Safety warning – loss of control/view
The designer of any control scheme must consider the potential failure modes of control paths and, for certain critical control functions, provide a means to achieve a safe state during and after a path failure. The examples of critical control functions are emergency and over-travel stop that may include the following capabilities:
- Separate or redundant control paths must be provided for critical control functions.
- System control paths may include communication links. Consideration must be given to the implications of unanticipated transmission delays or failures of the link.
- Each implementation of a control system must be individually and thoroughly tested for proper operation before being placed into service. ...
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