Soft-PLC Safety Time Query Path Checking for Fail-Safe Control
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Solution Overview
Problem
Existing hardware-independent programmable logic controllers (PLCs) lack reliable timekeeping mechanisms for fail-safe control in edge environments, as they rely on unknown computing systems without separate, independent timers, posing risks in safety-critical applications.
Innovation Solution
A method and computing unit that utilize an external network card with an independent crystal oscillator for timekeeping, ensuring secure communication paths and detecting software errors to maintain a safe state by configuring the PLC's physical interface to always access this external card, thereby avoiding reliance on potentially internal, non-independent timers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hardware-independent control software is used to run on unknown computing systems, then adaptability and flexibility are improved, but reliability of timekeeping for fail-safe control deteriorates
Solution Approach 1:
The patent introduces a configuration file as an intermediary that bridges the hardware-independent control software and the specific hardware interface card. This configuration file explicitly defines which interface card should be used for safety-related timekeeping, allowing the software to adapt to different hardware environments while maintaining reliable timekeeping through precise hardware identification and selection.
2Reliability
If separate independent timers are used to ensure fail-safe timekeeping, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent makes the interface card universal by enabling it to serve both standard control functions and safety-related timekeeping functions. The interface card contains multiple timers that can be configured for different purposes, and the control software can selectively use these timers for safety functions when needed, eliminating the need for separate dedicated safety hardware.
Solution Approach 2:
The patent merges the safety-related timekeeping function with the standard control interface card. Instead of requiring separate independent timer hardware, the interface card's timers are configured and used for both standard control and safety functions, combining multiple functions into a single hardware component to reduce overall system complexity.
3Reliability
If configuration files are used to specify secure communication paths, then reliability is improved, but ease of operation deteriorates
Solution Approach 1:
The patent performs preliminary configuration of secure communication paths and timer selections in the configuration file before the control software runs. This pre-configuration ensures that the correct hardware interfaces and timers are identified and selected before safety-critical operations begin, improving reliability while requiring minimal intervention during actual operation.
Data Source
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AI summary
In order to detect a possible software/hardware error in the computer system (1) in a method for operating cycle-oriented control software (Soft-PLC) for the fail-safe control of automation processes of a process, wherein the control software (Soft-PLC) is executed within a computer system (1), which causes an erroneous query of the safety time (FT) from an internal interface card (iNIC), it is cyclically checked whether a query path for the independent safety time (FT) corresponds to safe connection paths (S7V), if this is not the case, a safe state is assumed by means of the control software (Soft-PLC).