Linear Compressor Piston Position Detection Without Sensors
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Solution Overview
Problem
Determining the top dead center position of a piston in a linear compressor without using sensors is challenging due to varying parameters and the risk of contaminating hermetically sealed systems.
Innovation Solution
A method that estimates the acceleration of the motor using a robust integral of the sign of the error feedback, allowing for calculation of the piston's position at both bottom and top dead center points based on measured current and stroke length, without requiring position, velocity, or acceleration sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is used to measure the top dead center position of the piston, then measurement precision is improved, but device complexity increases and reliability deteriorates due to potential contamination of the hermetically sealed system
Solution Approach 1:
The patent replaces mechanical position sensors with an electrical measurement system. By measuring current draw characteristics and using signal processing techniques (FFT analysis, correlation methods), the system determines piston position electronically without physical sensors penetrating the hermetic seal, thus maintaining system reliability while achieving measurement precision.
Solution Approach 2:
The patent uses electrical current as an intermediary parameter to indirectly determine piston position. Instead of directly measuring position with a sensor, the system measures current draw which varies with piston position, and uses signal processing to extract position information from this intermediate electrical parameter, avoiding direct mechanical contact with the sealed system.
2Adaptability or versatility
If parameters of the linear compressor are kept fixed, then device complexity is reduced, but adaptability deteriorates as parameters need to accommodate various operating conditions
Solution Approach 1:
The system performs self-characterization by automatically measuring its own electrical parameters (current, voltage, frequency) during operation and using these measurements to determine operating conditions and piston position. This self-service approach allows the system to adapt to various operating conditions without requiring external calibration or complex parameter management, as the system uses its own operational data to adjust its control strategy.
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
Enables accurate determination of piston positions within the compressor, preventing head crashing and maintaining system integrity by avoiding sensor usage and potential contamination.
Implementation Method 1
The driving coil receives a current that generates a force for sliding the piston forward and backward within a chamber
Implementation Method 2
estimating an acceleration of the motor of the linear compressor using at least a robust integral of the sign of the error feedback
Data Source
AI summary
A method for operating a linear compressor is provided. The method includes estimating an acceleration of the motor of the linear compressor using at least a robust integral of the sign of the error feedback. A position of the motor of the linear compressor when the motor of the linear compressor is at the bottom dead center point is also determined based at least in part on a measured current to the motor of the linear compressor and an estimated acceleration of the motor. The position of the motor of the linear compressor when the motor of the linear compressor is at a top dead center point is calculated based at least in part on the position of the motor of the linear compressor when the motor of the linear compressor is at the bottom dead center point and a stroke length of the motor of the linear compressor.