Screwing Device Torque Measurement Correction
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Solution Overview
Problem
Servo-controlled screwing devices face challenges in accurately measuring tightening torque due to discrepancies between torque sensors integrated in the device and external sensors, leading to incorrect tightening reports and potential over-tightening, especially during high-speed final tightening phases.
Innovation Solution
The solution involves simultaneously measuring the torque with the conventional torque sensor and the acceleration or deceleration of the motor rotor, using the fundamental principle of dynamics to correct the output torque measurement, ensuring it aligns with the actual torque applied to the screw, thereby reducing inaccuracies and overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the motor rotor stops as quickly as possible when target tightening torque is reached, then the overshoot is minimized, but the motor rotor cannot stop immediately due to physical constraints
Solution Approach 1:
The controller predicts the rotor's stopping position by calculating its evolution during a predetermined time interval after torque threshold activation. This preliminary prediction allows the system to prepare for the inevitable overshoot by quantifying it in advance, rather than attempting impossible immediate stopping.
Solution Approach 2:
The system uses feedback from the torque sensor to detect when target tightening torque is reached, then combines this with rotor position prediction to calculate the expected overshoot. This feedback loop enables continuous monitoring and correction of tightening accuracy despite the physical constraint preventing immediate rotor stopping.
2Device complexity
If the torque sensor is integrated into the transmission of the screwing device, then the measurement system is compact and self-contained, but the measured torque differs from the actual tightening torque applied to the screw
Solution Approach 1:
The controller acts as an intermediary that receives the torque sensor signal and combines it with rotor position information to calculate the actual tightening torque. This intermediary processing step bridges the gap between the integrated sensor measurement and the true tightening torque applied to the screw, accounting for the differences introduced by integration into the transmission.
Solution Approach 2:
The system replaces direct mechanical torque measurement at the screw interface with an integrated sensor in the transmission, then uses computational methods (combining sensor data with rotor position) to derive the actual tightening torque. This substitution maintains compactness while recovering measurement accuracy through mathematical correction.
3Productivity
If the motor operates at high speed during final tightening phase, then productivity is improved, but the torque measurement discrepancies and overshoot increase
Solution Approach 1:
The system dynamically changes operational parameters by combining high-speed motor operation with real-time rotor position tracking and torque prediction calculations. This allows maintaining high productivity through high-speed operation while compensating for measurement discrepancies and overshoot through computational corrections based on varying operational parameters.
Solution Approach 2:
The system adopts a dynamic approach by continuously predicting rotor position evolution and torque development during the tightening process, rather than using static measurement methods. This dynamic calculation adapts to changing operational conditions at high speed, maintaining measurement accuracy despite the increased complexity of fast-moving components.
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 enhances the precision of tightening torque measurement, reduces overshoot, and improves the accuracy of tightening reports without the need for frequent recalibration, maintaining productivity while ensuring quality control.
Implementation Method 1
a deforming element provided with a strain gauge bridge. This deforming element is a metal component integrated into the structure of the screwing device
Implementation Method 2
a permanent magnet synchronous electric motor fitted with a sensor for measuring the angle of the rotor relative to the motor stator
Implementation Method 3
an epicyclic gear reduction to increase the electromagnetic torque produced by the motor and reduce its rotational speed proportionately
Data Source
Figure 1~2
Figure 3~4
Figure 5~5bis
AI summary
Optimized output torque measuring screwdriving device (201, 202), and method (6) for determining the corresponding output torque. The present invention relates to a screwdriving device comprising: - an electric motor (110, 11) comprising a stator (112) and a rotor (111); - a rotating output shaft (12); - a transmission (13) connecting said rotor (111) and said output shaft (12); - means for determining the output torque Coutie delivered by said output shaft (12), said means for determining the output torque Coutie comprising: - a torque sensor (18, 904, 905, 901, 90) comprising a deforming element (16) integrated into the screwdriving device, the axis of said deforming element (16) being parallel to the axis of said rotor (111); - means for measuring (18, 901, 90, 91) the acceleration or deceleration of said rotor (111);- calculation means (205) of said output torque Coutie from the torque Ccapteur measured by said sensor (18, 904, 905, 90I, 90) of torque and of the acceleration or deceleration of said rotor (111) measured by said measurement means (18, 90I, 90, 91) of the acceleration or deceleration of said rotor (111).;