Tool Drive Controller for Real-Time Deflection and Vibration Compensation
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Solution Overview
Problem
In robotic machining, inaccuracies in locating the tool center point or workpieces can lead to manufacturing quality issues and reduced tool service life due to deflections and vibrations, especially in large aerospace structures during machining operations.
Innovation Solution
A controller for a tool drive that collects force and displacement data to generate stiffness models of workpieces, allowing for real-time compensation of deflections and vibrations, and determines the location of the tool drive relative to a fixed coordinate system, thereby improving machining precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional robotic machining systems are used without real-time deflection compensation, then the system structure remains simple and operation is straightforward, but manufacturing precision deteriorates due to workpiece deflections and vibrations
Solution Approach 1:
The tool drive system uses its own force sensors and control unit to measure deflections and vibrations during machining, and automatically compensates for these effects by adjusting its motion commands. The system serves itself by utilizing its inherent sensing capabilities rather than requiring separate external measurement systems, thereby improving precision without proportionally increasing overall system complexity
Solution Approach 2:
The control unit continuously monitors force data from the force sensors during machining operations and uses this feedback information to calculate and compensate for workpiece deflections and tool vibrations in real-time, adjusting the robotic manipulator's motion to maintain machining accuracy despite dynamic disturbances
2Manufacturing precision
If accurate tool center point and workpiece location calibration are performed, then manufacturing precision improves, but the time required for setup and calibration increases
Solution Approach 1:
The system performs initial calibration of the tool center point and workpiece location using traditional methods to establish a baseline coordinate system. This preliminary calibration provides sufficient accuracy for most operations, and the real-time force-based compensation then handles dynamic precision requirements, reducing the need for extensive recalibration
Solution Approach 2:
The system transitions from static calibration parameters to dynamic parameter adjustment by using real-time force measurements to calculate and apply compensation values for deflections and vibrations. This allows the system to adapt to changing machining conditions without requiring repeated full calibrations, thereby reducing calibration time while maintaining precision
3Manufacturing precision
If force sensors and real-time compensation systems are implemented, then machining accuracy improves by compensating for deflections and vibrations, but device complexity increases due to additional sensors and control mechanisms
Solution Approach 1:
The force sensors integrated into the tool drive serve multiple functions: they measure cutting forces for process monitoring, detect workpiece deflections for compensation, and identify vibration patterns for stability control. By making the sensing system multi-functional, the patent avoids adding separate dedicated sensors for each measurement task, thereby improving precision without proportionally increasing system complexity
Solution Approach 2:
The patent combines the force measurement capability with the existing motion control system by integrating the force sensors and compensation algorithms into the tool drive's control unit. This merging of sensing and control functions eliminates the need for separate standalone compensation hardware, achieving deflection compensation while minimizing the increase in overall device complexity
Data Source
AI summary
A controller for a tool drive that collects force data and displacement data from the tool drive. The controller generates a stiffness model representing a workpiece using the force data and the displacement data. The controller further collects a force signal from the tool drive. The controller determines deflection of the workpiece using the force signal and stiffness model. The controller determines a resonant frequency of the workpiece using the stiffness model. The controller modifies an oscillation frequency and/or a rotational frequency of a spindle of the tool drive based on the resonant frequency. The controller also determines a location of a tip of the tool drive using the force signal.