Washing Machine Drum Inertia Measurement Under Unbalanced Loads
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Solution Overview
Problem
Existing methods for measuring the moment of inertia of a washing machine drum are inaccurate due to unbalanced loads, require significant computational resources, and are limited by design, especially during short acceleration ramps.
Innovation Solution
A method using a permanent magnet synchronous electric motor to set the drum in rotation, identify a synchronization point for a constant torque acceleration transient, and calculate the moment of inertia based on the torque and angular velocity changes, eliminating the need for integration and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the prior art method integrates power with respect to time to determine moment of inertia, then the measurement can be performed, but the computational weight becomes considerable
Solution Approach 1:
The patent extracts only the essential measurement parameters (torque, angular acceleration) needed to calculate moment of inertia directly through algebraic operations, eliminating the computationally intensive time integration step while preserving measurement accuracy
Solution Approach 2:
The patent changes the mathematical approach from integrating power over time to using direct algebraic calculation based on torque and angular acceleration parameters, reducing computational complexity while maintaining measurement capability
2Loss of time
If the drum acceleration transient is short, then the measurement time is reduced, but the measurement accuracy deteriorates due to unbalanced load oscillations
Solution Approach 1:
The patent uses feedback by continuously monitoring angular acceleration during the transient and using it to compensate for unbalanced load effects, allowing accurate measurement even during short acceleration periods where traditional methods would fail
Solution Approach 2:
The patent dynamically adjusts the measurement approach by using real-time angular acceleration data to account for varying load conditions during the transient, enabling accurate measurement in short-duration events
3Adaptability or versatility
If the load is unbalanced in the drum, then the power oscillation increases, but the moment of inertia measurement becomes inaccurate
Solution Approach 1:
The patent converts the harmful effect of power oscillation due to unbalanced loads into a useful measurement signal by using angular acceleration data to distinguish between oscillatory components and the true moment of inertia, thereby achieving accurate measurement despite load imbalance
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 method provides more accurate and computationally efficient measurement of the drum's moment of inertia, allowing for implementation during short acceleration transients and reducing errors caused by unbalanced loads.
Implementation Method 1
a permanent magnet synchronous electric motor for setting the drum in rotation
Implementation Method 2
processing an indirect measurement of the moment of inertia of the drum starting from a value of the torque yielded to the drum during the acceleration transient
Data Source
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AI summary
Method for measuring the moment of inertia of a washing machine drum containing a load, comprising the steps of: - set said drum in rotation by means of a permanent magnet synchronous electric motor taking it to a first angular spin velocity (100-101); - identifying a synchronisation point in a periodic signal indicative of the torque provided by the synchronous electric motor at said first angular velocity (104); - starting, at said synchronisation point, an acceleration transient of said drum with constant electromotive torque provided by the synchronous electric motor (105); - interrupting the acceleration transient upon reaching a second angular velocity (107); - acquiring the acceleration transient time duration (106); - processing an indirect measurement of the moment of inertia of said drum starting from a value of the torque yielded to the drum during the acceleration transient, from the transient time duration value, and from the variation of the angular velocity in the transient, according to the formula: J=Tacc⋅ΔtΔω