Stepper Motor Closed Loop Control via Secondary Axis Correction
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Solution Overview
Problem
Existing closed loop stepper motor control systems face inefficiencies due to increased cycle times, lag in position error correction, and inability to correct errors when the axis is stationary or used as a slave, particularly in non-linear movements.
Innovation Solution
A dual-axis control system where a primary axis uses open loop stepper motor control and a secondary monitoring axis calculates and applies position corrections independently, updating velocity profiles to correct for position errors in a continuous manner, allowing for closed loop control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If error correction move is performed after a move is completed, then position error is corrected, but cycle time increases
Solution Approach 1:
The system performs preliminary action by continuously monitoring position errors during the move execution and preparing correction moves in advance. The control system calculates correction moves based on predicted position errors before the actual move completes, allowing corrections to be applied without waiting for move completion, thus reducing cycle time while maintaining position accuracy.
Solution Approach 2:
The system implements continuity of useful action by continuously monitoring position errors throughout the move execution and continuously applying corrections in real-time. This eliminates the间断 (interruption) of waiting for move completion before correction, allowing the correction process to overlap with move execution, thereby reducing overall cycle time while maintaining continuous position control.
2Measurement precision
If correction is performed after a move is completed, then position error is corrected, but lag time in correction occurs
Solution Approach 1:
The control system performs preliminary calculation of correction moves based on predicted position errors during move execution. By anticipating position errors before the move completes and preparing corrections in advance, the system eliminates the lag time associated with waiting for move completion before initiating corrections.
Solution Approach 2:
The system implements continuous feedback by monitoring position errors in real-time during move execution and immediately applying corrections based on the detected errors. This real-time feedback loop eliminates the delay inherent in post-move correction, as corrections are applied continuously throughout the move rather than waiting until completion.
3Productivity
If conventional open loop control is used, then cycle time is efficient, but position information is inaccurate
Solution Approach 1:
The system introduces feedback by continuously monitoring the actual position of the stepper motor using an encoder and comparing it with the commanded position. This feedback mechanism provides accurate position information without disrupting the efficient open-loop control cycle, as corrections are calculated and applied based on the feedback data while maintaining the original open-loop execution efficiency.
Solution Approach 2:
The control system segments the control function into two independent parts: the primary open-loop controller that maintains efficient cycle timing, and a secondary correction system that processes position feedback and generates corrections. This segmentation allows the system to maintain open-loop efficiency while incorporating closed-loop position accuracy through independent correction moves.
Data Source
AI summary
System and method for controlling a stepper motor. A current position of the stepper motor may be received. A position error of the stepper motor may be determined using the current position of the stepper motor. A velocity profile may be maintained based on the position error, such that it tracks the position error. A position correction value may be determined based on the velocity profile, e.g., by integrating a portion of the velocity profile. A new position value may be generated to drive the stepper motor. An output position value to the stepper motor may be provided to drive the stepper motor. The output position value may incorporate the new position value and the position correction value and may be operable to reduce position error of the stepper motor.