Sensorless EC Fan Control for Constant Ventilation Airflow
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Solution Overview
Problem
Ventilation systems with EC motors face challenges in maintaining a constant volume flow rate due to varying back pressure and flow resistance, requiring complex sensor-based control methods that are prone to errors and high technical complexity, especially in applications with unknown or changing conditions.
Innovation Solution
A sensorless method for controlling EC motor fans in ventilation devices, which involves defining a field of operating points for different target volume flow rates and using motor control variables like power consumption and speed to adjust the fan operation, allowing for automatic adjustment and maintenance of a desired operating point without pressure or volume flow sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensor-based control methods are used to maintain constant volume flow rate, then control precision is improved, but device complexity and susceptibility to errors increase
Solution Approach 1:
The patent extracts and eliminates the sensor component from the control system. Instead of using pressure sensors or volume flow sensors to detect system state, the invention uses a model-based approach that calculates the actual volume flow rate from motor control variables and stored characteristic curves, thereby removing the need for physical sensors and reducing system complexity
Solution Approach 2:
The patent replaces the mechanical/sensor-based detection system with a computational model. The control device uses stored characteristic curves and motor control variables (electrical current, speed) to calculate and determine the actual volume flow rate, substituting physical measurement with mathematical modeling and computation
2Measurement precision
If pressure sensors or volume flow sensors are installed to detect operating conditions, then measurement accuracy is improved, but reliability decreases due to contamination and errors
Solution Approach 1:
The patent removes pressure sensors and volume flow sensors from the system entirely. The control device determines back pressure and volume flow rate through computational methods using stored characteristic curves and motor variables, eliminating the reliability issues associated with sensor contamination and failure
Solution Approach 2:
The patent introduces stored characteristic curves as an intermediary between the motor control variables and the actual system state. These pre-stored curves serve as a reference model that allows the control device to infer back pressure and volume flow rate without direct sensor measurement, avoiding contamination issues
3Use of energy by moving object
If EC motors are used with standard fan characteristic curves, then energy efficiency is improved, but adaptability to varying back pressure conditions deteriorates
Solution Approach 1:
The patent implements dynamic adaptation by storing multiple fan characteristic curves corresponding to different back pressure conditions. The control device dynamically selects and uses the appropriate characteristic curve based on current operating conditions, allowing the EC motor to efficiently adapt to varying back pressure while maintaining energy efficiency
Solution Approach 2:
The patent changes the parameter set by storing characteristic curves for multiple back pressure values rather than a single fixed curve. This allows the system to adjust to varying back pressure conditions by selecting the appropriate pre-stored curve, maintaining both efficiency and adaptability
Data Source
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AI summary
Method and apparatus for adjusting an EC motor-operated fan of a ventilation device (700) to an operating point in order for the ventilation device to obtain and maintain a predefined target volume flow rate without using any pressure sensor nor any volume flow sensor. An operating point is set to a first characteristic curve associated with a predefined value of the target volume flow rate. If a deviation (318), in which a value of a motor control variable differs from the value associated with the obtained value of the motor control variable at the set operating point, is detected, a temporary operating point selected from among an available set of operating points is reached (320). This process is done iteratively until the detected value of the motor control variable no longer differs from the value associated with the auxiliary value of the motor control variable at the currently set auxiliary operating point, and the auxiliary operating point set in this manner is thus verified (324). Thereafter, an operating point is reached which corresponds to the desired target volume flow rate (326).