Researchers at the Fraunhofer Institute for Applied Solid State Physics IAF have developed a compact modular 360-degree radar scanner that is superior to optical sensors and makes it a perfect choice for safety applications for human-machine collaboration. The radar works with millimeter waves that are reflected by the objects to be observed, such as people. Transmitted and received signals are processed and evaluated using numerical algorithms. Based on the calculations, it determines the distance, position and speed of the objects. If several radar units are used, an object’s location in the room as well as the direction of movement can be determined.
Increasing connectivity of production systems in “smart” industry 4.0 operations is driving the interaction between people and machines. The trend is moving towards industrial robots that operate without protective barriers. A mandatory thing for this level of co-working is that people must not be endangered at any time – but that is precisely the Achilles’ heel of collaboration between people and robots. Currently, laser scanners are used to monitor the danger zone around machinery, and to stop the machine as soon as a person enters the zone. However, optical sensors do not always achieve reliable results under changing light conditions. They also do not work if smoke, dust or fog limits visibility.
Unlike a laser scanner, this radar is not focused on one point, it sends out millimeter waves in a club shape which ensure the signals are reflected even when visibility is obstructed by an object. A laser scanner can reliably measure the distance and the position of a target – a person, for instance – only if the target is working in an unobstructed line of sight. However, IAF’s 360-degree radar can penetrate optically opaque material, which means it can identify the employee even if there are boxes, cardboard walls or other obstacles in the way.
Previous millimeter wave radar systems were based on waveguides which are bulky and expensive. IAF’s scanner has a diameter of only 20 centimeters and is 70 centimeters high. The high-frequency module featuring indium gallium arsenide semiconductor technology is no larger than a pack of cigarettes and is located in the base of the scanner. Nowadays millimeter wave applications are extremely expensive to produce due to waveguides dominance but IAF’s specially developed circuit boards, interconnection technology and cost effective mounting, helped them to replace the wave guides with their high-frequency module that has been integrated onto a board measuring just 78 x 42 x 28 millimeters. The high-frequency module, which is the key component of the radar scanner, was developed by IAF researchers in close collaboration with the Fraunhofer Institutes for Reliability and Microintegration IZM and for Manufacturing Engineering and Automation IPA.
In addition to the signal processor, the complete system comprises a transmitting and receiving antenna with a dielectric – that is, electric non-conducting – lens. A self-turning mirror affixed at a 45 degree angle deflects the millimeter waves, guides them, and evaluates the entire room. The use of a dielectric antenna, gives the liberty for free selection of the angle of aperture. That means nearby objects as small as a centimeter in size can be detected as easily as large objects that are far away. The system‘s range of operation is dependent on the application and can be up to several hundred meters. The scanner includes an Ethernet interface and is therefore suitable for industry 4.0 applications.
Hundreds of measurements were carried out In order to evaluate the measurement accuracy and reliability of the 360-degree radar. Maximum deviation from the mean was less than a micrometer; standard deviation was 0.3 micrometers.
The researchers will present a system demonstrator at the SENSOR+TEST in Nuremberg from April 25-29, 2016.
