sensor disposed at a known position within a vehicle frame of reference; (2) acquiring a distance measurement to a surface on the measurement axis; (3) evaluating the acquired distance measurement to identify a presence or an absence of the vehicle service fixture at the identified placement location; and (4) responsive to an identified presence of the vehicle service fixture, comparing the acquired distance measurement with an expected distance measurement based on a known position of the movable sensor and the identified placement location, to determine if the vehicle service fixture is properly positioned at the identified location to within an acceptable tolerance. 
     In a further method, the present disclosure sets forth a procedure to facilitate a proper placement of vehicle service fixtures without interference with a machine-vision vehicle inspection system normally positioned in front of the vehicle. With the vehicle positioned in a service area, and the vehicle inspection system initially disposed in front of the vehicle, the vehicle inspection system is operated to acquire a set of vehicle measurements from at least one wheel assembly on each lateral side of said vehicle, and to establish a vehicle frame of reference and/or a vehicle reference line from the acquired set of vehicle measurements. A first location of the vehicle inspection system relative to a visible reference point within the vehicle frame of reference having a determinable relationship with the vehicle is identified. To provide an unobstructed line of sight between the vehicle and a vehicle service fixture placement location within the vehicle service area in front of the vehicle, the vehicle inspection system is repositioned to a second location while maintaining the visible reference point within a field of view of at least one camera module, enabling the vehicle inspection system to identify the new location within said vehicle frame of reference relative to the visible reference point. Once repositioned, the vehicle inspection system is operated to provide a visual identification of the placement location for the vehicle service fixture within the vehicle frame of reference utilizing the identified second location and the vehicle reference line. 
     The foregoing features, and advantages set forth in the present disclosure as well as presently preferred embodiments will become more apparent from the reading of the following description in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the accompanying drawings which form part of the specification: 
         FIG. 1  is a perspective view of a prior art camera and a target support structure coupled to a control console; 
         FIG. 2  is a top plan view of the prior art support structure of  FIG. 1  disposed in proximity to a vehicle undergoing a measurement, inspection, or wheel alignment service; 
         FIG. 3  is a side view of the prior art support structure of  FIG. 1 ; 
         FIG. 4  is a perspective view of an embodiment of the present disclosure, illustrating a support structure configured with a pair of gimbal-mounted projection systems; 
         FIG. 5  is a close-up perspective view of a gimbal-mounted projection system of 
         FIG. 4  mounted to the support structure; 
         FIG. 6  is a front perspective view of an alternate gimbal-mounted projection and measurement system; 
         FIG. 7  is a rear perspective view of the gimbal-mounted projection and measurement system of  FIG. 6 ; 
         FIG. 8  is a top plan view illustrating visible indicia projected with optical projectors coupled to the gimbal-mounted guidance system of  FIG. 5 ; and 
         FIG. 9  is a top plan view illustrating a repositioning of the target support structure during a vehicle measurement, inspection, or wheel alignment service. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. It is to be understood that the drawings are for illustrating the concepts set forth in the present disclosure and are not to scale. 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. 
     DETAILED DESCRIPTION 
     The following detailed description illustrates the invention by way of example and not by way of limitation. The description enables one skilled in the art to make and use the present disclosure, and describes several embodiments, adaptations, variations, alternatives, and uses of the present disclosure, including what is presently believed to be the best mode of carrying out the present disclosure. 
     While the present disclosure sets for various embodiments in which cameras, laser emitters, range finders, etc., are disposed on a movable fixture or support structure for observing, illuminating, and measuring surfaces and/or other fixtures in proximity to the movable fixture or support structure, it will be understood by one of ordinary skill in the art that the relationships may be reversed without departing from the scope of the inventions, such that the cameras, laser emitters, range finders, etc., are disposed on the other fixtures and utilized to observe, illuminate, or measure distances to the movable fixture or support structure. 
