Module Communication Control Unit for PLC Hot Swap Sequencing
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Solution Overview
Problem
Existing solutions for hot swapping modules in programmable logic controllers face mechanical wear and cost issues due to non-standard connectors and dimensional compatibility problems, and they may cause intermittent communication when modules are incorrectly inserted.
Innovation Solution
A communication control unit is introduced between the module and the transmission bus, which requires a validation signal to establish communication, ensuring deterministic start-up and using standard connectors, while a passivation signal prevents communication during module extraction, avoiding mechanical constraints and parasitic signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different lengths are used for connector pins to achieve time sequencing during hot swap, then connection sequencing is ensured, but mechanical wear increases and cost increases due to non-standard connectors
Solution Approach 1:
The patent replaces the mechanical sequencing approach (different pin lengths) with an electronic control system. A controller with validation signal generation replaces the mechanical sequencing mechanism, allowing standard connectors to be used while ensuring proper connection timing through electronic control rather than physical dimension differences.
Solution Approach 2:
The patent changes the sequencing mechanism from physical parameter (pin length) to electronic parameter (validation signal timing). By controlling when the validation signal is generated based on module insertion detection, the system achieves reliable sequencing without mechanical modifications to connectors.
2Reliability
If long pin lengths are used to create sufficient time intervals for insertion/extraction sequences, then connection sequencing is ensured, but the total size of the PLC becomes larger
Solution Approach 1:
The patent eliminates the need for long pin lengths by replacing mechanical sequencing with electronic control. The validation signal timing is controlled by the controller's detection of module insertion, allowing standard pin lengths to be used while maintaining reliable connection sequencing without increasing PLC size.
3Reliability
If rotational insertion is used to sequence pin connections, then connection order is controlled, but tolerancing becomes difficult to achieve for small dimensions
Solution Approach 1:
The patent replaces rotational mechanical insertion with electronic control of communication activation. The controller detects module insertion and generates validation signals at appropriate times, eliminating the need for precise mechanical tolerancing in connector positioning while ensuring reliable connection sequencing.
4Ease of operation
If hot swap function is implemented without communication control, then module replacement is possible, but intermittent communication occurs when modules are incorrectly inserted
Solution Approach 1:
The patent implements feedback control through the validation signal mechanism. The controller monitors module insertion and only activates communication when proper insertion is detected, providing feedback control that prevents intermittent communication caused by incorrect module placement while maintaining hot swap capability.
Solution Approach 2:
The patent performs preliminary validation of module insertion before enabling communication. The controller detects whether the module is correctly inserted and generates validation signals only when insertion is proper, preventing communication issues before they occur rather than reacting to them after they start.
Data Source
Figure 1
AI summary
The device has a communication control unit (23) controlling communication between a connecting element (21) and a transmission bus (22) by applying a validation signal to a control input (25). A logical electronic unit (12) in a module (10) generates a validation signal, receives an input signal (S1) characterizing a state of the module at an input and delivers the signal at an output (S). The output generates the validation signal when the input signal represents an operation state of the module compatible with the communication of the module (10) with the bus.