Adaptive Screwdriver Speed Control for Torque Overshoot Prevention

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Solution Overview

Problem

Screwing tools in industrial settings often experience torque overshooting due to motor response time, leading to potential damage and inefficiencies, requiring manual speed selection and inflexible tightening programs that do not adapt to varying assembly characteristics.

Innovation Solution

A method for automatically adapting screwing speed based on torque variations, using coefficients K1 and K2 to gradually reduce speed and maintain target torque, independent of user input and adaptable to different assemblies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the screwing speed is increased to improve productivity, then productivity is improved, but torque overshooting occurs leading to potential damage and reduced reliability

Engineering Contradiction:

Improvescrewing speedVSAvoidtorque control accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies dynamics by making the screwing speed variable rather than constant. The control system continuously adjusts the motor speed based on real-time torque feedback, transitioning from a static speed setting to a dynamic speed profile that adapts to the actual tightening conditions, thereby preventing torque overshoot while maintaining high productivity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements feedback control by using torque sensors to monitor the actual tightening torque and feeding this information back to the control system. The control system then adjusts the motor speed based on the difference between the target torque and actual torque, ensuring accurate torque control even at high screwing speeds and preventing damage from overshooting

Inventive Principle:

Principle #23Feedback

2Ease of operation

If a fixed tightening program is used to simplify operation, then ease of operation is improved, but adaptability to different assembly characteristics deteriorates

Engineering Contradiction:

Improveprogram setup simplicityVSAvoidadaptation to assembly variations

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent applies self-service by enabling the control system to automatically adjust screwing parameters without requiring manual reprogramming for different assemblies. The system autonomously monitors torque feedback and adapts the speed profile in real-time, eliminating the need for operators to manually configure programs for each assembly type while maintaining both ease of operation and adaptability

Inventive Principle:

Principle #25Self-service

Data Source

PatentEP2241404B1Method for automatically adjusting the screwing speed of a screwdriver in several successive steps and corresponding tool

Publication Date: 2018.11.14 ETABLISSEMENT GEORGES RENAULT SAS

Figure 1

AI summary

The method involves executing two successive stages (1, 2) such that a set point speed is maintained constant for each stage and adjusted from one stage to following stage. The speed is calculated such that the speed is equal to a product of constant coefficient (K1) for a range of torque variations based on time and a constant coefficient (K2) for a range of percentages of final torque. Each stage predefined by lower and upper terminals is expressed in the form of percentage of final torque, where passage of the stage to the following stage modifies a value of the constant coefficient. An independent claim is also included for a screwing tool comprising a locking torque measurement unit.