Washing Machine Spin Imbalance Detection Across Natural Frequencies

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Solution Overview

Problem

Existing washing machines struggle to accurately detect off-balance loads during spin cycles, leading to severe vibrations and potential damage, as current methods are costly, unreliable, and fail to distinguish between light and heavy cabinet hits, especially at higher spin speeds.

Innovation Solution

A method that utilizes multiple frequency speed signals to detect off-balance conditions by extracting specific frequency signals corresponding to rocking, top or bottom hits, and unstable cabinet hitting, and compares these signals to thresholds to determine the presence of an imbalance, employing different detection schemes for various speed ranges corresponding to translational and rotational natural frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If mechanical switches are used to detect off-balance loads, then detection capability is provided, but cost increases and robustness to levelness deteriorates

Engineering Contradiction:

Improveoff-balance detection capabilityVSAvoidmechanical switch complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical paddle switches with an electrical sensing system that uses motor current measurements and signal processing to detect off-balance conditions. The controller analyzes current signals during spin cycles to identify cabinet hits and determine load balance, eliminating the need for mechanical components while improving reliability and reducing cost.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If existing detection methods are used, then some off-balance detection is provided, but measurement precision deteriorates at higher spin speeds

Engineering Contradiction:

Improvedetection reliabilityVSAvoidoff-balance detection precision

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent implements a dynamic detection system that adapts to different spin speeds by adjusting detection thresholds and parameters. The controller modifies its analysis approach based on the current spin cycle phase and speed, improving measurement precision across the entire operating range rather than being optimized for a single speed condition.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system continuously monitors motor current during spin cycles and uses feedback from detected cabinet hits to determine off-balance conditions. The controller analyzes the frequency and intensity of cabinet impacts in real-time, providing accurate detection even at varying spin speeds through continuous feedback adjustment.

Inventive Principle:

Principle #23Feedback

3Reliability

If detection methods are designed for specific speeds, then detection works at those speeds, but adaptability to different speed ranges deteriorates

Engineering Contradiction:

Improvedetection reliabilityVSAvoidspeed range adaptability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal detection method that functions across all spin speeds by using multiple detection schemes. The system can detect off-balance conditions during both acceleration and steady-state phases, and during both low-speed and high-speed spin cycles, making it adaptable to the entire operational range of the washing machine.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8042211B2Method of detecting an off-balance condition of a clothes load in a washing machine

Publication Date: 2011.10.25 WHIRLPOOL CORP

AI summary

An off-balance detection method comprises a plurality of off-balance detection schemes that utilize wash basket speed to detect an off-balance load condition at speed ranges that span the entire spin cycle and include speeds corresponding to natural frequencies of a mass comprising a wash tub and a wash basket. The schemes can be used alone or in combination with one or more of the other schemes. The off-balance detection method can further comprise a power limiting method to prevent motor overload when an off-balance condition is present.