Track Control Apparatus for Multi-Axis Servo Error Correction
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Solution Overview
Problem
Conventional track control methods fail to accurately correct track errors, especially when acceleration and deceleration occur, leading to shape distortions and excessive load on the driving system, particularly when machining complex three-dimensional shapes or small line segments.
Innovation Solution
A track control apparatus that simultaneously controls multiple axes, using an interpolation/acceleration unit to calculate post-acceleration and deceleration routes, a servo-response calculating unit to determine tangential direction movements, and a position-vector correcting unit to generate a correction vector, which is applied to correct position commands for each axis, ensuring accurate tracking and minimizing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional track control methods are used to calculate error amounts based on commanded points before acceleration and deceleration, then the control system is simple to implement, but the calculated error amount differs from the actual error amount during transient states, causing shape distortion in the response track
Solution Approach 1:
The patent performs acceleration and deceleration calculations on the commanded route before generating position commands for each axis. By pre-calculating the corrected route that accounts for transient state errors during acceleration and deceleration, the system determines accurate error amounts in advance, ensuring shape accuracy without requiring complex real-time adjustments during motion transitions.
Solution Approach 2:
The patent introduces an intermediary correction process that calculates the difference between the commanded route and the actual servo response track. This intermediary calculation identifies error amounts caused by acceleration and deceleration effects, allowing the system to compensate for these errors by adjusting the commanded positions before they are executed, thereby maintaining track accuracy.
2Speed
If feed speed is suddenly changed near start point, end point, or where commanded feed speed changes, then the response is fast, but allowable acceleration of the control target machine is exceeded, causing excessive load on the driving system
Solution Approach 1:
The patent dynamically adjusts the commanded feed speed profile by performing acceleration and deceleration calculations on the commanded route. The system modifies the speed transitions to ensure they remain within the allowable acceleration limits of the machine, creating a dynamically optimized speed profile that maintains fast response while protecting the driving system from excessive loads.
3Manufacturing precision
If correction vectors are applied to correct commanded positions for suppressing track errors, then track accuracy is improved, but the control system requires complex calculations involving servo response estimation and error decomposition
Solution Approach 1:
The patent implements a feedback mechanism where the actual servo response of each axis is measured and compared with the commanded position. The difference between the commanded route and the actual response track is calculated to determine error amounts, which are then used to generate correction vectors. These correction vectors are applied to adjust the commanded positions, creating a closed-loop control system that continuously suppresses track errors.
4Reliability
If acceleration and deceleration are performed to gradually increase or reduce feed speed, then the driving system is protected from excessive load, but the machining time increases and productivity decreases
Solution Approach 1:
The patent optimizes the acceleration and deceleration parameters by calculating the corrected route based on the machine's allowable acceleration characteristics. The system determines optimal acceleration and deceleration rates that maximize machining speed while remaining within the driving system's capacity limits, thereby protecting the system from excessive load without unnecessarily extending machining time.
Data Source
AI summary
A track control apparatus includes an interpolation/acceleration and deceleration calculating unit that interpolates a commanded route and calculates a post-acceleration and deceleration interpolation route, an axis distributing unit that generates a position command for each movable axis from the post-acceleration and deceleration interpolation route, a servo-response calculating unit that calculates a servo response to the position command, a tangential-direction-servo-response calculating unit that obtains a tangential direction servo response from the post-acceleration and deceleration interpolation route, a reference-point generating unit that obtains a reference point from the tangential direction servo response, a position-vector correcting unit that corrects the position command for each movable axis to output a post-correction position command for each movable axis, and a servo control unit that outputs motor driving torque such that each movable axis follows the corresponding post-correction position command.