Ventilator Solenoid Valve Opening Control Under Coil Heating Drift
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Solution Overview
Problem
Existing ventilation systems face issues with precise control of gas pressure and flow due to systematic drift in current intensity caused by coil heating and temperature changes, leading to poor regulation of proportional solenoid valves.
Innovation Solution
An electronic control system adjusts the electrical current supplied to the solenoid valve coil using a DC/DC converter and shunt resistor to maintain precise control of the orifice opening, compensating for temperature-induced resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If variable voltage or PWM control is used to adjust coil current, then the degree of opening of the orifice can be modified, but systematic drift of current intensity occurs due to coil heating and temperature increase
Solution Approach 1:
The patent implements a feedback control system using a shunt resistor to measure the actual current intensity in real-time. The microcontroller continuously monitors the voltage across the shunt resistor and adjusts the PWM duty cycle to compensate for current drift caused by temperature changes, thereby maintaining stable orifice opening despite coil heating
Solution Approach 2:
The patent replaces simple voltage control with an electronic feedback control system. Instead of directly controlling coil voltage, the system uses a shunt resistor for current measurement and a microcontroller with PWM output to regulate current through feedback, substituting mechanical/electrical direct control with an intelligent electronic control mechanism
2Ease of operation
If fixed voltage with current chopping is used to control the coil, then current intensity can be varied, but the regulation of gas pressure and flow becomes poor due to resistance changes
Solution Approach 1:
The feedback mechanism continuously measures actual current through the shunt resistor and compares it with the desired current level. The microcontroller adjusts the PWM duty cycle in real-time to compensate for resistance changes in the coil due to temperature, thereby maintaining precise control over gas pressure and flow despite the inherent instability of fixed voltage control
Solution Approach 2:
The patent dynamically changes the PWM duty cycle parameter based on real-time current measurements. Instead of using a fixed voltage or duty cycle, the system continuously adjusts the PWM parameter to compensate for changing coil resistance, thereby maintaining precise control of gas flow and pressure throughout operation
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 ensures precise regulation of gas pressure and flow by compensating for temperature-induced resistance changes in the solenoid valve coil, enhancing the accuracy of gas delivery in medical ventilators.
Implementation Method 1
comprising a coil which is supplied electrically
Implementation Method 2
proportional solenoid valve comprising an orifice for passage of gas with an adjustable degree of opening
Implementation Method 3
the lack of compensation for the systematic drift of the current (i.e. intensity) regulated when the coil is heated by joule effect
Data Source
AI summary
The disclosure concerns a ventilation apparatus (1) having an internal gas circuit (2) in order to convey a gas, and at least one proportional solenoid valve (4, 40, 400) with an orifice (4.1) for passage of gas with an adjustable degree of opening, arranged on the internal gas circuit (2), and comprising a coil (4.2) which is supplied electrically. An electronic control (5) controls the degree of opening of the orifice for passage of gas (4.1) of the proportional solenoid valve (4, 40, 400), by acting on the electrical current supplied to the coil (4.2) of the proportional solenoid valve (4, 40), to supply a desired flow or pressure of gas. The electronic control (5) comprise an 10 electronic circuit (10) which is configured to adjust the intensity of the electrical current supplied to the coil (4.2) according to a predetermined voltage set point (Vset).