Robotic Screwdriver Motion Control for Zero Axial Force Assembly
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Solution Overview
Problem
Conventional screw tightening devices for robotic arms risk damaging ultra-compact and lightweight products due to misalignment or over-tightening, as they apply force along the screw's axis, which can be detrimental to delicate materials like aluminum and plastic.
Innovation Solution
A screwdriver attachment for robotic arms that maintains a constant pre-defined distance from the screw, allowing for zero axial force application during installation, with a system comprising a tool rotation apparatus and a tool linear movement apparatus, controlled by servo motors and a processor to manage screwing speed and torque, enabling precise screw placement without damaging the product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional screw tightening devices apply force along the screw axis to ensure proper installation, then screw installation reliability is improved, but the risk of damaging delicate products increases
Solution Approach 1:
The patent replaces the conventional feedback mechanism that applies axial force with a cooperative motion control system between linear and rotational apparatuses. The linear movement apparatus moves the tool tip precisely along the screw axis while the rotational apparatus rotates the screw, maintaining a constant pre-defined distance without applying damaging axial force, thus substituting mechanical force application with coordinated motion control.
Solution Approach 2:
The patent changes the control parameter from axial force magnitude to the distance between tool tip and screw head. By controlling the linear movement to maintain a constant pre-defined distance (e.g., 0.5mm to 2mm gap), the system ensures proper screw installation through precise positional control rather than force application, adapting to delicate materials like aluminum and plastic.
2Manufacturing precision
If feedback mechanisms are used to detect force and control braking to prevent over-tightening, then screw installation precision is improved, but device complexity increases
Solution Approach 1:
The patent substitutes the complex feedback mechanism with brake control with a simpler cooperative motion control system. Instead of detecting axial force and controlling braking, the system uses the linear movement apparatus to maintain a constant pre-defined distance between tool tip and screw head, eliminating the need for force sensing and brake modulation while achieving comparable or superior precision.
Solution Approach 2:
The system achieves precise screw installation through the inherent coordination between linear and rotational movement. The linear apparatus automatically maintains the correct distance as the rotational apparatus drives the screw, with the constant distance relationship self-regulating the installation process without requiring external feedback or active control intervention.
3Productivity
If faster screwdriver head movement is implemented to increase production capacity, then productivity is improved, but accuracy in screw tightening deteriorates
Solution Approach 1:
The patent implements dynamic coordination between linear and rotational movement apparatuses. The linear movement apparatus dynamically adjusts the tool tip position to maintain constant distance while the rotational apparatus operates at high speed. This dynamic system allows rapid screw installation without sacrificing precision, as the linear positioning adapts in real-time to the rotational speed and screw advancement.
Solution Approach 2:
The system replaces speed-limited feedback control with proactive motion coordination. Instead of reacting to force feedback at high speeds, the linear movement apparatus proactively maintains the correct distance trajectory, enabling faster operation while preserving accuracy through predictive positional control rather than reactive force modulation.
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
Enables highly accurate and rapid screw installation with controlled force application, ensuring the safety and precision required for assembling delicate parts, while minimizing the risk of product damage.
Implementation Method 1
The tool linear movement motor may be connected to a lead screw that is parallel to the central axis, the lead screw having a known pitch, wherein the tool is linked to a nut, which may be a ball nut, mounted on the lead screw, such that rotation of the lead screw causes the tool to move along the central axis.
Data Source
AI summary
The invention relates to attachments for industrial robotic equipment and in particular relates to screw driver attachments for standalone or collaborative robots. A screwdriver apparatus for a robotic arm is provided, the apparatus being suitable for installing screws of a known pitch into a component, the apparatus comprising a screw driving tool having a shaft rotatable about a central axis, the shaft having a distal end with a tip suitable for engaging with a screw, the shaft further having a proximal end connected to both a tool rotation apparatus and a tool linear movement apparatus, wherein the tool rotation apparatus and the tool linear movement apparatus are arranged to cooperate such that the tool tip is maintained at a constant pre-defined distance in relation to the screw when in use.