NC Machine Tool Control for Real-Time Cutting Dynamics Identification
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Solution Overview
Problem
Existing numerical control systems for machine tools cannot accurately identify cutting processes and mechanical dynamics during machining, particularly due to changes in dynamic rigidity caused by heat generation and workpiece mass reduction during the cutting process.
Innovation Solution
A numerical control system that includes a coordinate transformation unit to convert disturbance forces into a tool reference coordinate system and an identification unit to calculate cutting process parameters and dynamic characteristic parameters using disturbance forces, states of machine drive systems, and predetermined equation models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If only cutting process information is calculated using dynamic characteristic information stored in advance, then the calculation method is simple, but displacement cannot be calculated correctly when dynamic rigidity changes during machining
Solution Approach 1:
The system transitions from static pre-stored dynamic characteristic information to dynamic real-time identification. The identification unit continuously updates cutting process parameters and dynamic characteristic parameters during machining based on actual disturbance forces, allowing the system to adapt to changing dynamic rigidity conditions while maintaining calculation feasibility through iterative parameter identification.
Solution Approach 2:
The system implements feedback by using measured disturbance forces from force sensors during actual machining to correct and update the cutting process parameters and dynamic characteristic parameters. This closed-loop approach allows the system to compensate for changes in dynamic rigidity caused by heat generation and workpiece mass reduction, improving displacement calculation accuracy while maintaining a relatively simple calculation framework.
2Measurement precision
If in-process machining state analysis is performed to accurately identify cutting process and mechanical dynamics, then identification accuracy is improved, but system complexity increases
Solution Approach 1:
The numerical control system integrates multiple functions into a unified framework: the identification unit simultaneously identifies both cutting process parameters and dynamic characteristic parameters, the coordinate transformation unit handles multiple disturbance force measurements, and the system performs real-time simulation and parameter correction. This multi-functionality achieves accurate in-process identification without proportionally increasing system complexity.
Solution Approach 2:
The system introduces a force sensor as an intermediary measurement device to directly capture disturbance forces during machining. This intermediary provides accurate real-time data on cutting forces and mechanical dynamics, enabling precise identification without requiring complex indirect measurement systems or multiple specialized sensors.
3Reliability
If dynamic characteristic parameters are updated in real-time during machining, then identification accuracy is maintained despite rigidity changes, but computational load increases
Solution Approach 1:
The system updates only the necessary cutting process parameters and dynamic characteristic parameters that are directly affected by changing conditions (heat generation, workpiece mass reduction) rather than recalculating all system parameters. This selective parameter identification maintains reliability under changing conditions while minimizing unnecessary computational energy consumption.
Solution Approach 2:
The system focuses on identifying and updating specific dynamic characteristic parameters (such as rigidity parameters) and cutting process parameters that change during machining, rather than maintaining a complete static model. This targeted parameter change approach ensures identification accuracy is maintained despite rigidity changes, while computational load is reduced by only processing the parameters that actually change.
Data Source
AI summary
A numerical control system according to the present invention controls machine drive systems included in a machine tool that performs machining using a tool, according to a numerical control program, and includes a coordinate transformation unit that acquires a disturbance force or a disturbance torque applied to each machine drive system, and coordinate-transforms the disturbance force or the disturbance torque into a tool reference coordinate system for output, and an identification unit that calculates cutting process parameters that determine characteristics of a cutting process model and dynamic characteristic parameters that determine characteristics of a dynamics model of the machine tool, using the disturbance force or the disturbance torque output from the coordinate transformation unit, states of the machine drive systems, predetermined equation models, and cutting conditions. The equation models define relationships between the cutting process parameters, the dynamic characteristic parameters, and the disturbance force or the disturbance torque.