Control Signal Protection Device for I/O Card Switchover

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Solution Overview

Problem

Process control systems face disruptions due to interruptions in control signals during switchover operations between primary and backup I/O cards, leading to undesirable responses from field devices, such as valves moving to unintended positions, potentially disrupting the process.

Innovation Solution

A control signal protection device that switches between operational modes, storing energy during normal operation and using it to sustain control signals during interruptions, ensuring continuous operation by monitoring input and output currents and voltages to maintain desired levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If redundant I/O cards are employed to improve system robustness, then system reliability is improved, but control signal interruption occurs during switchover operations

Engineering Contradiction:

Improvesystem robustnessVSAvoidcontrol signal continuity

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The protection device performs preliminary actions by detecting the switchover event before the control signal interruption fully affects the field device. The device monitors the control signal and proactively activates the energy storage circuit to prepare for the impending interruption, switching to protection mode in advance to prevent harmful effects on the field device

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The device implements beforehand cushioning by storing energy in the energy storage circuit during normal operation. This stored energy acts as a buffer or cushion that absorbs the impact of control signal interruptions during switchover operations, maintaining the control signal within safe ranges and preventing the field device from entering harmful states

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Productivity

If I/O card switchover is performed to maintain operation continuity, then system availability is improved, but field devices may respond in undesirable manner due to signal interruption

Engineering Contradiction:

Improveoperation continuityVSAvoidfield device undesirable response

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The protection device serves as an intermediary component between the I/O cards and the field device. It monitors the control signal and detects switchover events, then uses the energy storage circuit to maintain the control signal within safe ranges, preventing the field device from receiving harmful or undesirable signals during the switchover transition

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The device implements feedback by continuously monitoring the control signal and detecting changes that indicate a switchover event. Based on this feedback, the device automatically switches between normal operation mode and protection mode, adjusting its behavior to maintain control signal integrity and prevent harmful effects on the field device

Inventive Principle:

Principle #23Feedback

3Reliability

If periodic I/O card switchover is implemented to verify backup functionality, then system reliability is improved, but control signal interruptions occur periodically

Engineering Contradiction:

Improvebackup functionality verificationVSAvoidcontrol signal interruption time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The protection device ensures continuity of useful action by maintaining the control signal within safe ranges during periodic switchover operations. The energy storage circuit continuously supplies energy to keep the control signal stable, allowing the switchover to occur without interrupting the control function and enabling periodic verification without process disruption

Inventive Principle:

Principle #20Continuity of useful action

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

The solution prevents disruptions by maintaining control signal integrity during I/O card switchover, reducing the risk of field devices entering undesired states and ensuring process stability by using stored energy to sustain signal levels during temporary interruptions.

Implementation Method 1

a power storage element for temporary storage of electric energy... storing of electric energy... supplying of electric energy from the power storage element

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentEP2885682B1Control signal protection device

Publication Date: 2019.04.24 FISHER CONTROLS INT LLC

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AI summary

A control signal protection device (210) having a first operational mode and a second operational mode includes a first terminal that connects the signal protection device (210) to a control system (202) and a second terminal that connects the control signal protection device (210) to a field device (220). The control signal protection device (210) further includes a power storing element for temporary accumulation of electric energy and a switching circuit for controlling operational mode of the signal protection device (210). Electric energy is stored in the power storing element in the first operational mode. Electric energy stored in the power storing element is supplied to a positive terminal in the second terminal pair in the second operational mode.