Next generation: Robots that see

Visual servo control: Vision used for robotic or machine guidance also can be used for in-line part inspection to enhance product quality with traditional feedback systems. See photos, video.

04/21/2013

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Figure 2: Video shows Denso robots picking syringes using NI machine vision and NI LabVIEW. Courtesy: National Instruments



Robotics and automated machines can use visual servo control for robotic guidance, enhancing motion control and improving product quality, while replacing traditional feedback systems.

Every year robots become more integrated into our everyday lives and less like characters familiar only in science fiction movies. The field of robotics is advancing in the manufacturing and consumer industries, but one of the main obstacles stalling significant growth in this space is that most robots are “blind” or unable to perceive the world around them. With little to no perception about their environment, they are unable to react to changing surroundings. Our eyes and brain act as built-in hardware and software that helps us perceive the world around us including the various depths, textures, and colors encountered during the day. Just as our eyes receive signals from our brain to continuously focus and adjust to light as we move around, the integration of vision technology with today’s software tools makes it possible for robots to see and react to their changing environment. It presents an opportunity to enter a wide range of new vision and robotics applications.

Vision-guided robotics

One of the most common uses for vision technology in robotics is demonstrated in vision-guided robotics. This has historically been applied on the factory production floor in areas such as assembly and materials handling, where a camera is used to acquire an image and locate a part or destination before sending coordinates to the robot to perform a specific function like picking up a part, as shown in the photos and short video clip.

Figure 1: Multiple Denso robots pick syringes from a conveyer belt and place them into individual packages. Vision technology enables enough flexibility in the robotics to pick up syringes regardless of orientation on the belt or if the manufacturer uses

Integrating vision technology in applications such as these makes it possible for machines to become increasingly intelligent and therefore more flexible. The same machine can perform a variety of tasks because it can recognize which part it is working on and adapt appropriately based on different situations. The additional benefit of using vision for machine guidance is that the same images can be used for in-line inspection of the parts that are being handled, so not only are robots made more flexible but they also can produce results of higher quality.

It can be expensive when a high degree of accuracy is essential for the motion components, such as the camera or motion system. Some vision-guided robotics systems use one image at the beginning of the task without feedback to account for small errors later.

Continuous feedback

Using a technique known as visual servo control solves this challenge as a camera is either fixed to or near the robot, and it provides continuous visual feedback to correct for small errors in the movements. As a result, image processing is used within the control loop, and in some cases the image information can completely replace traditional feedback mechanisms like encoders by performing direct servo control tasks.

Direct servo control accelerates the high-speed performance of applications such as laser alignment and semiconductor manufacturing among other processes that involve high-speed control. While the use of vision in robotics is common with industrial applications, it is becoming increasingly more prevalent in the embedded industry. An example of this advancement is found in the field of mobile robotics. Robots are migrating from the factory floor and taking on a more prominent role in our daily lives. Functions range from service robots wandering the halls of local hospitals to accommodate for healthcare system cost pressures and a shortage of doctors and nurses to autonomous tractors plowing fields to advance planting and harvesting efficiency.

See another photo and more application details on next page.


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