Position Detection Accuracy with Rectangular Wave Sampling
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Solution Overview
Problem
Existing position detection systems using a single coil have limited accuracy over a wide range due to the influence of external metal cases and resistor settings, leading to errors in inductance measurement.
Innovation Solution
A position detection device employing a signal processor that generates a rectangular wave voltage applied to a coil, samples the voltage after a predetermined time Td, and restricts the voltage measurement value within 40% to 99.999% of the maximum voltage, using low and band pass filters to extract direct and alternating current components for accurate position information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single coil position sensor is used, then the device complexity and cost are reduced, but the measurement precision deteriorates due to external metal case interference and limited detection accuracy range
Solution Approach 1:
The patent changes the measurement parameter from direct inductance measurement to measuring the voltage at a specific time point Td after applying a rectangular wave voltage. This parameter transformation allows the system to avoid the influence of external metal cases and achieve high-accuracy position detection with a simple single-coil structure. The specific parameter Td is determined based on the relationship between the coil inductance and the voltage rise time, enabling accurate measurement across a wide position range.
2Measurement precision
If the LVDT is used to achieve high detection accuracy, then the measurement precision is improved, but the device complexity and component cost increase due to requiring multiple coils
Solution Approach 1:
The patent extracts and eliminates the unnecessary multiple coils from the LVDT structure, retaining only a single coil while achieving comparable or superior measurement precision. By removing the complex multi-coil configuration and replacing it with a single coil配合 rectangular wave voltage measurement method, the system maintains high accuracy while significantly reducing device complexity and component costs.
Solution Approach 2:
The patent replaces the traditional multi-coil electromagnetic measurement system (LVDT) with a simplified single-coil system using rectangular wave voltage excitation and time-domain sampling. This substitution transforms the measurement approach from continuous analog measurement to pulsed digital-style sampling, reducing mechanical and structural complexity while maintaining measurement precision.
3Ease of manufacture
If a simple single coil sensor is used, then the manufacturing cost is reduced, but the measurement precision deteriorates in wide range applications
Solution Approach 1:
The patent transforms the measurement parameter from direct inductance value to the voltage value at a specific time point Td after rectangular wave excitation. This parameter change enables the simple single-coil sensor to achieve wide-range high-accuracy detection, as the time-domain measurement method inherently compensates for the limited sensitivity of single-coil structures across different positions.
4Loss of time
If traditional inductance measurement methods are used, then the measurement time is reduced by using small time intervals, but the measurement precision deteriorates due to external interference and resistor setting influences
Solution Approach 1:
The patent applies a rectangular wave voltage with a predetermined time delay Td before measurement, allowing the transient response to settle and external interference to diminish. This preliminary action of waiting for the specific time Td ensures that the measurement is taken when the signal is most stable and least affected by external factors, achieving both speed and accuracy.
Solution Approach 2:
The patent uses the relationship between the coil inductance and the voltage rise time to determine the optimal measurement time Td. This feedback mechanism ensures that the measurement is always taken at the most appropriate moment regardless of the actual inductance value, maintaining high precision across different positions while minimizing measurement time.
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 enables high-accuracy position detection over a wide range with a simple single-coil configuration, reducing errors and component costs, and maintaining performance under varying environmental conditions.
Implementation Method 1
when a relative positional relationship between the coil and the magnetic core changes, inductance of the coil changes
Data Source
AI summary
A position detection device includes a position sensor including a coil and a magnetic core, and a signal processor. The signal processor generates a rectangular wave voltage applied to the coil, converts a current which flow through the coil by the rectangular wave voltage into a voltage and outputs the voltage, and acquires a voltage measurement value obtained by sampling the output voltage after predetermined time in synchronization with a timing of rising or falling of a waveform of the rectangular wave voltage. The predetermined time is set such that the voltage measurement value is restricted within a range of 40% or more and 99.999% or less with respect to a maximum value of the rectangular wave voltage when the coil is at a position where an inductance of the coil is minimum.