Dual-Encoder Motor Control for Position and Velocity
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Solution Overview
Problem
High-resolution encoders used for precise positioning in motor control systems are incompatible with high-speed velocity control due to serial communication delays, which hinder simultaneous achievement of precise position and velocity control.
Innovation Solution
Implementing a dual-encoder system with a high-resolution encoder for position control and a low-resolution encoder for velocity control, where the velocity control cycle is faster than the position control cycle, allowing for efficient serial data communication without compromising position control precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution encoder is used for precise position control, then position control precision is improved, but velocity control cannot be performed due to serial communication time delays
Solution Approach 1:
The encoder system is segmented into two distinct encoders: a high-resolution encoder dedicated to position control and a low-resolution encoder dedicated to velocity control. This segmentation allows each encoder to be optimized for its specific function, resolving the contradiction between position precision and velocity control speed by eliminating the communication bottleneck for velocity measurements
Solution Approach 2:
The low-resolution encoder acts as an intermediary for velocity control, providing a simplified measurement path that does not require high-speed serial communication. This intermediary encoder enables velocity control to proceed independently at high speed without being constrained by the communication limitations of the high-resolution position encoder
2Measurement precision
If serial communication is used for high-resolution encoder data transmission, then position detection accuracy is improved, but control cycle time increases
Solution Approach 1:
The control system is segmented into position control and velocity control loops with different timing requirements. The high-resolution encoder data is processed at a slower position control cycle, while velocity control operates at a faster cycle using separate encoder data, thereby reducing overall control cycle time loss
Solution Approach 2:
The system uses partial action by employing only the necessary resolution for each control function. The low-resolution encoder provides sufficient data for velocity control without the overhead of high-resolution serial communication, reducing time loss while maintaining adequate measurement precision for each specific control purpose
Data Source
AI summary
A motor control apparatus includes a high-resolution encoder for position control and a low-resolution encoder for velocity control, position control means for generating a velocity command in accordance with a difference between a given position command and the output of the high-resolution encoder, and velocity control means for generating a current command in accordance with a difference between the velocity command and a detected velocity that is based upon the output of the low-resolution encoder. A velocity control cycle based upon the velocity control means is made faster than a position control cycle based upon the position control means.