What is the function of a safety-rated programmable logic controller (PLC) in a robotic system?

The function of a safety-rated programmable logic controller (PLC) in a robotic system is to reliably monitor the safety devices, implement the safety logic, and initiate safe responses when a hazardous condition is detected. A safety-rated PLC is specifically designed and certified to meet stringent safety standards, such as IEC 61508 and EN ISO 13849, making it suitable for use in safety-critical applications. In a robotic system, the safety PLC receives signals from various safety devices, such as light curtains, emergency stop buttons, safety scanners, and door interlocks. It processes these signals according to a pre-programmed safety logic, which defines the actions to be taken in response to different safety events. If a hazardous condition is detected, such as a person entering the robot's work envelope, the safety PLC will initiate a safe response, such as stopping the robot's motion, disabling its power, or activating an alarm. For example, if a light curtain is breached, the safety PLC will immediately send a signal to the robot controller to stop the robot, preventing a potential collision. The safety PLC provides a centralized and reliable means of managing the safety functions of the robotic system, ensuring that safety is maintained even in the event of component failures or software errors. A key aspect of the safety PLC is its ability to detect faults within its own system and initiate a safe state.