Virtual Placeholder Objects for Distributed I/O Module Removal
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Solution Overview
Problem
Existing distributed I/O systems require reconfiguration and reprogramming when I/O modules are removed or added, leading to burdensome maintenance of multiple island configuration files for machines with different options.
Innovation Solution
The implementation of Virtual Placeholder objects in the network interface module allows for a consistent process image across various I/O configurations, enabling the removal of I/O modules without reconfiguration by using a translation table to map physical to logical module addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If I/O modules are removed or added from the distributed I/O system, then the system configuration changes to meet different machine options, but reconfiguration and reprogramming are required which increases maintenance burden and time
Solution Approach 1:
The patent creates a virtual copy (placeholder object) of the I/O module that remains in the process image even when the physical module is removed. This virtual copy maintains the same address and data structure as the original module, allowing the PLC program to continue accessing I/O points without modification. The placeholder object is a software representation that replicates the physical module's interface characteristics.
Solution Approach 2:
The placeholder object acts as an intermediary between the PLC program and the physical I/O module. When the physical module is removed, the placeholder object mediates by providing a dummy data structure that the PLC can access through the same address, preventing direct access errors while isolating the program from the physical hardware change.
2Adaptability or versatility
If multiple island configuration files are maintained for different machine options, then each configuration can be optimized for specific hardware setups, but the complexity of configuration management increases
Solution Approach 1:
The placeholder object provides a universal solution that works across all machine configurations. Instead of creating separate configuration files for different hardware setups, the same base configuration file can be used with placeholder objects automatically generated for removed modules. This single configuration approach serves multiple hardware variations.
Solution Approach 2:
The system dynamically changes the presence parameter of I/O modules in the configuration. When a module is removed, its presence parameter is set to false, and a placeholder object is created instead. This parameter change allows the same configuration file to adapt to different hardware setups without structural modifications.
3Ease of manufacture
If I/O modules are physically removed to reduce costs or simplify machines, then hardware requirements are reduced, but the PLC program must be modified to add/delete options
Solution Approach 1:
A virtual copy (placeholder object) of the removed I/O module is created in the process image. This placeholder maintains the same address, data type, and access characteristics as the original module, allowing the PLC program to continue operating without modification. The virtual copy is indistinguishable from the real module from the program's perspective.
Solution Approach 2:
The placeholder object is pre-configured with the same parameters and address as the original I/O module before the physical module is removed. This preliminary setup ensures that when the physical module is taken out, the PLC program immediately finds the expected interface without requiring any changes or reconfiguration.
Data Source
AI summary
A modular distributed I/O system for an industrial automation network that allows one or more modules of an island to be omitted without requiring reconfiguration of the system by maintaining a consistent I/O image representation of the distributed I/O network for various physical distributed I/O configurations, and managing reconfiguration changes using Virtual Placeholder objects.