     Turning to the figures, and to  FIGS. 1-3  in particular, a vehicle measurement system instrumentation fixture or support structure  100  is shown, having a vertical column  102  supporting a set of laterally spaced camera modules  104   a ,  104   b  associated with a vehicle measurement system, such as a vehicle wheel alignment or inspection system. At least one vehicle calibration assistance structure, consisting of a specialized target structure  400   a ,  400   b  is coupled to the support structure  100  and utilized to facilitate a process for realigning or recalibrating one or more safety system sensors onboard a vehicle  10  undergoing a service procedure in proximity to the support structure  100 . 
     A camera crossbeam  106  carried by the vertical column  102  on the support structure  100  locates the set of camera modules  104   a ,  104   b  adjacent opposite longitudinal ends. Each camera module contains one or more fixed cameras  105  with fields of view oriented in a generally forward direction to observe each lateral side of the vehicle  10  undergoing service. The camera crossbeam  106  is optionally vertically (and/or rotationally about its longitudinal axis) adjustable relative to the vertical column  102  to accommodate elevation changes in the vehicle  10  if it is located on an adjustable lift rack (not shown), or to accommodate changes in the placement of the support structure  100  relative to the vehicle  10 . Vertical and/or rotational adjustments to the camera crossbeam  106  may be manual or automatic, by any conventional means, such as sliding rails, rod and screw mechanisms, pulley mechanism, etc. As an alternative to rotationally adjusting the camera crossbeam  106 , individual camera modules  104   a ,  104   b  may be configured with suitable coupling mechanisms to permit multi-axis independent movement as required to achieve desired fields of view with the cameras  105 , and to facilitate positioning targets in proper locations. 
     It will be recognized that while the embodiments of the vehicle measurement system instrumentation structure illustrated in the Figures and described above utilize a vertical column  102  and a camera crossbeam  106 , other configurations of a camera support structure  100  may be utilized without departing from the scope of the present invention. For example, in place of the vertical column  102  and camera crossbeam  106 , a camera support structure  100  may consist of articulated camera support arms adapted to position individual cameras in laterally spaced arrangements as required to achieve the fields of view necessary to observe features or targets associated with a vehicle undergoing a wheel alignment service, measurement, or inspection. 
     The camera modules  104   a ,  104   b  are operatively coupled to a processing system  300 , which may be disposed in an associated console  302  in proximity to the fixture or support structure  100 . The processing system  300  is configured with suitable logic circuit components and with software instructions for receiving image data from the camera modules  104   a ,  104   b , evaluating the image data from at least one of the camera module to identify relative spatial positions of observed surfaces, such as optical targets disposed on the wheels  12  or surfaces of a vehicle  10 , for performing spatial transformations between various individual frames of reference, and for computing associated vehicle characteristics, such as wheel alignment angles or vehicle body position. It will be understood that the configuration of the processing system  300 , camera modules  104   a ,  104   b , and console  302  are generally known in the art of machine vision vehicle wheel alignment systems, and may vary from the specific configuration described herein without departing from the scope of the invention, so long as the processing system  300  is capable of determining at least the relative spatial position of one or more observed surfaces associated with the vehicle  10 . 
     To facilitate alignment and calibration of safety system sensors onboard a vehicle  10 , such as radar, LIDAR or optical sensors, one embodiment of the vehicle calibration assistance structure  100  includes at least one target structure  400   a  and/or  400   b  affixed to the camera support structure  100 , such as to the vertical column  102  or camera crossbeam  106 , by a multi-axis mounting fixture  402 . Each target structure  400   a ,  400   b  includes an observable target face oriented in a generally forward direction from the fixture or support structure  100  (i.e., towards the vehicle service area), at an elevation generally suitable for observation by the safety system sensors onboard the vehicle  10  during a realignment or recalibration procedure. The specific configuration of the target structures  400   a ,  400   b , such as the target face features, is related to, and will vary with, the specific type of safety system sensor for which it will be used. For example, an optical target  400   a  having retro-reflective or contrasting target face surface features may be provided for use with optical safety system sensors such as cameras or LIDAR. Correspondingly, a metallic or radar-reflective target  400   b  may be provided for use with radar-based safety system sensors. As seen in the various figures, multiple individual target structures of either the same or different types, may be secured to the vertical column  102  at different vertical elevations or horizontal separations. 
