Motor Shaft Motion Detection Using Adaptive Signal Processing
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Solution Overview
Problem
Existing sensor systems for detecting motor shaft motion, particularly those using Hall effect sensors and encoders, face challenges in accurately determining the direction and speed of rotation due to limited bandwidth and phase separation issues, leading to errors when phases are less than 90 electrical degrees apart.
Innovation Solution
A method involving a controller that samples first and second signals offset from each other, calculates rotational direction and displacement based on sample counts above or below a threshold, and assumes previous direction when samples are below the threshold, allowing for accurate motion determination even with limited sampling capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If quadrature phase signals are used to determine direction and speed of motor shaft rotation, then motion detection capability is improved, but measurement precision deteriorates when phases are less than 90 electrical degrees apart
Solution Approach 1:
The system dynamically adapts its processing method based on detected phase separation. When phase separation exceeds the threshold (90 electrical degrees), the system uses standard quadrature decoding. When phase separation falls below the threshold, the system automatically switches to an alternative processing mode that compares signal transitions differently, thereby maintaining measurement precision across varying phase conditions
Solution Approach 2:
The invention changes the processing parameter (decoding method) based on the phase separation parameter. By monitoring the phase separation between quadrature signals and comparing it to a threshold value, the system selects the appropriate processing approach, effectively handling both large and small phase separations without loss of accuracy
2Measurement precision
If high sampling rate is used to capture all phase changes for accurate direction determination, then measurement precision is improved, but device complexity increases due to limited microprocessor bandwidth
Solution Approach 1:
Instead of requiring the microprocessor to sample every single phase change event (excessive action), the system uses a lower sampling rate (partial action) combined with intelligent signal processing. The alternative decoding method processes fewer samples more effectively, reducing the burden on the microprocessor while maintaining accurate direction determination
Solution Approach 2:
The invention introduces an intermediary processing layer that sits between the raw quadrature signals and the final direction determination. This intermediary layer implements the alternative processing logic that can accurately determine direction from fewer samples, effectively mediating between limited sampling capability and the need for precise motion detection
3Device complexity
If standard quadrature processing is used with phases separated by less than 90 electrical degrees, then device complexity is kept simple, but measurement precision deteriorates leading to errors
Solution Approach 1:
The system dynamically selects the processing approach based on phase separation conditions. When phases are naturally well-separated (above threshold), simple processing suffices. When phases are closely spaced (below threshold), the system automatically activates the alternative processing method, ensuring accuracy is maintained without unnecessarily complicating the system for all operating conditions
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 method enables precise determination of motor shaft motion, including direction and speed, by effectively handling phase offsets as small as 5 electrical degrees, improving accuracy and reducing errors in systems with limited bandwidth.
Implementation Method 1
A Hall effect sensor is a solid state detection device that varies its output voltage in response to a magnetic field.
Data Source
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AI summary
Methods and systems of processing sensor signals to determine motion of a motor shaft are disclosed. This disclosure relates to the processing of sequences of pulses from a sensor for computing the motion of an electric motor output shaft. Furthermore, this disclosure relates to the processing of two sequences of pulses from sensor outputs, which may be separated by only a few electrical degrees, to compute the motion of an electrical motor output shaft while using a limited bandwidth controller. Motor shaft direction, displacement, speed, phase, and phase offset may be determined from processing the sensor signals.