Safety On Board
Need for integrated safety on board controllers
Today, production managers require more productivity through machines. Manufacturing industry suffers from stopping production line to perform day-to-day maintenance activities. Once multi axis motion controller based manufacturing line running hundred’s of delta robots is stopped, engineers are required to re-synchronize axis if integrated safety is not implemented in the production line design. It is because integrated safety on board technology allows plant engineers to safely stop machine without disconnecting power to the production line. In addition to enhanced productivity, integrated on board safety technology monitors movements where generated and respond very fast compared with traditional motion controllers where external controller stops power or reduce speed of motion controller in event safety circuit is not healthy.
Qualifying for certified safety on board solutions
Today, machine directives and relevant standards dictate requirements for a solution to pass qualifications related to Safety On Board Technology. There are various safety functions classifications available in the relevant directives. For instance,
- For Motion – SOS (Safe Operating Stop), SLS (Safety Limited Speed) are amongst few.
- For Position – SMP ( Safety Monitored Position), SLP ( Safety Limited Position).
- For Power disconnection – STO (safe torque off), SS1 ( safe stop 1).
Dual Channel Safety Inputs Monitoring
A very popular safety on board architecture involves feeding two set of inputs to the motion controller with safety on board technology of ‘Safety Inputs/Outputs SIO’ which have built in technology for dual channel monitoring. If a deviation of the monitored inputs/parameters is detected in one of the two channels, this causes the error reaction and the drive system goes to the safe status.
Dynamization pulse between motion controller and safety PLC PILZ or another controller is very common as well in manufacturing industry. Dynamization pulse ensures that external PILZ PLC knows motion controller is working. You might even want to feed back PILZ inputs as watch dog into motion controller. Dynamization pulse could be anything like a 1HZ discrete on/off signal between controllers. If one of the controller fails to detect a pulse within one second, it goes into error state.
Safety On Board technology in motion controller is becoming important now to achieve safe working environment for man and machine. By integrating advanced safety on board technology, machine builds could enhance safety integrity level SIL for the machine. I have come to know one manufacturer Bosch Rexroth who manufacturers servo motor and drive solutions with diverse options for many advanced, certified and reliable integrated safety on board technologies. It might be worth looking them up on google for your next motion control application.
If you need assistance with designing a safety-critical motion application, then please feel free to contact using the details on this website.