Numerical Controller Rotation Axis Solution Selection
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Solution Overview
Problem
Existing numerical controllers for 5-axis machine tools face challenges in uniquely determining and moving to compensated positions of rotation axes due to multiple solution sets from trigonometric functions like arctangent, leading to potential overtravel alarms or machine breakage, as they often exceed the operable range or do not align with command positions.
Innovation Solution
A numerical controller with a solution selection mechanism that identifies the solution set closest to the tool direction in the command coordinate system for rotation axes, using error compensation calculations, and adjusts positions within the operable range to ensure alignment with command positions, employing trigonometric functions such as arctangent, arccosine, or arcsine, and rounds positions if they exceed the machine's operable range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If error compensation is performed using trigonometric functions like arctangent to determine rotation axis positions, then workpiece setting error compensation is achieved, but multiple solution sets are generated making it impossible to uniquely determine the compensated position
Solution Approach 1:
The patent changes the parameter selection by introducing a new criterion for selecting among multiple mathematical solutions: choosing the solution closest to the original command position. This parameter change (from any valid mathematical solution to the solution nearest the command position) resolves the non-uniqueness problem while maintaining compensation precision
Solution Approach 2:
The patent implements feedback by comparing the calculated compensated positions with the original command positions and selecting the solution that minimizes the deviation. This feedback mechanism ensures unique determination of the compensated position by continuously referencing the original command intent
2Measurement precision
If the compensated position is calculated based on error compensation, then workpiece setting error is corrected, but the compensated position may exceed the machine's operable range causing overtravel alarm or machine breakage
Solution Approach 1:
The patent applies preliminary anti-action by预先 checking whether the calculated compensated position falls within the operable range before executing the movement. If it exceeds the range, the system proactively adjusts the position to the boundary of the operable range, preventing overtravel alarms and machine breakage before they can occur
Solution Approach 2:
The patent provides beforehand cushioning by preparing alternative positions (boundary positions of the operable range) in advance. When the calculated compensated position exceeds the operable range, the system switches to the pre-prepared boundary position, cushioning against the potential harm of overtravel without disrupting the machining process
3Measurement precision
If the compensated position is different from the command position, then workpiece setting error is compensated, but it may be impossible to move to the compensated position depending on machine structure
Solution Approach 1:
The patent changes the position parameter by adjusting the compensated position to fall within the operable range when necessary. This parameter modification ensures that the position is both accurate (for compensation) and movable (for machine operation), resolving the contradiction between precision and ease of operation
Solution Approach 2:
The patent applies dynamics by making the compensated position adaptive rather than fixed. The system dynamically adjusts the compensated position based on the machine's operable range, selecting the optimal position that satisfies both compensation accuracy and machine movability requirements
Data Source
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AI summary
A numerical controller controlling a 5-axis machine tool compensates setting error that arises when a workpiece is set on the table. Error in the three linear axes and the two rotation axes are compensated using preset error amounts to keep the calculated tool position and tool direction in a command coordinate system. If a trigonometric function used for error compensation has a plurality of solution sets, the solution set closest to the tool direction in the command coordinate system is selected from the plurality of solution sets and used as the positions of the two rotation axes compensated in the above error compensation.