PLC Managed Modbus Master Redundancy for Traffic Reduction

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Solution Overview

Problem

Existing automation control systems using Modbus communication protocol face challenges in reducing redundant traffic and improving data acquisition speed without compromising reliability and availability.

Innovation Solution

A system comprising a programmable logic controller (PLC), a primary master device, a standby master device, and multiple slave devices, where the PLC monitors the health and communication status of the primary master device and switches to the standby master device in case of failure, ensuring seamless communication with the slave devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a traditional Modbus master-slave configuration is used, then communication reliability is maintained, but redundant traffic increases and data acquisition speed decreases

Engineering Contradiction:

Improvedata acquisition speedVSAvoidredundant traffic

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The system segments the master device functionality into a primary master device and a standby master device. The primary master handles normal communication operations while the standby remains on standby, dividing the communication load and eliminating redundant traffic from multiple active masters, thus improving data acquisition speed without sacrificing reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The standby master device is pre-configured and ready to take over immediately upon detecting primary master failure. This preliminary preparation ensures seamless failover without interrupting communication, maintaining reliability while the primary master efficiently handles normal operations without redundant traffic

Inventive Principle:

Principle #10Preliminary action

2Reliability

If a standby master device is added to improve reliability, then availability increases, but device complexity increases

Engineering Contradiction:

ImproveavailabilityVSAvoidsystem configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system implements self-service through automatic failover detection and switching. The PLC automatically detects primary master failure and switches to the standby master without manual intervention, reducing operational complexity while maintaining high availability through the redundant standby configuration

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The PLC acts as an intermediary that manages the failover process between primary and standby master devices. It monitors system status, detects failures, and coordinates the switching process, simplifying the overall system architecture while ensuring reliable backup operation

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250158876A1Systems and methods to control modbus redundancy

Publication Date: 2025.05.15 SCHLUMBERGER TECH CORP

AI summary

A system includes a programmable logic controller (PLC); a primary master device; a standby master device; and a plurality of slave devices, wherein the primary master device is configured to communicate with each of the plurality of slave devices, and wherein the PLC is configured to determine that the primary master device is in a failure state, and in response, the PLC is configured to switch from the primary master device to the standby master device such that the standby master device is configured to communicate with each of the plurality of slave devices.