Encoder Input Synchronization for High-Speed Motor Position Feedback
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Solution Overview
Problem
Existing motor drive systems face limitations in accurately correlating high-speed feedback signals with motor position due to finite sampling intervals, leading to decreased resolution and synchronization challenges, especially in industrial processes with repeated motions.
Innovation Solution
A system and method involving a substrate-mounted control circuit that samples position feedback signals at a higher frequency than the motor drive, correlating input signals with motor position or time, and transmitting synchronized data packets to external controllers via an industrial network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the motor drive samples the position feedback signal at a finite interval to execute control routines, then the control system can generate switching signals for power electronic devices, but the resolution at which the position may be determined is decreased as speeds increase
Solution Approach 1:
The encoder samples the position feedback signal at a higher frequency than the motor drive's control routine, performing the sampling action in advance. This preliminary high-frequency sampling creates a reservoir of position data that can be correlated with input signals occurring at any time, thereby maintaining high position resolution even at high motor speeds without requiring the control routine to run faster
Solution Approach 2:
The encoder acts as an intermediary device between the motor drive and the position feedback signal. It receives the high-frequency position feedback signal and provides sampled position data to both the motor drive for control purposes and to external controllers for correlation with input signals, thereby resolving the contradiction by decoupling the sampling frequency from the control routine frequency
2Loss of information
If the motor drive correlates input signals with sampled position data, then position information can be associated with feedback signals, but synchronization accuracy is limited by the finite sampling interval
Solution Approach 1:
The encoder changes the sampling parameter (frequency) to be higher than the motor drive's control routine frequency. This parameter change allows position data to be captured at intervals fine enough to maintain synchronization accuracy even when input signals occur between the motor drive's control sampling moments, thereby reducing both information loss and effective time loss
3Measurement precision
If the sampling rate is increased to maintain position resolution at high speeds, then the difference in angular positions between samples decreases, but the complexity of the control system increases
Solution Approach 1:
The system segments the sampling function from the control routine function. The encoder performs high-frequency position sampling independently, while the motor drive executes control routines at its own frequency. This segmentation allows each component to operate at its optimal frequency without requiring the entire control system to run at high speed, thereby maintaining position resolution without proportionally increasing overall system complexity
Data Source
AI summary
A system for correlating an input signal with an operating state of a motor includes a substrate which is either integral to an encoder or mounted on the motor. The substrate has a first input connected to a sensor proximate to the motor to receive a first signal from the sensor. The substrate also includes a second input to receive a position feedback signal from the encoder. A control circuit is operative to detect a change in state of the first signal and to correlate at least one additional signal to the change in state of the first signal. A data packet including the first signal and the at least one additional signal correlated at the change in state is generated. A communication interface is operative to transmit the data packet from the control circuit to at least one additional controller external from the motor.