Fail-Safe Remote Control Safety Filter for Patient Table

Solution Overview

Problem

In safety-critical environments, such as medical facilities, wireless remote controls used to adjust patient tables face challenges in detecting errors in micro-controllers connected to relays, leading to potential uncontrolled movements that can be hazardous, as error conditions in semiconductor and software systems are difficult to detect and may result in unsafe situations.

Innovation Solution

A fail-safe interface with a safety filter is implemented, utilizing a band-pass filter and transformer to ensure that only valid frequency range signals activate the relay, providing a redundant signal path and using well-known reliable components to prevent uncontrolled movements by halting the patient table in case of an error condition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a micro-controller is connected to a relay to control patient table movements, then the control functionality is improved, but the detectability of error conditions deteriorates due to semiconductor and software complexity

Engineering Contradiction:

Improvecontrol functionalityVSAvoiderror detection difficulty

Core Design Contradiction:

Ease of operationVSDifficulty of detecting and measuring

Solution Approach 1:

An optical intermediary (LED and photodetector) is introduced between the micro-controller and relay to create a detectable error condition. The optical coupling allows error detection through light signal monitoring, solving the problem of undetectable semiconductor/software failures while maintaining control functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electrical connection between micro-controller and relay is replaced with an optical system (LED-photodetector coupling). This substitution enables error detection through optical signal monitoring, transforming an undetectable electrical/software system into one with detectable failure modes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If standard relay control is used without additional safety measures, then the device complexity is reduced, but the reliability deteriorates due to undetectable error conditions

Engineering Contradiction:

Improvecontrol system complexityVSAvoidsafety reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

An optical intermediary (LED and photodetector) is introduced between the micro-controller and relay to create a detectable error condition. The optical coupling allows error detection through light signal monitoring, solving the problem of undetectable semiconductor/software failures while maintaining control functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electrical connection between micro-controller and relay is replaced with an optical system (LED-photodetector coupling). This substitution enables error detection through optical signal monitoring, transforming an undetectable electrical/software system into one with detectable failure modes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If frequency range validation is implemented in the safety filter, then the reliability is improved by preventing erroneous signals, but the device complexity increases due to additional signal processing requirements

Engineering Contradiction:

Improvesignal validation reliabilityVSAvoidsignal processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The safety filter validates signals by checking frequency parameters. Only signals within a specific frequency range (corresponding to valid button press durations) can activate the relay. This parameter-based validation prevents erroneous signals while using simple analog circuitry rather than complex digital processing.

Inventive Principle:

Principle #35Parameter changes

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 effectively prevents hazardous uncontrolled movements by ensuring that the patient table stops immediately upon detecting an error condition, adhering to safety standards like IEC 61508 by using reliable components and reducing the complexity of failure analysis, thus enhancing safety in medical and similar environments.

Implementation Method 1

a transformer that is known from the past to be reliable enough to be used in fail-safe systems

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

the safety filter comprises a band-filter that outputs a relay control activation signal only when the micro-controller outputs a signal with a main component that lies within a certain frequency range

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Data Source

PatentUS8125309B2Fail-safe remote control

Publication Date: 2012.02.28 KONINKLIJKE PHILIPS NV

AI summary

The present invention relates to a remote control (160) operates fail-safe. The remote control comprises a safety filter (150) in order to provide a fail save operation. The present invention also relates to an adjustable patient table (100) comprising a fail-safe wireless remote control for controlling an actuator to adjust the table.