Washer Suspension Displacement Sensing via Coil Frequency Measurement
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Solution Overview
Problem
Existing household laundry washing machines face challenges in accurately measuring the relative displacement between the swinging assembly and the frame due to the limitations of analog signal processing, which requires expensive components and is prone to noise interference, making it costly and unreliable for detecting small movements.
Innovation Solution
A digital measurement system using an oscillator circuit with a coil whose oscillation frequency depends on the impedance, allowing for precise measurement of relative displacement through frequency analysis by a microcontroller, reducing costs and improving accuracy by processing signals locally and compensating for external interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall-effect sensing devices with permanent magnets are used to measure relative displacement, then displacement detection is enabled, but the cost increases due to expensive rare-earth magnets and the detection accuracy remains insufficient for small movements
Solution Approach 1:
The patent replaces the mechanical Hall-effect sensing system with permanent magnets with an electromagnetic sensing system using a coil and ferromagnetic element. The coil's inductance varies with the position of the ferromagnetic element, providing a cost-effective alternative that eliminates rare-earth magnets while enabling precise displacement measurement through electrical impedance changes.
Solution Approach 2:
The patent measures displacement by detecting changes in the electrical parameters (impedance, inductance) of the coil rather than using mechanical Hall-effect sensors. By applying AC voltage and measuring the resulting current or impedance variations, the system translates mechanical displacement into electrical parameter changes, achieving both accuracy and cost-effectiveness.
2Reliability
If analog electronic circuits are used to process displacement sensor signals, then displacement measurement is achieved, but the system becomes costly due to strict tolerance requirements and is prone to noise interference
Solution Approach 1:
The patent replaces complex analog signal processing circuits with a simpler electromagnetic sensing system. By using a coil whose impedance directly reflects displacement and measuring this impedance with AC voltage application, the system eliminates the need for complex analog processing chains, reducing both cost and noise susceptibility while maintaining measurement reliability.
Solution Approach 2:
The coil itself serves dual purposes: it is both the sensing element (detecting displacement through impedance changes) and the signal source (generating the measurement signal through AC voltage application). This self-service approach eliminates the need for separate, complex signal processing electronics, simplifying the overall system while improving reliability.
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 solution provides accurate and reliable measurement of relative displacement and associated quantities like weight and load imbalance, enhancing the operational efficiency of laundry washing machines while reducing the workload on the electronic control system and minimizing noise immunity issues.
Implementation Method 1
an oscillation frequency f which depends on an impedance L of a coil (9) whose inner volume is adapted to house the first end
Implementation Method 2
a first of said two ends (4) comprises ferromagnetic material
Data Source
Figure 1~4
Figure 2a~2b
Figure 3
AI summary
The present invention relates to a household appliance for treating soft goods, in particular a laundry washing machine, comprising a swinging assembly elastically constrained to a frame by means of a suspension system comprising a pair of elements telescopically coupled together through two respective ends, wherein the first of said two ends comprises ferromagnetic material and the second end comprises a coil (9). The household appliance also comprises an electronic detection module (6) comprising an oscillator circuit (12), the oscillation frequency of which depends on the impedance of the coil (9), and processing means operationally connected to the oscillator circuit (12) and adapted to measure the oscillation frequency and to determine, as a function of said oscillation frequency, at least one piece of information which can be associated with said relative displacement.