Backward-Curved Centrifugal Fan Flow Control Without Sensors

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Solution Overview

Problem

Backward curved centrifugal fans face challenges in accurately controlling volume flow rate without sensors, due to ambiguous dependency between motor current and flow rate, and are further complicated by external influences and disturbances, making closed-loop control difficult.

Innovation Solution

A method utilizing an artificial neural network to determine actual flow values by analyzing operation parameters such as motor current and voltage, and their time-dependent changes, allowing for precise open-loop or closed-loop control of gas flow without the need for flow sensors, by considering the relationship between these parameters and output pressure or volume flow rate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If no sensor for measurement of the volume flow rate is present, then the device complexity is reduced, but the measurement precision and control accuracy deteriorate due to ambiguous dependency between motor current and flow rate

Engineering Contradiction:
Improvedevice complexityVSAvoidmeasurement precision
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary computational model that processes multiple measurable parameters (motor current, voltage, frequency, temperature) to indirectly determine volume flow rate. This mediator translates ambiguous individual measurements into accurate flow rate estimation through mathematical relationships, eliminating the need for direct flow sensors while maintaining measurement precision.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces mechanical/physical flow measurement systems (flow sensors, differential pressure sensors) with an electronic computational system. By substituting physical measurement devices with algorithmic processing of electrical parameters, the system reduces device complexity while maintaining or improving measurement accuracy through the use of trained neural networks or lookup tables.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If mathematical or algorithmic modeling is used to control volume flow rate, then the device complexity is reduced, but the manufacturing precision and control accuracy deteriorate due to relatively inaccurate adjustment

Engineering Contradiction:
Improvedevice complexityVSAvoidcontrol accuracy
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The patent performs preliminary action by pre-training neural networks or pre-calculating lookup tables during the manufacturing phase. Extensive training data is collected and processed beforehand to create highly accurate models that are then deployed in the operating system. This preliminary preparation enables precise control accuracy during operation without requiring complex real-time computational resources.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent transforms the control approach by changing from simple mathematical formulas to sophisticated parameter relationships captured in trained neural networks. By incorporating multiple parameters (current, voltage, frequency, temperature) and their interactions, the system achieves high precision control. The trained models capture non-linear relationships and cross-parameter dependencies that simple algorithms miss.

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If sensor measurement is used for closed loop control, then the measurement precision is improved, but the device complexity and cost increase due to numerous external influence and disturbance variables

Engineering Contradiction:
Improvemeasurement precisionVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the control system universal by designing it to handle multiple functions with existing components. The same set of sensors (current, voltage, frequency, temperature) used for basic motor control also serve flow rate measurement. The computational model universally processes these parameters to simultaneously achieve motor control and flow measurement, eliminating the need for dedicated flow sensors and reducing overall system complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentUS11746794B2Method for operating a fan system and fan system having a backward curved centrifugal fan
Publication Date: 2023.09.05 EBM PAPST MULFINGEN GMBH & CO KG
  • US11746794B2 patent drawing
  • US11746794B2 patent drawing
  • US11746794B2 patent drawing

AI summary

A method for operating a fan system as well as such a fan system. The fan system has a control device having an artificial neural network. The control device controls an electric motor of a backward curved centrifugal fan. The centrifugal fan creates a gas flow that is characterized by an actual flow value, particularly the actual value of a volume flow rate. The actual flow value is not detected by a sensor means, but determined by means of the artificial neural network depending from input variables and based thereon, the electric motor is open loop or closed loop controlled by means of the control device. The motor current and the motor voltage as well as their time-dependent behavior that can be the time derivative (e.g. gradient of first order) or that can be at least one preceding value at a preceding point in time, are provided to an input layer of the artificial neural network. It is particularly advantageous, if the artificial neural network determines an actual value of an output pressure that is fed back internally or externally forming an input variable for the input layer.