Cognex vision positioning replaces traditional mechanical or gravity centering
BMW Brilliance Automotive Co., ltd devotes itself to being the most successful premium automobile manufacturer, and lead development of top gear automobile market in China. The company insists on bringing the latest products and the most advanced technology into China. By introducing the automatic stamping line of ABB and Cognex steel plate vision location and testing system, the company not only improves the quality of products, but also enhances productivity.
Optimize production process by visual location tools
The positioning process of automotive steel sheet, gravity centering and mechanical centering, both of them have the same problems. First, the appearance of product may be left blemishes which will affect quality by gravity and cylinder pat; second, the production line is affected by gravity and mechanical lapping; third, the cost is high. Visual location solves these problems easily. First, visual location is a kind of non-contacting locating way. It is installed above the conveyor belt, by this, it avoids affecting quality resulted from increasing external forces; second, the time is controlled within 500 milliseconds from taking photos and processing images to providing the coordinate information to the robot; third, comparing with the traditional locating method, visual location costs less, but more stable and more precise.
Steel plate location system is able to switch over to corresponding JOB by the analysis of visual pattern matching tools. For wide view products (maximum 3-4 meters) and different kinds of materials, steel visual
System Testing Process：
(1) After being conveyed to the predetermined position, PLC sends position signal to the robot, then the robot send trigger photo signal to visual system through Ethernet;
(2) Visual system received the trigger signal, then take photo and process it, and calculate the coordinate information (abscissa, ordinate, angle of deflection);
(3) Visual system send the coordinate information of product (horizontal offset, vertical offset and angle of deflection) to the robot through Ethemet;
(4) According to the location offset information of product, the robot adjusts its gesture to grab the product and puts it to the designated spot;
(5) After this process finished, the robot goes back to the waiting spot to wait for the next signal.
Cognex Pattern Matching Technology
The first step of every machine vision application-also the key step to success-is to locate the object in the view of visual camera--this process is called pattern matching.
Sometimes pattern matching is very difficult because of that too many variables can affect the display mode of objects in visual system. Traditional pattern matching technology is based on pixel grid analysis process which is called normalized correlation. This way fixes X/Y location of things by looking for the statistics similarity between gray level-or graphic benchmark-and other parts of picture.
This method is effective in certain situations, but when the appearance of production line changes frequently (such as the angle, size and shape of objects), its ability and accuracy of locating objects will be restricted.
To overcome these limits, Cognex developed the geometric pattern matching technology which is called PatMax. By this technology, geometric shape of the objects can be obtained by boundary curves which is not depended on pixel grid. Then it can search for the similar shape in the pictures, this skill is not limited by specific gray level. So you can find this object precisely no matter how its angle, size or shape changes. It improves the service ability of this technology fundamentally.
As the gold standard of the industry artifacts and feature location, PatMax® can provide accurate and repeatable test under the toughest conditions. PatMax technology was developed by patent certification for the first time in 1997 as the first high accuracy, high speed and high throughput object positioning technology in machine vision field. It is the most useful technology in pattern matching and detection.
PatMax is reliable and correct in locating workpieces by advanced geometric pattern matching technology. Even under the most extreme conditions, PatMax is able to reduce tremendously or totally eliminate the fixed requirements and cost. For locating workpieces or features, PatMax is a tool with the largest visual inspection capacity and highest reliability in visual system.