Range Hood Fan Control Using Virtual Airflow Sensing
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Solution Overview
Problem
Existing extraction hoods face inefficiencies due to the need for constant air flow rate monitoring and filter obstruction detection, which is hindered by the reliability issues of sail switches and increased noise from resonance phenomena, leading to higher maintenance costs and noise pollution.
Innovation Solution
A system that estimates air flow rate using electromechanical quantities such as current and revolution speed of the fan motor, eliminating the need for physical sensors and allowing for constant flow rate adjustment and noise reduction through virtual sensing and control algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sail switches are used to sense air flow rate and maintain constant efficiency, then air treatment efficiency is maintained, but the sail switch may break or get stuck due to dirt, preventing flow rate measurement and requiring frequent maintenance
Solution Approach 1:
The patent replaces the mechanical sail switch with an electromagnetic flow sensor that uses a magnet and coil assembly. This electromagnetic system has no moving parts that can get stuck or break from dirt accumulation, eliminating the maintenance issues associated with mechanical sail switches while maintaining accurate flow rate measurement capability
Solution Approach 2:
The patent extracts the sensing function from the mechanical sail switch and implements it through a separate electromagnetic field-based system. The magnet is positioned in the air flow path and the coil detects changes in magnetic flux, separating the sensing mechanism from the mechanical components that were prone to failure
2Productivity
If fan speed is increased to maintain air flow through obstructed filters, then air treatment continues, but noise increases due to resonance phenomena
Solution Approach 1:
The patent implements a feedback control system where the electromagnetic flow sensor continuously monitors air flow rate and provides signals to the controller. The controller adjusts fan speed based on this feedback to maintain constant air flow through the filters, preventing the need to operate at high speeds that would trigger resonance and excessive noise
Solution Approach 2:
The patent changes the operating parameters of the fan motor by using pulse width modulation (PWM) control to vary the duty cycle. This allows precise control of fan speed to maintain optimal air flow without exceeding resonance thresholds, thereby controlling noise while ensuring continuous air treatment
3Productivity
If multiple apparatuses including air extractors and fans are used to ensure air changes, then air changes are achieved, but the number of apparatuses increases leading to higher fixed and variable costs
Solution Approach 1:
The patent makes the extraction hood multi-functional by enabling it to perform both fume extraction and room air changes simultaneously. The electromagnetic flow sensor and controller system allows the hood to maintain constant air flow that satisfies both extraction efficiency requirements and air change rate requirements, eliminating the need for separate air extractor apparatuses
Solution Approach 2:
The patent merges the functions of the extraction hood with air change provision. By using the hood's air flow system to simultaneously achieve both fume removal and room ventilation, the patent consolidates what would traditionally require multiple separate apparatuses into a single integrated system
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 maintains consistent air flow and reduces noise while minimizing maintenance costs by using measurable electrical and mechanical parameters to control the fan operation, ensuring efficient air treatment and proper installation without the need for additional sensors.
Implementation Method 1
a first sensor of an electromagnetic type adapted to measure a value corresponding to the flow rate of the air flow by means of variations in the electromagnetic field generated by the fan motor
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a hood (1) comprising an inlet section (20) and an outlet section (50) respectively allowing the entry and exit of an air flow (60), fan means (30), filter means, and a control unit (70) operationally connected to said fan means (30) for controlling at least one operating parameter thereof, so as to take a measurement of the flow rate of the air flow (60) following the activation of an electric motor (31) associated with said fan means (30), after the detection of said at least one operating parameter.