Linear Compressor Back-EMF Position Estimation to Prevent Piston Collision
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Solution Overview
Problem
Linear compressors face challenges in accurately detecting the absolute position of a piston without a separate sensor, leading to difficulties in controlling piston movement and resulting in noise and potential collisions, which affect efficiency and lifespan.
Innovation Solution
A control system that uses motor voltage and current sensing to estimate piston position, calculate compensation values, and adjust motor control to maintain the piston's position within predetermined limits, eliminating the need for additional sensors and enhancing operational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate sensor is used to detect piston position, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system uses the motor's own voltage and current signals to detect piston position, allowing the motor to serve dual purposes as both actuator and sensor. The controller analyzes back-EMF and current characteristics inherent in the motor operation to infer piston position without external sensing equipment.
Solution Approach 2:
The patent replaces mechanical sensors and position detection devices with an electrical field-based detection method. By monitoring electrical parameters (voltage, current, back-EMF) of the linear motor, the system substitutes physical contactless sensing with electrical signal analysis, reducing mechanical complexity.
2Device complexity
If piston position is not accurately controlled, then device complexity is reduced, but noise and harmful factors increase
Solution Approach 1:
The controller continuously monitors motor current and voltage signals to detect piston position in real-time. Based on this feedback, the controller dynamically adjusts the driving voltage to prevent the piston from reaching the collision zone, thereby eliminating noise while maintaining simple device architecture.
Solution Approach 2:
The system detects approaching piston position through electrical signals and applies preliminary corrective action by adjusting the driving voltage before the piston reaches the collision point. This preventive control stops the harmful collision from occurring in the first place.
3Productivity
If stroke voltage is increased to improve compression ratio, then productivity is improved, but reliability deteriorates due to piston collision risk
Solution Approach 1:
The system dynamically adjusts the stroke voltage based on real-time piston position detection. Rather than using fixed high voltage, the controller modulates voltage according to the piston's actual position and load conditions, allowing high compression ratios when needed while preventing collisions under varying operating conditions.
Solution Approach 2:
The patent changes the electrical parameters (voltage, current) of the linear motor based on detected piston position and load variations. By dynamically adjusting these parameters, the system achieves high compression ratios when required while maintaining safe operating margins to prevent piston collision and maintain 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 approach reduces noise and wear by preventing piston collisions, extends the lifespan of components, and enables efficient operation without additional sensors.
Implementation Method 1
a linear motor is used... a motor providing a driving force for movement of the piston
Implementation Method 2
a sensing unit sensing a motor voltage and a motor current related to the motor
Data Source
Figure 1A~1B
Figure 1C
Figure 1D~2
AI summary
Provided is a linear compressor capable of reducing noise and manufacturing cost. The linear compressor includes a piston (142) reciprocating within a cylinder (141), a motor (130) providing a driving force for movement of the piston, a sensing unit sensing a motor voltage and a motor current related to the motor, a discharge part (2b) installed at one end of the cylinder and adjusting discharge of a refrigerant compressed within the cylinder, and a controller (25) detecting a load variation of the motor using at least one of the motor voltage and the motor current, calculating a compensation value related to a position of the piston each time a load variation of the motor is detected, and detecting an absolute position of the piston using the calculated compensation value.