Cameras give industrial vision-guided robots human-like functions

Using cameras can help give vision-guided robots (VGRs) the tools needed to be real assets on the plant floor.

By Henry Martel January 16, 2023
Courtesy: Chris Vavra, CFE Media and Technology

Vision-guided robot (VGR) insights

  • Vision-guided robot (VGR) technology has grown thanks to advanced in RGBD cameras, which allow the robot to accurately acquire 3D models.
  • VGRs also are more flexible than traditional robots and the vision systems can make them safer, as well.

It was only ever a matter of time before robotics and vision technologies merged. The first vision-guided robot (VGR) was a pick-and-place machine known as the programmable transfer machine. Essentially, the machine had a monochrome camera that was programmed with an algorithm that took pictures of each workpiece that it interacted with. If the piece did not match the algorithm, the piece was rejected – the programmable transfer machine would not interact with it.

Today, VGR technology has grown beyond the programmable transfer machine due to advances in 2D and 3D cameras, visual servo control, embedded Ethernet networks and more sophisticated software including artificial intelligence (AI). Advances in RGBD cameras – composed of a standard RGB camera and a depth sensor – have received attention because of their ability to quickly acquire 3D models of the environment and to estimate the camera pose in a low-cost way. Prior to RGBD cameras, other approaches to simultaneous localization and mapping (SLAM) robotics relied upon laser sensors that are far more expensive.

The benefits of incorporating a vision system into an industrial robot are numerous. Empowering a robot to ‘see’ allows it to precisely and consistently differentiate, pick, sort, move, weld or assemble various parts no matter their complexity. For instance, a multiple-step manual welding task on an automobile assembly line might take ten ‘blind’ robots to perform since each part must be mounted in place before every weld. However, this same multi-step welding process can be done with a single VGR, since its camera can precisely align the different parts in place without human assistance.

Flexibility is another benefit of VGRs. As with a machine vision system on an assembly line, a VGR uses intelligent processing to give it instructions. A slight alteration to the code allows the same robot to perform entirely different tasks, switching between products and batch runs without the need for any mechanical adjustments.

Safety is another consideration. With VGRs, factories can significantly reduce the risk of on-site accidents. To give you an idea of how that might work, consider a vision-guided forklift inside a warehouse. The automated forklift will sense obstructions along its pre-programmed paths and its movements to avoid contact with people or objects while precisely selecting items off pallets to meet customer orders. At Amazon, for instance, robotic material handling collaborative robots (cobots) safely work directly alongside humans.

The need for Ethernet switches for VGRs

To add vision to a robot, one or more cameras are needed. One is mounted on the robotic arm, serving as the machine’s eye Other cameras are installed in strategic locations in the working cell to capture more visual data. Adding these static cameras will compensate for the limitations of the arm-mounted camera. Careful attention must be given to ensure the camera and lens has the proper resolution, frame rate, and depth-of-field required for the application at an acceptable cost. Low-cost GigE Vision cameras are preferred since they use standardised, off-the-shelf Ethernet cables and components, while eliminating the need for frame grabbers.

All this engineering takes a collaborative effort on the part of vision systems providers, robotic arm manufacturers, and robotic systems integrators. It isn’t a surprise that a major trend today is to purchase VGRs already equipped with a vision system supplied by the robot manufacturer. This translates into faster adaptation into a production line, lower costs, and more responsive technical support from a single manufacturer.

Whether the vision system is installed by the end-user or the OEM, it will require an industrial Ethernet switch to create an embedded Ethernet network within the robot. Ethernet allows the individual robot parts to communicate with each other and is suitable for VGRs because Ethernet can handle image data.

Space inside a robot is always a limiting factor. The compact DIN-rail design of Ethernet switches allows them to fit easily next to a power supply, contactor, or relay. Power over Ethernet (PoE, PoE+, PoE++) is available on most of industrial switches to uncomplicate the connection of cameras and other components. In addition to multiple Gigabit Ethernet ports, industrial switches offer SFP slots for fibre optic connections. Fibre is impervious to electronic noise, so the SFP slots may be useful in running long-distance communications between the robot and a remote higher-level controller. While the industrial switch’s remaining Ethernet ports are able to collect data from various components in the robotic cell.

– This originally appeared on Control Engineering Europe’s website. Edited by Chris Vavra, web content manager, Control Engineering, CFE Media and Technology,