Encapsulating HTTP Messages in MODBUS for Network Interoperability

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Solution Overview

Problem

MODBUS protocol limitations, such as serial line frame length restrictions and limited node capacity, hinder efficient communication in factory automation networks, particularly when interfacing with modern protocols like HTTP across different network types.

Innovation Solution

The method involves encapsulating HTTP messages within MODBUS/TCP or serial MODBUS protocols to facilitate communication between automation devices and web browsers, enabling message tunneling and interoperability by using MODBUS/TCP or serial MODBUS protocols to bridge between different network types, including Ethernet-based networks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If MODBUS serial line protocol is used for communication, then compatibility with legacy automation devices is maintained, but message length is limited to 256 bytes and node capacity is restricted

Engineering Contradiction:

Improveprotocol compatibilityVSAvoidmessage length

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent encapsulates MODBUS messages within TCP/IP packets, creating a nested protocol structure where MODBUS operates as a layer above TCP/IP. This allows the message to be transported over Ethernet networks, effectively removing the 256-byte limitation while maintaining MODBUS compatibility at the application layer.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent introduces a gateway device that acts as an intermediary between MODBUS serial devices and Ethernet networks. The gateway translates and encapsulates MODBUS messages into TCP/IP format, enabling communication between legacy MODBUS devices and modern Ethernet-based systems without direct modification to the original devices.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If MODBUS serial line protocol is used for communication, then simplicity of implementation is maintained, but network speed and cabling flexibility are limited

Engineering Contradiction:

Improveprotocol implementationVSAvoidnetwork communication speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The patent makes the MODBUS protocol multi-functional by enabling it to operate over multiple transport mechanisms. The same MODBUS message format can be carried over serial lines, Ethernet, or other IP-based networks, allowing the protocol to adapt to different speed requirements while maintaining implementation simplicity at the application layer.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If message encapsulation and translation is implemented, then interoperability between different protocols is enhanced, but device complexity increases

Engineering Contradiction:

Improveprotocol interoperabilityVSAvoidmessage processing complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7574512B2MODBUS encapsulated transport interface

Publication Date: 2009.08.11 SCHNEIDER AUTOMATION SAS

AI summary

A method for encapsulating HTTP messages within a MODBUS message is described in the present invention. This MODBUS message can be encoded and sent using either MODBUS/TCP or serial MODBUS. Within MODBUS, the encapsulation is built using the MODBUS Encapsulation Interface (MEI). The HTTP message may contain HTML, XML, XHTML, or SGML.