Blower Airflow Estimation Using Torque Feedback at Limit Conditions

Solution Overview

Problem

Existing blower systems with variable speed motors face challenges in maintaining constant airflow when operating at limit conditions, leading to reduced effectiveness and potential system damage, as they lack accurate airflow estimation methods, especially when using constant torque or speed modes.

Innovation Solution

A method for estimating airflow in characterized blower systems involves iteratively calculating and revising torque and airflow estimates using a starting airflow assumption, torque error calculation, and correction factors until the torque error is within an acceptable range, allowing for accurate airflow estimation and system control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If variable speed motors are used to provide constant airflow over a range of system static pressures, then airflow stability is improved, but accurate airflow estimation becomes difficult when operating at limit conditions

Engineering Contradiction:

Improveairflow stabilityVSAvoidairflow estimation accuracy

Core Design Contradiction:

Stability of the object's compositionVSMeasurement precision

Solution Approach 1:

The system uses feedback control by continuously monitoring motor operating parameters (current, voltage, speed) and comparing actual performance against expected performance from system characterization data. The controller adjusts motor operation to maintain desired airflow, using the feedback loop to compensate for deviations caused by limit conditions or system changes.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces an intermediary estimation model that translates easily measurable motor parameters (current, speed, voltage) into airflow estimates. This intermediary relationship allows the system to infer airflow without direct measurement, using the motor's electrical characteristics as a mediator between control inputs and airflow output.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If airflow sensors are installed in duct work to measure actual airflow, then measurement accuracy is improved, but system cost and reliability are worsened

Engineering Contradiction:

Improveairflow measurement accuracyVSAvoidsystem cost and reliability

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary estimation model that translates easily measurable motor parameters (current, speed, voltage) into airflow estimates. This intermediary relationship allows the system to infer airflow without direct measurement, using the motor's electrical characteristics as a mediator between control inputs and airflow output.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention replaces the mechanical/physical airflow sensing system with an electrical-based estimation approach. Instead of using physical sensors in the ductwork to directly measure airflow, the system uses electrical measurements from the motor controller and computational models to estimate airflow, substituting a simpler electrical measurement system for a complex mechanical sensing system.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Speed

If the motor operates at limit conditions such as speed limit, torque limit or power limit, then system responsiveness is improved, but delivered airflow becomes much less than demanded airflow

Engineering Contradiction:

Improvesystem responsivenessVSAvoiddelivered airflow

Core Design Contradiction:

SpeedVSProductivity

Solution Approach 1:

The system performs preliminary system characterization during installation or commissioning, establishing the relationship between motor operating parameters and airflow for that specific system configuration. This preliminary data is stored and used by the controller to predict and compensate for airflow deviations before they occur, allowing the system to maintain accurate airflow control even when approaching limit conditions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback control by continuously monitoring motor operating parameters (current, voltage, speed) and comparing actual performance against expected performance from system characterization data. The controller adjusts motor operation to maintain desired airflow, using the feedback loop to compensate for deviations caused by limit conditions or system changes.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8175836B2Flow estimation for fluid handling system

Publication Date: 2012.05.08 NIDEC MOTOR CORP

AI summary

A method of estimating airflow for a characterized blower system including a motor. The method includes running the motor, estimating a torque and a speed of the running motor, and assuming a starting airflow estimate. Torque is calculated based on the estimated speed and the estimated airflow. A torque error is calculated as a function of the calculated torque and the estimated torque. Estimated airflow is revised based on the calculated torque error. The method also includes repeating the calculating and revising steps using the revised estimated airflow until the torque error is within a predetermined acceptable range.