Servomotor Spot Welding Pressing Force Control
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Solution Overview
Problem
Conventional spot welding systems using servomotor-driven electrodes struggle to accurately control the pressing force due to variations in electrode orientation, material properties, and environmental factors, leading to inconsistent welding quality and efficiency.
Innovation Solution
A spot welding system equipped with a pressing force detector and a control unit that calculates and adjusts the servomotor driving current in real-time to maintain the desired pressing force, utilizing a PID compensator and feedforward control to stabilize the clamping force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a correlation function between servomotor driving current and electrode pressing force is preliminarily prepared, then the clamping-pressing force can be regulated, but the pressing force actually produced may not reach the specified value due to variations in pressing direction, material properties, and environmental factors
Solution Approach 1:
The patent implements a feedback control system where the actual pressing force is continuously measured by a force sensor and compared with the target pressing force. The servomotor's driving current is then adjusted based on the difference between actual and target values, enabling dynamic compensation for variations in pressing direction, material properties, and environmental factors that a static correlation function cannot account for.
Solution Approach 2:
The system dynamically changes the servomotor driving current parameter based on real-time feedback from the force sensor. Instead of relying on a fixed correlation function, the control unit continuously adjusts the driving current to maintain the desired pressing force, adapting to different pressing directions and material properties through parameter modification rather than relying on pre-determined relationships.
2Device complexity
If the pressing force is regulated based on the position of the electrode driving servomotor, then the control can be simplified, but the generation state of the pressing force varies significantly depending on material and equipment state, making it extremely difficult to stabilize the pressing force
Solution Approach 1:
The patent replaces position-based open loop control with force-based closed loop feedback control. A force sensor directly measures the pressing force applied to the workpiece, and this measurement is fed back to the control unit which adjusts the servomotor driving current accordingly. This feedback mechanism directly addresses the pressing force stability issue by continuously monitoring and correcting deviations from the target force.
Solution Approach 2:
The patent substitutes mechanical position-based control with sensor-based force measurement and electronic feedback control. Instead of relying on the servomotor position to infer pressing force, the system uses a force sensor to directly measure the actual pressing force and electronically adjusts the driving current to maintain stability, replacing mechanical inference with direct sensing and electronic control.
3Adaptability or versatility
If updating the correlation function at every given time period is implemented, then some adaptation can be achieved, but it is not known whether or not the specified pressing force is attained at the actual welding position, and the clamping-pressing force cannot be accurately controlled
Solution Approach 1:
The patent implements continuous real-time feedback control where the force sensor measures the actual pressing force at the welding position and the control unit immediately adjusts the servomotor driving current based on this measurement. This eliminates the problem of not knowing whether the specified pressing force is attained, as the feedback loop continuously verifies and corrects the pressing force at the actual welding position rather than relying on periodic updates.
Solution Approach 2:
The system performs self-adjustment through the feedback loop, where the control unit automatically modifies the driving current based on the force sensor measurement without requiring external intervention or periodic manual updates. The system serves itself by continuously monitoring its own performance and making real-time corrections to maintain accurate pressing force control.
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 ensures accurate and consistent pressing force application, enhancing welding quality and efficiency by continuously monitoring and regulating the pressing force, thereby reducing the impact of disturbances and equipment aging.
Implementation Method 1
a pressing force detector (3) which detects the pressing force applied to the work (12)
Implementation Method 2
a servomotor (2) for driving the welding electrodes (1a)
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A spot welding system and method where pressing force of a welding electrode applied by driving a servomotor is accurately controlled. The spot welding system has a pair of welding electrodes, a servomotor (2) for driving the welding electrodes and clamping and pressing an article (12) to be welded, and a controller (100) for controlling the welding electrodes and operation of the servomotor. A pressing force detector (3) is provided in order to measure pressing force actually applied to the article (12) to be welded. The controller (100) regulates a driving current to the servo motor (2) based on the measurement value of the pressing force detector (3), controlling the pressing force applied to the article (12).