proportion of the waves . As the quantity of radar waves reflected by a person is significantly different to that reflected by wood chips or moisture , the LBK can detect whether the reflection comes from a person or from non metallic particles . In other words , particles in the air are not detected whereas a person is . The LBK therefore switches off reliably when a person is located in the danger zone . The LBK sensor emits its radar waves in three dimensional space so that not only the surface area but also the volume of this space is monitored . This allows the LBK to detect persons who enter a hazardous area or who are located in this area , regardless of whether they are standing , kneeling or lying .
Utilizing the properties of the radar frequency electromagnetic waves in sensors provides a solution for applications where optical sensors have so far proven unreliable .
Detecting human movements
The LBK 3D radar system not only operates in a wavelength range new to safety technology . It also uses FMCW , an operating principle which is also new to safety technology . FMCW stands for Frequency Modulated Continuous
Wave . Here , the transmission frequency changes within a defined bandwidth . Starting at a fundamental frequency , it increases continuously up to a maximum frequency and then returns to the fundamental frequency again . If a person reflects this signal , it reaches the receiver with a time delay . Subtraction of the reception signal from the transmission signal produces a difference frequency . If the distance between the LBK sensor and the person remains constant , the difference frequency also retains its value . However , if the person moves , the time delay between the transmitted and received signal changes , and therefore also the difference frequency . The faster the person moves , the greater the change in difference frequency will be . In this way , the LBK sensor is able to determine the speed at which the person is moving .
Precise determination of movements
This method is also referred to as radar Doppler . It allows movements to be determined with a very high degree of accuracy . The LBK sensor therefore detects not only a moving person , but also a person who is currently standing still , even if the movement is extremely slight . Even if a person is standing still , they are never absolutely motionless – there is always some movement , e . g . from their pulse or heartbeat , etc . The LBK sensor utilizes this to reliably distinguish a person in a danger zone from a static object , e . g . a pallet or material container . The slight movements of a person are sufficient to generate a reliable switch off signal for the machine . As a result , the LBK system interrupts the operating process only if somebody is actually located inside the danger zone . For example , completely static , motionless material containers can be left inside the protected area without them leading to interruption of the operating process . In this way , the LBK system prevents unnecessary downtimes and thereby increases the availability and cost effectiveness of the system . On the other hand , it ensures that the machine only starts to run again when all persons have left the danger zone , and therefore contributes to reliable personnel protection .
Flexible in use , easy to install
In addition to use in harsh environments , the LBK safety radar system is used primarily for preventing unwanted restarts and for monitoring hidden areas . Users can adapt it to their individual requirements . The system consists of a controller to which up to 6 radar sensors can be connected . The positioning of the sensors , the adjustable operating range and the selectable opening angle allow flexible adaptation of the monitored area to the danger zone . This also allows areas on steps or pedestals to be monitored reliably . The user can define the system parameters using the easy to operate configuration software . Certified safety experts from Leuze are available to assist with configuration and commissioning if required .
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