Servo Controller Reducing Synchronous Error in Machining
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Solution Overview
Problem
Conventional servo controllers for machine tools face challenges in reducing synchronous error between shafts, particularly when the master shaft has low servo stiffness, leading to vibrations and instability due to machining disturbances and mechanical rigidity, with existing methods either amplifying vibrations or failing to suppress aperiodic synchronous errors.
Innovation Solution
A servo controller that includes position and speed feedback acquisition units, converters, error calculators, filtering processors, and correctors to extract and correct synchronous errors within specific frequency ranges, using a low-pass filter to suppress high-frequency vibrations and correct positional and speed deviations, thereby improving stability and reducing synchronous errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback tracking method is used to synchronize master and slave shafts, then synchronous error is suppressed, but vibrations are amplified making the system unstable
Solution Approach 1:
The patent segments the synchronous control into two independent control loops: master shaft control and slave shaft control. Each shaft is controlled independently with its own servo controller, avoiding the vibration amplification problem of feedback tracking while maintaining synchronization through command distribution with periodic correction
Solution Approach 2:
The patent introduces a synchronization error detector as an intermediary that periodically detects the synchronization state between master and slave shafts. This intermediary provides correction signals to adjust the slave shaft command, ensuring synchronization without continuous feedback tracking that causes vibration amplification
2Stability of the object's composition
If command distribution method is used to synchronize master and slave shafts, then system stability is maintained, but synchronous error increases
Solution Approach 1:
The patent applies preliminary action by periodically detecting synchronization errors and applying correction signals before large deviations occur. The synchronization error detector continuously monitors the phase difference between master and slave shafts and applies corrective adjustments to maintain synchronization accuracy
Solution Approach 2:
The patent implements feedback through the synchronization error detection mechanism that monitors the actual synchronization state and feeds correction signals back to the slave shaft controller. This feedback is applied periodically rather than continuously, maintaining stability while reducing synchronous error
3Ease of operation
If master shaft has low servo stiffness, then ease of operation is improved, but vibrations occur due to machining disturbances
Solution Approach 1:
The patent extracts the vibration suppression function from the master shaft control and applies it separately to the slave shaft control. By independently controlling the slave shaft and applying vibration suppression algorithms specifically to its command signals, the system reduces vibrations generated by machining disturbances without compromising master shaft operability
Solution Approach 2:
The patent changes control parameters dynamically by adjusting the slave shaft command based on detected synchronization errors and vibration characteristics. The servo controller modifies acceleration, deceleration, and position parameters in real-time to suppress vibrations while maintaining ease of operation
Data Source
AI summary
A servo controller includes: a first position feedback acquisition unit; a second position feedback acquisition unit; a converter converting the acquired position feedback of the first shaft to a value corresponding to the position feedback of the second shaft based on a synchronous ratio; a synchronous error calculator calculating synchronous error which is difference between the converted position feedback of the first shaft and the position feedback of the second shaft; a positional deviation calculator calculating a positional deviation of the second shaft which is difference between the position command for the second shaft and the position feedback of the second shaft; a filtering processor extracting components in a predetermined frequency range from the difference between the synchronous error and the positional deviation of the second shaft; and, a positional deviation corrector correcting the positional deviation of the second shaft by use of the output from the filtering processor.