Position determination of car parts in 6 degrees of freedom

Measuring points of a motor vehicle side frame for reception by a robot

In car body construction, various parts such as doors, trunk lids, side parts etc. are removed from specially manufactured containers. In this process, certain requirements are placed on the mechanical tolerances in order to remove the components correctly. If the component position changes, the robot movement must be corrected accordingly. A 3D image processing system in an automobile manufacturer's joining and welding line demonstrates how this can be done quickly and economically in an automatic process.

Using an image processing system, the removal position of side frames in special containers is dynamically adapted to the current three-dimensional position (6 degrees of freedom) of the component. The standard cameras and lighting are integrated in the gripper. Three unique features are required on the component, which are taught in with the aid of an adjustment function and then used for localization. Each of the features can move in a search window of approx. 100 x 100 x 100 mm. The new component position is calculated from the calibration data and the two-dimensional features and transferred to the robot. An accuracy of approx. +/- 0.5 mm is achieved.

Disturbances caused by slipped parts or inaccurately placed containers are eliminated. The system can be used for a large number of very different parts. A concrete application can be realised by a mechanical engineering company alone using the guideline. No special calibration bodies are required for the system. The cameras are calibrated fully automatically on a real component, complex calculations or measurements are not necessary for the system integrator. If the camera is replaced or the position is changed, only a menu-guided rough adjustment of the cameras with subsequent automatic calibration run is required.

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