Servo Control Apparatus Reducing Tracking Error During Direction Reversal
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Solution Overview
Problem
Existing servo control systems face challenges in reducing tracking errors between the machine end position and the command position, especially during direction reversals, due to friction, backlash, and lost motion, which result in inaccuracies and flaws in machining results.
Innovation Solution
A servo control apparatus that calculates a torque command using error correction amounts based on the maximum change in deviation between the machine end and motor end positions during direction reversals, incorporating a model-response calculating unit, motor-end-movement-amount-during-stopping measuring unit, and error-correction-amount calculating unit to adjust the torque command and reduce tracking errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If torque compensation is performed based on the difference between virtual feeding mechanism and actual feeding mechanism, then frictional force and frictional torque can be compensated, but the correction comes into effect late and the tracking error is not sufficiently reduced
Solution Approach 1:
The invention calculates the motor end movement amount during stopping in advance, before the direction reversal occurs. This preliminary calculation allows the error correction amount to be prepared ahead of time, so that when the direction reversal happens and tracking error occurs, the correction can be applied immediately rather than after the error is detected, thus resolving the timing delay problem
2Manufacturing precision
If friction compensation signal is generated on the basis of direction reversal of position command, then friction compensation can be provided, but the shift of position between motor end and machine end affects full-closed control and compensation effect is not sufficiently obtained
Solution Approach 1:
The invention introduces the motor end movement amount during stopping as an intermediary parameter. This intermediary measurement captures the actual mechanical behavior during direction reversal, serving as a bridge between the position command and the full-closed control feedback. By using this intermediary data to calculate the error correction amount, the system can compensate for position shifts more accurately without being affected by the limitations of standard position feedback
3Manufacturing precision
If error correction is applied during direction reversal, then tracking error can be reduced, but excessive correction may occur causing new tracking errors
Solution Approach 1:
The invention applies partial correction by calculating the error correction amount as a specific portion of the total possible correction. Rather than applying full correction based on maximum deviation, the system uses the measured motor end movement amount during stopping to determine an appropriate correction magnitude, applying only the necessary partial correction to reduce tracking error without causing excessive correction and new errors
Data Source
AI summary
A servo control apparatus includes: a model-response calculating unit; a motor-end-movement-amount-during-stopping measuring unit that measures a motor end movement amount during stopping, which is a displacement amount of a detection value of a motor end position in a period from when the calculated value of the machine end position changes to zero until the calculated value changes to a value other than zero; and an error-correction-amount calculating unit that calculates an error correction amount on the basis of a parameter in which a maximum change amount of a deviation between the machine end position and the motor end position during moving direction reversal is set in advance, the calculated value of the machine end position, and the motor end movement amount. The servo control unit sets the detection value of the machine end position and the detection value of the motor end position.