Junction Relay Control for Isolating Network Transmission Errors
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Solution Overview
Problem
In control systems where a safety controller and a standard controller are connected via a network, existing configurations often result in standard control and safety control being independently performed, but they can be disrupted by transmission errors, leading to unnecessary stops of functional units and potential safety risks.
Innovation Solution
A control system with a junction device that manages periodic communication frames, detects transmission errors, and selectively switches its state to either disable all signal outputs or continue updates based on the configuration of connected functional units, ensuring that only affected controls are stopped, thereby preventing unnecessary disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common junction device is used to connect both safety controller and standard controller to the network, then device complexity is reduced and space is saved, but transmission errors can disrupt both control functions causing unnecessary stops and safety risks
Solution Approach 1:
The junction device segments control functions by creating separate virtual channels: a first channel for standard control signals and a second channel for safety control signals. This segmentation allows transmission errors to be isolated to specific channels, preventing disruption to other control functions while maintaining the benefit of using a single physical junction device.
Solution Approach 2:
The junction device acts as an intermediary that introduces error detection and state switching mechanisms between the network and functional units. When transmission errors are detected in one channel, the junction device can switch states to protect affected functional units while allowing other channels to continue operating normally.
2Reliability
If transmission error detection is implemented in the junction device, then reliability of control functions is improved, but device complexity and processing requirements increase
Solution Approach 1:
The junction device implements self-service error detection by autonomously monitoring transmission signals and automatically switching states when errors are detected. This self-service capability improves reliability without requiring external intervention or complex external error handling systems.
Solution Approach 2:
The junction device uses feedback mechanisms where transmission errors are detected and fed back into the state switching logic. This feedback loop enables automatic adjustment of operational states based on transmission quality, improving reliability while keeping the processing complexity manageable through standardized feedback protocols.
3Reliability
If all signal outputs are disabled when transmission error is detected, then safety is ensured, but productivity is reduced due to unnecessary stops of healthy functional units
Solution Approach 1:
The junction device applies local quality by enabling selective state switching for different functional units based on their specific control channel status. When transmission errors are detected in one channel, only the affected functional units switch to a protected state, while other functional units operating on error-free channels continue normal operation, thus maintaining productivity without compromising safety.
Solution Approach 2:
Instead of applying full shutdown action to all functional units when any transmission error occurs, the system applies partial action by selectively disabling only the minimum necessary functional units affected by the error. This partial action approach maintains safety for critical functions while preserving productivity through continued operation of unaffected functions.
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3(A)~3(B)
AI summary
The junction device includes a first error detection means that detects a transmission error by monitoring the periodic reception of a first communication frame, and a state switching means that switches, when a transmission error is detected by the first error detection means, a state of the junction device to either a first state in which the signal output from all of the functional units connected to the junction device is disabled or a second state in which the signal output from some of the functional units connected to the junction device is continuously updated based on the configuration of each functional unit connected to the junction device.