Plan a vision future
Jon Titus, Contributing Technical Editor -- Test & Measurement World, 12/1/2004
Often, vision-system developers design inspection stations as stand-alone systems that simply report an accept/reject condition. Some systems may move defective parts to a reject bin, but that's the extent of their interaction with other test or production gear. In many cases, that's all management will pay for. Soon, though, business needs will demand more inspection information, more control over what gets inspected, new inspection capabilities, and so on. Without laying the groundwork for these expanded requirements, companies may have to build entirely new inspection systems, which can bust a budget—and limit careers.
Careful planning requires analysis of hardware and software needs. On the hardware side, plan to add extra cameras, and expect new cameras to operate faster, transmit more pixels per image, produce color images, and read 2-D matrix codes. Instead of looking at cameras that come with proprietary or slow interfaces, choose ones that connect to a host controller through FireWire (IEEE 1394), USB, Camera Link, or another standard connection. Then, as camera requirements change, you can continue to use the same hardware to acquire images and control cameras, lights, and other devices.
Standards apply to host controllers, too. A standard bus such as PCI, PCI Express, cPCI, or PXI offers built-in flexibility and longevity. When you must add motion controllers, data-acquisition channels, and I/O ports, you'll find many suppliers of boards for these standard buses. Just make sure the manufacturers include drivers that comply with the VISA and IVI specs.
As you evaluate standard buses, also investigate communication connections. These days, an inspection system must provide an Ethernet port, and application software must include routines that can transmit data to end users and databases.
Developers who plan to put vision systems on production lines may need to ensure their systems can communicate with industrial machines that use Fieldbus signals and protocols. Manufacturing engineers may want production equipment to receive inspection results and adjust manufacturing processes to decrease rejects. If a vision system's host controller doesn't offer Fieldbus connections, it should let you add them later. In the meantime, "bridges" can convert one bus to another, say USB to CAN, and vice versa.
Because programming tools come and go, software also deserves attention. Just ask people who have written Visual Basic 6 code and now face abandonment by Microsoft. Vision systems can last for 10 or more years, and so should their program-development tools. Seek software companies that have exhibited a commitment to long-term support and have a solid following of developers and system integrators. Vision-software libraries should include routines that adapt to changes such as higher pixel counts, color images, and so on. And as new image-processing algorithms come into use, they should easily drop into your existing application code.
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