     The mounting fixture  402  may be a fixed mount which secures the target structures  400   a ,  400   b  in a fixed position and orientation relative to the vertical column  102 , or optionally, may include suitable multi-axis mechanisms for adjusting the lateral position, vertical position, and/or orientation of the target structures  400   a ,  400   b  over a limited range relative to the vertical column  102 , such as may be required for safety system sensors offset from a vehicle centerline CL or thrust line TL after the fixture or support structure  100  is disposed generally in front of the vehicle, as seen in  FIG. 2 . For example, a lateral support track  404  shown in  FIGS. 1-4  may be coupled to the mounting fixture  402 , parallel to the camera crossbeam  106  to support a target structure for sliding movement, enabling a lateral position of a target structure  400   a  to be adjusted. 
     In one embodiment, to facilitate positioning of the fixture or support structure  100  generally at the vehicle centerline CL (or thrust line) and to enable the set of camera modules  104   a ,  104   b  to view features on each lateral side of the vehicle  10 , the fixture or support structure  100  is provided with a base structure  108  having a set of rolling elements, such as casters or wheels  109 . Exemplary wheels may include omni-directional wheels such as Omni wheels or Mecanum wheels having small discs around their circumference. Optionally, the wheels may be coupled to a drive motor for powered movement of the support structure  100 . During use, the fixture or support structure  100  is positioned manually by an operator, under operator control through the processing system  300 , or automatically by the processing system  300 , at a selected distance from the front of the lift rack or support surface on which the vehicle  10  is disposed during the measurement, inspection, or wheel alignment service procedure. Different vehicles may require the fixture or support structure  100  to be positioned at different locations relative to the vehicle. An optional locking mechanism may be provided on at least one of the rolling elements, to prevent accidental movement of the fixture or support structure  100  during use. 
     Precise position of the fixture or support structure  100  to place the target structure  400  in an ideal location for use may be carried out automatically or by the operator under the guidance of the processing system  300  in response to data acquired through the processing of images acquired by the camera modules  104   a ,  104   b . For example, with the fixture or support structure  100  positioned generally on the centerline CL of a vehicle  10  as seen in  FIG. 2 , (or alternatively to a determined thrust line of the vehicle) the camera modules  104   a ,  104   b  can acquire images associated with the front and rear wheels  12  on each lateral side of the vehicle, from which the processing system  300  identifies the position of the fixture or support structure relative to either a geometric centerline CL or a thrust line TL of the vehicle  10 . If adjustments to the position of the fixture or support structure  100  relative to either the vehicle&#39;s geometric centerline CL or thrust line TL are required, suitable, signals directing movement are provided to the drive motors or operator by the processing system  300  based on the determined relative position of the fixture or support structure. 
     Positioning of the fixture or support structure  100 , if adjustable, may be relative to a single axis which is generally transverse to the vehicle centerline CL (i.e., from side to side), or may be relative to an additional axis which is generally parallel to the vehicle centerline CL (i.e., towards or away from the vehicle). A vertical height of the set of the camera modules  104   a ,  104   b  is optionally adjusted by raising or lowering the camera crossbeam  106  along the vertical column  102 . 
     Once the fixture or support structure is positioned at a desired location relative to the vehicle  10 , adjustments to the position and orientation of the target structure  400   a ,  400   b  relative to the vertical column  102  for proper placement within a field of view associated with the onboard vehicle safety system sensors can be done via the mounting fixture  402 . Suitable adjustment mechanisms within the mounting fixture  402  may include, but are not limited to, ball and socket connections, pivot arms, and the sliding rail or track  404 . With the target structure  400   a ,  400   b  positioned at the desired location relative to the vehicle, and more specifically, relative to an onboard vehicle sensor, measurement, alignment, or calibration of the onboard vehicle sensor can proceed as understood in the art, by observing or illuminating the target structure  400  and responding accordingly. 
