Screw Fastening Slip Detection for Accurate Seating Point Control
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Solution Overview
Problem
Existing screw fastening methods face challenges in accurately determining the seating point of a screw member due to noise in torque measurements and the occurrence of slip, which affects axial tension accuracy and operational productivity.
Innovation Solution
A screw fastening apparatus and method that includes a rotational angle sensor, torque detector, torque value difference detector, slip detector, and control unit to determine the theoretical seating point and detect slip by calculating a moving average of torque value differences, allowing for precise control of screw fastening and discontinuation when slip is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque values are used to determine the seating point and calculate torque increase ratio, then the screw fastening process can be controlled, but noise in torque measurements and slip occurrence cause inaccurate theoretical seating point determination
Solution Approach 1:
The patent extracts and removes the harmful elements (noise and slip) from the torque measurement data by detecting slip events separately and excluding their influence when calculating the torque increase ratio, thereby improving the accuracy of theoretical seating point determination
Solution Approach 2:
The system continuously monitors torque values during the fastening process, provides feedback on the torque increase ratio, and uses this feedback to dynamically adjust and refine the determination of the theoretical seating point, ensuring accurate axial tension control
2Reliability
If the screw fastening operation is suspended when slip is detected, then axial tension accuracy is improved, but operational productivity decreases due to frequent interruptions
Solution Approach 1:
The patent performs preliminary detection of slip events and calculates the torque increase ratio excluding slip-influenced data before completing the fastening operation, thereby ensuring accurate axial tension without needing to suspend the operation
Solution Approach 2:
The system maintains continuous screw fastening operation by identifying and excluding only the specific rotational angle periods affected by slip, allowing the fastening process to continue uninterrupted while still achieving accurate axial tension control
3Manufacturing precision
If a predetermined rotational angle is applied from the theoretical seating point to achieve target axial tension, then fastening precision is improved, but the complexity of the fastening control system increases
Solution Approach 1:
The system automatically determines the theoretical seating point and calculates the required rotational angle based on target axial tension requirements, eliminating the need for manual calculation or complex external control systems
Solution Approach 2:
The patent changes the control parameter from torque-based to rotational angle-based control after determining the theoretical seating point, simplifying the control system while maintaining high precision axial tension control
Data Source
AI summary
A screw fastening apparatus for fastening a screw member having a bearing surface with respect to a member to be fastened by rotating the screw member from a theoretical seating point to a target rotational angle, including a rotational angle sensor which senses rotational angle values of the screw member for fastening the screw member, a torque detector which detects torque values for fastening the screw member, a torque value difference detector which detects a plurality of torque value differences, each of the torque value differences is a difference of the torque values detected at intervals of a constant rotational angle, a slip detector which detects a slip of the screw member with respect to the member to be fastened, from an average of the torque value differences, and a screw fastening discontinuing unit which instructs to discontinue the screw fastening when the slip is detected by the slip detector.