Robot Rivet Tool Pose Compensation for Elastic Deformation
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Solution Overview
Problem
Self-piercing riveting processes face challenges due to high process forces causing elastic deformations in rivet setting tools, which impair the riveting result and require tools to be both lightweight and have long legs, making precise positioning difficult for robots.
Innovation Solution
A method and system where a robot adjusts the pose of the self-piercing rivet setting tool during riveting to compensate for elastic deformations, using a deformation model to predict and correct bending and displacement, allowing for more precise and reliable riveting with lighter tools and longer legs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If self-piercing-rivet setting tools are made lightweight with long legs to reduce robot load and enable riveting far from edges, then ease of operation and adaptability improve, but elastic deformation under high process forces worsens, impairing riveting precision
Solution Approach 1:
The robot performs preliminary positioning adjustments before riveting based on predicted deformation values. The control unit calculates expected elastic deformation of the tool legs and pre-compensates by adjusting the tool pose, so that when high process forces are applied during riveting, the tool ends up in the correct final position despite the deformation.
Solution Approach 2:
The system uses a deformation model that predicts tool deformation based on process parameters. This feedback mechanism allows the control unit to continuously adjust the robot's positioning commands to compensate for elastic deformation, maintaining riveting precision even with lightweight tools having long legs.
2Strength
If high process forces are applied during self-piercing riveting to join workpieces, then joining strength improves, but elastic deformation of the setting tool worsens, causing positioning errors
Solution Approach 1:
Before applying high process forces during riveting, the control unit calculates the expected elastic deformation using a deformation model and commands the robot to adjust the tool pose in advance. This preliminary positioning ensures that when the high forces are applied, the tool maintains accurate positioning throughout the riveting process.
Solution Approach 2:
The system applies a preliminary counteracting action by adjusting the tool pose in the opposite direction of expected deformation. The control unit commands the robot to position the tool with pre-compensated coordinates that account for the upcoming elastic deformation caused by high process forces, thereby preventing positioning errors.
3Adaptability or versatility
If the die-side leg of the setting tool is made longer to reach riveting positions far from component edges, then adaptability improves, but elastic deformation under load worsens, affecting riveting quality
Solution Approach 1:
The deformation model predicts elastic deformation of the long die-side leg based on process parameters. The control unit uses this prediction to command preliminary positioning adjustments that compensate for the expected deformation, ensuring reliable riveting quality even when using long legs to reach positions far from component edges.
Solution Approach 2:
The system dynamically changes the tool pose parameters during riveting based on real-time deformation predictions. The control unit adjusts positioning coordinates to account for elastic deformation of the long leg, maintaining riveting quality while enabling operation at extended reach positions.
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
This approach improves the precision and reliability of self-piercing riveting by partially compensating for tool deformations, enhancing the riveting process and reducing the calibration effort, while protecting the tools and workpieces.
Implementation Method 1
High process forces often have to be applied during self-piercing riveting, often in the region of, in some cases, well over 20 kN. This can lead to elastic deformations even with solid self-piercing-rivet setting tools
Data Source
AI summary
A method for positioning a self-piercing-rivet setting tool using a robot includes commanding a robot to position a self-piercing-rivet setting tool in a riveting pose at at least two workpieces joined, and commanding the tool to set a rivet to join the workpieces. During self-piercing riveting, the robot is commanded to change the pose of the tool to at least partially compensate for an elastic deformation induced by the self-piercing rivet. The method may additionally or alternatively include commanding the robot to position the tool in a riveting pose, commanding a self-piercing-rivet movement of the tool with or without setting of a rivet, and manually or sensor-based detecting a change in pose of a die of the tool or of a test element as a result of the self-piercing-rivet movement. The self-piercing-rivet setting tool may be checked and/or a deformation model may be calibrated based on the detected change in pose.