Modbus Master Detection for Automatic Output Fallback
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Solution Overview
Problem
Existing Modbus protocols lack efficient monitoring mechanisms for Modbus clients acting as masters, leading to challenges in implementing output fallbacks when communication stops, requiring manual reconfiguration upon address changes and impacting system reliability.
Innovation Solution
A control device that automatically detects Modbus masters by analyzing request frequencies and IP addresses, enabling automatic fallback management of outputs without manual reconfiguration, even in multi-master scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If manual configuration of master addresses is used, then configuration flexibility is achieved, but configuration complexity and time consumption increase
Solution Approach 1:
The control device automatically detects Modbus master addresses by monitoring communication requests and counting request frequencies from different IP addresses. The system self-configures by storing IP addresses and request counts in a table, eliminating the need for manual configuration while maintaining adaptability to address changes.
Solution Approach 2:
The system continuously monitors communication requests from Modbus clients, counts the frequency of requests from each IP address, and uses this feedback to automatically identify the current master. This closed-loop monitoring enables automatic adaptation to address changes without manual intervention.
2Stability of the object's composition
If centralized configuration is used, then configuration consistency is improved, but system complexity and retrieval overhead increase
Solution Approach 1:
Each control device independently performs automatic master detection using local monitoring of request frequencies. This distributed self-service approach eliminates the need for centralized configuration management, reducing system complexity while maintaining consistency through local automatic detection.
3Reliability
If monitoring of master disappearance is implemented, then output fallback reliability is improved, but detection accuracy requirements increase
Solution Approach 1:
The system monitors communication requests over time and uses request frequency as feedback to detect master disappearance. By counting requests from each IP address and comparing frequencies, the system reliably detects when the expected master is no longer communicating, achieving both reliability and sufficient accuracy without overly complex detection mechanisms.
Data Source
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AI summary
A control device (CD) managing outputs of a set of Input/Output modules and implementing a Modbus server communicating according to a Modbus TCP/IP communication protocol with Modbus clients, comprises: a network interface (NI) configured to receive requests for commanding one or more outputs from the Modbus clients, a storage unit (SU) configured to store, for each request received from a Modbus client, an IP address of the Modbus client and the number of requests received from said Modbus client, a processing unit (PU) configured to determine a Modbus client as Modbus master for said one or more outputs when the frequency of requests commanding said one or more outputs, received from said Modbus client, is above a threshold