     The vehicle calibration assistance structure includes one or more optical projectors  500  operatively coupled to, and under control of, the processing system  300 , for the projection of visible indicia  501  on to surfaces in proximity to the fixture or support structure, utilized to aid in the placement or alignment of vehicle service fixtures or targets. Exemplary surfaces onto which visible indicia may be projected include the vehicle body, wheel-mounted targets, targets or locations on the service bay floor surfaces, and movable targets located within the service bay. Each optical projector  500  as illustrated in  FIGS. 5-7  comprises a pair of laser modules  500   a  and  500   b . Each laser module is mounted on a set  502  of motorized multi-axis gimbals secured to the camera cross beam  106 . The laser modules  500   a ,  500   b  are disposed in a laterally spaced arrangement on the camera cross beam  106 , in proximity to the camera modules  104   a  and  104   b , enabling projection of visible indicia onto surfaces located within the vehicle service area, such as adjacent each lateral side of the vehicle  10  as shown in  FIG. 6 . Each laser module  500   a ,  500   b , as seen in  FIG. 5 , includes at least one laser line emitter  504  secured to the set  502  of gimbal motors  503   a ,  503   b , and  503   c  for controlled rotational movement about at least two orthogonal axes (X, Y, and/or Z). 
     Optionally, as shown in  FIGS. 6 and 7 , second laser emitter  506  is supported by an outboard gimbal motor  508  on the mounting structure  502 , for rotation about a fourth additional axis R, parallel to one of the orthogonal axes (X, Y, and/or Z), enabling projected indicia or laser lines to be rotated about the projection axis. Rotating one of the projected indicia or laser lines enables the processing system  300  to visually correct for parallax distortion resulting from non-orthogonal projection orientations. The laser emitters  504  and  506  each project beams  507  of visible light through associated optical focusing elements to illuminate visible indicia in the form of spots or lines, on the surfaces. It will be recognized that the optical projectors  500  may utilized other sources of visible light, such as LED elements, and associated optical focusing elements in place of the laser emitters  504 ,  506  to project indicia visible to an operator and/or to an observing camera system, such as spots or points, or illumination of different colors, onto the surfaces without departing from the scope of the present disclosure. Furthermore, the specific number of axes about which the optical projectors  500  are configured for movement may vary based on the intended use of the projected indicia. For example, optical projectors  500  intended to project indicia at a fixed location relative to the fixture or support structure  100  may be mounted in a fixed orientation, while optical projectors such as  500   a  and  500   b  which are intended to project indicia onto surfaces at varying locations relative to either the vehicle, fixture, or reference within the service bay, are mounted for rotational movement about multiple axes. 
     During a vehicle wheel alignment service, measurement, or inspection procedure, the processing system  300  is configured to control the set  502  of multi-axis gimbal mounting structures, and optional outboard gimbal motor  508 , to orient each laser emitter  504 ,  506  to project the observable indicia  501  at a selected location on a surface in proximity to the fixture or support structure  100 . The observable indicia  501  is configured to represent a stationary point location to aid in the placement of a vehicle service fixture  600 , or to represent lines or boundaries against which an elongated planar optical target  602  or other vehicle service device may be aligned. The processing system  300  optionally controls the set of multi-axis gimbal mounting structures to impart motion to the projected indicia, such as to sequentially illuminate two or more discrete locations on said surface. Indicia other than points or lines, such as alphanumeric symbols, or raster images, or visible indicia of different colors, may be projected under control of the processing system  300  from suitably configured optical projectors  500  within the scope of the present disclosure. 
