Friction Stir Tool Current Regulation for Sensorless Plunging Control
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Solution Overview
Problem
Existing friction stir welding methods face challenges in accurately controlling the plunging depth of the tool due to discrepancies between the set and actual pressurizing forces, which can be attributed to factors like C-frame deflection and resistance, leading to inconsistencies in the welding process.
Innovation Solution
A method and device that regulate the drive electric current to the friction stir tool based on a pressurizing force change ratio, allowing the actual pressurizing force to match the set force without the need for additional sensors, thus ensuring precise control of the tool's plunging depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a loadcell is arranged at a position closer to the backup member to detect the actual pressurizing force, then the measurement precision of the pressurizing force is improved, but the device complexity and cost increase
Solution Approach 1:
The patent creates a virtual model (copy) of the pressurizing force characteristics by measuring at a convenient location and mathematically transforming the data. Instead of placing sensors at the difficult-to-access position near the backup member, the system measures force at the tool's drive source location and uses a pre-established mathematical model to calculate the equivalent force at the workpiece interface, thereby achieving accurate measurement without complex sensor arrangement
Solution Approach 2:
The patent introduces a mathematical model as an intermediary between the easily measurable force at the drive source and the difficult-to-measure force at the backup member. This intermediary transformation relationship allows the system to infer the actual pressurizing force characteristics without directly measuring them at the problematic location
2Manufacturing precision
If feedback control is executed based on loadcell detection values to eliminate the difference between set and actual pressurizing force, then the manufacturing precision of the plunging depth is improved, but the reliability decreases due to noise influence
Solution Approach 1:
The system creates a virtual representation of the pressurizing force through mathematical transformation of drive source measurements, avoiding the need for physical sensors at the workpiece interface. This virtual model eliminates the reliability issues associated with physical loadcells while maintaining the ability to execute feedback control for precise plunging depth management
Solution Approach 2:
The patent replaces the mechanical sensor-based measurement system (loadcell) with an electrical/control-based approach. By using the drive source's electrical signals and a mathematical model, the system substitutes the problematic mechanical sensing arrangement with a more reliable electrical measurement and calculation system
3Ease of operation
If the set pressurizing force is used without considering the pressurizing force change ratio, then the ease of operation is improved, but the manufacturing precision of the plunging depth deteriorates
Solution Approach 1:
The patent performs preliminary measurements and calculations to establish the pressurizing force change ratio before actual welding operations. By pre-characterizing the system's force transmission characteristics and storing this information in a lookup table, the system prepares the correction data in advance, allowing operators to simply select parameters without performing complex real-time calculations
Data Source
AI summary
A friction stir tool control method is a control method for controlling an operation of a friction stir tool by supplying a necessary drive electric current to a drive source of the tool. The control method includes obtaining a pressurizing force change ratio by comparing a set pressurizing force predefined as a pressurizing force at plunging of the tool into a workpiece with an actual pressurizing force occurring at actual plunging of the tool into the workpiece by supplying a drive electric current for generating the set pressurizing force to the drive source. The drive electric current is regulated in accordance with the pressurizing force change ratio so that the actual pressurizing force comes to the set pressurizing force, and the drive source is driven with the regulated drive electric current.