Infant Incubator Humidity Control to Prevent Condensation Overshoot

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Infant incubators face challenges in controlling temperature and humidity due to their interdependent relationship, leading to modeling difficulties, non-intuitive controller behavior, and overshoots, which complicates the design and implementation of effective servo control systems.

Innovation Solution

The use of separate temperature and humidity control loops, where specific humidity (SH) is employed in the humidity control loop to decouple humidity from temperature, simplifying control and preventing condensation by regulating transient humidity through a humidifier rate saturation controller.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If independent PID control loops are used for temperature and humidity, then the control structure is simpler, but the interdependence between temperature and humidity causes overshoots and requires complex lookup tables for corrections

Engineering Contradiction:

Improvecontrol structureVSAvoidcontrol performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the control parameter from relative humidity to specific humidity (mixing ratio). This parameter transformation decouples the humidity control from temperature dependence, allowing independent PID control without overshoots or complex correction tables, thus resolving the contradiction between simple control structure and reliable control performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a humidity rate saturation controller as an intermediary between the PID controller and the humidifier. This mediator prevents excessive humidity addition rates that would cause overshoots, maintaining reliable control performance while keeping the overall structure simple

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If heaters and humidifiers operate independently with high capacities, then desired temperature and humidity can be achieved, but transient responses compete causing overshoots in one or both parameters

Engineering Contradiction:

Improveachievement of desired performanceVSAvoidtransient response control

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent employs a humidity rate saturation controller that uses feedback from the current humidity state and temperature to dynamically adjust the humidifier rate command. This feedback mechanism prevents overshoots by limiting the humidifier addition rate when approaching the target humidity, enabling reliable performance achievement with smooth transient response

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent makes the humidifier addition rate dynamic rather than fixed, using the saturation controller to adjust the rate based on real-time conditions. This dynamic control prevents competition between heater and humidifier transient responses, eliminating overshoots while maintaining ease of operation

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If relative humidity control is used, then the control is intuitive, but temperature changes cause RH to change even with constant moisture content, complicating the control architecture

Engineering Contradiction:

Improvecontrol intuitivenessVSAvoidcontrol architecture

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent changes the control parameter from relative humidity (temperature-dependent) to specific humidity (temperature-independent). This parameter transformation eliminates the coupling between temperature and humidity control, simplifying the control architecture while maintaining operational intuitiveness through the humidity rate saturation controller

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

This approach allows for improved control of temperature and humidity, reducing the likelihood of condensation and enabling more efficient operation of heaters and humidifiers, thereby enhancing the environmental control within the incubator.

Implementation Method 1

a humidifier to close the control loop

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 2

an air heater and a humidifier to close the control loop

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 3

a fan for circulating air within the interior

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentEP2661247B1Incubator assembly and associated control apparatus that controls humidity rate

Publication Date: 2015.03.18 KONINKLIJKE PHILIPS NV

Figure 1
Figure 2
Figure 3

AI summary

An improved incubator (4) and control apparatus (16) include separate temperature and humidity control loops (36, 38) wherein a commanded temperature (44) and a commanded relative humidity (RH) value (46) are commanded to the control apparatus via a user interface (40). The control apparatus employs a humidifier rate saturation controller (74) which acts responsive to both a humidity control signal (72) and a current temperature (52A) to regulate the addition of humidity to the air within the incubator assembly to avoid a transient humidity from exceeding a predetermined value and thereby avoiding the generation of condensation within the incubator.