Rotary Sensor Capacitance Detection for Absolute Angle
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Solution Overview
Problem
Existing rotary sensors struggle to accurately detect the absolute angle of a rotor with respect to a stator due to ambiguity in output signals from detection coils, which are caused by multiple cycles of magnetic field changes during one rotation of the rotor.
Innovation Solution
A rotary sensor configuration that includes a conductive rotor with conductive parts and a different-thickness part, along with a stator featuring an excitation coil, a detection coil, and a detection electrode part. The detection electrode part overlaps part of the rotation trajectory of the different-thickness part, allowing for the detection of capacitance changes which correspond to specific rotational positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetic field shielding parts and non-shielding parts are alternately arranged in the rotor to increase measurement cycles, then the resolution of angle detection is improved, but the ability to determine absolute angle position deteriorates due to signal ambiguity
Solution Approach 1:
A detection electrode part is introduced as an intermediary element between the rotor and stator. This electrode part forms a capacitance with the rotor that varies with rotational position. The capacitance value serves as an additional signal that provides absolute position information, complementing the magnetic field detection signals and resolving the ambiguity problem.
Solution Approach 2:
The invention utilizes capacitance as an additional detection parameter alongside magnetic field changes. By measuring both magnetic field variations (from multiple conductive parts) and capacitance variations (from the detection electrode part), the system obtains multiple independent parameters that together provide both high-resolution incremental measurement and absolute position determination.
2Measurement precision
If a detection electrode part is added to detect capacitance for determining absolute position, then the ability to detect absolute angle is improved, but the device complexity increases
Solution Approach 1:
The detection electrode part serves multiple functions: it forms a capacitance for detecting absolute angular position, and its presence also influences the magnetic field distribution. This multi-functional element adds minimal structural complexity while providing the needed absolute position information.
Solution Approach 2:
The detection electrode part is integrated into the stator structure, combining the capacitance detection function with the existing magnetic field detection system. The electrode part is disposed on the counter surface of the substrate, merging multiple detection capabilities into a unified stator assembly rather than adding separate independent components.
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 easy detection of the absolute angle of the rotor with respect to the stator by utilizing capacitance changes, improving rotation stability, and enhancing the accuracy of angle detection.
Implementation Method 1
the excitation coil generates a magnetic field, and in this state, a change in the magnetic field due to an eddy current along with rotation of the sensor rotor is detected by the detection coil
Implementation Method 2
a change in the magnetic field due to an eddy current along with rotation of the sensor rotor is detected by the detection coil
Implementation Method 3
the detection electrode part is configured to detect capacitance generated between the capacitance and the rotor
Data Source
AI summary
A plurality of conductive parts are aligned along a rotational direction of a rotor. A different-thickness part relatively differs in thickness in one direction. In the rotor, a plurality of gaps are provided to separate the plurality of conductive parts from each other. An excitation coil is annularly arranged on a counter surface of a substrate. A detection coil is disposed inside the excitation coil on the counter surface of the substrate. A detection electrode part is disposed on the counter surface of the substrate such that the detection electrode part overlaps part of a rotation trajectory of the different-thickness part at a time of rotation of the rotor in plan view in the one direction, and the detection electrode part is configured to detect capacitance generated between the detection electrode part and the rotor.