Position Encoder Phase Offset Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing processing techniques for position sensors, such as inductive and capacitive encoders, are sensitive to noise introduced by the processing electronics, which affects the accuracy of position information determination.
Innovation Solution
The development of an apparatus with a signal generator and controller that switches between two modes to generate cyclically varying sensor signals, allowing for phase difference measurement to determine position, while minimizing noise sensitivity through phase offset cancellation and synchronized zero crossings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing processing techniques are used to process detector signals, then position information can be determined, but the system is sensitive to noise introduced by processing electronics which reduces measurement precision
Solution Approach 1:
The system uses periodic switching between two different processing modes (first mode and second mode) to process detector signals. By alternately applying different transfer functions and then differencing the results, the method periodically cancels out noise components while preserving the position information, thereby improving measurement precision without being sensitive to continuous noise from processing electronics
Solution Approach 2:
The system changes processing parameters by switching between two different transfer functions (first transfer function and second transfer function) with different phase characteristics. This parameter switching allows the system to process the same detector signal through different mathematical transformations, and by differencing the results, eliminates common noise components while extracting accurate position information
2Productivity
If phase measurements are taken during single mode operation, then position can be determined, but update rates are limited and noise sensitivity remains
Solution Approach 1:
The system performs periodic switching between first mode and second mode processing, with each mode contributing to the final position calculation. This periodic alternation allows the system to effectively double the measurement throughput compared to single-mode operation, as both modes are utilized within each measurement cycle, thereby increasing update rate while maintaining precision through noise cancellation
Solution Approach 2:
The system maintains continuous position measurement capability by ensuring that both first mode and second mode processing occur in rapid succession without interruption. The continuous alternation between modes allows the system to continuously generate position information at higher update rates, eliminating idle time between measurements while the differencing operation continuously cancels noise
3Reliability
If the signal generator operates in a single mode, then the system is simpler to control, but it cannot cancel phase offsets and achieve faster update rates
Solution Approach 1:
The controller implements periodic switching between two distinct operating modes, each with different transfer functions. This controlled periodic alternation, while adding complexity to the control logic, enables the system to cancel phase offsets by differencing measurements from both modes, thereby significantly improving the reliability of position information through noise and offset elimination
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 accuracy and noise resilience of position sensing by canceling phase offsets and allowing for faster update rates of phase measurements, improving the reliability of position information determination.
Implementation Method 1
inductive or capacitive based position encoders... The stationary member typically includes a number of detectors which provide electrical output signals
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A position encoder is described that generates a signal whose phase varies with a position to be determined. A phase detector determines a first phase measurement of the sensor signal during a first mode and a second phase measurement of said sensor signal during a second mode. The phase detector then differences the first and second phase measurements to obtain a phase difference measurement, which it uses to determine an indication of the position to be sensed. A controller controls a signal generator in order to set a start phase of signals generated in at least one of the first and second modes so that the timings at which said sensor signal crosses a reference level are substantially the same.