3D images give a clearer view
By Fabian Zimmer, Product Manager for 3D Compact Systems, SICK AG, Waldkirch
Monday, 12 February, 2018
Outdoor industrial environments are constantly changing and to ensure that changes are always detected, SICK has designed its Visionary-B sensors with two eyes, in the form of horizontally offset lenses. This allows objects and obstacles to be safely identified in three dimensions by the stereoscopic principle. The result is an adaptive driver assistance system that uses intelligent algorithms to transmit live images (shown on the monitor near the steering wheel) with a filtered view of what is important to the driver. SICK’s Visionary-T sensors also create three-dimensional images. These products have one eye and are designed for indoor use and, like the Visionary-B, are equipped with SICK’s 3D snapshot technology. The sensors can be used, for example, to provide object detection or collision warning functions in automated guided vehicles (AGVs) and human-robot collaborations.
Driver assistance systems are required when the driver needs to pay full attention to their vehicle while navigating through obstacles, particularly when they are managing bulky loads. Often the driver cannot see the vehicle’s entire route or identify potential risks and obstacles in the surrounding area in real time. Typical applications for these systems include transport logistics, agriculture, construction sites, mines and ports, where industrial trucks, loaders, tippers or container vehicles, many of which are very large, are operating. SICK’s innovative 3D snapshot technology gives a full view of the area, including any of the driver’s blind spots.
Complete images without delay
The Visionary-B and Visionary-T sensors capture complete scenes in three dimensions with extremely short exposure times. Conversely, the 3D laser scanners scan their field of view taking in one line at a time. Therefore, as a result, there is always a delay in producing a static image, resulting in uncertainty or danger while navigating. SICK’s 3D snapshot technology operates like a ‘normal’ digital camera wherein every single pixel is exposed at the same time. This process prevents sudden changes creeping into the image, as can be the case with the line-by-line scanning process.
Another advantage of the Visionary-B and Visionary-T is that the three-dimensional image is created either by the stereoscopic principle using two lenses or using time-of-flight measurements with one lens. Mechanically moving parts are not needed in either case. The Visionary-B sensors, from a functional perspective, work in the same way as the human eye and the evaluation unit functions like the brain and analyses the raw 3D data from the sensor head.
By contrast, 3D laser scanners use rotating mirrors or rely on the movement of the objects in front of the scanner. This makes them more sensitive to vibrations and sudden changes that frequently occur in tough industrial sites such as mines and stone quarries. Static scenes also restrict the possible uses of 3D laser scanners because of their operating principle. The lack of mechanically moving parts in SICK’s 3D snapshot sensors increases the fail safety and durability of the system.
In addition to the way in which the images are created, other advantages include the rugged construction of the cameras and the shock- and water-resistant housings, which are specifically designed for tough conditions. For example, the sensor head of the Visionary-B can be cleaned using a fire hose. Design details like these play a key role in ensuring that the sensors are ideal for an industrial environment.
Assessing the situation quickly
At an industrial site, it is conceivable that an employee could suddenly appear from around a bend while a truck is reversing. In situations like this, the sensors must be able to respond quickly and inform the driver immediately about the risk. For this purpose, the Visionary-B takes several images per second. This ensures that the stereo images have a high information content, which is subsequently merged and evaluated by a high-performance computer to create a three-dimensional picture.
Despite the fact that a huge volume of data is needed to detect risks or obstacles reliably, drivers must also not be distracted by the flood of information. This is why the intelligent algorithms in SICK software filter out the information that is irrelevant to the driver. This includes small irregularities on the road surface, stones, rain and fog. The system ensures that drivers are only warned about genuinely critical situations. If unimportant occurrences or very small obstacles on the route triggered an alarm, this would reduce drivers’ confidence and acceptance of driver assistance systems. And if these alarms became a regular occurrence, eventually the driver would switch it off or ignore it.
Scaled-down solution for indoor use
While the Visionary-B, with its rugged design and low lighting requirements, is intended primarily for outdoor use, SICK has developed the Visionary-T specifically for indoor driver assistance systems. These sensors also have cameras and intelligent analysis software. The difference is that information about the distance and size of objects is obtained not by measuring the disparities in the stereo image but by taking time-of-flight measurements. The Visionary-T has a single eye and uses infrared light sources to measure the time-of-flight between the surface of the object and the camera. This allows the sensor to provide in-depth information for every pixel in real time.
The process, which involves taking up to 50 three-dimensional images per second, functions because SICK’s system can measure the minuscule differences in the time taken by the light travelling from its source to the object and back again. These differences make it possible to calculate the distance to the reflective surface. The resulting data forms the basis for the creation of three-dimensional images, in which different colours indicate distance. The integrated active lighting system illuminates the surroundings enabling the camera to be used in complete darkness. Unfortunately, the use of 3D time-of-flight technology is restricted in applications with strong external light sources, such as direct sunlight in open production and logistics facilities. This is why in its outdoor solutions SICK has opted for classic stereo cameras, as the monitoring process cannot be put at risk either by reflections or direct sunlight.
In indoor applications, such as large logistics centres or extensive production areas, the Visionary-T and 3D snapshot technology are designed to provide reliable detection assistance. Further, the functions offered by these compact devices go far beyond simple collision warning. For example, the Visionary-T is ideal for use in collaborative production processes where people and robots are working side by side. These sensors are so flexible that they can be configured and deployed so that robots can identify what is moving towards them and modify their approach. For example, if it is an automated guided vehicle (AGV), the robot continues at full speed. However, if the object that has been detected does not have the same outline as an AGV, because it is, in fact, a person, it is possible to specify predefined scenarios for the robot that include restricted or slower movement, or come to a complete standstill.
Other applications for the Visionary-T are in the fields of logistics and material flow. The sensors can be used, for example, to obtain reliable information about the size of parcels or packaging units. As well as detecting objects, the sensors can also identify gestures, which is an important consideration in the context of human-machine collaborations.
Improving the material flow
Self-driving systems, reversing assistants and intelligent spatial analysis are all applications where working areas and transport routes can be effectively monitored using 3D sensors. In light of the growing number of human-machine collaborations, this technology is beginning to play an increasingly important role. SICK’s 3D snapshot technology can also be used to identify positions in high-bay warehouses when pallets are being stored or removed. 3D sensors can also detect empty areas during the palletising process making it easier to manage the material handling process and improve efficiency.
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