Rotation Angle Sensor Frequency Multiplexing
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Solution Overview
Problem
Rotation angle sensors face measurement errors due to external interference and installation tolerances, such as tilting, which can cause interfering signals to overlap with the operating frequency, impairing accuracy.
Innovation Solution
The sensor employs a stator element with at least two transmission coils emitting electromagnetic alternating fields at different frequencies, and a measurement device that demodulates the induced AC voltages to distinguish between the desired and interfering signals, using resonant oscillating circuits and a demodulator to separate signal paths and reduce susceptibility to interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single frequency is used for the electromagnetic alternating field, then the device complexity is reduced, but the measurement precision deteriorates due to interference from external signals at similar frequencies
Solution Approach 1:
The patent applies dynamics by making the operating frequency variable rather than fixed. The measurement device is designed to excite the transmission coil at multiple different frequencies, allowing the system to dynamically switch between frequencies to avoid interference and maintain measurement precision.
Solution Approach 2:
The patent changes the frequency parameter of the electromagnetic alternating field. By exciting the transmission coil at different frequencies and demodulating the received signals accordingly, the system can distinguish between desired signals and external interference, thereby improving measurement precision.
2Reliability
If multiple frequencies are used for the electromagnetic alternating field, then the robustness against interference is improved, but the device complexity increases due to additional transmission coils and signal processing
Solution Approach 1:
The patent applies multi-functionality by enabling a single transmission coil to operate at multiple different frequencies. This allows the system to achieve robustness against interference at various frequencies without requiring multiple separate transmission coils, thus improving reliability while limiting the increase in device complexity.
3Measurement precision
If multiple reception coils are used, then the ability to distinguish signals from different frequencies is improved, but the device complexity and cost increase
Solution Approach 1:
The patent uses demodulation as an intermediary process to distinguish signals from different frequencies. Instead of requiring multiple reception coils physically separated for different frequencies, the demodulator acts as an intermediary that processes the combined signal and separates the frequency components, improving measurement precision without proportionally increasing device 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 enhances the robustness of the rotation angle sensor by effectively distinguishing between induced voltages from different frequencies, reducing the impact of external interference and improving measurement accuracy.
Implementation Method 1
By arranging transmission and reception coils on the stator of a rotation angle sensor, which coils are inductively coupled to a target on the rotor such that, when an electromagnetic alternating field is emitted by the transmission coil, at least two different AC voltages are induced in at least two reception coils
Implementation Method 2
The measurement device is designed to excite the at least one transmission coil at at least two different frequencies in order to emit at least two electromagnetic alternating fields
Data Source
AI summary
A rotary sensor includes a stator element and a rotor element that is rotatably mounted in respect of the stator element about an axis of rotation. A rotary angle can be captured by inductive coupling between the rotor element and the stator element. The rotary sensor further includes a measuring device configured to capture the rotary angle depending on the inductive coupling between the rotor element and the stator element. The stator element has at least one transmission coil for emitting alternating electromagnetic fields and at least two reception coils for capturing alternating electromagnetic fields, when the measuring device is configured to excite the at least one transmission coil with at least two mutually different frequencies for emitting at least two alternating electromagnetic fields.