Adaptive Screw Joint Tightening Using Torque-Angle Change
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Solution Overview
Problem
Existing methods for tightening screw connections using motor-operated screwdrivers often require complex parameterization and are prone to errors due to varying screw connection geometries and materials, making it difficult to achieve the desired preload without overtightening or undertightening.
Innovation Solution
The method evaluates torque and angle of rotation parameters synchronously during tightening to determine changes in the screw connection's physical properties, using these real-time process parameters to set a shutdown criterion based on the torque increase over angle of rotation, allowing for precise control to reach the desired preload without specifying fixed thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If torque-controlled tightening or angle-of-rotation controlled tightening is used, then the desired preload can be achieved, but complex parameterization is required and errors occur due to varying screw connection geometries and materials
Solution Approach 1:
The screwdriver unit automatically determines the shutdown criterion by evaluating torque and angle of rotation parameters during the tightening process itself. The system uses the actual process data to adaptively set the shutdown criterion without requiring external parameterization or pre-programming of torque/angle thresholds, making the system self-configuring and error-resistant
Solution Approach 2:
The system dynamically changes the control parameter from fixed pre-set torque or angle thresholds to an adaptive shutdown criterion determined by the rate of change of torque with respect to angle of rotation. This parameter transformation allows the system to automatically adapt to different screw connection geometries and materials without complex parameterization
2Ease of operation
If fixed torque or angle of rotation thresholds are specified, then the tightening process is simple to control, but errors occur due to incorrect parameter specification for different screw connection types
Solution Approach 1:
The system continuously monitors torque and angle of rotation during tightening and uses this real-time feedback to dynamically determine the shutdown criterion. The shutdown criterion is calculated based on the actual rate of change of torque with respect to angle of rotation observed during the process, allowing automatic adaptation to different screw connection types without requiring operator knowledge of appropriate parameters
Solution Approach 2:
The control system transitions from static fixed thresholds to a dynamic shutdown criterion that adapts during the tightening process. The system evaluates the actual torque-angle relationship in real-time and adjusts the shutdown point accordingly, making the control both simple to operate and reliable across different screw connection geometries and materials
3Ease of manufacture
If parameterizable calculation models are used to determine torque and angle of rotation values, then threshold setting is simplified, but the models are complex to prepare and susceptible to errors from incorrect parameter inputs
Solution Approach 1:
The system eliminates the need for external parameterizable calculation models by determining the shutdown criterion directly from actual process data during tightening. The screwdriver unit itself performs the evaluation and adaptation, requiring no pre-programmed models or parameter databases, thus simplifying the system while maintaining ease of use
Solution Approach 2:
The invention extracts the essential control function from complex external calculation models and implements it directly within the screwdriver unit using real-time process parameter evaluation. This removes the dependency on complex external models and their associated parameterization requirements, keeping only the essential adaptive control logic
Data Source
AI summary
A method and apparatus for tightening a screw connection having a motor-operated screwdriver unit, wherein the angle of rotation and the torque are determined during the tightening to be able to stop the tightening process on reaching a desired tightening tension. An increase in the torque over the angle of rotation is determined by a determination device in a first tightening region and a change in the increase in the torque over the angle of rotation is determined in a second, following tightening region, with the screwdriver unit being stopped by a control device on reaching or exceeding of a maximum permitted change in the increase and/or of a change speed that is determined with reference to the increase that occurred in the first tightening region.