For several years, the cost of machine vision systems tumbled faster than the stock market. Prices dropped from hundreds of thousands of dollars per system to tens of thousands per system to near-$1,000 prices. Today, you can buy vision systems as a commercial off-the-shelf (COTS) product. Vision systems are rapidly becoming commodities, much like programmable controllers, limit switches and computers.
The big question is whether COTS systems are suitable for machine vision applications. Can a COTS system perform with the needed speed and performance required by fast-moving production lines? Or do machine builders still need special systems designed for speed, performance and reliability?
For our purposes, let’s define a COTS vision system as something that is available, more or less, on an off-the-shelf basis. That is, you call a vendor, you order a system, and it ships in a few days.
Make vs. Buy
Concept Systems, a system integrator in Albany, Ore., decided custom engineering vision systems into every application no longer made sense. “We evaluated all the major vision providers, plumbed the depth of our capabilities, and determined that rolling our own vision system really didn’t make sense from a financial standpoint, as well as an inventory and support standpoint,” says Doug Taylor, principal engineer at Concept Systems.
That sentiment is echoed by an Atlanta-based builder of specialized aircraft assembly and manufacturing systems for Lockheed Martin’s new jet fighter, the F/A-22 Raptor. “When we first thought about this application,” says Roger Richardson, president, Delta Sigma Corp. (DSC), “we assumed we would have to work from the CCD on back. But when we found we could buy, ready-to-go, a no-compromise vision system that fit our accuracy and package requirements for $5,000--instead of creating something that would likely take us $100,000 and three months to develop--there was no reason not to go with it.”
For many it’s a relief that COTS vision is a viable alternative because early systems were tough to build and program, says Roberto Griguoli, vision project manager at Simac Masic, Veldhoven, Netherlands, an engineering firm that specializes in design and development of machine vision, motion control and data acquisition solutions "In the early days, computer programmers were an essential part of machine vision projects for OEMs,” he says. “The only way to get the job done was by programming in C or C++,” explains Masic. “These computer programmers were forced to learn the details of imaging, lighting, optics and image processing.” You had to pay big bucks and follow a steep learning curve for those highly specialized individuals.”
George Blackwell, director of product marketing for Cognex, agrees that in-house development of vision systems went out with bellbottom pants. “Very few equipment builders design their own vision boards today,” he says. “Most buy off-the-shelf hardware--frame grabbers, cameras and lighting--then integrate these components into a system.”
Concept Systems eventually standardized on Cognex board-level vision products and cameras. “We use boards with a 1024x768 camera for normal projects, and a board with a 1280x1024 camera for projects that require a greater field of view as well as high resolution,” explains Taylor.
For its 96 servo axes, 16-camera VisionPin non-contact wing and fuselage alignment and mating system for the F/A-22, Delta Sigma specified DVT Corp.’s Series 600 high-speed smart cameras with 640x480 pixel resolution and separate, modular light sources. The cameras are fixed to critical mating lugs on tools that represent the wings while the main part of the system supports and manipulates the forward, mid, and aft fuselage sections. According to Brett Haisty, vice president of engineering at DSC, “position measurement accuracy is 0.0002 in. in-plane and the distance measurement is accurate to 0.0005 in. with this camera.”
The cameras provide a visual “pin” for the lugs to align to and deliver precise position feedback to control the X, Y, Z, roll, pitch, and yaw motion of the tools moving the fuselage subassemblies into position. The system ensures alignment accuracy of 0.004 in. across the aircraft’s 22-ft.-long wing joint.
Doug Wilson, president of PVI Systems, an engineering firm in East Lyme, Conn., also puts machine vision systems in the custom machines his company builds for customers. “We mostly use machine vision for parts inspection applications, but we also employ vision in a true control mode, where the vision system is used to collect feedback,” says Wilson.
Like Concept Systems, PVI has years of experience with vision applications and it, too, chose a COTS solution. “We use products from National Instruments,” says Wilson. “It lets us use the same LabView and IMAQ Vision software, with which we have more than eight years of experience.”
One of the best features of a COTS system is its reliance on standards, says Kyle Voosen, product marketing manager at National Instruments. “All of NI’s products leverage industry-standard PC technologies,” he says. “A perfect example is our CVS, a tiny, embedded machine vision system based on an Intel chipset, IEEE-1394 for camera and hard drive connectivity, and a reconfigurable Xilinx FPGA for custom digital control and I/O. This architecture allows machine builders to choose the best vision components for their application and even use their own custom vision algorithms.”