Robotic Fastener Insertion Using Force-Moment Engagement Detection
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Solution Overview
Problem
Existing robotic assembly methods struggle to accurately determine engagement between male and female parts with fastener structures due to manufacturing variations and shape inconsistencies, leading to potential damage or assembly failures.
Innovation Solution
A robot system equipped with a force sensor and controller that monitors force and moment changes during insertion to determine engagement and orientation, using thresholds and recovery operations to ensure proper assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the pressing reaction force is monitored to determine engagement, then automation is achieved, but manufacturing variations cause false negatives where engagement is not detected
Solution Approach 1:
The patent introduces a moment sensor as an intermediary measurement device to detect engagement. Instead of relying solely on the pressing reaction force (which fails due to manufacturing variations), the moment sensor measures the rotational moment generated when the engagement portion contacts the receiving portion, providing a more reliable detection mechanism that works consistently across production tolerances.
Solution Approach 2:
The patent replaces the traditional mechanical pressing force measurement system with a moment-based detection system. By substituting the direct force monitoring approach with moment sensor measurement, the system achieves more reliable engagement detection that is insensitive to manufacturing variations in clearance and geometry.
2Reliability
If the male part is pressed into the female part to ensure engagement, then assembly completeness is achieved, but part damage occurs due to excessive pressing
Solution Approach 1:
The patent implements a feedback control mechanism where the moment sensor continuously monitors the engagement state during insertion. When the moment value indicates that engagement has been achieved, the system automatically stops the insertion motion, preventing excessive pressing that would cause part damage. This real-time feedback loop ensures both complete assembly and part protection.
Solution Approach 2:
The system performs preliminary detection of the engagement state using the moment sensor before completing the full insertion. By detecting engagement early through moment measurement, the system can stop the insertion process in advance, preventing the harmful effect of excessive pressing that would occur if insertion continued until mechanical end-stop or damage.
3Productivity
If the robot inserts the workpiece at high speed to improve productivity, then production efficiency increases, but accurate detection of engagement becomes difficult
Solution Approach 1:
The patent replaces the pressing force measurement system with a moment-based detection system that is more suitable for high-speed operation. The moment sensor can detect engagement instantaneously based on rotational moment changes, providing faster and more accurate detection compared to force measurement, thereby enabling high-speed assembly without sacrificing detection accuracy.
Solution Approach 2:
The patent utilizes the dynamic moment signal generated during high-speed insertion to detect engagement. By monitoring the moment waveform characteristics during rapid insertion, the system can identify engagement events accurately even at high speeds, maintaining measurement precision while achieving high productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Automates the assembly process with high accuracy, preventing part damage and improving success rates by accurately detecting engagement and correcting insertion orientation.
Implementation Method 1
a force sensor located on the robot to measure a force and a moment acting on the workpiece
Data Source
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AI summary
A technique automates robotic assembly of two parts with a fastener structure including an engaging portion and a receiving portion. A robot system includes a robot that grips a workpiece, a force sensor located on the robot to measure a force and a moment acting on the workpiece, and a controller that controls the robot. The controller monitors, while moving the workpiece in a direction along a first axis and inserting the workpiece into a part, a change in a force F in the direction along the first axis and a change in a moment M about a second axis perpendicular to the first axis measured by the force sensor to determine a state of assembly of the workpiece with the part.