Wednesday, February 22, 2012

Safe limit value specification

Safe motion monitoring requires not just safe motion detection but also the opportunity to specify limit values safely. The way in which this is achieved depends on the level of dynamics and the flexibility within the machine.

Relay-like systems often use constant limit values. For example, a fixed limit value can be defined by setting jumpers or via other setting options on the device. On safe control systems, multiple limit values can be defined via configuration or programming user interfaces. Selection can be made during operation via a safe I/O interconnection, through evaluation of sensor signals or through specification via a safe fieldbus, for example. Dynamic limit values can only be used in conjunction with a powerful, safe control system or a safe bus system with real-time capabilities. When combined with optical monitoring of the protected field in robot
applications, for example, safe speed can be reduced based on the distance of the operator from the danger zone: the closer the operator comes to the danger zone, the slower the motors move.

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