Rotating Shaft Position Sensing with Half-Cycle Marker Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing position sensing systems face challenges in accurately measuring the angular position of high-speed rotating shafts due to constraints in measurement timing, sampling frequency, processing delay, and noise, which affect reliability and accuracy.
Innovation Solution
A position sensing system that includes analog conditioning circuitry, an analog-to-digital converter, and a controller to process variable magnitude and period input signals, dynamically attenuate and filter signals, and compare ramp times to detect markers such as short teeth on a rotating object, minimizing phase shift and data processing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional position sensing systems are used for high-speed rotating shafts, then measurement timing and sampling frequency constraints are imposed, but measurement accuracy and reliability deteriorate
Solution Approach 1:
The patent replaces traditional mechanical/optical encoder systems with a magnetic field-based sensing system using Hall effect sensors. This substitution eliminates mechanical contact and complex optical paths, enabling accurate position measurement at high rotational speeds without sampling frequency constraints. The magnetic field detection method provides continuous analog signals that can be processed without discrete sampling, directly resolving the timing-accuracy contradiction.
Solution Approach 2:
The patent changes the fundamental measurement parameter from optical/mechanical displacement to magnetic field strength variation. By measuring changes in magnetic field strength as teeth pass the sensor rather than using optical encoders, the system achieves high-speed measurement capability. The magnetic field parameters (strength, direction) change with tooth position, providing continuous measurement data without sampling limitations.
2Measurement precision
If high sampling frequency is used to improve measurement accuracy, then data quantity increases and processing resources are consumed
Solution Approach 1:
The patent extracts only the essential position information from the magnetic field signals by detecting zero-crossing points and transition edges. Instead of processing entire high-frequency signal waveforms, the system identifies key feature points (tooth leading edges, trailing edges, gaps) and uses these extracted features for position calculation. This extraction approach maintains measurement accuracy while dramatically reducing data processing requirements.
Solution Approach 2:
The patent uses partial action by measuring magnetic field strength at specific critical points during tooth passage rather than continuously sampling the entire rotation cycle. The system focuses measurement effort on the portions of the cycle that provide position information (tooth edges and gaps), ignoring redundant data during stable periods, thereby reducing processing load while maintaining accuracy.
3Loss of time
If processing delay is reduced to improve real-time performance, then noise in measurement increases
Solution Approach 1:
The patent performs preliminary filtering and signal conditioning on the magnetic field signals before position calculation. The system pre-processes the raw magnetic field data by applying low-pass filters and noise reduction algorithms in advance, so that when position measurements are calculated, the data is already cleaned and ready for immediate use. This preliminary action reduces processing delay for actual position computation while maintaining signal quality.
Solution Approach 2:
The patent introduces intermediary signal processing stages between the Hall effect sensors and the position calculation unit. These intermediaries include analog conditioning circuits, digital filters, and signal validation logic that clean and prepare the raw magnetic field data. The intermediaries act as buffers that reduce noise without adding significant delay to the critical position measurement path.
4Measurement precision
If traditional encoders with discontinuous patterns are used, then position detection can be achieved, but reliability is compromised due to missing or short teeth
Solution Approach 1:
The patent implements feedback mechanisms that continuously monitor the magnetic field signal quality and detect anomalies such as missing teeth or short teeth. When a tooth is detected to be missing or abnormal, the system uses feedback from subsequent teeth and the known gear geometry to calculate and compensate for the position error. This feedback-based compensation maintains detection reliability even when individual teeth are defective.
Solution Approach 2:
The patent prepares compensation algorithms and lookup tables in advance that account for potential tooth defects. The system pre-calculates expected magnetic field patterns for normal teeth and stores correction factors for various defect types. When a defect is detected, the pre-prepared compensation data is immediately applied, cushioning against the reliability impact before it can affect position accuracy.
Data Source
Figure 1
Figure 2~5
Figure 3
AI summary
A position sensing system for a rotating object may include analog conditioning circuitry, analog to digital converter circuitry, and a controller. The analog conditioning circuitry may identify a half cycle of an analog input signal received from a sensor, which has a variable period and a variable magnitude. The analog to digital converter circuitry may process the input signal during the variable period. The controller may control the analog to digital converter circuitry to compare a magnitude of the identified half cycle of a first variable period of the input signal to a magnitude of the identified half cycle of a second variable period of the input signal. The controller may generate an output signal when a difference between the magnitude of the identified half cycle of the first variable period and the magnitude of the identified half cycle of the second variable period is greater than a predetermined threshold.