Motor Encoder Interface for Noise-Robust Angle Counting
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Solution Overview
Problem
Accurate measurement of motor rotation angle and number of rotations is hindered by noise in transmission paths and rotor stoppage around the starting position, making it difficult to reliably detect position and speed information.
Innovation Solution
An encoder system with an interface that includes digital filters, AB and Z waveform recognition circuitry, starting point storage, and a rotation angle counter, which generates an interrupt signal to reset and restart the count based on a predefined AB-phase change pattern, synchronizing the count with the Z-phase signal changes to mitigate noise and rotor stoppage effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rotation angle and number of rotations are counted at the starting point indicated by the Z-phase signal, then the measurement can be synchronized with the encoder signal, but noise in transmission paths and rotor stoppage around the starting position causes inaccurate measurement
Solution Approach 1:
The system performs preliminary actions by detecting the AB-phase change pattern and storing it as a reference before the Z-phase signal indicates the starting point. This allows the system to have the measurement reference ready in advance, avoiding the problem of measuring at an unreliable starting point where noise and rotor stoppage occur.
Solution Approach 2:
The AB-phase change pattern serves as an intermediary reference between the Z-phase signal and the rotation angle measurement. Instead of directly using the Z-phase signal's starting point (which is unreliable), the system uses the AB-phase change pattern as an intermediate reference that can be detected more reliably and used to establish the measurement baseline.
2Ease of operation
If the starting point is determined by the Z-phase signal rise, then the counting can be synchronized with the encoder, but noise and rotor stoppage make it difficult to accurately detect the starting position
Solution Approach 1:
The system replaces the mechanical/physical detection method (relying on the Z-phase signal rise and rotor position) with an electronic signal processing method. By detecting the AB-phase change pattern through digital signal analysis and comparing it with a stored reference pattern, the system can identify the starting position more reliably without being affected by noise and rotor stoppage issues.
Solution Approach 2:
The system uses feedback by storing the AB-phase change pattern as a reference and continuously comparing incoming AB-phase signals against this reference. This feedback mechanism allows the system to confirm when the correct starting position has been reached by matching the pattern, rather than relying solely on the Z-phase signal which may be unreliable.
Data Source
AI summary
According to an embodiment, an encoder system includes an encoder and an interface. The encoder detects the position and speed of a motor, and generates A-, B- and Z-phase signals. The interface includes an AB waveform recognition circuitry to recognize a waveform of an AB phase, a Z waveform recognition circuitry to recognize a period of an enable state of a Z phase, a starting point storage device to store a value of the AB phase when the Z phase changes and stores an AB-phase change pattern, a starting point recognition circuitry to generate an interrupt signal, and a rotation angle counter to start a new count of the rotation angle of the motor.