It is often necessary to repair the frame or other parts of a vehicle after the vehicle has been in a collision or accident that has bent or otherwise damaged the vehicle frame or other parts of the vehicle. In the U.S., such repair is commonly accomplished by securing the vehicle on a frame-straightening bench and exerting appropriate forces, at appropriate locations, in appropriate directions to bend the frame back into its normal position. However, bending the frame in this manner is not always possible or recommended, such as when the frame is constructed of aluminum rather than steel.
In Europe, repairs are commonly accomplished by removing and replacing the damaged part or portion of the frame rather than bending it. This requires the vehicle to be secured to a bench, and then the replacement portion is positioned and secured during the repair using appropriate fixtures. Unfortunately, the process of replacing a vehicle's frame can be laborious and time-consuming, particularly with regard to separating the body from the damaged frame and mounting the body onto the undamaged frame.
While the straightening machines are highly effective, they do not by themselves provide information as to the extent of straightening to be accomplished. The vehicles have manufacturer-provided reference points, such as reference openings or holes located at established points on the vehicles. Manufacturers also provide specifications for the correct three-dimensional spatial locations of these reference points relative to each other. If a vehicle is damaged, these reference points may be moved from their normal or “specification” positions relative to each other. Most, if not all, vehicle frame and unibody straightening jobs require that the vehicle reference points be returned to within manufacturer specifications.
In other repair systems, the dimensions of the vehicle's frame are measured and compared to pre-established standard (i.e., undamaged) dimensions, and, as necessary, the frame is adjusted on a frame-straightening machine until the measured dimensions correspond to the standard dimensions. In one system, for example, a laser scanner is positioned beneath the vehicle, and retro-reflective targets are hung from points on the frame. The laser scanner uses lasers to triangulate the positions of the targets and determine the width and length dimensions. Each target presents a bar code which specifically identifies it, and from which the laser scanner can extract the height dimension.
Unfortunately, each type of repair systems suffers drawbacks. In the fixture system, there is no verification that the fixtures themselves are in the proper positions, and thus, the vehicle may be straightened, or parts may be added, based on inexact coordinates, resulting in a faulty repair. Even the laser scanner may result in inaccurate measurements. Specifically, the accuracy of the triangulation calculation decreases with the square of the distance from the scanner, thereby limiting the range of the system to no more than a few meters.