Servo Weld Gun Orientation Normalization via Torque Feedback
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Solution Overview
Problem
Existing welding robot systems with spot welding guns face challenges in correcting the orientation of the servo gun to ensure proper alignment with the part being welded, leading to uneven force distribution and poor weld quality due to orientation errors, which are difficult and time-consuming to correct, especially when one electrode is not visible.
Innovation Solution
A method that automatically determines a normal vector relative to the surface of the part to be welded, allowing for correction of the servo gun orientation prior to welding, using disturbance torque feedback from the motor controlling the movable electrode to detect multiple points in three-dimensional space and adjust the gun's orientation accordingly, without the need for external sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual teach correction is used to correct welding robot orientation, then orientation accuracy can be improved, but correction time increases significantly
Solution Approach 1:
The welding robot system performs self-correction of orientation by automatically detecting the normal vector of the workpiece surface and adjusting its own gun orientation accordingly, eliminating the need for manual teach correction operations
Solution Approach 2:
The system uses feedback from surface normal detection to automatically adjust the welding gun orientation, creating a closed-loop control system that corrects orientation errors without manual intervention
2Productivity
If automatic teach correction methods are used, then correction speed is improved, but orientation detection capability is insufficient
Solution Approach 1:
The patent replaces external sensor-based detection systems with a method that uses the welding robot's own motor disturbance torque feedback to detect surface normal orientation, eliminating the need for separate external sensing hardware
Solution Approach 2:
The welding robot system performs multiple functions using the same hardware: it uses its drive motors both for welding gun actuation and for surface normal detection through disturbance torque measurement, eliminating the need for dedicated detection sensors
3Measurement precision
If external sensors are added to detect surface normal, then orientation detection accuracy is improved, but system complexity increases
Solution Approach 1:
The welding robot uses its own drive system components (motors and controllers) to perform both welding operations and surface normal detection, eliminating the need for external sensors and reducing overall system complexity
Solution Approach 2:
The existing motor and controller components serve dual purposes: welding gun actuation and surface normal detection through disturbance torque measurement, reducing the need for additional hardware and simplifying the system
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 method enables accurate and efficient correction of the servo gun's orientation, preventing uneven force distribution and improving weld quality by ensuring the gun is properly aligned, thereby enhancing the reliability and efficiency of the welding process.
Implementation Method 1
The method may further employ disturbance torque feedback from at least one motor controlling the servo weld gun's moveable electrode to detect part locations at multiple points in three dimensional space
Data Source
AI summary
A method for controlling a welding robot having a servo gun with a movable tip and a fixed tip includes the steps of separately contacting a surface of a part with the movable tip to measure a base test point and an at least two additional test points displaced from the base test point. Two non-collinear vectors are calculated from the at least two additional test points. A normal vector is calculated from the two non-collinear vectors. An angle between the original servo gun orientation and the normal vector is determined. An orientation of the servo gun may be corrected, for example, if the angle is within user specified tolerances.