PCB Reluctance Sensor for Accurate Rotor Position Detection
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Solution Overview
Problem
Existing rotor position sensing systems in electric machines face challenges in accurately detecting the position and speed of rotating elements, particularly when the system is stationary or under varying magnetic conditions, leading to inefficiencies and increased complexity in control systems.
Innovation Solution
A rotor position sensing system utilizing a printed circuit board with a sensing coil that detects fluctuations in magnetic fields or reluctance caused by rotating teeth, employing a magnetic equivalent circuit and driving/filtering circuits to extract signals for precise position and speed determination, allowing for improved control of electric machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional rotor position sensing systems are used, then the system can detect rotor position, but the accuracy is insufficient particularly when the system is stationary or under varying magnetic conditions
Solution Approach 1:
The patent employs multiple sensing coils arranged at different positions around the rotor, each detecting magnetic field parameters from different spatial perspectives. By combining measurements from multiple coils with different orientations and positions, the system achieves accurate rotor position detection even when individual coil signals are weak or distorted under stationary or varying magnetic conditions
Solution Approach 2:
The patent introduces a magnetic equivalent circuit model as an intermediary to interpret the complex magnetic field interactions between the rotor and stator. This model transforms difficult-to-interpret raw magnetic field data into reliable position information by accounting for magnetic saturation, leakage, and other non-ideal effects that vary with operating conditions
2Measurement precision
If complex control systems are implemented to improve detection accuracy, then position detection accuracy improves, but system complexity increases
Solution Approach 1:
The sensing coil assembly is designed to simultaneously perform multiple functions: detecting rotor position, determining rotor speed, and providing information for commutation control. By integrating these functions into a single sensor system rather than using separate sensors for each function, the patent achieves high detection accuracy without proportionally increasing system complexity
Solution Approach 2:
The magnetic field sensing system utilizes the existing magnetic field generated by the motor's own operation rather than requiring external excitation sources or additional sensors. The rotor's movement through the stator's magnetic field naturally induces signals in the sensing coils, allowing the system to self-diagnose position and speed without external intervention
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
Enhances the accuracy and efficiency of rotor position detection, enabling better control of electric machines by providing reliable feedback for sequencing and speed control, even under varying conditions, and reduces commutation losses and voltage drop.
Implementation Method 1
A rotor position sensing system may include a controller and a reluctance sensor... the reluctance sensor may include a magnetic core and a sensing coil wound around the magnetic core... detects fluctuations in magnetic fields or reluctance caused by rotating teeth
Implementation Method 2
the reluctance sensor may include a magnetic core and a sensing coil wound around the magnetic core... employed a magnetic equivalent circuit... to extract signals for precise position and speed determination
Data Source
AI summary
An electric machine includes at least a printed circuit board and a magnetically permeable element. The printed circuit board includes a reluctance coil configured to generate a voltage in presence of a magnetic flux. The magnetically permeable element has a first end positioned adjacent to a rotor of the electrical machine and a second end positioned adjacent to the coil of the printed circuit board. In some examples, rotation of the rotor causes a change in the magnetic flux through the magnetically permeable element and generation of the voltage across the reluctance coil.