     In one embodiment, the selected location of the observable indicia  501  on the surface is determined by the processing system  300  in response to spatial measurements of associated with the vehicle  10  acquired from images captured by the camera modules  104 , or is selected to be relative to a component of the fixture or support structure  100 , such as an axis of the support column  102 . For example, some vehicle safety system sensor calibration procedures require the placement of target structures, observable by onboard vehicle safety system sensors, at select locations relative to the vehicle. Specific placement requirements associated with safety system calibration procedures for a variety of vehicle makes and models may be stored in a database accessible to the processing system  300 . After determining measurements associated with the relative spatial position of the vehicle  10  to the fixture or support structure  100 , such as by conventional machine vision vehicle alignment measurement procedures, the processing system  300  is configured with software instructions to access the database to recall the placement requirements for visible targets or calibrations fixtures  600  associated with the vehicle. Utilizing the recalled placement requirements, the processing system  300  operates the set  502  of motorized gimbal mounting structures to directly orient the optical projectors to project visible indicia at the appropriate locations on the floor surface of the vehicle service area, enabling an operator to place targets or structures necessary to carry out or complete a vehicle service, calibration, or inspection procedure. 
     In a further embodiment, the processing system  300  utilizes images from the camera modules  104   a ,  104   b  to observe a location of the projected visible indicia relative to the vehicle, a wheel mounted target, or other reference location visible within images captured by the camera modules. The processing system  300  is configured with software instructions to utilize the observed location to operate the set  502  of motorized gimbal mounting structures to alter an orientation of the optical projectors to adjust the location of the projected indicia from the observed location to a location required for the operator to carry out or complete a vehicle service calibration or inspection procedure. 
     In addition to operating the set of motorized gimbal mounting structures to orient the optical projectors to project the visible indicia at the selected locations on the floor surface, the processing system  300  may be further configured to provide for motion stabilization of the projected visible indicia in response to movement of the fixture or support structure  100 . Motion stabilization, via control of the set of motorized gimbal mounting structures, may be provided by the processing system  300  to maintain the projected visible indicia at the selected location during movement of the base  108  across the floor surface, as well as during vertical movement of the camera crossbeam  106 . 
     In another embodiment, the fixture or support structure  100  is configured with at least one secondary optical camera system  700  mounted to a motorized multi-axis gimbal. The optical camera system has a field of view suitable for viewing targets disposed in proximity to the vehicle  10  and/or within the vehicle service area. The motorized multi-axis gimbal incorporates rotational position encoders associated with each rotational axis, such that a spatial orientation of the secondary optical camera system field of view can be identified, tracked, and controlled by the processing system  300 . 
     Turning to  FIGS. 6 and 7 , the secondary optical camera system  700  may be supported directly on the motorized gimbal mounting structure  502  of one of the laser modules  500   a  or  500   b , aligned with a field of view parallel to an axis of one of the associated laser emitters  504  and  506 , eliminating the need for a separate motorized multi-axis gimbal dedicated to the camera system  700 . With suitable software programming instructions, the processing system  300  utilizes the secondary optical camera system to observe targets  602  within a field of view associated with the current orientation of the laser module  500   a ,  500   b  onto which the camera system  700  is mounted. Proper placement of a target relative to the secondary optical camera system  700  or other established frame of reference, such as the vehicle (based on observations of wheel adapter targets) can be determined by the processing system  300  by analyzing an observed location of the target within the camera system field of view, together with gimbal encoder data identifying a multi-axis spatial orientation of the field of view (i.e. reference frame). If necessary, the processing system  300  can drive the motorized gimbal mounting structure  502  to orient the secondary optical camera system  700  field of view as required to observe an area in proximity to a vehicle or service bay in which a target  602  is expected to be placed. If the target is not observed within the field of view following the orientation of the secondary optical camera system  700 , a warning or other suitable indication to an operator may be provided. 
     The processing system  300  may be configured with software instruction to utilize the secondary optical camera system  700  to determine if an external fixture  600  or target  602  has been properly positioned relative to a location indicated by optical projector  500  on the fixture or support structure  100 . Once the optical projector  500  is oriented to illuminate a specific point or location for placement of the external fixture  600  or target  602 , an operator moves or places the external fixture  600  or target  602  at the indicated location. Preferably, the external fixture  600  or target  602  includes a point or reference marking, such as a crosshair or bulls-eye icon, which is to be aligned with an illuminating laser from the optical projector  500 . For the processing system  300  to determine if a point of illumination from a laser module  500   a ,  500   b  is aligned with an observable reference location on the external fixture  600  or target  602 , one or more images are acquired by the secondary optical camera system  700  oriented to view the indicated location. 
