Linear Compressor Head Crash Detection Using Motor Current Feedback
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Solution Overview
Problem
Detecting head crashes in linear compressors without requiring sensors to determine piston position is challenging due to variations in materials and production, and using sensors can compromise the hermetic seal, allowing contaminants to enter the system.
Innovation Solution
A method that measures the current induced in the motor of a linear compressor using an electrical dynamic model and a robust integral of the sign of the error feedback, allowing for detection of head crashes by comparing the observed current with the measured current and setting a crash threshold, without the need for direct piston position sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is used to measure the position of the piston, then the detection accuracy of head crashing is improved, but the hermetic seal is compromised and contaminants can enter the system
Solution Approach 1:
The patent replaces the mechanical sensor-based position detection system with an electrical current-based detection system. By measuring current induced in the motor and comparing it with observed current from an electrical dynamic model, the system detects head crashes without physical sensors inside the hermetic chamber, thus maintaining seal integrity while achieving detection functionality.
Solution Approach 2:
The patent uses electrical current as an intermediary parameter to indirectly detect piston position and head crash conditions. Instead of directly measuring piston position with sensors, the system measures current which reflects the mechanical state, allowing detection without compromising the hermetic seal.
2Ease of manufacture
If parameters of the linear compressor are kept fixed, then the manufacturing complexity is reduced, but the detection accuracy of head crashing deteriorates due to material and production variations
Solution Approach 1:
The patent implements a feedback mechanism where the electrical dynamic model continuously compares observed current with measured current. This feedback loop allows the system to adapt to parameter variations from manufacturing tolerances and material differences, maintaining detection accuracy without requiring fixed, standardized parameters across all units.
Solution Approach 2:
The patent accounts for parameter variations by using an electrical dynamic model that can accommodate changes in motor resistance, inductance, and other electrical parameters. The model adapts to these parameter changes through continuous monitoring and comparison, allowing accurate head crash detection despite manufacturing variations.
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
Effectively detects head crashes in linear compressors, preventing damage and maintaining the hermetic seal, thus enhancing operational efficiency and reliability.
Implementation Method 1
A current is induced in the driving coil that generates a force for sliding the piston forward and backward within a chamber
Implementation Method 2
measuring a current induced in a motor of the linear compressor
Data Source
AI summary
A method for operating a linear compressor includes measuring a current induced in a motor of the linear compressor and calculating an observed current of the motor of the linear compressor using at least an electrical dynamic model for the linear compressor and a robust integral of the sign of the error feedback. The method also includes detecting a head crash within the linear compressor if an error between the observed current of the motor of the linear compressor and the measured current induced in the motor of the linear compressor is greater than a crash threshold.