Medical Gas Heating Wire Control Without Separate Temperature Sensors
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Solution Overview
Problem
Existing medical devices for procedures like laparoscopy and respiration face challenges in accurately controlling gas temperature without incurring additional costs, as separate temperature sensors are costly and disposable, and the relationship between gas temperature and heating wire temperature is complex and dependent on various parameters.
Innovation Solution
A mathematical model based on a state-space representation of the heating wire, electronic measurement system, and gas flow is used to estimate gas temperature at the exit of the hose, allowing for precise control without the need for additional temperature sensors, utilizing a Luenberger observer for error correction and resistance measurements of the heating wire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate temperature sensor is used to measure gas temperature, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The heating wire is merged with the temperature sensing function. The same heating wire that heats the gas also serves as the temperature sensor through resistance measurement, eliminating the need for a separate temperature sensor. This combining of heating and sensing functions in a single component directly resolves the contradiction by maintaining measurement capability while reducing device complexity.
Solution Approach 2:
The heating wire is given dual functionality: it serves both as a heating element and as a temperature sensor. By measuring the electrical resistance of the heating wire, which varies with temperature, the system uses the same component for both heating and temperature measurement purposes, thereby reducing the number of components needed while maintaining measurement precision.
2Measurement precision
If a separate temperature sensor is used to measure gas temperature, then measurement precision is improved, but cost increases
Solution Approach 1:
The heating wire is merged with the temperature sensing function. The same heating wire that heats the gas also serves as the temperature sensor through resistance measurement, eliminating the need for a separate temperature sensor. This combining of heating and sensing functions in a single component directly resolves the contradiction by maintaining measurement capability while reducing device complexity.
Solution Approach 2:
The heating wire is given dual functionality: it serves both as a heating element and as a temperature sensor. By measuring the electrical resistance of the heating wire, which varies with temperature, the system uses the same component for both heating and temperature measurement purposes, thereby reducing the number of components needed while maintaining measurement precision.
3Device complexity
If the relationship between gas temperature and heating wire temperature is used for estimation, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The system employs feedback control where the measured resistance of the heating wire (which correlates with its temperature) is continuously monitored and used to adjust the heating power. This feedback mechanism, combined with the mathematical model, ensures that the gas temperature estimation remains precise by continuously correcting based on actual measurements, thereby resolving the contradiction between reduced complexity and maintained precision.
Solution Approach 2:
The system changes the operational parameters of the heating wire (current, voltage, power) based on the estimated gas temperature and feedback from resistance measurements. By dynamically adjusting these parameters according to the mathematical model and actual measurements, the system maintains precise temperature control despite using an estimation approach rather than direct sensing, thus resolving the precision concern.
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 method ensures precise gas temperature control at the patient-side end, comparable to conventional systems with separate sensors, while eliminating the need for additional hardware, thus ensuring patient safety and reducing costs.
Implementation Method 1
the supplied gas is normally heated, so that the gas entering into the inward parts of the body has nearly body temperature
Implementation Method 2
the measurement of the heating wire temperature can be made by a resistance measurement, so that no additional components are required
Data Source
AI summary
A method is provided for controlling the gas temperature in medical devices by means of a state observer, e.g., in the field of laparoscopy or respiration, and to devices for carrying-out said method.