     Alternatively, the external fixture  600  or target  602  may be configured with an optical receptor responsive to incident illumination. The optical receptor may be integrated into the external fixture  600  or target  602 , or may consist of a self-contained module suitable for placement on the fixture, target or other surface. In one configuration, the optical receptor is responsive to laser illumination to activate a visual indicator, such as an LED once the external fixture  600  or target  602  is properly positioned with respect to any incident laser illumination from the optical projector  500 , enabling an operator to visually confirm proper placement. 
     Configured with software instructions, the processing system  300  can analyze images of the external fixture  600  or target  602  acquired by the secondary optical camera system  700 , and confirm activation of, or a presence of, the visual indicator to verify proper positioning of the external fixture  600  or target  602 . Alternatively, the optical receptor is configured to respond to incident illumination by emitting a wireless signal or other form of suitable feedback detectable by the processing system  300 . 
     In addition to confirming proper positioning of an external fixture  600  or target  602 , a feedback system responsive to incident illumination may be utilized to facilitate position calibration of the laser modules  500   a ,  500   b  by enabling the processing system  300  to confirm that the laser modules are accurately responding to commands for orientating the illuminating lasers about each rotational axis of the motorized gimbal mounting structure  502 . The processing system  300  is configured with software instructions to drive the individual gimbal motors supporting each laser module in order to align the illuminating lasers with specific calibration targets in three dimensional space. The calibration targets may optionally be located on the fixture or support structure  100  itself, enabling a self-calibration procedure. Failure to receive appropriate responsive feedback at the processing system  300 , such as from an operator, from a visual indicator, or an emitted signal responsive to incident illumination, is an indication to the processing system  300  that the illuminating lasers are not oriented to properly illuminate the specific calibration point or reference marking. A suitable warning to an operator can be provided by the processing system  300 , indicating the need for a corrective action or recalibration. 
     In a further embodiment, a non-contact distance measurement sensor  800  is secured to the motorized gimbal  502 . The distance measurement sensor  800  may be any of a variety of suitable sensors, such as a laser range finder, a radar system, or a Lidar system, having an operating range suitable for determining distances to targets disposed in proximity to the vehicle  10  and/or within the vehicle service area. The motorized gimbal  502  incorporates rotational position encoders associated with each rotational axis, such that a spatial orientation of a measurement axis associated with the distance measurement sensor  800  can be identified, tracked, and controlled by the processing system  300 . Optionally, as seen in  FIGS. 6 and 7 , the distance measurement sensor  800 , replacing the laser  700 , may be supported directly on one of the laser modules  500   a ,  500   b . With suitable software programming instructions, the processing system  300  utilizes the distance measurement sensor  800  to locate external fixtures  600  or targets  602  within the field of view. Proper placement of a fixture  600  or target  602  relative to an established frame of reference, such as the vehicle (based on observations of wheel adapter targets) is determined by the processing system  300  in response to a measured distance to the fixture  600  or target  602 . The processing system  300  is configured to utilize gimbal encoder data for each associated rotational axis to identify a spatial orientation of the measurement axis for the measurement sensor  800 . If necessary, the processing system  300  can drive the motorized gimbal  802  to orient the measurement axis of the measurement sensor  800  towards an area in proximity to a vehicle or service bay, in which the fixture  600  or target  602  is expected to be placed. 
     In a further embodiment, use of a laser range finder or laser displacement sensor  800  functions as an additional means by which the processing system  300  can project a point of illumination onto surfaces within proximity to the fixture or support structure  100 . Utilizing the motorized gimbal  802  to orient the measurement axis of the laser displacement sensor or laser range finder  800  towards a selected location on a surface, the processing system  300  is configured to activate the laser displacement sensor or laser range finder to emit a laser beam along the oriented measurement axis, illuminating the selected location. 
