Inductive Position Sensor Offset Voltage Reduction
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Solution Overview
Problem
Conventional inductive position sensors suffer from measurement errors due to parasitic pulses caused by amplifiers and switches, leading to inaccuracies in calculating the angular position of moving parts, particularly in high-speed applications like industrial automation.
Innovation Solution
The proposed solution involves reconfiguring the signal processing architecture by placing amplifiers after the output terminals of the sensor, incorporating RC filters and parallel multiplexers to eliminate parasitic pulses, and using low-pass filters to remove high-frequency components, thereby reducing offset voltage errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amplifiers and switches are placed before the output terminals of the sensor, then signal amplification and demodulation can be performed, but parasitic pulses are injected into the measurement circuit causing measurement errors
Solution Approach 1:
The patent extracts the harmful function of the amplifiers and switches by moving them from the measurement signal path to a separate demodulation path. The amplifiers are reconfigured to amplify only the demodulated baseband signals rather than the high-frequency measurement signals, thereby extracting the amplification function from the measurement path and eliminating the parasitic pulse injection into the measurement circuit.
Solution Approach 2:
The patent introduces demodulation circuits as intermediary elements between the sensor output and the amplifiers. These intermediary circuits convert the high-frequency measurement signals to baseband signals, allowing the amplifiers to operate on the demodulated signals without injecting parasitic pulses into the original measurement path. The intermediary demodulation stage acts as a buffer that separates the measurement and processing functions.
2Ease of operation
If multiplexers with switches are used for demodulation, then signal processing can be performed, but parasitic pulses are injected when multiplexer is connected to amplifier output
Solution Approach 1:
The patent segments the signal processing function into separate demodulation and amplification stages. The multiplexers are dedicated solely to the demodulation function, switching between different signal paths to extract sine and cosine components. The amplification function is separated into dedicated amplifier circuits that receive only the demodulated baseband signals. This segmentation prevents the multiplexers from injecting parasitic pulses into the amplification path.
Solution Approach 2:
The patent extracts the switching function from the measurement signal path and confines it to the demodulation path only. The multiplexers are reconfigured to switch only the demodulated baseband signals rather than the high-frequency measurement signals, thereby extracting the switching operation from the measurement path and eliminating the parasitic pulse injection into the measurement circuit.
3Power
If amplifiers amplify both measured value and errors, then signal strength is increased, but measurement errors are also amplified
Solution Approach 1:
The patent applies preliminary demodulation action before amplification. The demodulation circuits first convert the high-frequency measurement signals to baseband signals, separating the measurement information from the carrier frequency. Only after this preliminary demodulation action are the signals amplified. This preliminary action ensures that the amplifiers amplify only the baseband measurement signals without the high-frequency components that would carry measurement errors.
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 configuration significantly reduces measurement errors by eliminating parasitic pulses and deformations in the signal curves, resulting in more accurate position measurements with reduced offset voltage, enhancing the precision of position detection in industrial applications.
Implementation Method 1
This high-frequency alternating current induces a magnetic field at the same frequency as the current passing through it, in at least one secondary circuit
Implementation Method 2
The moving target cuts the passage of the magnetic flux, and therefore the voltage induced by the magnetic field in the loops varies depending on the position of the target
Data Source
AI summary
To eliminate measurement errors, such as “offset voltages” in sensors of the inductive type by modifying the architecture of the assembly of elements used for signal processing, the architecture of the apparatuses processing the signal from the secondary windings is modified as follows:the amplifiers of this sensor are placed between the low-pass filters and the output terminals of the sensor,the voltages from the two secondary windings pass into an RC filter including a resistor and a capacitor,the voltage from each of the secondary windings passes into two multiplexers, one of which allows only the positive half-cycle to pass through, the other being wired so as to allow only the negative half-cycle to pass through, and the unused outputs of these multiplexers are connected to the common point between the secondary windings,low-pass filters are placed between each of the multiplexers and the amplifiers.