High-Resolution Encoder Counting for Smooth Low-Speed Motor Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Direct-drive permanent magnet motors face challenges in achieving smooth operation at slow speeds due to low-resolution encoders, leading to torque vibrations and insufficient position and velocity feedback, especially in applications like elevators where precise control is necessary.
Innovation Solution
A motor drive system that incorporates a speed regulator module and a high-resolution counter to enhance position feedback resolution by incrementing a high-resolution counter during each second periodic interval, even if only one count is detected within the first periodic interval, thereby improving control during slow speed operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a low-resolution encoder is used in direct-drive permanent magnet motors, then device complexity is reduced and cost is lowered, but measurement precision of position and velocity feedback deteriorates, causing torque vibrations and insufficient control at slow speeds
Solution Approach 1:
The patent introduces an intermediary processing layer between the low-resolution encoder and the control system. A high-resolution counter accumulates encoder pulses over multiple intervals, and a resolution enhancement algorithm interpolates additional position and velocity information. This intermediary mechanism effectively transforms low-resolution encoder output into high-resolution feedback signals without requiring a physically higher-resolution encoder, thus resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
The patent transitions from spatial resolution (encoder pulses per revolution) to temporal resolution by measuring the time intervals between encoder pulses. By incorporating time-based measurements and calculating velocity as the derivative of position over time, the system achieves high-resolution velocity feedback even with low spatial resolution encoders. This dimensional shift from space to time allows accurate slow-speed control without increasing encoder complexity.
2Measurement precision
If the encoder resolution is increased to improve position feedback accuracy, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary processing layer between the low-resolution encoder and the control system. A high-resolution counter accumulates encoder pulses over multiple intervals, and a resolution enhancement algorithm interpolates additional position and velocity information. This intermediary mechanism effectively transforms low-resolution encoder output into high-resolution feedback signals without requiring a physically higher-resolution encoder, thus resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
The patent changes the processing parameters of the encoder signal rather than changing the physical encoder itself. By implementing software-based interpolation algorithms and adjusting the counting interval parameters, the system achieves higher effective resolution from the same physical encoder. This parameter-based approach allows dynamic adjustment of resolution without hardware changes, maintaining simplicity while improving measurement precision.
3Device complexity
If traditional counting methods are used at slow speeds, then device complexity remains low, but measurement precision of velocity feedback deteriorates due to insufficient counts per interval
Solution Approach 1:
The patent implements preliminary accumulation of encoder pulses over extended time intervals before performing velocity calculations. By pre-accumulating counts across multiple traditional intervals and using high-resolution timing to measure the total duration, the system ensures sufficient data accumulation even at very slow speeds. This preliminary action guarantees adequate measurement precision for velocity feedback without requiring complex real-time processing during speed regulation.
Solution Approach 2:
The patent transitions from spatial resolution (encoder pulses per revolution) to temporal resolution by measuring the time intervals between encoder pulses. By incorporating time-based measurements and calculating velocity as the derivative of position over time, the system achieves high-resolution velocity feedback even with low spatial resolution encoders. This dimensional shift from space to time allows accurate slow-speed control without increasing encoder complexity.
Data Source
AI summary
A motor drive receives a position feedback signal from an encoder operatively connected to the motor. The motor drive executes a speed regulator module on a first periodic interval to achieve desired operation of the motor, and the motor drive executes an additional module at a second periodic interval, occurring more frequently than the first periodic interval, to increase the resolution of the position feedback. The position feedback signal is provided as or converted to counts. The motor drive maintains a first counter with a running total of each count received as well as a second counter which generates a higher resolution value than the first counter. During each second periodic interval the motor drive increments the high-resolution counter by the number of actual counts detected within the corresponding first periodic interval. This high-resolution counter is used by the speed regulator to obtain desired operation of the motor.