Capacitive Rotary Angle Sensing With Adaptive Carrier Frequency
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Solution Overview
Problem
Capacitive rotary angle measuring systems in electric motors are prone to signal noise interference from PWM signals, affecting accuracy and reliability.
Innovation Solution
A capacitive rotary angle measuring system with a carrier signal adaptation unit that adjusts the carrier signal frequency to avoid interference frequencies, using an interference frequency detection unit to determine and adapt the carrier signal frequency based on detected interference signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed carrier signal frequency is used in the capacitive rotary angle measuring system, then the system structure is simple and operation is easy, but the system is susceptible to PWM signal interference affecting measurement accuracy
Solution Approach 1:
The patent implements a dynamic carrier signal frequency adaptation mechanism where the carrier signal frequency is no longer fixed but is continuously adjusted based on detected interference frequencies. The system includes a frequency detection unit that identifies PWM signal frequencies and a frequency adaptation unit that modifies the carrier signal frequency in real-time to avoid interference, transforming the static frequency parameter into a dynamic one that adapts to changing operational conditions.
Solution Approach 2:
The patent changes the parameter of carrier signal frequency from a constant value to a variable that is continuously adapted based on interference detection. The frequency adaptation unit modifies the carrier signal frequency parameter in response to detected PWM signal frequencies, ensuring that the measurement system operates at optimal frequencies that avoid interference while maintaining measurement accuracy.
2Reliability
If the carrier signal frequency is adapted dynamically to avoid interference, then measurement reliability is improved, but the device complexity increases due to additional detection and adaptation units
Solution Approach 1:
The patent integrates multiple functions into unified components to minimize system complexity. The frequency detection unit and frequency adaptation unit work as a coordinated system where the detection unit identifies interference and the adaptation unit simultaneously adjusts the carrier signal. This multi-functional approach allows the system to perform interference detection, frequency analysis, and adaptive adjustment through integrated components rather than separate dedicated units for each function.
Solution Approach 2:
The patent implements a feedback mechanism where the detected interference frequencies are fed back to the frequency adaptation unit, which then adjusts the carrier signal frequency accordingly. This closed-loop feedback system continuously monitors the electromagnetic environment and automatically adapts the carrier signal to avoid interference, improving reliability without requiring complex manual intervention or multiple independent control systems.
3Measurement precision
If a fixed carrier signal frequency is used, then the system is easy to operate and manufacture, but signal noise from PWM harmonics significantly affects measurement accuracy
Solution Approach 1:
The patent performs preliminary frequency detection and adaptation before actual rotary angle measurement begins. The frequency detection unit identifies PWM signal frequencies in advance, and the frequency adaptation unit pre-adjusts the carrier signal frequency to avoid interference. This preliminary action ensures that the measurement system is already optimized for the current electromagnetic environment before measurements start, eliminating the need for complex real-time adjustments during measurement operations.
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
Minimizes interference influence, ensuring accurate and reliable rotational angle measurements by adapting the carrier signal frequency to avoid harmonics and noise from PWM signals.
Implementation Method 1
a receiving electrode arrangement (20) which is capacitively coupled to the transmitting electrode arrangement (18)
Data Source
AI summary
A capacitive rotary angle measuring system for detecting a rotary movement of a shaft includes a sensor unit, a carrier signal generator, an evaluation unit, and a carrier signal adaptation unit. The sensor unit includes a transmitting electrode arrangement and a receiving electrode arrangement which are capacitively coupled together, and a coupling device which co-rotates with the shaft and which varies an electric capacity between the receiving and the transmitting electrode arrangement based on a rotational position of the coupling device. The carrier signal generator is electrically connected to the transmitting electrode arrangement and generates an electrical carrier signal. The evaluation unit is electrically connected to the receiving electrode arrangement and senses an electric measurement signal generated at the receiving electrode arrangement and determines a current rotary angle measurement value. The carrier signal adaptation unit adapts a carrier signal frequency value based on a provided interference frequency value.