Resonant Linear Compressor Power Control Without Position Sensors
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Solution Overview
Problem
Existing control methods for resonant linear compressors in cooling systems face challenges such as high complexity, increased costs, and instability due to the need for position sensors and additional devices like temperature sensors and accelerometers, which are difficult to implement in hermetical and high-temperature environments, and often result in mechanical impacts, noise, and inefficiencies.
Innovation Solution
A control method and system that eliminates the need for sensors by reading and comparing reference operation power with actual motor operation parameters, adjusting the operation voltage using an electronic power device to control piston displacement and prevent mechanical impacts, thereby optimizing compressor capacity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position sensors are used to measure compressor stroke, then measurement precision is improved, but device complexity increases and manufacturing cost increases
Solution Approach 1:
The patent replaces mechanical position sensors with an electrical measurement system that uses motor current and voltage signals to calculate piston displacement. The control system measures motor phase currents and voltages, then computes stroke based on the relationship between electrical parameters and mechanical displacement in the resonant linear compressor, eliminating the need for physical sensors inside the compressor.
Solution Approach 2:
The patent introduces an intermediary calculation method that uses motor electrical parameters (current, voltage, power) as intermediate variables to determine piston stroke. Instead of directly measuring position, the system uses the known relationship between motor input power and piston displacement in resonant compressors to derive stroke information from electrical measurements.
2Measurement precision
If additional sensors (temperature, accelerometer) are added to control capacity, then control precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the control system self-sufficient by using only motor electrical parameters (current and voltage) that are already available in the compressor's control circuitry. The system calculates piston stroke and controls capacity using only the motor's electrical input data, without requiring additional temperature sensors, accelerometers, or other external measurement devices.
Solution Approach 2:
The patent enables the motor's electrical parameters to serve multiple functions: they are used both for normal motor control and for determining piston stroke position and capacity. The same current and voltage measurements that control motor operation also provide the information needed for stroke measurement and capacity regulation, eliminating the need for separate sensing systems.
3Productivity
If piston displacement is increased to vary cooling capacity, then productivity is improved, but risk of mechanical impact increases
Solution Approach 1:
The patent implements a feedback control system that continuously monitors motor electrical parameters to determine real-time piston displacement. Based on the calculated stroke position, the system adjusts motor voltage to prevent excessive displacement that would cause mechanical impact, while still allowing sufficient displacement variation to control cooling capacity according to system needs.
Solution Approach 2:
The patent controls piston displacement by changing motor voltage parameters rather than mechanically limiting stroke. The system adjusts the electrical input to the linear motor, which changes the magnetic field strength and consequently the piston displacement amplitude, allowing capacity control without mechanical constraints that could cause impact.
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 reduces costs, improves operation stability, and minimizes noise peaks by eliminating the need for sensors and complex methods, allowing for efficient control of compressor capacity across wide displacement ranges while maintaining constant power, thus preventing mechanical impacts and power consumption peaks.
Implementation Method 1
a linear actuator, which is formed by a support and magnets that can be actuated by one or more coils
Implementation Method 2
designed for functioning at the resonance frequency of the so-called mass/spring system of the assembly
Implementation Method 3
the so-called equivalent spring is equal to the sum of the resonant spring of the system plus the gas spring generated by the gas compression force
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The present invention relates to a control method and system for a resonant linear compressor, which are especially applied for controlling the capacity of a cooling system. Such a method comprises essentially the following steps: a) reading a reference operation power (IMED) of the motor of the compressor (100); b) measuring an operation current (IMED) of the motor of com compressor (100); c) measuring an operation voltage of a control module of the compressor (100); d) calculating an input power (PMED) of the motor of the compressor (100) as a function of the operation current (IMED) measured in step b) and of the operation voltage obtained in step c); e) comparing the input power (PMED) calculated in the preceding step with the reference operation power (Pref); f) if the reference operation power (PREF) is higher than the input power (PMED), then increase an operation voltage of the compressor (UC); g) if the reference operation power (Pref) is lower than the input power (PMED), then decrease the operation voltage of the compressor (UC).