     In one embodiment, the processing system  300  is configured with software instruction to utilize the measurement sensor  800  to determine if an external fixture  600  or target  602  has been properly positioned relative to a location indicated by an optical projector  500  on the fixture or support structure  100 . Once the optical projector  500  is oriented to illuminate a specific point or location for placement of the external fixture  600  or target  602 , an operator moves or places the external fixture or target at the indicated location. Next, the processing system  300  utilizes the measurement sensor  800  to measure a distance from the fixture or support structure  100  along an axis oriented towards the specific point or location at which the external target  600  or fixture  602  is expected. If the external fixture  600  or target  602  is properly positioned, the processing system will receive an expected distance measurement from the measurement sensor  800 . If the received distance measurement is outside of an acceptable tolerance of the expected measurement, the processing system  300  is configured to provide the operator with a warning or other suitable indication that the external target or fixture  550  is not disposed at the expected location, and that corrective action may be required. 
     In a further variation, the processing system  300  may be configured with software instructions to utilize the measurement sensor  800  to locate a proper location for place of an external fixture  600  or target  602  relative to either the vehicle or to the support structure  100 . By controlling the motorized multi-axis gimbal  802 , the processing system  300  can acquire distance measurement data from the measurement sensor  800  over an area or region in proximity to the vehicle or support structure  100 . Once a location at a selected distance is identified from the measurement data, the processing system  300  utilizes an optical projector  500  and motorized multi-axis gimbal  502  to provide a visible indication of the location to an operator, or simply activates the optical projector  500  if the measurement sensor  800  is mounted on a common multi-axis gimbal. 
     During a vehicle service procedure, the support structure  100  typically is disposed in front of the vehicle within the service bay. When placing an external fixture  600  or target  602  relative to either the vehicle or to the support structure  100  it may be necessary for a service technician to move the support structure  100  out of the way to provide clearance at a placement location. If an external fixture  600  or target  602  is to be placed in front of the vehicle in the service bay, such as for service or inspection of a forward-looking ADAS system on the vehicle, it may be necessary to first identify the placement location for the external fixture or target using the optical projector  500 , mark the location on the floor surface, and then move the support structure  100  to provide a clear line of sight between the vehicle and the external fixture  600  or target  602  disposed at the marked location as seen in  FIG. 9 . 
     In a further embodiment, the processing system  300  is configured with software instructions to eliminate the need for a service technician to mark the floor location prior to moving the support structure  100 , and to enable the camera modules  104   a ,  104   b  to continue to acquire useful data after the support structure  100  is moved to a new location within the service bay relative to the vehicle  100 . Initially, with the support structure located at a starting position at the front of the vehicle, the processing system  300  utilizes the camera modules  104   a ,  104   b  to acquire images of optical targets T mounted to the vehicle from which a vehicle thrust line and a rear axle coordinate system (frame of reference) are determined as is conventional with a machine-vision vehicle alignment or inspection system. Optionally, a fixed optical target associated with a surface of the vehicle service area, such as a wall, ceiling, or other stationary structure is observed as well. 
     Next, the support structure  100  is repositioned, as seen in  FIG. 9 , off to one side of the vehicle, while maintaining at least one of the vehicle-mounted optical targets T (or an optional fixed optical target) in a field of view of at least one of the camera modules  104   a ,  104   b . Using the initially determined vehicle thrust line and rear axle coordinate system data (or other established reference), the processing system  300  is configured with software instructions to determine the new position of the support structure  100  relative to the vehicle using only images of a single visible vehicle-mounted optical target T (or optional fixed optical target). For example, the camera modules  104   a  normally viewing the front driver side of the vehicle may now acquire images of an optical target T mounted to a rear wheel. So long as at least one optical target remains visible, the processing system  300  can acquire sufficient information from which to determine the relative positions of the vehicle and the support structure  100  in a common spatial reference system using well understood coordinate transform algorithms. With the relative positions known (or determinable), the processing system  300  operates the set  502  of motorized gimbal mounting structures to orient one or both of the optical projectors  500   a ,  500   b  to project visible indicia at the appropriate locations on the floor surface of the vehicle service area for fixture  600  or target  602  placement, including floor surface locations previously occupied or obstructed by the support structure  100 , enabling an operator to carry out or complete a vehicle service, calibration, or inspection procedure as noted above. 
