Washing Machine Drum Inertia Measurement with Constant-Torque Sync Point
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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 and require significant computational resources, especially when implemented with 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 using the formula J=Tacc·Δt·Δω, eliminating the need for integration and reducing measurement errors by accounting for torque oscillations.
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 and measurement accuracy deteriorates due to unbalanced load oscillations
Solution Approach 1:
The patent extracts and eliminates the integration operation from the measurement method. Instead of integrating power with respect to time as in the prior art, the invention directly calculates moment of inertia from instantaneous power and angular velocity measurements, removing the computational burden of integration while maintaining measurement capability
Solution Approach 2:
The patent changes the measurement parameters from power integration over time to direct calculation using instantaneous electrical parameters (voltage, current, angular velocity). This parameter transformation eliminates the need for integration and reduces computational complexity while improving accuracy by avoiding error accumulation
2Productivity
If the acceleration ramp is made short to reduce measurement time, then productivity improves, but measurement accuracy deteriorates due to unbalanced load effects becoming more significant
Solution Approach 1:
The patent introduces feedback mechanisms that continuously monitor electrical parameters (voltage, current, angular velocity) during the acceleration transient. This real-time feedback allows the system to compensate for unbalanced load effects even during short acceleration ramps, maintaining accuracy while enabling faster measurements
Solution Approach 2:
The patent replaces mechanical measurement approaches with electrical parameter-based measurement. By using electrical measurements (voltage, current, power) instead of mechanical sensors, the system achieves higher frequency response and accuracy during short transients, enabling fast measurements without sacrificing precision
3Adaptability or versatility
If the velocity range is widened to accommodate different operating conditions, then adaptability improves, but measurement accuracy deteriorates due to unbalanced load oscillations at certain velocities
Solution Approach 1:
The patent employs dynamic measurement techniques that adapt to different acceleration rates and velocity ranges. The system can perform measurements during various phases of the acceleration transient, allowing flexible adaptation to different operating conditions while maintaining accuracy through real-time electrical parameter monitoring
Solution Approach 2:
The patent creates a universal measurement method that works across different velocity ranges and acceleration profiles. The electrical parameter-based approach is not limited to specific velocity ranges, allowing the same measurement technique to be applied universally across different operating conditions without sacrificing accuracy
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 efficient measurement of the moment of inertia, allowing for implementation with short acceleration transients and reducing computational costs, while accounting for unbalanced loads and friction torques.
Implementation Method 1
set said drum in rotation by means of a permanent magnet synchronous electric motor
Data Source
AI summary
A method for measuring the moment of inertia of a washing machine drum containing a load. The drum is set in a rotation by means of a permanent magnet synchronous electric motor taking it to a first angular spin velocity. The method includes identifying a synchronization point in a periodic signal indicative of the torque provided by the synchronous electric motor at the first angular velocity. An acceleration transient of said drum with constant electromotive torque is provided by the synchronous electric motor. The method further includes interrupting the acceleration transient upon reaching a second angular velocity, acquiring the acceleration transient time duration, and 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, from the transient time duration value, and from the variation of the angular velocity in the transient.