Auto3D: Inspection of V-stay
SINTEF and Tordivel AS are currently collaborating with the development of a system for fully automatic inspection of the 3D geometry of objects.
Our ambition has been to create a 3D vision system based on low-cost, off-the-shelf components that is able to acquire 3D point clouds of objects at regular intervals directly in the production line. The system should be applicable for inspection of 100% of the production. This means that the entire process of digitization and subsequent extraction of physical parameters from the point clouds needs to be carried out within a timeframe of very few seconds, and without intervention from an operator.
Left: Measurement cell for automotive V-stay based on structured light. Right: Result of a measurement, with cylinders fitted to each of the steel tubes.
The idea is to divide the measurement into two phases, where the first manual phase consists of a specification of all the parameters that should be measured and the second phase carries out the actual measurements. The specification of the measurements needs only to be performed once, typically when the system is configured for a new measurement task.
For our system, the specification of the measurements is aided by an intuitive user interface and it contains set of standard tools to perform typical measurement tasks, such as tools for fitting and characterizing geometric primitives (e.g., cylinders, spheres and planes) and tools for finding relationships between said primitives, such as distances and angles. The configuration of the system is an easy task, and it can be performed by factory personell without in-depth knowledge within image processing or 3D data analysis.
Through collaboration with the Norwegian car part manufacturer Kongsberg Automotive, a measurement cell for inspection of a V-shaped car component has been developed. The car component consists of two steel pipes attached to a central housing with two additional housings clamped to its ends. The result of a measurement is an ordered point cloud with 1.2 million 3D points. The software is configured to fit cylinders to each of the steel pipes as well as to the inside of the housings of the car part. The size, position and orientation of the fitted cylinders allow us to measure and verify a series of dimensions specified on the CAD drawing of the component.
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For more information, contact Øystein Skotheim