     The relative position of the support structure  100  to the vehicle (or other fixed reference point) may alternatively be determined or tracked by utilizing a suitable movement tracking system, such as laser or optical sensors (similar to computer mouse) located in the base support structure, or an inertial tracking system within the support structure  100 . A movement tracking system enables relative movement of the support structure  100  to be monitored when the vehicle wheel targets T or other fixed reference point are not visible to the camera modules  104   a ,  104   b.    
     For many vehicle inspection, service, or alignment adjustment procedures, it is beneficial (or required) to have the vehicle disposed on a level surface. When placing external fixture  600  or targets  602  in proximity to the vehicle, it is assumed that the fixtures or targets will be disposed on the same level surface as the vehicle. However, in most vehicle service shops, the floor surfaces of the vehicle inspection bays are not uniformly level. When a vehicle inspection, service, or alignment procedure requires that an external fixture  600  or target  602  be disposed at a distance from the vehicle, errors or miscalculations in measurements may be introduced by uneven or un-level conditions in the service bay floor. 
     Establishing a horizontal reference plane can aid in the placement of external fixtures  600  or targets  602  facilitates the inspection, service, or alignment of a vehicle when floor conditions are less than ideal. In an embodiment of the present disclosure, a laser projection system  850  disposed on the support structure  100 , as seen in  FIG. 4 , is configured to establish a reference plane at a selected height relative to the vehicle. The laser projection system  850  may consist of a rotating laser or fan laser mounted to the support structure  100  at either a fixed or vertically adjustable location and aligned to project the laser in a horizontal plane. Alternatively, one of the gimbal mounted laser emitters on an optical projector  500   a  or  500   b  may be driven by the processing system  300  in a reciprocating or rotating movement about one axis of the gimbal structure to project a laser in a horizontal plane. the placement of the optical projectors  500   a ,  500   b  on the support structure  100  establishes a reference plane at a known vertical distance relative to the camera modules  104   a ,  104   b . Once placed on the floor, the vertical height of the external fixtures  600  or targets  602  can be adjusted relative to the established reference plane, rather than the uneven floor, such as by aligning index markings on the fixtures or targets with the rotating laser or fan laser illumination, or by guided adjustment in response to feedback provided by the processing system  300  based on observations of the fixtures  600  or target  602 . 
     It will be further recognized that the establishment of a horizontal reference plane may be carried out prior to vehicle measurement or inspection, and utilized to characterize the contours of the floor surface of the vehicle service bay during a set up or calibration process. With the horizontal reference plane established, an external fixture  600  or target  602  is moved about the vehicle service bay to various locations. At each location, the position of the fixture  600  or target  602  relative to the vertical height of the horizontal reference plane is identified, effectively mapping a displacement between the floor surface and the reference plane at each location. Granularity of the mapping is directly connected to the number of locations at which the fixture  600  or target  602  is positioned. Once the floor surface is characterized, during a vehicle service or inspection procedure, appropriate measurement offsets or corrective values can be applied to measurements acquired from the vehicle wheels, targets  602 , or fixtures  600  based on an associated location on the characterized floor surface. 
     The present disclosure can be embodied in-part in the form of computer-implemented processes and apparatuses for practicing those processes. The present disclosure can also be embodied in-part in the form of computer program code containing instructions embodied in tangible media, or another computer readable non-transitory storage medium, wherein, when the computer program code is loaded into, and executed by, an electronic device such as a computer, micro-processor or logic circuit, the device becomes an apparatus for practicing the present disclosure. 
     The present disclosure can also be embodied in-part in the form of computer program code, for example, whether stored in a non-transitory storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the present disclosure. When implemented in a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits. 
     As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.