Decentralized Redundancy in Process Control Devices
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Solution Overview
Problem
Redundant control systems in automation technology face challenges when both control devices fail or the communication network is disrupted, leading to a loss of process control and potential critical system states.
Innovation Solution
A process device configured as an input/output device with its own intelligence and runtime system executes an emergency control program stored in its memory, allowing it to switch to emergency operation and continue process control when the primary control device fails, and communicate with other process devices for synchronized emergency operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redundant control system uses traditional control devices without embedded intelligence, then device complexity is reduced, but system reliability deteriorates when both control devices fail or communication is disrupted
Solution Approach 1:
The process device is equipped with its own intelligence including an evaluation unit to detect control failures, an emergency control program stored in memory, and a runtime system to execute the emergency program. This self-service capability allows the process device to autonomously switch to emergency operation when control devices fail or communication is disrupted, eliminating the need for external intervention and thereby improving system reliability without significantly increasing overall system complexity
Solution Approach 2:
The control functionality is segmented between the control device and the process device. The control device handles normal operation while the process device contains embedded intelligence for emergency operation. This segmentation allows the system to maintain simplicity in normal operation while gaining reliability through distributed intelligence that activates only when needed
2Reliability
If the process device is equipped with embedded intelligence and runtime system, then system reliability is improved during failures, but device complexity increases
Solution Approach 1:
The process device is pre-equipped with an evaluation unit, emergency control program stored in memory, and runtime system before any failure occurs. These components are prepared in advance and remain dormant during normal operation, only activating when control failure is detected. This preliminary action ensures immediate response to failures without the complexity of real-time decision-making, thereby improving reliability while minimizing the impact on device structure
Solution Approach 2:
The process device is designed with multi-functionality, serving both as a passive I/O device during normal operation and as an autonomous emergency controller when needed. The embedded intelligence allows the same device to perform multiple functions - normal process control under control device supervision and emergency autonomous operation - thereby improving reliability without requiring separate dedicated emergency hardware
3Loss of information
If traditional control systems are used without decentralized redundancy, then device complexity is minimized, but loss of process control occurs when communication network fails
Solution Approach 1:
The system implements local quality by distributing intelligence to individual process devices rather than relying on centralized control. Each process device contains local evaluation units and emergency control programs that enable autonomous operation. This local capability ensures that process control data and control authority remain available at the local level even when communication network fails, preventing total loss of process control without requiring a completely redundant centralized system
Data Source
AI summary
There is provided a control and data transmission system, comprising at least one control device which, in normal operation, is connected by means of a communication network to at least one process device designed as an input and/or output device, wherein the process device comprises an evaluation unit designed to detect a failure in the control system, an emergency control program which can be parameterized and which is stored in a memory of the process device, and a runtime system designed to execute the emergency control program, and wherein the process device is designed to switch to emergency operation in response to a failure in the control system detected by the evaluation unit, in which emergency operation the process device executes the emergency control program. The invention further provides a process device for use in such a control and data transmission system and a method for redundant process control.