PLC Input Module With Three-State Interface Fault Detection
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Solution Overview
Problem
Existing input modules for industrial programmable logic controllers (PLCs) are bulky and lack a compact design while ensuring safety and proper operation, which is a challenge in modular architectures where space efficiency is crucial.
Innovation Solution
A compact input module with three-state interfaces (forcing, low, and read states) and a processing submodule for anomaly detection, utilizing components like transistors, diodes, and isolation parts to ensure secure interfacing and fault detection, reducing the need for multiple interfaces and enhancing space efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple identical interfaces per input are used to detect malfunctions, then safety and reliability are improved, but the module becomes bulky and space-consuming
Solution Approach 1:
The patent merges multiple interface functions into a single interface by implementing three distinct operational states (forcing state, low state, and read state) within one interface circuit. This eliminates the need for multiple parallel interfaces while maintaining the ability to perform both normal signal reading and self-test operations, thereby reducing module footprint while preserving safety functionality.
Solution Approach 2:
The interface is designed to be dynamic by allowing a single interface to switch between three different operational states (forcing, low, and read states) based on test commands. This dynamic capability enables the interface to perform multiple functions that would traditionally require separate static interfaces, thus reducing the overall module area while maintaining reliability.
2Reliability
If three identical interfaces per input are used to perform test sequences, then fault detection capability is improved, but the device complexity increases
Solution Approach 1:
The single interface is designed with universal functionality to perform both normal input signal reading and self-test operations by switching between three states. The forcing state forces the interface output to a known state for testing, the low state forces it to another known state, and the read state performs normal signal acquisition. This multi-functionality eliminates the need for separate test interfaces while maintaining comprehensive fault detection capability.
Solution Approach 2:
The interface incorporates feedback mechanisms where the output state is monitored and compared against expected states during self-test operations. The processing submodule receives feedback from the interface output and compares it with the state that should have been produced, enabling fault detection without requiring additional interface circuits.
3Reliability
If periodic test sequences are performed on interfaces, then operational safety is ensured, but the loss of time for signal processing increases
Solution Approach 1:
The patent implements periodic self-test sequences that are integrated into the normal operation cycle. The interface periodically switches between forcing state, low state, and read state to perform self-diagnosis. This periodic action ensures operational safety by regularly detecting faults while minimizing disruption to normal signal processing through efficient state transitions and integrated testing.
Solution Approach 2:
The interface performs preliminary self-testing by forcing known states (forcing state and low state) before normal read operations. This preliminary action allows the system to detect potential faults before they affect normal operation, ensuring safety while minimizing time loss through proactive rather than reactive testing.
Data Source
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AI summary
The invention relates to an input module (32) for an industrial programmable logic controller suitable for being connected to a plurality of elements of an automated chain, the module (32) comprising: - inputs (32A, 32B), each input (32A, 32B) being suitable for receiving a signal from at least one element of the plurality of elements, - interfaces (40A, 40B), each interface (40A, 40B) being associated with a single input and comprising at least one output (40A6, 40B6) suitable for operating in three distinct states, - a test block (42), and - a processing sub-module (24) suitable for comparing the state of the output (40A6, 40B6) of each interface (40A, 40B) with the state imposed by the test block (42) and for deducing an anomaly in the operation of the module (32, 34).