Numerical Controller for Parallel Link Machine Tool
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional numerical controllers for machine tools with parallel link mechanisms cannot realize machining in certain tool positions and postures due to crossover offsets, leading to unrealizable regions, and lack a specific control method to continue machining when commanded conditions are impossible to meet.
Innovation Solution
A numerical controller with a command analysis unit, correction command calculation unit, and command output unit that analyzes program commands, calculates and outputs a corrected posture to maintain the commanded position on the outer periphery of an unrealizable region, allowing machining to continue by adjusting the tool's axial direction without changing the distal end point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the machine tool uses a parallel link mechanism with crossover offset, then the structure is compact and positioning is precise, but there exists an unrealizable region where certain tool positions and postures cannot be achieved
Solution Approach 1:
The system dynamically changes the tool posture parameters by calculating a corrected posture that satisfies the parallel link mechanism's constraints. When the commanded posture falls within the unrealizable region, the correction command calculation unit computes an alternative posture configuration that achieves the same machining objective while respecting the mechanical limitations of the parallel link structure.
2Reliability
If the numerical controller issues an alarm when commanded position and posture are not feasible, then the system maintains strict control accuracy, but machining cannot continue in unrealizable regions
Solution Approach 1:
The system performs preliminary calculation of the corrected posture before executing the machining operation. The correction command calculation unit pre-computes the alternative posture configuration that satisfies the parallel link mechanism constraints, allowing the machining to proceed without interruption or alarm conditions.
Solution Approach 2:
The system implements a feedback mechanism where the command analysis unit continuously monitors whether the commanded position and posture combination is feasible. When infeasibility is detected, the correction command calculation unit generates corrected commands based on the parallel link mechanism's actual capabilities, and the command output unit outputs these corrected commands to maintain continuous machining operation.
3Length of moving object
If the extensible link axes are moved to position the tool distal end in the unrealizable region, then the tool can reach the target position, but the tool posture tilts and becomes incorrect
Solution Approach 1:
The system simultaneously adjusts both position and posture parameters to maintain the correct tool orientation. The correction command calculation unit computes the relationship between position and posture changes required to keep the tool distal end at the commanded position while correcting the axial direction to achieve the correct posture for machining.
Data Source
AI summary
A numerical controller for controlling a machine tool having a parallel link mechanism specifies a commanded position and a commanded posture of a tool by analyzing a program command, corrects the commanded posture while maintaining the commanded position when a combination of the specified commanded position and commanded posture is not feasible, and outputs the commanded position and the corrected posture which has been corrected to the machine tool. In this way, machining in the unrealizable region is realised by the machine tool having the parallel link mechanism.