Self-Calibrating LVDT Demodulator Phase Shift Compensation
Solution Overview
Problem
Existing linear voltage differential transformer position sensors face challenges in accurately determining peak-to-peak values due to phase shifts caused by environmental factors and aging, which complicates the measurement of shaft position without requiring high-frequency sampling.
Innovation Solution
A self-calibrating demodulator system that includes an excitation module, a measurement module, a calculation module, and a calibration module, which introduces an excitation signal, measures induced signals at specific phases, compares values to adjust phases incrementally to detect peak values, and calculates peak-to-peak values without high-bandwidth sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RMS or average value measurement is used to determine secondary voltages, then shaft position can be calculated, but multiple samples during the excitation period are required which increases measurement complexity
Solution Approach 1:
The patent applies preliminary action by pre-determining the optimal sampling phase angle through calibration. The system performs an initial calibration process that identifies the specific phase angle where sampling yields the most accurate peak-to-peak voltage measurement. This pre-established phase information is then used during normal operation to guide single-sample measurements, eliminating the need for multiple samples during each excitation period while maintaining measurement accuracy.
2Productivity
If peak-to-peak measurement technique is used to measure secondary voltages, then fewer samples are required, but determining the peaks becomes difficult due to phase shift variations from temperature, aging, and wiring
Solution Approach 1:
The patent implements feedback through an iterative calibration process. The system initially guesses a sampling phase angle, performs measurements, and then uses the measured data to refine and adjust the phase angle estimate. This feedback loop continues, progressively improving the accuracy of the phase angle determination until convergence is achieved. The calibrated phase angle is then used for accurate peak-to-peak measurements during normal operation, resolving the difficulty of peak detection under varying environmental conditions.
3Measurement precision
If high-frequency sampling is used to accurately capture secondary voltages, then measurement accuracy improves, but computational requirements and processing complexity increase
Solution Approach 1:
The patent applies preliminary action by performing phase calibration during an initialization or idle period before normal measurement begins. This pre-computed phase information captures the system's characteristics under current environmental conditions. During subsequent normal operation, the system uses this pre-determined phase angle to perform accurate measurements with minimal sampling, avoiding the need for continuous high-frequency sampling and complex real-time computations while maintaining measurement accuracy.
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 allows for accurate determination of shaft position with reduced computational requirements and increased accuracy by tracking peak values efficiently, overcoming phase shift issues caused by environmental factors.
Implementation Method 1
An excitation signal is applied to the primary winding, and the excitation signal is coupled to the secondary windings. The resulting voltages across the secondary windings can be used to calculate shaft position.
Data Source
AI summary
A calibration system includes an excitation module that introduces an excitation signal to a primary coil of a differential transformer, a measurement module that measures, at a first phase shift, a positive value of an induced signal. The induced signal is caused by the excitation signal on a secondary coil of the differential transformer. The system further includes a calculation module that compares the positive value to a last positive value to form a compared positive value, and a calibration module that changes the first phase shift based on the compared positive value.