Safety is built into the system at all levels. All drives are monitored by a separate process. Absolute encoders on the output shaft are used together with motor encoders to control each machine’s integrity, as well as to monitor synchronous motion. Important functions are not simply doubled, but are handled by two different methods so that design and system errors will not compromise safety.
In designing the safety systems, the goal is to obtain the highest levels of safety without compromising reliability. All safety functions that can stop or prevent movement are easily traceable and continuously supervised by the main control system.
The following points are central to the Visual act safety philosophy:
- CONTINUOUS CONTROL OF SYSTEM INTEGRITY All important parts of the system are continuously monitored, also when drives are not in use.
- DOUBLING OF FUNCTION BY SEPERATE ALGORITHMS (DIVERSITY) We do not simply mirror or double components in order to achieve the required safety levels. This avoids system failure due to systematic design or production faults. Each drive is monitored by a control routine on a separate and different computer using an independent network and an independent encoder. Software modules are monitored by both parent and child processes.
- USABILITY AND OPERATOR TRAINING
No amount of safety features can stop an operator from making dangerous movements. Even if it was possible, doing so would seriously cripple the system, destroying both its dependability and availability. The operator desk must be usable in the sense of providing the operator with the information necessary to evaluate the safety of his actions. The owner must insure that operators are suitable qualified.
In designing, producing and testing hardware and software Visual act actively follows the safety standard EN 61508 for all stages of the product lifecycle. Based on the risk assessment safety functions are identified, described and allocated. The hardware and software is then designed to provide the required safety integrity level (SIL) for each function. High standards of quality control during production and intensive testing confirm that the safety level is attained.