Industrial vision systems are used to solve a variety of applications in various manufacturing sectors.
One application is counting tires moving down a conveyor. In fact, vision systems offer more than just one way to complete the task. One way would use cameras and fluorescent lights while the other would incorporate a line scan laser. The best method depends on the application and the task to be completed.
The economical way—for a simple production count
The most economical way would involve placing one or two stationary cameras above the tires along with some fluorescent panels for lighting.
This application uses a technology known as blob detection and analysis to check the shape of an object—in this case, our tires. The vision system software looks for the difference in light and dark pixels that form areas, or blobs, of the tires, as defined by the software when it was set up. You can limit a minimum number of light or dark pixels for each blob to count as well as the maximum number of pixels and ignore everything else that doesn’t fall within that range and color.
For example, as the tires move down the conveyor, there may be a partial tire in the field of view. This could cause the tire to be counted more than once, once in the first field of view and once again in the next view. But this situation can be covered during set up.
The vision system can be set so that a minimum number of pixels is set above 50% of the smallest tire being counted, assuming the tire sizes don't vary that much. By having the maximum number of pixels above 50%, it can be assured that the partial tire(s) is only counted once.
This type of system could be used for a simple production count or it could be used to vary the speed of the conveyor based on how much product is moving to the next process. If the tires are in a single row the system could also be used to sort different sizes.
The vision system is normally triggered from the conveyor by a proximity switch so that the field of view doesn’t overlap. In most cases the conveyor would be continuous and not indexed. You can increase the conveyor speed on this type of system, but it depends on the type of processor the vision system is using and the camera resolution.
When you require more detail
Another way of counting tires with an indexed conveyor or slower moving conveyor is to use a line scan laser to create a point cloud image of the tires and send it to the vision software. This would be used more in an application where you need more detail about the tire being counted. This method is more expensive and needs to be engineered for the demands of the application.