Output Module Slice Current Control for Fault-Tolerant Failover

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Solution Overview

Problem

Current fault-tolerant safety control systems face challenges in maintaining continuous operation and minimizing fault detection periods, particularly in systems relying on software-implemented fault tolerance, which can introduce communication overhead and disrupt system operation during module changes.

Innovation Solution

The implementation of an output module slice that includes an output field interface controller for a first field effect transistor, an analogue to digital converter to monitor current, and a pulse ratio modulation signal to control input voltage, along with a second field effect transistor enabled by an external signal, ensures fault tolerance and fail-safe operation by regulating current and monitoring voltages across a shared load.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If software-implemented fault tolerance is used, then fault detection and redundancy management can be achieved, but communication overhead increases and system operation may be disrupted during module changes

Engineering Contradiction:

Improvefault toleranceVSAvoidcommunication overhead

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces software-implemented fault tolerance with hardware-implemented fault tolerance (HIFT). The field interface controller uses dedicated hardware circuits including triplicated voting circuits and hot-standby modules to detect faults and manage redundancy, eliminating the need for software-based fault detection and communication protocols. This substitution of hardware for software directly resolves the communication overhead problem while maintaining fault tolerance capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements hot-standby modules that are pre-configured and ready to immediately take over if an active module fails. The standby modules maintain identical operational states through continuous synchronization, allowing instant failover without system disruption. This preliminary preparation of backup systems eliminates the time loss associated with module changes and software reconfiguration.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If hot-standby modules are used for fault tolerance, then system operation can be maintained during module failure, but disruption occurs during the changeover period

Engineering Contradiction:

Improvecontinuous operationVSAvoidchangeover disruption

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent ensures continuous operation by maintaining both active and standby modules in parallel, with the standby module continuously synchronized to the active module's state. When a failure occurs, the standby module immediately takes over without interruption to the controlled process. This continuous parallel operation and instant failover mechanism eliminates changeover disruption while maintaining reliability.

Inventive Principle:

Principle #20Continuity of useful action

3Reliability

If triplicated circuits are used with majority voting, then fault tolerance is achieved, but system complexity increases

Engineering Contradiction:

Improvefault toleranceVSAvoidcircuit triplication

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the field interface controller into three independent triplicated modules, each capable of performing the complete control function independently. Each module processes inputs and generates outputs separately, with a voting circuit that compares the three outputs and selects the majority value. This segmentation into independent functional units provides fault tolerance while organizing the complexity into manageable, identical modules that can be systematically implemented and tested.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution provides enhanced fault tolerance and fail-safe operation by eliminating communication overhead, enabling continuous system operation with automatic fault recovery and minimal disruption, ensuring the system remains operational even in the event of module failures.

Implementation Method 1

an output field interface controller for controlling an input voltage to a first field effect transistor

Methodology Applied

Scientific EffectField effect transistor operation: Electric Field

Implementation Method 2

an analogue to digital converter connected to read the current flowing through said first field effect transistor and to provide a digital signal dependent thereon

Methodology Applied

Scientific EffectAnalogue to digital conversion:

Implementation Method 3

the interface controller is arranged in operation to control the input voltage to the first field effect transistor by generating a pulse ratio modulated signal

Methodology Applied

Scientific EffectPulse ratio modulation: Phase Modulation

Data Source

PatentUS7504975B2Method and apparatus for output current control

Publication Date: 2009.03.17 ICS TRIPLEX EMEA PLC

AI summary

This invention relates to a method and apparatus for output current control. The invention provides an output module slice for controlling an output current comprising: an output field interface controller for controlling an input voltage to a first field effect transistor; an analogue to digital converter connected to read the current flowing through said first field effect transistor and to provide a digital signal dependent thereon to said output field interface controller.