Process Control Safety Signal Bypass for Response Time Reduction
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Solution Overview
Problem
Current process control systems face challenges in achieving safe and rapid response times due to increased response times and safety distances caused by signal processing and data transmission, particularly in applications with time-critical sensors like light grids, which require fast data transmission and result in high bus loads, limiting the number of participants in the network.
Innovation Solution
The solution involves logically linking non-safety-related process signals with safety signals in a local control unit, allowing a local safety signal to bypass the logical link for direct activation of the process device via a high-speed switching path, reducing response times by eliminating time-consuming signal propagation and processing delays, and incorporating a quick-switching function to confirm and reverse state changes based on joint evaluations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If process signals and safety signals are logically linked in a centralized safety controller, then safety control is achieved, but response time increases and safety distances must be increased
Solution Approach 1:
The patent divides the safety control function into two segments: a first control unit that processes safety signals and generates control signals, and a second control unit that executes the control signals. This segmentation allows the first control unit to respond quickly to safety signals without waiting for lengthy logical linking processes, thereby reducing response time while maintaining safety control reliability
Solution Approach 2:
The patent implements preliminary action by having the first control unit generate control signals in advance based on safety signals before the full logical linking with process signals is complete. This allows the system to prepare safety responses proactively, reducing the actual response time when safety events occur
2Loss of time
If data transmission rate is increased to reduce response time, then response time decreases, but bus load increases and limits the number of network participants
Solution Approach 1:
The patent segments the control architecture into distributed control units that process safety signals locally rather than transmitting all data through a centralized bus system. This reduces the overall bus load while maintaining fast response times through local processing
Solution Approach 2:
The patent implements local quality by enabling each control unit to independently process safety signals and generate control signals locally without requiring high-speed centralized data transmission. This local processing capability reduces bus load while achieving rapid safety responses
3Reliability
If safety signals are processed through logical linking with process signals, then comprehensive safety control is achieved, but response time increases due to processing delays
Solution Approach 1:
The first control unit performs preliminary processing of safety signals to generate control signals before the complete logical linking with process signals is finalized. This preliminary action allows the system to initiate safety responses faster while the comprehensive logical linking continues in the background
Solution Approach 2:
The patent introduces an intermediary mechanism where the first control unit generates intermediate control signals based on safety signals alone, which then serve as the basis for final control execution. This intermediary step bypasses the time-consuming logical linking process for the critical safety response path
Data Source
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AI summary
The method involves controlling of a process device (11) that is controlled by a process module (13) and a security module (15,15'), in which non-security relevant process signal (P) of the process module and the process stability related to the security signals (S,S',S'') of the security module that are combined with each other. A local security signal of a local safety sensor is directly supplied to the local control unit (17). The fast switching path (29), has a fast switching function, in which the result (35) of the logical combination and the local security signal are evaluated jointly. An independent claim is also included for a system for process control, in particular for the execution of a method, has a process device which is controlled by a process module and a safety module.