Servo Gun Pressure Detection via Motor Current Analysis
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Solution Overview
Problem
Conventional robotic welding gun control methods face challenges due to high mechanical impedance and delayed pressure force transmission, leading to inaccurate responses and increased size and weight, and existing intelligent welding guns are not designed for defect detection and require multiple sensors.
Innovation Solution
A method and apparatus for detecting pressure changes in robotic welding systems by storing benchmark values and calculating current values for spring constant, pressure, efficiency, and inertia/friction, generating error indications for deviations, and performing tip wear measurements to ensure accurate pressure calibration and detect potential issues like arm fracture or motor deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a speed reducer is provided in the moving side portion of the welding gun, then the mechanical impedance is increased and dynamic hardness is improved, but the responsiveness is lowered and accurate pressure response becomes difficult to obtain
Solution Approach 1:
The patent replaces the mechanical encoder-based detection system with a motor current-based pressure detection system. By monitoring the current consumed by the servo motor during tip closure, the system can accurately detect pressure changes without relying on the mechanical impedance transmission path that includes the speed reducer. This substitution eliminates the responsiveness problem caused by the mechanical transmission delay.
2Strength
If the rigidity of the arm supporting the fixed side electrode tip is increased to match the mechanical impedance of the moving side portion, then the mechanical impedance is balanced, but the size and weight of the welding gun are increased
Solution Approach 1:
The patent eliminates the need for mechanical impedance balancing by substituting the pressure detection mechanism. Instead of requiring the fixed side arm to have high rigidity for accurate encoder detection, the system uses motor current monitoring to detect pressure, allowing the arm to be lighter while maintaining detection accuracy.
3Measurement precision
If multiple sensors are provided in the intelligent welding gun for pressure and position detection, then the measurement accuracy is improved, but the device complexity and cost are increased
Solution Approach 1:
The patent extracts the pressure detection function from the mechanical sensor system and implements it through electrical current monitoring. By taking out the pressure sensing capability from the mechanical domain and placing it in the electrical domain (motor current), the system achieves accurate pressure detection without adding mechanical sensors, thereby reducing device complexity.
Solution Approach 2:
The patent makes the motor current serve multiple functions: it simultaneously controls the motor operation and provides pressure detection information. This multi-functionality eliminates the need for separate pressure sensors, reducing system complexity while maintaining measurement precision.
4Device complexity
If the encoder is located on the opposite side of the moving side electrode tip with respect to the speed reducer, then the mechanical structure is simplified, but the transmission of pressing displacement and force to the encoder is delayed and reduced
Solution Approach 1:
The patent substitutes the mechanical displacement transmission path (through the speed reducer to the encoder) with an electrical signal path (motor current measurement). This substitution eliminates the time delay and signal attenuation caused by the mechanical transmission path while maintaining the simplified structural arrangement.
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
The solution enables accurate pressure calibration and defect detection in robotic welding systems, improving welding efficiency and reducing hardware errors by using a pressure estimator to compare measured deflection values with benchmark values, thus enhancing the reliability and precision of the welding process.
Implementation Method 1
A method for detecting pressure changes in robotic welding systems... measure a resulting first deflection value at the gun tips... measure a resulting second deflection value at the gun tips... converting the deflection value to a calibrated pressure value
Data Source
AI summary
A method and an apparatus detects pressure changes at servo gun tips of a robotic welding system having a servo gun with a movable tip and an opposed fixed tip configured to weld a part. The method and apparatus observe a tip deflection value and convert the value to a current pressure value using a pressure estimator. The current pressure value is compared to a benchmark pressure value to detect any difference.