Linear Motor Control via Resonance Frequency Detection
Solution Overview
Problem
The phase difference evaluation function in existing linear motor systems is challenging to control accurately due to its dependency on the variable inductance of the motor coil, which is influenced by the mover's position, making precise control of angular frequency difficult.
Innovation Solution
A linear motor system with a position detection unit, a position estimation unit, and a control unit that adjusts the AC power frequency based on detected or estimated positions and currents, allowing for precise control of the phase difference and angular frequency by applying signals with specific frequencies to the position detection or current detection outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the phase difference evaluation function is used to control angular frequency, then the control system can operate, but the control accuracy deteriorates due to inductance variability
Solution Approach 1:
The patent replaces the conventional electrical-based phase difference control method with a mechanical resonance-based control method. By detecting the resonance frequency of the mover through position or current detection and controlling the linear motor to operate at this resonance frequency, the system achieves accurate control independent of inductance variations. This substitution of control basis from electrical phase difference to mechanical resonance frequency resolves the accuracy problem caused by inductance variability.
2Reliability
If the inductance-based phase difference control is used, then the system can function, but the control complexity increases due to variable parameters
Solution Approach 1:
The patent simplifies the control system by replacing complex electrical parameter-based control (requiring inductance measurements and phase difference calculations) with a simpler mechanical resonance frequency detection and control method. The control unit detects resonance through position or current signals and directly controls the motor frequency to match this resonance frequency, eliminating the need for complex inductance-based phase difference control algorithms.
3Measurement precision
If resonance frequency detection is implemented, then the control precision is improved, but the device complexity increases due to additional detection and control mechanisms
Solution Approach 1:
The patent implements self-service by utilizing the existing position detection unit or current detection unit already present in the linear motor system to detect the resonance frequency. No separate or additional detection devices are required. The control unit processes the existing detection signals to identify resonance conditions and adjusts the drive frequency accordingly, achieving enhanced control precision while avoiding additional hardware complexity.
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 enables accurate control of the linear motor system's frequency, improving efficiency and precision by accounting for changes in load and position, thereby enhancing the motor's performance and energy utilization.
Implementation Method 1
a linear motor including an armature (9) having magnetic poles (7) and winding wires (8) and a mover (6) having a permanent magnet (2)
Implementation Method 2
the mover (6) or the armature (9) is connected to an elastic body (23)
Data Source
AI summary
Controllability of a linear motor or a compressor is improved in a linear motor system that includes: an armature having magnetic poles and winding wires; a mover having a permanent magnet; and a power conversion unit that outputs AC power to the winding wires, in which the mover and the armature are relatively movable, and the mover or the armature is connected to an elastic body. The linear motor system further includes: a position detection unit that detects and outputs the position of the mover with respect to the armature, a position estimation, or a current detection unit that outputs the value of current flowing through the winding wires; and a control unit that controls the output of the power conversion unit on the basis of the output of the position detection unit, the output of the position estimation unit, or the output of the current detection unit.